Download Targeting survivin in cancer therapy: fulfilled

Carcinogenesis vol.28 no.6 pp.1133–1139, 2007
doi:10.1093/carcin/bgm047
Advance Access publication March 6, 2007
REVIEW
Targeting survivin in cancer therapy: fulfilled promises and open questions
Marzia Pennati, Marco Folini and Nadia Zaffaroni
Dipartimento di Oncologia Sperimentale, Fondazione IRCCS Istituto
Nazionale dei Tumori, Via Venezian 1, 20133 Milan, Italy
To whom correspondence should be addressed. Tel: þ39 02 23903260;
Fax: þ39 02 23903052;
Email: [email protected]
Survivin is a bifunctional protein that acts as a suppressor of
apoptosis and plays a central role in cell division. The protein is
strongly expressed in the most common human neoplasms, has
prognostic relevance for some of them and appears to be involved
in tumor cell resistance to anticancer agents and ionizing radiation. On the basis of these findings, survivin has been proposed as
an attractive target for new anticancer interventions. Several preclinical studies have demonstrated that down-regulation of survivin expression or function, accomplished by means of various
strategies, reduced tumor growth potential, increased the apoptotic rate and sensitized tumor cells to chemotherapeutic drugs and
radiation in different human tumor models. Moreover, the first
survivin inhibitors recently entered clinical trials. Recent studies
suggest a possible role for survivin in regulating the function of
normal adult cells. However, the expression and function of survivin in normal tissues are still not well characterized and understood. Better knowledge of the role of survivin in tumor
versus normal cells will be instrumental for the design of optimal
strategies to selectively disrupt survivin in cancer.
Introduction
The anti-apoptotic proteins that counteract signaling through specific
apoptosis pathways provide targets for possible drug discovery and
new anticancer interventions.
Two major pathways of apoptosis have been identified in mammalian cells. An extrinsic pathway is triggered by the binding of ligands to
cell-surface trimeric membrane death receptors and leads to caspase-8
activation (1). An intrinsic pathway involves mitochondria, which
respond to pro-apoptotic signals by releasing cytochrome c, which
in turn binds and activates the apoptotic protease-activating factor-1,
causing assembly of a multiprotein caspase-activating complex (apoptosome) and leading to activation of caspase-9 and initiation of a protease cascade (2). The intrinsic and extrinsic pathways for apoptosis
converge on downstream effector caspases. Some of these, such as
caspase-3 and caspase-7, are targets of suppression by an endogenous
family of anti-apoptotic proteins called inhibitor of apoptosis proteins
(IAPs), which also interfere with caspase-9 processing, the upstream
initiation of the mitochondrial pathway of apoptosis (3). The human
genome encodes eight IAP family members including X-linked
inhibitor of apoptosis protein (X-IAP), cIAP1, cIAP2, ML-IAP (Livin;
K-IAP), Naip, ILP2 (TS-IAP), Apollon/Bruce and survivin (4).
Structure and function of survivin
The human survivin gene spans 14.7 kb on the telomeric position of
chromosome 17 and is transcribed from a TATA-less, GC-rich promoter (5) to generate the wild-type transcript and four different splice
Abbreviations: AkT, v-akt murine thymoma viral oncogene homolog 1 or protein kinase B; CDK, cyclin-dependent kinase; HBX, hepatitis B virus X; Hsp90,
heat shock protein 90; IAP, inhibitor of apoptosis protein; IC, Inhibitor Concentration; IGF-1, insulin-like growth factor-1; NFjB, nuclear factor-j B; RNAi,
RNA interference; siRNA, small interfering RNA; STAT3, signal-transducerand-activator-of-transcription-3; Thr34 / Ala, Threonine 34 / alanine.
variant mRNAs (6). Survivin is a 16.5 kD protein of 142 amino acids
and is composed of a single baculovirus IAP repeat domain and an
extended C-terminal a-helical coiled-coil domain; it does not contain
the RING-finger domain found in other IAPs (7).
Growing evidence points to a functional role of survivin in both cell
division and apoptosis control (8). Survivin is a chromosomal passenger protein that localizes to kinetochores at metaphase, transfers to the
central spindle mid-zone at anaphase and accumulates in mid-bodies
at telophase (9). Physical interactions with the inner centromere protein, Aurora B (10,11) and Borealin/Dasra B (12) are required to
target the complex to the kinetochore, properly form the bipolar spindle and complete cytokinesis (10–12). Such a function of preservation
of genome fidelity and regulation of microtubule dynamics requires
a sharp cell-cycle-dependent transcription of the survivin gene during
the mitotic phase (13) as well as post-translational modifications of
the protein including phosphorylation by the p34cdc2 (14) and Aurora
B (15) kinases and monoubiquitination through Lys48 and Lys63 linkages (16). It has been recently suggested that this pathway is dominant
in normal cells and constitutes the primary function of survivin in adult
tissues (8,17). However, an up-regulation of survivin in G2/M cell
compartments has been observed in various cancer cell lines (18,19).
Other non-cell-cycle-dependent mechanisms driving survivin gene
transcription independent of mitosis have been described, which
involve tissue patterning circuits (Wnt/b-catenin) (20), cytokine
activation signal-transducer-and-activator-of-transcription-3 (21), costimulatory messages (OX-40) (22) and pleiotropic signaling mechanisms
[v-akt murine thymoma viral oncogene homolog 1 or protein kinase B
(AkT) and nuclear factor-j B] (23) that are operative during development and generally up-regulated in cancer cells (24) and can explain survivin over-expression in the large majority of human tumors.
It has been recently suggested that these non-cell-cycle-dependent
pathways are dominant in tumors. This hypothesis also relies on the
fact that a transgenic mouse model expressing the green fluorescent
protein reporter gene under the control of the minimal survivin promoter demonstrated that expression of survivin in development and
tumor formation is largely independent of cell-cycle-dependent transcription of the survivin gene at mitosis (25). The fraction of survivin
produced through these non-cell-cycle-dependent mechanisms mediates apoptosis inhibition through intermolecular cooperation with
cofactors including the hepatitis B virus X-interacting protein (26),
a target of the oncogenic viral hepatitis B virus X protein and X-IAP
(27), leading to the formation of complexes that inhibit caspase-9
processing. Moreover, subcellular compartmentalization of survivin
in mitochondria seems to play a role in the anti-apoptotic function of the
protein. Specifically, the existence of a mitochondrial pool of survivin
was recently reported, and it was found that in response to cell death
stimulation, mitochondrial survivin is rapidly discharged and released
into the cytosol, where it prevents caspase activation and inhibits apoptosis (28). In addition, survivin was not seen in mitochondria in normal tissues, suggesting that mitochondrial survivin is exclusively
associated with tumor transformation (28). A very recent study found
that survivin has a nuclear export signal and that in cancer cells the
anti-apoptotic and mitotic roles of survivin can be separated through
mutation of its nuclear export signal, which abrogates the cytoprotective activity of the protein but still allows mitosis to proceed (29).
