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Review Article
The role of survivin in diagnosis, prognosis and treatment of breast cancer
Department of Vascular and Endocrine Surgery, First Affiliated Hospital, Fourth Military Medical University. Xi'an 710032, Shaanxi Province, China
# These authors contributed equally to this paper.
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Abstract
Survivin is a cancer gene that is silenced in differentiated tissues, while overexpressed at high levels in vast majority
of tumors. It has garnered great interests in recent years. Some essential properties characterizing it as an ideal target
involve inhibiting apoptosis, promoting mitosis, stimulating vessel growth thus inducing chemo-resistance. These
functions touch the full gamut of tumorigenesis, including proliferation, migration, and invasion, and collectively facilitate
malignant behavior. In the case of breast cancer, survivin detection independent or combined in serum and/or
urine has emerged as a measure for diagnosis. Moreover, many studies indicated aberrant expression of survivin is
associated with poor prognosis and drug/radiation resistance. Strategies targeting survivin to treat breast cancer have
got promising initial results. In this review, we summarize its role in breast cancer’s diagnosis, prognosis, and treatment,
with the intention to explain why this interesting molecule plays a conflicting role.
Key words
survivin; diagnosis; prognosis; treatment; breast neoplasm
J Thorac Dis 2010;2:100-110. DOI: 10.3978/j.issn.2072-1439.2010.02.02.009
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Introduction
Breast cancer is by far the leading cause of cancer death
in women throughout the world and its incidence continues
to rise (1,2). The main reasons consist of high propensity to
metastasize at an early stage and the acquired resistance to
a wide range of anticancer agents (3). Once the cancer has
spread beyond the breast and loco-regional lymph nodes, it
is seemed to be incurable (4). In such cases, chemotherapy
or radiotherapy considered to be the main treatment,
but accompanied by various adverse effects. This fact
emphasizes the importance of selecting sensitive diagnostic
and prognostic markers in the early stage and more efficient
targeted treatment for this disease.
Survivin is an inhibitor of apoptosis protein (IAP) and
is overexpressed in a wide spectrum of tumors including
breast cancer (5-7). Its primary functions comprise
inhibiting apoptosis and regulating mitosis, which are associated with carcinogenesis (8). Considering of its
differentiated expression between normal and cancerous
tissues, it has become an attractive molecule for early
detection and prognoses of breast cancer. Additionally,
inhibition of survivin alone or in combination with other
approaches has emerged as a promising therapeutic
strategy.
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Biologic function of survivin
Survivin as an inhibitor of apoptosis
Survivin inhibits apoptosis either directly or indirectly
by interfering with the function of caspase-3, caspase-7
and caspase-9 (9-13). The effect of survivin on apoptosis
may also in a caspase-independent way by interaction and
cooperation with hepatitis B interacting protein (HBXIP)
(14), Smac/diablo (15-17), AIF pathway (18), HSP90 (19),
c-IAP-1 (20) HER-2/EGF (21,22) leptin/Stat3 (23) and
progesterone/P53 (24).
Survivin as a promotor of mitosis
Current evidence suggests that survivin also plays
a role in regulating mitotic progression. Which, rather
than inhibiting apoptosis, is the primary function of
survivin (25,26). In some cancer cells, survivin inhibition
produces defects in chromosome segregation, cytokinesis
and ultimately cell division, without measurable impact
on apoptosis (27,28). The probable mechanisms include
mediating mitosis by acting as an interphase between the centromere/central spindle and the CPC (chromosomal
passenger complex) (29). The CPC is composed of the
mitotic kinase aurora-B, borealin and INCENP and
is involved in correcting attachment errors between
chromosomes and the mitotic spindle, ensuring the correct
completion of cytokinesis.
Survivin facilitating angiogenesis
In addition to its involvement in apoptosis and mitosis,
there is growing evidence suggesting survivin has been
implicated in angiogenesis. Transfection of endothelial
cells (EC) with genes coding of survivin-specific siRNA
(30), or antisense oligonucleotide (ASODN) (31), or
phosphorylation-defective form of survivin (32) result in
vascular regression during tumor angiogenesis. Adversely,
survivin expression (both mRNA and protein) was
increased in cultured vascular EC following exposure to
angiogenic factors such as VEGF and bFGF (33-35). The
mechanism by which survivin promotes angiogenesis is
likely to attributed to its ability to preserve microtubule
structure integrity, and inhibit apoptosis in EC, which may
be required for EC viability and cytoprotection (35,36).
