Induction of apoptosis and inhibition of prostate and breast cancer growth by BGP-15, a new calcipotriene-derived vitamin D3 analog

The role of vitamin D-3 in cancer prevention and its potential as an anticancer therapeutic agent have been researched and are well established. However, the clinical use of the natural vitamin D-3 metabolite, 1 alpha,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3 or calcitriol] is limited by a possible cause of hypercalcemia and hypercalciuria. A new 24-chloro calcipotriene-based vitamin D-3 analog (BGP-15) was synthesized and examined for antiproliferative activity in the androgen-dependent cell lines of prostate cancer (LNCaP) and breast cancer (MCF-7). The new analog led to significant decrease in cell viability in cultured LNCaP and MCF-7 cell lines compared with calcipotriene and 1,25(OH)(2)D-3. We observed elevated vitamin D receptor protein levels in both LNCaP and MCF-7 cells, which were treated with 5 mu mol/l of 1,25(OH)(2)D-3, calcipotriene or BGP-15 for 20 h, indicating vitamin D receptor-binding ability. Treatments of LNCaP and MCF-7 cells with 5 mu mol/l BGP-15 and calcipotriene for 20 h generated procaspase-3 cleavage and therefore, apoptosis. Interestingly, BGP-15, and to a lesser extent calcipotriene, but not 1,25(OH)(2)D-3, activated caspase-3 in MCF-7 cells, a cell line that normally lacks this specific caspase (and procaspase). It is presumed that management of MCF-7 with BGP-15 modulates procaspase-3 expression and cleavage, and a subsequent activation of caspase-3. Similar treatments of LNCaP cells induced procaspase-9 cleavage and therefore caspase-9 activation, whereas similar treatments of MCF-7 cells failed to induce caspase-9 activation. Cytochrome c release was, however, detected in both cell lines, LNCaP and MCF-7. In-vivo results suggested that BGP-15 (similar to its parent drug) did not cause calcium-related toxic side effects after chronic treatment. Anti-Cancer Drugs 21:609-618 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.