Regulation of Rap1 Prenylation and Trafficking in Breast Cancer

 描述（由申请人提供）：拟议的研究将探索一种新的方法，以减少乳腺癌转移的目标G蛋白偶联受体（GPCR），控制异戊二烯化的小GTCRap 1B。异戊烯化Rap 1B定位于乳腺癌细胞的质膜并稳定粘附连接，从而促进细胞间粘附并减少乳腺肿瘤转移细胞的释放。我们最近发现，Rap 1B异戊二烯化是通过激活乳腺癌细胞上的腺苷A2 B受体（A2 BR）来抑制的。我们报道了A2 BR激活导致蛋白激酶A磷酸化新合成的Rap 1B，从而减少Rap 1B与伴侣蛋白SmgGDS的相互作用，并阻止Rap 1B进入异戊烯化途径。这些事件促进非异戊二烯化Rap 1B的胞质和核积累，导致细胞-细胞粘附的丧失和转移表型的获得。这种促进转移表型的GPCR介导的途径是非常新颖的，因为以前认为细胞不具有抑制异戊烯化的信号传导机制，并且认为抑制小GTP酶的异戊烯化将抑制而不是促进转移。基于我们的发现，灭活A2 BR应该恢复Rap 1B异戊二烯化和向细胞膜的运输，这将增加细胞-细胞粘附并减少转移细胞从肿瘤中的释放。我们最近发现，其他GPCR（除了A2 BR）可以抑制乳腺癌细胞中的Rap 1B异戊二烯化。这些GPCR被目前用于癌症以外疾病患者的药物灭活。我们假设这些药物可用于抑制乳腺癌细胞中Rap 1B异戊烯化的GPCR，导致Rap 1B异戊烯化增加，细胞间粘附增加，转移减少。该假设将通过1）鉴定通过抑制Rap 1B的异戊烯化和膜运输促进培养的乳腺癌细胞的转移表型的GPCR，2）测试抑制这些GPCR的药物，以确定它们是否将通过恢复肿瘤细胞中正常的Rap 1B异戊烯化来减少动物模型中的乳腺癌转移，和3）检查患者的乳腺肿瘤以确定特异性GPCR的表达和Rap 1B异戊烯化的减少是否与特异性肿瘤亚型和更具侵袭性的阶段相关。实现这些目标将通过开发抑制乳腺癌转移的创新策略提供显著的益处。

 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.