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Diagnosis and detection of breast cancer
About 30-50% of patients with early-stage breast
cancer, even those with negative lymph nodes, still develop
a recurrent disease, which is metastatic in most cases
(37-39). In patients who receive neoadjuvant chemotherapy
(NACT), about 10%-35% (40,41) do not respond well
because of chemoresistance and have a dismal prognosis
of 10-20% 5-year survival (42). Breast cancer has been
posing a great challenge with an overall poor long-term
prognosis (43). There is increasing evidence that primary
cancers begin releasing cancer cells into the circulation at
an early stage (44-49). So peripheral blood of breast cancer
patients was used for the detection of circulating tumor
cells (CTCs) (50). At present, sampling of tumor markers
such as cytokeratin 20, mammaglobin, c-Met, maspin,
epidermal growth factor receptor (EGFR), Her2/neu,
membrane association mucin1 (MUC1), CD44, have been
detected with varying degrees of sensitivity and specificity
(51-54). Most of these factors are less reliable for small
tumors and further stratification of breast cancer patients
remains a challenge (55). Since survivin is selectively
expressed in malignant tissues, and can inhibit apoptosis,
promote cell division and enhance angiogenesis (56), its
detection in body fluids could serve as an ideal tumor
marker for diagnosis and detection (tab1) (57-59). Such
a study was carried out by Yie et al detected survivinexpressing
circulating breast cancer cells in the peripheral
blood using a RT-PCR ELISA technique (60). Survivin-expressing circulating cancer cells were detected in the
peripheral blood samples from 34 (50.7%) out of 67 breast
cancer patients, but not in the healthy women that were
used as controls. The presence of survivin-expressing
circulating breast cancer cells was found to be significantly
associated with various clinicopathological parameters
such as vessel infiltration, histological grade, tumor size,
nodal involvement, ER/PgR status, Her-2 expression and
clinical stages of the disease. The authors concluded that
the detection of circulating cancer cells expressing survivin
mRNA could provide valuable information for predicting
metastasis and recurrence of breast cancer.
Similar to these findings, Chen et al studied the gene
expression in a combined way using a membrane array
technique (61). Survivin was shown to be one of the four
marker genes detected in circulating tumor cells in the
blood of Taiwanese women with breast cancer. The results
revealed that tumor size, histologic grade, lymph node
metastasis and TNM stage were significantly correlated
with the positive detection of these genes, including
survivin.
Guney N conducted a study to investigate the serum and
urine levels of survivin in patients with breast cancer and
the relationships with known prognostic parameters and
therapy (62). Their results suggested that serum survivin
level could be a sensitive marker for detecting metastases in
lymph nodes from breast cancer patients. More recently, a
research from China discussed that detection of survivin or
other associated gene may serve as an important diagnostic
test for breast cancer and provide an early biomarker of
aggressive tumor behavior before the appearance of distant
metastasis. Multiple marker assays may significantly
improve the sensitivity of detecting heterogeneous tumor
cells compared with single marker assay. Further clinical
trials are needed to provide more convincing evidence.
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Survivin and prognosis of breast cancer
The ultimate outcome of breast cancer relies on the
initial stage of the cancer at diagnosis. The main prognostic
factors associated with breast cancer are lymph node
involvement, tumor size, histological grade, and hormone
receptor status. However, tumor at the same stage can
behave in a different manner, and the prognosis can
vary (80). So it is important to find biomarkers that will
predict the likelihood of recurrence and identify those
patients who might benefit from therapy. Hence, low-risk
patients can be spared unnecessary treatment, avoiding
side effects and reducing the cost of treatment. Moreover,
high-risk patients could be rapidly identified and offered
more aggressive treatment. Recently, abundant survivin
expression in human breast cancers have been found using RT-PCR (64,80,81). Several studies were carried out to
assess the possibility of survivin as a prognostic molecule.
