Introduction

The incidence of various cancers has been increasing and cancer is the most deadly disease threatening human life. One of the main causes of deaths is the inherent metastatic property of malignant tumors. This poses great difficulty in developing clinical therapeutics. The multi-linked pathological processes of tumor metastasis include: basement membrane degradation, matrix permeability, forward movement of tumor cells including secondary growth, and interaction between tumor cells and host stromal cells. CD147/EMMPRIN, also known as basigin or M6 antigen, has been shown to play an important role in tumor metastasis by stimulating tumor stromal cells to produce matrix metalloproteinases (MMPs) and degrading basement membrane and stroma1.

CD147/EMMPRIN is a member of the immunoglobulin family and is widely expressed in a variety of human tissues and cells1. CD147/EMMPRIN functions to: (1) facilitate secretion of MMP-1, MMP-3, MMP-9 and membrane-type 1-MMP from cancer cells, fibroblasts and endometrial cells, leading to degradation of basement membrane and extracellular matrix, thus promoting tumor proliferation, invasion and metastasis1,2; (2) drive tumor angiogenesis by enhancing MMPs and vascular endothelia growth factor (VEGF) levels in cancer cells and the mesenchyme3; (3) regulate expression and activity of monocarboxylate transporters-1 (MCT-1) and MCT-4, and form complexes on the membrane to transport lactic acid produced by anaerobic glycolysis4; (4) develop chemoresistance in many cancers, probably by mediating activation of phosphatidylinositol 3-hydroxy kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways5,6,7,8; and (5) interact with α3β1, α6β1 integrins to regulate adhesion with extracellular matrix proteins, collagen, laminin or fibronectin and also promote expression of cyclophilin A to induce cancer cell proliferation9. All of these functions are regulated by CD147/EMMPRIN and are summarized in Fig. 1. The outcomes of many of the pathways regulated by CD147 have been associated with the adverse outcomes highlighted in our study.

Figure 1
figure 1

Schematic overview of CD147/EMMPRIN-associated proteins, regulating functional effects at different stages of cancer progression.

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It is highly upregulated in several malignant tumors10,11,12,13,14,15,16,17. A few recent studies10,15,16,17 have revealed a conflicting correlation between CD147/EMMPRIN and various outcomes in different cancers. A meta-analysis of the literature published previously suggests that elevated MCT-4 and CD147 expressions are associated with worse prognosis across many cancer types focusing on the aspect of tumor metabolism while the existing evidence lacks statistical power to draw a convincing conclusion18. The objective of this updated study was to systematically assemble all the existing CD147 literature, link the data to variable outcomes, perform a comprehensive meta-analysis to predict potential prognostic effects in different cancers, and provide further evidence to establish CD147/EMMPRIN as a key player in tumor progression from a number of perspectives.

Results

Our systematic literature search of CD147 and its correlation with different outcomes identified 910 articles. Among these, 836 articles were excluded and only 82 studies satisfied the inclusion eligibility for the meta-analysis. Upon further review of the full text articles, eight additional articles from reference sources were included. An additional 29 studies were excluded due to the following reasons: two articles were reviews; three were duplicate reports; four had insufficient data; four included only a few cases; nine explored the prognostic value of CD147/EMMPRIN in combination with other biomarkers, such as VEGF, MMP-2, CD44s, MCT-1; and seven studies were determined to be too complicated for subgroup analysis. The remaining 53 studies5,6,7,9,10,11,12,13,14,15,16,17,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59 containing 68 datasets that met our inclusion criteria were included in this review (Fig. 2). Among the eligible studies, 33 provided survival information about the correlation of CD147/EMMPRIN expression with tumor prognosis using a multivariate model and 20 presented the same information using a univariate model. The characteristics of these two models are summarized in Tables 1 and 2, respectively.

Table 1 Characteristics of studies exploring the relationship between CD147/EMMPRIN expression and tumor prognosis (Multivariate model).
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Table 2 Characteristics of studies exploring the relationship between CD147/EMMPRIN expression and tumor prognosis (Univariate model) V.
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Figure 2
figure 2

PRISMA 2009 flow diagram showing the article screening and selection process.

