ABSTRACT
Objective To investigate the antitumor effects and the possible mechanisms of dendrit-ic cells co-cultured with cytokine-induced killer cells(DC-CIK)in combination with sorafenib on two lung adenocarcinoma cell lines,A549 cells(harboring KRAS gene mutation)and PC-9 cells(harboring EGFR gene mutation). Methods DC and CIK cells were routinely generated in vitro by stimulating PBMCs isola-ted from lung cancer patients with different cytokines and then co-cultured after a week of culturing. Flow cy-tometry analysis(FCM)was used to analyze the phenotype of DC-CIK cells after 7 days of co-culturing. The 50% inhibitory concentration(IC50 )of sorafenib against tumor cells was detected by MTT assay. The tumor cells were treated with DC-CIK cells alone or in combination with sorafenib. The proliferation of tumor cells was tested by CCK-8 kit and dynamically monitored by real-time cellular analysis(RTCA). Annexin-V/ PI staining was used to examine the apoptosis rates in each group. Real-time fluorescent quantitative PCR and FCM were respectively performed to detect the expression of natural killer group 2 member D ligands (NKG2DLs)at mRNA and protein levels after the treatment with sorafenib for 24 h. Results There was no significant difference between the IC50 of sorafenib against A549 and PC-9 cells after a 24-hour exposure(P﹥0. 05). Compared with the DC-CIK biotherapy,treating the tumor cells with DC-CIK cells in combination with sorafenib significantly inhibited the cell proliferation and increased the total apoptosis rates of tumor cells(P﹤0. 05). Moreover,the inhibition rates to tumor cell proliferation were enhanced along with the in-crease of effect-to-target ratio(E/ T). Compared with the single-factor treatment groups,the normalized cell index(NCI)in the combined treatment group was significantly decreased. Blocking NKG2D could abate the inhibitory effect of DC-CIK cells on tumor cell proliferation(P﹤0. 05). The expression of NKG2DLs(inclu-ding ULBP1,UBLP2 and ULBP3)on tumor cells at mRNA and protein levels were increased to different ex-tent after treating with 5 μmol/ L of sorafenib for 24 h. Conclusion There was no significant different be-tween the inhibitory effects of sorafenib on the proliferation of lung adenocarcinoma cancer cells harboring KRAS or EGFR gene mutation. The antitumor effects of DC-CIK cells combined with sorafenib on lung ade-nocarcinoma cells might be induced by regulating the NKG2D-NKG2DLs pathway and enhancing apoptosis. Moreover,the antitumor effects of the combined treatment were better than those of single-factor treatments.