RNPC1 Enhances Progesterone Receptor Functions By Regulating Its MRNA Stability In Breast Cancer

Objective:To explore the mechanism of progesterone receptor (PR) expression regulated by RNPC1. Further look into the mechanism of PR function change with this regulation.Materials and methods:In breast cancer tissue, IHC was used to detect the expression of RNPC1 and PR, and immunofluorescence was used to confirmed the localization of RNPC1 and PR. RNPC1 was overexpressed and knocked down in MCF-7, BT474, MDA-MB-231 and SUM 1315 cells. qRT-PCR and western blot were applied to detected the PR and its target genes expression. Considering ER could regulate PR, ER was knocked in MCF-7 and BT474 cells. Then RNPC 1 was overexpressed or knocked down, and PR protein and mRNA level was detected. Overexpressed and knocked down of RNPC 1 MCF-7 and BT474 cells was dealt with actinomycin D, and the mRNA level was detected at different time. RNA immunoprecipitation (RIP) was used to confirm the combination of RNPC land PR mRNA. RNA electrophoretic mobility shift assay (REMSA) was used to verify the region of PR mRNA combined with RNPC1 protein. CCK8 and colony assay were applied to explore the PR function regulated by RNPC1. To further explore the influence of RNPC1la on PR proliferating functions in vivo, tumor formation following inoculation of MCF-7 cells in mouse models was applied.Results:In breast cancer tissue, RNPC1 was corresponded with PR (P<0.05). RNPC1a was mainly expressed in the cytoplasm and PR was mainly expressed in the nucleus. In breast cancer cells MCF-7 and BT474, overexpression of RNPC1 upregulated PR, while knockdown of RNPC1 could decrease PR expression. The target genes of PR, Wnt4 and β-catenin was also regulated by RNPC1. In ER knocked down cells, RNPC1 could still regulated PR expression, which was a independent process. Overexpression increase the mRNA stability of PR, while knockdown of RNPC1 decrease the mRNA stability of PR. RNPC1 protein could bind to PR 3’UTR AU-rich elements, and enhance the mRNA stability. Besides, RNPC1 enhances progesterone receptor functions by regulating in vitro and in vivo.Conclusions:In breast cancer, the expression of RNPC1 and PR was related. Overexpression of RNPC1 could increase while knockdown of RNPC1 could decrease the PR expression. RNPC1 could combined with PR mRNA 3’UTR and enhanced mRNA stability. RNPC1 enhances progesterone receptor functions by regulating in vitro and in vivo.