ELISA study of matrix metalloproteinases 2, 7, 9 and their type 2 tissue inhibitor in the tumors of gastric cancer patients: clinical and pathologic correlations

Background: Over the last 10 years the incidence of gastric cancer has declined significantly. Nevertheless, it remains one of the most prevalent malignancies both in Russia and worldwide. Therefore, the problems of early diagnostics, prognosis and individualized treatment choice are still on the agenda. Much attention is paid to the evaluation of molecular biological characteristics of the tumor, as well as to the development of multiparametric prognostic systems for gastric cancer based on its identified characteristics. An important place among potential tumor biological markers belongs to matrix metalloproteinases (MMPs) involved into all the stages of tumor progression, first of all, into the regulation of invasion and metastasizing.

Aim: Comparative quantitative evaluation of some MMP family members (MMP-2, 7, and 9) and one of the tissue MMP inhibitors (TIMP-2) levels in the tumors and adjacent histologically unchanged mucosa in gastric cancer patients, the analysis of their associations with the main clinical and pathological features of the disease and its prognosis.

Materials and methods: Sixty six (66) primary gastric cancer patients (32 male and 34 female) aged 24 to 82 years (median, 61 year) were recruited into the study. Twenty two (22) patients were with stage I of the disease, 11 with stage II, 28 with stage III, and 5 with stage IV. The concentrations of the proteins studied were measured in the tumor and unchanged mucosa extracts by standard direct ELISA kits (Quantikine®, R&D Systems, USA).

Results: Tumor MMP-2, 7 and 9 levels were significantly increased, compared to those in the adjacent histologically unchanged mucosa, in 80, 70 and 72% of gastric cancer patients, respectively, while the increase of TIMP-2 level found in 61% of the tumors was not statistically significant. Tumor MMP-2 and TIMP-2 content was increasing significantly with higher T index – size and advancement of the primary tumor (p < 0.01 and p < 0.05 respectively). Tumor MMP-2 level was also increasing in parallel with the N index (regional lymph node involvement; p < 0.01); it was significantly higher in the patients with distant metastases than in those without them (p < 0.05). Tumor MMP-9 and MMP-7 concentrations were not significantly associated with the indices of the tumor progression. The patients were followed up for 1 to 85 months (median, 18.3 months). According to the univariate analysis, high (> 32.6 ng/mg protein) MMP-2 and low MMP-7 (< 1.1 ng/mg protein) levels in the gastric cancer tissue represent statistically significant unfavorable prognostic factors for overall survival. Increased TIMP-2 level is associated with a non-significant decrease in the overall survival (p > 0.05), whereas the MMP-9 level was unrelated to the gastric cancer prognosis. Only T index (p = 0.0034) and tumor MMP-7 content (p = 0.026) remained independent prognostic factors in the multivariate regression analysis.

Conclusion: The majority of gastric cancer patients demonstrate a significant increase in the expression of three MMP family members, i.e. gelatinases (MMP-2 and 9), and matrilysin (MMP-7), in the tumors, as compared to adjacent histologically unchanged mucosa. Only MMP-2 levels were associated with the disease progression, increasing with higher TNM system indices. High MMP-2 and low MMP-7 content in the gastric cancer tissue are significant unfavorable prognostic factors for the overall survival in the univariate analysis, but only MMP-7 has retained its independent prognostic value in the multivariate assessment.