The impact of ADI combined with GEM on PANC-1 cell apoptosis, cell cycle arrest, and inhibition of colony formation. A, Apoptosis in PANC-1 cells at the 24 hour time point in the control group, ADI alone, GEM alone, or both ADI and GEM groups was visualized by in situ fluorescence microscopy using the indicated dyes (Annexin V-FITC/PI or Hoechst 33258/PI). B, The percentages of apoptotic PANC-1 cells treated with vehicle, ADI alone, GEM alone, or both drugs were estimated by FACS analysis following staining with Annexin V-FITC/PI. C, Cell cycle progression of PANC-1 cells following treatment with ADI or GEM alone or in combination was analyzed by single staining with PI. *, P < 0.05, as compared with the control group or indicated groups. D, Proliferative activity of PANC-1 cells treated by GEM following ADI was viewed by the single cell colony formation assay.