The use of
tyrosinase-based polymerase chain reaction (PCR) tests for the detection of circulating tumour cells in the blood of
melanoma patients has led to highly controversial results. We here report on the analysis of 120 blood samples from 76 stage I to IV
melanoma patients using a new MART-1/
Melan-A PCR system in conjunction with the
tyrosinase-specific assay reported in the literature. While there were no positive results in localized disease (stages I and II), identification of specific PCR products in stage III
melanoma patients was restricted to the MART-1/
Melan-A tests, with positive results in 11% (two out of 19) of the blood specimens analysed. Stage IV
melanoma patients presented with the highest incidence of detectable
mRNA levels, with positive results for
tyrosinase in 38% (12 out of 32) and for MART-1/
Melan-A in 22% (seven out of 32). By delineating 64 follow-up specimens covering sampling periods of up to 33 weeks, stable
mRNA expression profiles were identified in nearly 95%. Four patients, however, showed PCR changes towards positive MART-1/
Melan-A expression that were linked to metastatic
melanoma progression. Taken together, PCR tests for
tyrosinase and MART-1/
Melan-A seem to lack sufficient detection frequencies for the routine monitoring of
melanoma disease. Regarding the link between MART-1/
Melan-A seroconversion and the development of metastatic disease, further studies are needed to clarify the clinical value of this observation.