Role of Gi/o-GPCR signaling in breast cancer progression

项目总结/摘要 G蛋白偶联受体（GPCR）是细胞表面受体的最大家族，其代表了细胞内的G蛋白。 对于包括癌症在内的多种疾病来说，这是非常理想的药物靶点。尽管其重要性，我们 对GPCR如何促进肿瘤发生和癌症进展的理解仍然有限，因为 有超过350种非感觉GPCR，其中许多在癌细胞中异常表达。这 一项提案旨在描述GPCR亚组Gi/o-GPCR在调节 干细胞样乳腺肿瘤起始细胞（TIC）的自我更新和致瘤活性。我们将测试 靶向Gi/o-GPCR可以消除TIC并恢复患者对当前疗法的反应。 作为我们研究的一个模型，我们专注于ErbB 2/HER 2阳性乳腺癌，因为它们是高度 侵袭性强，预后差。HER 2靶向治疗是这些癌症的首选治疗方法， 抗药性是主要障碍。耐药性的潜在机制在很大程度上仍然未知， 是由于肿瘤中TIC的储存。TIC可能逃避治疗，部分原因是他们找到了方法， 通过其他途径-包括GPCR介导的途径反式激活HER 2。 我们的初步研究发现Gi/o-GPCR在人HER 2扩增的乳腺癌中过表达 细胞系和来自HER 2驱动的乳腺肿瘤的小鼠TIC，并且是TIC体外生长所需的 和体内。使用我们的转基因小鼠品系，使我们能够上调或阻断Gi/o信号，在一个实验中， 诱导的方式，特别是在乳腺上皮细胞中，我们进一步表明HER 2驱动的自发性 乳腺肿瘤和肺转移的形成需要Gi/o-GPCR信号传导。这些令人兴奋的数据导致了 我们的建议的中心假设：HER 2驱动的乳腺肿瘤拥有一个TIC的水库人口， 上调Gi/o-GPCR信号传导;并且这过度激活EGFR/HER 2，允许TIC 自我更新和 最终促进肿瘤生长和转移。我们认为，破坏Gi/o-GPCR信号可能是 一种消融TIC、预防耐药性并维持HER 2靶向治疗有效性的方法 . 我们的建议使用多模式方法，包括 遗传和患者来源的异种移植小鼠 乳腺癌的模型有了这个强大的工具包，我们将确定上调Gi/o的机制， TIC中的信号传导以增加TIC致瘤性并驱动癌症发展（目的1）;阐明Gi/o- GPCR部分通过激活Gαi/o/c-Src和Gβγ-PI 3 K β反式激活EGFR/HER 2发挥功能 信号传导轴驱动癌症进展（目标2）;最后，测试阻断Gi/o-GPCR信号传导是否可以 消除TIC并增强对HER 2+乳腺癌当前治疗方案的敏感性（目标3）。 我们的研究的总体影响将是我们对机械理解的根本性进步， 致瘤性TIC获得通过Gi/o-GPCR信号转导反式激活EGFR/HER 2的能力。这些知识 可用于寻找消除TIC以增强HER 2治疗的新方法。

Project Summary / Abstract G-protein coupled receptors (GPCRs) are the largest family of cell surface receptors that represent the highly desirable drug targets for diverse diseases, including cancer. Despite their importance, our understanding of how GPCRs contribute to tumorigenesis and cancer progression remains limited, because there are over 350 non-sensory GPCRs and many of them are aberrantly expressed in cancer cells. This proposal aims to delineate the function and mechanisms of a subgroup of GPCRs, Gi/o-GPCRs, in regulating the self-renewal and tumorigenic activities of stem cell-like breast tumor-initiating cells (TICs). We will test the idea that targeting Gi/o-GPCRs can eliminate TICs and restore patient response to current therapeutics. As a model of our studies, we focus on ErbB2/HER2-positive breast cancers, because they are highly aggressive and have poor prognosis. HER2-targeted therapy is the preferred treatment for these cancers but drug resistance is the major hurdle. The mechanisms underlying drug resistance remain largely unknown but are attributed to a reservoir of TICs in tumors. TICs may escape therapy in part because they find ways to transactivate HER2 via other pathways—including pathways mediated by GPCRs. Our preliminary studies found Gi/o-GPCRs were overexpressed in human HER2-amplified breast cancer cell lines and mouse TICs from HER2-driven mammary tumors, and were required for growth of TICs in vitro and in vivo. Using our transgenic mouse lines that allow us to upregulate or block Gi/o signaling, in an inducible manner, specifically in mammary epithelial cells, we further showed HER2-driven spontaneous formation of mammary tumors and lung metastases requires Gi/o-GPCR signaling. These exciting data led to our proposal's central hypothesis: HER2-driven breast tumors harbor a reservoir population of TICs that upregulate Gi/o-GPCR signaling; and this hyperactivates EGFR/HER2, permitting TIC self-renewal and ultimately, promoting tumor growth and metastasis. We propose that disrupting Gi/o-GPCR signaling might be a way to ablate TICs, prevent resistance, and maintain effectiveness of HER2-targeted therapeutics . Our proposal uses multimodal approaches, including genetic and patient-derived xenograft mouse models of breast cancer. With this powerful toolkit we will determine the mechanisms of upregulated Gi/o signaling in TICs to increase TIC tumorigenicity and drive cancer development (Aim 1); elucidate if Gi/o- GPCRs function in part through transactivation of EGFR/HER2 via the activation of Gαi/o/c-Src and Gβγ-PI3Kβ signaling axes to drive cancer progression (Aim 2); and finally, test whether blocking Gi/o-GPCR signaling can eliminate TICs and enhance sensitivity to current treatment regimens for HER2+ breast cancer (Aim 3). The overall impact of our studies will be a fundamental advance in our mechanistic understanding of how tumorigenic TICs acquire the ability to transactivate EGFR/HER2 via Gi/o-GPCR signaling. This knowledge may be exploited for finding new ways to eliminate TICs to augment HER2 therapeutics.