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Oncogene (2002) 21, 6884 – 6897
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Chromosome instability in human lung cancers: possible underlying
mechanisms and potential consequences in the pathogenesis
Akira Masuda1 and Takashi Takahashi*,1
1
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan
Chromosomal abnormality is one of the hallmarks of
neoplastic cells, and the persistent presence of chromosome instability (CIN) has been demonstrated in human
cancers, including lung cancer. Recent progress in
molecular and cellular biology as well as cytogenetics
has shed light on the underlying mechanisms and the
biological and clinical significance of chromosome
abnormalities and the CIN phenotype. Chromosome
abnormalities can be classified broadly into numerical
(i.e., aneuploidy) and structural alterations (e.g., deletion, translocation, homogenously staining region (HSR),
double minutes (DMs)). However, both alterations
usually occur in the same cells, suggesting some overlap
in their underlying mechanisms. Missegregation of
chromosomes may result from various causes, including
defects of mitotic spindle checkpoint, abnormal centrosome formation and failure of cytokinesis, while
structural alterations of chromosomes may be caused
especially by failure in the repair of DNA double-strand
breaks (DSBs) due to the impairment of DNA damage
checkpoints and/or DSB repair systems. Recent studies
also suggest that telomere erosion may be involved. The
consequential acquisition of the CIN phenotype would
give lung cancer cells an excellent opportunity to
efficiently alter their characteristics so as to be more
malignant and suitable to their microenvironment, thereby gaining a selective growth advantage.
Oncogene (2002) 21, 6884 – 6897. doi:10.1038.sj.onc.
1205566
Keywords: chromosome instability; cell cycle checkpoint; DNA double-strand break; telomere; lung
cancer
Introduction
High fidelity DNA replication and faithful chromosome segregation are fundamentally essential processes
allowing cells to transmit their genetic information to
the descendants. Failures in maintaining genetic
stability may cause their death or such abnormal
phenotypes as malignancy. Cancer cells frequently
exhibit marked chromosome abnormalities, which are
generally considered to reflect defects in the mechan-
*Correspondence: T Takahashi; E-mail: [email protected]
isms that ensure genetic stability. Chromosome
abnormalities can be classified broadly into numerical
(i.e., aneuploidy) and structural alterations (e.g.,
deletion, translocation, homogenously staining region
(HSR), double minutes (DMs)) of chromosomes. Such
chromosomal alterations, which are indeed present in
most human tumors, are especially marked in solid
tumors, including lung cancer, but the underlying
mechanisms and the biological and clinical significance
have not been elucidated to any satisfactory degree.
However, recent progress in molecular and cellular
biology as well as technical development in cytogenetics has shed light on these important issues related
to cancer development and progression, providing
evidence for the involvement of failures in the cell
cycle checkpoint control and defects in the DNA
double-strand break (DSB) repair system in the genesis
of chromosome instability (CIN).
In the present article, we will give a brief overview of
chromosomal alterations thus far reported in lung
cancer, and then summarize recent progress in the
understanding of possible underlying mechanisms of
CIN and its potential involvement in the development
of lung cancer, with reference to recent findings in the
analysis of other human cancers as well as in those of
various organisms such as mice and yeast.
Numerical and structural chromosome abnormalities in
human lung cancer
Early in the 20th century, Theodor Boveri described
abnormal mitosis and chromosomal changes in
cancers, and hypothesized that malignancy of the
mammalian somatic cells resulted from an abnormal
chromosomal constitution (Boveri, 1914). Later on,
Philadelphia chromosome (Ph1) was identified in the
majority of chronic myelocytic leukemia (CML),
supporting Boveri’s hypothesis. To date, a large
number of additional non-random chromosomal
translocations have been identified especially in tumors
of hematopoietic lineage (Heim and Mitelman, 1989).
In contrast, in most malignancies of epithelial origin,
including lung cancer, studies on the possible involvement of chromosomal alterations in carcinogenesis
were hampered by technical limitations. Conventional
karyotyping analysis principally requires the presence
of mitotic cells in their preparations, but primary solid
Chromosome instability in lung cancer
A Masuda and T Takahashi
6885
tumors often provide too few mitotic cells. Furthermore, the presence of very complex karyotypes in solid
tumor cells from numerical and structural points of
view often made it difficult to accomplish the
karyotyping analysis satisfactorily. In human lung
cancer, nearly all cases show complex karyotypes with
multiple structural and numerical abnormalities (Testa
and Siegfried, 1992; Testa, 1996). Approximately 70 –
80% of lung cancer cases carry from a near triploid to
tetraploid ranges of karyotypes with various structural
abnormalities including deletion, non-reciprocal translocation and isochromosome. DMs are also observed
in 20 – 30% of small cell lung cancer (SCLC) and 10 –
20% of non-small cell lung cancer (NSCLC).
Fluorescence activated cell sorter (FACS) and image
cytometric analyses can assess any overall increase or
decrease in the DNA content of a tumor cell, not only
in the mitotic phase, but also in the interphase, even
with fixed and paraffin-embedded specimens. Numerous studies have been reported on the relationships
between abnormal DNA content reflecting aneuploidy
and various clinical features including histological type,
clinical stage, sensitivity to chemotherapy, and prognosis. Although most of such studies have
demonstrated the presence of markedly abnormal
DNA contents in 65 – 85% of NSCLC and SCLC,
the relationship between aneuploidy and patient
survival remains controversial. In this connection,
Choma et al. (2001) recently conducted a meta-analysis
of data obtained with 4033 NSCLC patients in 35
previously published studies, demonstrating that
patients with tumors with abnormal DNA content
had a significantly shorter survival duration than those
with normal DNA content reflecting diploid or
psuedodiploid chromosomes. In contrast, the prognostic value of the degree of abnormal DNA ploidy does
not seem to be evident in SCLC (Oud et al., 1989;
Jackson-York et al., 1991; Viren et al., 1997).
Fluorescence in situ hybridization (FISH) analysis
with centromeric probes of a specific chromosome(s)
can obtain information of losses and gains of the
specific chromosome in each cell of a whole tissue
section or cultured cells. Although it has been
suggested that cancer cells possess persistent CIN
based on observations of the karyotypic heterogeneity
even within the same tumor, it has remained rather
ambiguous as to whether chromosomes in cancer cells
are indeed unstable, which would reflect the presence
of persistent CIN. Lengauer et al. (1997) demonstrated
by means of FISH analysis that aneuploidy in colorectal cancer cell lines is not a result of a few past
catastrophic processes of missegregations, but rather
that it reflects the persistence of an unstable karyotypic
state. Haruki et al. (2001) have also demonstrated
persistent CIN in human lung cancer cell lines with a
notable association with aneuploid karyotypes.
Recently invented novel means of cytogenetic
analysis, such as comparable genomic hybridization
(CGH) and spectral karyotyping (SKY), have allowed
a fine mapping of chromosomal losses or gains in
cancer cells, and have revealed clear pictures of non-
random losses and gains of particular chromosomal
portions even in solid tumors. CGH enables precise
analysis of losses and gains of chromosomal segments
by competitive hydridization between cancer and
normal DNAs on a karyotype spread of normal cells,
and thus does not require the abundant presence of
mitotic cells in primary cancer cells (Kallioniemi et al.,
1992). CGH studies have revealed novel and histological type-specific gains and losses of chromosome
segments in human lung cancers (Schwendel et al.,
1997; Levin et al., 1994, 1995; Petersen et al., 1997a,b),
in addition to those previously reported by conventional cytogenetic approaches.
SKY is also a powerful technique, which is based on
24-color, whole chromosome-painting assay (Liyanage
et al., 1996; Veldman et al., 1997). SKY makes it
possible to detect subtle karyotypic alterations, which
would be otherwise overlooked, as well as to identify
the chromosomal origins of abnormalities, which
would have been designated merely as a ‘marker
chromosome’ in conventional karyotyping analysis.
To date, only a few SKY studies have been reported
in lung cancers, but these have resulted in the
identification of a greater degree of chromosomal
rearrangements than those detected by previous Gbanding and CGH analyses (Luk et al., 2001; Dennis
and Stock, 1999).
As a consequence, it has become evident that the
losses and gains of chromosomes in lung cancer are not
random. It is also notable that although lung cancers
do share similar chromosomal abnormalities in
common, they also have certain histologic type-specific
characteristics of chromosomal abnormalities. The
short arm of chromosome 3 (3p) was among the first
to be identified as a non-randomly affected chromosomal region in lung cancer (Whang-Peng et al., 1982). In
addition to 3p, it has been reported that chromosomal
gains are frequent in 5p, the long arm of chromosome
8 (8q), 17q and 19q in NSCLC and 3q, 5p, 8p and Xq
in SCLC, whereas chromosome losses are frequent in
1p, 4q, 5q, 6q, 8p, 9p, 13q and 17p in NSCLC and 5q,
13q and 17p in SCLC (Schwendel et al., 1997; Levin et
al., 1994, 1995; Petersen et al., 1997a,b; Michelland et
al., 1999).
There is considerable circumstantial evidence for
the involvement of CIN in the initiation, progression,
and metastasis of human malignancies. Notable
examples are the existence of hereditary CIN
syndromes including the Ataxia telangiectasia (A-T),
Nijmegen breakage, Bloom’s and Werner syndromes
as well as Fanconi anemia, all of which are known to
be predisposed to various cancers (Wright, 1999;
Vessey et al., 1999). A few mitotic checkpoint genes
important for proper chromosome segregation have
been found to be mutated in human cancer cells
(Cahill et al., 1998; Nomoto et al., 1999; Percy et al.,
2000; Hernando et al., 2001; Gemma et al., 2000;
Sato et al., 2000), while mice deficient in the Mad2
mitotic checkpoint gene have been shown to
specifically develop lung tumors with the CIN
phenotype (Michel et al., 2001). Furthermore, the
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Chromosome instability in lung cancer
A Masuda and T Takahashi
6886
precise assay of chromosome aneuploidy in primary
tumors with G-banding, SKY and CGH have
revealed the presence of specific chromosomal
abnormalities, which correlate with distinct tumor
type, suggesting their non-random nature (Seizinger et
al., 1991; Rooney et al., 1999).
What would then be the consequence of CIN in
terms of its contributions to tumorigenesis and
progression? Several possible explanations may be
applicable, although it should be noted that these
explanations are not exclusive of one another: (1) CIN
alters chromosomal configurations, and increases the
gene dosage of growth-promoting genes, such as
oncogenes, and decreases the gene dosage of negative
regulators, such as tumor suppressor genes on the
affected chromosomes. Cancer cell clones with such
advantageous changes would eventually develop predominance during the tumor progression processes.
