<p>Table S1: IC50 values for inhibition of proliferation of (A) 5 PDAC cell lines and (B) 2 derived erlotinib-resistant (ER) cell lines, in response to inhibitors of EGFR (erlotinib, gefitinib), IGF1R (NVP-AEW541), MEK (PD-98059), PI3K (LY-294002), PI3K� (NVP-BYL719) and PI3K/mTOR (NVP-BEZ235). Average  SEM of 6 experiments. Highly insensitive cell lines are shaded in grey in (A). Paired t-test statistics was calculated for resistance in (B).</p>
ARTICLE ABSTRACT
Purpose: PI3K–Akt is overexpressed in 50% to 70% of pancreatic ductal adenocarcinoma (PDAC). The hypothesis of this study is that PI3K and EGFR coinhibition may be effective in PDAC with upregulated PI3K–Akt signaling.Experimental Design: Multiple inhibitors were tested on five PDAC cell lines. EGFR inhibitor (EGFRi)–resistant cell lines were found to have significantly overexpressed AKT2 gene, total Akt, and pAkt. In vitro erlotinib-resistant (ER) cell models (BxPC-ER and PANC-ER) with highly constitutively active PI3K–Akt were developed. These and their respective parent cell lines were tested for sensitivity to erlotinib, IGFIR inhibitor NVP-AEW541 (AEW), and PI3K-alpha inhibitor NVP-BYL719 (BYL), alone or in combination, by RTK-phosphoarray, Western blotting, immunofluorescence, qRT-PCR, cell proliferation, cell cycle, clonogenic, apoptosis, and migration assays. Erlotinib plus BYL was tested in vivo.Results: Erlotinib acted synergistically with BYL in BxPC-ER (synergy index, SI = 1.71) and PANC-ER (SI = 1.44). Treatment of ER cell lines showing upregulated PI3K–Akt with erlotinib plus BYL caused significant G1 cell-cycle arrest (71%, P < 0.001; 58%, P = 0.003), inhibition of colony formation (69% and 72%, both P < 0.001), and necrosis and apoptosis (75% and 53%, both P < 0.001), more so compared with parent cell lines. In primary patient-derived tumor subrenal capsule (n = 90) and subcutaneous (n = 22) xenografts, erlotinib plus BYL significantly reduced tumor volume (P = 0.005). Strong pEGFR and pAkt immunostaining (2+/3+) was correlated with high and low responses, respectively, to both erlotinib and erlotinib plus BYL.Conclusion: PDAC with increased expression of the PI3K–Akt pathway was susceptible to PI3K–EGFR coinhibition, suggesting oncogenic dependence. Erlotinib plus BYL should be considered for a clinical study in PDAC; further evaluation of pEGFR and pAkt expression as potential positive and negative predictive biomarkers is warranted. Clin Cancer Res; 20(15); 4047–58. ©2014 AACR.
