Glutamine catabolism in c-Myc driven liver tumor development

 描述（由申请人提供）：肝细胞癌（HCC）是全球第五大常见癌症和第三大癌症死亡原因。然而，HCC发生的分子遗传学基础仍然知之甚少。c-Myc被认为是HCC的关键驱动癌基因。研究表明，c-Myc驱动的肿瘤细胞依赖于谷氨酰胺存活。我们实验室的研究表明，c-Myc驱动的肝肿瘤中谷氨酰胺催化剂增加。该表型与谷氨酰胺合成酶（Glul）的表达降低和从GLS 2转换为GLS 1谷氨酰胺酶相关，导致谷氨酰胺酶活性增加。我们还表明，剥夺谷氨酰胺或沉默GLS 1诱导来自c-Myc驱动的HCC的细胞中的细胞死亡。然而，谷氨酰胺催化剂或GLS 1表达是否是c-Myc驱动的肿瘤发生所必需的;以及谷氨酰胺催化剂如何整合到异常的肿瘤代谢系统中从未在体内研究过。在本申请中，我们假设GLS 1是小鼠中c-Myc驱动的肝肿瘤的启动和维持所需的。通过将流体动力学转染与体内基于miR-30的组成型和诱导型shRNA沉默相结合的创新方法，我们将确定沉默GLS 1表达是否抑制小鼠中c-Myc驱动的HCC形成（目的1）;以及在c-Myc肿瘤形成后沉默GLS 1是否诱导肿瘤消退（目的2）。我们将进一步研究的分子机制，我们观察到的表型使用表达分析，代谢成像和稳定同位素通量测定。总而言之，我们提出的研究将是第一个使用体内建模在c-Myc诱导的肿瘤发展的背景下表征GLS 1的功能意义。该研究将为c-Myc驱动的肝癌发生的代谢要求提供新的机制见解。这也将为开发GLS抑制剂预防和治疗HCC提供有力的证据。由于c-Myc被认为是许多肿瘤中的驱动癌基因，并且c-Myc在多种细胞类型中诱导类似的代谢变化，因此我们的研究可能对HCC以外的癌症代谢产生广泛影响。

 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.