Reduced Cish expression by siRNA knockdown in Natural Killer cells promotes anti-tumor effects against gastric cancer cell lines.

Improving immune cell functions in tumors remains a main challenge in cancer immunotherapy. NK are main innate effector cells with anti-tumor activity against various tumors. Consequently, NK cells are proper candidates for cancer immunotherapy, including gastric cancer. The IL-15 signaling pathway is negatively regulated by a protein called Cish encoded by the Cish gene. In the present study, we explored the knockdown of Cish and anti-tumor effects of NK cells. We knockdown Cish in human primary NK cells using siRNA, and the expression of Cish was evaluated by qRT-PCR. Gene expression analysis revealed that Cish expression increased after induction by IL-15 at various time point and conversely decreased after knockdown, approximately 44% and 41% reduction were observed at siRNA concentrations of 100 nmol/l at timepoint of 6h and 48h, respectively. Cish knockdown of human NK cells, showed enhanced the anti-tumor effects and induced apoptosis against a human gastric cancer cell lines called MKN-45 and AGS. Additionally, co-culture with MKN-45 and AGS cells showed increased secretion of IFN-γ and TNF-ɑ that could be related to higher cytotoxicity of knockdown Cish NK cells. Our results indicate that Cish knockdown human NK cells enhanced cytotoxicity and cytokine production when co-cultured with gastric cancer cell lines. siRNA-mediated Cish knockdown NK cells, might be a promising immunotherapeutic alternative in patients with gastric cancer.