Table 1.
VDR Binding Properties,a HL-60 Differentiating Activities,b and Transcriptional Activitiesc of the Vitamin D Analogs (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16)
| Compound | Structure of a side chain (R) | Compd No. | VDR binding | HL-60 differentiation | 24-OHase transcription | |||
|---|---|---|---|---|---|---|---|---|
| Ki | ratio | EC50 | ratio | EC50 | ratio | |||
| 1α,25-(OH)2D3 | - | 1 | 1 × 10-10 M | 1 | 2 × 10-9 M | 1 | 2 × 10-10M | 1 |
 |
 |
4 | 1 × 10-10 M | 1 | 8 × 10-11 M | 0.04 | 7 × 10-12M | 0.035 |
 |
5 | 1 × 10-10 M | 1 | 2 × 10-9 M | 1 | 4 × 10-10M | 2 | |
 |
6 | 6 × 10-11 M | 0.6 | 6 × 10-10 M | 0.3 | 6 × 10-11 M | 0.3 | |
 |
7 | 1 × 10-10 M | 1 | 1 × 10-9 M | 0.5 | 2 × 10-10 M | 1 | |
 |
8 | 9 × 10-11 M | 0.9 | 9 × 10-11 M | 0.045 | 1 × 10-11 M | 0.05 | |
 |
|
9 | 2 × 10-10 M | 2 | 5 × 10-9 M | 2.5 | 6 × 10-10 M | 3 |
|
10 | 1 × 10-10 M | 1 | 4 × 10-10 M | 0.2 | 8 × 10-11 M | 0.4 | |
|
13 | 3 × 10-10 M | 3 | 2 × 10-9 M | 1 | 4 × 10-10 M | 2 | |
|
14 | 8 × 10-11 M | 0.8 | 1 × 10-10 M | 0.05 | 2 × 10-11 M | 0.1 | |
 |
|
11 | 5 × 10-9 M | 50 | 1 × 10-7 M | 50 | 3 × 10-8 M | 150 |
|
12 | 5 × 10-10 M | 5 | 2 × 10-8 M | 10 | 7 × 10-9 M | 35 | |
|
15 | 2 × 10-9 M | 20 | 6 × 10-8 M | 30 | 2 × 10-8 M | 100 | |
|
16 | 4 × 10-10 M | 4 | 6 × 10-9 M | 3 | 1 × 10-9 M | 5 | |
Competitive binding of 1α,25-(OH)2D3 (1) and the synthesized vitamin D analogs to the full-length recombinant rat vitamin D receptor. The Ki values are derived from dose-response curves and represent the inhibition constant when radiolabeled 1α,25-(OH)2D3 is present at 1 nM and a Kd of 0.2 nM is used. The binding ratio is the average ratio of the analog Ki to the Ki for 1α,25-(OH)2D3.
induction of differentiation of HL-60 promyelocytes to monocytes by 1α,25-(OH)2D3 and the synthesized vitamin D analogs. Differentiation state was determined by measuring the percentage of cells reducing nitro blue tetrazolium (NBT). The EC50 values are derived from dose-response curves and represent the analog concentration capable of inducing 50% maturation. The differentiation activity ratio is the average ratio of the analog EC50 to the EC50 for 1α,25-(OH)2D3.
Transcriptional assay in rat osteosarcoma cells stably transfected with a 24-hydroxylase gene reporter plasmid. The EC50 values are derived from dose-response curves and represent the analog concentration capable of increasing the luciferase activity by 50%. The luciferase activity ratio is the average ratio of the EC50 for the analog to the EC50 for 1α,25-(OH)2D3. All the experiments were carried out in duplicate on at least two different occasions.