Download Cytogenetics and Molecular Genetics of Bone and Soft

American Journal of Medical Genetics (Semin. Med. Genet.) 115:189 –193 (2002)
A R T I C L E
Cytogenetics and Molecular Genetics of Bone
and Soft-Tissue Tumors
AVERY A. SANDBERG*
The cytogenetic and molecular findings in bone and soft-tissue sarcomas are summarized. A table presenting all such
tumors, with their specific translocations and the genes involved, is included, along with a list of those tumors that
most likely result from a stepwise process of numerous genetic changes. ß 2002 Wiley-Liss, Inc.
KEY WORDS: soft-tissue sarcomas; bone tumors; chromosome changes; molecular abnormalities
For cytogenetic and molecular data
on bone and soft-tissue tumors up to
1994, the reader may wish to consult
the book by Sandberg and Bridge
[1994]. For more recent information,
an ongoing series of updates on various
bone and soft-tissue tumors are available
[Sandberg and Bridge, 2001a,b, in press],
as are several comprehensive reviews
[Barr et al., 1995; Sorensen and Triche,
1996; Åman, 1999; Ladanyi and Bridge,
2000]. The cytogenetic and molecular
aspects of bone and soft-tissue tumors,
most of them sarcomas, have received
much attention lately. From a cytogenetic viewpoint, these tumors are relatively easy to grow in vitro and hence
yield metaphases for chromosome
analysis. Most important, a substantial
number of these tumors are characterized by specific cytogenetic changes,
usually translocations (Table I). In a
significant proportion of these tumors
(Table I), the translocation is the sole
cytogenetic anomaly, indicating the probable causative role of this translocation
in the genesis of these tumors. Generally,
when there are additional chromosomal
changes, the tumor is usually more
aggressive than when the translocation
is the sole anomaly. At a molecular level,
almost all the genes involved in these
Avery A. Sandberg, M.D., D.Sc., is Editorin-Chief of Cancer Genetics and Cytogenetics; Clinical Consultant in the Department
of DNA Diagnostics at St. Joseph’s Hospital
and Medical Center in Phoenix, Arizona; and
Clinical Professor in Pathology at the University of Arizona in Tucson.
*Correspondence to: Avery A. Sandberg,
M.D., D.Sc., Department of DNA Diagnostics, St. Joseph’s Hospital and Medical
Center, 350 West Thomas Road, Phoenix,
AZ 85013. E-mail: [email protected]
DOI 10.1002/ajmg.10691
Inflammatory myofibroblastic tumor
ß 2002 Wiley-Liss, Inc.
translocations have been identified, leading to their utilization in establishing the
diagnosis in confusing tumors, particularly when fresh tissue for cytogenetic
analysis is not available. The application of molecular approaches, including
TABLE I. Specific Chromosomal Translocations Established Cytogenetically
and the Corresponding Gene Changes in Bone and Soft-Tissue Tumors
Tumors
Alveolar rhabdomyosarcoma
Alveolar soft-part sarcoma
Clear-cell sarcoma (malignant
melanoma of soft parts)
Congenital fibrosarcoma and
mesoblastic nephroma
Dermatofibrosarcoma protuberans
(giant-cell fibroblastoma)
Desmoplastic round-cell tumor
Endometrial stromal sarcoma
Ewing sarcoma and peripheral
primitive neuroectodermal tumors
Myxoid chondrosarcoma, extraskeletal
Myxoid liposarcoma
Synovial sarcoma
Translocation
Gene changes
t(2;13)(q35;q14)
t(1;13)(p36;q14)
t(X;17)(p11.2;q25)
t(12;22)(q13;q12)
PAX3-FKHR
PAX7-FKHR
ASPL-TFE3
ATF1-EWS
t(12;15)(p13;q25)
ETV6-NTRK3
t(17;22)(q22;q13)
COL1A1-PDGFB
t(11;22)(p13;q12)
t(7;17)(p15;q21)
t(11;22)(q24;q12)
WT1-EWS
JAZF1-JJAZ1
EWS-FLI1
t(21;22)(q22;q12)
t(7;22)(p22;q12)
t(17;22)(q12;q12)
t(2;22)(q33;q12)
t(2;19)(p23;p13.1)
t(1;2)(q22-23;p23)
t(9;22)(q22;q12)
t(9;17)(q22;q11)
t(9;15)(q22;q21)
t(12;16)(q13;p11)
t(12;22)(q13;q12)
t(X;18)(p11;q11)
EWS-ERG
EWS-ETV1
EWS-E1AF
FEV-EWS
ALK-TPM4
TPM3-ALK
EWS-CHN(TEC)
RBP56-CHN(TEC)
TEC-TCF12
TLS(FUS)-CHOP
EWS-CHOP
SYT-SSX1
SYT-SSX2
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AMERICAN JOURNAL OF MEDICAL GENETICS (SEMIN. MED. GENET.)
fluorescence in situ hybridization of
various types, to archival tissue has been
a major development in the field.
In a significant proportion
of these tumors . . . the
translocation is the sole
cytogenetic anomaly, indicating
the probable causative role of
this translocation in the
genesis of these tumors.
