Proleukin TR – Chiron Pharmaceuticals
The youthful person normally has an ongoing search and destroy mechanism working constantly against cancer. This process is known as “immune surveillance”. The natural killer lymphocyte (NK cell) is the killing effector (hit man) of the immune surveillance mechanism. IL-2 is a direct stimulant of NK cells. NK cells may decline in old age or cancer. During treatment with IL-2, assays for NK cells as a percentage of total lymphocytes will usually rise.
Dr. Steven Rosenberg at the National Cancer Institute has employed large doses of IL-2 in successfully inducing sustained remissions and apparent cures in patients with metastatic melanoma and renal cell carcinoma, two types of cancer notoriously resistent to radiotherapy and chemotherapy. IL-2 has produced a very significant lengthening of median and mean survival with apparent cures. Cure in the treated patients is suggested by a flat survival curve.
An editorial appeared in the same issue of the Journal of the American Medical Association as Rosenberg’s paper on IL-2 . In this editorial, Samuel Helman states:
” What then have we learned from this clinical experiment? The initial hypothesis was that it was possible to stimulate the host immune response to become an effective antitumor agent. The report by Rosenberg in this issue of THE JOURNAL clearly supports this hypothesis and is best regarded as a ‘proof of principle’. Interleukin-2 has no direct antitumor activity. It appears to act by causing the production of lymphokine activated killer cells and expanding the population of T-cells that can destroy target cells. Rosenberg, et al. have demonstrated that IL-2 treatment has resulted in clear, and in some cases dramatic, tumor regression. ……We are impressed with the duration of the complete responses. …..We should conclude that this study represents a significant advance in cancer therapy because of the novel mechanism of action of IL-2 and the long duration of complete responses.”