GEFT调控Rho GTPases信号通路在横纹肌肉瘤侵袭转移中的作用机制研究

Rhabdomyosarcoma (RMS) is the most common childhood malignant soft tissue tumor. In addition to onset location, clinical stage and histologic type, its prognostic factors also include fusion gene, gene amplification or deletion, and chromosomal changes, which can induce tumor invasion and metastasis. In our preliminary work, we found a high level of guanine nucleotide exchange factor T (GEFT) amplification in rhabdomaysarcoma using array comparative genomic hybridization (aCGH) and further confirmed the overexpression of GEFT protein by immunohistochemistry. Moreover, we found that the overexpression of GEFT is closely correlated with the metastasis and prognosis of RMS. Recent studies have shown that the guanine nucleotide exchange factor (GEFs) mediated Rho GTPases signaling pathway is correspond with mesenchymal tumor metastasis and mesenchymal epithelial transformation (MET)/ epithelial mesenchymal transformation (EMT). It is thus suggested that the GEFT may be involved in the formation and development of rhabdomaysarcoma by regulating Rho GTPases pathway. In order to clarify the detailed function and molecular mechanism of GEFT/Rho GTPases pathway and to identify critical molecules of MET/EMT in the invasion and mestasis of rhabdomyosarcoma, we plan to first investigate the expression of GEFT and MET-related genes in rhabdomyosarcoma and their relationships with tumor grade, clinical stages and prognosis; Second, we will investigate the invasion and metastasis of rhabdomaysarcoma cell and the possible mechanism of GEFT mediated Rho GTPases pathway and MET-related genes by cellular experiments. Finally, we plan to further evaluate key genes related with the GEFT-mediated Rho GTPases signaling pathway by using mice model of rhabdomyosarcoma and find the key molecules affecting its invasion, metastasis prevention. We believe that this study will lay the foundation for the metastasis prevention and molecular targeted therapy of rhabdomyosarcoma.

横纹肌肉瘤（RMS）是儿童最常见的软组织恶性肿瘤,其预后因素除发病部位、临床分期和组织学类型外，还与融合基因形成、基因扩增或缺失等染色体改变所致的侵袭转移有关。我们的研究证实RMS中存在Rho家族鸟苷酸交换因子（GEFs）成员GEFT基因的扩增，且其高表达与RMS的转移和预后密切相关。而目前研究显示，GEFs调节的Rho GTPases通路可以激活效应分子引起肿瘤发生间叶上皮转化（MET/EMT）。因此，我们推测GEFT可能通过调控Rho GTPases通路导致肿瘤发生MET/EMT从而在RMS的侵袭转移中发挥重要作用。本项目拟在探讨GEFT、MET相关基因与RMS临床病理分期、分级及预后间关系的基础上，建立细胞和小鼠模型进一步研究GEFT介导的Rho GTPases通路及MET相关基因在RMS侵袭转移中的作用与机制，并寻找影响侵袭转移的关键分子，为RMS的转移预防和靶向治疗奠定基础。

横纹肌肉瘤是儿童最常见的软组织恶性肿瘤,其预后因素除发病部位、临床分期和组织学类型外，还与融合基因形成、基因扩增或缺失等染色体改变所致的侵袭转移有关。我们的研究证实横纹肌肉瘤中存在Rho家族鸟苷酸交换因子（GEFs）成员GEFT基因的扩增，且其高表达与横纹肌肉瘤的转移和预后密切相关。GEFT基因过表达能增强横纹肌肉瘤细胞的增殖、迁移、侵袭和抗凋亡能力；而GEFT基因沉默能减弱横纹肌肉瘤细胞的增殖、迁移、侵袭和抗凋亡能力；同时，裸鼠实验证明GEFT基因可促进裸鼠皮下横纹肌肉瘤细胞移植瘤的形成和转移的发生；Rac1、Cdc42基因过表达能增强横纹肌肉瘤细胞的增殖、迁移、侵袭和抗凋亡能力，其抑制剂能抑制横纹肌肉瘤细胞的生物学行为；因此，GEFT基因可能在横纹肌肉瘤的生长和侵袭转移过程中发挥重要作用且通过调控Rac1/Cdc42信号通路来影响横纹肌肉瘤的发生发展。同时体外实验初步证实横纹肌肉瘤中存在EMT/MET现象，且GEFT可能通过激活Rac1/Cdc42-PAK1信号通路促进EMT/MET过程，进而促进横纹肌肉瘤的增殖、侵袭及迁移。上述研究结果为横纹肌肉瘤的转移预防和靶向治疗奠定了坚实的基础。