Novel Deuterated Gemini-Vitamin D3 Analogs Have Potent Antitumor Activity.

Abstract

The active form of vitamin D3, 1,25(OH)2D3, is an important regulator of calcium and bone metabolism. Also, it inhibits proliferation and induces differentiation of a variety of malignant cells. Here, we synthesized a new class of vitamin D3 analogs, which have a C-20 methyl group and a deuterium substituted basic side chain [Deuterated Gemini (DG)]. Six DG analogs were evaluated for their ability to inhibit growth of myeloid leukemia (HL-60), prostate (LNCaP and PC-3), lung (H520) and breast (MCF-7) cancer cell lines. All 6 DG analogs inhibited growth in a dose-dependent manner and had very similar potency. Most effective DG, BXL-01-0120, was over 70-fold more potent than 1,25(OH)2D3 in inhibiting 50% clonal growth (ED50) of HL-60, LNCaP, PC-3, H520 and MCF-7 cells with ED50s ranging from 10−11 M to 10−13 M. Focusing on this analog for further analyses, pulse-exposure, wash and culture experiments showed that 48 hours exposure of HL-60 cells to BXL-01-0120 (10−9 M) had potent anti-proliferative activity (82% growth inhibition compared to diluent control cells). Cell cycle assays found that BXL-01-0120 (10−10 M, 4 days) increased the percent of cells in the G0/G1-phase (61%, diluent control 47%) associated with a decrease S-phase (18%, diluent control 42%). BXL-01-0120 (10−10 M, 4 days) caused apoptosis in approximately 15% of cells. 1,25(OH)2D3 at the same concentration and duration changed neither the cell cycle nor number of cells undergoing apoptosis compared to control HL-60 cells. BXL-01-0120 (10−10 M, 4 days) strongly induced expression of the CD11b and CD14 (monocyte / macrophage differentiation markers) on HL-60 cells (87%); in contrast, 1,25(OH)2D3(10−10 M) stimulated a mean 43% of the cells to express these cell surface proteins. In summary, DGs strongly inhibited clonal proliferation, induced differentiation and cell cycle arrest in several types of cancer cells, especially HL-60 cells, suggesting that further preclinical and clinical studies to explore their anticancer potential are warranted.