Abstract 2569: miR520a inhibits Fzd9 in bronchial epithelial cells and NSCLC

Non-small cell lung cancer (NSCLC) continues to be the most diagnosed cancer type worldwide and has the highest mortality rate. Treatment is highly researched, but 5 year survival remains around 20%. Chemoprevention could combat the development of lung cancer in individuals who are at high risk, such as former cigarette smokers. Iloprost is a prostacyclin analogue demonstrated to reduce the presence of endobronchial dysplasia in former smokers. Increased Frizzled-9 (Fzd9) expression is induced by Iloprost, resulting in activation of peroxisome proliferator activated receptor γ (PPARγ) and inhibition of transformed growth. The goal of this study is to elucidate the relationship of cigarette smoke, NSCLC, and miRNA regulation of Fzd9 expression. We hypothesized that miRNA regulate Fzd9 expression when NSCLC cells are exposed to both cigarette smoke condensate (CSC) and Iloprost. miR520a5p was predicted in silico to bind Fzd9 and we validated binding with a miR520a5p mimic and Fzd9 39UTR luciferase in an immortalized human bronchial epithelial cell line (HBEC) and NSCLC cell lines. A549 and H322 NSCLC cells and HBEC were exposed to cigarette smoke condensate (CSC) and Iloprost. CSC increased miR520a expression, while the opposite was observed in Iloprost treated cells. We also measured Fzd9 39UTR activity and demonstrated that CSC decreases both Fzd9 39UTR and PPRE activity, while Iloprost does the opposite. We investigated the effect of miR520a5p on targets downstream of Fzd9, including PPARγ response element (PPRE), a direct measure of PPARγ activity, and epithelial to mesenchymal transition (EMT) gene expression, including Cox2, E-cadherin, and CRB3. We found that when Fzd9 is inhibited by miR520a5p, PPRE activity and epithelial gene expression are inhibited, while mesenchymal gene expression is stimulated. Rescue experiments combining CSC with a miR520a5p inhibitor or iloprost with a miR520a5p mimic supported a role for miR-520a-5p in inhibition of Fzd9 in a CSC carcinogenic pathway in lung epithelial cells that is reversed with iloprost treatment. Overall, these findings suggest a mechanism for miRNA regulation of Fzd9 in lung epithelial cells exposed to cigarette smoke and a potential chemoprevention target. Citation Format: Alex J. Smith, Paulina Do, Kayla M. Sompel, Alamelu Elango. miR520a inhibits Fzd9 in bronchial epithelial cells and NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2569.