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The 53 eligible studies represented 26 different carcinomas or sarcomas and a median number of 204.5 patients (range, 40–600). CD147/EMMPRIN expression in these studies was mainly detected by immunohistochemistry (IHC). One publication had three groups of subjects from different cancers and was therefore considered as three different studies49. Ten publications12,13,14,16,25,29,38,39,51,52 presented two different prognostic results, while one publication31 presented three prognostic results. Some studies also investigated the link between CD147/EMMPRIN and chemotherapy5,6,7 or radiation resistance57. In terms of clinicopathological variables, most of the studies suggested that increased CD147/EMMPRIN expression correlated significantly with higher clinical grade, tumor size, invasion depth, lymphatic invasion, histological grade, and some additional parameters (Table 3).

Table 3 Relationship between CD147/EMMPRIN overexpression and clinical and pathological factors.
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CD147/EMMPRIN and overall survival (OS)

The 44 studies, with data from a total of 5,813 patients, showed that CD147/EMMPRIN expression was associated with worse OS, both in multivariate (meta-hazard ratio (HR) = 1.92; 95% confidence interval (CI): 1.58–2.32) and in univariate models (meta-HR = 1.98; 95% CI: 1.53–2.57) (Table 4; Fig. 3A,B). In addition, separate analysis of solid and non-solid tumors suggested that the OS of solid tumors was significantly associated with CD147 in both multivariate (meta-HR = 1.73; 95% CI: 1.44–2.08) and univariate (meta-HR = 2.06; 95% CI: 1.57–2.70) models. In contrast, OS of non-solid tumors only displayed significant association in the multivariate model (meta-HR = 3.72; 95% CI: 2.23–6.22), while there was no significant association in the univariate model analysis (meta-HR = 1.34, 95% CI: 0.77–2.32) (Table 4).

Table 4 Meta-analysis of association between CD147/EMMPRIN expression and tumor prognosis.
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Figure 3
figure 3

Qualitative meta-analysis of the association between CD147/EMMPRIN over-expression and overall survival (OS) in cancer patients.

Panel A, represents the association of CD147/EMMPRIN positive expression with worse OS in multivariate model, while panel B, represents similar association by univariate model.

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Furthermore, the subgroup analysis of tumors stratified by cancer type also demonstrated a significant association between higher CD147/EMMPRIN expression and adverse outcome of OS for breast carcinoma (meta-HR = 2.92; 95% CI: 1.85–4.60), bladder cancer (meta-HR = 2.32; 95% CI: 1.63–3.29), colorectal cancer (meta-HR = 2.14; 95% CI: 1.38–4.26), ovarian cancer (meta-HR = 1.57; 95% CI: 1.23–2.01) and osteosarcoma (meta-HR = 7.83; 95% CI: 3.18–19.27) in the multivariate model. However, an association was only observed in renal cell carcinoma (meta-HR = 1.87; 95% CI: 1.37–2.56) and bladder carcinoma (meta-HR = 2.51; 95% CI: 1.46–4.33), using the univariate model. In contrast, there was no association in gastric carcinoma (meta-HR = 1.33; 95% CI: 0.99–1.80) and lung cancer (meta-HR = 1.16; 95% CI: 0.63–2.12) (Table 4). We also found a similar association of CD147 with the adverse outcome (OS) in many other cancers, such as adenoid cystic carcinoma of salivary glands, esophageal squamous cell carcinoma, prostate cancer, pediatric medulloblastoma, glioblastoma, gallbladder carcinoma, nasopharyngeal carcinoma, tongue squamous cell carcinoma, endometrial cancer, uterine cervical carcinoma, hepatocellular carcinoma, pancreatobiliary adenocarcinoma, cutaneous squamous cell carcinoma, astrocytomas and soft tissue sarcomas (Supplementary Figure 1A,B).

CD147/EMMPRIN and progression free survival (PFS), metastasis-free survival (MFS) and recurrence-free survival (RFS)

Analysis of 19 studies, with a total of 2,472 patients, showed that CD147/EMMPRIN expression was associated with worse PFS/MFS/RFS, both in multivariate (meta-HR = 2.32; 95% CI: 1.67–3.21) and univariate (meta-HR = 2.18; 95% CI: 1.30–3.63) models (Table 3 and Fig. 4A,B). Moreover, the HR estimates derived specifically from the solid tumors by both models showed a similar pattern of association (multivariate: meta-HR = 2.26; 95% CI: 1.61–3.18; univariate: meta-HR = 2.18; 95% CI: 1.30–3.63). Exclusive analysis of non-solid tumors by a multivariate model suggested a significant association (meta-HR = 3.52; 95% CI: 1.18–10.5) (Table 4).

