Transcription activity of EB1285 in MCF-7 cells. (a) The chemical structure of the vitamin D analogue EB1285 before and after (EB1089) 1α-hydroxylation. (b) VDR-directed transcription activity of EB1089 or EB1285 in transfected MCF-7 cells. (c) Activation of transcription in the presence of the cytochrome P450 inhibitor ketoconazole. Asterisks represent p < 0.001.