PSM-E在前列腺癌中诱导肿瘤相关巨噬细胞凋亡的功能及机制研究

PSMA is a known specific biomarker of prostate cancer. PSM-E is a new alternatively spliced variant we found previously, and it was found to have the ability of suppressing the invasion and migration of prostate cancer cells. Tumor-associated macrophages (TAMs) that derived from monocyte in the circulatory systemis similar to M2 macrophages and can inhibit anti-tumor immune response, and therefore participate in the development and progression of angiogenesis, tumorigenesis, invasion and metastasis. Thus, strategies targeting TAMs anti-tumor therapy are the major theme of the research in current cancer treatment. In our previous study, we observed that PSM-E could strongly induce TAM apoptosis in primary culture TAM model from transplated prostate cancer in mice, which indicate that PSM-E may efficiently trigger apoptosis of TAMs, and then promote anti-tumor immunity response. Therefore, this study will explore the function and underlying mechanisms of PSM-E on TAMs by using this primary culture model and in vivo model. Meanwhile, for the first time, this study will demonstrate that PSM-E can form complex with ASK1, an apoptosis associated kinase, and activate it, revealing the molecular mechnisms and pathway for PSM-E-induced cell apoptosis by means of Western blotting, MACS Technology, flow cytometry, etc. In conclusion, these results will reveal the new anti-tumor function and mechanisms of PSM-E by inducing TAM apoptosis, and provide a theoretical basis for PSM-E as a novel target for targeted prostate cancer therapy.

前列腺特异膜抗原（PSMA）是前列腺癌较特异的生物学标志物，PSM-E是本课题组首次发现的PSMA新型剪接变异体，已发现其可抑制前列腺癌侵袭转移。肿瘤相关巨噬细胞（TAM）可抑制机体的抗肿瘤免疫应答，其异常聚集是肿瘤重要的恶性表型，而靶向TAM的免疫疗法已成为肿瘤治疗的新策略。前期研究表明，在小鼠前列腺癌移植瘤原代培养TAM模型中，PSM-E能较强的诱导TAM的细胞凋亡。本项目拟利用TAM体外及体内模型，进一步探讨PSM-E蛋白诱导TAM凋亡的新功能；进而采用Western blotting、磁珠分选、流式细胞术等方法，从PSM-E调节TAM细胞内ASK1/JNK信号转导而诱导凋亡方面对其抗肿瘤免疫机理进行深入探讨；并系统性开展其体内外抗肿瘤免疫活性研究。本项目将揭示PSM-E通过诱导TAM凋亡而促进机体抗肿瘤免疫的新功能，提示PSM-E可能成为TAM靶向性抗肿瘤免疫分子治疗的一个新靶点。

前列腺特异膜抗原（PSMA）作为前列腺癌较特异的生物学标志物已受到广泛关注。PSM-E是本课题组首次发现的PSMA新型剪接变异体，其结构与组织表达与PSMA相比均有明显差异。肿瘤相关巨噬细胞（TAMs）可抑制机体的抗肿瘤免疫应答，其异常聚集是肿瘤重要的恶性表型，可用于不良生存预后的判断标志，因此靶向TAMs的免疫疗法已成为肿瘤治疗新策略研究的热点。本研究从临床问题出发，发现在前列腺癌组织中PSM-E与M2型TAMs表面特异性蛋白CD206的表达呈负相关性，提示PSM-E高表达可显著减少TAMs的浸润。在细胞模型上，应用PSM-E高表达或低表达细胞与单核细胞系THP-1共培养系统，证明了PSM-E可较强抑制单核细胞分化成巨噬细胞。并且创新性发现了PSM-E可以外泌体形式存在，可在细胞间传递，并以外泌体形式发挥作用。进而，阐明了其抑制单核细胞分化成巨噬细胞的分子机制：首次发现PSM-E蛋白可以与细胞膜上一种激酶RACK1相互结合，从而阻断了RACK1下游MAPK/ERK及Akt通路信号转导，从而抑制了单核细胞分化的核心调控通路。并且，PSM-E可较强抑制肿瘤微环境中MAPK/ERK及Akt通路下游的炎性细胞因子的分泌（包括IL4、IL-13等），从而可显著的抑制单核细胞分化的核心诱发因子。从外因到内因两方面抑制肿瘤微环境中单核细胞分化成巨噬细胞，最终抑制了TAMs的产生。综上所述，本研究揭示了PSM-E通过结合RACK1并阻断其信号转导，同时抑制肿瘤微环境中炎性细胞因子产生而促进机体抗肿瘤免疫的新功能及新机制，提示PSM-E及其外泌体形式可能可成为TAMs靶向性抗肿瘤免疫分子治疗的一个新靶点。