Over-expression of c-Myc and the cross-talk between DNA-PKcs and c-Myc in metastatic cancer cells. (A) The levels of c-Myc and DNA-PKcs proteins in PC3 and PC3-MM2 cells (left) and KM12 and KM12L4A cells (right) were determined using Western blot analysis. (B) Immunoprecipitates (IP) of the DNA-PKcs or c-Myc antibody from PC3 and PC3-MM2 cells were subjected to Western blot analysis with c-Myc, phospho-c-Myc (pMyc) or DNA-PKcs antibody to determine the interaction between DNA-PKcs and c-Myc. IgG was used as an internal control for the immunoprecipitation. (C) PC3 cells were transfected with siRNA against DNA-PKcs or scrambled siRNA as a control. After 48 h, the cell lysates of the transfectants were subjected to Western blot analysis with c-Myc or pMyc antibody.