MiR-221 to modulate tumor growth in vivo and as a regulator of TGF.

Abstract

e23008 Background: Despite the advances in cancer therapy, when Prostate Cancer (PCa) progress to castration resistant phase, patients develop incurable bone metastases. Understanding the processes that regulate homing and survival of metastatic cancer cells in the bone is crucial for the identification of new therapies. TGF-β signaling plays a major role in bone remodeling and according to the “vicious cycle hypothesis” is a master regulator of maintenance of prostate cancer cells in lytic bone lesions. microRNAs (miRs) are a class of small non-coding RNAs that regulates many biological process. miR-221 expression has been previously associated with prostate cancer progression. Here we studied the effect of miR-221 on TGF-β signaling and the impact of miR-221 on tumor growth in vivo Methods: miR-221 was overexpressed in PC3 and RWPE-1 cells and PMEPA was monitored by RT-qPCR and western blot. Expression of miR-221 in PC3 and RWPE-1 cells was assessed by RT-qPCR. Luciferase assay was used to investigate the interaction between miR-221 and PMEPA1. For zebrafish experiment, fluorescently labelled PC-3M-Pro4 cells overexpressing miR-221 were injected in the Duct of Cuvier (DC) of zebrafish embryos. Results: miR-221 overexpression resulted in decreased PMEPA1 mRNA and protein in PC-3 cells. Luciferase reporter assay indicated that miR-221 can directly interact with PMEPA1 3’ UTR. We show an enhancement of the proliferative effect of TGF-β in PC-3 cells, following miR-221 overexpression. In conclusion, we observed increased Smad2 activation upon TGF-β treatment in miR-221 overexpressing PC-3 cells. Inoculation of PC-3M-Pro4 cells overexpressing miR-221 in the DC of zebrafish embryos resulted reduced tumor burden compared to control. Finally, we observed inverse correlation between miR-221 and PMEPA1 expression in normal vs. tumor tissue collected from PCa patients. Conclusions: Our results indicate that miR-221 is a regulator of TGF-β signaling via modulation of PMEPA1 and miR-221 overexpression can reduce tumor growth in vivo.