Low abundance of TFPI-2 by both promoter methylation and miR-27a-3p regulation is linked with poor clinical outcome in gastric cancer.

Abstract

The tumor suppressor role of tissue factor pathway inhibitor 2 (TFPI-2) has been reported in various tumors. The present study aimed to improve the understanding of the oncogenic properties of TFPI-2 in gastric cancer. Relative expression of TFPI-2 was determined by a real-time polymerase chain reaction (PCR) and western blotting, respectively. Cell viability was measured via a cell counting kit-8 assay and proliferation was evaluated by a colony formation assay. Cell apoptosis was assessed with a caspase-3 activity kit and invasion was evaluated by a transwell chamber assay. The methylation level of TFPI-2 promoter was assayed by methylation-specific PCR. The regulatory effect of miR-27a-3p on TFPI-2 was analyzed with a luciferase reporter assay. The direct association between miR-27a-3p and TFPI-2 was shown by biotin-labelling pulldown. TFPI-2 was down-regulated in gastric cancer, which associated with an unfavorable prognosis clinically. Ectopic introduction of TFPI-2 greatly compromised cell viability, colony formation and invasive capacity, and also induced cell apoptosis simultaneously. The promoter region of TFPI-2 was extensively methylated in gastric cancer tissues compared to normal tissues, suggesting the epigenetic inhibition of TFPI-2 expression. We further identified that TFPI-2 functioned as sponge RNA against miR-27a-3p. Most importantly, miR-27a-3p-specific inhibitor significantly exerted a tumor suppressor function akin to TFPI-2 itself, and the anti-tumoral activities were completely abolished by TFPI-2 knockdown. We found that the epigenetically suppressed TFPI-2 compromised sponging effects with respect to miR-27a-3p in gastric cancer, which consequently and mechanistically contributed to the tumor biology of gastric cancer.