Biological response modifiers in cancer therapeutics: potentialities and limitations.

With increased knowledge of the mechanisms of host defenses against tumors, both immunological and nonimmunological in nature, and of the relationships between tumors and host cells, it becomes possible to develop agents aimed at modifying those relationships to therapeutic advantage. The task is facilitated by the advent of recombinant DNA technology, which makes it possible to produce biologicals in quantity and purity adequate for studies in vivo. The potentialities of biological response modifiers (BRMs) are primarily due to their specificity and/or selectivity of action, whether these attributes are related to receptors/antigens present on neoplastic cells or on cells of the immunological regulatory networks or to nonspecific activation of host defenses. The limitations are related to the fact that in certain cases treatments are too specific for a tumor cell within a heterogeneous cell population; these agents also show toxicities that, albeit usually unrelated to their antitumor action, can in some cases be severe.