The authors have declared that no competing interests exist.
Conceived and designed the experiments: ZC. Performed the experiments: SX HX. Analyzed the data: SX HX XS KW BL. Contributed reagents/materials/analysis tools: SX HX XS KW BL. Wrote the paper: SX ZC. Designed and revised the article: ZC. Collected articles, summarized data, did statistical work and drafted the manuscript: SX. Collected articles, summarized data and did statistical work: HX XS. Provided collected data and summarized information in part: BL KW.
Survivin has been proposed as a promising prognostic marker in oral squamous cell carcinoma (OSCC), but the published data on survivin expression in patients with this condition are controversial. To address this we performed a meta-analysis systematically to assess the clinicopathological and prognostic significance of survivin expression in OSCC.
We searched PubMed, Embase, Web of Science and Ovid databases for papers investigating the clinicopathological and prognostic significance of survivin expression in OSCC. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to determine the relevance of survivin.
A total of 15 papers, including 1040 cases in which survivin expression was detected by immunohistochemistry (IHC) or reverse transcription polymerase chain reaction (RT-PCR), were included. A meta-analysis of clinicopathological variables revealed a correlation between survivin expression and lymph node metastasis (OR = 0.62, 95% CI = 0.44–0.88, p < 0.05) and clinical stage (OR = 0.63, 95% CI = 0.41–0.96, p < 0.05). However, no significant associations were found between survivin expression and tumor differentiation grade (OR = 0.72, 95%CI = 0.26–1.11, p > 0.05), depth of invasion (OR = 0.76, 95% CI = 0.50–1.14, p > 0.05), age (OR = 0.78, 95% CI = 0.48–1.29, p > 0.05) or gender (OR = 1.31, 95% CI = 0.86–2.01, p > 0.05). Subgroup analysis using stratified detection methods showed no significant associations between the expression of survivin protein and clinicopathological variables in OSCC. A correlation between survivin expression and poor prognosis of patients with OSCC (HR = 1.62, 95% CI = 1.23–2.01, p < 0.05) was demonstrated.
Survivin is a potential prognostic marker of OSCC. Future studies with larger sample sizes and well-designed inclusion criteria will be needed to dissect the role of survivin expression in determining the clinicopathological features and/or prognosis of OSCC.
Oral cancer is one of the 10 most common cancers in the world. Its high mortality rate and the disfigurement that survivors may suffer gives rise to a considerable global public health burden [
Widely used and conventional prognostic factors, such as the presence of lymph node metastases, clinical stage and tumor size, are not always of use in the early diagnosis of OSCC. Further, the inherent heterogeneity of both tumor biology and patient factors between affected individuals means that reliable prognostic factors for OSCC are currently lacking. Additional factors, including molecular markers, are likely to be needed to explain the mechanism of development and occurrence of OSCC.
Biomarkers are important in establishing an accurate diagnosis and also can provide prognostic data. For instance, alpha fetoprotein (AFP) is widely used as one facet in the process of diagnosing liver cancer. However, to date, no specific tumor marker has been identified for use in OSCC.
In the 1990’s, survivin, a member of the ‘inhibitor of apoptosis’ (IAP) family, was found to be over-expressed in tumors and fetal tissues, but not in normal adult tissues [
This has been directly addressed in several cancer types with regard to determining prognosis [
We searched PubMed, Web of Science, Ovid and Embase databases on April 3rd 2014 for articles in English that met the following search criteria: (1) survivin OR BIRC5 OR baculoviral inhibitor of apoptosis repeat-containing 5, and (2) oral OR mouth OR lip OR buccal OR tongue OR gingiva OR palate OR mouth floor, and (3) tumor OR cancer OR carcinoma OR neoplasm. Retrieved papers were independently screened by two authors according to the title, abstract and type of article, and irrelevant papers were dropped out. A manual review of the references cited in the included articles was also performed to highlight articles that might have been missed by the original search strategy. All relevant papers were then assessed using inclusion and exclusion criteria for meta-analysis, as described below.
The following criteria were set and reviewed by two independent authors: (1) survivin expression of OSCC was evaluated by immunohistochemistry (IHC) or RT-PCR analysis; (2) the levels of survivin expression were used to estimate the relation between survivin and clinicopathological variables and/or prognosis of OSCC; (3) articles were published in English as full paper; (4) odds ratios (ORs) for estimating clinicopathological variables were provided or were extractable from the original articles; sufficient information was provided in relation to survivin expression and prognosis of OSCC; (5) when multiple publications from a particular research group reported data from overlapping samples, the study reporting the largest dataset was included; (6) reviews, meta-analyses, letters, conference abstracts, case reports and non-English language articles were excluded; (7) articles that provided no sufficient information on prognosis or ORs were excluded.
