SYNERGISTIC DIFFERENTIATION OF U937 CELLS BY ALL-TRANS-RETINOIC ACID AND 1-ALPHA,25-DIHYDROXYVITAMIN-D3 IS ASSOCIATED WITH THE EXPRESSION OF RETINOID-X RECEPTOR-ALPHA

Among the nuclear hormone receptors, the retinoid X receptors (RXRs) p lay a central role through their ability to heterodimerize with other members of this family of transcription factors, including retinoic ac id (RA) and vitamin D (VD3) receptors. We have previously found that a ll-trans retinoic acid and 1 alpha, 25-dihydroxyvitamin D3 cooperate t o induce monocytic differentiation of U937 human leukemic cells. Here the expression of RXR alpha protein in myelomonocytic cells was studie d by immunodetection using polyclonal antibodies. RXR alpha was detect ed upon exposure of cells to VD3 and higher levels were found in cells treated by combinations of RA and VD3 under conditions where both age nts synergized for inducing monocytic properties. (C) 1994 Academic Pr ess, inc.