A physical interaction with the molecular chaperone heat shock
protein 90 (Hsp90), which involves the Hsp90 ATPase domain and
the survivin baculovirus IAP repeat domain, was shown to be essential
for the stability and function of survivin. In fact, targeted antibodymediated disruption of the survivin–Hsp90 complex in cancer cells
resulted in proteasomal degradation of survivin, mitochondrialdependent apoptosis and mitotic arrest (30). A possible role of survivin
Ó The Author 2007. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
1133
M.Pennati et al.
in prolonging the cellular lifespan has been recently suggested considering that ectopic expression of survivin in colon cancer cells was
able to enhance telomerase activity through the up-regulation of Sp1and c-Myc-mediated transcription of the human telomerase reverse
transcriptase (hTERT) component of the enzyme (31).
Little is known about the functions of alternative splice forms of
survivin, which are generally expressed at lower levels than the wildtype survivin. Preliminary data suggest that heterodimerization of
wild-type survivin with survivin-DEx3 is essential for the inhibition
of mitochondrial-dependent apoptosis (32). It has also been demonstrated in exogenous expression assays that survivin-2a splice variant
attenuates the anti-apoptotic activity of wild-type survivin (33). More
recently, it was reported that despite their ability to interact with wildtype survivin, alternative splice isoforms such as survivin-DEx3 and
survivin-2b do not play a role in mitosis since they do not localize
with the chromosomal passenger complex in vivo as a consequence of
their reduced affinity for the survivin partner Borealin (34). Moreover,
these splice variants cannot rescue cell proliferation inhibited by RNA
interference (RNAi)-mediated survivin depletion (34).
Survivin expression in normal and tumor tissues
Survivin expression in normal tissues is developmentally regulated
and the protein was found to be absent or low in most terminally
differentiated tissues (5). However, recent studies tend to attribute
a role to survivin in regulating the function of normal adult cells
(35) including vascular endothelial cells (36), polymorphonuclear
cells (37), T cells (38), erythroid cells (39) and hematopoietic progenitor cells (40). Moreover, survivin expression was reported in adult
liver cells (41), gastrointestinal tract mucosa (42) and ovarian granulosa cells (43). However, although survivin is expressed in normal
tissues characterized by self-renewal and proliferation, its expression
is significantly lower than in transformed cells. In fact, several studies
have demonstrated strong survivin expression in most human solid
tumor types and hematologic malignancies (44). Expression of survivin has also been detected in a variety of benign and preneoplastic
lesions including melanocytic nevi (45,46), polyps of the colon, breast
adenomas, Bowen’s disease and hypertrophic actinic keratosis (44),
suggesting that re-expression of survivin may occur early during malignant transformation or following a disturbance in the balance between cell proliferation and cell death. The up-regulation of survivin
at the transcriptional level in human tumors has been confirmed in
genome-wide searches, which indicated survivin as the fourth top
‘‘transcriptome’’ in cancers of various histology (47). Moreover,
global deregulation of the survivin gene mediated by oncogenes such
as signal-transducer-and-activator-of-transcription-3 (21), E2F (48)
and activated H-Ras (49,50) or by loss of tumor suppressors like
wild-type p53 (51) or the adenomatous polyposis coli protein (52)
seems to be responsible for the enhanced expression of survivin in
tumors.
Growing evidence suggests that survivin expression in cancer cells
is associated with clinicopathologic variables of aggressive disease
and may represent an important prognostic marker for patient outcome. In fact, several studies on different types of solid tumors and
hematologic malignancies showed that high levels of the protein were
predictive of tumor progression in terms of either disease-free or
overall survival (44). In several neoplasms, the association with tumor
progression was corroborated in the context of a comprehensive analysis of gene-expression profiling by DNA microarray or polymerase
chain reaction-based assay. As it is possible to immunohistochemically distinguish two intracellular pools of survivin, a nuclear and
a cytosolic one, the prognostic significance of the protein has been
analyzed in some studies as a function of its intracellular localization,
and inconsistent and sometimes contrasting results have been obtained regarding the prognostic value of nuclear survivin expression
(53). The different prognostic value of survivin may reflect differences in methods to detect its expression and/or a differential expression of survivin splice variants. For instance, expression of the
1134
2b variant, which does not seem to have anti-apoptotic activity, was
found to predominate in neuroblastomas with a good prognosis (54).
Survivin as a determinant of treatment resistance
There is evidence that survivin plays an important role in the drugresistant phenotype of human cancer cells. Giodini et al. (55) first
reported that infection of HeLa cells with an adenoviral vector expressing survivin suppressed apoptosis induced by taxol. Successively, we found that stable transfection of OAW42 and IGROV-1
human ovarian cancer cell lines with survivin cDNA was able to
protect the cells from the cytotoxic effects induced by taxol and
taxotere, with IC50 values for the survivin-transfectant cell populations 4- to 6-fold those of control cells (56). Zhang et al. (57) showed
that forced expression of wild-type survivin in human prostate cancer
cell lines increased the resistance to taxol in vitro and in vivo. In the
clinical setting, when we analyzed the response of 95 patients with
advanced ovarian cancer to a taxol-based regimen as a function of
survivin expression, we found significantly higher clinical or pathologic response rates in cases with absent or low protein expression
than in those expressing high levels of survivin (56).
It has been reported that taxol-induced microtubule stabilization
and mitotic arrest increase the expression of survivin, which engenders a cell survival pathway to counteract taxol-induced apoptosis
(58). Interestingly, using a taxol-resistant ovarian cancer cell clone,
PTX10, with a b-tubulin mutation at the taxol-binding site, Zhou et al.
(59) found that taxol treatment failed to induce mitotic arrest and
survivin expression. However, the finding that taxol induced an apoptotic response in these cells suggests that mitotic arrest is not strictly
required for taxol-induced apoptosis. It is also possible that the mitotic survival pathway is not the only one by which cancer cells
counteract taxol-induced apoptosis. In fact, Ling et al. (60) recently
reported that induction of survivin by taxol in MCF-7 cells is an early
event and is independent of taxol-mediated G2/M arrest, suggesting
a role for survivin in taxol resistance not only during mitosis but also
outside of the mitotic checkpoint. There is evidence that the mammalian target of rapamycin pathway, which constitutes a sensor network
for stress conditions, is involved in resistance to taxol by increasing
survivin levels (61). In fact, it has been recently reported that insulinlike growth factor-1-mediated mammalian target of rapamycin activation in prostate cancer cells positively modulated survivin levels by
favoring stabilization and translation of a survivin mRNA pool and
that mammalian target of rapamycin inhibition with rapamycin, alone
or in combination with taxol, abolished survivin increase. Consistent
with a critical reduction of the anti-apoptotic threshold maintained by
survivin, the taxol plus rapamycin combination was more effective
than either treatment in reducing cell viability in the presence of
insulin-like growth factor-1 (61).