Gene amplification of members of the myc gene family
may be one of the typical examples. (2) CIN
accelerates the occurrence of loss of heterozygosity
(LOH) of tumor suppressor genes. In combination with
inactivation of the other allele by genetic alterations,
such as point mutations or gene silencing due to
aberrant hypermethylation or possibly due to the
naturally implemented genomic imprinting, it may lead
to complete loss of expression of the affected tumor
suppressor genes, such as p16INK4A, p53 and Rb. (3)
Global changes of gene expression may be caused by
CIN, because either loss or gain of a whole or even a
portion of a chromosome simultaneously affects
thousands of genes. Such massive changes in the gene
expression profile would provide a force sufficient to
alter the physiological balance of various cellular
systems, such as cell cycle checkpoints, metabolic and
cell cycle machineries, and cell-to-cell communications.
Since these may in turn lead to relaxation of the precise
control of cell growth and genomic fidelity, it would
consequently give cancer cells an excellent opportunity
to efficiently change their phenotypes so as to be more
malignant and suitable to their microenvironment.
and ensuring a smooth progression through the cell
cycle (Hartwell and Weinert, 1989). Thus, defects in
either cell cycle machinery or checkpoints are likely
candidates for the underlying mechanism of CIN
(Figure 1). In addition, other malfunctions of cells,
such as telomere erosion, may be involved in the
generation of CIN. In the following sections, these
possible underlying mechanisms of CIN are discussed
in reference to recent findings in lung and other human
cancers as well as to those in various experimental
systems.
Numerical CIN and its potential causes
Mitosis consists of spatially and temporally organized
complex events including nuclear envelope breakdown,
centrosome-mediated nucleation of new microtubules,
condensation and movement of chromosomes, and
cytokinesis. Failures in any of these events would
induce CIN (Figure 2). The mitotic spindle checkpoint
is activated by kinetochores that remain unattached to
the spindle and delays the cell cycle at prometaphase
until all chromosomes have established bipolar attachment. Although the precise signaling mechanism of the
mitotic spindle checkpoint remains to be clarified,
accumulating evidence points to an important role of
the Bub and Mad genes (Amon, 1999; Rundner and
Murray, 1996). The presence of an unattached
kinetochore is detected by a presently unknown
mechanism, and a complex of the Bub and Mad gene
products is then recruited to the unattached kinetochore, transmitting an activating signal to Mad2 and
BubR1 (Shah and Cleveland, 2000; Wassmann and
Benezra, 2001; Hoyt, 2001).
The Bub and Mad genes are conserved well in
mammalian genomes as well as in lower eukaryotes
such as yeast, in which they were originally identified in
the analyses of mutants that failed to arrest in response
to microtubule-depolymerizing drugs. The activated
Mad2 inhibits anaphase promoting complex/cyclosome
Potential involvement of various malfunctions of cells in
the induction of CIN
The consequence of CIN can be reflected as numerical
and structural alterations of chromosomes, with the
former often termed aneuploidy, while the latter
includes deletion, translocation, HSR and DMs. These
changes are not mutually exclusive, and in fact they are
usually detected in the same cells, perhaps because of
considerable overlap in the underlying mechanisms as
we discuss below. The cells pass through an organized
series of controlled events referred to as the cell cycle
during proliferation. In addition to the machinery
necessary for promoting cell cycle progression, cell
cycle checkpoints are built-in as a monitoring system,
which arrests cells at a particular phase of the cycle in
response to a lack of appropriate signals for cell cycle
progression, thereby maintaining the genetic stability
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Figure 1 A simplified view of signal transduction pathways
involved in the cellular responses to DNA damage and mitotic
spindle defect. Arrows and bars do not necessarily mean direct
interactions between the proteins. Molecules, alterations of which
have been reported in lung cancer, are indicated in bold
Chromosome instability in lung cancer
A Masuda and T Takahashi
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Figure 2 Possible defects of the mitotic machinery involved in the generation of missegregation of chromosomes. Failure of
anchoring of mitotic spindle to kinetochore, abnormal centrosome formation, abnormal chromosome separation and failure of
cytokinesis can cause missegregation of chromosomes and CIN
(APC/C), which is a multi-subunit E3 uniquitin ligase
associated with proteosome-mediated proteolysis,
through association with p55CDC. Since activation of
APC/C, which promotes the degradation of Securin by
26S proteosome, is a prerequisite for the sisterchromatid separation, the inhibition of APC/C consequently arrests the cell at prometaphase.
Considering the importance of the mitotic spindle
checkpoint in normal chromosome segregation, it is a
good candidate for the mechanism, defects of which
may be involved in the genesis of numerical CIN.
Indeed, Cahill et al. (1998) have reported that the
presence of the CIN phenotype in colon cancer cell
lines was tightly associated with dysfunction of the
mitotic spindle checkpoint. A significant fraction (up to
40%) of lung cancer cell lines also exhibit mitotic
spindle checkpoint defects (Takahashi et al., 1999), but
CIN in lung cancer appears to be less closely related to
the presence of mitotic spindle checkpoint impairment
than that in colon cancer (Haruki et al., 2001),
suggesting the possibility that cancer type-specific
differences may exist in the major underlying causes
of CIN between these two common cancers of adults.
Mutations in the mitotic spindle checkpoint genes
have been reported in a small fraction of several types
of human cancers including lung and colon cancers,
including MAD1 in lung cancer (Nomoto et al., 1999),
MAD2 in breast and bladder cancers (Percy et al.,
2000; Hernando et al., 2001), BUB1 in lung and
colorectal cancers (Gemma et al., 2000; Sato et al.,
2000; Cahill et al., 1998), and BUBR1 in colon cancer
(Cahill et al., 1998). Considering the frequent occurrence of mitotic spindle checkpoint impairment in lung
(Takahashi et al., 1999), colon (Cahill et al., 1998), and
nasopharyngeal cancers (Wang et al., 2000) as well as
possibly in other types of human cancers, the relative
scarcity of alterations in the mitotic spindle checkpoint
genes may point to the possibilities of an inactivating
mechanism other than mutation or an as yet
unidentified major target gene responsible for the
mitotic spindle checkpoint defects. It is also possible
that there might be a large number of affected genes
each playing a role in a small proportion of cases. In
this connection, it is interesting to note that haploinsufficiency of the MAD2 gene resulted in a defective
mitotic spindle checkpoint in both human cancer cells
and murine primary embryonic fibroblasts (MEFs) and
that mad2 (+/7) mice developed lung tumors at
unusually high rates after long latencies (Michel et al.,
2001). Frequent loss of heterozygosity in 4q, where
MAD2 resides, has been reported in lung cancer
(Petersen et al., 1997a,b; Girard et al., 2000; Ullmann
et al., 2001; Pei et al., 2001) as well as in other types of
human cancers including Hodgkin’s disease, hepatocellular carcinomas, and breast cancers (Dohner et al.,
1992; Rashid et al., 1999; Shivapurkar et al., 1999).
Several lines of evidence suggests the possibility that
inactivation of a colon tumor suppressor protein, APC,
may also lead to CIN. The C-terminal domain of APC
binds to microtubules as well as to a protein called
EB1. It has been shown that the EB1 protein associates
at the spindle microtubules and centrosomes, and
functions in the cytokinesis checkpoint (Muhua et al.,
1998). Recently, APC was also suggested to play a role
in kinetochore-microtubule attachment, whereas truncated mutations of APC, which eliminate microtubule
binding, induce chromosomal missegregation and the
CIN phenotype (Kaplan et al., 2001; Fodde et al.,
2001). Tighe et al. (2001) recently reported that
introduction of a mutant APC into a non-CIN
colorectal cancer cell line with the intact mitotic
spindle checkpoint impaired mitotic delay following
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Chromosome instability in lung cancer
A Masuda and T Takahashi
6888
spindle damage, providing additional support for its
possible involvement. Although p53 was once suggested
to play a role in the mitotic checkpoint, it is now well
accepted that p53 is involved in the post-mitotic
checkpoint, where it prevents endoreduplication (Lanni
and Jacks, 1998; Khan and Wahl, 1998; Notterman et
al., 1998).
Scolnick and Halazonetis (2000) recently identified a
gene, named CHFR, which appears to coordinate
another important phase of cell cycle progression,
i.e., mitotic prophase. Interestingly, they also identified
a loss of CHFR expression in one neuroblastoma and
two colon cancer cell lines, although the molecular
mechanism underlying the inactivation remained
unclear. Mizuno et al. (2002) found that CHFR
transcripts were undetectable in a fraction of lung
cancer cell lines and that this appeared to be due to
aberrant hypermethylation of the promoter region of
CHFR, although it remains to be clarified whether loss
of CHFR directly contributes to the acquisition of
CIN.
Defects or abnormal regulation of molecules constituting the mitotic machinery may also induce
missegregation of chromosomes, and thus they are
candidates for the causes of CIN in human cancers.
Centrosomes, which consist of a pair of centrioles
surrounded by a pericentriolar protein matrix, play a
pivotal role in organizing the microtubule network in
interphase and the mitotic spindle at M phase.
Inappropriate centrosome duplication and multipolar
mitosis was first suggested by Boveri to be related to
the chromosome abnormalities seen in cancer (Boveri,
1914). Abnormal centrosomes are commonly seen in a
wide range of cancers including lung, breast, prostate,
brain, and colon cancers (Lingle et al., 1998; Pihan et
al., 1998). Centrosomes of tumor cells display diverse
structural alterations including an increase in their
number and size, accumulation of excess pericentriolar
material, supernumerary centriole and inappropriate
phosphorylation of centrosome proteins (Salisbury et
al., 1999; Doxsey, 2001). Normal cells duplicate a
centrosome only once at the S phase during the cell
cycle, while cyclin E and cyclin A have been suggested
to play a role in centrosome duplication (Meraldi et al.,
1999; Hinchcliffe et al., 1999; Lacey et al., 1999;
Matsumoto et al., 1999), possibly through nucleophosmin/B23 modification (Okuda et al., 2000). Increased
expression of pericentrin and g-tubulin, the components of centrosomes, are often detected in tumor cells,
suggesting their potential contribution to CIN through
formation of disorganized mitotic spindles (Pihan et
al., 1998; Shu and Joshi, 1995).
