Matrix metalloproteinase-7 may serve as a novel biomarker for cervical cancer

Abstract

Background: The biological and clinical significance of matrix metalloproteinase-7 (MMP-7) in cervical cancer remains unknown. Here, we investigated the function of MMP-7 in cervical cancer cells and evaluated its clinical significance in both tissues and serum from cervical cancer patients.

Methods: First, we analyzed the expression of MMP-7 in cervical cancer using Oncomine microarray data and examined its expression in cervical tissues by quantitative real-time polymerase chain reaction and Western blotting. Second, we utilized gene silencing to explore the role of MMP-7 in cells. Finally, we examined the MMP-7 levels in patients with cervical cancer and normal serum by enzyme-linked immunosorbent assay. Moreover, we further investigated the relationship between MMP-7 expression and pathological features.

Results: The mRNA and protein MMP-7 levels were higher in cervical cancer tissues than in healthy controls. Silencing of MMP-7 significantly decreased cervical cancer cell proliferation, migration, and invasion. The serum MMP-7 levels were significantly higher in cervical cancer patients than in healthy subjects (P<0.01). Further, higher MMP-7 expression was associated with increased lymph metastasis (P=0.021), pathological grade (P=0.039, P=0.047), and clinical stage (P=0.049, P=0.046).

Conclusion: MMP-7 appears to act as an oncogene in cervical cancer cells and is involved in cell proliferation, migration, and invasion. MMP-7 expression was significantly higher in the tissue and serum of cervical cancer patients compared to healthy individuals and was correlated with increased pathalogical grade, clinical stage, and lymph metastasis. Therefore, our data provide novel evidence that MMP-7 may be a clinically relevant biomarker for cervical cancer.

Keywords: biomarker; cervical cancer; invasion; matrix metalloproteinase-7; migration.

Figure 1

Expression of matrix metalloproteinase-7 (MMP-7) is significantly upregulated in cervical cancers. Notes: (A) MMP-7 mRNA expression is upregulated in cervical squamous cell carcinoma tissues compared with normal cervical tissues, as revealed by the Oncomine Biewenga Cervix dataset. (B) MMP-7 mRNA expression is upregulated in cervical squamous cell carcinoma tissues compared with cervical squamous epithelium, as revealed by the Oncomine Scotto Cervix dataset. (C) MMP-7 mRNA expression is upregulated in cervical squamous cell carcinoma tissues and high-grade squamous intraepithelial neoplasia compared with normal cervical tissues, as revealed by the Oncomine Zhai Cervix dataset. (D) Relative mRNA expression levels of MMP-7, as determined by quantitative real-time polymerase chain reaction, in 15 pairs of cervical cancer tissues and paracancerous tissues. (A–D) Values are presented as the means ± standard error of the mean; ^**P<0.01. (E) Western blot analysis of MMP-7 expression in 9 pairs of cervical cancer samples and normal controls. C represents cervical cancer tissues and N represents normal control tissues. (F) Densitometric analysis of these results, using β-actin as a loading control.

Figure 2

Silencing of matrix metalloproteinase-7 (MMP-7) significantly decreases MMP-7 expression. Notes: Silencing of MMP-7 in Hela (A) and Caski (C) cells significantly decreased the expression of MMP-7 protein as detected by Western blot analysis. The results were normalized to β-actin expression, as shown in B and D. siRNA-1: 5′-ACC CAT TTG ATG GGC CAG GAA-3′; siRNA-2: 5′-TGC AGT GAT GTA TCC AAC CTA-3′.

Figure 3

Silencing of matrix metalloproteinase-7 (MMP-7) suppresses cervical cancer cell proliferation in vitro. Notes: The proliferation of Hela (A) and Caski (B) cells in the control and siRNA-1 and siRNA-2 groups was determined by Cell Counting Kit-8 (CCK8) assay at 0, 24, 48, and 72 h. Values are presented as the mean ± standard error of the mean; n=5. ^**P < 0.01. siRNA-1: 5′-ACC CAT TTG ATG GGC CAG GAA-3′; siRNA-2: 5′-TGC AGT GAT GTA TCC AAC CTA-3′.

Figure 4

Silencing of matrix metalloproteinase-7 (MMP-7) suppresses cervical cancer cell migration in vitro. Notes: Representative wound healing images of Hela (A) and Caski (C) cells at 0 and 24 h. The dotted black lines outline the cell boundary. Magnification 200×. Wound healing rates were quantified in both Hela (B) and Caski (D) cells. Data are presented as the mean ± standard error of the mean; ^*P<0.05; ^**P<0.01. siRNA-1: 5′-ACC CAT TTG ATG GGC CAG GAA-3′; siRNA-2: 5′-TGC AGT GAT GTA TCC AAC CTA-3′.

Figure 5

Silencing of matrix metalloproteinase-7 (MMP-7) suppresses cervical cancer cell invasion in vitro. Notes: (A and C) Representative invasion images from MMP-7-silenced and control cells. Original magnification: 200×. (B and D) Quantification of cells on the lower surface of the membrane was performed with 3 randomly selected fields. Data are presented as the means ± standard error of the mean; ^**P<0.01. siRNA-1: 5′-ACC CAT TTG ATG GGC CAG GAA-3′; siRNA-2: 5′-TGC AGT GAT GTA TCC AAC CTA-3′.

Figure 6

Matrix metalloproteinase-7 (MMP-7) is highly expressed in the serum of cervical cancer patients. Notes: (A) Comparisons between serum MMP-7 concentrations in healthy people and cervical cancer patients. (B) Comparisons between serum squamous cell carcinoma antigen (SCC-Ag) concentrations in healthy people and cervical cancer patients. (C) Receiver operating characteristic (ROC) curve analysis was performed to predict the clinical value of MMP-7, SCC-Ag, and MMP-7+SCC-Ag levels in cervical cancer prediction. ^**P < 0.01.

Figure 7

Analysis of correlation between matrix metalloproteinase-7 (MMP-7) expression and clinical data. Notes: (A) Serum MMP-7 levels in patients with lymph metastasis compared to those without lymph metastasis. (B) Serum MMP-7 levels in patients with pathology grade 3, or grades 1 or 2 compared with healthy individuals. (C) Serum MMP-7 levels in patients with clinical stage I or II, or III or IV, compared with healthy individuals. (D) Serum MMP-7 levels in patients with tumor invasion depth >0.5 compared to patients with tumor invasion depth ≤0.5. (E) Serum MMP-7 levels in patients with tumors ≥2 cm compared to those with tumors <2 cm. (F) Serum MMP-7 levels in patients with vascular invasion compared to those without vascular invasion. Data are presented as the mean ± standard error of the mean; ^*P<0.05; ^**P<0.01. Abbreviation: NC, no sense.