Mitochondrial Metabolism and ROS Regulate Lung Cancer

描述（由申请人提供）：肺癌是美国男性和女性癌症相关死亡的最常见原因。80%的肺癌是非小细胞肺癌（nsclc）， 30%的非小细胞肺癌是腺癌，其中包括非吸烟者中不断增加的癌症病例。Kras癌基因的突变已在20-30%的非小细胞肺癌中被发现。Kras癌基因通过一系列激酶发出信号，促进细胞增殖。kras驱动肿瘤的治疗靶向需要识别致癌kras驱动的增殖所需的信号通路。kras驱动的肺癌细胞比非癌性肺细胞表现出更高水平的活性氧（ROS）。ROS被认为是激活多种信号通路的信号分子，包括PI3K、ERK1/2 MAPK和转录因子缺氧诱导因子（hypoxia inducible factors, hfs），这些信号通路促进肿瘤细胞增殖、血管生成和转移。在细胞质中参与信号传导的ROS的主要形式是过氧化氢（H2O2），它是由细胞质中铜锌超氧化物歧化酶（SOD1）将超氧化物（O2-）转化而来。我们报道了来自线粒体复合体III的O2-及其在细胞质中向H2O2的转化是启动kras诱导的肿瘤细胞增殖和hif缺氧激活所必需的。目前，尚不清楚胞质中复合体iii产生的O2或h2o2依赖性信号是否需要在体内致癌kras驱动的肺致瘤性。最近的研究表明，谷氨酰胺是TCA循环产生NADH和FADH2的主要燃料。这些还原等价物将电子提供给电子传递链，从而生成超氧化物络合物III。我们最近报道了kras驱动的肿瘤细胞也利用谷氨酰胺来促进TCA循环。谷氨酰胺可通过谷氨酰胺酶（GLS）转化为谷氨酸，谷氨酸通过转氨酶（GPT2或GOT2）或谷氨酸脱氢酶（GDH）转化为α -酮戊二酸进入TCA循环。初步数据表明，使用转氨酶抑制剂或GPT2的RNAi来阻止谷氨酰胺进入TCA循环，可以减少致癌kras驱动的肿瘤细胞的非锚定生长。然而，目前尚不清楚抑制GPT2是否会在体内减轻肺腺癌，或者成年小鼠的正常组织是否需要GPT2。该资助的主要目标是从遗传学上确定TCA循环减少复合物III产生的超氧化物、胞质过氧化氢的产生和谷氨酰胺的利用是否会减弱Kras驱动的肺癌小鼠模型和使用携带Kras突变的人类A549肺腺癌细胞的原位小鼠模型中的肿瘤发生。

DESCRIPTION (provided by applicant): Lung cancer is the most common cause of cancer-related death in both men and women in the United States. Eighty percent of lung cancers are non-small cell lung cancers (NSCLCs) and 30% of NSCLCs are adenocarcinomas, which include a rising population of cancer cases that occur in nonsmokers. Mutations in the Kras oncogene, which signals through a cascade of kinases to promote cellular proliferation, have been identified in 20-30% of NSCLCs. Therapeutic targeting of Kras-driven tumors necessitates the identification of signaling pathways required for oncogenic Kras-driven proliferation. Kras-driven lung cancer cells display higher levels of reactive oxygen species (ROS) than noncancerous lung cells. ROS have been proposed to serve as signaling molecules to activate numerous signaling pathways, including PI3K, ERK1/2 MAPK, and the transcription factors hypoxia inducible factors (HIFs), which promote tumor cell proliferation, angiogenesis, and metastasis. The major form of ROS that participates in signaling in the cytosol is hydrogen peroxide (H2O2), which is generated by its conversion from superoxide (O2-) by copper-zinc superoxide dismutase (SOD1) in the cytosol. We have reported that O2- from mitochondrial complex III and its conversion to H2O2 in the cytosol are required to initiate Kras-induced cellular proliferation and hypoxic activation of HIFs in tumor cells. Presently, it is not known whether complex III-generated O2- or H2O2-dependent signaling in the cytosol is required for oncogenic Kras-driven lung tumorigenicity in vivo. Recent studies indicate that glutamine is a major fuel for the TCA cycle to generate NADH and FADH2. These reducing equivalents donate electrons to the electron transport chain resulting in complex III generated superoxide. We recently reported that Kras-driven tumor cells also utilize glutamine to fuel the TCA cycle. Glutamine can be converted by glutaminase (GLS) to glutamate, which enters the TCA cycle through conversion into alpha-ketoglutarate by aminotransferases (GPT2 or GOT2) or glutamate dehydrogenase (GDH). Preliminary data indicate that preventing glutamine entry into the TCA cycle using inhibitors of aminotransferases or RNAi of GPT2 reduces anchorage-independent growth of oncogenic Kras-driven tumor cells. However, it is not known if inhibition of GPT2 would attenuate lung adenocarcinoma in vivo or if GPT2 is dispensable for normal tissues in the adult mouse. The major goal of this grant is to genetically determine whether diminishing complex III generated superoxide, production of cytosolic hydrogen peroxide, and glutamine utilization by the TCA cycle will attenuate tumorigenesis in the oncogenic Kras-driven mouse model of lung adenocarcinoma and in an orthotopic mouse model using human A549 lung adenocarcinoma cells harboring a Kras mutation. PUBLIC HEALTH RELEVANCE: Lung cancer is the most common cause of cancer-related death in both men and women in the United States. The major goal is to determine whether preventing mitochondrial metabolism or production of hydrogen peroxide would be effective in diminishing lung cancer. Positive results would provide a rationale for therapies targeting metabolic enzymes that regulate mitochondrial metabolism.