反义表皮生长因子受体cDNA转染对胶质母细胞瘤端粒酶活性的影响

Effect of antisense epidermal growth factor receptor cDNA transfection on telomerase activity of glioblastomas cells

目的:探讨反义表皮生长因子受体(epidermalgrowthfactorreceptor, EGFR)cDNA转染对胶质母细胞瘤细胞株U87MG端粒酶活性和端粒长度的影响及其机制。方法:用反义EGFRcDNA转染胶质母细胞瘤细胞株U87MG后,筛选出低表达EGFR的细胞株;用telomericrepeatamplificationprotocolassay(TRAP分析)检测肿瘤细胞的端粒酶活性;用Southern印迹杂交方法检测端粒长度;用半定量RT PCR方法检测端粒酶逆转录酶(humantelomerasere versetranscriptase, hTERT)、端粒酶相关蛋白1(humantelomerase associatedprotein1, hTEP1)和c myc基因的表达。结果:反义EGFRcDNA转染胶质母细胞瘤U87MG后,其EGFR蛋白表达量明显降低;肿瘤细胞生长缓慢,对EGF的生长刺激作用,反应明显减弱;肿瘤细胞的端粒酶活性明显降低,端粒长度显著缩短;hTERT的mRNA表达量略微降低,而hTEP1和c myc的mRNA表达量未见明显改变。结论:反义EGFRcDNA转染胶质母细胞瘤可以有效阻断EGFR信号传导通路,降低肿瘤细胞的端粒酶活性,使端粒长度缩短,这可能是抑制肿瘤细胞生长的新机制;反义EGFRcDNA转染降低hTERTmRNA的表达,可能是其降低端粒酶活性的机制之一。

Objective: To study the effects of antisense epidermal growth factor receptor (EGFR) cDNA transfection on telomerase activity and telomere length of glioblastomas U87MG cells and the mechanism. Methods: Glioblastoma U87MG cells, which over-expressed EGFR, were transfected with antisense-EGFR cDNA constructs. Several clones stably expressing lower or undetectable levels of EGFR protein were obtained. The effect of antisense-EGFR cDNA on telomerase activity was assessed by Telomeric Repeat Amplification Protocol (TRAP) assay. The effect of antisense- EGFR cDNA on telomere length was determined by Southern blot hybridization. The mRNA expressions of hTERT, hTEP1 and c-myc were analyzed by semi-quantitative PCR. Results: U87MG cells that were transfected with antisense-EGFR cDNA expressed lower level of EGFR and were less responsive to the growth stimulation of EGF compared with the control cells. Telomerase activity was significantly decreased in the antisense-EGFR clones. Telomere length was shortened. The mRNA expression of hTERT was slightly decreased in the antisense-EGFR clones, whereas the expressions of hTEP1 and c-myc were not altered. Conclusion: Antisense-EGFR cDNA transfection can sufficiently inhibit EGFR signal transduction pathway, decrease telomerase activity and shorten telomere length, which may be a new mechanism of antisense-EGFR approach in tumor suppression. The down-regulation of hTERT mRNA may contribute to the decreased telomerase activity in the antisense-EGFR clones.