Histone deacetylase inhibitor Vorinostat (SAHA) suppresses micropthalmia transcription factor expression and induces cell death in nevocytes from large/giant congenital melanocytic nevi.

Large/giant congenital nevi (L/GCMN) are benign neoplasms of the melanocytic neural crest lineage covering extensive areas of skin presenting risk for melanoma. Surgical resection often leads to scarring and trauma. Histone deacetylase inhibitors (iHDACs) as topical therapeutic agents may prove beneficial as an alternative/adjunct to surgery in this disease. Here we describe the effect of in vitro treatment of iHDACs drugs on primary nevocytes isolated from L/GCMN patients. Micropthalmia transcription factor (MITF) expression in L/GCMN patients' lesions was detected by immunohistochemistry, in cultured nevocytes by immunofluorescence, immunoblot and quantitative polymerase chain reaction. Cellular senescence was detected by SA-ß galactosidase activity. Markers for melanocytic differentiation were evaluated by immunoblot analysis and extracted melanin content was estimated spectrophotometrically. Cell death was measured by lactate dehydrogenase (LDH) assay and necrosis confirmed by polymerase (PARP) cleavage and acridine orange staining of the nuclei. MITF was expressed ubiquitously in nevocytes and melanocytes in patients' lesions. In culture, iHDAC treatment suppressed MITF protein and mRNA expression resulting in a senescent-like phenotype with positive ß-galactosidase staining, progressing to necrotic cell death as evidenced by increased LDH activity, appearance of cleaved PARP and necrotic nuclei. This is the first report showing evidence of iHDACs-induced MITF suppression in congenital nevocytes in vitro leading to a morphologic change with positive ß-galactosidase staining, followed by necrotic cell death in nevocytes, indicating that iHDAC drugs could be valuable therapeutic agents for treatment of L/GCMN lesions.