[Thermosensitivity of glioma cells with special reference to changes in cytoskeletons]

The relationship between the thermosensitivity of cultured brain tumor cells and cytoskeleton was studied. C6 rat glioma cell line (C6 cells) and U-373-MG human glioblastoma cell line (MG cells) were used in monolayer culture. Survival rates at various temperatures were calculated by colony forming assay 10 days after heat treatment. Actin filaments, the main components of microfilaments, were observed by the 7-chloro-4-nitrobenzo-2-oxadiazole phallacidin staining and indirect immunofluorescence staining methods. Alpha-tubulins, the main components of microtubules, were also stained with an indirect immunofluorescence staining method. The morphological changes were investigated by scanning electron microscopy (SEM). Both the C6 cells and the MG cells showed moderate thermosensitivity on the survival curves. Actin filaments were revealed at stress fibers and the ruffles of the leading edge on both cell lines. Stress fibers were well developed in MG cells but were only minor in C6 cells. After heat treatment ruffles and stress fibers were disrupted. However, alpha-tubulins were not affected by heat treatment. SEM showed Swiss-cheese like change of cell surfaces due to many pores with disruption of ruffles and stress fibers after heat treatment. These results suggest that the cytoskeleton, especially microfilaments, may be damaged by hyperthermia.