Expression of Id1 is specifically down-regulated by tyrosine kinase inhibitors. (A) Real-time quantitative RT-PCR analysis of transduced 32Dcl3 cells treated with either imatinib or MLN518 using Id1-specific primer. Results were normalized against the expression level of GAPDH. 32D/BCR-ABL cells treated with MLN518 or 32D/FLT3-ITD cells treated with imatinib were used as a negative control. (B) Western blot analysis of transduced 32Dcl3 cells treated with either imatinib or MLN518 using Id1 antibody. 32D/BCR-ABL cells treated with MLN518 or 32D/FLT3-ITD cells treated with imatinib were used as a negative control. The membrane was stripped and reblotted with a RACK1 antibody as a loading control. (C) Western blot analysis of murine BaF3 cells transduced with either BCR-ABL or FLT3-ITD using c-Abl or FLT3 antibody. Untransduced BaF3 cells were used as a negative control. (D) Western blot analysis of transduced BaF3 cells treated with either imatinib or MLN518 using Id1 antibody. BaF3/BCR-ABL cells treated with MLN518 or BaF3/FLT3-ITD treated with imatinib were used as a negative control. The membrane was stripped and reblotted with RACK1 antibody as loading control. (E) Western blot analysis of K562 cells and Molm-14 cells using c-Abl or FLT3 antibody. (F) Western blot analysis of K562 cells treated with imatinib or Molm-14 cells treated with MLN518 using Id1 antibody. K562 cells treated with MLN518 or Molm-14 cells treated with imatinib were used as a negative control. The membrane was stripped and reblotted with RACK1 antibody as loading control.