Figure 4
figure 4

Qualitative meta-analysis of the association between CD147/EMMPRIN over-expression and PFS/MFS/RFS in cancer patients.

Panel (A) represents the overall association of CD147/EMMPRIN positive expression with worse PFS/MFS/RFS in multivariate model; panel (B) depicts similar association in univariate model.

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Similarly, the subgroup analysis of tumors stratified by cancer type again demonstrated a significant association between CD147/EMMPRIN overexpression and adverse outcome of PFS/MFS/RFS in breast carcinoma (meta-HR = 2.50; 95% CI: 1.63–3.83) and ovarian cancer (meta-HR = 1.72; 95% CI: 1.23–2.40) in the multivariate model and renal cell carcinoma (meta-HR = 1.58; 95% CI: 1.34–1.85) in the univariate model. Similar associations were observed in hepatocellular carcinoma, bladder cancer, prostate cancer, colorectal cancer, osteosarcoma, gastric cancer and hypopharyngeal squamous cell carcinoma. However, we did not observe an association in cases of endometrial carcinoma, and the results were not consistent for cervical carcinoma (Supplementary Figure 2A,B).

CD147/EMMPRIN and disease-specific survival (DSS)

Quantitative analysis of five different studies, representing 1,031 patients, linked CD147/EMMPRIN overexpression with DSS in four different solid tumors, namely breast cancer2, colorectal cancer [24, 41], oral squamous cell carcinomas7 and cervical cancer16. Multivariate model analysis established that CD147/EMMPRIN expression was associated with a worse DSS (meta-HR = 1.83; 95% CI: 1.27–2.65) (Table 4; Fig. 5A). Similarly, univariate model analysis indicated that CD147 expression associated with worse DSS (meta-HR = 5.81; 95% CI: 4.16–7.46) (Table 4). This pattern was unchanged even in the subgroup analyses stratified by cancer type. Multivariate model analysis also identified the following associations with DSS: breast carcinoma (meta-HR = 1.70; 95% CI: 1.02–2.84), oral squamous cell carcinoma (meta-HR = 3.89; 95% CI: 1.11–13.71) and colorectal cancer (meta-HR = 2.30; 95% CI: 1.03–5.14). The only cancer for which we did not observe an association was uterine cervical carcinoma (meta-HR =1.23; 95% CI: 0.52–2.90) (Supplementary Figure 4).

Figure 5
figure 5

Qualitative meta-analysis of the association between CD147/EMMPRIN over-expression and disease free survival (DSS) in cancer patients, and to predict easier recurrence of drug resistance.

Panel A, represents the association of CD147/EMMPRIN positive expression with worse DSS in multivariate model. Panels B, represents the potential of CD147/EMMPRIN positive expression to predict easier recurrence of drug resistance.

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CD147/EMMPRIN and chemotherapy drug/radiation resistance

Among the included articles, three studies5,6,7 reported risk for CD147/EMMPRIN overexpression and chemotherapy drug resistance, while only one study57 reported radiation resistance. Quantitative analysis of three articles revealed that positive expression of CD147/EMMPRIN predicted recurrence of drug resistance (meta-OR = 9.30; 95% CI: 2.09–41.30) (Fig. 5B). In addition, CD147/EMMPRIN overexpression appeared to be linked to high risk of radiation resistance (OR = 13.30; 95% CI: 4.38–40.35) in cervical squamous cell carcinomas, although this is just based on one study (Fig. 5C).

Heterogeneity analysis

There was evidence of significant heterogeneity (I2 > 50%) between OS and PFS studies, but not among DSS studies (Table 4). Therefore, the random-effect model was used in all analyses except for the DSS. For the OS and PFS studies, we conducted a meta-regression analysis using publication year, cancer type, sample size, and country as covariates. All covariates were entered into the meta-regression model simultaneously, and the covariates with the highest p values were omitted one at a time to identify sources of heterogeneity. The meta-regression did not identify any of these covariates as a significant source of heterogeneity for OS and PFS studies in multivariate, and indicated that cancer type may be the source of heterogeneity for OS studies in univariate analysis (Coef = 0.093, p = 0.042) (Supplementary Figure 4). Meta-regression was not used for univariate analysis of the PFS since these studies numbered less than 10.

Sensitivity analysis

We also performed a sensitivity analysis to evaluate the effects of individual studies on the pooled HR estimates by omitting one study at a time. The HR estimates for the DSS and PFS/MFS/RFS in the multivariate model were not altered. However, the HR estimates for the OS in the multivariate model, and OS and PFS/MFS/RFS in the univariate model were altered when one, one and two studies were excluded, respectively (data not shown).

