PO-175 The secretary miR-141 facilitates ovarian cancer metastasis through reprogramming stromal fibroblast cells in pre-metastatic niches formation

Introduction Regardless of the modern advances in cancer therapeutics, cancer metastasis is still a major obstacle in the clinical management of ovarian cancer. Emerging evidence discloses exosomal miRNAs act as critical roles in cancer development. One of the possibility is the secretary miRNAs mediating communications between tumour cells and their tumour microenvironment. However, the functions and mechanisms of miRNAs in regulating cancer metastasis are not fully understood. We have previously identified that Hsa-miR-141 (miR-141) is not only aberrantly expressed in aggressive ovarian cancer but also enhances anoikis resistance in metastatic progression of ovarian cancer through targeting KLF12/SP1/Survivin axis. Here, we report that miR-141 is also a tumour secretary miRNA which can remodel the stromal cells to facilitate the formation of pre-metastatic niches for ovarian cancer metastasis. Material and methods QPCR analysis was used to evaluate the level of exosomal miR-141 in the conditioned medium of ovarian cancer cells. T-HESCs and WPMY-1 were used for miR-141 mediated reprogramming stromal cells. Cytokine array, ELISA, QPCR and Western blot analyses were used for measuring the levels of EMMPRIN and GRO-α. LC-MS/MS and proteomic analyses to identify miR-141-mediated target, Yes Associated Protein 1(YAP1). Results and discussions miR-141 was frequently overexpressed in ovarian cancer cells and also secreted to the surroundings through exosomal pathway. Functional analyses revealed miR-141 enables to reprogram the stromal cells because miR-141-expressing stromal cells showed an escalating secretion of cytokines GRO-α and EMMPRIN in cultured media. By co-culture with ovarian cancer cells with above conditioned media, or the recombinant proteins of GRO-α and EMMPRIN, ovarian cancer cells exhibited increased cell proliferation. Proteomic profiling of miR-141 reprogrammed stromal cells revealed YAP1, a key downstream effector of the Hippo pathway was suppressed. Depletion of YAP1 in stromal cells also increased the expression of GRO-α and EMMPRIN in the conditioned media. On the contrary, restoration of YAP1 attenuated the escalated secretion of GRO-α and EMMPRIN, indicating the reduction of YAP1 might be required for increased YAP/TAZ –mediated transcriptional activities of GRO-α and EMMPRIN. Conclusion Our preliminary findings suggest the exosomal miR-141 could reprogram stromal cells through altering Hippo/YAP1 signalling in production of GRO-α and EMMPRIN, to facilitate metastatic colonisation of ovarian cancer.