Role of RNA Binding Protein with Multiple Splicing (RBPMS) Variants in Cell Proliferation, Invasion and Angiogenesis in Ovarian Cancer.

Worldwide, the number of cancer‐related deaths continues to increase due to the ability of cancer cells to become chemotherapy‐resistant and metastasize. For women with ovarian cancer, a staggering 70% will become resistant to the front‐line therapy, cisplatin. RNA binding protein with multiple splicing (RBPMS) is a member of family proteins that bind to the nascent RNA transcripts regulate their processing, which includes splicing, transport, localization and stability. Evidence indicates that RBPMS interact with c‐Fos, a member of the AP‐1 family that dimerizes with c‐Jun to stimulate AP‐1 transcriptional activity. Furthermore, RBPMS interacted with transcription factor Smad3, which bind to c‐Jun increasing AP‐1 transcriptional activity. Three major RBPMS isoforms have been described, RBPMS‐A (21.8 kDa), RBPMS‐B (22.4 kDa) and RBPMS‐C (24.2 kDa). Reports have shown that each RBPMS isoform interacts with proteins and/or RNAs responsible for cell growth, proliferation, and tumor progression. Previous reports of our laboratory have found that RBPMS expression decrease in cisplatin resistance compared with cisplatin sensitive cells. However, the specific RBPMS isoform responsible of this observation has not been elucidated and less is known about its role on invasiveness ability and angiogenesis capacity. We overexpressed each RBPMS variants (A, B and C) in the cisplatin resistant ovarian cancer cells, A2780CP20, and performed cell viability, cell proliferation and invasion assays. Significant reduction in the number of colonies and their area were observed in both isoform A and isoform C clones, compared with isoform B and control empty vector clones. However, clones of isoform A were more sensitive to cisplatin treatment in comparation with isoform B and C clones. In vivo experiments showed a significant reduction in tumor growth between RBPMS A and C when compared with the controls. Tumor tissues were subjected to immunohistochemical analysis for proliferation (Ki67) and angiogenesis (CD31). Elevated signals of both antibodies were detected in tissues from control groups when compared with RBPMS A and C overexpressing tumor tissues. These studies along with the RNAseq suggest that RBPMS, regulate transcripts involved in cell proliferation and invasion capacity of ovarian cancer cells. Moreover, RBPMS A and C represses uncontrolled proliferation, invasiveness, and angiogenesis in ovarian cancer cells. However, only the isoform A contributed to the cisplatin sensitivity of ovarian cancer cells. Future efforts on this project will be focused on determining the RBPMS isoform that represses AP‐1 (c‐Fos and c‐Jun) dependent gene regulation in cisplatin sensitive ovarian cancer cells.