Tumor Suppressing Pathways in Kidney Cancer

 描述(由申请人提供)： 肾透明细胞癌(CcRCC)是军人，特别是40岁以上男性，包括退伍军人的严重健康问题。根据1995-2004年国防医学流行病学数据库，第4个十年以后专门针对军人的RCC发病率急剧增加到8.5，而总体发病率为每10万人年1.5例。我们的实验室研究了von Hippel-Lindau(VHL)蛋白调节的分子通路，VHL蛋白是ccRCC中最常丢失的肿瘤抑制因子。在之前的资助期间，我们发表了关于自噬在ccRCC生长中的作用的重要数据。这种竞争性的更新建立在这些实质性观察的基础上。自噬是一种体内平衡功能，细胞通过这种功能处理自己的细胞器和蛋白质，以消除缺陷分子和循环营养物质。在肿瘤生长过程中，许多癌症会沉迷于自噬作为一种营养来源。此外，自噬被不同的癌症疗法激活，导致对治疗的抵抗，并促进自噬抑制剂、氯喹衍生物在联合疗法中的使用。MAP1LC3(Lc3)是形成自噬小体所必需的蛋白质。在我们最近发表的工作和初步结果中，我们发现两个LC_3B和LC_3C对CCRCC的生长有相反的影响。Lc3B依赖的自噬促进VHL缺失的肾癌细胞形成的肿瘤生长，而Lc3B依赖的自噬抑制VHL(-)细胞的生长。这项建议侧重于调查，以了解依赖LC3C的自噬的活性。最重要的是，我们发现了氧化(限速酶，葡萄糖6-磷酸脱氢酶，G6PD)和非氧化性(转酮醇酶，TKT)戊糖磷酸途径(PPP)降解酶的自噬作用靶标是LC3C，而不是LC3B。LC3c的作用是PPP特异性的，不影响糖酵解途径。这一重要的癌症途径产生核糖-5-磷酸，用于生产核酸，产生NADPH，用于脂质合成和谷胱甘肽的还原，所有这些都能促进细胞的生存和生长。KIRC TCGA发表的非监督分析进一步支持了我们数据的重要性，该分析显示G6PD和TKT水平与ccRCC的不良预后显著相关。这一提议的主要假设是，由于HIF的作用而导致的VHL的丢失降低了Lc3c，从而允许激活PPP来支持肿瘤的生长。在目标1中，我们将确定VHL诱导LC3C基因表达的分子机制。我们的工作假设是，HIF通过诱导抑制转录因子的表达来抑制LC3C。在目标2中，我们将利用遗传和代谢组学的方法，确定Lc3c在PPP的氧化和非氧化分支在控制核酸合成和NADPH生成中的作用。在目标3中，我们将确定PPP的氧化和非氧化分支在人肾癌原位移植瘤生长和PPP酶表达中的作用。在目标4中，我们将确定LC3C而不是LC3B专门针对TKT和G6PD进行自噬降解的分子机制。我们的工作假说得到了初步数据的支持，即Lc3c效应的特异性是由Lc3C端多肽介导的。

 DESCRIPTION (provided by applicant): Clear cell renal cell carcinoma (ccRCC) is a serious health concern for military personnel, particularly males beyond 40 years of age, including military veterans. According to The Defense Medical Epidemiology Database for 1995-2004 the incidence of RCC specifically for military members after the 4th decade of life is dramatically increased to 8.5 as compared to 1.5 cases per 100,000 person-years of the overall incidence. Our laboratory studies molecular pathways regulated by the von Hippel-Lindau (VHL) protein, the most frequently lost tumor suppressor in ccRCC. During the previous funding period we have published important data regarding the role of autophagy in growth of ccRCC. This competitive renewal builds on these substantial observations. Autophagy is a homeostatic function by which cells process their own organelles and proteins in order to eliminate defective molecules and to recycle nutrients. During tumor growth many cancers become addicted to autophagy as a source of nutrients. Moreover, autophagy is activated by different cancer therapies, causing resistance to treatments, and promoting use of autophagic inhibitors, chloroquine derivatives in combination therapies. MAP1LC3s (LC3) are essential proteins for the formation of an autophagosome. In our recently published work and preliminary results, we show that two LC3 paralogs, LC3B and LC3C, have opposite effects on growth of ccRCC. LC3B-dependent autophagy promoted growth of tumors formed by RCC cells with lost VHL, while LC3C-dependent autophagy was tumor suppressive and absent in VHL(-) cells. This proposal focuses on investigations to understand the activity of LC3C-dependent autophagy. Most importantly, we found that LC3C, but not LC3B, autophagic program targets of degradation enzymes of oxidative (rate limiting enzyme, glucose 6-phosphate dehydrogenase, G6PD) and non-oxidative (transketolase, TKT) pentose phosphate pathway (PPP). The effect of LC3C is specific for PPP and does not affect the glycolytic pathway. This important cancer pathway produces ribose-5-phophate for the production of nucleic acids and NADPH for the lipid synthesis and reduction of glutathione, all resulting in enhanced cell survival and growth. The importance of our data is further supported by unsupervised analysis published by KIRC TCGA, which showed significant correlation between levels of G6PD, TKT and poor outcome in ccRCC. The leading hypothesis for this proposal is that loss of VHL through indction of HIF reduces LC3C, permitting activation of PPP to support tumor growth. In Aim 1 we will determine the molecular mechanism by which VHL induces LC3C gene expression. Our working hypothesis is that HIF suppresses LC3C by inducing expression of repressing transcription factors. In Aim 2 we will determine the role of LC3C in the activities of the oxidative and non-oxidative branches of PPP in controlling nucleic acid synthesis and generation of NADPH using genetic and metabolomics approaches. In Aim 3 we will determine the role of the oxidative and non-oxidative branches of PPP in orthotopic xenograft tumor growth and expression of PPP enzymes in human kidney-ccRCC specimens. In Aim 4 we will determine the molecular mechanism by which LC3C, but not LC3B, specifically targets TKT and G6PD for autophagic degradation. Our working hypothesis, supported by preliminary data is that the specificity of LC3C effects is mediated by the LC3C C-terminal peptide.