Identification of melanoma-specific serological markers using proteomic analyses

The discovery of novel melanoma markers for not only early detection but also monitoring disease status is promising to improve the clinical outcome of patients. In the present study, we performed proteomic comparative analysis of plasma proteins between healthy volunteers and melanoma patients using NanoLC and MALDI-TOF-MS. As a result, we were successful in identifying nine proteins that were specifically expressed in melanoma plasma compared with healthy plasma, most of which had not previously been identified as plasma markers of melanoma. The mRNA expression levels of four proteins [pro-platelet basic protein precursor (PPBP), serum amyloid A2 (SAA2), complement factor H-related protein 1 precursor (FHR1), interalpha-trypsin inhibitor heavy chain H4 precursor (IAIH4)] were prominently up-regulated in several melanoma cell lines compared with melanocytes. Moreover, two proteins (PPBP, SAA) were shown to be expressed in tumor specimens from melanoma patients. In the survival time analysis regarding melanoma patients, the semi-quantified plasma PPBP levels were statistically negatively correlated with the survival time. Most interestingly, the significant survival benefit was seen in low PBPP level group (< index 20) versus high level (>= index 20) group. The results suggest that PPBP might be a novel promising serological marker and a prognostic factor specific to melanomas.