siRNA沉默p75神经营养因子受体逆转胶质瘤恶性表型

Study on reversion of malignant phenotype of glioma by siRNA targeting p75 neurotrophin receptor

目的 利用小干扰RNA（siRNA）技术沉默与胶质瘤细胞凋亡和侵袭密切相关的p75神经营养因子受体（p75NTR）基因,观察其逆转胶质瘤恶性表型的治疗效果.方法 设计靶向p75NTR基因的siRNA片段,脂质体转染人U251胶质瘤细胞系,逆转录聚合酶链反应（RT-PCR）和免疫细胞化学方法 检测p75NTR的mRNA和蛋白表达;Transwell细胞侵袭实验检测U251细胞的侵袭力;软琼脂集落形成实验检测细胞集落形成能力;建立裸鼠颅内U251胶质瘤荷瘤模型,原位重复注射siRNA-p75NTR/脂质体复合物3次,MRI检测颅内瘤体积,免疫细胞化学SP法检测p75NTR、神经生长因子（NGF）和细胞周期蛋白（cyclin）D2表达,用TUNEL法做移植瘤细胞原位细胞凋亡检测.结果 转染siRNA基因片段的U251细胞p75NTR mRNA和蛋白质表达水平显著下降（P〈0.05）,细胞侵袭能力及软琼脂集落形成能力均显著降低（P〈0.05）;体内实验显示p75NTR的表达程度与NGF的表达呈正相关,与cyclin D2表达及原位细胞凋亡数量呈负相关,MRI示瘤体积增长缓慢,边界轮廓清晰,动物生存期明显延长（P〈0.05）.结论 靶向p75NTR的siRNA技术可有效降低胶质瘤细胞的侵袭及增殖能力,诱导肿瘤细胞凋亡.

Objective To study the therapeutic efficacy of siRNA fragments silencing p75 neurotrophin receptor （p75NTR）, which may be a key regulator of glioma cell apoptosis and invasion.Methods The siRNA sequence fragments targeting p75NTR were designed and transferred into human glioma cell line U251. RT-PCR and immuocytochemistry method were used to explore the expression of p75NTR mRNA and protein. Cell adhesion assay was employed to detect cellular adhesion ability, and soft agar clone formation assay was adopted to identify oncogenicity, and a U251 glioma model was established in nude mice.The intracranial tumor volume was detected by MRI. The expression of p75NTR, NGF and cyclin D2 were identified using immunohistochemistry. Cell apoptosis was detected by apoptosis kit in situ. Results The siRNA fragments targeting p75NTR were capable of decreasing mRNA and protein expression of p75NTR in U251 glioma cell line. Both the cellular adhesion ability and oncogenicity were weakly relevant. The p75NTR expression level was negatively correlated with cyclin D2 and apoptosis, and positively correlated with NGF expression. The siRNA sequence fragments targeting p75NTR were effective in decreasing the gross volume of tumor;prolonged the survival time of mice, and the edge of tumor was much sharper than that of the control group. Conclusions The gene silencing technique by siRNA targeting p75NTR is capable of decreasing tumor invasion and cell proliferation as well as inducing cell apoptosis. It is expected to be a new choice for glioma gene therapy.