An unexpected inverse correlation between soluble epidermal growth factor receptor and interleukin-6 in metastatic malignant melanoma patients

The exact role of the soluble form of epidermal growth factor receptor (sEGF-R) in melanoma disease remains to be determined. We focused this study on the detection of circulating levels of sEGF-R in metastatic malignant melanoma patients and on the possible relationship between sEGF-R and clinicobiological parameters including circulating interleukin-6 (IL-6) and survival. sEGF-R and IL-6 levels were determined using a highly sensitive enzyme-linked immunosorbent assay in serum from 75 metastatic malignant melanoma patients and 30 healthy controls. In our patients, median sEGF-R level was significantly elevated (P0.0001) compared with that of healthy controls (173.4 vs. 91.9 fm/ml). Age or sex was not associated with sEGF-R levels. Regarding tumor burden, in contrary to the detected IL-6 levels, we found that median sEGF-R levels were significantly (P = 0.045) lower in patients with high tumor burden (163 fm/ml) than in those with low tumor burden (193.8 fm/ml). An inverse correlation between IL-6 levels and sEGF-R was observed (r =-0.33; P = 0.040). No relationship between sEGF-R and time to progression or overall survival was observed while circulating IL-6 was found as a predictive factor of survival. Our results showed that sEGF-R level was elevated in metastatic malignant melanoma patients but not related to time to progression or survival and demonstrated an inverse correlation between sEGF-R and IL-6 levels. These findings imply a better understanding of EGF-R and IL-6 cross-talk function in melanoma.