Recent experimental evidence suggests relationships
between various genetic lesions and centrosome
abnormalities in human cancers. While overexpression
of cyclin E is common in human cancers (Keyomarsi
and Herliczek, 1997), overexpression of cyclin E and
loss of p53 has been shown to synergistically induce
centrosome hyperamplification and CIN in mouse
embryonic fibroblasts (MEFs) (Mussman et al.,
2000), whereas Spruck et al. (1999) reported significant
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induction of CIN without accompanying centrosome
abnormalities by conditional overexpression of cyclin E
alone using tet/tTA gene-induction system. It was also
reported that introduction of the Aurora-A centrosome-associated
kinase,
which
is
frequently
overexpressed in multiple types of human cancers
(Sen et al., 1997; Bischoff et al., 1998; Zhou et al.,
1998), induced abnormal centrosomes and transforms
rodent fibroblastic cell lines (Bischoff et al., 1998; Zhou
et al., 1998). Overexpression of other centrosomeassociated kinases such as Aurora-B and Aurora-C has
also been reported in human colon cancers (Katayama
et al., 1999; Takahashi et al., 2000).
The p53 tumor suppressor protein may also
participate in the regulation of centrosome duplication.
Multiple copies of functionally competent centrosomes
are generated during a single cell cycle in MEFs
lacking p53 (Fukasawa et al., 1996), while introduction
of p21, a target of p53-dependent transactivation,
partially restores the centrosome duplication control
in p53-deficient cells (Tarapore et al., 2001). MEFs
from mice lacking Gadd45a, another target of p53dependent transactivation, shows centrosome amplification, unequal segregation of chromosomes due to
multiple spindle poles, and the induction of aneuploidy
(Hollander et al., 1999). Ectopic overexpression of
Mdm2, which inactivates p53, induces centrosome
hyperamplification and CIN in Swiss 3T3 cells (Carroll
et al., 1999). Human papilloma virus-E6 (HPV-E6)
oncoprotein, which inactivates p53, cooperates with the
Rb-inactivating HPV-E7 oncoprotein, resulting in the
induction of abnormal centrosomes, aberrant mitotic
spindle pole formation and genomic instability (Duensing et al., 2000). Thus, the most frequently and widely
inactivated tumor suppressor protein, p53, seems to
have a regulatory role in the process of centrosome
duplication, and this may be one of the mechanisms by
which inactivation of p53 function contributes to the
induction of CIN.
Changes in other molecules of the mitotic machinery
may also cause missegregation of chromosomes and
consequently confer the CIN phenotype, when overexpressed, mutated or functionally abrogated (Pihan
and Doxsey, 1999). While ectopic expression of
Securin, a sister-chromatid separation inhibitor, transforms NIH3T3 (Zou et al., 1999), up-regulation of
Securin has been reported in some human tumors (Saez
et al., 1999; Heaney et al., 2000). A human colorectal
cancer cell line engineered to be securin deficient was
shown to be abnormal in chromosome segregation, and
to lose chromosomes at a high frequency (Jallepalli et
al., 2001).
Oncogenes may also be involved in the genesis of
CIN. Introduction of ectopic vav-2 and mos oncogenes
have been shown to induce cytokinesis abnormalities
by uncoupling of nuclear division and cytokinesis, and
to frequently induce multinucleation and abnormal
spindles, resulting in CIN (Schuebel et al., 1998;
Fukasawa and Vande Woude, 1997). Several lines of
evidence also point to a role of mutational activation
of the ras genes, which are known to be present in
Chromosome instability in lung cancer
A Masuda and T Takahashi
6889
certain types of human cancers including lung
adenocarcinomas. Abnormal mitotic figures, mainly
characterized by lagging chromosomes in prometaphase, and the resulting various ranges of aneuploidy
were frequently observed in NIH-3T3 expressing
activated human K-ras (Hagag et al., 1990; Nigro et
al., 1996). Increased karyotypic alterations were also
observed in a chromosomally stable human colorectal
cancer cell line, SW480, in proportion to the expression
levels of ectopic human c-H-ras (de Vries et al., 1993).
Structural instability and its potential causes
Complex structural aberrations of chromosomes are
frequently seen in common epithelial tumors of adults
including lung cancer, suggesting the presence of
persistent structural CIN, although yet to be formally
proven by future experimentation. DSBs can be
introduced into the genome by intracellular stresses
such as oxidative stress as well as by environmental
stresses such as ionizing irradiation. DSBs are the most
detrimental form of DNA damage, since they can
cause erroneous rejoining of the broken genome,
conferring a high risk for gross chromosomal structural
abnormalities such as deletion, translocation, HSR and
DMs. As a consequence, loss of a chromosomal
segment may uncover an inactivating mutation occurring in the other allele of a tumor suppressor gene,
whereas significant overrepresentation of a chromosomal region may lead to overexpression of protooncogenes and/or the induction of multidrug resistance
against chemotherapy (Figure 3).
The DNA damage checkpoints prevent damaged
cells from starting DNA replication (the G1/S
checkpoint), from progressing with replication (the
intra S checkpoint) or from going into mitosis (the G2
checkpoint) (Rotman and Shiloh, 1999; Dasika et al.,
1999). Mounting evidence indicates that the p53 gene is
Figure 3 Cellular responses to DNA double-strand breaks
(DSBs). The occurrence of DSBs may be repaired by the activation of cell cycle checkpoints and DNA damage repair systems,
whereas cells with extensive damage may be eliminated by the induction of cell death. Impairment of these systems can lead to
genomic instabilities including chromosomal aberrations
involved in the DNA damage checkpoints through
various pathways, and the fact that p53 is one of the
most frequent targets for somatic alterations in various
types of human cancers including lung cancer indicates
its important role as a guardian of the genome against
various genomic insults. The ATM protein kinase
signals the occurrence of DNA damage to p53 by
phosphorylated serine 15 of p53 as well as threonine 68
of Chk2, an activated form of which in turn
phosphorylated p53 at serine 20. These modifications
stabilize, activate, and execute the effects of p53 by
transcriptional activation of various target genes such
as p21 and 14-3-3s (Harper et al., 1993; el-Deiry et al.,
1993; Hermeking et al., 1997). p21 inhibits various
cyclin-dependent kinase activity including CDK2/cyclin
E, resulting in the cell cycle arrest at the G1/S
boundary. 14-3-3s excludes Cdc2/cyclin B from the
nuclei, leading to cell cycle arrest at G2. p53R2, a novel
inducible form of a catalytic subunit of ribonucleotide
reductase, was recently identified as a downstream
target of p53 and was implicated in DNA repair,
providing intriguing evidence for a linkage between cell
cycle checkpoints and DNA repair by p53 (Yamaguchi
et al., 2001). It was recently proposed that cells severely
damaged to an unrepairable extent may be eliminated
by the p53-dependent activation of p53DINP1 and its
downstream molecule p53AIP1 (Oda et al., 2000;
Okamura et al., 2001). Among these downstream genes
of p53, inactivation of 14-3-3s due to aberrant
hypermethylation of its promoter region has been
shown to be frequent in several common cancers of
adults including lung, breast, gastric, and hepatocellular carcinomas (Ferguson et al., 2000a; Suzuki et al.,
2000; Iwata et al., 2000; Osada et al., 2002). Although
ATM appears to play a key role in the upstream of p53
in the cellular response to DNA damage, somatic
disruption of both alleles of the ATM gene is rarely
observed. In this connection, it is of note that somatic
ATM aberrations were recently reported in sporadic Bcell chronic lymphocytic leukemia (Schaffner et al.,
1999). In addition, individuals heterozygous for ATM
mutations may possibly have an increased risk for
cancer susceptibility (Khanna, 2000). The S phase
checkpoint is less well understood in terms of its
possible contribution to the generation of chromosomal aberrations. A recent study shows that the S phase
checkpoint is activated at least in part through the
ATM-Chk2-Cdc25A pathway and that overexpression
of Cdc25A cancels the S checkpoint signal through
inhibition of CDK2 activity, which is needed for DNA
synthesis (Falck et al., 2001). Interestingly, overexpression of Cdc25A has been reported in 60% of NSCLC
(Wu et al., 1998).
The G2 checkpoint prevents cells from entering into
mitosis with broken chromosome. If the G2 checkpoint
fails to provide sufficient time for repair of DNA
damage before entering mitosis, cells will have to deal
with a chromosome broken into the centromeric and
the acentric fragments. The fate of broken chromosomes in such a situation includes degradation, healing
as a truncated chromosome, and generation of a
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translocated chromosome due to fusion between two
chromosomes. Fusion between two centromerecontaining chromosomes results in the formation of a
chromosome with two centromeres, i.e., dicentric
chromosome, which lacks a considerable portion of
genetic material. Such a dicentric chromosome will be
broken in the next mitosis, after which it fuses again,
thus entering the highly unstable breakage – fusion –
bridge (BFB) cycle (McClintock, 1938, 1940; Gisselsson
et al., 2000) (Figure 4). BFB cycles are also thought to
play a role in the chromosome rearrangement and gene
amplification.
Significant data has been accumulated during the
past few years with regard to the molecules and signal
transduction pathways involved in the G2 checkpoint
(Taylor and Stark, 2001; Dasika et al., 1999; Khanna,
2000). Of particular relevance in terms of DNA
damage response of this checkpoint is phosphorylation
and subsequent activation of Chk1 and Chk2, which is
thought to be mediated preferentially by ATR and
ATM, respectively. Their activation leads to phosphorylation of Cdc25C, a phosphatase that normally
activates Cdc2, and results in Cdc25C being bound to
the 14-3-3 proteins and consequentially inactivated. It
is of interest that Konishi et al. (2002) recently
identified the presence of abnormal G2 checkpoint
response in a significant fraction of SCLC cell lines as
well as a homozygous deletion of 14-3-3e in a SCLC
cell line. Another member of the 14-3-3 family, 14-33s, which is transactivated by p53 in response to DNA
damage, has been shown to have a role in the
maintenance of G2 arrest through nuclear exclusion
of the Cdc2/cyclin B1. Somatic knockout cells of 14-33s show a loss of the normal G2 checkpoint response
to DNA damage and an accumulation of chromosomal
aberrations (Chan et al., 1999; Dhar et al., 2000). In
this connection, frequent epigenetic inactivation of 143-3s due to aberrant hypermethylation has been
reported in lung cancer (Osada et al., 2002) as well
as in a few other types of human cancers including
breast, gastric and hepatocellular carcinomas (Suzuki
et al., 2000; Ferguson et al., 2000a). Additional
evidence for the involvement of molecules implicated
in the G2 checkpoint is provided by the demonstration
of germline CHK2 mutations in family members of the
Li-Fraumeni syndrome, who do not carry p53
mutations in their germline. CHK2 has also been
shown to be somatically mutated in a small fraction of
lung cancer (Haruki et al., 2000; Matsuoka et al.,
2001).
