Enhancement of CYP26A1 transcription by a specific homeobox factor. (A) Semiquantitative reverse transcriptase PCR following the treatment of 3 APL blast populations showing distinct sensitivities to ATRA and following the differentiation of NB4 cells. Electrophoresis results of retinoid-inducible targets (top) and homeobox transcription factors (bottom). (B) Specific enhancement of CYP26A1 transcription in Cos-7 cells following the expression of homeobox factors. Electrophoresis results of individual or cotransfection of 1 μg of both RARα and RXRβ plasmids along with 1 μg of the HOXA10v2 plasmid. (C) Fold induction observed with distinct doses of the HOXA10v2 or HOXA1 plasmids in Cos-7 cells. (D) Induction of CYP26A1 transcription in NB4 cells following the nucleofection of either HOXA10v2 or HOXA1 plasmid. The specificity of the enhancement of the cytochrome was confirmed by measuring the modulation of other retinoid-induced targets (cumulative means for HIC1, PRAM1, and CEBPB). *P < .05 compared with ATRA alone. (E) Specific down-regulation of CYP26A1 was observed after siRNA transfection that induced HOXA10v2 transcript silencing. *P < .05 compared with ATRA control. (C-E) Error bars represent the standard error (n = 2).