It has been reported that apoptosis is a predominant mode of death of tumor cells treated with cisplatin. It is unclear, however, whether cells of all tumor types, without exception, respond to cisplatin by apoptosis. In particular, the mode of death of glioma cells has not been investigated. In the present study human glioma U251 MG cells were treated in vitro with 1 or 10 mu g/ml cisplatin and their mode of death was analyzed by flow cytometry, DNA gel electrophoresis, examination of cell morphology following their staining with Giemsa and electron microscopy. The absence of a sub-G1 peak on the DNA content frequency histogram, the absence of DNA laddering on agarose gels, no nuclear fragmentation but distinct mitochondrial swelling were the features of U251 MG cells dying in the presence of cisplatin. Since these features are characteristic of necrosis rather than apoptosis the data indicate that the mode of cell death of some tumors treated with cisplatin may be necrosis.

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