Cisplatin treatment of NIH-3T3 cultures induces a form of autophagic death in polyploid cells

Abstract

The effects induced by different concentrations (50, 75, 100 μM) of the cytostatic drug cisplatin (cDDP) in NIH/3T3 cells were analyzed. Subconfluent cultures of this mouse fibroblast line, obtained after serum deprivation, showed the presence of aneuploid/polyploid cells with ploidy values ranging from 4c to 24c. DNA content cytofluorometry demonstrated that 50 and 75 μM cDDP induced a cytostatic effect; 100 μM concentration showed lower antiproliferative action. All treatments caused a partial cell detachment and apoptosis, the incidence of which appeared to be cDDP concentration-dependent. Ultrastructural and fluorescence microscopy integrated analyses of the still adherent cells demonstrated the presence of alternative degeneration patterns, especially in polyploid cells, with extensive modifications at both nuclear and cytoplasmic levels. There were events of micronucleation and phenomena of multilobulation and furrows of the nucleus that preceded the formation of heterogeneous fragments. These events were correlated, at cytoplasmic level, with actin reorganization and the appearance of autophagocytotic processes. In our cell model, the same pharmacological treatment was able to induce different cell death phenomena relating to cell dimension and ploidy. More actively proliferating cells (2c–4c DNA content) die throughout canonical apoptosis, while polyploid cells prevailingly degenerate by mechanisms partly referable to autophagic cell death.