1,25-Dihydroxyvitamin D3 receptor-like macromolecule in rat osteogenic sarcoma cell lines

Abstract

The hormonal metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), exerts its biological effects by initially binding to a cytosolic receptor protein. Such a protein has been demonstrated in the target organs of vitamin D3 including bone. Although the role of 1,25(OH)2D3 on the skeleton has been extensively studied in normal bone, nothing is known about its effects, if any, in abnormal bone growth. Rat osteogenic sarcoma is a useful model for bone malignancy. Tumor cells retain differentiated functions including the ability to form bone and to respond to parathyroid hormone, prostaglandins, and to a smaller extent to calcitonin with increases in cyclic AMP levels. We have here evaluated osteogenic sarcoma cell lines for the presence of a receptor for 1,25(OH)2D3. We have utilized sucrose gradient sedimentation, saturation analysis, and DNA-cellulose chromatography. Cytosol preparations from these cell lines contain a 3.3 S saturable macromolecule which binds 1,25(OH)2D3 with specificity and high affinity (Kd = 2 x 10(-10) M). The sterol-macromolecule complex binds to DNA-cellulose and its elution profile from this affinity resin is similar to that of the 1,25(OH)2D3 receptor from normal rat bone. These tumor cells should serve as a useful model for studying the action of 1,25(OH)2D3 in bone and the role of this metabolite in the biology of bone malignancy.