Effects of calcitriol, seocalcitol, and medium-chain triglyceride on a canine transitional cell carcinoma cell line.

BACKGROUND Transitional cell carcinoma (TCC) in dogs is associated with high morbidity and mortality. Calcitriol and its analog seocalcitol, combined with medium-chain triglyceride (MCT), have potential for the treatment of this disease. MATERIALS AND METHODS TCC cells were treated with calcitriol or seocalcitol, alone or combined with MCT. Cell growth, cell cycle kinetics, vitamin D receptor (VDR) localization and expression, and Bcl-2 expression were measured. RESULTS Canine TCC expresses high levels of nuclear VDR. Furthermore, calcitriol and seocalcitol significantly inhibited cell growth and calcitriol caused G0/G1 cell cycle arrest. Bcl-2 expression was slightly decreased in cells treated with these compounds, although no significant changes in VDR expression were observed. MCT enhanced the growth inhibitory effect of both compounds. CONCLUSION Calcitriol and seocalcitol inhibited TCC cell growth via induction of cell cycle arrest and MCT enhanced this effect. Therefore, calcitriol and seocalcitol with MCT may have therapeutic potential for canine bladder cancer.