Figure 6.

Inhibition of colony formation of melanoma SKMEL-188 treated with pregna-5,7-diene-3β,17α,20-triols 4R (B) and 4S (E) and their D-like and L-like derivatives: 4R-D (C), 4R-L (D), 4S-D (F) and 4S-L (G).

An active form of vitamin D₃ 1,25(OH)₂D₃ was used as positive control (A). The inhibition of melanoma SKMEL-188 colony formation was used to assay biological activity of newly synthesized compounds at 0.1, 10 and 100 nM concentrations. The average value (n=6) for ethanol treated cells was used as a 0 nM on all graphs. The total number of colonies and their diameters with cutoff below and above 20 nm was measured and expressed in colony forming units (CFU). Data are presented as mean±SEM for colony-forming assay (n=4 to 6); *P<0.05, **P<0.005, and ***P<0.001. Representative pictures of SKMEL treated with studied compounds and the vehicle control are shown (H).