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

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 (K(d)=2x10^-10 M). The sterolmacromolecule 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.