双基因干扰对MCF-7细胞基因表达抑制及细胞凋亡影响的研究

背景与目的：肿瘤细胞具有端粒酶高表达及端粒稳定性强两大特点。人端粒酶逆转录酶（hTERT@是端粒酶的催化亚单位,端粒重复序列结合因子2（TRF2@对维持端粒长度及端粒稳定性非常重要。本实验研究针对hTERT和TRF2的特异性RNAi腺病毒表达载体单独和联合转染乳腺癌MCF-7细胞后,对两基因的抑制效率以及对细胞凋亡的影响,探索针对端粒的多基因干扰对乳腺癌基因治疗的可行性。方法：构建RNA干扰腺病毒载体rAd-hTERT和rAd-TRF2,单独和联合转染MCF-7细胞后实时荧光定量PCR检测hTERT和TRF2基因表达情况,流式细胞仪检测各组细胞凋亡率。结果：①转染后48h,与PBS组相比,rAd-hTERT对hTERT基因mRNA的抑制率约86%,对TRF2基因表达无明显抑制（P〉0.05@;rAd-TRF2对TRF2基因mRNA的抑制率约80%,对hTERT基因表达无明显抑制（P〉0.05@;rAd-hTERT/rAd-TRF2联合干扰组对hTERT基因表达抑制率约88%,TRF2基因表达抑制率约85%,联合干扰与单基因干扰相比,对hTERT和TRF2基因的表达抑制差异无显著性（P〉0.05@。②干扰组转染后1～6d均能促进细胞凋亡。单基因干扰组转染后3～5d凋亡最明显,第5天达凋亡高峰;凋亡率rAd-hTERT组为46.2%,rAd-TRF2组为43.5%。联合组转染后第1天凋亡率为46.2%,第2天为68.5%,第3～6天均维持在较高水平,第6天达77.6%。转染后1～6d,联合干扰细胞凋亡率与单基因干扰细胞凋亡率相比,差异均有显著性（P〈0.05@。结论：①rAd-hTERT和rAd-TRF2转染MCF-7细胞48h后可分别显著抑制hTERT和TRF2基因mRNA表达,但rAd-hTERT和rAd-TRF2在抑制hTERT和TRF2基因mRNA表达上无相互协同或相互抑制作用。②rAd-hTERT和rAd-TRF2均能有效促进MCF-7细胞凋亡,且两者联合干扰效果具有累加效应。因此利用联合干扰技术靶向抑制端粒酶活性和端粒稳定性相关的多基因的表达能更高效地促进乳腺癌细胞凋亡,抑制肿瘤细胞的增殖与生长。

The inhibition of hTERT and TRF2 gene expression and inducing cells apoptosis by adenovirus-mediated hTERT/TRF2 RNA interference in MCF-7 cells

Background and purpose: High expression of telomerase and telomere stability are two common features in tumor cell. hTERT is a catalytic subunit of telomerase, TRF2 is extremely important to maintain the length and stability of telomerase. This study was to construct the recombinant adenovirus mediated shRNA to hTERT and TRF2, and to investigate the inhibitory effects of the vector by solo-inhibiting and connect-inhibiting in the MCF-7 cells, in order to present a new approach to the gene therapy for breast cancer. Methods: rAd-hTERT and rAd-TRF2 were constructed and the expression of hTERT mRNA and TRF2 mRNA were tested by FQ-PCR 48 hours after transfecting in MCF-7 cells. Apoptosis was observed by flow cytometry 1 to 6 days after transfection. Results: ①At 48 hours after transfection, the results of FQ-PCR showed that compared to PBS group, the expression of hTERT in rAd-hTERT group was obviously decreased and the inhibition ratio was about 86%, but TRF2 had not been obviously inhibited (P>0.05);the expression of TRF2 in rAd-TRF2 group was obviously decreased and the inhibition ratio was about 80%, but hTERT had not been obviously inhibited (P>0.05);in rAd-hTERT/rAd-TRF2 group, the inhibition ratio of hTERT and TRF2 were about 88% and 85%. Comparing rAd-hTERT/rAd-TRF2 group with rAd-hTERT group and rAd-TRF2 group, there were no significant differences of inhibition ratio between hTERT gene and TRF2 gene(P>0.05). Otherwise, comparing rAd-HK group, rAd-blank group with PBS group, there were no significant differences of inhibition ratio between hTERT gene and TRF2 gene(P>0.05). ②The result of flow cytometry showed that apoptosis was induced at the first day after transfecting in rAd-hTERT group and rAd-TRF2 group, the most obvious apoptosis was in the 3rd to 5th days,at the peak in the 5th day, and decreased in the 6th day after transfection. The apoptosis ratio of rAd-hTERT group was 46.2%, rAd-TRF2 group was 43.5%. The apoptosis ratio of rAd-hTERT/rAd-TRF2 group was 46.2% at first day, 68.5% at the second day, the most obvious apoptosis was in the 3rd to 6th days and was 77.6% in the 6th days in rAd-hTERT/rAd-TRF2 group. There were significant differences in apoptosis ratio in solo-inhibiting and connect-inhibiting(P<0.05). In addition, comparing rAd-HK group, rAd-blank group with PBS group, there were no significant differences in apoptosis ratio(P>0.05). Conclusion: ①Target sequence of RNAi which aimed at hTERT gene and TRF2 gene was designed efficiently, and the RNAi expression vectors were seen in vivo study efficiently and specifically inhibited the correspond gene expression and promoted cell apoptosis in MCF-7 cells. ②rAd-hTERT vector and rAd-TRF2 vector have no synergistical effect and antagoinstical effect on inhibiting hTERT gene and TRF2 gene mRNA expressing in MCF-7, but there was synergistical effect in terms of the induction of apoptosis. So association-RNAi-technique targeting to the genes of telomere length and stability can effectively promote tumor cell into apoptosis and inhibit breast cancer cell growth. RNAi technique of connecting correlation genes is a more effective gene therapy strategy.