KRAS-induced lung cancer is a very common disease, for which there are currently no effective therapies. Direct targeting of KRAS has failed in clinical trials and intense efforts are underway to identify KRAS targets that play a crucial role in oncogenesis. One promising KRAS-regulated pathway that has so far been overlooked is the microRNA pathway. Even though many microRNAs that regulate expression of KRAS are known, microRNAs regulated by oncogenic KRAS remain largely unknown. Our goal was to identify microRNAs regulated by oncogenic KRAS in lung cells that could contribute to the oncogenic phenotype. Due to a reported positive correlation between microRNA486-5p (miR-486-5p) expression and the presence of KRAS mutations in colon cancer specimens, we decided to investigate in lung cells whether KRAS regulates miR-486-5p. For that purpose we used an immortalized human primary lung epithelial cell line (SALEB) and its isogenic KRAS-transformed counterpart (SAKRAS), as well as lung cancer cell lines with either gain-of-function or loss-of-function of KRAS. We found, in all models tested, a positive correlation between expression of oncogenic KRAS and expression of miR-486-5p. We also found a negative correlation between expression of oncogenic KRAS and expression of miR-486-5p targets, including FoxO1, a tumor suppressor. In order to evaluate how miR-486-5p affects Ras-induced oncogenic properties, we transfected miR-486-5p inhibitor oligonucleotides into KRAS-positive lung cancer cell lines H358 and A549. Inhibition of miR-486-5p expression leads to reduced growth in clonogenic assays and reduced MTT viability. This reduction is not associated with increased cell death, but, as measured by 3H-Thymidine incorporation, it is associated with decreased cell proliferation. Interestingly, transfection of miR-486-5p double-stranded RNA mimic oligonucleotides into KRAS negative lung cancer cell line H1703 or into H358 cells with loss of function of KRAS by RNA interference leads to enhanced proliferation and clonogenicity. Taken together, these results indicate, not only that miR-486-5p is a KRAS target in lung cancer, but also that miR-486-5p acts as an oncomiR contributing to KRAS-induced cell proliferation. Further understanding of miR-486-5p targets could uncover novel pathways for KRAS-induced lung cancer therapy design.
Citation Format: Mateus N. Aoki, Amanda C. P. Salviatto, Tatiana C. C. Lobo, Ana Cláudia O. Carreira, Mari C. Sogayar, Daniela S. Basseres. MicroRNA486-5p is a KRas target involved in promoting cell proliferation in lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 533. doi:10.1158/1538-7445.AM2014-533