Two distinct and complementary mechanisms, which
are termed non-homologous end joining (NHEJ) and
homologous recombination (HR), are installed in cells
for repair of detrimental DSBs, which can cause
chromosomal structural abnormalities resulting from
its erroneous rejoining of the broken genome. These
two repair pathways differ in their requirement for a
homologous template DNA and in the fidelity of DSB
repair. In contrast to generally error-free HR, NHEJ is
an error-prone pathway that joins DNA ends with no
sequence homology or those with a short homologous
Oncogene
Figure 4 The breakage – fusion – bridge (BFB) cycle resulting
from DNA double-strand breaks. (a), A broken chromosome is
replicated, resulting in two chromatids. After fusion of these chromatids at their ends by NHEJ, the chromosome breaks again at a
secondary site, and enters the BFB cycle. (b), Two broken chromosomes are fused with one another to form a dicentric chromosome with two centromeres. At mitosis, the chromosome breaks
again at a secondary site, if the two centromeres are pulled to opposite sides by mitotic spindles, and enters the BFB cycle. (c), A
chromosome broken at plural sites is fused with itself to form a
ring chromosome. Torsion or chromatid exchange during replication leads to the formation of a chromosome with two centromeres. At mitosis, the chromosome breaks again at two
secondary sites, when the two centromeres are pulled to opposite
sides by mitotic spindles, and enters the BFB cycle
sequence (510 bp), termed microhomology (Khanna
and Jackson, 2001; Ferguson and Alt, 2001) (Figure 5).
Rad50-Mre11-NBS1 complex plays an important
role in both HR and NHEJ pathways by processing
Chromosome instability in lung cancer
A Masuda and T Takahashi
6891
Figure 5 The double-strand break (DSB) repair by either nonhomologous end-joining (NHEJ) and homologous recombination
(HR). NHEJ pathway (left). The Ku heterodimer binds to DNA
ends and recruits DNA-PKcs, while Mer11/Rad50/NBS1 are
thought to have enzymatic and/or structural roles. The XRCC4/
Ligase IV complex joins the DNA ends. HR pathway (right).
DSBs are initially processed by the Mre11/Rad50/NBS1 nuclease
complex. Rad52 protects DNA ends and RAD51 facilities DNA
strand invasion. Intact DNA from the sister chromatid or homologous chromosome is used as a template
DSBs prior to its repair. While NBS1 is phosphorylated by ATM in response to DNA damage, germline
NBS1 mutations leads to Nijmegen breakage syndrome
(NBS), an A-T like hereditary cancer prone disorder
with CIN, developmental defects, and radiosensitivity
(Petrini, 2000; Carney, 1999). MRE11 mutations have
been found in patients of another A-T-like disorder
AT-LD as well as in a small fraction of breast and
lymphoid tumors (Stewart et al., 1999; Fukuda et al.,
2001). ATM-dependent, c-Abl-mediated phosphorylation of Rad51 increases the association between Rad51
and Rad52, which play a role in HR repair. It is
notable that other proteins implicated in the orchestration of a proper Rad51 response include the breast
tumor suppressor Brca1 and Brca2. It seems that Brca1
interacts indirectly with Rad51, whereas Brca2 binds
directly to Rad51 (Chen et al., 1998; Davies et al.,
2001). Both Brca1 and Brca2 co-localize with the Rad
proteins in radiation-induced foci (Scully and Livingston, 2000). Embryonic lethality in Brca1- or Brca2deficient mice is attenuated by deficiency of p53
(Hakem et al., 1997; Sharan et al., 1997). Loss of
either Brca1 or Brca2 leads to aneuploidy in association with centrosome amplification and chromosomal
missegregation (Xu et al., 1999b; Lee et al., 1999).
While tumors in Brca2-deficient mice have been shown
to carry mutations in the mitotic spindle checkpoint
genes Bub1 or Mad3L (Lee et al., 1999), loss of p53
accelerates the formation of mammary tumors in mice
carrying conditional mutation of Brca1 (Xu et al.,
1999a). A DNA-dependent helicase Rad54, which plays
a role in a later step of HR in association with Rad51,
as well as its homologue RAD54B have been shown to
be mutated in human lymphoma, colon cancer and
breast cancer (Hiramoto et al., 1999; Matsuda et al.,
1999).
In the process of NHEJ repair, the DNA-dependent
protein kinase (DNA-PK), which is a member of PI3kinase related kinases consisting of a heterodimeric
DNA targeting subunit (Ku70 and Ku80) and a
catalytic subunit (DNA-PKcs), plays a role as one of
the key components. DNA Ligase4 (Lig4) and XRCC4
catalyze the DNA ligation step in the process of
NHEJ. Defects in any of Ku70, Ku80, XRCC4 or Lig4
have been shown to generate frequent chromosome
and chromatid breaks, premature cellular senescence
and apoptosis in their respective knockout mice (Bailey
et al., 1999; Difilippantonio et al., 2000; Ferguson et
al., 2000b; Gao et al., 2000; Karanjawala et al., 1999).
Embryonic lethality and premature senescence of
fibroblasts in NHEJ-deficient mice can be rescued by
simultaneous deficiency of p53, and they develop
progenitor B cell lymphomas (Difilippantonio et al.,
2000; Guidos et al., 1996; Vanasse et al., 1999; Frank
et al., 2000). LIG4 mutation was recently reported in a
leukemic patient, who was highly radiosensitive
(Riballo et al., 1999).
Gene amplification of certain oncogenes, including
members of the ERBB and MYC gene families, is
occasionally present in various human cancers including lung cancer (Brison, 1993), where it is often
reflected as HSR and DMs in karyotyping analysis.
The frequencies of gene amplification increase in
association with increase in tumor stage, suggesting
that the event may be involved in tumor progression
rather than in initiation. Although the molecular
mechanisms of gene amplification are not fully understood, it has been suggested that DSBs near the
amplified gene, incorrect repair and the resulting BFB
cycle may be involved in the genesis of gene
amplification (Singer et al., 2000). Quantitative
measurements have indicated that gene amplification
of the CAD gene can be induced in response to N(phosphonoacetyl)-L-aspartate (PALA) treatment at a
higher rate (1073 – 1075) in cancer cells than that
(51079) in normal cells (Tlsty et al., 1989; Tlsty,
1990). Notably, p53-deficient human fibroblasts have
been shown to be more vulnerable to CAD gene
amplification than the proficient cells (Livingstone et
al., 1992; Yin et al., 1992), suggesting that p53
inactivation may play a role in this type of genetic
instability.
Another important clue for a better understanding of
the underlying mechanisms of CIN came from recent
progress in the studies on telomere and telomerase, i.e.,
possible involvement of progressive telomere erosion in
the acquisition of CIN in cancer cells (Harley and
Sherwood, 1997; Artandi and DePinho, 2000). Even
though telomeres are essential for normal chromosome
structure and function, they cannot be fully replicated
by the conventional DNA polymerase complex.
Normal somatic cells show a progressive loss of their
telomere DNA during proliferation, whereupon they
enter replicative senescence, a non-proliferating, but
metabolically active stable state, which often accomOncogene
Chromosome instability in lung cancer
A Masuda and T Takahashi
6892
panies generation of polyploid cells (Sherwood et al.,
1988). In contrast, it is presumed that premalignant/
cancer cells, which have lost normal control of
proliferation due to the activation of oncogenes and
inactivation of tumor suppressor genes, continue to
proliferate, resulting in the extensive telomere shortening. This may consequently lead to telomere
association and subsequent formation of structurally
abnormal chromosomes, such as dicentric and ring
chromosomes. The resultant structurally abnormal
chromosomes are notably unstable by nature and
undergo the BFB cycle, providing the driving force
behind continuous generation of structurally abnormal
chromosomes (Counter et al., 1992).
Several lines of evidence suggest the occurrence of
telomere dysfunction in carcinogenesis. Human fibroblasts senesce and cease proliferation, which is
accompanied by activation of p53 as well as increased
expression of p21, p16INK4A and p14ARF (Atadja et al.,
1995; Kulju and Lehman, 1995; Alcorta et al., 1996;
Dimri et al., 2000). p53- and Rb-inactivating oncoproteins of viral origin such as SV40 large T, HPV-E6/E7
and adenovirus E1A/E1B drive presenescent cells into
extended proliferation and result in the crisis (Shay et
al., 1991; Counter et al., 1992) (Figure 6). Lack of the
p21 gene allows continued cell division despite
increasing telomere dysfunction, leading to telomere
crisis in p21-deficient, otherwise normal human fibroblasts (Brown et al., 1997). Notably, telomerasedeficient mice of successive generational matings not
only exhibit a subset of premature aging phenotypes
but also develop spontaneous tumors at a high rate,
suggesting a role of telomere erosion due to its
extensive shortening (Rudolph et al., 1999; Artandi et
al., 2000). It is notable that serial retroviral transduction of primary human fibroblast with SV40 large T,
activated H-ras, and then hTERT resulted in transfor-
Figure 6 Excessive shortening (erosion) of telomere and the occurrence of cancer cells with CIN. Telomere shortening in primary human cells leads to p53 and Rb-dependent replicative
senescence, whereas cells with inactivated p53 and Rb continue
to divide, entering telomere crisis due to telomere erosion. Reactivation of telomerase, which is observed in 80 – 90% of lung cancers, allows cells to escape from telomere crisis. Note that
telomere erosion may lead to the formation of unstable chromosomes such as dicentric and ring chromosomes, which are susceptible to entering the BFB cycle (See text and Figure 4)
Oncogene
mation and tumors in nude mice (Hahn et al., 1999), in
contrast to the failure of anchorage-independent
growth of fibroblasts, which were serially transduced
with hTERT, E6/E7 and then activated H-ras (Morales
et al., 1999). These findings suggest that the ordered
occurrence of telomere crisis and subsequent reexpression of telomerase may be a requisite for
malignant transformation. The precise molecular
mechanism involved in the re-expression of telomerase
in cancer cells remains to be elucidated, but several
possible candidates have recently been proposed.
Members of the Myc gene family directly transactivate
hTERT (Wang et al., 1998; Wu et al., 1999), while
Mad, an antagonizing binding partner of Myc,
represses hTERT gene expression (Oh et al., 2000).
