INDUCTION OF DIFFERENTIATION IN ERYTHROLEUKEMIC K562 CELLS BY GAMMA-IRRADIATION

Various agents have been shown to induce differentiation in neoplastic cells. The present study aimed at investigating comparable phenomena induced by high doses of gamma-irradiation in the presence of physiolo gical factors. The erythroleukemic K562 cells were gamma-irradiated or treated with cytosine-arabinoside (Ara-C), and examined for cell size , protein content, acetylcholinesterase (AChE)-activity and hemoglobin synthesis in relation to mitotic activity. At doses above 10 Gy, diff erentiation was induced, as recognized by elevated AChE-activity, acco mpanied by an increase in cell size and protein content and cessation of cell proliferation. Moreover, irradiation, as well as Ara-C, induce d hemoglobin synthesis when cultures were supplemented with hemin prio r to treatment, It is suggested that the basic mechanisms of different iation induction are similar for ionizing radiation and certain chemic al agents and are related to continued growth of essential cytoplasmic constituents during inhibition of mitotic activity.