For example, in a study of 275 patients with breast cancer
(70), survivin mRNA was highly expressed in tissues from
younger patients (<50) and in high-grade cancer tissues.
High survivin concentrations were most strongly associated
with ER- or PR-negative tumors. Survivin demonstrates
a strong, independent association with poor prognosis.
Survivin might be used as a new marker to stratify breast
cancer patients for more optimal treatment modalities, or
it could be a promising new target for therapy. In another
study (66), survivin expression was examined in 167 cases
of breast cancer and the results suggest that apoptosis
inhibition by survivin, alone or in cooperation with bcl-2,
is a significant prognostic parameter of worse outcome in
breast carcinoma.
Consistent with these results at mRNA level，Ryan et
al showed that survivin protein, as determined by ELISA,
was also an independent prognostic factor in breast cancer
(81). In this study, the prognostic impact of survivin
was independent of patient age, tumor size, lymph node
status, hormone receptor status, HER-2, VEGF, and
urokinase plasminogen activator/plasminogen activator
inhibitor type-1. Fuzhong et al reported that patients of
low expression of survivin have high response rate after
neoadjuvant chemotherapy and the results shows that
survivin is an important predictive factor for effectiveness
of neoadjuvant chemotherapy in locally advanced breast
cancer (79). Another study analyzed the five survivin
transcripts in 60 breast cancer patients treated with FEC
(fluorouracil, epirubicin and cyclophosphamide) or TE (taxol and epirubicin) (82). They found that an imbalance
in the alternative transcript ratios might make the cells
resistant or sensitive to apoptosis. They also demonstrate
for the first time that alternative survivin transcript
expression levels may be predictive markers in FEC and
TE treatment in breast carcinoma.Converse conclusions
are also made in a few studies, for example, Kostadima
et al quantitatively measured mRNA levels of survivin in
272 breast cancer patients but fail to correlate these levels
with disease outcome (39). But the paper was questioned
by Span et al for disproportionate groups and unfeasible
multivariate analysis (83). Kennedy et al examined the
expression of survivin protein in a series of 293 cases
of invasive primary breast carcinoma (67), they found
nucleus-localized survivin expression was a significant
independent prognostic indicator of favorable outcome
both in relapse-free and overall survival. This is a logical
finding, as caspases are present and function in the cell
cytoplasm (71). Although the black and white IHC images
provided in the study do not permit appreciation of the
nuclear or cytoplasmic staining of survivin, although the
results could not be replicated in the 106 samples used
for the RT-PCR study (68), their findings highlights that
survivin has different functions by different forms with
respective subcellular location. The above mentioned
study firstly analyzed the expression of survivin and its
two splice variants, survivin-DEx3 and survivin-2B in
breast cancer (68). The results indicated that bcl-2 mRNA
expression, but not survivin and its two splice variants, is
a significant prognostic factor associated with favorable
outcome, in terms of both RFS and OS, and correlating with ER positivity.
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Survivin and treatment of breast cancer
Adjuvant chemotherapy or neoadjuvant chemotherapy
Growing evidence has indicated that survivin plays a
crucial role in drug resistance, and modulation of survivin
expression affects drug effectiveness. Mesri et al used a
breast cancer line and delivered a recombinant adenovirus
encoding survivin (T34A) into subcutaneous tumor nodules
or into tumor-bearing peritoneum, striking antitumor
activity was observed, parallel to taxol and more effective
than adriamycin in induction of MCF-7 cell apoptosis and
enhanced taxol-induced cell death (84). In three xenograft
breast cancer models in immunodeficient mice, pAd-
T34A suppressed de novo tumor formation, inhibited by
approximately 40% the growth of established tumors,
and reduced intraperitoneal tumor dissemination. Tumors
injected with pAd-T34A exhibited loss of proliferating cells
and massive apoptosis by in situ internucleosomal DNA
fragmentation.
Many studies have demonstrated that some cancer
prevention drugs may function by inhibiting survivin
expression (85,86) and overexpression of survivin was
related to chemoresistance of various drugs including
ad r iamycin (87), cisplatin (88-90) and taxol (91).
