PO-254 Merkel cell polyomavirus T-antigen regulate microRNAs post-transcriptionally through DICER in merkel cell carcinoma

Abstract

all animal works has been obtained from the Institutional Animal Care and Use Committee, Academia Sinica. Results and discussions Galectin-4 was upregulated during the development of castration resistance and metastasis. High expression of galectin-4 in PCa cells exhibited castration resistance, tumor-regenerating stem-like cells, expressed SOX9 and ALDH1A1, and ability to colonise distant metastases. We identify a feed-forward signalling pathway by which galectin-4 signalling through RTK-Myc axis upregulated gene transcription of enzymes in a specific O-glycosylation pathway and the biosynthesis of their substrates, thus altered the cellular modification of O-glycosylation, and bolstered castration resistance and metastasis. These coordinated effects conferred more and more binding sites for galectin-4 and amplified the RTKs signalling, implicating crosstalk mechanisms to activate androgen receptor signalling and drive the PCa progression. Conclusion MYC regulates oncofetal O-glycosylation in RTKs thus primes the cells for binding to galectin-4 and downstream signalling, which promotes PCa castration resistance, metastasis, and clinically poor survival. PO-253ABSTRACT WITHDRAWN Introduction Background and aim Merkel cell carcinoma (MCC) is an aggressive type of skin cancer. About 80% of MCCs harbour integrated Merkel cell polyomavirus (MCV) genome with a mutation in the large T (LT) gene. MCV T-antigens are required for neoplastic transformation and maintenance of cell growth. however the molecular mechanism by which the virus induces tumorigenesis remains unclear. In this study we aimed to identify and characterise functional role of MCV-regulated microRNAs in MCC. Material and methods We did silencing or ectopic expression of MCV T-antigens to identify specific miRNAs regulated by MCV T-antigens by RT-qPCR. The involvement of MCV Tantigens and miRNAs in autophagy was evaluated using LC3-II conversion, mRFP-EGFP-LC3 reporter and/or transmission electron microscopy. The targets of miRNAs were verified by western blot analysis and luciferase reporter assays. We also look for the DICER expression by western blot. Results and discussions We identified specific miRNAs regulated by MCV T-antigens. Using both gain-and loss-of-function experiments, we showed that MCV T-antigens and MCVregulated miRNAs (miR-375, miR-30a-5p and miR-30a-3p) could regulate autophagy. We further demonstrated that miR-375 could directly regulate ATG7 and SQSTM1, while both miR-30a-3p and miR-30a-5p could target BECN1. We also identified the MCV T-antigens regulates these miRNAs PO-254 MERKEL CELL POLYOMAVIRUS T-ANTIGEN REGULATE MICRORNAS POST-TRANSCRIPTIONALLY THROUGH DICER IN MERKEL CELL CARCINOMA