e20043 Background: Targeted therapies caused a revolution in treatment of non-small cell lung cancer (NSCLC). Response to Epidermal Growth Factor Receptor such as erlotinib, can be predicted by the presence of sensitizing mutations in EGFR. In case of cMET, amplification or exon 14 skipping serve as biomarkers for response to cMET-TKIs, crizotinib. Methods: In this study, we investigated the combination of erlotinib and crizotinib on several squamous NSCLC cell lines wild-type for EGFR and cMET. Growth inhibition was determined using the sulforhodamine B-assay. Combination indexes (CI) were calculated based on the method of Chou and Talalay. A CI below 0.8 was considered synergistic, between 0.8 and 1.2 was considered additive and above 1.2 was considered antagonistic. The influence of treatment on the cell cycle, cell migration, 3D cell cultures and phosphorylation was studied. Results: The H1703 cell line gave an antagonistic (CI = 1.20±0.15), the Calu1 (CI = 0.81±0.04), H520 (CI = 0.87±0.06) and SKMES1 (CI = 0.81±0.02) were additive and LUDLU (CI = 0.39±0.07) was synergistic. A G1 phase arrest occurred after treatment with erlotinib (38 to 76%), whereas crizotinib caused a G2/M phase arrest (13 to 64%). In the combination, the effect of crizotinib was dominant (13 to 52%). A decrease in p-ERK1/2 (Thr202/204), p-PRAS40 (Thr246) and p-GSK3 β (Ser9) was observed. Phospho-PRAS40 showed a decrease after treatment with erlotinib or crizotinib, whereas combination treatment almost abolished p-PRAS40. In the SKMES1 cell line, p-PRAS40 only decreased after the combination, whereas H1703 cells showed no change in p-PRAS40 levels. Phospho-PRAS40 activity is strongly linked to PI3K/Akt signaling. Her3 is able to heterodimerize both with EGFR and cMET, thus activating downstream PI3K/Akt signaling. No expression of Her3 in the antagonistic cell line was detected. In the LUDLU, levels of p-Her3 were not detectable after erlotinib treatment and in the combination, whereas in the SKMES1 levels of p-Her3 slightly decreased only after combination treatment. Conclusions: To conclude, the simultaneous inhibition of both EGFR and cMET leads to a strong inhibition of PI3K/Akt signaling, leading to synergy in the LUDLU wild-type squamous NSCLC cells.
Iodine-131 induces apoptosis in HTori-3 human thyrocyte cell line and G2/M phase arrest in a p53-independent pathway
