CYP11A1 and leukemia: In addition, 20(OH)D3, a novel product of vitamin D3 metabolism by CYP11A1 (Slominski et al, 2005), has strong antiproliferative activity in keratinocytes (Zbytek et al, 2008) and anticancer activity in leukaemia lines (Slominski et al, 2010).