All data were independently reviewed and extracted by two authors (Xie and Xu). Differences between reviewers were resolved by discussion and through consultation, if necessary. The following characteristics were collected from each study: first author, publication year, subjects’ ethnicity, country, sample size, cut-off values, survivin subcellular location, clinicopathological and prognostic variables, and other relevant data.
We used the Newcastle-Ottawa Scale (NOS) [
Data management and analysis were performed with STATA 11.0 software (Stata Co., College Station, TX). The ORs with corresponding 95% CIs were used to define the association between survivin expression and clinicopathological variables in patients with OSCC. We extracted the clinicopathological variables and combined them by meta-analyses. The clinicopathological variables included: the presence or absence of lymph node metastasis; clinical stage I and stage II versus stage III and stage IV; good differentiation versus moderate-poor differentiation; depth of invasion T1 and T2 versus T3 and T4; male versus female; and age less than 60 versus more than 60 years.
For prognostic parameters, the hazard ratios (HRs) with corresponding 95% CIs were calculated to estimate the effect of survivin expression on survival rates. If the authors reported HR and 95% CI, data were directly extracted from the original articles. Otherwise, these data were calculated by the methods described by Parmar et al. [
In order to calculate the heterogeneity of the studies we included, the Chi-Square test was used and significance was set at p < 0.05 [
According to the Cochrane Handbook, meta-analyses and systematic reviews are considered to be the best available evidence if all eligible trials are included. However, ‘the best available evidence’ might not be equal to ‘sufficient evidence’. Based on this issue, we applied the TSA to estimate the robustness of the current conclusions [
A total of 614 articles were retrieved by the database search, of which 576 studies were excluded as being irrelevant to OSCC or survivin, or due to lack of clinicopathological or prognostic data. A further two potentially eligible papers were obtained by screening the references of reviews. After more detailed evaluations of the 40 potentially eligible articles, three were excluded as being reviews. A further two studies were excluded due to the presence of overlapping data, and 11 more failed to provide sufficient data to warrant inclusion. Five studies were meeting abstracts only, and were therefore also excluded. Three were unavailable in English. A single further paper was excluded because it provided only recurrence-free data without any discussion of clinicopathological features or survival rates. Fifteen papers were therefore included in the meta-analysis to estimate the clinicopathological and prognostic significance of survivin as a potential marker in OSCC [
The key information extracted from each eligible paper is summarized in
First Author | Year | Country | Cases | AT |
NOS |
C. Features |
Prognosis | Method | Cut-off value | HR Estimate (95% CI) | Location |
---|---|---|---|---|---|---|---|---|---|---|---|
L Lo Muzio | 2003 | Italy | 110 | NA | 8 | N,S,D,A,G | HR | IHC | <5% | HR = 2.28 (1.49–4.04) | cytoplasm and/or nucleus |
C Tanaka | 2003 | Japan | 71 | NA | 8 | N,S,T,D,G,A | NA | IHC | IHC score<100 | NA | cytoplasm |
M-J Kim | 2005 | South Korea | 113 | NA | 7 | NA | sur. curve | RT-PCR | median value | HR = 2.78 (1.53–5.08) | --- |
C-Y Lin | 2005 | Taiwan | 96 | NA | 7 | N,S,T,D,G | sur. curve | IHC | <25% | HR = 1.94 (1.11–3.37) | Cytoplasm |
G Marioni | 2005 | Italy | 18 | NA | 7 | N,T,D,G,A | NA | IHC | <9.5% | NA | nucleus and/or cytoplasm |
C Jane | 2006 | India | 38 | NA | 7 | D | NA | IHC | <5% | NA | cytoplasm |
K Freier | 2007 | Germany | 251 | AR/AC | 7 | T,N | sur. curve | IHC | <20% cytoplasm and <10% nucleus | HR = 1.39 (0.94–2.07) | nucleus and/or cytoplasm |
S De Maria | 2009 | Italy | 22 | NA | 8 | N,S,D,A,G | NA | IHC | <30% | NA | nucleus and/or cytoplasm |
Z Khan | 2009 | India | 29 | NA | 7 | N,S,T,D | NA | IHC | <10% | NA | nucleus and/or cytoplasm |
