SPECIFIC UPTAKE OF 1,25-DIHYDROXYCHOLECALCIFEROL BY HUMAN CHRONIC MYELOID-LEUKEMIA CELLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (8) , 3627-3631
Abstract
Mononuclear cell preparations from patients with chronic myeloid leukemia [CML] were examined for binding of and response to 1,25-dihydroxycholecalciferol[1,25-(OH)2D3]. Whole cells specifically took up [3H]-1,25-(OH)2D3 with high affinity (Kd 3.6 .times. 10-11 M) and low capacity. Subcellular fractionation of labeled cells showed that binding was restricted to cytosols and nuclei. Sucrose gradient centrifugation of cells preincubated with [3H]-1,25-(OH)2D3 revealed a single 3.6S peak which was totally displaced with 100-fold excess nonradioactive hormone. Specific binding of 1,25-(OH)2D3 could not be demonstrated by postlabeling standard cytosol preparations. Cytosols prepared from a mixture of CML cells and 1,25-(OH)2D3 receptor-positive T47D (human breast cancer) cells had < 10% of the binding measured in T47D cytosol alone. The levels of binding in T47D cytosols were not reduced if the receptors were occupied with [3H]-1,25-(OH)2D3 prior to the addition of the CML cytosols. CML cells appear to contain both the receptor for 1,25-(OH)2D3 and an unknown substance which prevents its detection following the preparation of cytosol. Cells from patients with CML in the chronic phase specifically bound more 1,25-(OH)2D3 [18.0 .+-. 3.2 (SE) fmol/107 cells] than did those in acute myeloid transformation [7.2 .+-. 1.5] or than did cells from patients with acute myeloid leukemia [2.6 .+-. 0.8]. Only cells from the 1st group of patients responded to the addition of 1,25-(OH)2D3 by differentiating along the monocyte-macrophage pathway. The differentiation-induction effect of 1,25-(OH)2D3 is likely to depend on adequate levels of receptor and that intact cells rather than cytosol preparations should be studied before cells of a particular tissue are designated as receptor negative.