An increase in survivin expression has also been reported in prostate cancer (62) and thyroid cancer (63) cell lines permanently resistant to cisplatin as well as in colorectal cancer cells resistant to
tumor necrosis factor-related apoptosis-inducing ligand (64). Zhang
et al. (65) showed that survivin mediates resistance to anti-androgen
therapy with flutamide in prostate cancer cells. Specifically, these
authors suggested that up-regulation of survivin via insulin-like
growth factor-1/AkT signaling during androgen blockade may be
one of the mechanisms by which prostate cancer cells develop resistance to anti-androgens. Paik et al. (66) showed that survivin was
one of the sixteen genes predictive of recurrence in tamoxifen-treated
breast cancer patients.
Regarding the role of survivin in determining the response of human tumor cells to radiation, Asanuma et al. (67) first reported that
survivin acts as a constitutive radioresistance factor in pancreatic
cancer cells. Specifically, in a panel of established cell lines, they
found an inverse relationship between survivin mRNA expression
and in vitro sensitivity to X-irradiation. Moreover, they demonstrated
that survivin mRNA expression was increased by sublethal doses of
X-irradiation, which would suggest that the protein also acts as an
inducible radioresistance factor. Rodel et al. (68) also showed an
Targeting survivin in cancer therapy
inverse correlation between survivin expression and apoptotic response
to irradiation in a panel of colorectal carcinoma cell lines. More recently, in a translational study of 59 rectal cancer patients treated with
a combination of radiotherapy and chemotherapy, the same authors
reported that increased survivin expression was associated with a significantly increased risk of local tumor recurrence (69). It is worthy of
note that survivin can contribute to radiation resistance also by promoting the survival of tumor vascular endothelial cells. In fact, induction of vascular endothelial apoptosis was recently shown to be
a major determinant of overall tumor response to radiotherapy (70).
Radiation may induce tumor cells to secrete cytokines such as vascular endothelial growth factor, which in turn could inhibit radiationinduced apoptosis of vascular endothelial cells by up-regulating
survivin expression, as already demonstrated for drug-induced
apoptosis (71).
Survivin-directed cancer therapy
In recent years, considerable efforts have been made to validate survivin as a new target in cancer therapy. In this context, a collection of
different approaches to counteract survivin in tumor cells (Figure 1)
have been proposed with the dual aim to inhibit tumor growth potential and to enhance tumor cell response to apoptosis-inducing anticancer agents.
Molecular antagonists
Anti-sense oligonucleotides
Grossman et al. (73) first demonstrated that transfection of survivin
anti-sense triggered spontaneous apoptosis in the absence of other
stimuli in YUSAC2 and LOX human melanoma cell lines. Successively, several studies dealing with the use of survivin anti-sense
Fig. 1. A schematic representation of the different strategies to target
survivin in cancer therapy: (A) Molecular antagonists able to target survivin
mRNA and inhibit translation; (B) Dominant-negative mutants able to inhibit
survivin dimerization (Ala84) or survivin activation through phosphorylation
of Thr34 residue (Ala34); (C) Small molecule antagonists able to inhibit
survivin phosphorylation on Thr34 residue (CDK inhibitors) or to counteract
survivin–Hsp90 interaction (Hsp90 inhibitors); (D) Survivin-directed
immunotherapy approaches. In (B–D), the wild-type protein is reported in its
dimeric arrangement (72).
oligonucleotides, delivered to the cells as chemically synthesized
molecules or through the use of expression vectors, consistently
showed that specific inhibition of survivin mRNA and protein could
reduce cell proliferation and induce caspase-dependent apoptosis in
established cell lines of different tumor origins including lung, bladder, head and neck and thyroid cancers, sarcomas and lymphomas
(74–78). Moreover, down-regulation of survivin was shown to sensitize human tumor cells to cytotoxic drugs such as etoposide and
cisplatin (75), as well as ionizing radiation (79). Anti-sense-mediated
survivin knock-down also caused inhibition of tumor growth in xenograft models (74,78) and sensitized lung cancer xenografts to
radiotherapy (74). Kanwar et al. (80) demonstrated that survivin inhibition resulted in increased sensitivity to immunotherapy in murine
EL-4 thymic lymphoma. Specifically, tumors injected with plasmids encoding survivin anti-sense were significantly inhibited in their
growth. Such growth delay was further enhanced by concomitant injection of the T-cell costimulator B7-1.
Supported by a favorable safety profile, the first anti-sense oligonucleotide, LY2181308 (ISIS 23722; Lilly and Co., Indianapolis, IN
and ISIS Pharmaceuticals, Carlsbad, CA, US), already entered the
clinic and is currently undergoing phase I trials in patients with advanced cancers.
Hammerhead ribozymes
As an alternative anti-sense strategy for survivin inhibition, we developed in our laboratory two hammerhead ribozymes targeting the 3#
end of the CUA110 (RZ7) and the GUC294 (RZ1) triplets in the survivin mRNA and transfected them into the JR8 human melanoma cell
line over-expressing survivin. Stably transfected clones proven to
endogenously express the active ribozyme RZ1 or RZ7 were characterized by a markedly lower survivin protein level than JR8 parental
cells, and showed an increased caspase-9-dependent apoptotic response to treatment with the cytotoxic agents cisplatin (81) and topotecan (82) as well as with c-irradiation (83). Moreover, an increased
antitumor activity of oral topotecan was observed in ribozymeexpressing JR8 cells grown as xenograft tumors in athymic nude mice
(82). In addition, we constructed a Moloney-based retroviral vector
expressing the RZ7 ribozyme, encoded as a chimeric RNA within
adenoviral VA1 RNA. Polyclonal cell populations, obtained by infection with the retroviral vector, of two androgen-independent human prostate cancer cell lines (DU145 and PC-3) were characterized
by a significant reduction of survivin expression; the cells became
polyploid, underwent caspase-9-dependent apoptosis and showed an
altered pattern of gene expression, as detected by oligonucleotide
array analysis. Survivin inhibition also enhanced the susceptibility
of these cells to cisplatin-induced apoptosis and prevented tumor
formation when cells were xenografted into athymic nude mice
(84). Choi et al. (85) also showed that two hammerhead ribozymes,
able to cleave the human survivin mRNA at nucleotide position þ279
and þ28 and cloned into a replication-deficient adenoviral vector,
increased the apoptotic response to etoposide in transduced MCF-7
breast cancer cells.
Small interfering RNAs
The discovery that synthetic 21–23 nucleotide RNA duplexes can
trigger an RNAi response in mammalian cells and induce strong inhibition of specific gene expression has opened the door to the therapeutic use of small interfering RNAs (siRNAs) (86). Carvalho et al.
(87) first used RNAi to specifically repress survivin in HeLa cells.
