We identified a novel vitamin D analog, 1 alpha-hydroxy-24 ethyl vitamin D5 (1 alpha(OH)D5) that showed potent growth inhibitory and cell- differentiating actions in breast cancer cells. Based on our findings in vitro and in vivo, we hypothesized hat 1 alpha (OH)D5 (D5), when administered to women with breast cancer, will induce differentiation of dedifferentiated cells and thereby prevent progression of malignancy. 1999-2000, we completed preclinical studies in rats, showing ...