TYROSINASE IMMUNOREACTIVITY IN FORMALIN-FIXED, PARAFFIN-EMBEDDED PRIMARY AND METASTATIC MELANOMA - FREQUENCY AND DISTRIBUTION

Monoclonal antibody T311 specifically detects tyrosinase protein expre ssion. Tyrosinase-derived peptides are recognized by CD8+ T-cells and applied in immunotherapy. We examined formalin-fixed paraffin-embedded tissue of 50 melanoma (primary n=31, metastatic n=19) and 41 control cases (junctional, dermal, compound, Spitz, Reed, balloon-cell nevi) b y immunochemistry using the alkaline phosphatase-anti-alkaline phospha tase method after antigen retrieval. Staining with mAb T311 showed a s ensitivity of 94% for melanoma with a very high specificity for melano cytic cells. Immunopositivity (94% of melanomas overall) correlated in versely with clinical stage: clinical stage I and stage II showed 100% , stage III and stage IV 86% immunoreactivity each. Staining changed f rom an exclusively homogeneous pattern in early stages to a more heter ogeneous pattern in later stages. Melanocytic control tissue like nevi of different subtypes all showed weak to moderate, homogeneous immuno reactivity with polarity towards the epidermis. RT-PCR ELISA analysis of short-term melanoma cell cultures displaced mRNA expression in only half of the originally immunopositive tumors only suggesting rapid mR NA expression loss in culture, mAb T311 allows detection of melanoma-a ssociated tyrosinase protein expression and thus profiling of melanoma s using routine archival tissue suited for immunotherapy approaches in volving tyrosinase derived epitopes. (C) Munksgaard 1998.