RETINOIC ACID-BINDING PROTEIN IN A HUMAN CELL (MCF-7) FROM BREAST-CARCINOMA

  • 1 January 1980
    • journal article
    • research article
    • Vol. 42  (5) , 490-494
Abstract
A specific retinoic acid-binding protein was demonstrated by sucrose density gradient centrifugation and saturation binding analysis in MCF-7 human breast cancer cells. Retinol-binding protein could not be detected in this cell line. By Scatchard analysis, this retinoic acid-binding protein had a dissociation constant (Kd) of 154 nM and bound a maximum of 14 pmoles of [3H]retinoic acid per mg of cytoplasmic protein. Experiments with intact attached cells revealed the Kd to be 125 nM, which is very close to the value obtained for cytoplasmic extract. The binding of [3H]retinoic acid was abolished by unlabeled retinoic acid. Retinal and .alpha.-retinoic acid competed for binding sites but were less potent than unlabeled retinoic acid. Retinol, retinyl acetate and the analog Ro 10-9359 showed little or no competition for the retinoic acid-binding site. A specific retinoic acid-binding protein was also demonstrated by gel electrophoresis. The presence of retinoic acid binding protein in MCF-7 cells suggests that the biologic effects of retinoic acid may be mediated by this specific protein. [Retinoic acid has antineoplastic effects on some tumors.].