Effect of endogenous interleukin-6 on Fas (APO-1/CD95) receptor expression in advanced melanoma patients

Interleukin-6 (IL-6) has been shown to support either autocrine or paracrine growth in melanoma, and may prevent programmed cell death in different cell types. We have previously demonstrated that the endogenous IL-6 level is significantly correlated with tumor burden and nonresponse to biochemotherapy in metastatic malignant melanoma patients. In the present study, we investigated the relationship between endogenous IL-6 and apoptosis signal through Fas (APO-1/CD95) receptor expression in 9 responder and 15 refractory patients with metastatic disease treated by biochemotherapy. Before any treatment, double immunostaining demonstrated that 61.5% of the tumor cells were HMB45+CD95+. At day 49 in refractory patients, a significant decrease (p = 0.04) of total Fas expression was observed. Furthermore, a significant reduction (p = 0.032) in the percentage of HMB45+CD95* cells occurred. An 11-fold increase in serum IL-6 level was detected (p < 0.002). This increase was negatively correlated (r = -0.2, p = 0.008) with the decrease in total Fas expression. However, in responding patients, no detectable decrease in Fas expression was observed, while a very low increase in serum IL-6 (2-fold) was detected. These results suggest that the increased endogenous IL-6 level in refractory patients may inhibit apoptosis via modulation of Fas expression. These preliminary results must be interpreted with caution, and further study with a greater number of patients is needed to understand the mechanism by which IL-6 inhibits apoptosis in melanoma.