[The role of cytokines in cancer therapy]

A variety of normal tissue or malignant cells can produce and/or release various biologically active substances (hormone-like mediators) now collectively called cytokines. Because immunological and non-immunological responses of malignant cells were modified by many of them, some cytokines have been employed as so-called Biological Response Modifiers (BRM) in the treatment of cancers in animals and humans. This overview discussed a few of the difficulties, probably inherent in cytokine therapy, that have already been encountered in early clinical trials as well as some of those that can be anticipated in future work. These include unexpected and undesirable reactions due to the systemic administration in relatively large amounts of a cytokine that is, under physiological conditions, supposed to act as a paracrine and/or autocrine among cells located within a limited distance. Even a pure recombinant preparation of a cytokine is now known to affect multiple target cells if they are accessible to it. Furthermore, this kind of therapy may sometimes be little more than a shot in the dark, since the physiological balance (homeostasis) among many of the cytokines present or produced in a host receiving a large quantity of exogenous cytokines is not well understood. Making the situation still more complicated, many types of tumor cells are known to release some of these cytokines spontaneously. Many challenging problems remain to be solved before we can confidently prescribe a cocktail of cytokines precisely suitable for a given patient according to the individual's in vivo cytokine profile. Nevertheless, in spite of all these reservations, cytokine therapy has been too frequently beneficial to be allowed to be discouraged. "Out of this nettle, danger, we pluck this flower, safety".