Comparison of the in vitro cytotoxicity of Vitamin D analogs, calcitriol and alpha- calcidol, in mouse and human tumor cell lines Hilary J. Shmeeda, Lidia Mak, Jenny Gorin, Alberto Gabizon. Shaare Zedek Medical Center, Jerusalem, Israel. Vitamin D3 (VD3), involved in calcium and mineral metabolism, is a potent regulator of cell growth, differentiation, and more recently has been shown to affect apoptosis, tumor invasiveness, and angiogenesis. It has demonstrated significant cytotoxic abilities both in androgen-sensitive and insensitive prostate cancer cells as well as in a number of other tumor types expressing the VD3 receptor including colon carcinoma (ca), breast ca and malignant melanoma. We compared the cytotoxic effects of calcitriol [1,25(OH)2D3], the active and most potent physiologic form of VD3, to alpha-calcidol [1 alpha(OH)D3], a vitamin D analog used clinically which lacks the hydroxyl group in the 25 position of calcitriol, and to cholecalciferol, a VD3 prodrug. The cytotoxic effects of these vitamin D3 analogs on a number of mouse (C-26, M109, M109R) and human (PC-3, KB, A375, PANC-1) tumor cell lines were examined after 72-hour continuous exposure using a colorimetric assay in 96-multiwell plates. Broad-spectrum cytotoxicity with IC50 values ranging from 1-20 ìM were found. Alpha-calcidol was a 2- to 3-fold more potent cytotoxic agent irrespective of multidrug resistance phenotype compared to calcitriol. Both, alpha-calcidol and calcitriol were significantly more cytotoxic than cholecalciferol. Apoptosis was confirmed based on the TUNEL assay. Alpha-calcidol appears to be a highly active vitamin D analog with potential value in cancer therapy, despite being an incomplete form of VD3. Abstract 2255, AACR 2005 Abstract 1601, AACR, 2005 Abstract 5814 AACR, 2005 Abstract 4545 AACR, 2005 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.