Y-H Kim | 2010 | South Korea | 38 | NA | 7 | N,D,S,G,A | sur. curve | IHC | <20% | HR = 1.87 (0.56–6.25) | nucleus and/or cytoplasm |
G Lodi | 2010 | Italy | 17 | NA | 7 | G,A | NA | Real-time RT-PCR | median value | NA | --- |
L-P Su | 2010 | China | 68 | No | 7 | N,S,T,D,G,A | HR | RT-PCR | median value | HR = 2.71 (1.46–5.10) | --- |
S-X Li | 2012 | China | 13 | NA | 8 | G,A | NA | ISH | >0% | NA | nucleus and/or cytoplasm |
M-B Zhang | 2013 | China | 110 | NA | 8 | NA | sur. curve | IHC | mean value | HR = 1.12 (0.54–2.30) | cytoplasm |
M Dogan | 2014 | Turkey | 46 | NA | 8 | N,D,G | NA | IHC | >0% | NA | nucleus and/or cytoplasm |
#AT: Adjuvant therapy
*NOS: Newcastle-Ottawa Scale
**C. Features: clinicopathological features; AR: adjuvant radiotherapy; AC: adjuvant chemotherapy; NA: not available; sur. curve: survival curve; IHC: immunohistochemistry; HR: hazard ratio; N: lymph node; S: clinical stage; T: depth of invasion; D: differentiation; G: gender; A: age
Using the Newcastle-Ottawa Scale system, quality assessment for the included studies yielded either seven stars or eight stars (shown in
We studied the relationship between high survivin expression and clinicopathological features in patients with OSCC. To identify an appropriate statistic model for combining the data, we performed heterogeneity analyses for all clinicopathological variables, including models for lymphatic metastasis, clinical stage, depth of invasion, cell differentiation, gender, and age. The results are shown in
Clinicopathological variables | No. of studies | Cases | Pooled data | Test for heterogeneity | |||
---|---|---|---|---|---|---|---|
OR (95% CI) | p | Chi2 | p | I2 | |||
10 | 499 (311/188) | 1.31 (0.86–2.01) | 0.21 | 9.51 | 0.392 | 5.30% | |
Protein expression (IHC) | 7 | 401 (270/131) | 1.19 (0.73–1.94) | 0.493 | 7.56 | 0.272 | 20.6% |
mRNA expression (PCR/ISH) | 3 | 98 (41/57) | 1.83 (0.75–4.46) | 0.181 | 1.63 | 0.443 | 0.0% |
8 | 357 (134/223) | 0.78 (0.48–1.29) | 0.337 | 4.47 | 0.724 | 0.00% | |
Protein expression (IHC) | 5 | 234 (79/155) | 0.77 (0.41–1.43) | 0.400 | 4.47 | 0.346 | 10.5% |
mRNA expression (PCR/ISH) | 3 | 123 (55/68) | 0.82 (0.36–1.86) | 0.631 | 0.02 | 0.988 | 0.0% |
7 | 434 (206/228) | 0.63 (0.41–0.96) | 0.033 | 6.83 | 0.337 | 12.10% | |
Protein expression (IHC) | 6 | 366 170/196) | 0.77 (0.47–1.24) | 0.281 | 3.54 | 0.617 | 0.0% |
mRNA expression (PCR/ISH) | 1 | 68 (36/32) | 0.26 (0.10–0.72) | 0.010 | 0.00 | --- | --- |
6 | 533 (296/237) | 0.76 (0.50–1.14) | 0.19 | 2.12 | 0.832 | 0.00% | |
Protein expression (IHC) | 5 | 465 (257/208) | 0.74 (0.47–1.17) | 0.200 | 2.08 | 0.720 | 0.0% |
mRNA expression (PCR/ISH) | 1 | 68 (39/29) | 0.83 (0.32–2.17) | 0.701 | 0.00 | --- | --- |
10 | 536 (271/265) | 0.72 (0.46–1.11) | 0.14 | 5.89 | 0.751 | 0.00% | |
Protein expression (IHC) | 9 | 468 (250/218) | 0.83 (0.51–1.35) | 0.449 | 3.91 | 0.865 | 0.0% |
mRNA expression (PCR/ISH) | 1 | 68 (21/47) | 0.35 (0.12–1.06) | 0.064 | 0.00 | --- | --- |
10 | 749 (354/395) | 0.62 (0.44–0.88) | 0.008 | 11.15 | 0.266 | 19.30% | |
Protein expression (IHC) | 9 | 681 (316/365) | 0.70 (0.48–1.02) | 0.062 | 7.81 | 0.453 | 0.0% |
mRNA expression (PCR/ISH) | 1 | 68 (38/30) | 0.27 (0.10–0.73) | 0.010 | 0.00 | --- | --- |
Since the studies included in the meta-analysis assessed survivin expression at both the transcriptional and the protein level, we undertook a subgroup analysis to assess the correlation between survivin expression and the clinicopathological features of OSCC using both detection methods. Lymph node metastasis and the clinical stage of OSCC were correlated with survivin expression at the genetic level, though no significant relationship between clinicopathological features and survivin overexpression at the protein level was identified (
Funnel plots were used to evaluate possible publication bias, and are shown in