Publication bias

To assess confidence in our study, we performed a publication bias analysis using the funnel plot and Egger’s and Begg’s rank correlation tests. There was no significant publication bias in both models for the DSS and PFS/MFS/RFS groups (Table 4; Fig. 6D–F). In the case of the OS group, the univariate model (Table 4; Fig. 6C) suggested no publication bias, but in the multivariate model, results were inconsistent based on the p value obtained by Begg’s rank test (0.05) and Egger’s test (0.007) (Table 4; Fig. 6A). These test results were nonparametric and therefore the Trim and Fill method was used to further verify this analysis. After filling the deleted studies (square dots), we found no obvious asymmetry in the funnel plot (Fig. 6B). Thus, the HR estimates for the prognostic value of CD147/EMMPRIN were not notably altered (data not shown). This suggests that there was no publication bias even in the OS group in the multivariate model.

Figure 6
figure 6

Assessment of publication bias for OS, DSS, and PFS/MFS/RFS studies.

Panel (A) depicts the assessment of publication bias for multivariate model studies, by funnel plot analysis, whereas panel (B) shows funnel plot analysis using nonparametric Trim and Fill method. Panel (C) represents the publication bias in univariate model studies. Panel (D) represents the assessment of publication bias for multivariate model. Panels (E,F) represents assessment of publication bias for multivariate and univariate model studies, respectively.

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Discussion

CD147/EMMPRIN is a glycosylated, multifunctional molecule that participates in tumor progression61. In the present study, we quantitatively analyzed the data from 53 studies, including 68 datasets, to examine the associations between CD147/EMMPRIN expression and its prognosis predictive value in cancer. Previous studies have suggested that combination of CD147/EMMPRIN with other factors, especially VEGF60,62,63 and MMP-264,65,66, can predict the prognosis of some cancers. Here, we exclusively studied the role of CD147/EMMPRIN in tumor prognosis. Our meta-analysis revealed that the prognosis in three adverse outcomes was significantly poor in cases with CD147/EMMPRIN overexpression. This was further confirmed in subgroup analyses of tumors stratified by cancer type. Meanwhile, the predictive role of CD147/EMMPRIN in cervical cancer and hepatocellular carcinoma prognosis has been controversial and its result in cervical carcinoma, endometrial carcinoma, pancreatobiliary adenocarcinoma and some additional tumors did not consistently reach significance. However, the sample size and studies in our stratified analysis were small, and our findings should be further verified.

CD147/EMMPRIN has been shown to be involved in the regulation of tumor cell invasion, metastasis, angiogenesis, anti-apoptosis, adhesion and facilitation of drug resistance through its association with various proteins1, such as MMP-219, MMP-920, Ki-6714, VEGF19, microvessel density19, C-erbB-212, S100A431, a disintegrin and metalloproteinase 1732, lewis y antigen6, fascin43, caveolin-148, hypoxia inducible factor 1 alpha9, cyclophilin A9, CD44v654, cyclooxygenase-254, receptor for activated C kinase 155 and metabolism related factors like MCT-156, MCT-456, and glucose transporter -157. However, there is some conflicting literature refuting associations with paxillin42, syndecan-142, and MMP-2 and MMP-922. In addition, CD147 expression has been proposed to inversely correlate with estrogen and progesterone expression10,12. Furthermore, CD147/EMMPRIN was positively associated with clinicopathological variables in most studies (Table 3). It is speculated that CD147/EMMPRIN interacting with many proteins representing various molecular or biological pathways contributes to malignant progression, eventually causes adverse clinical outcomes.

Previous meta-analyses didn’t explore any significant association between CD147/EMMPRIN and susceptibility of radio-chemotherapy. In the view of more studies are warranted to validate CD147/EMMPRIN association with chemotherapy and radiation resistance prediction5,6,7,57. It has been suggested that chemotherapy drugs combined with CD147-targeted therapy may increase the sensitivity of tumor cells to several different chemotherapeutics, and can result in more effective inhibition of tumor proliferation and recurrence7,67. Our study also established that increased CD147/EMMPRIN expression is linked to high risk of drug resistance and our preliminary analysis linked CD147 to radiation resistance. It follows that CD147/EMMPRIN has been proposed to be an important potential therapeutic target.

