Vitamin D and retinoblastoma. The presence of receptors and inhibition of growth in vitro

The vitamin D receptor has been found in several human organs not involved in calcium metabolism and in several malignant neoplasms found in humans. The role of the receptor in these tissues is unclear. There is, however, a relationship between the presence and quantity of the vitamin D receptor in a malignant cell line and the antineoplastic effect of vitamin D on that cell line. We found that Y-79 retinoblastoma cells have receptors specific for calcitriol (1,25-dihydroxycholecalciferol). Scatchard analysis of the receptor data shows a quantity of 56,000 receptors per retinoblastoma cell. These receptors have a dissociation constant of 1.18 nmol/L. Retinoblastoma cells treated with 10^-9 mol/L of calcitriol for nine days had 15% less cell growth than the control cells. Further studies of the effect of vitamin D on retinoblastoma may warrant its inclusion in chemotherapeutic protocols for the treatment of this childhood affliction.