High hTERT mRNA levels have been suggested to be
linked to myc gene overexpression in various human
cancers (Latil et al., 2000; Bieche et al., 2000; Sagawa
et al., 2001). Introduction of HPV-E6 also stimulates
the expression of hTERT through activation of
unidentified transcription factors that share the binding
site with Myc and Sp1 (Klingelhutz et al., 1996; Oh et
al., 2001). Interestingly, microcell transfer experiments
have revealed that a gene or genes that represses
expression of hTERT may be present on human
chromosome 3p, which is among the most frequently
altered regions in lung cancer (Ohmura et al., 1995;
Cuthbert et al., 1999).
Current understanding and perspective on future studies
of the molecular basis of CIN in lung cancer
There are many theoretically possible candidates for
the underlying mechanisms that would cause CIN in
lung cancer, if one takes experimental data in yeast
into consideration of human cancers. In this section,
we will discuss the current status and perspective on
the studies of potential underlying mechanisms of CIN
in lung cancer as well as the direction of future studies,
based on the molecular genetic and cytogenetic findings
thus far identified in this tumor type.
Many molecules or pathways can be nominated as a
potential candidate for lesions, alterations of which
may directly contribute to the acquisition of the CIN
phenotype in human lung cancer. One such example
would be an abnormal centrosome. It is well
recognized that centrosomes are frequently overrepresented in lung cancer with significant atypia in
shape, size, and composition (Pihan et al., 1998). A
fairly good correlation has been reported between
centrosome abnormalities and the CIN phenotype in
lung cancer cell lines (Haruki et al., 2001). As discussed
above, orderly duplication of centrosomes requires
regulated expression of cyclin E and cyclin A, and
overexpression of cyclin E has been shown to induce
centrosome abnormalities and numerical CIN in
combination with loss of p53 in rodent embryonic
fibroblasts (Spruck et al., 1999; Mussman et al., 2000).
In this context, frequent overexpression of cyclin E and
cyclin A has been shown in lung cancer (Volm et al.,
Chromosome instability in lung cancer
A Masuda and T Takahashi
6893
1997; Dobashi et al., 1998; Mishina et al., 2000;
Fukuse et al., 2000). In addition, frequent genetic and
epigenetic alterations present in lung cancer may be
associated with the induction of CIN in this scheme.
Mutations in the RB gene, which are frequent
especially in SCLC (Harbour et al., 1988), may
conceivably result in the deregulated expression of
cyclin E and cyclin A through the consequential E2Fmediated transactivation (Harbour and Dean, 2000),
which would in turn confer CIN to lung cancer cells.
Inactivation of p16INK4A due to aberrant hypermethylation, which is present almost exclusively in NSCLC,
may have similar consequences in terms of the
generation of CIN, because loss of p16INK4A impairs
its negative regulatory function on the CDK4 activity
that inhibits Rb function.
Another important candidate is defects in the mitotic
spindle checkpoint. Lung cancer cells lines have been
shown to carry mitotic checkpoint defects up to 40%
(Takahashi et al., 1999) and those with such defects
indeed exhibited persistent ongoing CIN (Haruki et al.,
2001). It is notable that despite relatively frequent
mitotic spindle checkpoint impairment, mutations and
down-regulations of the mitotic spindle checkpoint
genes are infrequent in human lung cancer (Nomoto et
al., 1999; Gemma et al., 2000; Sato et al., 2000).
Collectively, these findings suggest that although the
impaired mitotic spindle checkpoint may have a certain
role as a CIN-inducing lesion in lung cancer, we seem
to have a missing piece(s) allowing a better understanding of how it is introduced. In this connection,
Tighe et al. (2001) recently showed that abrogation of
a colon tumor suppressor APC’s function in a nonCIN colon cancer cell line induced chromosomal
missegregation and the CIN phenotype despite retention of a robust mitotic spindle checkpoint. They also
reported the presence of APC mutations correlated
well with the CIN phenotype in colon cancer cell lines.
Although APC mutations have not been reported in
lung cancer, it would be an intriguing possibility that
alterations of the signaling pathway involving APC
might play a part in the genesis of CIN in lung cancer.
The recent finding of frequent G2 checkpoint
impairment in SCLC is of considerable interest in
terms of CIN as well as other aspects (Konishi et al.,
2002). Cells with such a defect may well be susceptible
to loss of chromosomes in mitosis or initiation of the
BFB cycles as discussed above, while up to 90% of
SCLCs carry p53 mutations. It has been shown that G2
checkpoint-overriding agents such as caffeine and
pentoxyphylline enhance the sensitivity of cells that
are defective in the G1/S delay to DNA damaging
agents (Fan et al., 1995; Powell et al., 1995; Russell et
al., 1995). These findings may therefore be consistent
with the notion that SCLC is sensitive to chemo- and
radiotherapy but often recurs after the initial successful
treatment, showing aggressive clinical behavior.
Although a few genes related to the G2 checkpoint
have been found to be inactivated in lung cancer
(Haruki et al., 2000; Konishi et al., 2002; Osada et al.,
2002), further studies are necessary to identify an
additional molecule(s) that may account for the high
frequency of G2 checkpoint aberrations in SCLC as
well as to examine the contribution of the perturbed G2
checkpoint in the progression of lung cancer.
Structural abnormalities in chromosomes are
commonly seen in lung cancer, suggesting the existence
of defects in the DSB repair systems. Although the
potential involvement of defects in the DSB repair
system is conceivable, no direct evidence has yet been
obtained, and this is obviously an area requiring
thorough future investigation. In addition, human
orthologues of various genes that, when altered, can
result in CIN phenotypes in lower eukaryotes, such as
yeast, would be excellent candidates for such as yet
unidentified genetic lesions (Chen and Kolodner, 1999).
Accumulating evidence suggests that telomere
erosion and consequential formation of abnormal
chromosomes, such as dicentric and ring chromosomes
may also be involved in the acquisition of CIN as
discussed above. In this connection, telomere lengths of
lung cancer are often significantly shorter than the
normal case, and telomerase is re-activated in more
than 80% of lung cancers (Hiyama et al., 1995a,b). It
should prove interesting to investigate the timing of
these changes in premalignant lesions, since the order
of occurrence of telomere crisis and re-expression of
telomerase has been suggested to be crucial in terms of
neoplastic transformation (Morales et al., 1999).
p53 mutations are among the most frequent genetic
lesions thus far identified in lung cancer (Takahashi et
al., 1989), and it has been shown that both inactivation
of p53 and aneuploidy are detectable even in the
dysplastic lesions of the lung (Sundaresan et al., 1992;
Nuorva et al., 1993; Hirano et al., 1994). In addition,
up-regulation of MDM2 and down-regulation of
p14ARF, both of which inactivate p53 function, are
also detectable in a fraction of NSCLC (Higashiyama
et al., 1997; Vonlanthen et al., 1998). Accumulating
evidence, however, suggests that inactivation of p53
may be indirectly involved in the induction of CIN in
lung cancer by permitting cells to proliferate in the
presence of defects, which directly lead to CIN. Haruki
et al (2001) recently reported that inactivation of p53
allowed lung cancer cells to go through an inappropriate second division cycle under mitotic stresses,
resulting in the induction of the CIN phenotype in
conjunction with the generation of aneuploidy.
Furthermore a similar permissive role of abrogation
of p53 function has been shown to exist in diverse
settings, which might have relevance to the generation
of CIN in lung cancer. For example, p53 inactivation
rescues knockout mice that have defects in DSB repair
machineries from their lethality (Difilippantonio et al.,
2000; Guidos et al., 1996; Vanasse et al., 1999; Frank
et al., 2000), while telomerase deficient MEFs are more
readily transformable by cellular oncogene in cooperation with p53 deficiency (Chin et al., 1999). It is
interesting that growth defects in MEF from Brca2Tr/Tr
mice can be overcome and their cellular transformation
promoted by the expression of dominant negative
mutants of p53 or Bub1 (Lee et al., 1999). These
Oncogene
Chromosome instability in lung cancer
A Masuda and T Takahashi
6894
findings also reflect well the presence of p53 mutations
as well as either Bub1 or Mad3L mutations in tumors
arising in the Brca2Tr/Tr mice, suggesting a strong
selective pressure to remove DNA damage and mitotic
spindle checkpoints during the transformation
processes, which in turn consequently leads to the
induction of CIN. Overexpression of anti-apoptotic
genes such as BCL-2 and Survivin in lung cancer might
provide the opportunity to resist apoptotic signals in a
p53-independent manner (Pezzella et al., 1993; Monzo
et al., 1999). Finally, but no less importantly, once
alterations of chromosomes are imposed in lung cells
by the above mentioned mechanisms, the resultant
chromosomal defects themselves may provide the
driving force for maintaining persistent CIN because
of the BFB cycle and potentially abnormal number of
chromosomes itself (Gisselsson et al., 2000; Duesberg
et al., 1998; Matzke et al., 1999).
Growing evidence suggests the possible biological
and clinical impact of CIN in the pathogenesis of lung
cancer. However, currently available information is far
from sufficient to envisage the precise roles of CIN. We
have yet to identify which are the major underlying
mechanisms of CIN as well as when CIN is introduced
during the process of initiation and progression of this
fatal disease. Also, it is important to elucidate how the
presence of CIN in lung cancer cells contributes to the
carcinogenesis and progression. To answer these
important questions, systematic studies with regard to
the molecular lesions involved will certainly be
important. In addition, molecular correlative studies
on the relationship of clinical characteristics of lung
cancer patients with the presence of CIN and/or the
lesions involved should give us important clues to a
better understanding. Recent advances in the cutting
edge technology for molecular cytogenetic and cellular
biological studies as well as the enormous amount of
information about the human genome should make it
possible to further elucidate the molecular basis and
clinical importance of CIN, eventually leading us to the
development of new therapeutic approaches for this
highly prevalent and aggressive form of cancer.
Acknowledgements
We apologize for the omission of many important original
papers because of limited space. We are grateful to all
members of our division for helpful discussion and
comments on the manuscript as well as to surgical
pathologists, clinicians and surgeons of our lung cancer
research group of the Aichi Cancer Center for continuing
fruitful collaborations for many years.
References
Alcorta DA, Xiong Y, Phelps D, Hannon G, Beach D and
Barrett JC. (1996). Proc. Natl. Acad. Sci. USA, 93, 13742 –
13747.
Amon A. (1999). Curr. Opin. Genet. Dev., 9, 69 – 75.
Artandi SE, Chang S, Lee SL, Alson S, Gottlieb GJ, Chin L
and DePinho RA. (2000). Nature, 406, 641 – 645.
Artandi SE and DePinho RA. (2000). Curr. Opin. Genet.
