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Abstract 2441: Evaluation of combination of an EGFR and AKT inhibitor inEGFRmutant andEGFRwild type non-small cell lung cancer cells lines.

Background: Epidermal growth factor receptor (EGFR) inhibition with tyrosine kinase inhibitors (TKIs) has proven successful in the management of patients with non small cell lung cancer (NSCLC). However, clinical benefit is predominantly limited to the subgroup of patients with an activating EGFR mutation (10%). Treating the remaining 90% of patients with wild type (wt) EGFR is an unmet clinical need. Aim: To evaluate the effect of an allosteric AKT inhibitor (AKTi 1/2) in combination with the EGFR inhibitor gefitinib on cell proliferation, apoptosis and signalling output in EGFR mutant/wt NSCLC cell lines. Methods: Four NSCLC cell lines were selected: NCI-H522 and NCI-H1651 (EGFR wt and K-RAS wt), PC9 and HCC827 (EGFR mutant). The 96hr sulphorhodamine assays was used to assess the effect of gefitinib and AKTi 1/2 on growth inhibition, and median effect analysis to calculate combination indices (CIs) to assess the effect of both drugs in combination. The expression of p-EGFR, p-AKT, p-S6, p-ERK and cleaved PARP were studied by Western blotting in the EGFR wt NCI-H522 and the EGFR mutant PC9 cell lines. Results: EGFR wt cell lines NCI-H522 and NCI-H1651 were relatively resistant to gefitinib (IC50 values of 7.0 ± 2.5 uM and 8.8 ± 0.9 uM, respectively) compared with the EGFR mutant cell lines PC9 and HCC827 (IC50 values of 0.07 ± 0.03 uM and 0.004 ± 0.0005 uM, respectively). The combination of gefitinib and AKTi 1/2 produced synergistic inhibition of growth in both EGFR wild type and mutant cell lines. Synergism was more marked in EGFR wt cell lines with CI values (ED50) of 0.53 ± 0.28 and 0.49 ± 0.17 for NCI-H522 and NCI-H1651 respectively, compared with 0.74 ± 0.11 and 0.76 ± 0.14 for the EGFR mutant cell lines PC9 and HCC827, respectively. Concomitant exposure of cells to gefitinib and AKTi 1/2 for 24 hrs caused incremental inhibition of p-AKT, p-S6 and p-ERK in both the EGFR wt (NCI-H522) and EGFR mutant (PC9) cell lines. Gefitinib alone resulted in partial inhibition of AKT phosphorylation in PC9 cells and up-regulation in NCI-H522 cells. Incremental induction of cleaved PARP, a marker of apoptosis, was seen in PC9 cells treated with the combination of gefitinib and AKTi 1/2. Conclusions: These results demonstrate synergistic growth inhibition of EGFR wt and mutant NSCLC cell lines by the combination of gefitinib with AKTi 1/2. Additional pre-clinical studies are investigating this further. Clinical studies of the combination doublet are warranted to expand the utility of EGFR TKI in EGFR wt NSCLC. Citation Format: Martina Puglisi, Parames Thavasu, Adam Stewart, Jaishree Bhosle, Sanjay Popat, Mary E R O9Brien, Udai Banerji. Evaluation of combination of an EGFR and AKT inhibitor in EGFR mutant and EGFR wild type non-small cell lung cancer cells lines. [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 2441. doi:10.1158/1538-7445.AM2013-2441