Molecular and prognostic classification of advanced melanoma: a multi-marker microcontamination assay of peripheral blood stem cells

The presence or absence of melanoma cells in human peripheral blood has rec ently been shown to be associated with disease prognosis, including overall survival. The detection of tyrosinase mRNA-positive circulating melanoma c ells by reverse transcription-polymerase chain reaction (RT-PCR) has been l imited to disseminated tumours expressing measurable amounts of this melano cyte-specific enzyme. To biologically classify both melanotic and amelanoti c melanomas and to evaluate the clinical and prognostic relevance of tumour cell microcontamination, we examined autologous peripheral blood stem cell (PBSC) harvests from patients with advanced malignant melanoma prior to do se-escalated chemotherapy. To assay heterogeneous melanoma cell antigen exp ression, we developed a highly sensitive RT-PCR using four melanoma- and on e tumour-associated antigen as molecular markers. Expression of the melanoc yte-associated transcripts of tyrosinase, MART1/Melan-A, tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2) as well as the tumour-specific transcript of MAGE-3 was analysed by RT-PCR in PBSC harvest s from 31 patients. Seven of the 31 PBSC harvests tested positive for one o r more molecular markers: two patients for tyrosinase only, and one patient for MAGE-3 only, one patient for tyrosinase and MAGE-3, one for tyrosinase and MART1/Melan-A, and two patients for tyrosinase, MART1/Melan-A, TRP-2 a nd MAGE-3. mRNA-positive patients exhibited a significantly impaired overal l survival (P = 0.0032), with a median survival of 3 months as opposed to 1 0 months in PBSC mRNA-negative patients. In conclusion, the use of this mul tiple-marker microcontamination assay allowed for molecular and prognostic classification of advanced malignant melanoma. (C) 2000 Lippincott Williams & Wilkins.