Regulation of Rap1 Prenylation and Trafficking in Breast Cancer

 描述(申请人提供)：拟议的研究将探索一种新的方法，通过靶向控制小GTPase Rap1B的预烯基化的G蛋白偶联受体(GPCRs)来减少乳腺癌的转移。Prenylated Rap1B定位于乳腺癌细胞的质膜，稳定黏附连接，促进细胞与细胞的黏附，减少乳腺肿瘤转移细胞的释放。我们最近发现，通过激活乳腺癌细胞上的腺苷A2B受体(A2BR)来抑制Rap1B的前烯基化。我们报道，A2BR的激活导致蛋白激酶A磷酸化新合成的Rap1B，从而减少Rap1B与伴侣蛋白SmgGDS的相互作用，并阻止Rap1B进入前烯基化途径。这些事件促进了非前烯基化的Rap1B的胞浆和核积累，导致细胞与细胞之间的黏附丧失和获得转移表型。这种由GPCR介导的促进转移表型的途径是非常新颖的，因为以前人们认为细胞不具有抑制预烯基化的信号机制，并且认为抑制小GTP酶的预烯基化将抑制而不是促进转移。根据我们的发现，灭活A2BR应该会恢复Rap1B的预苯化和转运到细胞膜，这将增加细胞与细胞的黏附，减少转移细胞从肿瘤中的释放。我们最近发现，除A2BR外，其他GPCRs还可以抑制乳腺癌细胞中的Rap1B前烯基化。这些GPCR被目前用于癌症以外疾病患者的药物灭活。我们推测，这些药物可以用来灭活GPCRs，这些GPCRs抑制乳腺癌细胞中Rap1B的前烯基化，导致Rap1B前烯基化增加，细胞间黏附增加，转移减少。验证这一假说的方法包括：1)确定通过抑制Rap1B的预烯化和膜转运来促进培养的乳腺癌细胞转移表型的GPCRs，2)测试使这些GPCRs失活的药物，以确定它们是否会通过恢复肿瘤细胞中正常的Rap1B预烯化来减少动物模型中的乳腺癌转移，以及3)检查患者的乳腺肿瘤，以确定特定的GPCRs的表达和Rap1B预烯基化减弱是否与特定的肿瘤亚型和更具侵袭性的分期有关。实现这些目标将通过开发一种创新的策略来抑制乳腺癌转移而带来显著的好处。

 DESCRIPTION (provided by applicant): The proposed research will explore a new approach to diminish breast cancer metastasis by targeting G protein-coupled receptors (GPCRs) that control the prenylation of the small GTPase Rap1B. Prenylated Rap1B localizes at the plasma membrane of breast cancer cells and stabilizes adherens junctions, which promotes cell-cell adhesion and diminishes the release of metastatic cells from breast tumors. We recently discovered that Rap1B prenylation is suppressed by activating adenosine A2B receptors (A2BR) on breast cancer cells. We reported that A2BR activation causes protein kinase A to phosphorylate newly synthesized Rap1B, which decreases the interaction of Rap1B with the chaperone protein SmgGDS and prohibits Rap1B from entering the prenylation pathway. These events promote the cytosolic and nuclear accumulation of non-prenylated Rap1B, resulting in loss of cell-cell adhesion and acquisition of a metastatic phenotype. This GPCR-mediated pathway that promotes the metastatic phenotype is very novel, because it was previously thought that cells do not possess signaling mechanisms to suppress prenylation, and it was thought that suppressing the prenylation of small GTPases would inhibit, rather than promote, metastasis. Based on our discovery, inactivating A2BR should restore Rap1B prenylation and trafficking to the cell membrane, which will increase cell- cell adhesion and diminish the release of metastatic cells from the tumor. We recently discovered that other GPCRs (in addition to A2BR) can suppress Rap1B prenylation in breast cancer cells. These GPCRs are inactivated by drugs that are currently being given to patients with diseases other than cancer. We hypothesize that these drugs can be used to inactivate the GPCRs that suppress the prenylation of Rap1B in breast cancer cells, resulting in increased Rap1B prenylation, increased cell-cell adhesion, and diminished metastasis. This hypothesis will be tested by 1) identifying GPCRs that promote the metastatic phenotype of cultured breast cancer cells by suppressing the prenylation and membrane trafficking of Rap1B, 2) testing drugs that inactivate these GPCRs, to determine if they will diminish breast cancer metastasis in animal models by restoring normal Rap1B prenylation in the tumor cells, and 3) examining patients' breast tumors to determine if expression of specific GPCRs and diminished Rap1B prenylation are associated with specific tumor subtypes and a more aggressive stage. Accomplishing these goals will provide significant benefits by developing an innovative strategy to inhibit breast cancer metastasis.