These authors showed that survivin was no longer detectable in
cultures 60 h after transfection with specific siRNAs and that
survivin-depleted cells were delayed in mitosis and accumulated in
prometaphase with misaligned chromosomes. Several studies dealing
with the use of chemically synthesized siRNAs or plasmid/viral vectors encoding short hairpin RNAs showed that RNAi-mediated survivin knock-down was able to reduce tumor cell proliferative potential
and induce caspase-dependent apoptosis in a variety of human tumor
cell models (17,88–93), as well as to decrease the formation of new
1135
M.Pennati et al.
tumors and the growth of already established lesions in nude mice
(93,94). Survivin down-regulation also induced an enhanced apoptotic response of tumor cells of different histologic origin to several
stimuli, including treatment with vincristine (93), doxorubicin (94,95),
17-allylamino-17-demethoxygeldanamycin (89), tumor necrosis factoralpha (94) and APO2 ligand/tumor necrosis factor-related apoptosisinducing ligand (90), and caused radiosensitization of a sarcoma cell
line expressing wild-type p53 (96). Finally, Coma et al. (97) demonstrated that transfection of endothelial cells with survivin-specific
siRNAs induced a marked increase in the rate of apoptosis, a dosedependent inhibition of their migration on vitronectin, and a decrease
in capillary formation.
Gene therapy
Two main gene therapy approaches targeting survivin have been successfully developed. One is based on the use of plasmids or viral
vectors to deliver dominant-negative survivin mutants to tumor cells.
Grossman et al. (73) first demonstrated that transfection of YUSAC2
and LOX melanoma cell lines with a mutant carrying a cysteine 84 /
alanine (Cys84Ala) mutation in the survivin baculovirus IAP repeat
domain increased the apoptotic index and enhanced the sub-G1 apoptotic cell fraction in both tumor models. More recently, Tu et al. (98)
showed that adeno-associated viral vector-mediated transfer of the
survivin mutant Cys84Ala induced apoptosis and mitotic catastrophe
in colon cancer cells, inhibited angiogenesis and tumor growth in
a colon cancer xenograft model in vivo and strongly enhanced the
antitumor activity of 5-fluorouracil. By using a phosphorylationdefective survivin threonine 34 / alanine (Thr34 / Ala) mutant,
Grossman et al. (99) demonstrated the induction of spontaneous apoptosis in different melanoma cell lines as well as an increased apoptotic response following cisplatin treatment. Conditional expression
of Thr34 / Ala in these cells prevented tumor formation upon subcutaneous injection in 13 of 15 CB.17 severely combined immunodeficient mice. Such treatment also caused a significant reduction
(60–70%) in the growth rate of already established tumors and enhancement of apoptosis (99). Mesri et al. (100) investigated the effect
of a replication-deficient adenovirus encoding the survivin Thr34 /
Ala dominant-negative mutant (pAd-T34A) in human tumor cells of
various origin in vitro and in vivo. They showed that infection with
pAd-T34A caused enhanced spontaneous and taxol-induced apoptosis
in cell lines of different tumor origin while not affecting the growth of
proliferating normal human cells not expressing survivin. In vivo experiments on the MCF-7 human breast cancer xenograft model demonstrated that pAd-T34A was able to suppress de novo tumor
formation, inhibit the growth of already established tumors by
40% and reduce intra-peritoneal tumor dissemination. Moreover,
tumors infected with pAd-T34A showed massive apoptosis and loss
of proliferating cells. Very recently, using a recombinant fusion protein containing the TAT transduction domain and the Thr34 / Ala
dominant-negative mutant (TAT-Surv-T34A), Yan et al. (101) observed an induction of caspase-dependent apoptosis in melanoma
cells. Moreover, repeated intra-peritoneal injection of TAT-SurvT34A resulted in a marked reduction of the growth and mass of
established subcutaneous tumors in mice.
The second gene therapy approach involves the use of the survivin
gene promoter to drive the expression of cytotoxic genes in tumor
cells (102). It was shown that when coupled to the pro-apoptotic
protein Bik, administration of the suicidal construct as a DNA–
liposome formulation suppressed the growth of human lung cancer
in vitro and in vivo (103). Van Houdt et al. (104) showed recently
that survivin promoter-based conditionally replicative adenoviruses
(CRAds), composed of survivin promoter-regulated E1 gene expression and an RGD-4C capsid modification, efficiently replicated
within and killed a variety of established glioma cell lines but were
inactive in a normal liver culture. Moreover, survivin promoterbased CRAds significantly inhibited the growth of glioma xenografts
in vivo.
1136
Small molecule antagonists
Cyclin-dependent kinase inhibitors
In the context of a strategy focused on pharmacologic inhibition of
mitotic phosphorylation of survivin on Thr34 to accelerate protein
destruction and counteract its function (58), cyclin-dependent kinase
(CDK) inhibitors such as flavopiridol or the more p34cdc2-specific
inhibitor, purvalanol A, were tested in tumor cells arrested at mitosis
with taxol, which induces hyperphosphorylation of survivin on Thr34
(56). Sequential administration of CDK inhibitors resulted in escape
from the mitotic block imposed by taxol, marked activation of
mitochondrial-dependent apoptosis and anticancer activity in vivo
(58). More recently, inhibition of survivin phosphorylation and expression was also suggested to be the potential mechanism by which
the novel CDK inhibitor NU6140 (4-(6-cyclohexylmethoxy-9Hpurin-2-ylamino)-N,N-diethyl-benzamide) potentiates taxol-induced
apoptosis in HeLa cells (105).
Hsp90 inhibitors
A structure-based rational screening for antagonists of the survivin–
Hsp90 complex identified a cell-permeable peptidomimetic derived
from the survivin sequence Lys79–Leu87, shepherdin (106). In addition to counteracting survivin–Hsp90 interaction, the molecule inhibited Hsp90 chaperone function by competing with ATP binding.
Specifically, shepherdin was able to destabilize several Hsp90 client
proteins (including AkT, CDK6 and telomerase) and to induce cell
death via apoptotic and non-apoptotic mechanisms in cell lines of
different tumor types. The cytotoxicity of shepherdin was seen to
be independent of the proliferative activity of the cell model, concomitant over-expression of other cytoprotective factors such as Bcl-2 and
p53 status. Moreover, shepherdin appeared to be selective in its antitumor activity since it did not affect viability of normal cells or tissues, including hematopoietic progenitors. Systemic administration of
shepherdin in vivo was safe and well tolerated and inhibited the
growth of already established prostate and breast cancers without inducing systemic or organ toxicity. Moreover, immunohistochemical
analysis of Hsp90 client proteins carried out in tumor samples at the
end of shepherdin treatment showed a nearly complete loss of Akt
levels and severely attenuated survivin expression (106). The clinical
development of shepherdin with respect to its optimal formulation and
pharmacokinetic profile is currently under way through the National
Cancer Institute Rapid Access to Intervention Development program.
