Table II.

Summary of the relative IC₅₀ values for inhibition of proliferation of human melanoma A375 cells by H₂O₂ (0.004-0.250 mM), cisplatin (0.19-300 µM) or dacarbazine (0.15-10 µM) in the presence or absence of the tested secosteroids.

Incubation time, h	Tested compound	Relative IC 50
		Monotreatment	+10 nM 1α,25(OH)2D3	+10 nM 20(OH)D3	+10 nM 21(OH)pD	+10 nM calcipotriol
24	H2O2	0.017±0.07	0.011±0.001	0.013±0.0006	0.017±0.002	0.012±0.0006
24	Cisplatin	4.81±2.2	11.61±0.98a	14.08±3.29b	9.37±1.64	15.23±6.15b
48	Cisplatin	2.57±0.19	1.97±0.22	3.47±1.04	3.71±1.90	2.13±1.01
48	Dacarbazine	1.07±0.31	0.45±0.35a	1.17±0.40	1.04±0.36	0.85±0.39

Data are presented as the mean ± standard deviation of three independent experiments (n=6 each). The data were subjected to analysis of variance followed by Tukey’s multiple comparison test.

^aP<0.05 and

^bP<0.001 vs. monotreatment. IC₅₀, half maximal inhibitory concentration; H₂O₂, hydrogen peroxide; 1α,25(OH)₂D3, 1α,25-dihydroxyvitamin D3; 20(OH)D3, 20S-hydroxyvitamin D3; 21(OH)pD, 21-hydroxypregnacalciferol.