The effect of MG132 on the MICA protein stability and NK cell cytotoxicity in breast cancer cell lines

ZHOU Zhifeng; CHEN Shuping; LI Jieyu; LIN Wansong; WANG Ling; ZHENG Qingfeng; YE Yunbin

doi:10.13431/j.cnki.immunol.j.20180073

Abstract：This study was designed to investigate the effect of proteasome inhibitor MG132 on the MHC class I-related molecules A (MICA) stability and NK cell cytotoxicity in breast cancer cell lines. MICA gene of breast cancer cell line was detected; eukaryotic expression vector for MICA allele of breast cancer cell line was constructed and transfected to 293 T cells. The expression of MICA in breast cancer cell line was detected by flow cytometry and Western blotting. MTT assay was used to detect the inhibitory effect of MG132 on the growth of breast cancer cells; LDH was used to detect the killing activity of NK cells. Data showed that MDA-MB-231 gene sequence is MICA* 019/A5, and MDA-MB-435 S gene sequence is MICA*010/A5. There was only a difference in the amino acid at position 29 of the N-terminal (outer membrane) region. MICA*019/A5 is Arg (arginine) at this locus, and MICA* 010/A5 is Pro (proline) at this locus. The Arg or Pro locus is on a beta fold of the protein structure and locates in the middle of the position. MG132 inhibited the proliferation of 293 T cells obviously. After 293 T cells were treated by MG132, MICA expression decreased in MDA-MB-435 S MICA gene-derived 293 T cells and the impact was time-dependent, and the sensitivity to NK cell cytotoxicity was decline. While MDA-MB-231 MICA gene-derived 293 T cells did not show significant changes in MICA expression, and the sensitivity to NK cytotoxicity was not affected. Taken together, NK cell cytotoxicity is closely related to the expression of MICA in breast cancer cells. MG132 affects the stability of MICA in MDA-MB-435 S, and affects NK kill sensitivity, while MDA-MB-231 is not affected by MG132.