Hematopoietic growth factors: current knowledge, future prospects

The introduction of hematopoietic growth factors into clinical medicine represents one of the more exciting developments in oncology in the past several years. The identification, gene cloning, and large-scale production of hematopoietic growth factors represent important examples of the practical benefits that may accrue from application of the sophisticated technology derived from recombinant DNA research. Research, both at the bench and by the bedside, has proceeded at an extraordinarily rapid pace in this field over the past five years, leading to an abundance of new information, novel promising agents, and important clinical controversies related to the biology and appropriate clinical applications of hematopoietic growth factors. With these agents, for the first time in history, the production of human blood cells can be systematically manipulated in vivo in an effort to optimize physiology beyond the endogenous host response. Additionally, investigators utilizing purified hematopoietic growth factors as reagents may provide crucial insights into the mechanisms of blood cell production in health and in various disease states. This review aims to summarize the current state of knowledge regarding the control of blood cell production by specific factors and to put these data in the context of clinical medicine. The emphasis will be on factors that primarily influence myeloid (rather than lymphoid) cell growth, differentiation, and activation, and the clinical focus will be on applications in oncologic therapeutics and in the treatment of primary hematologic disorders. By reviewing what we know and what has already been done, we may be better able to define the important questions that remain and to formulate the means to answer our current uncertainties about the activities and clinical uses of hematopoietic growth factors.