Modulation of interleukin-2-induced macrophage activation in cancer patients by the pineal hormone melatonin

The concomitant induction of immunosuppressive events, at least in part mediated by macrophages, would represent one of the mechanisms responsible for the lower activity of IL-2 in vivo than in vitro. Since macrophages have recently appeared to be under neuroendocrine control, the present study was carried out to evaluate the effect of the pineal neurohormone MLT on IL-2-induced macrophage activation during cancer immunotherapy, by determining serum levels of neopterin, which is a specific marker of macrophage activity. The study included 21 advanced cancer patients (lung cancer: 12; renal cancer: 9), 10 of whom received IL-2 subcutaneous therapy alone (1.8 x 10(6) IU/m2 twice daily), or IL-2 plus MLT (10 mg/day orally at 8.00 P.M.). Neopterin levels increased in all patients during IL-2 immunotherapy, but neopterin mean peak was significantly higher in patients treated with IL-2 alone than in those who received IL-2 plus MLT. This preliminary study would suggest the possible use of neurohormones to modulate host antitumor immune response during cancer immunotherapy with IL-2.