PDF file - 191K, Western blotting for phosphorylated (Y1068) EGFR, total EGFR, pERK and total ERK in NSCLC cells treated with DMSO, gefitinib and/or Wnt pathway inhibitors, qPCR analyses of Axin-2 mRNA levels in cells in cells treated with canonical Wnt pathway inhibitors, western blotting for activated beta-catenin in stable cell lines, and determination of the ability of activated beta-catenin expression to mitigate the impact of gefitinib and/or XAV939 treatment in HCC4006 NSCLC cells
ARTICLE ABSTRACTLung cancer is the leading cause of death worldwide. Adenocarcinomas, the most common histologic subtype of non-small cell lung cancer (NSCLC), are frequently associated with activating mutations in the epidermal growth factor receptor (EGFR) gene. Although these patients often respond clinically to the EGFR tyrosine kinase inhibitors erlotinib and gefitinib, relapse inevitably occurs, suggesting the development of escape mechanisms that promote cell survival. Using a loss-of-function, whole genome short hairpin RNA (shRNA) screen, we identified that the canonical Wnt pathway contributes to the maintenance of NSCLC cells during EGFR inhibition, particularly the poly-ADP-ribosylating enzymes tankyrase 1 and 2 that positively regulate canonical Wnt signaling. Inhibition of tankyrase and various other components of the Wnt pathway with shRNAs or small molecules significantly increased the efficacy of EGFR inhibitors both in vitro and in vivo. Our findings therefore reveal a critical role for tankyrase and the canonical Wnt pathway in maintaining lung cancer cells during EGFR inhibition. Targeting the Wnt-tankyrase-β-catenin pathway together with EGFR inhibition may improve clinical outcome in patients with NSCLC. Cancer Res; 72(16); 4154–64. ©2012 AACR.