wnt信号通路对谷氨酰胺酶GLS1表达的表观遗传调控及其在结直肠癌发生中的意义

The development of human cancers is often associated with reprogrammed metabolism such as enhanced glutaminolysis. However, the relevance of glutaminolysis to colorectal carcinogenesis remains largely unclarified. In preliminary studies, we found that glutaminase 1 (GLS1), the rate-limiting enzyme in glutaminolysis, was highly expressed in colorectal carcinoma cells and colorectal tumors in human or mice. Inhibition of GLS1 activity significantly impaired the development of colorectal cancer. However, inhibition of glutaminolysis also inhibited mTOR activity, leading to the activation of prosurvival autophagy. Inactivation of autophagy enhanced growth inhibition induced by GLS1 inhibitor. In addition, we found GLS1 was the target of miR137 which was epigenetically down-regulated in human colorectal cancer cells and colitis-associated colorectal cancer in mice. Knocking-down of β-catenin expression restored miR137 expression to down-regulate GLS1 expression. Moreover, miR137 down-regulation in colorectal cancer was attributed to promoter methylation and transcription factor HSF1 could interact with DNMT3a and miR137 promoter, indicating that HSF1 might recruit DNMT3a to miR137 promoter for DNA methylation. Based on these preliminary findings, we proposed that activated wnt/β-catenin signaling activates HSF1-miR137-GLS1 axis to promote glutaminolysis in colorectal carcinogenesis. To approve this assumption, we will perform a series of in vitro and in vivo experiments to evaluate the dynamic regulation of HSF1-miR137-GLS1 axis in mice with APC deficiency or chemical-induced colitis, define the impact of GLS1 inhibitor on mTOR, explore the function of HSF1 in methylation of miR137 promoter and clarify the clinical relevance of wnt-HSF1-miR137-GLS1 axis to colorectal cancer. By doing so, we believe it could facilitate our understanding in the contribution of metabolism to colorectal carcinogenesis and promote the development of novel strategies for the effective prevention and treatment of colorectal cancer and probably other cancers.

谷氨酰胺代谢在多种肿瘤中发挥重要作用，但在结直肠癌中的作用及调控尚未明确。我们发现谷氨酰胺酶GLS1在人结直肠癌及小鼠自发或诱发肠肿瘤中表达升高，下调其活性可抑制体内外肿瘤生长，但同时抑制mTOR并激活自噬，抑制自噬显著增强GLS1抑制剂的细胞毒作用；wnt通路可上调热休克因子HSF1的表达，而后者可招募DNMT3a到miR137启动子并抑制其转录，使GLS1免受转录后抑制而表达上调。因此，wnt通路可通过HSF1/DNMT3a来抑制miR137转录，上调GLS1表达，激活mTOR信号通路，从而促进结直肠癌发生。我们将通过HSF1敲除小鼠等模型，分析GLS1等在结直肠癌发生中的动态变化，解析wnt通路通过HSF1/DNMT3a促进miR137启动子DNA发生甲基化的分子机制，阐明GLS1抑制剂调控mTOR活性的分子机制，探索靶向谷氨酰胺代谢以干预结直肠癌发生的新方法，为肿瘤防治提供新思路。

谷氨酰胺代谢在多种肿瘤中发挥重要作用，靶向谷氨酰胺代谢因此成为肿瘤治疗的一大潜在策略。但其在结直肠癌中的作用及调控尚未明确。我们发现谷氨酰胺酶GLS1在人结直肠癌及小鼠自发或诱发肠肿瘤中表达升高；抑制谷氨酰胺代谢可抑制体内外肿瘤生长，但同时通过活化ATF4依赖性DDIT3转录来抑制mTOR并激活细胞保护性自噬；抑制细胞自噬则显著增强GLS1抑制剂的细胞毒作用;wnt通路可上调热休克因子HSF1的表达，而后者可招募DNMT3a到miR137启动子并抑制其转录，使GLS1免受转录后抑制而表达上调。本项目通过HSF1敲除小鼠等模型，分析了GLS1等在结直肠癌发生中的动态变化，解析了wnt通路通过HSF 1/DNMT3a促进miR137启动子DNA发生甲基化的分子机制，阐明了GLS1抑制剂调控mTOR活性的分子机制，发现wnt通路可通过HSF1/DNMT3a来 抑制miR137转录，上调GLS1表达，激活mTOR信号通路，从而促进结直肠癌发生。抑制谷氨酰胺代谢可抑制体内外肿瘤生长，但同时通过活化ATF4依赖性DDIT3转录来抑制mTOR并激活细胞保护性自噬；抑制自噬显著增强GLS1抑制剂的细胞毒作用,如果联用门冬酰胺酶则效果更佳。因此，本项目通过探索靶向谷氨酰胺代谢以干预结直肠癌发生的新方法，为肿瘤防治提供了新思路。

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