Abstract 3049: miR-10a regulates PI3K signaling and paclitaxel response in NSCLC.

Phosphatidylinositol 3-kinases (PI3Ks) are enzymes involved in diverse cellular functions including cell growth, proliferation, differentiation, motility, survival and apoptosis. Many of these functions relate to class I PI3Ks, heterodimers composed of regulatory and catalytic subunits that convert extracellular cues to intracellular responses upon activation. Overall, this signaling pathway is under extremely tight regulation and even slight perturbations can lead to aberrant pathway activation, which is the case in a majority of cancers. We are interested in whether PI3K signaling is regulated by one or more microRNAs and whether those miRNAs affect cancer cell viability and drug response in PI3K-driven oncogenesis. We identified miR-10a as a regulator of PIK3CA, the gene encoding the catalytic subunit of PI3K. In NSCLC cell lines, we found that manipulation of intracellular levels of miR-10a results in significant changes in both mRNA and protein levels of PIK3CA; PIK3CA was confirmed as a direct target by luciferase reporter assay. Using functional assays, we found that increasing miR-10a levels leads to a reduction in PI3K enzymatic activity and modulation of cellular metabolism. Additionally, increasing miR-10a levels inhibits colony formation, while decreasing miR-10a levels increases it. We then investigated if inhibition of the PI3K pathway using miR-10a mimic affects the response of NSCLC cell lines to paclitaxel, which is a front-line therapy for advanced NSCLC. We observed a 10-fold decrease in cell viability in the presence of miR-10a mimic relative to paclitaxel alone, while inhibiting miR-10a resulted in a 10-fold increase, suggesting that high levels of miR-10a may be prognostic for response to taxanes. To assess prognostic value, we assessed expression in NSCLC tumors and found that high miR-10a levels correlate with longer overall patient survival. MicroRNAs can target hundreds of genes, meaning that miR-10a may regulate PIK3CA expression both directly and indirectly. We identified the transcription factor GATA6 as both a target of miR-10a with a predicted miR-10a target site in its 3’UTR and a regulator of PI3K expression, with several conserved binding sites in the promoter of PIK3CA. siRNA knockdown of GATA6 reduced both PI3K mRNA and protein levels. Manipulating miR-10a levels showed that miR-10a negatively regulates both mRNA and protein levels of GATA6; direct interaction was confirmed by luciferase reporter assay. These findings demonstrate that miR-10a regulates the PI3K pathway at two distinct levels. The identification of a miR-10a as a modulator of cellular response to paclitaxel through its inhibition of PI3K, both directly and indirectly through GATA6, defines a novel regulatory pathway modulating paclitaxel sensitivity in lung cancer. This may provide novel adjuvant strategies for taxane regimens in the treatment of lung cancer as well as biomarkers for predicting taxane response in NSCLC. Citation Format: Christopher DeSevo, Liqin Du, Carmen Behrens, Ignacio Wistuba, John Minna, Alexander Pertsemlidis. miR-10a regulates PI3K signaling and paclitaxel response in NSCLC. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3049. doi:10.1158/1538-7445.AM2013-3049