Abstract 1100: Targeting ITGA3/ITGB1 signaling by tumor-suppressive microRNA-223 inhibits cancer cell migration and invasion in prostate cancer

Abstract

Abstract BACKGROUNDS: Most patients initially respond to androgen-deprivation therapy, but eventually acquire resistance and progress to castration-resistant prostate cancer (CRPC). Several clinical trials for CRPC have shown limited benefits, eventually resulting in disease progression and metastasis. Our recent study of microRNA (miRNA) expression signature in CRPC revealed that miR-223 expression was significantly reduced in PCa tissues, suggesting miR-223 functions as a tumor suppressive miRNA in PCa cells. The aim of this study was to investigate the functional significance of miR-223 and to identify its regulated oncogenic genes in PCa. METHODS: Expression levels of miR-223 were evaluated in PCa clinical specimens and PCa cell lines (PC3 and PC3M) by quantitative real-time PCR methods. Gain-of-function studies (cell proliferation, migration and invasion assays) were performed using transfection of mature miR-223 into cancer cells. Genome-wide gene expression analysis and in silico analysis were applied to investigate molecular targets regulated by miR-223 in PCa cells. A luciferase reporter assay was carried out to determine whether 3’ UTR of target genes have actual biding sites for miR-223. To investigate the functional role of target genes in PCa cells, loss-of-function studies by silencing of these genes were performed. RESULTS: The expression levels of miR-223 were significantly reduced in PCa clinical specimens and cell lines compared to non-cancerous prostate tissues. Restoration of miR-223 significantly inhibits cancer cell migration and invasion in PCa cells. Integrin alpha-3 (ITGA3) and integrin beta-1 (ITGB1) were identified as direct target genes of miR-223 by microarray, in silico studies, and luciferase reporter assays. ITGA3 and ITGB1 interact with multiple extracellular matrix proteins and mediate several survival signaling into the cancer cells. Knockdown of ITGA3 and ITGB1 significantly inhibited cancer cell migration and invasion in PCa cells by regulating downstream signaling. CONCLUSIONS: Downregulation of miR-223 was a frequent event of PCa cells and it functions as a tumor suppressor via targeting ITGA3 and ITGB1. Overexpression of ITGA3 or ITGB1 might be contributed to PCa oncogenesis and metastasis. Elucidation of tumor-suppressive miR-223 regulated molecular pathways and targets could provide new information on potential therapeutic strategies in PCa. Citation Format: Ichiro Fukumoto, Akira Kurozumi, Yusuke Goto, Ryosuke Matsushita, Mayuko Kato, Rika Nishikawa, Shinichi Sakamoto, Tomohiko Ichikawa, Naohiko Seki. Targeting ITGA3/ITGB1 signaling by tumor-suppressive microRNA-223 inhibits cancer cell migration and invasion in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1100.