title: Inhibition of hemoglobin accumulation by monoclonal antibodies to the human transferrin receptor is reversed by hemin.
abstract: We have studied the effects of hemin on the inhibition of K562 cell erythroid differentiation mediated by a monoclonal antibody to the human transferrin receptor. In the absence of hemin, the monoclonal antibody 42/6 suppresses the increase of hemoglobin accumulation induced by butyric acid or 5-azacytidine (5-azaCR). In contrast, in the presence of hemin, the hemin-resistant K562(h) cell line is induced to hemoglobin production by treatment with 5-azaCR even in the presence of the monoclonal antibody to human transferrin receptor. The results obtained suggest (1) that the human leukemic K562 cells treated with monoclonal antibodies to human transferrin receptor might retain molecular properties similar to those found in erythroid cells from subjects affected by alterations of iron metabolism, and (2) that hemin might allow hemoglobin synthesis in erythroid cells whose iron uptake is inhibited by monoclonal antibodies to human transferrin receptors.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001374:Azacitidine / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D006418:Heme / Q000494:pharmacology*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute / Q000503:physiopathology; D007942:Leukemia, Experimental / Q000503:physiopathology; D051379:Mice; D011990:Receptors, Transferrin / Q000187:drug effects / Q000276:immunology / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D006454:Hemoglobins; D011990:Receptors, Transferrin; D006418:Heme; D001374:Azacitidine