Erlotinib treatment induces down-regulation of EGFR/EGFR-coupled signaling pathways and cell cycle arrest with subsequent induction of apoptosis in EGFR sensitive tumor cells.

<p>The erlotinib sensitive cell lines HCC827 and PC9 and the erlotinib-resistant cell line H1975 were treated with the indicated doses of erlotinib for 24 hours. Whole-cell lysates were subjected to immunoblotting with the indicated antibodies (A). PC9, HCC827 and H1975 cells were treated with erlotinib (0.5 µM) for 24h, 48h and 72h; nuclei were prepared, stained with propidium iodide and analyzed by flow cytometry. Results are shown for the G1 and S phases of the cell cycle (A). Apoptotic effects of erlotinib on EGFR-sensitive cell lines in comparison to the T790M mutant H1975 (B). Annexin V FACS was performed 12h, 24h, 36h, 48h, 72h and 96h after 0.5 µM erlotinib treatment. Images show Annexin V-positive cells after 48h in the different cell lines.