Targeted induction of endogenous NKX3‐1 by small activating RNA inhibits prostate tumor growth

BACKGROUND: RNA activation (RNAa) is a small RNA-mediated gene regulation mechanism by which expression of a particular gene can be induced by targeting its promoter using small double-stranded RNA also known as small activating RNA (saRNA). We used saRNA as a molecular tool to examine NKX3-1's role as a tumor suppressor and tested in vitro and in vivo antitumor effects of NKX3-1 induction by saRNA. MATERIALS AND METHODS: NKX3-1 saRNA was transfected into human prostate cancer cells including LNCaP, CWR22R, PC-3, CWR22RV1, DuPro, LAPC4, and DU145. The transfected cells were used for analysis of gene expression by RT-PCR and immunoblotting, proliferation, apoptosis and cell cycle distribution. PC-3 xenograft models were established in immunocompromised mice and treated with NKX3-1 saRNA. RESULTS: NKX3-1 saRNA induced NKX3-1 expression in different prostate cancer cell lines, resulting in inhibited cell proliferation and survival, cell cycle arrest and apoptotic cell death. These effects were partly mediated by NKX3-1's regulation of several downstream genes including the upregulation of p21 and p27, and the inhibition of VEGFC expression. Treatment of mouse xenograft prostate tumors with intratumoral delivery of NKX3-1 saRNA formulated in lipid nanoparticles significantly inhibited tumor growth and prolonged animal survival. CONCLUSIONS: By revealing several important target genes of NKX3-1, our findings corroborated NKX3-1's role as a tumor suppressor gene through direct regulation of the cell cycle and growth/survival pathways. This study also validated the therapeutic potential of saRNA for the treatment of prostate cancer via targeted activation of tumor suppressor genes.