EphA7的激酶依赖/非依赖信号传导途径对前列腺癌的双重作用及机制

EphA7, a critical member of the tyrosine kinase receptor family, plays an important role in the physiological processes involving the formation of tissues and organs and the nervous system signal transduction. In recent years, it was suggested that EphA7 can promote tumor development in some cancers, whereas in other cancers EphA7 has been implicated as tumor supressor. Our previous studies reported the EphA7 expression was downregulated in prostate cancer due to its promoter hypermethylation, suggesting its essential role in the pathogenesis of prostate cancer. Our preliminary experiments showed the interaction between EphA7 and ephrinA5. In this study, we will confirm ephrinA5 as the ligand of EphA7. The expression of ephrinA5 and EphA7 will be detected and their clinical relevance with pathologic parameters will be analyzed. The auto-phosphorylation sites of EphA7 activated by ephrinA5 will also be detected utilizing site-directed mutagenesis techniques. The tumor proliferation, apoptosis, invasion, metastasis and cytoskeleton transforming effects of the kinase dependent or -independent signal transduction of EphA7 will be further analyzed. Finally, we'll detect and identify the signaling proteins, uncovering the EphA7-ephrinA5 signal transduction pathway. This study will reveal the kinase dependent/-independent signal transduction can induce dual function of EphA7 in the prostate cancer. Meanwhile, the downstream signaling pathway of EphA7-ephrinA5 will locate potential novel therapeutic targets for prostate cancer treatment.

EphA7属于受体酪氨酸激酶家族，参与组织和器官的形成、神经信号转导等过程。近年来发现EphA7在某些肿瘤以促癌的方式呈现，而在另外一些肿瘤中以抑癌的方式呈现，但机理不明。我们先前发现EphA7在前列腺癌由于启动子甲基化导致表达下调，预示其参与了前列腺癌的病理过程，预实验发现EphA7与ephrinA5有相互作用。本项目将观察EphA7、ephrinA5在前列腺癌中的表达及与病理参数的相关性，然后通过定点突变技术确定ephrinA5活化EphA7后的自磷酸化位点，分析EphA7的激酶依赖/非依赖效应对肿瘤细胞的增殖、凋亡、侵袭、转移和细胞骨架的影响，并鉴定EphA7-ephrinA5信号通路蛋白，阐明其信号传导途径。本项目将揭示EphA7所具有的激酶依赖/非依赖效应导致的对前列腺癌的双重作用，同时EphA7-ephrinA5下游信号通路的认识也将为前列腺癌治疗提供新的潜在治疗靶点。

EphA7 属于受体酪氨酸激酶家族，参与组织和器官的形成、神经信号转导等过程。我们先前报道了EphA7 在前列腺癌由于启动子甲基化导致表达下调，但EphA7 对前列腺癌细胞的作用及其调节机制尚不清楚。本研究检测EphA7、ephrinA5 在前列腺癌中的表达，并分析这两个指标与病理参数的相关性；通过定点突变技术、免疫共沉淀和免疫印迹技术明确ephrinA5与EphA7相互作用与ephrinA5诱导EphA7磷酸化及其磷酸化位点Y791；构建了各型EphA7慢病毒表达载体，体外感染前列腺癌细胞PC-3与DU145，并给予外源性ephrinA5刺激，观察EphA7磷酸化对细胞生长、凋亡、迁徙、侵袭的影响和体内EphA7对肿瘤细胞的抑制作用，并采用免疫印迹技术分析EphA7磷酸化激活的下游信号传导通路，发现野生型EphA7受体不仅可诱导Akt蛋白发生去磷酸化，而且分别下调和上调了抗凋亡蛋白BCl-2和促凋亡蛋白Bax的表达，诱导了前列腺癌细胞的凋亡，有望为前列腺癌治疗提供新的潜在治疗靶点。