Elucidating the mechanism of Ga13 mediated tumor suppression in pancreatic cancer

研究综述 异三聚体G蛋白从G蛋白偶联受体(GPCRs)传递信号，G蛋白偶联受体是最大的一类 调节多种生物过程的细胞表面蛋白。Gα13，G12家族成员 在异三聚体G蛋白中，已被报道在不同的肿瘤环境中是肿瘤抑制或启动子。 我们最近报道，Gα13的缺失加速了肿瘤的发展，并降低了井- 描述了胰腺癌的遗传性小鼠模型。从机制上讲，Gα13缺陷小鼠胰腺 肿瘤的mTOR信号升高，类似于人类胰腺癌。一直以来，肿瘤起源于 Gα13缺陷的胰腺癌细胞对雷帕霉素敏感，雷帕霉素是一种特性良好的mTOR抑制剂。 最近，我们发现在胰腺肿瘤和癌细胞中Gα13的缺失增加了线粒体 炎性细胞因子的代谢和表达。然而，肿瘤新陈代谢的影响和 炎症在G-α13缺陷肿瘤发生发展中的作用及其信号转导机制 对这些过程的监管还没有得到调查。我们在本申请中的目标是阐明 胰腺癌细胞Gα13缺失促进肿瘤发生和发展的机制(S) 在体内的进展。中心假说是Gα13的缺失通过升高促进肿瘤的发展 MTOR信号驱动线粒体新陈代谢和炎症。提出了两个具体目标：1) 确定mTORC_1信号对促进G-α13缺陷胰腺细胞代谢是否必要 肿瘤。2)确定mTORC 1信号是否在调节Gα13炎症增加中起重要作用- 缺陷性肿瘤在目标1中，我们将确定抑制mTORC1信号是否会延缓肿瘤的发展 并在缺乏Gα13的早期和晚期肿瘤中诱导细胞死亡。此外，我们将评估Gα13丢失 调节肿瘤代谢以及Gα13缺陷肿瘤是否易受线粒体扰动的影响 功能。在目标2中，我们将确定Gα13缺失是否会增加炎性细胞因子水平和肿瘤- 促进早期和晚期肿瘤的免疫细胞。我们将确定是否阻止mTORC1信号 限制候选细胞因子的表达和免疫细胞的渗透以抑制Gα13缺失的肿瘤生长 肿瘤。最后，我们将检查抗炎药与线粒体抑制剂的结合是否 功能将协同增强抗肿瘤疗效。该提案的创新之处在于使用了 一种独特的小鼠模型来研究Gα13的抑瘤功能，其中该基因在两种情况下都缺失 人和小鼠胰腺肿瘤与mTOR信号升高和较差的生存结果相关。我们 还将使用人类肿瘤切片培养的创新方法来确定Gα13的状态 决定了对抑制mTORC1信号的反应。这项提议意义重大，因为它将澄清 Gα13在胰腺癌中的抑瘤机制，为胰腺癌的有益治疗提供见解 Gα13缺乏症患者。

RESEARCH SUMMARY The heterotrimeric G proteins transduce signals from the G protein-coupled receptors (GPCRs), the largest class of cell surface proteins that regulate a wide variety of biological processes. Gα13, a member of the G12 family of heterotrimeric G proteins, has been reported to be a tumor suppressor or promoter in different tumor contexts. We recently reported that loss of Gα13 accelerated tumor development and reduced survival in a well- characterized genetic mouse model of pancreatic cancer. Mechanistically, Gα13-deficient mouse pancreatic tumors had elevated mTOR signaling, similar to human pancreatic cancer. Consistently, tumors derived from Gα13-deficient pancreatic cancer cells were susceptible to rapamycin, a well-characterized mTOR inhibitor. Recently, we have shown that loss of Gα13 in pancreatic tumors and cancer cells increased mitochondrial metabolism and expression of inflammatory cytokines. However, the impact of tumor metabolism and inflammation on the development and progression of Gα13-deficient tumors and whether mTOR signaling regulates these processes has not been investigated. Our objective in this application is to elucidate the mechanism(s) by which the deletion of Gα13 in the pancreas cancer cells contributes to tumor development and progression in vivo. The central hypothesis is that loss of Gα13 promotes tumor development through elevated mTOR signaling to drive mitochondrial metabolism and inflammation. Two specific aims are proposed: 1) Determine whether mTORC1 signaling is necessary for promoting cellular metabolism of Gα13-deficient pancreas tumors. 2) Determine whether mTORC1 signaling is essential in mediating the increased inflammation in Gα13- deficient tumors. In Aim 1, we will determine whether inhibition of mTORC1 signaling delays tumor development and induces cell death in early and advanced tumors lacking Gα13. Further, we will assess how Gα13 loss regulates tumor metabolism and whether Gα13-deficient tumors are susceptible to perturbations of mitochondrial functions. In Aim 2, we will determine whether Gα13 loss increases inflammatory cytokine levels and tumor- promoting immune cells in early and advanced tumors. We will determine whether blocking mTORC1 signaling limits the expression of candidate cytokines and immune cell infiltration to suppress tumor growth in Gα13 lacking tumors. Finally, we will examine whether combining anti-inflammatory agents with inhibitors of mitochondrial function will synergistically enhance anti-tumor efficacy. The innovative component of this proposal is the use of a unique mouse model to study the tumor suppressive function of Gα13, where the loss of the gene in both human and mouse pancreas tumors correlates with elevated mTOR signaling and worse survival outcome. We will also use the innovative approach of human tumor slice culture assays to determine whether Gα13 status dictates the response to inhibition of mTORC1 signaling. The proposal is significant because it will elucidate the tumor suppressive mechanisms of Gα13 in pancreatic cancer, providing insights into beneficial therapies for patients with Gα13 deficiency.