MicroRNA-21 stimulates gastric cancer growth and invasion by inhibiting the tumor suppressor effects of programmed cell death protein 4 and phosphatase and tensin homolog.

Purpose: MicroRNA-21 (miR-21) is abnormally expressed in many solid cancers, such as gastric adenocarcinoma, and regulates some targets involved in cancer initiation and progression. In this study, we investigated the function of miR-21 in two gastric cancer cell lines, as well as its potential targeting of the tumor suppressor genes phosphatase and tensin homolog (PTEN) and programmed cell death protein 4 (PDCD4).

Methods: The first step was to use quantitative (q) RTPCR in order to verify the overexpression of miR-21 in two different gastric cancer cell lines (SGC-7901 and MKN-45) transfected with mIR-21 mimic. Western blotting confirmed the qRT-PCR data in a set of rescue experiments in which miR-21 mimic, inhibitor, and non specific mimic (NSM) were used to transfect the two gastric cancer cell lines. The protein levels of miR-21 targets PTEN and PDCD4 were estimated. Then, we evaluated its effect on tumor growth and invasion potential on the two different gastric adenocarcinoma cell lines.

Results: qRT-PCR results proved that miR-21 was overexpressed in gastric cancer cells transfected with miR-21 mimic. Western blot results further suggested that PTEN and PDCD4 were regulated by miR-21, as miR-21 inhibitor increased the expression of PTEN and PDCD4 proteins and significantly reduced cell proliferation, migration and invasion. In the control experiment miR-21 mimic significantly inhibited the expression of PTEN and PDCD4 proteins in the two gastric cell lines, leading to an increase in cell invasion and migration. Furthermore, miR-21 mimic inhibited the apoptosis of the two gastric cancer cell lines.

Conclusions: miR-21 is overexpressed in gastric cancer and its aberrant expression may have important role in gastric cancer growth and dissemination by modulating the expression of the tumor suppressors PTEN and PDCD4, as well as by modulating the pathways involved in mediating cell growth, migration, invasion and apoptosis. Targeting miR-21 may help develop novel therapeutics for gastric cancer, once its pathophysiology is completely investigated.