beta-catenin in soft tissue sarcomas: Expression is related to proliferative activity in high-grade sarcomas

Besides its role in cell adhesion, beta-catenin exerts a function as an onc oprotein. The aim of this study was the characterization of its expression, possible mutation, and the assessment of beta-catenin as a prognostic indi cator for soft tissue sarcomas. A total of 115 soft tissue sarcomas were an alyzed using immunohistochemistry, immunogold-electron microscopy, and DNA analysis. Information from 56 patients was available for follow-up. A stati stically significant correlation was found between intracellular distributi on of beta-catenin and the proliferative activity (MIB-1 expression) in hig h-grade sarcomas (P =.0008). beta-catenin was identified with intracytoplas mic and nuclear accumulation, showing additional membranous staining in sar comas with epithelioid pattern. Ultrastructurally, a colocalization between beta-catenin and nuclear heterochromatin was demonstrated. In 22 analyzed tumors, only one (yet undescribed) mutation of the beta-catenin gene (C-A t ransversion) could be detected. Prognostic validity of the cellular express ion of beta-catenin, however, was not proven. Apart from its membranous fun ction as an effective molecule for cell-adhesion in sarcomas with epithelio id pattern, beta-catenin may act as an oncoprotein in sarcomas with intracy toplasmic and nuclear localization with binding to nuclear DNA. A previousl y discussed stimulation of cell proliferation caused by an increased beta-c atenin level can also be postulated for high-grade soft tissue sarcomas in correlation with the rate of proliferation. Mutations of the beta-catenin g ene are probably of lesser importance for the accumulation of beta-catenin in soft tissue sarcomas.