肿瘤微环境中CAF外泌体介导的microRNA下调PTPN12的表达促进乳腺癌发生发展的分子机制

Protein tyrosine phosphatase nonreceptor type 12 (PTPN12) as an antioncogene is frequently inactivated or down-regulated in triple-negative breast cancer (TNBC). PTPN12 restrains several receptor tyrosine kinases (RTKs) suggesting that PTPN12 deficiency leads to aberrant activation of multiple RTKs and poor prognosis. At present, the anticarcinogenic effect of PTPN12 is widely studied. Nevertheless, the key factor decreasing PTPN12 expression level in TNBC remains to be further explored. In tumor microenvironment, cancer associated fibroblast (CAF) is the most common constituent. Emerging evidences suggest that exosomes secreted by CAFs play vital roles in promoting tumor initiation, progression and metastasis. Exosomes carry biologically active molecules, such as microRNAs, mRNAs, lncRNAs and proteins, which can be transferred and function in recipient cells. It is reported that microRNAs can suppress target protein expression by binding with specific mRNA through either degradation or translational inhibition. Therefore, we hypothesized that CAF derived exosomes delivering microRNA could promote breast cancer initiation and progression by reducing PTPN12 expression. In the current project, we will thoroughly investigate the effects of CAF derived exosomes on breast cancer and the underlying molecular mechanism through cellular and molecular approaches. Our research will contribute to a deeper understanding of breast cancer initiation and progression. Furthermore, our research will provide a new strategy for the development of novel chemotherapeutic drugs.

蛋白酪氨酸磷酸酶PTPN12是抑癌基因。PTPN12低表达或者发生失活突变会降低其抑制原癌通路的功能，促进乳腺癌的发生和发展。目前，对于PTPN12抑癌作用的研究主要集中在其对下游信号因子的调控，但是导致乳腺癌中PTPN12表达降低的分子机制鲜有报道，亟待更深层次的探究。肿瘤微环境中，肿瘤相关成纤维细胞CAF通过外泌体运载多种生物活性分子促进恶性肿瘤的发生和发展。microRNA作为外泌体的重要组分，直接调控基因组中三分之一以上基因的表达。为此，我们提出假说：CAF外泌体递送相关microRNA到乳腺癌细胞，下调乳腺癌细胞中PTPN12的表达，从而促进恶性肿瘤的侵袭和转移。本项目将分离提取CAF外泌体，通过外泌体microRNA表达差异分析，联合细胞和分子生物学技术，探究乳腺癌中PTPN12表达降低的分子机制，为更深层次地揭示乳腺癌的发展过程奠定基础，为开发新型乳腺癌化疗药物提供思路。

抑癌基因PTPN12是经典蛋白酪氨酸磷酸酶家族的成员之一，由于PTPN12低表达或者产生失活突变会导致其丧失抑制原癌基因的能力，从而导致乳腺癌的发生和发展。本项目主要探究导致乳腺癌细胞中PTPN12降低的主要原因。在肿瘤微环境中，肿瘤相关成纤维细胞能够分泌外泌体，而外泌体中可以运载多种生物活性分子，从而调控肿瘤细胞的基因表达和细胞功能。microRNA是外泌体中的主要生物活性成分之一，可直接调控基因的表达。本项目通过分离获取乳腺癌的肿瘤相关成纤维细胞以及正常成纤维细胞，并进行成纤维细胞的鉴定；经培养之后获取其外泌体，通过对外泌体的microRNA进行表达差异分析，结合数据库，筛选出miR-216是调控乳腺癌细胞中PTPN12表达的重要microRNA；在乳腺癌细胞中过表达miR-216，能够检测到PTPN12表达明显下调，而其下游原癌基因HER2磷酸化水平明显升高。综上所述，本项目揭示了乳腺肿瘤相关成纤维细胞对乳腺癌细胞中重要基因PTPN12的表达调控机制，为阐明乳腺微环境对肿瘤的发生和发展机制提供了理论基础。