| 7915598 |
Venetianer A, Pirity M, Hever-Szabo A: The function of heat-shock proteins in stress tolerance. Cell Biol Int. 1994 Jun;18(6):605-15.
We earlier demonstrated that hsp68 is deficiently induced upon stress in the glucocorticoid-resistant, dedifferentiated Reuber rat hepatoma clone 2 cells, but is strongly activated in the differentiated, glucocorticoid-sensitive Faza 967 cells from which clone 2 was derived. We used the two cell types to address the questions whether hsp68 is specifically involved in the development of thermotolerance and/or thermoresistance or drug resistance. Our experiments show that clone 2 cells were not protected from the killing effect of heat by pre-treatment with sodium arsenite, whereas Faza 967 cells were. These results strongly suggest a role of hsp68 in the development of thermotolerance in hepatoma cells. Stable heat-resistant variants of clone 2 cells were also isolated, where an increased basal expression of several hsps was observed together with the (at least partial) restoration of the heat-inducibility of hsp68. These results suggest that several hsps are needed to protect the critical biological processes at high temperature. The heat-resistant hepatoma cells also became resistant to several anticancer drugs. The multidrug resistance of the hepatoma variants correlates with the overexpression of the plasma membrane P-glycoprotein. Our results showing that severely stressed hepatoma cells overexpressed the mdr gene (s) raise the possibility that the P-gp may participate in protection against environmental stress such as heat. |
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