Differentiation and malignant transformation: two roads diverged in a wood.

Growth factors and their receptors are known to send at times contradictory signals, such as proliferation or differentiation. Recent developments in our knowledge of growth factor receptors and their signaling pathways have clarified the basis for this puzzling behavior. Separate domains of a receptor and/or the availability of specific substrates determine the fate of a cell stimulated by the same growth factor. In some models, the difference between malignant transformation and differentiation (leading to cell death) may depend on the presence or absence of a single agonist or antagonist molecule. The type 1 insulin-like growth factor receptor will serve as the paradigm for this review. J. Cell. Biochem. Suppls. 32/33:68-75, 1999. Copyright 1999 Wiley-Liss, Inc.