Is there any relationship between interleukin-6/interleukin-6 receptor modulation and endogenous interleukin-6 release in metastatic malignant melanoma patients treated by biochemotherapy?

During recent years it has become clear that the production of most cytokines could play an important role in malignancies. We previously demonstrated that a high endogenous interleukin-6 (IL-6) level is significantly correlated with a high tumour burden and resistance to biochemotherapy in metastatic malignant melanoma patients. However, little is known about the origin of IL-6 and the pattern of IL-6 receptor (IL-6R) expression. In this report, we studied the expression of IL-6R and intracellular IL-6 using flow cytometry in tumour cells provided by fine-needle aspiration of lymph nodes and palpable metastatic lesions from 14 patients refractory to biochemotherapy and six responder patients. Moreover, we established the relationship between these parameters and the serum IL-6 level. Our results demonstrated that, following treatment, the percentage of HMB45-positive (HMB45+) cells expressing functional IL-6R, intracellular IL-6 or both IL-6R and IL-6 significantly decreased in patients refractory to biochemotherapy. In contrast, in responder patients the percentage of HMB45+ cells expressing IL-6R increased and those expressing IL-6 remained stable. Regarding the serum IL-6 level, an 11-fold increase was observed in the patients refractory to biochemotherapy, but only a 1.8-fold increase in the responder patients. In conclusion, in metastatic malignant melanoma patients with a poor prognosis, the endogenous production of IL-6 is concomitant with a decrease in functional IL-6R and intracellular IL-6 expression, suggesting the involvement of an IL-6/IL-6R complex.