Dev., 10, 39 – 46.
Atadja P, Wong H, Garkavtsev I, Veillette C and Riabowol
K. (1995). Proc. Natl. Acad. Sci. USA, 92, 8348 – 8352.
Bailey SM, Meyne J, Chen DJ, Kurimasa A, Li GC, Lehnert
BE and Goodwin EH. (1999). Proc. Natl. Acad. Sci. USA,
96, 14899 – 14904.
Bieche I, Nogues C, Paradis V, Olivi M, Bedossa P, Lidereau
R and Vidaud M. (2000). Clin. Cancer Res., 6, 452 – 459.
Bischoff JR, Anderson L, Zhu Y, Mossie K, Ng L, Souza B,
Schryver B, Flanagan P, Clairvoyant F, Ginther C, Chan
CS, Novotny M, Slamon DJ and Plowman GD. (1998).
EMBO J., 17, 3052 – 3065.
Boveri T. (1914). Zur Frage der Enstehung Maligner
Tumoren. Jena: Gustav Fisher Verlag.
Brison O. (1993). Biochim. Biophys. Acta, 1155, 25 – 41.
Brown JP, Wei W and Sedivy JM. (1997). Science, 277, 831 –
834.
Cahill DP, Lengauer C, Yu J, Riggins GJ, Willson JK,
Markowitz SD, Kinzler KW and Vogelstein B. (1998).
Nature, 392, 300 – 303.
Carney JP. (1999). Curr. Opin. Immunol., 11, 443 – 447.
Carroll PE, Okuda M, Horn HF, Biddinger P, Stambrook
PJ, Gleich LL, Li YQ, Tarapore P and Fukasawa K.
(1999). Oncogene, 18, 1935 – 1944.
Chan TA, Hermeking H, Lengauer C, Kinzler KW and
Vogelstein B. (1999). Nature, 401, 616 – 620.
Oncogene
Chen C and Kolodner RD. (1999). Nat. Genet., 23, 81 – 85.
Chen J, Silver DP, Walpita D, Cantor SB, Gazdar AF,
Tomlinson G, Couch FJ, Weber BL, Ashley T, Livingston
DM and Scully R. (1998). Mol. Cell., 2, 317 – 328.
Chin L, Artandi SE, Shen Q, Tam A, Lee SL, Gottlieb GJ,
Greider CW and DePinho RA. (1999). Cell, 97, 527 – 538.
Choma D, Daures JP, Quantin X and Pujol JL. (2001). Br. J.
Cancer, 85, 14 – 22.
Counter CM, Avilion AA, LeFeuvre CE, Stewart NG,
Greider CW, Harley CB and Bacchetti S. (1992). EMBO
J., 11, 1921 – 1929.
Cuthbert AP, Bond J, Trott DA, Gill S, Broni J, Marriott A,
Khoudoli G, Parkinson EK, Cooper CS and Newbold RF.
(1999). J. Natl. Cancer Inst., 91, 37 – 45.
Dasika GK, Lin SC, Zhao S, Sung P, Tomkinson A and Lee
EY. (1999). Oncogene, 18, 7883 – 7899.
Davies AA, Masson JY, McIlwraith MJ, Stasiak AZ, Stasiak
A, Venkitaraman AR and West SC. (2001). Mol. Cell, 7,
273 – 282.
de Vries JE, Kornips FH, Marx P, Bosman FT, Geraedts JP
and ten Kate J. (1993). Cancer Genet. Cytogenet., 67, 35 –
43.
Dennis TR and Stock AD. (1999). Cancer Genet. Cytogenet.,
113, 134 – 140.
Dhar S, Squire JA, Hande MP, Wellinger RJ and Pandita
TK. (2000). Mol. Cell. Biol., 20, 7764 – 7772.
Difilippantonio MJ, Zhu J, Chen HT, Meffre E, Nussenzweig MC, Max EE, Ried T and Nussenzweig A. (2000).
Nature, 404, 510 – 514.
Dimri GP, Itahana K, Acosta M and Campisi J. (2000). Mol.
Cell. Biol., 20, 273 – 285.
Dobashi Y, Shoji M, Jiang SX, Kobayashi M, Kawakubo Y
and Kameya T. (1998). Am. J. Pathol., 153, 963 – 972.
Chromosome instability in lung cancer
A Masuda and T Takahashi
6895
Dohner H, Bloomfield CD, Frizzera G, Frestedt J and
Arthur DC. (1992). Genes Chromosomes Cancer, 5, 392 –
398.
Doxsey S. (2001). Nat. Rev. Mol. Cell. Biol., 2, 688 – 698.
Duensing S, Lee LY, Duensing A, Basile J, Piboonniyom S,
Gonzalez S, Crum CP and Munger K. (2000). Proc. Natl.
Acad. Sci. USA, 97, 10002 – 10007.
Duesberg P, Rausch C, Rasnick D and Hehlmann R. (1998).
Proc. Natl. Acad. Sci. USA, 95, 13692 – 13697.
el-Deiry WS, Tokino T, Velculescu VE, Levy DB, Parsons R,
Trent JM, Lin D, Mercer WE, Kinzler KW and Vogelstein
B. (1993). Cell, 75, 817 – 825.
Falck J, Mailand N, Syljuasen RG, Bartek J and Lukas J.
(2001). Nature, 401, 842 – 847.
Fan S, Smith ML, Rivet 2nd DJ, Duba D, Zhan Q, Kohn
KW, Fornace Jr AJ and O’Connor PM. (1995). Cancer
Res., 55, 1649 – 1654.
Ferguson AT, Evron E, Umbricht CB, Pandita TK, Chan
TA, Hermeking H, Marks JR, Lambers AR, Futreal PA,
Stampfer MR and Sukumar S. (2000a). Proc. Natl. Acad.
Sci. USA, 97, 6049 – 6054.
Ferguson DO and Alt FW. (2001). Oncogene, 20, 5572 –
5579.
Ferguson DO, Sekiguchi JM, Chang S, Frank KM, Gao Y,
DePinho RA and Alt FW. (2000b). Proc. Natl. Acad. Sci.
USA, 97, 6630 – 6633.
Fodde R, Kuipers J, Rosenberg C, Smits R, Kielman M,
Gaspar C, van Es JH, Breukel C, Wiegant J, Giles RH and
Clevers H. (2001). Natl. Cell. Biol., 3, 433 – 438.
Frank KM, Sharpless NE, Gao Y, Sekiguchi JM, Ferguson
DO, Zhu C, Manis JP, Horner J, DePinho RA and Alt
FW. (2000). Mol. Cell, 5, 993 – 1002.
Fukasawa K, Choi T, Kuriyama R, Rulong S and Vande
Woude GF. (1996). Science, 271, 1744 – 1747.
Fukasawa K and Vande Woude GF. (1997). Mol. Cell Biol.,
17, 506 – 518.
Fukuda T, Sumiyoshi T, Takahashi M, Kataoka T, Asahara
T, Inui H, Watatani M, Yasutomi M, Kamada N and
Miyagawa K. (2001). Cancer Res., 61, 23 – 26.
Fukuse T, Hirata T, Naiki H, Hitomi S and Wada H. (2000).
Cancer Res., 60, 242 – 244.
Gao Y, Ferguson DO, Xie W, Manis JP, Sekiguchi J, Frank
KM, Chaudhuri J, Horner J, DePinho RA and Alt FW.
(2000). Nature, 404, 897 – 900.
Gemma A, Seike M, Seike Y, Uematsu K, Hibino S,
Kurimoto F, Yoshimura A, Shibuya M, Harris CC and
Kudoh S. (2000). Genes Chromosomes Cancer, 29, 213 –
218.
Girard L, Zochbauer-Muller S, Virmani AK, Gazdar AF
and Minna JD. (2000). Cancer Res., 60, 4894 – 4906.
Gisselsson D, Pettersson L, Hoglund M, Heidenblad M,
Gorunova L, Wiegant J, Mertens F, Dal Cin P, Mitelman
F and Mandahl N. (2000). Proc. Natl. Acad. Sci. USA, 97,
5357 – 5362.
Guidos CJ, Williams CJ, Grandal I, Knowles G, Huang MT
and Danska JS. (1996). Genes Dev., 10, 2038 – 2054.
Hagag N, Diamond L, Palermo R and Lyubsky S. (1990).
Oncogene, 5, 1481 – 1489.
Hahn WC, Counter CM, Lundberg AS, Beijersbergen RL,
Brooks MW and Weinberg RA. (1999). Nature, 400, 464 –
468.
Hakem R, de la Pompa JL, Elia A, Potter J and Mak TW.
(1997). Nat. Genet., 16, 298 – 302.
Harbour JW and Dean DC. (2000). Genes Dev., 14, 2393 –
2409.
Harbour JW, Lai SL, Whang-Peng J, Gazdar AF, Minna JD
and Kaye FJ. (1988). Science, 241, 353 – 357.
Harley CB and Sherwood SW. (1997). Cancer Surv., 29,
263 – 284.
Harper JW, Adami GR, Wei N, Keyomarsi K and Elledge
SJ. (1993). Cell, 75, 805 – 816.
Hartwell LH and Weinert TA. (1989). Science, 246, 629 –
634.
Haruki N, Harano T, Masuda A, Kiyono T, Takahashi T,
Takematsu Y, Shimizu S, Mitsudomi T, Konishi H, Osada
H and Fujii Y. (2001). Am. J. Pathol., 159, 1345 – 1352.
Haruki N, Saito H, Tatematsu Y, Konishi H, Harano T,
Masuda A, Osada H, Fujii Y and Takahashi T. (2000).
Cancer Res., 60, 4689 – 4692.
Heaney AP, Singson R, McCabe CJ, Nelson V, Nakashima
M and Melmed S. (2000). Lancet, 355, 716 – 719.
Heim S and Mitelman F. (1989). Adv. Cancer Res., 52, 1 – 43.
Hermeking H, Lengauer C, Polyak K, He TC, Zhang L,
Thiagalingam S, Kinzler KW and Vogelstein B. (1997).
Mol. Cell, 1, 3 – 11.
Hernando E, Orlow I, Liberal V, Nohales G, Benezra R and
Cordon-Cardo C. (2001). Int. J. Cancer, 95, 223 – 227.
Higashiyama M, Doi O, Kodama K, Yokouchi H, Kasugai
T, Ishiguro S, Takami K, Nakayama T and Nishisho I.
(1997). Br. J. Cancer, 75, 1302 – 1308.