Upregulation of survivin by taxol per se appears to be an
early event and independent of paclitaxel-mediated mitotic
arrest in MCF-7 breast cancer cells (92). High survivin
expression in turn results in resistance to taxol and may
be a survival pathway in cancer cells (93). Retinoids, an inducer of apoptosis, have been shown to sensitize
MCF-7 breast cancer cells to taxol by down regulating
survivin (94). Similar outcome was got by several groups
when they respectively investigated the potential role
of prodigiosin (95), flavopiridol (96) , resveratrol (97),
3,3V-diindolylmethane (98) and Calcium sensing receptor
(99) in the treatment of breast cancer. Moreover, PI-3K/
Akt2 signal pathway (21, 100) and leptin/stat3 pathway
(23) activation both played roles in acquired resistance
to docetaxel in breast cancer cells. More recently, Lu et
al found that the mechanism of Her-2 overexpression
conferring on breast cancer cells resistance to taxol is via
upregulation of survivin (101).
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Radiotherapy
Evidence has also revealed an essential role for survivin
in radiation therapy of breast cancer, i.e., survivin can be
drastically down-regulated by radiation, with its high levels
associated with resistance to radiotherapy. High expression
of survivin in breast cancer associated fibroblasts in vitro
shows resistance to ultraviolet (UV) light irradiation (105).
Exposure of breast carcinoma MCF-7 cells to UVB, or
fractionated radiation resulted in a significant increased
survivin expression (96,106). Kim et al examined the effect
of signal transducer and activator of transcription 3 (stat3)
on survivin expression in irradiated breast cancer cells, and
found inhibiting survivin and stat3 together could promote
radiation sensitivity in MDA-MB-231 breast cancer cells
(102). Consistently, combination of radiation and 17-AAG
(an antitumor agent which blocks survivin’s function) in human BT-474 breast cancer cells resulted increased
apoptotic indexes and cytotoxicity (103). A recent study
from China shows that deguelin enhances radiosensitivity
of breast cancer MDA-MB-231 cells by inhibiting pAkt
and survivin expression (104). Similar outcome can be seen
in other cancers, such as rectal cancer (107), pancreatic and
gastric cancer (108,109).It is worthy of note that survivin
can contribute to radiation resistance also by promoting the
survival of tumor vascular endothelial cells (109,110,111).
In fact, induction of vascular endothelial apoptosis was
recently shown to be a major determinant of overall tumor
response to radiotherapy (35).
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Why survivin act as an absolutely different role?
We must notice that with the increased number of
publications, inconsistent conclusions have been reported
frequently in breast cancer (35), also in gastric cancer (112).
Several reasons contribute to the opposing behavior of
survivin.
There are all 5 splice variants (wide-type survivin,
survivin2B, survivin2α, survivin3B and survivinΔEx3) with
different structure and function (72, 112-114). For example,
survivin-2a seems to strongly attenuate the antiapoptotic
activity of survivin even without an apoptotic stimulus
(115). survivin3B was more frequent in high grade breast
carcinomas and correlated with the p53 gene mutation,
suggesting a positive role of survivin-3B in apoptosis
inhibition (116). Survivin2B might act as a proapoptotic
factor in breast cancer (116), and its expression decreases
in a tumor stage-dependent way, in small tumor size, its
expression is significantly higher and is inversely associated
with axillary node positive carcinomas (116). Theoretically,
if survivin2B expresses predominantly, it will related to
a good prognosis. A report confirmed the hypothesis by
reporting that survivin-2B expression is toxic to cells (117).
But its expression is at low levels in most malignant tissues,
especially in late stage ones, so its function was hidden
by other splice variants and this variation may play a role
in cancer development (72, 116, 118,119). That may be the
reason of some reports indicating a good or inconclusive
prognostic role of survivin’s expression in breast cancer
(67,68). To regulate the balance between these splice
variants, or selectively inhibit antiapoptotic variants, or
enhance proapoptotic variants might lead to novel strategy
for cancer prevention and therapeutics.
