IFN-γ基因转染抗大肠癌细胞的作用机制

Effect of expression of interferon-γ gene in inhibition of growth of colon cancer cell

目的:通过检测IFN-γ基因转染对大肠癌细胞表面抗原的表达情况、对细胞的生长抑制、细胞周期的影响情况,初步探讨IFN-γ基因治疗抗肿瘤作用的机制.方法:制备含人IFN-γ基因的真核表达质粒pcDNA-3-IFN-γ,利用阳离子脂质体将其转染进入人大肠癌细胞株LOVO、SW62O、HCT116BG及人宫颈癌细胞株Hela,检测基因转染后IFN-γ基因的表达情况,同时检测基因转染对大肠癌细胞CEA、HLA-DR抗原表达的诱导作用和细胞凋亡及细胞周期的变化.结果:基因转染后,原来高表达CEA的细胞株(LOVO、HCT116BG)其上清中CEA含量增加明显(从21.25±6.76μ/l增加到34.96±7.07μg/lP<0.05),而原来低表达甚至不表达CEA的细胞株(Hela、SW620)其上清CEA含量则无明显增加(P>0.05).各细胞株表面的HLA-DR的表达量在导入IFN-γ基因后明显增强(平均表达率从3.91±3.61%增加到11.67±7.20%P<0.01).通过对细胞的凋亡情况和细胞周期的变化显示:转染IFN-γ基因后促进了LOVO细胞的凋亡(各时段平均凋亡率对照组与治疗组分别为8.27±5.62%与15.32±11.41%P<0.05),细胞的S期比例随作用时间延长而呈逐渐降低趋势,显示了基因转染后DNA的合成代谢受到抑制.结论:IFN-γ基因转染后可有效增强大肠癌细胞表面抗原的表达,诱导机体产生抗肿瘤免疫应答;并可能通过抑制细胞DNA的合成,促进细胞的凋亡,抑制肿瘤细胞的增生等机制发挥抗肿瘤作用.

AIM:To investigate the effect of expression of interferon-γ (IFN-γ) in tumor cell and its inhibitory effect on the growth of tumor cell. METHODS:pcDNA3-IFN-γ vector containing IFN- γ gene was constructed and transfected into LOVO, SW620, HCT116BG and Hela cell lines by lipofectamine, respectively. The ex- pression of IFN-γ, CEA and HLA-DR in transfected cells were tested.Both the number of apoptosis of and the proportion of cell cycles of tumor cells were measured to investigate the anti-tumor effect of IFN-γ gene therapy. RESULTS:LOVO and HCT116BG transfected cell lines had high expression of CEA, the average level of CEA was signifi- cantly increased from 26.02±6.76 to 38.85±7.07 μg/l ( P <0.05). However, there was no detectable increase in the superna- tants of Hela, SW620 cell lines that naturally expressed little of CEA. Flow cytometry analysis showed that HLA-DR ex- pression rate (11.67±7.20) was significantly higher than that prior gene transfection (3.91±3.61) (P <0.01), and the IFN-γ gene transfer effectively induced the apoptosis of tu- mor cells, the proportion of DNA synthesis phase was de- ceased gradually after IFN-γ gene transfer, which indicated that the synthesis of DNA and growth of tumor cells were repressed. CONCLUSION:IFN-γ gene therapy enhanced the expres- sion of antigens on cell surface and thus induced powerful antitumor immunity. Repressing of synthesis of DNA, in- ducing the apoptosis of tumor cells and inhibiting the prolif-eration of tumor cells might be anti-tumor mechanisms of IFN-γ.