Detection of tyrosinase mRNA by RT-PCR in the peripheral blood of patientswith advanced metastatic melanoma

Detection of melanoma cells in the peripheral blood has been facilitated by the reverse transcriptase-polymerase chain reaction (RT-PCR), but their pr esence is of uncertain importance in the evolution of the disease. We studi ed the detection of melanoma cells using RT-PCR in the peripheral blood of 21 patients, four with regional lymph node metastases (American Joint Commi ttee on Cancer [AJCC] stage III) and 17 with disseminated disease (AJCC sta ge IV), RNA was extracted from 10 ml of heparinized blood following density gradient centrifugation and converted into cDNA for PCR analysis. Assay se nsitivity of 10 cells in 10(7) mononuclear cells and granulocytes obtained from 10 ml of peripheral blood was achieved using the G361 and C32 melanoma cell lines. Tyrosinase mRNA was not detected in control samples from healt hy volunteers or patients with non-malignant disease. Six patients (one sta ge III, five stage IV) tested positive for tyrosinase mRNA (28.6%); with on e exception, all patients were receiving chemotherapy at the time of sampli ng. Of the six positive results, three were from patients who initially tes ted negative but were subsequently positive after a 3-4 week interval. The low detection rates of melanoma cells in the peripheral blood of patients w ith widely disseminated disease is consistent with recent reports and corre lates poorly with the clinical stage of melanoma. This may be partly explai ned by the clinically observed intermittent and random evolution of melanom a metastases. (C) 1999 Lippincott Williams & Wilkins.