Since the shepherdin residues between Lys79 and Gly83 were shown
to be essential for Hsp90 binding, a new five-residue peptide containing the Lys79–Gly83 sequence (called shepherdin[79–83]) was successively synthesized (107). The oligopeptide inhibited the formation of
the survivin–Hsp90 complex and competed with ATP binding to
Hsp90. Cell-permeable shepherdin[79–83] induced rapid killing in
different types of human acute myeloid leukemia cell lines and
in patient-derived acute myeloid leukemia peripheral blasts but not
in normal mononuclear cells. Moreover, when systemically delivered,
shepherdin[79–83] abolished the growth of acute myeloid leukemia
xenograft tumors without systemic or organ toxicity (107). We have
recently used shepherdin as a scaffold to rationally identify lowmolecular weight compounds that may act as structurally novel
Hsp90 inhibitors. Through a combined structure- and dynamics-based
computational design strategy, the non-peptidic small molecule 5aminoimidazole-4-carboxamide-1-b-D-ribofuranoside (AICAR) was
selected to bind the Hsp90 N-terminal domain, mimicking the chemical and conformational properties of shepherdin. AICAR was shown
to destabilize several Hsp90 client proteins in vivo, including survivin,
and to exhibit anti-proliferative and pro-apoptotic activities in multiple tumor cell lines while not affecting proliferation of normal human
fibroblasts (108).
Other small molecules
Additional small molecules that target survivin have been developed
and some of them are currently being evaluated in clinical trials. One
Targeting survivin in cancer therapy
of those that directly affect survivin expression, tetra-O-methyl nordihydroguaiaretic acid (M(4)N), was shown to suppress Sp1dependent survivin gene transcription and activate the mitochondrial
apoptotic pathway in transformed cells (109). Moreover, M(4)N suppressed the growth of human xenograft tumors following systemic
treatment (110). However, considering that the compound is a global
transcription inhibitor, both survivin-dependent and survivin-independent
pathways are thought to be responsible for drug-induced cell death in
tumors (111).
YM155 is a small molecule that selectively inhibits survivin gene
transcription and protein expression in several tumor cell lines. It
showed marked anti-proliferative activity (in the nanomolar range)
in a broad spectrum of human tumor cell lines and induced tumor
regression in lymphoma, prostate cancer and non-small cell lung
cancer xenografts (112). Moreover, preliminary evidence of the clinical activity of the compound was derived from a phase I open-label
study in which 41 patients with different tumor types were treated
with 7-day continuous intravenous infusion of YM155 and objective
responses were observed in three patients with non-Hodgkin’s lymphoma (112). The compound is currently being evaluated in a phase II
study for patients with stage III and stage IV melanoma.
Other small molecules currently in the clinic were shown to indirectly affect survivin expression. Some of them, including signaltransducer-and-activator-of-transcription-3 (113) and T-cell factor (114)
antagonists, caused the suppression of survivin gene transcription,
whereas others, such as the ErbB2 antagonist lapatinib (115), markedly inhibited survivin expression by acting at the post-translational
level through the promotion of the ubiquitin-proteasome-mediated
degradation of the protein (115).
Cancer vaccines and immunotherapy
The immunologic properties of survivin that have been discovered
indicate that the protein is also an attractive target for novel immunotherapies against cancer (116). Specifically, the immunogenicity of
survivin has been demonstrated in humans in vivo (clinical level) as
well as ex vivo by the detection of human survivin-reactive antibodies
(117) and cytolytic T-cell clones restricted to several haplotypes
(118–120). In a preclinical model of non-small cell lung carcinoma,
an orally delivered DNA vaccine encoding the secretory chemokine
CCL21 and survivin elicited marked activation of antigen-presenting
dendritic cells and an effective CD8þ T-cell immune response, which
resulted in suppression of pulmonary metastases, also as a consequence of inhibition of tumor-associated angiogenesis, without inducing toxicity (121). Survivin-directed immunotherapeutic approaches
have been quickly moved to the clinical setting: several phase I trials
based on the administration of survivin-directed autologous cytotoxic
T lymphocytes generated ex vivo or survivin peptides (122,123) have
been completed recently and the treatment was proved to be safe and
devoid of significant adverse effects. On account of these encouraging
results, some of these protocols have already moved on to clinical
phase II studies.
Conclusions
Results from studies exploiting different strategies to interfere with
survivin expression and function provided direct and convincing
evidence that targeting the survivin network inhibits tumor growth potential in vitro and in vivo and increases spontaneous and treatmentinduced apoptosis of cancer cells, thus indicating survivin as a
promising molecular target for cancer therapy. The applicability of
survivin-targeted strategies for the clinical treatment of human tumors
is currently under investigation as the first survivin inhibitors recently
entered phase I–II clinical trials. Although the results of these trials
are not yet available, survivin inhibitors may represent a novel type of
targeted drugs inasmuch as they specifically interfere with defined
molecular pathways of tumor cell maintenance and at the same time
are applicable to different tumor types independent of their genetic
makeup.
Although the anti-survivin therapies developed thus far have not
shown any major systemic toxicity in in vivo experimental models and
appear to be extremely promising, the possibility that survivin disruption could affect normal cell function, mainly the hematopoietic and
immune systems, cannot be excluded. In this context, a better understanding of the effects exerted by survivin on normal versus
malignant cells will be important in identifying strategies that maximally disrupt survivin in cancer cells while minimally affecting normal tissues. Moreover, in accord with the more recent view suggesting
that the two main functions of survivin, i.e. spindle monitoring at
mitosis and the ability to counteract apoptosis mainly through caspase
inhibition, are differentially exploited in normal and tumor cells, the
identification of points at which these functions can be separated
could open new possibilities for strategies aimed at eliminating cancer
cells while preserving normal cell viability.
Acknowledgements
The work in the authors’ laboratory was in part supported by grants from
the Italian Association for Cancer Research, the Italian Health Ministry and
Monzino Foundation.
Conflict of Interest Statement: None declared.
References
1. Yuan,J. (1997) Transducing signals of life and death. Curr. Opin. Cell
Biol., 9, 247–251.
2. Cryns,V. et al. (1999) Proteases to die for. Genes Dev., 12, 1551–1570.
3. Deveraux,Q.L. et al. (1999) IAP family proteins—suppressors of apoptosis. Genes Dev., 13, 239–252.
4. Reed,J.C. et al. (2004) The domains of apoptosis: a genomics perspective
[RE9]. Sci. STKE, 239, 1–29.
5. Ambrosini,G. et al. (1997) A novel anti-apoptosis gene, survivin, expressed in cancer and lymphoma. Nat. Med., 3, 917–921.
6. Li,F. et al. (2006) Survivin study: an update of ‘‘what is the next wave?’’.
J. Cell Physiol., 208, 476–486.
7. LaCasse,E.C. et al. (1998) The inhibitors of apoptosis (IAPs) and their
emerging role in cancer. Oncogene, 17, 3247–3259.
8. Altieri,D.C. (2006) The case for survivin as a regulator of microtubule
dynamics and cell-death decisions. Curr. Opin. Cell Biol., 18, 1–7.
9. Vagnarelli,P. et al. (2004) Chromosomal passengers: the four-dimensional
regulation of mitotic events. Chromosoma, 113, 211–222.
10. Honda,R. et al. (2003) Exploring the functional interactions between aurora
B, INCENP, and survivin in mitosis. Mol. Biol. Cell, 14, 3325–3341.
11. Wheatley,S.P. et al. (2001) INCENP is required for proper targeting of
survivin to the centromeres and the anaphase spindle during mitosis. Curr.
