Nishioka Soichiro, Wu Ping-Hsiu, Yakabe Toshiaki, Giaccia Amato J, Le Quynh-Thu, Aoyama Hidefumi, Shimizu Shinichi, Shirato Hiroki, Onodera Yasuhito, Nam Jin-Min
Molecular and Cellular Dynamics Research, Graduate School of Biomedical Science and Engineering, Hokkaido University, Sapporo, Japan.
Global Center for Biomedical Science and Engineering, Faculty of Medicine, Hokkaido University, Sapporo, Japan.
Neurooncol Adv. 2020 Aug 8;2(1):vdaa091. doi: 10.1093/noajnl/vdaa091. eCollection 2020 Jan-Dec.
Radiotherapy is the standard treatment for glioblastoma (GBM). However, radioresistance of GBM cells leads to recurrence and poor patient prognosis. Recent studies suggest that secretion factors have important roles in radioresistance of tumor cells. This study aims to determine whether Rab27b, a small GTPase involved in secretory vesicle trafficking, plays a role in radioresistance of GBM.
Microarray analysis, cell viability analysis, apoptosis assay, immunostaining, and in vivo experiments were performed to assess the effect of Rab27b on radioresistance of GBM. We further investigated paracrine effects mediated by Rab27b after X-ray irradiation using coculture systems of glioma cell lines.
Rab27b was specifically upregulated in irradiated U87MG cells. Furthermore, Rab27b knockdown decreased the proliferation of GBM cells after irradiation. Knockdown of Rab27b in U87MG cells combined with radiation treatment suppressed orthotopic tumor growth in the mouse brain and prolonged the survival of recipient mice. Interestingly, the co-upregulation of Rab27b and epiregulin (EREG), a member of the epidermal growth factor (EGF) family, correlated with radioresistance in glioma cell lines. Additionally, EREG, which was secreted from U87MG cells via Rab27b-mediated mechanism, activated EGF receptor and contributed to H4 cell proliferation in a paracrine manner.
Our results show that Rab27b mediates the radioresistance of highly malignant GBM cells. Rab27b promotes the proliferation of adjacent cells through EREG-mediated paracrine signaling after irradiation. Thus, the Rab27b-EREG pathway is a novel potential target to improve the efficacy of radiotherapy in GBM.
放射治疗是胶质母细胞瘤（GBM）的标准治疗方法。然而，GBM细胞的放射抗性会导致复发和患者预后不良。最近的研究表明，分泌因子在肿瘤细胞的放射抗性中起重要作用。本研究旨在确定参与分泌囊泡运输的小GTP酶Rab27b是否在GBM的放射抗性中发挥作用。
进行微阵列分析、细胞活力分析、凋亡检测、免疫染色和体内实验，以评估Rab27b对GBM放射抗性的影响。我们还使用胶质瘤细胞系共培养系统，进一步研究了X射线照射后Rab27b介导的旁分泌作用。
Rab27b在受照射的U87MG细胞中特异性上调。此外，Rab27b敲低降低了照射后GBM细胞的增殖。U87MG细胞中Rab27b敲低与放射治疗相结合，抑制了小鼠脑原位肿瘤生长，并延长了受体小鼠的生存期。有趣的是，Rab27b和表皮生长因子（EGF）家族成员上皮调节蛋白（EREG）的共同上调与胶质瘤细胞系的放射抗性相关。此外，通过Rab27b介导的机制从U87MG细胞分泌的EREG以旁分泌方式激活EGF受体并促进H4细胞增殖。
我们的结果表明，Rab27b介导高度恶性GBM细胞的放射抗性。照射后，Rab27b通过EREG介导的旁分泌信号促进相邻细胞的增殖。因此，Rab27b-EREG途径是提高GBM放射治疗疗效的一个新的潜在靶点。
