Jiang Yuanpei, Sheng Hongling, Meng Lei, Yue Hongsheng, Li Bo, Zhang Aijun, Dong Yanan, Liu Yuguang
Department of Neurosurgery, Ji'nan Central Hospital Affiliated to Shandong University, Liberate Road No. 105, Ji'nan, 250013, China.
Department of Pediatrics, Shandong Jiaotong Hospital, Central Wuying Hill Road No. 12, Ji'nan, 250031, China.
World J Surg Oncol. 2017 Jan 6;15(1):9. doi: 10.1186/s12957-016-1084-1.
Gliomas are one of the most common malignant brain tumors and bring a big threat to human life as traditional therapy is unsatisfactory. RBM5 was a RNA-binding motif protein and was reported as a tumor suppressor. But the role of RBM5 in gliomas was unknown.
The mRNA level of RBM5 was determined in gliomas tissues and cell lines by real-time quantitative PCR (qRT-PCR) assay while the association of RBM5 expression with prognosis was analyzed by Kaplan-Meier method and compared by log-rank test. Lentivirus was used to overexpress RBM5 in gliomas cells. MTT and BrdU incorporation assay were used to determine cell proliferation and DNA synthesis when the ability of cell migration and invasion was analyzed by transwell assay with/without Matrigel. Cell apoptosis rate was determined with fluorescence-activated cell sorting (FACS) method. Then, expression of apoptosis molecules and critical members in Wnt/β-catenin pathway were detected by western blot analysis.
RBM5 was shown to be downregulated in gliomas tissues and gliomas cell lines. And decreased RBM5 expression was clinically correlated with tumor stage, patient age, and poor prognosis of gliomas patients. The proliferation and DNA synthesis was dramatically inhibited when RBM5 was overexpressed in SHG44 or U251 cells. Also, the ability of cell migration and invasion was disrupted. Then, the level of β-catenin and Cyclin D1 significantly decreased when DKK1 and P-GSK-3β increased reversely in SHG44 cells, which suggested that RBM5 inhibited canonical Wnt/β-catenin signaling. Meanwhile, we demonstrated that caspase3-mediated apoptotic pathway was activated by RBM5 as Bax, TNF-α, and cleaved caspase3 were greatly upregulated while antiapoptotic molecule Bcl-2 was downregulated. Additionally, that apoptotic rate increased significantly from less than 1 to 32% in RBM5-overexpressed SHG44 cells further supported the pro-apoptosis role of RBM5 in gliomas cells.
RBM5 plays a suppressor role in human gliomas by inhibiting Wnt/β-catenin signaling and inducing cell apoptosis. This study improves our knowledge about the carcinogenesis and progression of human gliomas, which would greatly contribute to the therapy for gliomas patients.
胶质瘤是最常见的恶性脑肿瘤之一，由于传统治疗效果不理想，对人类生命构成巨大威胁。RBM5是一种RNA结合基序蛋白，被报道为一种肿瘤抑制因子。但RBM5在胶质瘤中的作用尚不清楚。
通过实时定量PCR（qRT-PCR）检测胶质瘤组织和细胞系中RBM5的mRNA水平，采用Kaplan-Meier法分析RBM5表达与预后的关系，并通过对数秩检验进行比较。利用慢病毒在胶质瘤细胞中过表达RBM5。采用MTT和BrdU掺入法检测细胞增殖和DNA合成，同时通过有无基质胶的transwell实验分析细胞迁移和侵袭能力。用荧光激活细胞分选（FACS）法测定细胞凋亡率。然后，通过蛋白质免疫印迹分析检测凋亡分子和Wnt/β-连环蛋白通路关键成员的表达。
RBM5在胶质瘤组织和胶质瘤细胞系中表达下调。RBM5表达降低与肿瘤分期、患者年龄及胶质瘤患者预后不良在临床上相关。当RBM5在SHG44或U251细胞中过表达时，细胞增殖和DNA合成受到显著抑制。此外，细胞迁移和侵袭能力也被破坏。然后，在SHG44细胞中，当DKK1和P-GSK-3β反向增加时，β-连环蛋白和细胞周期蛋白D1水平显著降低，这表明RBM5抑制经典Wnt/β-连环蛋白信号通路。同时，我们证明RBM5激活了caspase3介导的凋亡途径，因为Bax、TNF-α和裂解的caspase3显著上调，而抗凋亡分子Bcl-2下调。此外，在过表达RBM5的SHG44细胞中，凋亡率从不到1%显著增加到32%，进一步支持了RBM5在胶质瘤细胞中的促凋亡作用。
RBM5通过抑制Wnt/β-连环蛋白信号通路和诱导细胞凋亡在人类胶质瘤中发挥抑制作用。本研究提高了我们对人类胶质瘤发生和进展的认识，将对胶质瘤患者的治疗有很大帮助。
