Monocyte release and plasma levels of interleukin-6 in patients irradiated for cancer.

Interleukin-6 (IL-6) release from purified blood monocytes was determined in patients with breast cancer or prostatic cancer before and after radiation treatment (Rx). Plasma levels of IL-6 and neopterin were also determined. Spontaneous IL-6 release in vitro was higher in breast than in prostatic cancer or in controls. Strong lipopolysaccharide (LPS)-induced cellular IL-6 release was detected in breast cancer and controls but was subnormal in prostatic cancer. Addition of indomethacin to cultures had no effect on IL-6 release. Rx generally increased levels of in vitro released IL-6 and raised LPS-stimulated IL-6 secretion in prostatic cancer to normal. Plasma levels of IL-6 were lower in breast than in prostatic cancer or controls. Rx resulted in a tendency towards raised levels in both patient groups suggestive of monocyte activation. In accordance with this, plasma levels of neopterin, which were normal before treatment, increased in prostatic cancer patients after Rx. Taken together, the results of this study indicate that monocyte release as well as plasma levels of IL-6 are affected by the malignant state as well as by radiation treatment. In view of the antiproliferative effects of IL-6, the findings may have bearing on the pathogenesis and treatment of malignant disease.