Tumor promoter-mediated inhibition of cell differentiation: suppression of the expression of erythroid functions in murine erythroleukemia cells.

Abstract

Previous studies demonstrated that 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a tumor promoter, is a potent inhibitor of inducer-mediated differentiation of murine erythroleukemia cells. Inhibition of cell differentiation was associated with inhibition of cell growth. The present studies, employing a cell line adapted for growth in TPA, demonstrate that inhibition of differentiation is not dependent upon inhibition of cell growth or a change in the cellfdivision cycle; neither is inhibition of differentiation accompanied by detectable effect on cell uptake of [3H]hexamethylene bisacetamide, the inducer used in these studies. TPA causes an inhibition of expression of all hexamethylene bisacetamide-inducible erythroid characteristics measured, including commitment to terminal cell division, accumulation of globin mRNA, and synthesis of globins, spectrin, heme synthetic enzymes (5-aminolevulinic acid dehydratase and uroporphyrinogen-I synthase) and heme. A hypothetical model for the inhibitory action of tumor promoters on terminal cell differentiation is discussed. 12-0-Tetradecanoyl-phorbol-13-acetate (TPA) is one of a group of plant diterpenes that are tumor promoters in the two-stage mouse skin carcinogenesis system (1-4). TPA is a reversible inhibitor of cell differentiation in several in vitro systems, including murine erythroleukemia cells (MELC) (5, 6), murine neuroblastoma cells (7), chicken myoblasts and chondroblasts (8,9), and the fibroblast-adipocyte conversion (10). It has been postulated that tumor promotion itself may involve interference in the process of differentiation (1, 6, 11). Of the several systems examined to date, MELC is the best characterized with respect to the molecular events during expression of differentiation. Upon exposure to various agents such as dimethyl sulfoxide (12), hexamethylene bisacetamide (HMBA) (13), or butyric acid (14), these cells initiate erythroid differentiation, including characteristic morphological changes (12), synthesis and accumulation of globin mRNA (15-18), synthesis of a and ( globins (19,20), increase in spectrin content (21,22), increase in the activity of heme synthetic enzymes and heme content (23,24), and loss of the capacity for cell division (12,25,26).We have previously found that TPA-mediated inhibition of differentiation is accompanied by an early and pronounced inhibition of cell growth (6,27). In the present studies we demonstrate that an effect on cell growth is not required for the effect on differentiation. Furthermore, we show that, under conditions in which TPA has no detectable effect on cell growth or uptake of inducer, it inhibits the expression of many characteristics of erythroid differentiation, including commitment to terminal cell division and accumulation of globin mRNA, globin, spectrin, heme synthetic enzymes, and heme. MATERIALS AND METHODSMELC, subclone DS19-1OTS, a TPA-sensitive cell line isolated from strain 745A-DS19, was maintained in culture and characterized as described (27). DS19-1OTS(TPA) cells were obtain...

Antagonism between Epidermal Growth Factor and Phorbol Ester Tumor Promoters in Human Breast Cancer Cells

“…The phorbol esters appear to interact with a mechanism involved with control of differentiation in other in vitro animal model systems, but inhibition of spontaneous and induced differentiation has usually resulted (34)(35)(36)(37)(38)(39)(40)(41)(42). Different results have been reported with human-derived cells.…”

Nuclear proteins that bind the human gamma-globin gene promoter: alterations in binding produced by point mutations associated with hereditary persistence of fetal hemoglobin.

“…We have observed little or no reduction in the concentration of any of the proteins studied after 4-day stimulation of K562 cells with 25 ,uM hemin. Under these conditions, 75% of cells were benzidine positive (16), and 95% excluded trypan blue. When we tested 50 ,uM hemin, the number of benzidine-positive cells increased only slightly, but more than 70% of cells were damaged by the trypan blue criteria.…”

Phorbol diesters stimulate the development of an early murine progenitor cell. The burst-forming unit-megakaryocyte.

“…Finally, the lack of erythropoietin responsiveness in these progenitor cells is further evidence of their lineage restriction. However, it should be noted that PMA has been reported to inhibit erythroid colony formation (28,29). Its presence may thus mask the actions of erythropoietin in these cultures.…”