调控Wip1基因表达靶向增敏放疗对脑肿瘤干细胞的作用

Gliomas are the most common primary human brain tumors. p53 pathway is a key regulator of glioma cell responses to DNA damage induced by radiation，and the p53 status determines the sensitivity of glioma cells to radiation. Wild-type p53-induced phosphatase 1 (Wip1) belongs to the Ser/Thr PP2C family of phosphatases.Wip1 is a newly found oncogene, can suppresso the activity of p53 and is up-regulated after radiation. Our prior discovery indicated that Wip1 is selectively over-expressed in gliomas with wild-type p53 and plays an important role in the proliferation in glioma cells. Wip1 acts as a key regulator to DNA damage and repair., is another factor that determine the cells are repaired or apoptotic when they are demaged. Brain tumor stem cells have been identified in gliomas and CD133 was identified as a marker for them. It was demonstrated that CD133+ cells contribute to glioma radio-resistance via preferential activation of DNA damage checkpoints and increase after radiation. Wip1 is related with proliferation and growth of stem cells, but the expression of Wip1 and the roles after radiation in brain tumor stem cells have not been reported yet. Our study intends to increase the sensitivity of brain tumor stem cells to radiation by controlling the expression of Wip1 to induce the differentiation of brain tumor stem cells. Our study with further reveals the mechanisms of glioma radio-resistance and provides a promising target for therapeutic intervention of glioma.

脑胶质瘤是最常见的原发颅内肿瘤。p53信号通路与胶质瘤放疗所致DNA损伤修复密切相关，不同p53状态的胶质瘤对放疗的敏感性不同。丝氨酸/苏氨酸家族成员Wip1是一种新发现的癌基因，可以调节p53的功能，在放射损伤时显著上调。我们发现在胶质瘤中选择性过表达的Wip1基因与野生型p53的胶质瘤细胞生长密切相关。Wip1基因在DNA损伤修复中起重要作用，是决定细胞损伤后修复还是凋亡的一个重要因素。胶质瘤中少数的脑肿瘤干细胞是胶质瘤放疗抵抗的根源，并且放疗可能增加脑肿瘤干细胞的比例。Wip1基因与肿瘤干细胞的增殖和生长密切相关，但Wip1基因在脑肿瘤干细胞中表达及其对放疗的作用尚未见报道。本研究拟通过调控Wip1基因在脑肿瘤干细胞中的表达有效实现脑肿瘤干细胞的分化进而达到放疗增敏作用。通过本项目的实施，将帮助我们进一步认识胶质瘤放疗抵抗的机制，有望为胶质瘤的治疗提供新的靶点。

脑胶质瘤是最常见的原发颅内肿瘤。p53信号通路与胶质瘤放化疗所致DNA损伤修复密切相关，不同p53状态的胶质瘤对放疗的敏感性不同。丝氨酸/苏氨酸家族成员Wip1是一种新发现的癌基因，可以调节p53的功能，可能与胶质瘤的放化疗耐受相关。在胶质瘤中选择性过表达的Wip1基因与野生型p53的胶质瘤细胞生长密切相关。本课题通过靶向沉默Wip1基因在胶质瘤中的表达，发现Wip1基因沉默可以抑制胶质瘤细胞的生长并增加凋亡。Wip1在胶质瘤中的作用可以通过去磷酸化p53使其失活，也可以通过抑制p38MAPK及调节p14ARF的作用间接作用于p53.因此Wip1对胶质瘤的生长具有重要的作用。本项目将Wip1基因沉默的胶质瘤细胞再予以放疗，结果发现Wip1基因沉默可以显著增加胶质瘤细胞对放疗所致的凋亡，抑制细胞生长。Wip1基因沉默的胶质瘤细胞予以放疗干预后表现为显著的Chk1、Chk2蛋白表达降低。同时我们通过靶向沉默Wip1基因并协同替莫唑胺作用胶质瘤U-87MG细胞，并观察其细胞生物学变化。结果发现Wip1基因沉默的胶质瘤细胞接受替莫唑胺处理后更多的细胞停留在细胞分裂的G2期，表现为显著的细胞增殖抑制和凋亡增加。通过基因芯片扫描发现，Wip1基因沉默并协同替莫唑胺作用后，与对照组相比表现为367个基因上调和444个基因下调，最具有显著影响的通路是肿瘤通路。蛋白表达检测证实肿瘤通路中MAPK8 和PIK3R1蛋白表达上调而RB1的表达下调。Wip1基因沉默可以显著增加胶质瘤细胞对替莫唑胺的敏感性，并且这种作用可能与PIK3/Akt信号通路的作用有关。本项目证实Wip1基因在胶质瘤的放化疗中起重要的调节作用及其作用途径，有望通过对Wip1基因的作用实现逆转胶质瘤细胞的放化疗耐受,为胶质瘤的治疗提供新的靶点