The results of the present study must be interpreted with caution due to the presence of substantial heterogeneity. In addition, there were several limitations in this study. First, the composition of the cancer type or stage varied between studies, and the detection and corresponding cut-offs varied. For instance, some studies only included pediatric patients26 while others included older patients10. Also, in non-small-cell lung cancer, CD147/EMMPRIN was associated with poor survival in patients with adenocarcinoma only, but not with squamous cell carcinoma22. The scoring criteria were also inconsistent. Second, the follow-up time varied across studies, which may have contributed to the non-homogeneity of prognostic information. Sensitivity analysis results also showed instability within individual articles. Third, this study was based on published articles only and, since negative data are hard to publish, there could be publication bias, which is an inherent limitation of all meta-analyses, irrespective of outcomes from the Egger’s linear regression test and Begg’s rank correlation test.

Conclusion

In summary, this meta-analysis indicated that higher expression of CD147/EMMPRIN potentially may be a prognostic marker for most cancers, and thus can serve as a potential therapeutic target. We further verified that CD147/EMMPRIN had a complex role in tumor progression by crosstalk with numerous factors. However, additional multicenter prospective studies are warranted to confirm these findings, especially in various types of tumors.

Methods

Study identification

We searched PubMed and Embase databases through March 2015 to identify relevant studies for inclusion in our meta-analysis. The following keywords were used in the literature searches; “CD147”, “extracellular matrix metalloproteinase inducer”, “EMMPRIN”, “basigin”, “survival”, “prognosis”, “tumor”, “cancer”, “carcinoma”, “neoplasm”, or their combinations. Eligible articles were selected based on title, abstract and full text. If the same patient cohort was reported in multiple publications, only the most complete and most recent publication was selected. We also searched of the reference lists from electronically identified articles.

Inclusion and exclusion criteria

Based on the Reporting Recommendations for Tumor Marker Prognostic Studies (REMARK) guidelines, we included studies that met all of the following criteria: (1) written in English; (2) reported quantitative outcomes from prognostic association studies of tumor and CD147/EMMPRIN; (3) described outcomes as overall survival (OS), disease-specific survival (DSS), progression-free survival (PFS), metastasis-free survival (MFS) or recurrence-free survival (RFS), depending upon the study; (4) had a minimum of 40 case numbers describing prognosis; (5) provided a detailed protocol, including the source of raw materials, methodology, quantification methods, and scoring criteria; (6) precisely defined the time-to-event outcome, time to follow-up, and the median follow-up time; and (8) data were presented as the estimated hazard ratios (HRs) with 95% confidence intervals (CIs) or in the case where HRs or 95% CIs were not reported directly, a calculation was used to determine if the conditions of the study were suitable for inclusion68. Multivariate analyses were used for statistical analysis biomarkers that had independent prognostic factors for cancers after adjusting for one or more additional standard clinical prognostic variables like age, pathology, stage, grade, lymphatic metastasis or other biological marker variables. Studies were excluded if they were case reports, case-only studies, letters, reviews, reported insufficient data, lacked statistical analysis, combined with other factors, or were duplicate studies. All studies were independently reviewed by two authors, and in a case of conflict a third author resolved the issue after thorough discussion.

Data collection and analysis

We assessed heterogeneity using the Chi2 test and I2 test69. If heterogeneity was present, meta-regression was used to determine the source. We combined data from different trials using a fixed-effect model when there was no significant heterogeneity in populations (I2 < 50%) and a random-effect model when there was considerable heterogeneity. If heterogeneity was present, meta-regression was used to determine the source. Variables were synthesized using HR/OR. By convention, an overall HR (OR) > 1 with a 95% CI implied a poor outcome (high risk) for the group with either positive or negative biomarker expression. The high HR value corresponded with poor survival. To evaluate the effects of individual studies on the pooled HR estimates, we performed a sensitivity analysis omitting one study at a time. The statistical significance was set at 0.05. We used funnel plot asymmetry using Egger’s linear regression test and Begg’s rank correlation test to assess the publication bias. If both test results were inconsistent, Nonparametric Trim and Fill method was used to verify the results70. A P value of <0.05 suggested significant publication bias. All statistical analyses were performed using STATA 12.0 (StataCorp, College Station, TX) statistical software.

Additional Information

How to cite this article: Xin, X. et al. CD147/EMMPRIN overexpression and prognosis in cancer: A systematic review and meta-analysis. Sci. Rep. 6, 32804; doi: 10.1038/srep32804 (2016).