Glutamine catabolism in c-Myc driven liver tumor development

 简介(申请人提供)：肝细胞癌是全球第五大常见癌症，也是导致癌症死亡的第三大原因。然而，肝细胞癌发生的分子遗传学仍不甚清楚。C-Myc被认为是肝细胞癌的关键癌基因。研究表明，c-Myc驱动的肿瘤细胞依赖谷氨酰胺生存。我们实验室的研究表明，c-Myc驱动的肝肿瘤中谷氨酰胺分解代谢增加。这种表型与谷氨酰胺合成酶(GLUL)的表达降低有关，并从GLS2转换为GLS1谷氨酰胺酶，导致谷氨酰胺酶活性增加。我们还发现，剥夺谷氨酰胺或沉默GLS1会诱导c-Myc驱动的肝癌细胞的细胞死亡。然而，c-Myc驱动的肿瘤发生是否需要谷氨酰胺分解代谢或GLS1的表达，以及谷氨酰胺分解代谢如何整合到异常的肿瘤代谢系统中，还从未在体内进行过研究。在这个应用中，我们假设GLS1在c-Myc驱动的小鼠肝肿瘤的启动和维持中都是必需的。我们将采用一种创新的方法，将流体动力学转染与体内基于miR-30的结构性和诱导性shRNA沉默相结合，确定沉默GLS1表达是否抑制c-Myc驱动的小鼠肝癌的形成(目标1)；以及在c-Myc肿瘤形成后沉默GLS1是否导致肿瘤消退(目标2)。我们将使用表达分析、代谢成像和稳定同位素通量分析来进一步研究我们观察到的表型背后的分子机制。总之，我们提出的研究将是第一个利用活体建模来表征GLS1在c-Myc诱导的肿瘤发生中的功能意义的研究。这项研究将为c-Myc驱动的肝癌发生中的代谢需求提供新的机制洞察力。这也将为GLS抑制剂的开发提供强有力的证据，用于预防和治疗肝癌。由于c-Myc被认为是许多肿瘤的原癌基因，并且c-Myc在多种细胞类型中引起相似的代谢变化，我们的研究很可能对肝癌以外的癌症代谢产生广泛的影响。

 DESCRIPTION (provided by applicant): Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer death worldwide. However, molecular genetics underlying HCC development remain to be poorly understood. c-Myc is considered to be a key driver oncogene for HCC. Studies have shown that c-Myc driven tumor cells depend on glutamine for survival. Studies from our laboratory demonstrated the increased glutamine catabolism in c- Myc driven liver tumors. This phenotype is associated with decreased expression of Glutamine Synthetase (Glul) and switch from GLS2 to GLS1 glutaminase, resulting in increased glutaminase activity. We also showed that depriving glutamine or silencing GLS1 induces cell death in cells derived from c-Myc-driven HCCs. However, whether glutamine catabolism or GLS1 expression is required for c-Myc driven tumorigenesis; and how glutamine catabolism is integrated into the aberrant tumor metabolic system have never been studied in vivo. In this application, we hypothesize that GLS1 is required for both initiation and maintenance of c-Myc driven liver tumors in mice. Using an innovative approach by combining hydrodynamic transfection with miR-30 based constitutive and inducible shRNA silencing in vivo, we will determine whether silencing GLS1 expression inhibits c-Myc driven HCC formation in mice (Aim 1); and whether silencing GLS1 after c-Myc tumor formation induces tumor regression (Aim 2). We will further investigate the molecular mechanisms underlying the phenotypes we observe using expression analysis, metabolic imaging and stable isotope flux assays. Altogether, our proposed study will be the first to characterize the functional significanc of GLS1 in the context of c-Myc induced tumor development using in vivo modeling. The study will provide novel mechanistic insight into the metabolic requirements in c-Myc driven hepatic carcinogenesis. It will also provide strong evidence for the development of GLS inhibitors for HCC prevention and treatment. As c-Myc is considered to be the driver oncogene in many tumors, and c-Myc induces similar metabolic changes in multiple cell types, our study is likely to have broad impact in cancer metabolism beyond HCC.