OBJECTIVE: This study aims to observe the expression of MHC-class I chain related protein A (MICA) in oral squamous carcinoma cell and explore its effects on NK cells.METHODS: Normal oral mucosa epithelial cell line NOK and oral squamous carcinoma cell lines OEC-M1, SAS and SCC-25 were used in this study. MICA expression in the cells was detected by western blotting and RT-PCR methods, sMICA was detected by ELISA method. The cells were transfected by pEGFP-MICA and pEGFP-NC respectively using Lipofectamine 2000 kit. The transfected cells were co-cultured with NK92 cells. Killing activity of NK92 cells was detected by LDH release method and NKG2D was detected by Flow cytometry. ADAM10 and ADAM17 were detected by ELISA method.RESULTS: MICA expression in OEC-M1, SAS and SCC-25 cells were lower than that of NOK cells (P<0.01), sMICA levels in OEC-M1, SAS and SCC-25 cells were higher than that of NOK cells (P<0.01). Over-expression of MICA in SCC-25 cells could significantly increase the killing activity of NK92 cells (P<0.01), up-regulate NKG2D (P<0.01) and decrease ADAM10 and ADAM17 contents (P<0.01).CONCLUSIONS: MICA expressed lowly in oral squamous cell carcinoma cells, over-expression of MICA could significantly increase the killing activity of NK92 cells, which could be related with the regulation of ADAM.