The vitamin D receptor-mediated activation of phosphatidylinositol 3-kinase (PI3Kα) plays a role in the 1α,25-dihydroxyvitamin D3-stimulated increase in steroid sulphatase activity in myeloid leukaemic cell lines

In this article we show that 1 alpha,25-dihydroxyvitamin D-3 (1 alpha,25(OH)(2)D-3) stimulates the activity of the class IA phosphatidylinositol 3-kinase PI3K alpha and its downstream target Akt in HL60, U937 and THP-1 myeloid leukaemic cell lines. Furthermore, we show that the classical nuclear vitamin D receptor (VDRnuc) is involved in this activation of the PI3K/Akt signalling in these cell lines. We have previously shown that the activity of steroid sulphatase is stimulated in HL60, U937 and THP-1 myeloid leukaemic cell lines by 1 alpha,25(OH)(2)D-3 (Hughes et al., [2001] Biochem J 355:361 -371; Hughes et al. [2005] J Cell Biochem 94:1175-1189; Hughes and Brown [2006] J Cell Biochem 98:590-617). In this article we show that the 1 alpha,25(OH)(2)D-3-stimulated increase in signalling via the PI3K/Akt pathway plays a role in the increase in steroid sulphatase activity in the HL60 U937 and THP-1 cell lines. We used a variety of pharmacological and biochemical approaches to show that activation of PI3K alpha mediates the 1 alpha,25(OH)(2)D-3-stimulated increase in steroid sulphatase activity in myeloid leukaemic cells. We also show that the PI3K/Akt dependent activation of NF-kappa B plays a role in the 1 alpha,25(OH)(2)D-3-stimulated increase in steroid sulphatase activity in myeloid leukaemic cells.