Biol., 11, 886–890.
12. Gassmann,R. et al. (2004) Borealin: a novel chromosomal passenger
required for stability of the bipolar mitotic spindle. J. Cell Biol., 166,
179–191.
13. Li,F. et al. (1998) Control of apoptosis and mitotic spindle checkpoint by
survivin. Nature, 396, 580–584.
14. O’Connor,D.S. et al. (2000) Regulation of apoptosis at cell division by
p34cdc2 phosphorylation of surviving. Proc. Natl Acad. Sci. USA, 97,
13103–13107.
15. Wheatley,S.P. et al. (2004) Aurora-B phosphorylation in vitro identifies
a residue of survivin that is essential for its localization and binding
to inner centromere protein (INCENP) in vivo. J. Biol. Chem., 279,
5655–5660.
16. Vong,Q.P. et al. (2005) Chromosome alignment and segregation regulated
by ubiquitination of survivin. Science, 310, 1499–1504.
17. Yang,D. et al. (2004) Cell division and cell survival in the absence of
surviving. Proc. Natl Acad. Sci. USA, 101, 15100–15105.
18. Li,F. et al. (1998) Control of apoptosis and mitotic spindle checkpoint by
survivin. Nature, 396, 580–584.
19. Li,F. et al. (1999) The cancer antiapoptosis mouse survivin gene: characterization of locus and transcriptional requirements of basal and cell cycledependent expression. Cancer Res., 59, 3143–3151.
20. Kim,P.J. et al. (2003) Survivin and molecular pathogenesis of colorectal
cancer. Lancet, 362, 205–209.
1137
M.Pennati et al.
21. Gritsko,T. et al. (2006) Persistent activation of stat3 signaling induces
survivin gene expression and confers resistance to apoptosis in human
breast cancer cells. Clin. Cancer Res., 12, 11–19.
22. Song,J. et al. (2005) Sustained survivin expression from OX40
costimulatory signals drives T cell clonal expansion. Immunity, 22,
621–631.
23. Mitsiades,C.S. et al. (2002) Activation of NF-kB and upregulation
of intracellular anti-apoptotic proteins via the IGF-1/Akt signaling in
human multiple myeloma cells: therapeutic implications. Oncogene, 21,
5673–5683.
24. Vogelstein,B. et al. (2004) Cancer genes and the pathways they control.
Nat. Med., 10, 789–799.
25. Xia,F. et al. (2006) Mitosis-independent survivin gene expression in vivo
and regulation by p53. Cancer Res., 66, 3392–3395.
26. Marusawa,H. et al. (2003) HBXIP functions as a cofactor of survivin in
apoptosis suppression. EMBO J., 22, 2729–2740.
27. Dohi,T. et al. (2004) An IAP-IAP complex inhibits apoptosis. J. Biol.
Chem., 279, 34087–34090.
28. Dohi,T. et al. (2004) Mitochondrial survivin inhibits apoptosis and
promotes tumorigenesis. J. Clin. Invest., 114, 1117–1127.
29. Colnaghi,R. et al. (2006) Separating the anti-apoptotic and mitotic roles of
survivin. J. Biol. Chem., 281, 33450–33456.
30. Fortugno,P. et al. (2003) Regulation of survivin function by Hsp90. Proc.
Natl Acad. Sci. USA, 100, 13791–13796.
31. Endoh,T. et al. (2005) Survivin enhances telomerase activity via upregulation of specificity protein 1-and c-Myc-mediated human telomerase
reverse transcriptase gene transcription. Exp. Cell Res., 305, 300–311.
32. Caldas,H. et al. (2005) Survivin splice variants regulate the balance
between proliferation and cell death. Oncogene, 24, 1994–2007.
33. Caldas,H. et al. (2005) Survivin 2alpha: a novel survivin splice variant
expressed in human malignancies. Mol. Cancer, 4, 11.
34. Noton,E.A. et al. (2006) Molecular analysis of survivin isoforms:
evidence that alternatively spliced variants do not play a role in mitosis.
J. Biol. Chem., 281, 1286–1295.
35. Fukuda,S. et al. (2006) Survivin, a cancer target with an emerging role in
normal adult tissues. Mol. Cancer Ther., 5, 1087–1098.
36. Mesri,M. et al. (2001) Suppression of vascular endothelial growth factormediated endothelial cell protection by survivin targeting. Am. J. Pathol.,
158, 1757–1765.
37. Altznauer,F. et al. (2004) Inflammation-associated cell cycle-independent
block of apoptosis by survivin in terminally differentiated neutrophils.
J. Exp. Med., 199, 1343–1354.
38. Xing,Z. et al. (2004) Essential role of survivin, an inhibitor of apoptosis
protein, in T cell development, maturation, and homeostasis. J. Exp. Med.,
199, 69–80.
39. Gurbuxani,S. et al. (2005) Differential requirements for survivin in hematopoietic cell development. Proc. Natl Acad. Sci. USA, 102, 11480–11485.
40. Fukuda,S. et al. (2001) Regulation of the inhibitor-of-apoptosis family
member survivin in normal cord blood and bone marrow CD34(þ) cells
by hematopoietic growth factors: implication of survivin expression in
normal hematopoiesis. Blood, 98, 2091–2100.
41. Deguchi,M. et al. (2002) Expression of survivin during liver regeneration.
Biochem. Biophys. Res. Commun., 297, 59–64.
42. Chiou,S.K. et al. (2003) Survivin expression in the stomach: implications
for mucosal integrity and protection. Biochem. Biophys. Res. Commun.,
305, 374–379.
43. Wang,Y. et al. (2004) Survivin expression in rat testis is up-regulated by
stem-cell factor. Mol. Cell Endocrinol., 218, 165–174.
44. Altieri,D.C. (2003) Survivin, versatile modulation of cell division and
apoptosis in cancer. Oncogene, 22, 8581–8589.
45. Florrel,S.R. et al. (2005) Proliferation, apoptosis, and survivin expression
in a spectrum of melanocytic nevi. J. Cutan. Pathol., 32, 45–49.
46. Vetter,C.S. et al. (2005) Cytoplasmic and nuclear expression of survivin in
melanocytic skin lesions. Arch. Dermatol. Res., 297, 26–30.
47. Velculescu,V.E. et al. (1999) Analysis of human transcriptomes. Nat.
Gen., 23, 387–388.
48. Jiang,Y. et al. (2004) Aberrant regulation of survivin by the RB/E2F
family of proteins. J. Biol. Chem., 279, 40511–40520.
49. Sommer,K.W. et al. (2003) Inhibitor of apoptosis protein (IAP) survivin is
up-regulated by oncogenic c-H-Ras. Oncogene, 22, 4266–4280.
50. Fukuda,S. et al. (2004) Activated H-Ras regulates hematopoietic cell
survival by modulating survivin. Biochem. Biophys. Res. Commun.,
323, 636–644.
51. Hoffman,W.H. et al. (2002) Transcriptional repression of the
anti-apoptotic survivin gene by wild type p53. J. Biol. Chem., 277,
3247–3257.
