A microRNA signature of response to erlotinib is impacted by the EMT‐ inducing cytokine TGFβ1

Abstract

PurposeWe endeavored to understand the contribution of canonical TGFβ signaling on expression of a 13‐gene microRNA (miR) signature of erlotinib response.BackgroundWe identified a 13‐gene miRNA signature predictive of response to the epidermal growth factor receptor (EGFR) inhibitor, erlotinib, in Non‐Small Cell Lung Cancer (NSCLC) cell lines. Bioinformatic analysis of the signature showed a functional convergence on TGFβ canonical signaling. We hypothesize that TGFβ signaling controls expression of the miR genes comprising an erlotinib response signature in NSCLC.MethodsTwo signature miR genes (miR‐140‐3p and miR‐141) were chosen for study. Promoters regions of both genes harbor putative Smad Binding Elements (SBEs), DNA binding domains for TGFβ‐responsive Smad transcription factors. TGFβ signaling impact on miR‐140 and ‐141 expression was assessed in erlotinib‐resistant (A549) and –sensitive (PC9) NSCLC cells by quantitative real‐time PCR (qRT‐PCR), luciferase reporter assays, and chromatin immunoprecipitation (ChIP).Results(1) qRT‐PCR showed endogenous miR 140/141 expression decreased after short term TGFβ1 treatment in both cell lines. After 7 days of treatment, the trend continued. (2) The promoter region of miR‐141, containing 6 SBEs, was cloned into a luciferase reporter vector. The miR‐141 luciferase construct is responsive to TGFβ stimulation like that seen in qRT‐PCR. (3) ChIP experiments will assess specific Smad complexes binding SBE sites.ConclusionWe expected that canonical TGFβ signaling molecules, Smads, bind to and control miR genes with SBEs in A549 cells. In PC9 cells, some miR genes likely control Smad protein expression while a non‐canonical TGFβ response may regulate signature miR expressionCollege funds were used.