Hinchcliffe EH, Li C, Thompson EA, Maller JL and Sluder
G. (1999). Science, 283, 851 – 854.
Hiramoto T, Nakanishi T, Sumiyoshi T, Fukuda T,
Matsuura S, Tauchi H, Komatsu K, Shibasaki Y, Inui
H, Watatani M, Yasutomi M, Sumii K, Kajiyama G,
Kamada N, Miyagawa K and Kamiya K. (1999).
Oncogene, 18, 3422 – 3426.
Hirano T, Franzen B, Kato H, Ebihara Y and Auer G.
(1994). Am. J. Pathol., 144, 296 – 302.
Hiyama K, Hiyama E, Ishioka S, Yamakido M, Inai K,
Gazdar AF, Piatyszek MA and Shay JW. (1995a). J. Natl.
Cancer Inst., 87, 895 – 902.
Hiyama K, Ishioka S, Shirotani Y, Inai K, Hiyama E,
Murakami I, Isobe T, Inamizu T and Yamakido M.
(1995b). Oncogene, 10, 937 – 944.
Hollander MC, Sheikh MS, Bulavin DV, Lundgren K,
Augeri-Henmueller L, Shehee R, Molinaro TA, Kim KE,
Tolosa E, Ashwell JD, Rosenberg MP, Zhan Q,
Fernandez-Salguero PM, Morgan WF, Deng CX and
Fornace Jr AJ. (1999). Nat. Genet., 23, 176 – 184.
Hoyt MA. (2001). J. Cell Biol., 154, 909 – 911.
Iwata N, Yamamoto H, Sasaki S, Itoh F, Suzuki H, Kikuchi
T, Kaneto H, Iku S, Ozeki I, Karino Y, Satoh T, Toyota J,
Satoh M, Endo T and Imai K. (2000). Oncogene, 19, 5298 –
5302.
Jackson-York GL, Davis BH, Warren WH, Gould VE and
Memoli VA. (1991). Cancer, 68, 374 – 379.
Jallepalli PV, Waizenegger IC, Bunz F, Langer S, Speicher
MR, Peters JM, Kinzler KW, Vogelstein B and Lengauer
C. (2001). Cell, 105, 445 – 457.
Kallioniemi A, Kallioniemi OP, Sudar D, Rutovitz D, Gray
JW, Waldman F and Pinkel D. (1992). Science, 258, 818 –
821.
Kaplan KB, Burds AA, Swedlow JR, Bekir SS, Sorger PK
and Nathke IS. (2001). Nat. Cell. Biol., 3, 429 – 432.
Karanjawala ZE, Grawunder U, Hsieh CL and Lieber MR.
(1999). Curr. Biol., 9, 1501 – 1504.
Katayama H, Ota T, Jisaki F, Ueda Y, Tanaka T, Odashima
S, Suzuki F, Terada Y and Tatsuka M. (1999). J. Natl.
Cancer Inst., 91, 1160 – 1162.
Keyomarsi K and Herliczek TW. (1997). Prog. Cell Cycle
Res., 3, 171 – 191.
Khan SH and Wahl GM. (1998). Cancer Res., 58, 396 – 401.
Khanna KK. (2000). J. Natl. Cancer Inst., 92, 795 – 802.
Oncogene
Chromosome instability in lung cancer
A Masuda and T Takahashi
6896
Khanna KK and Jackson SP. (2001). Nat. Genet., 27, 247 –
254.
Klingelhutz AJ, Foster SA and McDougall JK. (1996).
Nature, 380, 79 – 82.
Konishi H, Nakagawa T, Harano T, Mizuno K, Saito H,
Masuda A, Matsuda H, Osada H and Takahashi T. (2002).
Cancer Res., 62, 271 – 276.
Kulju KS and Lehman JM. (1995). Exp. Cell Res., 217, 336 –
345.
Lacey KR, Jackson PK and Stearns T. (1999). Proc. Natl.
Acad. Sci. USA, 96, 2817 – 2822.
Lanni JS and Jacks T. (1998). Mol. Cell. Biol., 18, 1055 –
1064.
Latil A, Vidaud D, Valeri A, Fournier G, Vidaud M,
Lidereau R, Cussenot O and Biache I. (2000). Int. J.
Cancer, 89, 172 – 176.
Lee H, Trainer AH, Friedman LS, Thistlethwaite FC, Evans
MJ, Ponder BA and Venkitaraman AR. (1999). Mol. Cell,
4, 1 – 10.
Lengauer C, Kinzler KW and Vogelstein B. (1997). Nature,
386, 623 – 637.
Levin NA, Brzoska P, Gupta N, Minna JD, Gray JW and
Christman MF. (1994). Cancer Res., 54, 5086 – 5091.
Levin NA, Brzoska PA, Warnock ML, Gray JW and
Christman MF. (1995). Genes Chromosomes Cancer, 13,
175 – 185.
Lingle WL, Lutz WH, Ingle JN, Maihle NJ and Salisbury JL.
(1998). Proc. Natl. Acad. Sci. USA, 95, 2950 – 2955.
Livingstone LR, White A, Sprouse J, Livanos E, Jacks T and
Tlsty TD. (1992). Cell, 70, 923 – 935.
Liyanage M, Coleman A, du Manoir S, Veldman T,
McCormack S, Dickson RB, Barlow C, Wynshaw-Boris
A, Janz S, Wienberg J, Ferguson-Smith MA, Schrock E
and Ried T. (1996). Nat. Genet., 14, 312 – 315.
Luk C, Tsao MS, Bayani J, Shepherd F and Squire JA.
(2001). Cancer Genet. Cytogenet., 125, 87 – 99.
Matsuda M, Miyagawa K, Takahashi M, Fukuda T,
Kataoka T, Asahara T, Inui H, Watatani M, Yasutomi
M, Kamada N, Dohi K and Kamiya K. (1999). Oncogene,
18, 3427 – 3430.
Matsumoto Y, Hayashi K and Nishida E. (1999). Curr. Biol.,
9, 429 – 432.
Matsuoka S, Nakagawa T, Masuda A, Haruki N, Elledge SJ
and Takahashi T. (2001). Cancer Res., 61, 5362 – 5365.
Matzke MA, Scheid OM and Matzke AJ. (1999). Bioessays,
21, 761 – 767.
McClintock B. (1938). Genetics, 23, 215 – 376.
McClintock B. (1940). Genetics, 26, 234 – 282.
Meraldi P, Lukas J, Fry AM, Bartek J and Nigg EA. (1999).
Nat. Cell Biol., 1, 88 – 93.
Michel LS, Liberal V, Chatterjee A, Kirchwegger R, Pasche
B, Gerald W, Dobles M, Sorger PK, Murty VV and
Benezra R. (2001). Nature, 409, 355 – 359.
Michelland S, Gazzeri S, Brambilla E and Robert-Nicoud M.
(1999). Cancer Genet. Cytogenet, 114, 22 – 30.
Mishina T, Dosaka-Akita H, Hommura F, Nishi M, Kojima
T, Ogura S, Shimizu M, Katoh H and Kawakami Y.
(2000). Clin. Cancer Res., 6, 11 – 16.
Mizuno K, Osada H, Konishi H, Tatematsu Y, Yatabe Y,
Mitsudomi T, Fujii Y and Takahashi T. (2002). Oncogene,
21, 2328 – 2333.
Monzo M, Rosell R, Felip E, Astudillo J, Sanchez JJ,
Maestre J, Martin C, Font A, Barnadas A and Abad A.
(1999). J. Clin. Oncol., 17, 2100 – 2104.
Morales CP, Holt SE, Ouellette M, Kaur KJ, Yan Y, Wilson
KS, White MA, Wright WE and Shay JW. (1999). Nat.
Genet., 21, 115 – 118.
Oncogene
Muhua L, Adames NR, Murphy MD, Shields CR and
Cooper JA. (1998). Nature, 393, 487 – 491.
Mussman JG, Horn HF, Carroll PE, Okuda M, Tarapore P,
Donehower LA and Fukasawa K. (2000). Oncogene, 19,
1635 – 1646.
Nigro S, Geido E, Infusini E, Orecchia R and Giaretti W.
(1996). Int. J. Cancer, 67, 871 – 875.
Nomoto S, Haruki N, Takahashi T, Masuda A, Koshikawa
T, Fujii Y and Osada H. (1999). Oncogene, 18, 7180 – 7183.
Notterman D, Young S, Wainger B and Levine AJ. (1998).
Oncogene, 17, 2743 – 2751.
Nuorva K, Soini Y, Kamel D, Autio-Harmainen H, Risteli
L, Risteli J, Vahakangas K and Paakko P. (1993). Am. J.
Pathol., 142, 725 – 732.
Oda K, Arakawa H, Tanaka T, Matsuda K, Tanikawa C,
Mori T, Nishimori H, Tamai K, Tokino T, Nakamura Y
and Taya Y. (2000). Cell, 102, 849 – 862.
Oh S, Song YH, Yim J and Kim TK. (2000). Oncogene, 19,
1485 – 1490.
Oh ST, Kyo S and Laimins LA. (2001). J. Virol., 75, 5559 –
5566.
Ohmura H, Tahara H, Suzuki M, Ide T, Shimizu M, Yoshida
MA, Tahara E, Shay JW, Barrett JC and Oshimura M.
(1995). Jpn. J. Cancer Res., 86, 899 – 904.
Okamura S, Arakawa H, Tanaka T, Nakanishi H, Ng CC,
Taya Y, Monden M and Nakamura Y. (2001). Mol. Cell.,
8, 85 – 94.
Okuda M, Horn HF, Tarapore P, Tokuyama Y, Smulian
AG, Chan PK, Knudsen ES, Hofmann IA, Snyder JD,
Bove KE and Fukasawa K. (2000). Cell, 103, 127 – 140.
Osada H, Tatematsu Y, Yatabe Y, Nakagawa T, Konishi H,
Harano T, Tezel E, Takada M and Takahashi T. (2002).
Oncogene, 21, 2418 – 2424.
Oud PS, Pahlplatz MM, Beck JL, Wiersma-Van Tilburg A,
Wagenaar SJ and Vooijs GP. (1989). Cancer, 64, 1304 –
1309.
Pei J, Balasara BR, Li W, Litwin S, Gabrielson E, Feder M,
Jen J and Testa JR. (2001). Genes Chromosomes Cancer,
31, 282 – 287.
Percy MJ, Myrie KA, Neeley CK, Azim JN, Ethier SP and
Petty EM. (2000). Genes Chromosomes Cancer, 29, 356 –
362.