The meta-analysis included seven assessments of the potential correlation between survivin expression and survival rates, including 786 patients. There was no significant heterogeneity among these articles (I2 = 4.2%, p(Q-test) = 0.394), and a fixed-effect model was used to combine the HR and 95% CI. The overall HR was 1.62 (95% CI = 1.23–2.01, p < 0.05), indicating that survivin overexpression is correlated with prognosis in OSCC. To further explore the associations between survivin gene or protein expression and prognosis, we carried out a subgroup analysis stratified by these two detection methods. The results suggested that the pooled HR of survivin mRNA and protein expression were 2.75 (95% CI = 1.48–4.02; I2 = 0.0%; p(Q-test) = 0.957; p <0.05) and 1.51 (95% CI = 1.10–1.92; I2 = 0.0%; p(Q-test) = 0.567; p <0.05), respectively, indicating that both survivin gene expression and protein expression were significantly correlated with prognosis in patients with OSCC (
Potential publication bias and sensitivity were assessed using Begg’s funnel plot and sensitivity analysis (
Fifteen trials (1040 subjects) were used to investigate the relevance of survivin expression with clinicopathological variables and OSCC prognosis. Using the relevance of survivin protein expression with lymph node metastasis of OSCC (including 9 trials with 678 patients) as an example, we performed the TSA and found that the required power to demonstrate clear conclusions was 2282 subjects (
The dashed curve represents the cumulative Z-curve. The solid line represents the trial sequential monitoring boundary.
In 1997, Ambrosini and his colleagues discovered survivin by hybridization screening of the human P1 genomic library with the effector cell protease receptor-1 cDNA [
Several studies have aimed to assess the potential association between survivin expression and the presentation and prognosis of cancers. Where results were unclear or controversial, meta-analyses have been performed looking at survivin’s role in lung cancer [
In this meta-analysis, we included 15 eligible articles comparing the different clinicopathological features or survival rates of patients with OSCC according to survivin expression. Our results suggested that expression of survivin at both the transcript and protein level was correlated with prognosis in patients with OSCC, indicating that survivin may be a promising molecular marker in this disease.
We further demonstrated that survivin mRNA expression is correlated with the presence of lymph node metastasis and with clinical stage, but does not appear to be related to other clinicopathological features. We failed to find any correlation between these clinicopathological features and survivin protein expression These apparently conflicting data for survivin transcript and protein expression might be explained, at least in part, by the existence of splice variants [
All the results of heterogeneity analyses, as well as sensitivity analysis and assessment of publication bias support the results from this meta-analysis as robust and credible. Nevertheless, it is important to take into account some limitations of our study.
First, articles were limited to those published in English, which will necessarily exclude potentially relevant studies in other languages. The tendency to publish positive findings over negative results may also introduce some bias. Second, the methods of generating HR estimates and 95% CI varied between studies: there were only two studies which offered these parameters directly, and the extraction of data from the survival curves in other five studies may give rise to inconsistencies. Third, the roles of survivin may vary with its subcellular location [
Despite these limitations, by combining the data from different studies our meta-analysis permits the conclusion that there are significant associations between survivin overexpression and survival rates in patients with OSCC, indicating that survivin may be a potential biomarker for OSCC. Future studies with larger sample sizes and well-designed inclusion criteria will be needed to dissect the role of survivin expression in determining the clinicopathological features and/or prognosis of OSCC.
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We would like to thank the native English speaking scientists of Elixigen Company for editing our manuscript.