Coexpression ofkeratin- andvimentin-type intermediate filaments inhumanmetastatic carcinoma cells

ABSTRACT Metastatic tumorcells of epithelial origin pres-entineffusionsfromhumanserouscavity fluids (ascitesorpleural fluid) wereexaminedfor their intermediate-sized filament types by using antibodies to keratin, vimentin, and desmin in the in-directimmunofluorescence technique. Solid epithelial tumors (both primary carcinomas andtheir metastases) contain keratin inter-mediate-sized filaments exclusively. However, when these cellsarepresentin ascitic orpleural fluid, they alsoexpress vimentin,whichoccursinafibrillarorganization. The possible effectsofthis additional, but temporary, cytoskeleton on metastatic growth oraggressiveness (or both) are discussed. Intermediate filaments (IFs) in eukaryotic cells constitute a considerable part ofthe cytoskeleton in addition to microfila- ments andmicrotubules (1). They can bevisualized in theelec-tron microscope as 7- to 11-nm fibrils (2) and are characterizedby specific biochemical and immunological properties (3-7).These properties also distinguish between different types ofIFs, whosenatureseemstocorrelatewiththeembryonicoriginofthe