Effect and mechanism of RNAi targeting WWTR1 on biological activity of gastric cancer cells SGC7901

Gastric cancer (GC) is one of the most common malignancies in the world. It is essential to develop novel targets and therapeutic approaches for GC, which requires identification of novel functional molecules. WW-domain containing transcription regulator 1 (WWTR1) may activate many transcriptional factors and exhibit an important role in the development of various tissues in mammals. The results of the present study demonstrated that mRNA and protein levels of WWTR1 are increased in GC tissues and cell lines. The SGC7901 cell line was selected to perform RNA interference (RNAi) targeting WWTR1, and for subsequent study. Compared with control groups (cells without any treatment) and mock groups (cells treated with nonspecific siRNA), cell proliferation of siWWTR1 cells (cells treated with WWTR1 siRNA) was detected using a Cell Counting Kit-8 assay at 12, 24 and 48 h, and decreased in a time-dependent manner. Cell cycle and apoptosis status were determined by flow cytometry, and it was demonstrated that G1/S transition was blocked in the cell cycle and apoptosis promoted in siWWTR1 cells, compared with control and mock cells. Reverse transcription-quantitative polymerase chain reaction and western blotting were performed to detect the mRNA and protein levels of cell cycle and apoptosis-associated factors. The expression of Cyclin D1, cancer Myc and B cell lymphoma/leukemia-2 (Bcl-2) decreased and Bcl-2 associated X protein increased significantly in siWWRT1 cells, at the mRNA and protein level, compared with control and mock cells. With the exception of the Hippo pathway, siWWTR1 regulated downstream factors, including mothers against decapentaplegic homolog family member 3 (SMAD3) and inhibitor of DNA binding 1, HLH protein (ID1), HLH protein in the transforming growth factor (TGF)-β pathway. The expression of asparagine synthetase was decreased whereas ID1, SMAD3 (proteins that participate in intracellular TGF-β transduction) and betacellulin increased notably in siWWRT1 cells. In conclusion, WWTR1 promotes cell proliferation and inhibits apoptosis of GC cells by regulating cell cycle/apoptosis-associated factors, and effectors in the TGF-β pathway.