Expression of melanoma inhibitory activity in melanoma and nonmelanoma tissue specimens

Melanoma inhibitory activity (MIA) is a small soluble protein secreted by m alignant melanoma cells and chondrocytes. Prior studies suggested that MIA expression was relatively tissue-specific, making it a potentially useful m arker for melanoma. The current investigations sought to more clearly defin e the range of tumor/tissue-types where MIA is expressed, compared with exp ression of 4 other potential melanoma marker genes (tyrosinase melanoma ant igen recognized by T cells [MART-1/MelanA], gp100, and melanoma growth-stim ulatory activity [MGSA/Gro alpha]). Expression of these genes was assayed b y reverse transcription polymerase chain reaction (RT-PCR) and immunohistoc hemistry in 23 melanoma tumor specimens and in 25 additional nonmelanoma or nonmalignant specimens. MIA, tyrosinase, and MGSA were expressed in most m elanoma specimens. Specificity was highest for MART-1, followed by MIA and tyrosinase. Increasing the number of cycles of amplification from 35 to 40 increased sensitivity but decreased specificity of most markers, though MIA was relatively robust. MIA mRNA was also detected in carcinomas of the col on, ovary, kidney, and head/neck, as well as in normal laryngeal epithelium . Although MIA discriminated melanoma from nommelanoma at least as well as tyrosinase, no single mRNA marker had accuracy greater than 71%, raising po tential concern about application of these particular mRNA markers to the m inimal disease setting. HUM PATHOL 31:1381-1388. Copyright (C) 2000 by W.B. Saunders Company.