CYP27B1 and neuroblastoma: In agreement with increased Aβ peptide level in the case of mild 25(OH) vitamin D3 deficiency, calcifediol, which is converted by 1α-hydroxylase CYP27B1 to active 1,25(OH)2 vitamin D3, calcitriol, decreased total Aβ level to 55.1% in human neuroblastoma cells.