A revealing advance has been the
finding in some sarcomas that the
variability in fusion products, due to
variability in intragenic breakpoints, may
have clinical application, such as in prognosis [Lin et al., 1999]. This has been
established in the case of Ewing sarcoma,
and similar observations probably also
will be made for other types of sarcomas.
The figure shown in this article utilizes
some of the cytogenetic and molecular
findings from Ewing sarcoma and related
tumors and serves as an example of the
nature of changes that may be encountered in bone and soft-tissue sarcomas
and the possible events and the meaning
associated with these changes.
Figure 1 shows a karyotype from a
Ewing sarcoma with the characteristic
t(11;22)(q24;q12) (horizontal arrows).
The vertical arrows point to additional
chromosomal changes (þ 3, þ 7, þ 8,
and þ 9) that generally indicate a more
aggressive tumor than those containing
the translocation as a sole cytogenetic
event. The latter is seen not infrequently
in Ewing and other sarcomas. Figure 2 is
a schematic presentation of the t(11;22)
translocation in Ewing sarcoma and a
partial karyotype of this translocation.
Figure 3 is a schematic presentation of
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the molecular genetic events resulting
from the t(11;22) in Ewing sarcoma,
that is, the break in the EWS gene
and the break in the FLI gene leading
to the for-mation of an abnormal fusion
gene EWS-FLI1. The latter is thought
to be the direct cause of the development
of Ewing sarcoma. Note that the break
on the EWS gene may occur in different
parts of an alternate splicing area, as it
may on the FLI gene, leading to different
fusion products (see Fig. 4).
The upper part of Figure 3 shows
the structure of the EWS and FLI1
genes, with arrowheads indicating the
naturally occurring fusion sites in the
chimeric transcripts resulting from the
t(11;22)q24;q12) and the fusion of the 50
end of the EWS gene and the 30 end of
the FLI1 gene, with considerable combinatorial diversity of junctions. The
transactivating domain of EWS is
retained in EWS-FLI1; the RNA
domain is lost. The FLI1 gene encodes
Figure 1. Karyotype of a Ewing sarcoma with the characteristic t(11;22)(q24;q12) seen in this tumor. Among the additional changes,
trisomy 8 (þ8) is a common secondary abnormality observed in Ewing sarcoma and related tumors [Sandberg and Bridge, 2000].
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AMERICAN JOURNAL OF MEDICAL GENETICS (SEMIN. MED. GENET.)
Figure 2. Schematic illustration of the t(11;22) characteristic of Ewing sarcoma
(top). Partial G-banded karyotype of the t(11;22)(q24;q12). See text for discussion
[Sandberg and Bridge, 2000].
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an NH-terminal transactivating region
(including a pointed domain encoded
largely by exon 4) that is partially
retained in some EWS-FLI1 fusions
and a COOH-terminal transactivating
domain. Exon 9 of the FLI1 gene encodes the highly conserved ETS-type
DNA binding domain. The EWS and
FLI1 transcripts shown in Figure 4 are
presented approximately to scale. Differences in the fusion products have
shown clinical significance, in that the
prognosis in Ewing sarcoma is different
for the type 1 versus the type 2 fusion
product of EWS-FLI1. The clinical
significance of the other fusion products
is unknown, owing to lack of data at this
time.
Molecular studies shown the involvement and changes in genes not necessarily involved in translocations. An example is the gene KIT in intestinal
stromal tumors, whose overexpression
or mutation or both is diagnostic of this
tumor. Most important, because of its
tyrosine kinase content, it is subject
to remarkable effects of drugs directed
against this kinase, for example, Gleevec,
PD17, and, possibly, other similar drugs
[Sandberg and Bridge, 2002]. An identical translocation as well as the molecular changes associated with this
translocation (Table I) have led to the
recognition that infantile fibrosarcoma
and congenital mesoblastic nephroma
Figure 3. Schematic diagram of the chimeric EWS-FLI1 protein product. NTD ¼ amino terminal domain; BD ¼ binding domain.
See text for discussion [Sandberg and Bridge, 2000].
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AMERICAN JOURNAL OF MEDICAL GENETICS (SEMIN. MED. GENET.)
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TABLE II. Bone and Soft-Tissue
Tumors Not Associated With
Specific Translocations
Chondrosarcomas
(except extraskeletal)
Osteosarcomas
Mesothelioma
Leiomyosarcomas
Fibrosarcoma (adult)
Malignant fibrous histiocytoma
Malignant peripheral nerve sheath
tumor
Figure 4. Upper part of the figure shows the structure of the EWS and FLI1 genes
with arrowheads indicating the breakpoints and fusion sites in the chimeric transcripts
resulting from the t(11;22)(q24;q12) in Ewing sarcoma. See text for discussion [Sandberg
and Bridge, 2000].
are tumors of identical genetic origin
and pathologic features. Without the
unique cytogenetic and molecular findings in these two tumors, it is doubtful
whether their common origin would
have been recognized. Another example
of tumors of quite different anatomic
location having the same genetic background is alveolar soft-part sarcoma and
some papillary renal cell carcinomas
(RCCs), which have an identical translocation, t(X;17)(p11.2;q25). Of significance is the balanced nature of
the t(X;17) in RCCs and the unbalanced nature of the translocation in alveolar soft-part sarcomas, leading to a
der(17)t(X;17) (p11.2;q25). The abnormal fusion genes in both types of tumors
are identical, that is, ASPL(RCC)-TFE3
[Argani et al., 2001; Sandberg and
Bridge, in press].
