A predictive strategy for micrometastic disease: Detection of tumor mRNA transcripts in lymph nodes, blood and plasma of malignant melanoma patients

G. Gómeza, N. Álvareza, M E. Garcíaa, L. Cabañasb, M V. Toledo MDa, J. Coll PhDa, A. Moyano MDa and E. Caso MD,PhDa

aHospital Ramón y Cajal. Madrid. Spain, bLaboratorio de Oncología Molecular Aplicada. Servicio de Oncología Médica y Servicio de Cirugía General.

AIM. Assessment of tyrosinase mRNA by RT-PCR within a panel of multiple transcripts of melanoma-associated genes is determinant for detection of scattered tumor cells in lymph nodes of malignant melanoma patients (1). Analysis of tyrosinase mRNA transcripts in sentinel lymph nodes (SLNs), whole blood and plasma for detection of occult melanoma cells may be useful as predictive strategy for micrometastic disease in melanoma patients. On the other hand, it is unclear whether mRNA can exist in plasma and serum with sufficient integrity to allow amplification (2,3). METHODS. Blood and SLNs samples, from 24 malignant melanoma patients, were studied. Plasma was passed through a 0.22 mm sterile filter to exclude cells contaminating. Total RNA was amplified by a RT-nested PCR method previously established (1,4). Blood from 9 healthy volunteers was included as control. RESULTS. Seven out of 24 patients (28%) were tyrosinase positive both in SLN and whole blood. Plasma from 13 patients was positive in 23% of cases. Tyrosinase profile (blood/plasma) was: +/+ in 15%, +/- in 23%, -/+ in 8% and -/- in 54% of patients. Tyrosinase mRNA circulating in peripheral blood was achieved in 36% of melanoma patients. Our assays, reveal that extracellular mRNA exists in plasma with sufficient integrity for amplification of tumor transcripts. CONCLUSIONS. Tumor mRNA circulating in peripheral blood is marker of occult haematogenous dissemination. This strategy is a noninvassive approach for routine clinical management of patients and may be useful for monitoring anticancer therapies. The finding of tumor mRNA in plasma may be suggestive of tumoral cell death and further studies are ongoing to explain the nature of extracellular circulating mRNA. REFERENCES: 1. Caso, E. et al. ASCO Proceedings 2001. Abst. 2896. 2. Kopresky, M. S. et al. Clinical Cancer Res. 1999; 5, 1961-65. 3. Komeda, T. et al. Cancer (Phila.) 1995; 75: 2214-19 4. Smith, B. et al. The Lancet 1991;338: 1227-29. .

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Carcinogenesis.