Human leukemic K562 cells: suppression of hemoglobin accumulation by a monoclonal antibody to human transferrin receptor.

The receptor for transferrin plays an important role both in tumor cell growth and in hemoglobin synthesis. In this paper, we demonstrate that the monoclonal antibody 42/6 to human transferrin receptor inhibits iron uptake in the human leukemic K562 cell line and suppresses hemoglobin accumulation in K562 cells induced to erythroid differentiation by butyric acid. In contrast, only slight inhibitory effects were observed on cell proliferation of both uninduced and erythroid-induced K562 cells treated with the 42/6 monoclonal antibody.

Methylation and expression of c-myc and c-abl oncogenes in human leukemic K562 cells before and after treatment with 5-azacytidine.

The correlation between expression and extent of DNA methylation of c-myc and c-abl oncogenes has been investigated in the human leukemic K-562 cell line before and after 5-azacytidine-mediated erythroid induction. RNA accumulation was analyzed by cytoplasmic dot hybridization and DNA methylation by using HpaII and MspI endonucleases, which differently cleave the CCGG sequence depending on cytosine methylation. Both the oncogenes are expressed in uninduced cells; however, whereas the c-myc expression does not change following 5-azacytidine treatment, the c-abl expression sharply decreases.

Efficient cell proliferation and predominant accumulation of epsilon-globin mRNA in human leukemic K562 cells which produce mostly Hb Gower 1.

Long-term cultures of K562(S) cells in 50-75 microM hemin allow the selection of 'hemin-resistant' K562 cells together with cells which proliferate efficiently while fully induced to express the human embryonic globin genes, as the hemoglobin Gower 1 (zeta 2 epsilon 2) is the predominant hemoglobin produced. Our experiments demonstrate that these K562 cells accumulate mostly epsilon-globin mRNA (epsilon-globin mRNA/gamma-globin mRNA = 2.9) suggesting that the control of hemoglobin expression is at a pretranslational level.

Human leukemia K562 cells: relationship between hemin-mediated erythroid induction, cell proliferation and expression of c-abl and c-myc oncogenes.

We have studied the expression of the c-myc and c-abl oncogenes in two human leukemic K562 cell lines which do express hemoglobin genes retaining a differential rate of cell proliferation. Our data indicate that in hemin-induced K562(S) cells the expression of c-abl oncogene decreases and appears to be related to a decrease in the proliferation capacity rather than to the activation of differentiated functions. The K562(hC) cell line, which produces large amounts of Hb Gower 1 retaining an efficient rate of cell proliferation, expresses indeed the c-abl oncogene at high level.