Usefulness of neuron-specific enolase as a serum marker of metastatic melanoma.

Treatment strategies for advanced melanoma are dramatically changing, due to immune-checkpoint inhibitors and BRAF/MEK inhibitors. Nevertheless, reliable serum markers for evaluation of treatment responses and the outcome are still limited. Some previous reports suggested that serum neuron-specific enolase (sNSE) may be a useful marker for melanoma; however, its usefulness is controversial. Moreover, NSE has not been examined in vitro by using melanoma cell lines. We retrospectively evaluated sNSE and serum lactate dehydrogenase (sLDH) levels at the initial diagnosis and during therapy in 33 melanoma patients of various stages. We analyzed the NSE concentrations in cell lysates and supernatants from melanoma cell lines by enzyme-linked immunosorbent assay. The median sNSE was significantly higher in stage IV patients compared with stages I/II and III (16.3, 12.7 and 12.1 ng/mL, respectively). sNSE was elevated in 20% (2/10) of stage III and 61.1% (11/18) of stage IV patients but not in stages I/II. sNSE and sLDH tended to correspond to the total tumor volume (P = 0.48 and 0.58; 95% confidence intervals, 0.005-0172 and 0.776-0.836, respectively). The coincidence rate of sNSE and sLDH in stage IV at the initial diagnosis was 11 of 18 (61.1%). Of the remaining patients, elevated sNSE but not sLDH was observed in five patients (27.8%) and elevated sLDH but not sNSE was observed in two (11.1%). Four of the five patients showing elevated sNSE and normal sLDH were of the mucosal type. NSE was detected in both supernatant and cell lysate of all four melanoma cell lines (0.30-237.32 ng/mL and 137-483.04 ng/mg, respectively). Two cell lines with a high supernatant NSE level contained many dead cells in the supernatant. The combination of sNSE and sLDH could contribute to the early detection of distant metastasis and disease condition evaluations for advanced melanoma patients.