Purpose: The value of tyrosinase messenger RNA (mRNA) detection in the peripheral blood by reverse-transcription polymerase chain reaction (RT-PCR) as a melanoma marker remains controversial. The purpose of this study was to compare the sensitivities of two different blood processing techniques for tyrosinase mRNA detection and evaluate its potential clinical value.
Methods: A total of 50 patients with progressive stage IV melanoma was studied. Two blood processing methods were used: RNA extraction from the whole blood and RNA extraction from density gradient-isolated peripheral-blood mononuclear cells (PBMC). The RNA samples were tested with a sensitive nested-primer RT-PCR assay. RT-PCR results were also correlated with serum lactate dehydrogenase (LDH), treatment status, and presence of visceral versus nonvisceral metastases.
Results: Thirteen (26%) of the density gradient and five (10%) of the whole blood processed samples were PCR positive (P = .011). Serum LDH levels were found to be significantly higher in PCR-positive PBMC-processed patients (P = .015). There was no significant difference in the detection rates between visceral versus nonvisceral metastases or between prior treatment versus no prior treatment.
Conclusion: Using a density gradient method to process the blood samples resulted in a higher detection rate of tyrosinase mRNA than extracting the RNA from the whole blood. However, the relatively low sensitivity in patients with disseminated and progressive disease compared with other reports suggests that tyrosinase mRNA may be of limited value in the management of malignant melanoma.