Changes in the cytoskeleton pattern of tumor cells by cisplatin in vitro.

The influence of the antitumor drug cis-diamminedichloroplatinum(II) ('cisplatin') upon the structural pattern of the main cytoskeletal components, i.e. microtubules, intermediate filaments and microfilaments, was investigated in squamous carcinoma cells derived from the mouse stomach (G 22) or the human lung (L 266) and growing in vitro as monolayer cultures. The studies were performed by the indirect immunofluorescence technique using monoclonal antibodies against alpha-tubulin, type 19 cytokeratin and actin at the end of a 90-min exposure to 2.5 x 10(-6), 5 x 10(-6) or 10(-5) mol cisplatin/l and a subsequent 24-h recovery period. Under the influence of cisplatin, the cytoskeletal tubules and filaments, which were distributed in untreated cells as a finely organized network spreading through the whole cytoplasm like a spider's web, collapsed and aggregated to dense and circularly arranged bands of bright immunofluorescence around the nucleus or to cap-like structures apposing the nucleus. These phenomena developed in clear dependence upon the dose of cisplatin applied and were observable in a modified manner and to a different degree with the three structural elements of the cytoskeleton. During the subsequent 24-h interval, during which the cells were allowed to recover in drug-free growth medium, the before-mentioned collapse of the cytoskeletal network was only partially reversible following previous treatment with the medium (5 x 10(-6) mol/l) and the high (10(-5) mol/l) dose of cisplatin and restored totally to the normal structural pattern of untreated control cells when the low dose of 2.5 x 10(-6) mol cisplatin/l had been administered before. These results give evidence that the DNA cannot be the only cellular target for the antitumor drug cisplatin, but that it also effects other intracellular lesions which cause structural alterations of cellular organelles independently of the primary molecular attack at nuclear DNA strands. Probably, these additional interactions fortify the antiproliferative effect and contribute to the achievement of important biological and cytological effects of cisplatin such as growth inhibition or giant cell formation.