BCL-2 IS PREFERENTIALLY EXPRESSED IN TUMORS OF MUSCLE ORIGIN BUT IS NOT RELATED TO P53 EXPRESSION

bcl-2 is a proto-oncogene which inhibits apoptosis. In contrast, p53 t umour suppressor gene is known to induce apoptosis. In this study we a nalysed immunohistochemically 63 mesenchymal tumours for the expressio n of bcl-2 and p53 proteins with a special emphasis on muscle-derived tumours. bcl-2 was expressed in all seven rhabdomyosarcomas and in fiv e out of seven leiomyosarcomas. In benign muscle tumours, bcl-2 expres sion was found in all four epithelioid leiomyomas and in six out of 14 leiomyomas. In non-neoplastic muscle cells, occasional weak bcl-2 pos itivity was found in muscle cells of vascular walls and myometrium. In mesenchymal tumours of other lineages, bcl-2 positivity was only foun d in four out of 12 malignant fibrous histiocytomas and in one out of three liposarcomas. p53 positivity was found in 14 tumours, 13 of whic h were sarcomas. No association was found between p53 and bcl-2 positi vity. Our results suggest that bcl-2 expression is activated significa ntly more often in muscle derived tumours than in mesenchymal tumours of other lineages. Our results also suggest that p53 status does not d irectly affect the expression of bcl-2 in sarcomas.