1138
52. Zhang,T. et al. (2001) Evidence that APC regulates survivin expression:
a possible mechanism contributing to the stem cell origin of colon cancer.
Cancer Res., 61, 8664–8667.
53. Fengzhi,L. et al. (2005) Nuclear or cytoplasmic expression of survivin:
what is the significance? Int. J. Cancer, 114, 509–512.
54. Islam,A. et al. (2000) Role of survivin, whose gene is mapped to 17q25, in
human neuroblastoma and identification of a novel dominant-negative
isoform, survivin-b/2B. Med. Pediatr. Oncol., 35, 550–553.
55. Giodini,A. et al. (2002) Regulation of microtubule stability and mitotic
progression by survivin. Cancer Res., 62, 2462–2467.
56. Zaffaroni,N. et al. (2002) Expression of the anti-apoptotic gene survivin
correlates with taxol resistance in human ovarian cancer. Cell Mol. Life
Sci., 59, 1406–1412.
57. Zhang,M. et al. (2005) Adenovirus-mediated inhibition of survivin expression sensitizes human prostate cancer cells to paclitaxel in vitro and in
vivo. Prostate, 64, 293–302.
58. O’Connor,D.S. et al. (2002) A p34(cdc2) survival checkpoint in cancer.
Cancer Cell, 2, 43–54.
59. Zhou,J. et al. (2004) Survivin deregulation in beta-tubulin mutant ovarian
cancer cells underlies their compromised mitotic response to taxol. Cancer Res., 64, 8708–8714.
60. Ling,X. et al. (2004) Induction of survivin expression by taxol (paclitaxel)
is an early event, which is independent of taxol-mediated G2/M arrest.
J. Biol. Chem., 279, 15196–15203.
61. Vaira,V. et al. (2006) Regulation of survivin expression by IGF-1/mTOR
signalling. Oncogene advance online publication, 30 oct 2006 (doi:
10.1038/sj.onc.1210094).
62. Nomura,T. et al. (2005) Expression of the inhibitors of apoptosis proteins
in cisplatin-resistant prostate cancer cells. Oncol. Rep., 14, 993–997.
63. Tirro,E. et al. (2006) Altered expression of c-IAP1, survivin, and Smac
contributes to chemotherapy resistance in thyroid cancer cells. Cancer
Res., 66, 4263–4272.
64. Van Geelen,C.M. et al. (2004) Lessons from TRAIL-resistance
mechanisms in colorectal cancer cells: paving the road to patient-tailored
therapy. Drug Resist. Updat., 7, 345–358.
65. Zhang,M. et al. (2005) Survivin mediates resistance to antiandrogen therapy in prostate cancer. Oncogene, 24, 2474–2482.
66. Paik,S. et al. (2004) A multigene assay to predict recurrence of tamoxifentreated, node-negative breast cancer. N. Engl. J. Med., 351, 2817–2826.
67. Asanuma,K. et al. (2000) Survivin as a radio-resistance factor in pancreatic cancer. Jpn. J. Cancer Res., 91, 1204–1209.
68. Rodel,C. et al. (2003) Spontaneous and radiation-induced apoptosis
in colorectal carcinoma cells with different intrinsic radiosensitivities:
survivin as a radioresistance factor. Int. J. Radiat. Oncol. Biol. Phys.,
55, 1341–1347.
69. Rodel,F. et al. (2005) Survivin as a radioresistance factor, and prognostic
and therapeutic target for radiotherapy in rectal cancer. Cancer Res., 65,
4881–4887.
70. Garcia-Barros,M. et al. (2003) Tumor response to radiotherapy regulated
by endothelial cell apoptosis. Science, 300, 1155–1159.
71. Tran,J. et al. (2002) a role for survivin in chemoresistance of endothelial
cells mediated by VEGF. Proc. Natl Acad. Sci. USA, 99, 4349–4354.
72. Muchmore,S.W. et al. (2000) Crystal structure and mutagenic analysis of
the inhibitor-of-apoptosis protein survivin. Mol. Cell, 6, 173–182.
73. Grossman,D. et al. (1999) Expression and targeting of the apoptosis
inhibitor, survivin, in human melanoma. J. Invest. Dermatol., 113,
1076–1081.
74. Cao,C. et al. (2004) XIAP and survivin as therapeutic targets for
radiation sensitization in preclinical models of lung cancer. Oncogene,
23, 7047–7052.
75. Sharma,H. et al. (2005) Antisense-mediated downregulation of antiapoptotic proteins induces apoptosis and sensitizes head and neck
squamous cell carcinoma cells to chemotherapy. Cancer Biol. Ther., 4,
720–727.
76. Du,Z.X. et al. (2006) Antisurvivin oligonucleotides inhibit growth and
induce apoptosis in human medullary thyroid carcinoma cells. Exp.
Mol. Med., 38, 230–240.
77. Fuessel,S. et al. (2004) Systematic in vitro evaluation of survivin directed
antisense oligodeoxynucleotides in bladder cancer cells. J. Urol., 171,
2471–2476.
78. Ansell,S.M. et al. (2004) Inhibition of survivin expression suppresses
the growth of aggressive non-Hodgkin’s lymphoma. Leukemia, 18,
616–623.
79. Sah,N.K. et al. (2006) Effect of downregulation of survivin expression on
radiosensitivity of human epidermoid carcinoma cells. Int. J. Radiat. Oncol. Biol. Phys., 66, 852–859.
Targeting survivin in cancer therapy
80. Kanwar,J.R. et al. (2001) Effects of survivin antagonists on growth of
established tumors and B7-1 immunogene therapy. J. Natl Cancer Inst.,
93, 1541–1552.
81. Pennati,M. et al. (2002) Ribozyme-mediated attenuation of survivin
expression sensitizes human melanoma cells to cisplatin-induced apoptosis. J. Clin. Invest., 109, 285–286.
82. Pennati,M. et al. (2004) Ribozyme-mediated down-regulation of survivin
expression sensitizes human melanoma cells to topotecan in vitro and
in vivo. Carcinogenesis, 25, 1129–1136.
83. Pennati,M. et al. (2003) Radiosensitization of human melanoma cells by
ribozyme-mediated inhibition of survivin expression. J. Invest. Dermatol.,
120, 648–654.
84. Pennati,M. et al. (2004) Ribozyme-mediated inhibition of survivin
expression increases spontaneous and drug-induced apoptosis and
decreases the tumorigenic potential of human prostate cancer cells.
Oncogene, 23, 386–394.
85. Choi,K.S. et al. (2003) Ribozyme-mediated cleavage of the human survivin mRNA and inhibition of antiapoptotica function of survivin in MCF-7
cells. Cancer Gene Ther., 10, 87–95.
86. Izquierdo,M. (2005) Short interfering RNAs as a tool for cancer gene
therapy. Cancer Gene Ther., 12, 217–227.
87. Carvalho,A. et al. (2003) Survivin is required for stable checkpoint
activation in taxol-treated HeLa cells. J. Cell Sci., 116, 2987–2998.
