APC and beta-catenin in alveolar soft part sarcoma (ASPS) - Immunohistochemical and molecular genetic analysis

Apart from its role in cell-adhesion, beta-catenin is regarded as an oncopr otein, the cytoplasmic level of which is regulated by APC as a turner suppr essor protein. Changes of chromosome 5q, the region that includes the APC-g ene, are known to be important in the pathogenesis of fibromatosis; however , little is known about the significance of APC and beta-catenin ill other mesenchymal tumors. Therefore, we used immunohistochemistry and DNA-analysi s to investigate four cases of alveolar soft-part sarcoma (ASPS) as a mesen chymal tumor with a distinct histologic appearance. In three cases of ASPS the APC-gene product was found to have strong nuclea r expression and only faint cytoplasmic staining, beta-catenin showed a par tly membranous, partly strong intracytoplasmic expression. No gene mutation s for APC and beta-catenin were detected in any of the four cases. These investigations suggest that, apart from their function in carcinogene sis and fibromatoses, APC and beta-catenin play a role in the pathogenesis of soft tissue tumors such as ASPS, The significance of a striking nuclear accumulation of non-mutated, virtually functionally active APC-tumor suppre ssor protein has not yet been investigated. A nuclear function of APC in AS PS in down-regulating nuclear transcription processes linked to overexpress ion of beta-catenin, as is known in colorectal carcinogenesis, may be hypot hesized.