MiR-152-5p as a microRNA passenger strand special functions in human gastric cancer cells.

Gastric cancer (GC) is one of the most common malignancies with high mortality rate. MiR-152 may exert the function of tumor suppressor by regulating its target gene, including PIK3CA. Nevertheless, all of the described functions are referred explicitly to miR-152-3p, while miR-152-5p as a passenger strand is poorly realized and entirely ignored. We previously selected miR-152-5p as a candidate using cell migration inhibition screening for GC cells and predicted that miR-152-5p might also target PIK3CA. In this study, we found an abnormal proportion of miR-152-3p / miR-152-5p in GC (gastric cancer) tissues and cells and demonstrated that miR-152-5p had poorer stability in GC cells, revealing the possibility that miR-152-5p is abnormally "suppressed" in gastric cancer. We also investigated and confirmed the role of miR-152-5p in GC by a series of experiments, and found that miR-152-5p modulated cell viability, migration, invasion, and cell-cycle progression of human GC cells, and also inhibited tumor growth and metastasis partially by targeting PIK3CA. More interestingly, it was proved that miR-152-3p and miR-152-5p had synergistic effects on the inhibition of PIK3CA in GC cells. The results of this study suggest that miR-152-5p may act as a tumor suppressor in SGC-7901 gastric cancer cells via targeting PIK3CA. Further, the study provides a novel insight into the roles of miRNA* during carcinogenesis.