88. Ai,Z. et al. (2006) Inhibition of survivin reduces cell proliferation and
induces apoptosis in human endometrial cancer. Cancer, 107, 746–756.
89. Paduano,F. et al. (2006) Silencing of survivin gene by small interfering
RNAs produces supra-additive growth suppression in combination with
17-allylamino-17-demethoxygeldanamycin in human prostate cancer
cells. Mol. Cancer Ther., 5, 179–186.
90. Nakao,K. et al. (2006) Survivin downregulation by siRNA sensitizes
human hepatoma cells to TRAIL-induced apoptosis. Oncol. Rep., 16,
389–392.
91. Lens,S.M. et al. (2003) Survivin is required for a sustained spindle checkpoint arrest in response to lack of tension. EMBO J., 22, 2934–2947.
92. Beltrami,E. et al. (2004) Acute ablation of survivin uncovers p53dependent mitotic checkpoint functions and control of mitochondrial
apoptosis. J. Biol. Chem., 279, 2077–2084.
93. Jiang,G. et al. (2006) Lentivirus-mediated gene therapy by suppressing
survivin in BALB/c nude mice bearing oral squamous cell carcinoma.
Cancer Biol. Ther., 5, 435–440.
94. Li,Q.X. et al. (2006) Survivin stable knockdown by siRNA inhibits tumor
cell growth and angiogenesis in breast and cervical cancers. Cancer Biol.
Ther., 5, 860–866.
95. Yonesaka,K. et al. (2006) Small interfering RNA targeting survivin
sensitizes lung cancer cell with mutant p53 to adriamycin. Int. J. Cancer,
118, 812–820.
96. Kappler,M. et al. (2005) Radiosensitization after a combined treatment
of survivin siRNA and irradiation, is correlated with the activation of
caspases 3 and 7 in a wt-p53 sarcoma cell line, but not in a mt-p53
sarcoma cell line. Oncol. Rep., 13, 167–172.
97. Coma,S. et al. (2004) Use of siRNAs and antisense oligonucleotides
against survivin RNA to inhibit steps leading to tumor angiogenesis.
Oligonucleotides, 14, 100–113.
98. Tu,S.P. et al. (2005) Gene therapy for colon cancer by adeno-associated
viral vector-mediated transfer of survivin Cys84Ala mutant. Gastroenterology, 128, 361–375.
99. Grossman,D. et al. (2001) Inhibition of melanoma tumor growth in vivo by
survivin targeting. Proc. Natl Acad. Sci. USA, 98, 635–640.
100. Mesri,M. et al. (2001) Cancer gene therapy using a survivin mutant adneovirus. J. Clin. Invest., 108, 981–990.
101. Yan,H. et al. (2006) Induction of melanoma cell apoptosis and inhibition
of tumor growth using a cell-permeable survivin antagonist. Oncogene,
25, 6968–6974.
102. Lo,H.W. et al. (2005) Cancer-specific gene therapy. Adv. Genet., 54, 235–
255.
103. Chen,J.S. et al. (2004) Cancer-specific activation of the survivin
promoter and its potential use in gene therapy. Cancer Gene Ther., 11,
740–747.
104. Van Houdt,W.J. et al. (2006) The human survivin promoter: a novel transcriptional targeting strategy for treatment of glioma. J. Neurosurg., 104,
583–592.
105. Pennati,M. et al. (2005) Potentiation of paclitaxel-induced apoptosis by
the novel cyclin-dependent kinase inhibitor NU6140: a possible role for
survivin down-regulation. Mol. Cancer Ther., 4, 1328–1337.
106. Plescia,J. et al. (2005) Rational design of shepherdin, a novel anticancer
agent. Cancer Cell, 7, 457–468.
107. Gyurkocza,B. et al. (2006) Antileukemic activity of shepherdin and
molecular diversity of Hsp90 inhibitors. J. Natl Cancer Inst., 98, 1068–
1077.
108. Meli,M. et al. (2006) Small-molecule targeting of heat shock protein 90
chaperone function: rational identification of a new anticancer lead.
J. Med. Chem., 49, 7721–7730.
109. Chang,C.C. et al. (2004) Tetra-O-methyl nordihydroguaiaretic acid induces growth arrest and cellular apoptosis by inhibiting Cdc2 and survivin
expression. Proc. Natl Acad. Sci. USA, 101, 13239–13244.
110. Park,R. et al. (2005) Systemic treatment with tetra-O-methyl nordihydroguaiaretic acid suppresses the growth of human xenograft tumors. Clin.
Cancer Res., 11, 4601–4609.
111. Huang,R.C. et al. (2006) Survivin-dependent and -independent pathways
and the induction of cancer cell death by tetra-O-methyl nordihydroguaiaretic acid. Semin. Oncol., 33, 479–485.
112. Mita,M.M. et al. (2006) Apoptosis: mechanism and implications for cancer therapeutics. Targ. Oncol., 1, 197–214.
113. Turkson,J. (2004) STAT proteins as novel targets for cancer drug discovery. Expert. Opin. Ther. Targets, 8, 409–422.
114. Emami,K.H. et al. (2004) A small molecule inhibitor of b-catenin/cyclic
AMP response element-binding protein transcription. Proc. Natl Acad.
Sci. USA, 101, 12682–12687.
115. Xia,W. et al. (2006) Regulation of survivin by ErbB2 signaling: therapeutic implications for ErbB2-overexpressing breast cancers. Cancer Res.,
66, 1640–1647.
116. Andersen,M.H. et al. (2002) Survivin—a universal tumor antigen. Histol.
Histopathol., 17, 669–675.
117. Rohayem,J. et al. (2000) Antibody response to the tumor-associated
inhibitor of apoptosis protein in cancer patients. Cancer Res., 60,
1815–1817.
118. Schmidt,S.M. et al. (2003) Survivin is a shared tumor-associated antigen
expressed in a broad variety of malignancies and recognized by specific
cytotoxic T cells. Blood, 102, 571–576.
119. Schmitz,M. et al. (2000) Generation of survivin-specific CD8þ T effector
cells by dendritic cells pulsed with protein or selected peptides. Cancer
Res., 60, 4845–4849.
120. Reker,S. et al. (2004) Identification of novel survivin-derived CTL epitopes. Cancer Biol. Ther., 3, 173–179.
121. Xiang,R. et al. (2005) A DNA vaccine targeting survivin combines apoptosis with suppression of angiogenesis in lung tumor eradication. Cancer
Res., 65, 553–561.
122. Otto,K. et al. (2005) Lack of toxicity of therapy-induced T cell
responses against the universal tumour antigen survivin. Vaccine, 23,
884–889.
123. Tsuruma,T. et al. (2004) Phase I clinical study of antiapoptosis protein,
survivin-derived peptide vaccine therapy for patients with advanced or
recurrent colorectal cancer. J. Transl. Med., 2, 19.
Received December 7, 2006; revised February 21, 2007;
accepted February 21, 2007
1139