缺氧微环境下ZEB2/RBMX通过调控SCAP的可变剪接促进胶质母细胞瘤脂代谢重塑的机制研究

Lipid remodeling is an important feature of the metabolism alterations of glioblastoma (GBM), which is closely related to the malignant progress of tumor and resistance to radiotherapy and chemotherapy. We previously found upregulated lipid metabolism in hypoxic GBM cells, but the specific mechanism remains unknown. It is known that oncogene ZEB2 is upregulated by hypoxia key factor HIF-1α.Bioinformatics analysis and preliminary experiments showed that ZEB2 may interact with RBMX, and the lipid droplet accumulation in GBM cells will be decreased after ZEB2 knockdown. Moreover, RBMX has multiple binding sites with exon 17 of SCAP. Exon 17 skipping of SCAP inhibits the activation of SREBP-1, a key lipid synthesis factor in GBM cells, and this process can be reversed by hypoxia . Therefore, this project intends to use transgenic technology, CoIP, ChIP, FRET, isotope lipid labeling, in vitro and in vivo experiments to confirme that HIF-1α upregulates ZEB2 to regulate the splicing pattern of SCAP through interaction with RBMX, and then activate SREBP-1-mediated de novo fatty acid synthesis, leading to the accumulation of lipid droplets within the GBM. This project will elucidate a key molecular mechanism of GBM lipid metabolism remodeling, and provide new therapeutic targets for the control of GBM recurrence.

脂代谢重塑是胶质母细胞瘤（GBM）代谢改变的重要特征，与肿瘤恶性进展及放化疗抵抗密切相关。我们前期发现缺氧的GBM细胞脂代谢通路异常激活，但具体机制不明。已知癌基因ZEB2受缺氧关键因子HIF-1α的调控。生信分析及预实验表明，ZEB2与RBMX可能为相互作用蛋白，干扰ZEB2后GBM细胞脂滴堆积下降。且RBMX与SCAP第17号外显子有多个结合位点，SCAP第17号外显子跳跃的剪接模式抑制了GBM细胞脂质合成关键因子SREBP-1的激活，而此过程能够被缺氧所逆转。据此，本项目拟利用转基因技术、CoIP、ChIP、FRET、同位素脂质标记、体内外功能实验，证实在缺氧微环境下HIF-1α通过上调ZEB2的表达，促进RBMX对SCAP剪接模式的调控，激活SREBP-1介导的脂肪酸从头合成，导致GBM内脂滴的堆积。本项目将阐明GBM脂代谢重塑的一个关键分子机制，为控制GBM复发提供新的治疗靶点。

异常的脂质合成能力增强是胶质母细胞瘤代谢重塑的重要特征之一，也是维持肿瘤细胞的生存、侵袭以及干细胞特征的重要代谢途径，其具体的调控机制有待于进一步探究。本项目中，我们发现缺氧微环境下，胶质母细胞瘤的脂质堆积可能和ZEB2的升高相关。进一步地，我们在体内外实验中，通过荧光染色与非靶向脂质组学证实ZEB2可通过促进FASN升高调控肿瘤细胞内不同脂质成分的含量，特别是饱和脂肪酸，进而导致了细胞内膜流动性降低，细胞膜生长信号与免疫抵抗信号的富集。而后蛋白质质谱与转录组学数据的联合应用，证实去泛素化酶CYLD受ZEB2的转录调控且与FASN相互结合，在敲除CLYD的细胞模型中，我们发现FASN的稳定性降低，表明CYLD可能介导了ZEB2对FASN的调控作用。总而言之，本项目在体内外实验的证据中提出ZEB2是胶质母细胞瘤代谢重塑的关键靶向分子，并证实了其通过CYLD-FASN轴介导的脂质成分变化的机制。本项目研究期间资助发表期刊论文6篇，并为胶质母细胞瘤的发生发展和临床靶向提供了新的视角。