THE ANALYSIS OF TYROSINASE-SPECIFIC MESSENGER-RNA IN BLOOD-SAMPLES OFMELANOMA PATIENTS BY RT-PCR IS NOT A USEFUL TEST FOR METASTATIC TUMORPROGRESSION

Reverse transcription (RT) of the tyrosinase mRNA and specific cDNA am plification by nested polymerase chain reactin (PCR) have been reporte d to facilitate the early detection of circulating tumor cells in mela noma patients, The significance and practical value of this procedure for the diagnosis of tumor dissemination in melanoma patients are uncl ear. In the current study we analyzed peripheral blood samples of 65 m elanoma patients of different clinical stages for the presence of tyro sinase mRNA by RT-PCR using nested oligonucleotide primers specific fo r tyrosinase cDNA. Furthermore, blood samples were evaluated for tumor cell growth by cell culture assays in. vitro. No tyrosinase mRNA was detectable in blood samples of 26 patients with primary melanoma and 1 6 patients with regional lymph node metastases. In five of 13 patients with visceral metastases we found at least one blood sample positive for tyrosinase mRNA during a 2-to 4-mo interval, Analyses of different blood samples of patients with visceral metastases taken in a 2-h int erval, furthermore, indicate that tumor cells only transiently persist in the peripheral blood. We obtained in vitro proliferating melanoma cells from two blood samples derived front different patients with vis ceral melanoma metastases. This demonstrates that viable melanoma cell s indeed circulate in the peripheral blood with retained proliferative capacity in vitro. The analysis of blood samples by RT-PCR for tyrosi nase mRNA, however, is not suitable for the early detection of tumor p rogression in melanoma patients.