1,24(S)-dihydroxyvitamin D2, an endogenous vitamin D2 metabolite, inhibits growth of breast cancer cells and tumors.

Background: 1,24-Dihydroxyvitamin D2 (1,24(OH)2D2) is a naturally occurring metabolite of vitamin D2 with low calcemic activity and potent antiproliferative activity. We evaluated the activity of 1,24(OH)2D2 in breast cancer models.

Materials And Methods: The antiproliferative activity of 1,24(OH)2D2 was quantitated against human and murine breast cancer cell lines.

Effects of vitamin D compounds on renal and intestinal Ca2+ transport proteins in 25-hydroxyvitamin D3-1alpha-hydroxylase knockout mice.

Background: Vitamin D compounds are used clinically to control secondary hyperparathyroidism (SHPT) due to renal failure. Newer vitamin D compounds retain the suppressive action of 1,25(OH)(2)D(3) on the parathyroid glands and may have less Ca(2+)-mobilizing activity, offering potentially safer therapies.

Methods: This study investigated the effect of a single dose of compound (1,25(OH)(2)D(3), 1,24(OH)(2)D(2), or 1alpha(OH)D(2)) on renal and intestinal Ca(2+) transport proteins, including TRPV5 and TRPV6, and serum Ca(2+), in a novel SHPT model, the 25-OH-D(3)-1alpha-hydroxylase knockout mouse, which lacks endogenous 1,25(OH)(2)D(3) and is severely hypocalcemic.