Expression of insulin-like growth factors IGF-I and IGF-II, and their receptors during the growth and megakaryocytic differentiation of K562 cells

Insulin-like growth factors (IGFs) I and II are critical regulators of cell proliferation and differentiation and most of the growth promoting properties of both ligands are mediated by IGF-I receptor (IGF-IR). In the present study we have investigated the role of IGFs in K562 cell line during normal growth and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced megakaryocytic differentiation. Abundant expression of IGF-I, IGF-II and IGF-IR was demonstrated in resting cells and exogenous IGF-I and IGF-II increased 3 H-thymidine incorporation in a dose dependent manner. In contrast, we found that basal growth of the cells was inhibited by using anti-IGF-IR mAb. Furthermore, also IGF-I and IGF-II induced DNA synthesis was significantly suppressed by anti-IGF-IR mAb. During megakaryocytic differentiation, expression of IGF-IR increased during first 12 h, but after that the expression started to decrease together with IGF-I. Taken together, our data suggest that autocrine production of IGF-I and IGF-II may via IGF-IR play a significant role in the growth and megakaryocytic differentiation of K562 cells. (C) 2002 Elsevier Science Ltd. All rights reserved.