An identical translocation
as well as the molecular
changes associated with this
translocation (Table I) have
led to the recognition that
infantile fibrosarcoma and
congenital mesoblastic
nephroma are tumors of
identical genetic origin and
pathologic features.
Both tumors with specific translocations and those without (Table II)
have been shown to have numerous
cytogenetic and molecular changes. In
the case of the former tumors, this may
be indicative of biologic tumor progression; in the case of the latter tumors,
some of the changes may be primary and
causative, whereas others may be of a
secondary nature. In most of these tumors (without specific translocations),
the primary (causative) genes have not
been established. Also, the cytogenetic
and molecular changes vary from tumor
to tumor as well as in tumors of similar
origin.
The genetic findings in some of
these tumors are not dissimilar from the
pattern described in this issue for bladder
cancer [Sandberg, in press]. Thus, these
tumors are associated with a stepwise
process of orchestrated genetic changes
starting from excess cellular proliferation, malignant transformation, and
ultimately invasiveness and metastases.
These changes vary from tumor to
tumor, though some of the same genes
may be involved in several tumors.
Although translocations and other structural chromosome changes affecting
oncogenes may be part of this genetic
cascade of events in these tumors, most
of the genes affected are tumor suppressor genes containing allelic imbalances
leading to loss of heterozygosity. It
remains to be resolved what constitutes
the causative and original genetic event
and the order in which the subsequent
changes lead to overt cancer and
cancerous behavior. Although various
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chromosomes have been suggested as
being responsible for the initiation of
some of these tumors, rigorous evidence
has not been obtained for any of these
tumors. The establishment of the significant role of any genes in the stepwise
process of tumorigenesis of the neoplasms shown in Table II may serve
important diagnostic and, particularly,
prognostic and therapeutic purposes.
REFERENCES
Åman P. 1999. Fusion genes in solid tumors.
Cancer Biol 9:303–318.
Argani P, Antonescu CR, Illei PB, Lui MY,
Timmons CF, Newbury R, Reuter VE,
Garvin AJ, Perez-Atayde AR, Fletcher JA,
Beckwith JB, Bridge JA, Ladanyi M. 2001.
Primary renal neoplasms with the ASPL-
AMERICAN JOURNAL OF MEDICAL GENETICS (SEMIN. MED. GENET.)
TFE3 gene fusion of alveolar soft part
sarcoma: a distinctive tumor entity previously included among renal cell carcinomas
of children and adolescents. Am J Pathol
159:179–192.
Barr FG, Chatten J, D’Cruz CM, Wilson AE,
Nauta LE, Mycum LM, Biegel JA, Womer
RB. 1995. Molecular assays for chromosomal translocations in the diagnosis of pediatric soft tissue sarcomas. JAMA 273:553–
557.
Heimann P, El Housni H, Ogur G, Weterman
MAJ, Petty EM, Vassart G. 2001. Fusion of a
novel gene, RCC17, to the TFE3 gene in
t(X;17)(p11.2;q25.3)-bearing papillary renal
cell carcinomas. Cancer Res 61:4130–4135.
Ladanyi M, Bridge JA. 2000. Contribution of
molecular genetic data to the classification of
sarcomas. Hum Pathol 31:532–538.
Lin PP, Brody RI, Hamelin AC, Bradner JE,
Healey JH, Ladany M. 1999. Differential
transactivation by alternative EWS-FLI1
proteins correlates with clinical heterogeneity in Ewing’s sarcoma. Cancer Res
59:1428–1432.
193
Sandberg AA. 2002. The cytogenetics and
molecular genetics of bladder cancer: a
personal view. Am J Med Genet (Semin
Med Genet) (in press).
Sandberg AA, Bridge JA. 1994. The cytogenetics
of bone and soft tissue tumors. Austin: RG
Landes Co.
Sandberg AA, Bridge JA. 2001a. Updates on
the cytogenetics and molecular genetics of
bone and soft tissue tumors: clear cell
sarcoma (malignant melanoma of soft
parts). Cancer Genet Cytogenet 130:1–7.
Sandberg AA, Bridge JA. 2001b. Updates on
the cytogenetics and molecular genetics
of bone and soft tissue tumors: mesothelioma. Cancer Genet Cytogenet 127:93–
110.
Sandberg AA, Bridge JA. 2002. Updates on the
cytogenetics and molecular genetics of
bone and soft issue tumors: gastrointestinal
stromal tumors. Cancer Genet Cytogenet
(in press).
Sorensen PHB, Triche TJ. 1996. Gene fusions
encoding chimaeric transcription factors in
solid tumours. Cancer Biol 7:3–14.