Effects of Calcitriol on the Expression of Endogenous Antioxidant Enzymes in Canine Bladder Transitional Cell Carcinoma Cells

The hormonally active form of vitamin D, calcitriol (1,25-dihydroxyvitamin D₃), is now known as an important player in many biological areas beyond calcium and phosphate metabolism. These include cancer, immunity, development, heart disease and others. Studies have shown that higher levels of serum vitamin D are associated with greater survival and reduced incidence of multiple types of cancers. We have previously shown that calcitriol, as well as analogs of vitamin D, decrease proliferation and induce differentiation of canine cancer squamous cell carcinoma cells in vitro. In order to further characterize these effects, we have performed gene expression analysis of canine bladder transitional cell carcinoma cells in vitro in response to calcitriol and the vitamin D analog seocalcitol (25-dihydroxy-22,24-diene-24,26,27-trihomovitamin D). Due to the involvement of reactive oxygen species and cancer, we have also investigated calcitriol's and seocalcitol's ability to affect the expression of endogenous antioxidant enzymes at the gene, protein and activity level.