Petersen I, Bujard M, Petersen S, Wolf G, Goeze A,
Schwendel A, Langreck H, Gellert K, Reichel M, Just K,
du Manoir S, Cremer T, Dietel M and Ried T. (1997a).
Cancer Res., 57, 2331 – 2335.
Petersen I, Langreck H, Wold G, Schwendel A, Psille R,
Vogt P, Reichel MB, Ried T and Dietel M. (1997b). Br. J.
Cancer, 75, 79 – 86.
Petrini JH. (2000). Curr. Opin. Cell Biol., 12, 293 – 296.
Pezzella F, Turley H, Kuzu I, Tungekar MF, Dunnill MS,
Pierce CB, Harris A, Gatter KC and Mason DY. (1993). N.
Engl. J. Med., 329, 690 – 694.
Pihan GA and Doxsey SJ. (1999). Semin. Cancer Biol., 9,
289 – 302.
Pihan GA, Purohit A, Wallace J, Knecht H, Woda B,
Quesenberry P and Doxsey SJ. (1998). Cancer Res., 58,
3974 – 3985.
Powell SN, DeFrank JS, Connell P, Eogan M, Preffner F,
Dombkowski D, Tang W and Friend S. (1995). Cancer
Res., 55, 1643 – 1648.
Rashid A, Wang JS, Qian GS, Lu BX, Hamilton SR and
Groopman JD. (1999). Br. J. Cancer, 80, 59 – 66.
Riballo E, Critchlow SE, Teo SH, Doherty AJ, Priestley A,
Broughton B, Kysela B, Beamish H, Plowman N, Arlett
CF, Lehmann AR, Jackson SP and Jeggo PA. (1999). Curr.
Biol., 9, 699 – 702.
Chromosome instability in lung cancer
A Masuda and T Takahashi
6897
Rooney PH, Murray GI, Stevenson DA, Haites NE, Cassidy
J and McLeod HL. (1999). Br. J. Cancer, 80, 862 – 873.
Rotman G and Shiloh Y. (1999). Oncogene, 18, 6135 – 6144.
Rudner AD and Murray AW. (1996). Curr. Opin. Cell Biol.,
8, 773 – 780.
Rudolph KL, Chang S, Lee HW, Blasco M, Gottlieb GJ,
Greider C and DePinho RA. (1999). Cell, 96, 701 – 712.
Russell KJ, Wiens LW, Demers GW, Galloway DA, Plon SE
and Groudine M. (1995). Cancer Res., 55, 1639 – 1642.
Saez C, Japon MA, Ramos-Morales F, Romero F, Segura
DI, Tortolero M and Pintor-Toro JA. (1999). Oncogene,
18, 5473 – 5476.
Sagawa Y, Nishi H, Isaka K, Fujito A and Takayama M.
(2001). Cancer Lett., 168, 45 – 50.
Salisbury JL, Whitehead CM, Lingle WL and Barrett SL.
(1999). Biol. Cell, 91, 451 – 460.
Sato M, Sekido Y, Horio Y, Takahashi M, Saito H, Minna
JD, Shimokata K and Hasegawa Y. (2000). Jpn. J. Cancer
Res., 91, 504 – 509.
Schaffner C, Stilgenbauer S, Rappold GA, Dohner H and
Lichter P. (1999). Blood, 94, 748 – 753.
Schuebel KE, Movilla N, Rosa JL and Bustelo XR. (1998).
EMBO J., 17, 6608 – 6621.
Schwendel A, Langreck H, Reichel M, Schrock E, Ried T,
Dietal M and Petersen I. (1997). Int. J. Cancer, 74, 86 – 93.
Scolnick DM and Halazonetis TD. (2000). Nature, 406, 430 –
435.
Scully R and Livingston DM. (2000). Nature, 408, 429 – 432.
Seizinger BR, Klinger HP, Junien C, Nakamura Y, Le Beau
M, Cavenee W, Emanuel B, Ponder B, Naylor S, Mitelman
F, Louis D, Menon A, Newsham I, Decker J, Kaelbling M,
Henry I and Deimling A. (1991). Cytogenet. Cell Genet.,
58, 1080 – 1096.
Sen S, Zhou H and White RA. (1997). Oncogene, 14, 2195 –
2200.
Shah JV and Cleveland DW. (2000). Cell, 103, 997 – 1000.
Sharan SK, Morimatsu M, Albrecht U, Lim DS, Regel E,
Dinh C, Sands A, Eichele G, Hasty P and Bradley A.
(1997). Nature, 386, 804 – 810.
Shay JW, Pereira-Smith OM and Wright WE. (1991). Exp.
Cell Res., 196, 33 – 39.
Sherwood SW, Rush D, Ellsworth JL and Schimke RT.
(1988). Proc. Natl. Acad. Sci. USA, 85, 9086 – 9090.
Shivapurkar N, Sood S, Wistuba II, Virmani AK, Maitra A,
Milchgrub S, Minna JD and Gazdar AF. (1999). Cancer
Res., 59, 3576 – 3580.
Shu HB and Joshi HC. (1995). J. Cell Biol., 130, 1137 – 1147.
Singer MJ, Mesner LD, Friedman CL, Trask BJ and Hamlin
JL. (2000). Proc. Natl. Acad. Sci, USA,, 97, 7921 – 7926.
Spruck CH, Won KA and Reed SI. (1999). Nature, 401,
297 – 300.
Stewart GS, Maser RS, Stankovic T, Bressan DA, Kaplan
MI, Jaspers NG, Raams A, Byrd PJ, Petrini JH and Taylor
AM. (1999). Cell, 99, 577 – 587.
Sundaresan V, Ganly P, Hasleton P, Rudd R, Sinha G,
Bleehen NM and Rabbitts P. (1992). Oncogene, 7, 1989 –
1997.
Suzuki H, Itoh F, Toyota M, Kikuchi T, Kakiuchi H and
Imai K. (2000). Cancer Res., 60, 4353 – 4357.
Takahashi T, Futamura M, Yoshimi N, Sano J, Katada M,
Takagi Y, Kimura M, Yoshioka T, Okano Y and Saji S.
(2000). Jpn. J. Cancer Res., 91, 1007 – 1014.
Takahashi T, Haruki N, Nomoto S, Masuda A, Saji S and
Osada H. (1999). Oncogene, 18, 4295 – 4300.
Takahashi T, Nau MM, Chiba I, Birrer MJ, Rosenberg RK,
Vinocour M, Levitt M, Pass H, Gazdar AF and Minna JD.
(1989). Science, 246, 491 – 494.
Tarapore P, Horn HF, Tokuyama Y and Fukasawa K.
(2001). Oncogene, 20, 3173 – 3184.
Taylor WR and Stark GR. (2001). Oncogene, 20, 1803 – 1815.
Testa JR. (1996). Lung Cancer. Pass HI, Mitchell JB,
Johnson DH and Turrisi AT. (eds). Philadelphia:
Lippincott-Raven, pp 55 – 71.
Testa JR and Siegfried JM. (1992). Cancer Res., 52, 2702s –
2706s.
Tighe A, Johnson VL, Albertella M and Taylor SS. (2001).
EMBO Rep., 2, 609 – 614.
Tlsty TD. (1990). Proc. Natl. Acad. Sci. USA, 87, 3132 –
3136.
Tlsty TD, Margolin BH and Lum K. (1989). Proc. Natl.
Acad. Sci. USA, 86, 9441 – 9445.
Ullmann R, Petzmann S, Sharma A, Cagle PT and Popper
HH. (2001). Hum. Pathol., 32, 1059 – 1063.
Vanasse GJ, Halbrook J, Thomas S, Burgess A, Hoekstra
MF, Disteche CM and Willerform DM. (1999). J. Clin.
Invest., 103, 1669 – 1675.
Veldman T, Vignon C, Schrock E, Rowley JD and Ried T.
(1997). Nat. Genet., 15, 406 – 410.
Vessey CJ, Norbury CJ and Hickson ID. (1999). Prog.
Nucleic Acid Res. Mol. Biol., 63, 189 – 221.
Viren MM, Ojala AT, Kataja VV, Mattila JJ, Koiviso PA
and Nikkanen VT. (1997). Med. Oncol., 14, 35 – 38.
Volm M, Koomagi R, Mattern J and Stammler G. (1997). Br.
J. Cancer, 75, 1774 – 1778.
Vonlanthen S, Heighway J, Tschan MP, Borner MM,
Altermatt HJ, Kappeler A, Tobler A, Fey MF, Thatcher
N, Yarbrough WG and Betticher DC. (1998). Oncogene,
17, 2779 – 2785.
Wang J, Xie LY, Allan S, Beach D and Hannon GJ. (1998).
Genes Dev., 12, 1769 – 1774.
Wang X, Jin DY, Wong YC, Cheung AL, Chun AC, Lo AK,
Liu Y and Tsao SW. (2000). Carcinogenesis, 21, 2293 –
2297.
Wassmann K and Benezra R. (2001). Curr. Opin. Genet.
Dev., 11, 83 – 90.
Whang-Peng J, Kao-Shan CS, Lee EC, Bunn PA, Carney
DN, Gazdar AF and Minna JD. (1982). Science, 215, 181 –
182.
Wright EG. (1999). J. Pathol., 187, 19 – 27.
Wu KJ, Grandori C, Amacker M, Simon-Vermot N, Polack
A, Lingner J and Dalla-Favera R. (1999). Nat. Genet., 21,
220 – 224.
Wu W, Fan YH, Kemp BL, Walsh G and Mao L. (1998).
Cancer Res., 58, 4082 – 4085.
Xu X, Wagner KU, Larson D, Weaver Z, Li C, Ried T,
Hennighausen L, Wynshaw-Boris A and Deng CX.
(1999a). Nat. Genet., 22, 37 – 43.
Xu X, Weaver Z, Linke SP, Li C, Gotay J, Wang XW, Harris
CC, Ried T and Deng CX. (1999b). Mol. Cell, 3, 389 – 395.
Yamaguchi T, Matsuda K, Sagiya Y, Iwadate M, Fujino
MA, Nakamura Y and Arakawa H. (2001). Cancer Res.,
61, 8256 – 8262.
Yin Y, Tainsky MA, Fischoff FZ, Strong LC and Wahl GM.
(1992). Cell, 70, 937 – 948.
Zhou H, Kuang J, Zhong L, Kuo WL, Gray JW, Sahin A,
Brinkley BR and Sen S. (1998). Nat. Genet., 20, 189 – 193.
Zou H, McGarry TJ, Bernal T and Kirschner MW. (1999).
Science, 285, 418 – 422.
Oncogene