Activated NK cells against human hepatocellular carcinoma cell lines in vitro and in vivo

AIM: To evaluate the role of natural killer(NK) cells against a variety of human hepatocellular carcinoma (HCC) cell lines in vitro and in vivo, and to investigate the expression of MHC class I chain-related protein (MIC protein) in these HCC cell lines. METHODS: Peripheral blood mononuclear cells (PBMC) were isolated from 50 mL peripheral blood donored by a healthy volunteer and cultured in the NK cell kit followed by amplification and cytokine activation. The release of lactate dehydrogenase (LDH) was detected by lysis experiment. Animal experiments were performed following vaccination with HCC cell lines (BEL7402, HepG2 and SMMC7721) in BALB/c-nu/nu mice. The diameters of the tumors were measured and the growth curves of difference cell lines were delineated. Three weeks later, these mice were sacrificed and the weight of the transplanted tumors was also detected. Furthermore, the expression of MIC protein was determined. RESULTS: The obvious differences of lysis effects of NK cells on different cell lines were observed, in which the lysis effect of NK cells on K562 cells was the strongest, the effect on BEL7402 cells was in the middle and the effect on SMMC7721 cells was the weakest. In animal experiments, NK cells also showed obvious and different restraining effects on a variety of HCC cell line-transplanted tumors in nude mice. The tumor inhibitory rates of NK cells were 43.5% in BEL-7402 cell-transplanted tumor, 40.7% in HepG2 cell-transplanted tumor and 36.0% in SMMC-7721 cell-transplanted tumor. The protein expression of MIC was 48.7%, 32.8% and 0.9% in the 3 cell lines,respectively. CONCLUSION: The lysis effects of NK cells on a variety of human HCC cell lines are different. The expression of MIC in the tumor cells may play distinct role in evaluating these differences.