Rac 蛋白與多形性神經膠質母細胞瘤之臨床關聯性分析

Abstract

多型性神經膠母細胞瘤(Glioblastoma multiform，GBM) 為最常見且高侵襲性的原發性腦瘤， 並具高復發率，目前的治療方式為手術切除搭配放射線治療及化學藥物治療。然而預後狀況仍然不理想。 Rac 蛋白質屬於 Rho GTP酶的亞家族成員，其功能為細胞遷移、侵襲和存活，Rac 所調控的訊息傳遞路徑可能導致腫瘤生成。研究發現 Rac 蛋白質在癌幹細胞中扮演維持幹性(stemness)和增生(proliferation)的角色。 本研究利用基因圖譜計畫資料庫(TCGA)中的RNA-Seq、全基因組甲基化圖譜、微型核醣核酸晶片及臨床病患資料等數據探討Rac family表達模式與膠質母細胞瘤的臨床預後關係。 我們使用RNA-seq 來測定Rac family 在GBM的mRNA level，發現GBM病患的Rac1和Rac2表現量跟正常組織相比有顯著的上升，其表現量分別在Proneural、Classical 亞型的存活時間有顯著影響。 在本次實驗中我們探討可能調控Rac 蛋白的機制，我們發現Rac2有5個低甲基化的位點可能與 Rac2 在腦癌中的高表現量有關，而在Rac1及Rac3，則沒有明顯甲基化的差異。 此外在微型核糖核酸分析中，miR-148a、miR-155、miR-34a與Rac家族表現量呈正相關，其表現量對存活時間有顯著影響，因此Rac family 及 miR148a、miR-155、miR-34a有潛力成為多形性神經膠質母細胞瘤的治療策略。Glioblastoma is the most common and aggressive primary brain tumor. One of its malignant characters is high recurrence. The standard treatment is surgical removal combined with radio-chemotherapy. However, the prognosis remains poor. Rac proteins belong to the Rho small GTPase which regulate cell migration, invasion, and survival. All the signaling pathways regulated by Rac may contribute to tumorigenesis. Our previous study had shown that Rac family proteins play an important role in maintaining the stemness and proliferation of glioblastoma stem cells. In this study, we used RNA-seq data, methylation data, microRNA array data , and clinical data obtained from TCGA database to explore the relationship between the expression patterns of Rac (family and the clinical outcomes of glioblastoma. We observed that Rac1 and Rac2 mRNA expression levels were significantly increased in glioblasoma patients compared with solid normal tissue. Glioblastoma patients with high expression levels of Rac1 and Rac2 had significantly shorter overall survival in Proneural and Classical subtype, respectively. Moreover, we observed that several hypomethylated CpG sites in Rac2 of glioblastoma pateints which may account for Rac2 overexpression in these patients.but there are not significant difference in Rac1 and Rac3. In addition, in microRNA analysis, the expression of miR-148a, miR-155, miR-34a was positively correlated with the expression of Rac family. Moreover, these expression patterns had a significant impact on overall survival time. Therefore, Rac family and microRNA miR148a, miR-155, and miR-34a may serve as potential therapeutical targets for glioblastoma multiforme.