Novel vitamin D-3 analog, 21-(3-methyl-3-hydroxy-butyl)-19-nor D-3, that modulates cell growth, differentiation, apoptosis, cell cycle, and inductionof PTEN in leukemic cells

The active form of vitamin D-3, 1,25(OH)(2)D-3, inhibits proliferation and induces differentiation of a variety of malignant cells. A new class of vit amin D-3 analogs, having 2 identical side chains attached to carbon-20, was synthesized and the anticancer effects evaluated. Four analogs were evalua ted for their ability to inhibit growth of myeloid leukemia (NB4, HL-60), b reast (MCF-7), and prostate (LNCaP) cancer cells. All 4 analogs inhibited g rowth in a dose-dependent manner. Most effective was 21-(3-methyl-3-hydroxy -butyl)-19-nor D-3 (Gemini-19-nor), which has 2 side chains and removal of the C19. Gemini-19-nor was approximately 40 625-, 70-, 23-, and 380-fold mo re potent than 1,25(OH)(2)D-3 in inhibiting 50% clonal growth (ED50) of NB4 , HL-60, MCF-7, and LNCaP cells, respectively. Gemini-19-nor (10(-8) M) str ongly induced expression of CD11b and CD14 on HL-60 cells (90%); in contras t, 1,25(OH)(2)D-3 (10-8 M) stimulated only 50% expression. Annexin V assay showed that Gemini-19- nor and 1,25(OH)(2)D-3 induced apoptosis in a dose-d ependent fashion. Gemini-19-nor (10(-8) M, 4 days) caused apoptosis in appr oximately 20% of cells, whereas 1,25(OH)(2)D-3 at the same concentration di d not induce apoptosis. Gemini-19-nor increased in HL-60 both the proportio n of cells in the G(t)/G(o) phase and expression level of p27(idp1). Moreov er, Gemini-19-nor stimulated expression of the potential tumor suppressor, PTEN. Furthermore, other inducers of differentiation, all-trans-retinoic ac id and 12-O-tetradecanoylphorbol 13-acetate, increased PTEN expression in H L-60. In summary, Gemini-19-nor strongly inhibited clonal proliferation in various types of cancer cells, especially NB4 cells, suggesting that furthe r studies to explore its anticancer potential are warranted. In addition, P TEN expression appears to parallel terminal differentiation of myeloid cell s. (Blood. 2001;97:2427-2433) (C) 2001 by The American Society of Hematolog y.