多基因共沉默对鼻咽癌细胞裸鼠移植瘤影响的研究

Effect of silencing VEGF, c-myc, survivin and hTERT by multiple shRNA expression vectors on the xenografted human nasopharyngeal carcinoma in nude mice

目的 应用基因克隆技术构建一个载体同时编码四个不同基因的真核表达质粒,并与单基因质粒作对比,通过裸鼠成瘤实验研究其对体内鼻咽癌细胞CNE-2Z生长增殖的影响.方法 构建同时表达血管内皮生长因子（VEGF）、致癌基因蛋白（c-myc）、存活素（survivin）和端粒酶反转录酶（hTERT）并含荧光素标记的短发夹RNA质粒（命名为P-1）,并构建单独表达VEGF、c-myc、survivin 和hTERT的质粒（分别命名为P-2、P-3、P-4和P-5）,建立人鼻咽癌细胞CNE-2Z细胞株裸鼠皮下接种模型,分别将其转染于荷瘤裸鼠瘤体内,以激光共聚焦显微镜观察质粒在瘤体内的转染及表达情况.反转录聚合酶链反应（RT-PCR）在mRNA水平上检测对目的基因表达的抑制作用,免疫印迹法在蛋白水平上检测对目的基因的封闭效果.脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL法）检测各组移植瘤细胞凋亡率.结果 所有裸鼠均接种成功,l周左右可见皮下肿瘤形成,并随时间延长不断增大.各质粒组载体转入瘤体后,共聚焦显微镜下见癌组织中有绿色荧光表达,而空白对照组未见绿色表达荧光.肿瘤体积生长曲线表明,单基因组和多基因组肿瘤生长明显受到抑制,以多基因组肿瘤体积抑制最为明显.肿瘤抑制率在Pl～5组分别为82.4%、46.2%、48.5%、51.9%和46.8%.RT-PCR和免疫印迹法在体内实验证实单基因质粒组主要引起单个基因mRNA和蛋白的表达下降,而多基因质粒组可以同时下调四个不同基因mRNA和蛋白的表达,TUNEL实验表明多基因质粒能更有效地促进肿瘤细胞凋亡,抑制肿瘤的生长.结论 多基因共沉默对鼻咽癌基因治疗有着潜在的应用前景,同时阻断多个基因可能是恶性肿瘤基因治疗的一个希望所在.

Objective To investigate the effects of multiple short hairpin （shRNA） expression vectors, targeting VEGF, c-myc, survivin and hTERT, genes on the xenografted human nasopharyngeal carcinoma （CNE-2Z） in nude mice. Methods The shRNA expression vectors were constructed and subsequently transfected by direct injections into the tumors formed by CNE-2Z cells implanted in nude mice. The expressions of the targeted genes in tumor tissues and the apoptosis of tumor cells were evaluated.Results NPC CNE-2Z cells were successfully inoculated and subcutaneous tumor was formed in all nude mice. Under fluorescence microscope, tumor tissues showed the expression of each vector with green fluorescence. The expression of multiple shRNAs led to the decreases in the expressions of VEGF, c-myc,survivin, hTERT mRNA and proteins. Multi-gene silencing was better than single gene silencing in inducing the apoptosis of tumor cells. Tumor growth curves showed that the tumors treated with the shRNAs, including VEGF, c-myc, survivin, hTERT or the combination of 4 shRNAs, growed slowly obviously compared with control tumors. Inhibited rates of tumor growth by VEGF-, c-myc-, survivin- and hTERT-shRNA were 46. 2%, 48. 5%, 51.9% and 46. 8% respectively. The combined application of 4 shRNA produced the more significant inhibatory rate （82. 4% ） than single shRNA application. Conclusions The application of vector-based RNAi targeting multiple genes is a promising therapeutic modality in the gene therapy of nasopharyngeal carcinoma and multi-gene silencing is a new strategy for tumor therapy.