靶向TRF2/NRSF信号通路抑制胶质瘤干细胞增殖及肿瘤生长

Glioma brain tumors harbor a small population of cancer stem cells that are resistant to conventional chemotherapeutic and radiation treatments, and are believed responsible for tumor recurrence and mortality. The identification of the epigenetic molecular mechanisms that control self-renewal of glioma stem cells will foster development of targeted therapeutic approaches. The transcriptional repressor NRSF, best known for its role in controlling cell fate decisions in neural stem cells, may also be crucial for cancer stem cell self-renewal. Our hypothesis is NRSF could be selectively targeted for proteasomal degradation by inhibition of TRF2, resulting in suppression of CD133+ glioma stem cell proliferation and tumor growth. In addition to protecting telomeres, TRF2 possesses a novel role in stabilization of REST that is required for controlling glioma stem cell fate. Neurological side effects of treatments that target TRF2 and NRSF signaling pathway may be less severe than conventional brain tumor treatments because postmitotic neurons have relatively stable telomeres and express little NRSF. Combining a NRSF/TRF2-based treatment with low doses of existing chemotherapeutic agents might further improve the outcome in patients with glioma.

胶质瘤干细胞（GSC）与肿瘤的持续增长及复发密切相关，它具有放化疗耐受性，是治疗的一个重要靶点。本课题将证明，神经限制性沉默因子（NRSF）是调控GSC命运的重要分子开关，抑制端粒重复序列结合因子2（TRF2）的表达，减少TRF2与NRSF的结合，导致NRSF经蛋白酶体降解，可以启动GSC从自我复制向终末分化或衰老死亡转化，最终抑制GSC增殖和肿瘤生长，并提高其放化疗敏感性。本研究体外采用TRF2特异性shRNA下调GSC中内源TRF2表达，观察GSC自我复制、增殖分化、衰老死亡及放化疗敏感性的变化，并阐明其分子机制。体内采用动物脑内成瘤实验，观察干预TRF2/NRSF信号通路对GSC体内成瘤的影响。靶向TRF2/NRSF信号通路的治疗，与胶质瘤常规疗法相比，对成熟神经元和胶质细胞无不良影响，神经系统副作用小。本课题不仅有助于阐明GSC自我复制的分子机制，而且开辟了胶质瘤靶向治疗的新方向。

胶质母细胞瘤是最常见的原发性脑肿瘤，患者在诊断后存活期约为2年左右。胶质母细胞瘤中所含有的具有自我更新能力的胶质瘤干细胞（GSCs）常常抵抗化疗和放疗。胶质瘤干细胞高表达神经限制性沉默因子（NRSF），可能是其抵抗常规治疗的原因之一。端粒重复序列结合因子2（TRF2）具有稳定端粒结构的功能，同时NRSF在维持神经干细胞和肿瘤细胞的自我更新中发挥重要作用。本研究体外采用病毒载体转导TRF2特异性shRNA下调从患者标本中分离的GSCs内源TRF2表达，减少TRF2与NRSF的结合，导致NRSF经蛋白酶体降解，进而显著抑制GSCs的增殖，同时上调有丝分裂后成熟神经元相关蛋白（L1CAM和B3微管蛋白）的表达。本研究表明抑制TRF2表达可使GSCs从自我复制向终末分化转化，增加GSCs对目前广泛用于胶质母细胞瘤治疗的DNA烷化剂替莫唑胺的敏感性，体内免疫缺陷小鼠颅内成瘤实验表明靶向TRF2可显著提高动物存活率。本研究揭示了TRF2在维持GSCs依赖于NRSF的增殖和化疗耐药中的作用，表明TRF2是胶质母细胞瘤治疗的潜在靶点。