Insulin-Like Growth Factors and Hematologic Malignancies

TO THE EDITOR:

In their excellent review on the family of insulin-like growth factors (IGF) and cancer, LeRoith and colleagues [1] described the current knowledge of the role of the IGFs and of their receptors and binding proteins in certain solid tumors. However, the authors did not mention the involvement of the IGF system in the growth and development of neoplastic hematologic processes. We recently reviewed the relevant literature on the role of the IGF system in the regulation of normal and malignant hematopoiesis [2]. Nearly all hematopoietic cells, either normal or neoplastic, express the receptors of IGF, and some even produce IGFs or their binding proteins. Insulin-like growth factors seem to be involved in normal erythropoiesis, granulopoiesis, and lymphopoiesis. The growth factors are also mitogenic for cell lines of promyelocytic leukemia [3], acute myeloid leukemia [4], erythroleukemia, and Burkitt lymphoma and may stimulate proliferation of B-cell and T-cell acute lymphocytic leukemia and erythroid progenitors in polycythemia vera [5]. The differentiation of certain immature malignant cell lines as myeloid leukemias or B-cell or T-cell acute lymphocytic leukemia to their mature counterparts is usually accompanied by a decrease in the number and affinity of IGF-1 receptors on cells.