Effects of hyperthermia on the nucleolar proteins in tumour cells

The effects of hyperthermia at 41 degrees C and 43 degrees C on the nucleolar protein B23 in Ehrlich ascites tumour (EAT), human glioblastoma U-87 MG and U-373 MG cell lines were studied. Cellular localization of protein B23 was detected by an immunofluorescence technique using monoclonal antibody against protein B23. Diminution of fluorescence in the nucleoli occurred when the cells were treated at high temperature. The decrease in fluorescence level depends on the treatment temperature and duration. Among the three cell lines studied, the U-373 MG glioblastoma was the least responsive to hyperthermia followed by the U-87 MG glioblastoma. The decrease in nucleolar fluorescence of the EAT cells treated at 41 degrees C and 43 degrees C correlated with their subsequent cell survival. Dispersion of the nucleolar argyrophilic granules occurred in EAT cells after heating at 43 degrees C for 1 h. The possible implication of such effect is discussed in relation to the heat-sensitive elements in the nucleolus.