The cytoskeleton in tumor cells.

During the past few years several laboratories investigated the occurrence of cytoskeletal components in epithelial and mesenchymal cells by electron microscopy and/or immunocytochemical methods in a number of tumor types growing in vitro or in the body. Since it is well established that antibodies to different intermediate-sized filament proteins can distinguish cells and tissues of epithelial, mesenchymal, muscle, astrocytic and neural origin special attention has been paid to the behaviour of these filaments in neoplastic cells recently. While the organisation of the cytoskeleton in tumor cells growing in vitro is very variable, regularities relevant for the diagnosis and the determination of the histogenetic origin of tumors have been observed in tumor cells growing in the body. In general, ultrastructural and immunological features of intermediate filaments are maintained during neoplastic transformation in the body. Thus immunofluorescence microscopy with antibodies to cytoskeletal proteins is a powerful tool for the classification and differential diagnosis of tumors, especially for the distinction between epithelial and mesenchymal tumors, including metastases. The concept that presence of an excess of contractile proteins such as actin is an important prerequisite for the metastatic spread of malignant cells has not been unequivocally supported by more recent results. However, an accumulation of various types of intermediate filaments (e.g. prekeratin, vimentin, acidic glial fibrillar protein) has been shown in different tumor types. The further elucidation of this alteration could contribute to a better understanding of the molecular mechanisms of neoplastic cell transformation.