Effects of EGFR and IGF1R inhibitors in suppression of epithelial cancer cell through synergistic induction of DSB-related apoptosis.

<p><b>A</b>, Radio-sensitivity assay of cells treated with EGFR and IGF1R inhibitors. Cancer cells of different groups were treated without (control) or with AG1024 (10 µM), Erlotinib (10 µM) or both for 1 h and then subjected to radio-sensitivity clonogenic assay. After 10 days, the clones were fixed and stained. Surviving fraction was calculated according to the colony counts and plating efficiency. <b>B</b>, Radio-sensitivity assay of cells treated with EGFR and IGF1R siRNAs. Cells of different groups were transfected with non-silencing control siRNA (NSC-siRNA), EGFR and/or IGF1R siRNA, and then subjected to radio-sensitivity clonogenic assay as described in panel A. <b>C</b>, Apoptosis of cells treated with EGFR and IGF1R inhibitors. Prostate cancer cell lines were pre-treated with AG1024 or Erlotinib at indicated concentrations for 1 h, and then irradiated for 2 Gy. After 4 hours, they were stained with Annexin V and propidium iodide for flow cytometry to determine percentage of apoptotic cells. <b>D</b>, Apoptosis of prostate cancer cell lines transfected with EGFR and/or IGF1R siRNA. Cells of different groups were transiently transfected with NSC siRNA, IGF1R siRNA or EGFR siRNA for 24 h, and then irradiated for 2 Gy. Apoptosis was analyzed as in panel C. The data were presented as mean ± SD from three independent experiments. *P<0.05, **P<0.01, as compared to the control cells.