Besides different splicing forms, survivin also
localized in different subcellular compartments. Wild
type survivin and survivin2B preferentially localize
in cytoplasm. Survivin 2a, almost equally between the
cytoplasm and nucleus, While survivinΔEx3 localizes
in both mitochondria and nucleus. However, in mitotic cells, survivin-ΔEx3 appeared to be translocated to and
colocalized with the mitotic spindle. Dohi et al reported
that mitochondrial survivin could be released into the
cytoplasm, where it prevents caspase activation and inhibits
apoptosis (120). Other studies found sending survivin
into the nucleus (121) or lowered cytoplasmic-to-nuclear
ratio of survivin (77) or nuclear export-deficient survivin
mutants (122-124) failed to protect tumor cells against
chemo- and radiotherapy-induced apoptosis. So exploiting
the mechanism for the survivin’s dynamic subcellular
distribution and translocation will offer a new point of
view.
Methylation and Phosphorylation. Several observations
show that survivin is unmethylated in cancer but may be
selectively methylated in normal tissues with individual
variations (125,126). Methylation may play important a
role in the p53 mediated suppression of survivin (127).
Another critical requirement for survivin function was
the phosphorylation on Thr34 (128). Treatment with a
cyclin-dependent kinase inhibitor, flavopiridol, suppressed
survivin phosphorylation on Thr34 and resulted in loss of
survivin expression and induction of apoptosis in breast
cancer cells (96).
Specificity and sensitivity of antibody or RT-PCR used
in the research. Interestingly, some antibodies are specific
to different domain of survivin, for example, an antibody
specific to sequence Ala3–Ile19, recognizes survivin band
from nuclear fraction. Another antibody, to sequence Cys57
–Trp67, recognize survivin band from cytosol fraction (129).
These immunohistochemical-based studies have failed
to reach a consensus about how survivin staining should
be interpreted (77). If the antibody used by the author
could not react with the full survivin, or the tissues or
images were inappropriately processed by the researchers,
bias would occur. For example, different variants have
same N-terminal sequence, which could be potentially
recognized by survivin antibodies used currently, this
observation raises a possibility that the nuclear survivin
is survivin-ΔEx3 or both survivin and survivin-ΔEx3
(130). Which has been pointed out by Li et al according
to their working experiences and the excellent images
they offered (86). And this dilemma can be resolved by
image analysis (85). Using RT-PCR to measure survivin
mRNA is more accurate because survivin concentrations
are largely controlled at the level of gene transcription (36,
131). Real-time RT-PCR has the advantages of being more
quantitative than classical one (70). Although the primers
and probes were designed specifically to pick only the
intended variant, they would likely to react with each other
(132). So more sensitive and special primers and probes are
needed.
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Conclusion
Because of its functions as a cancer gene/protein,
survivin is currently extensively used in diagnosis,
prognosis and treatment of breast cancer. The detection
of serum/urinary survivin by immunochemistry or RTPCR
seems to be a promising assay to detect both newly
diagnosed and recurrent breast cancer. Increased survivin
expression in cancer patients is an unfavorable prognostic
marker correlating with decreased overall survival in breast
carcinomas. Survivin overexpression may be a predictive
factor to determine response to chemotherapy and
radiotherapy in patients with breast cancer. Survivin has
been pursued as a cancer drug target by diverse strategies,
such as immuno approaches and the application of smallmolecule
antagonists. Although some inconsistent reports
exists, overwhelming reports support that measurement
of survivin expression can help to make early diagnosis,
predict prognosis and judge therapy effect of breast cancer.
Targeting it for cancer treatment has less/ no toxicity to
normal tissue and cells. These preliminary findings on the
diagnostic, prognostic and predictive potential of survivin
should now be confirmed in large prospective trials.
Furthermore, assays for the measurement of survivin and
its splice variants should be simplified, standardized and
evaluated in external quality assurance schemes.
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Acknowledgments
This work was supported by the Science and Technology
Development Project of Shaanxi Province (no.
2007K09-06), the Social Development Project of Xi’an (no.
YF07164), and the National Natural Science Foundation of
China (no. 30872514).
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References
Cite this article as: Lv YG, Yu F, Yao Q, Chen JH, Wang L. The role of survivin in diagnosis, prognosis and treatment of breast cancer. J Thorac Dis 2010;2(2):100-110. doi: 10.3978/j.issn.2072-1439.2010.02.02.009
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