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New Vitamin D ₅ Analogue

Mehta et al. (p. 212) report that a new vitamin D ₅ analogue, la-hydroxyvitamin D ₅ , is a good candidate for cancer chemoprevention studies. They say it potently inhibits development of preneoplastic lesions in mouse mammary glands in organ culture, is nontoxic at a wide range of doses, and is less calcemic than 1 α,25-dihydroxyvitamin D ₃ , the biologically active analogue produced by the activation of vitamin D3 in fortified milk. The latter analogue is too calcemic for use in chemoprevention.

The study examined various activities of the vitamin D ₃ and D ₅ analogues, including their effects on vitamin D receptor (VDR) and transforming growth factor-β ₁ (TGF-β ₁ ) expression.

The investigators found that the vitamin D ₅ analogue induced VDR and TGF-β ₁ (which inhibits cancer cell growth) in normal mouse mammary tissue organ cultures. They speculate that VDR might be required for the analogue's chemopreventive activity, which may be mediated by induction of TGF-β ₁ .