Cytokine-Induced Radiation Protection and Sensitization.

Cytokines, hormone-like proteins that are produced by stimulated cells and tissues, serve as intercellular messengers. The cloning and large-scale production in a recombinant form of an expanding number of cytokines in the past decade has permitted investigations aimed at assessing the benefit they may provide in preserving and restoring functions of tissues compromised by irradiation. This review focuses primarily on the preclinical and clinical findings of a number of radiation and chemotherapy studies in which cytokines were found to protect, restore, or at times harm the hematopoietic and gastrointestinal tissues, as well as lung and liver, against cytotoxic therapies. Included are the myelorestorative effects of cytokines, their application in mobilization of peripheral blood progenitor cells for bone marrow transplantation, and their myeloprotective effect when given before irradiation. Studies indicating the importance of the treatment schedule, and in some cases their contrasting effects on different tissues, are included. The insights gained from such studies into the mechanisms of regulation by cytokines of radiation-induced damage are discussed.