The expression of the growth-related 25kDa protein (p25) of Ehrlich ascites tumor cells is increased by hyperthermic treatment (heat shock).
The abundance of a 25 kDa protein (p25) and at least two phosphorylated isoforms is inversely correlated with the rate of in vivo growth of the Ehrlich ascites tumor (EAT). On the basis of cDNA sequence data, p25 shows an about 80% amino acid sequence homology to the mammalian heat shock protein hsp27 (Gaestel et al., Europ. J. Biochem. 179, 209, 1989). In this paper, the following data are presented and discussed: 1. The expression of p25 is increased by in vitro incubation of cells at elevated temperatures (41.5 degrees C-43.5 degrees C). 2. A two-step hyperthermic treatment with a recovery period at 37 degrees C results in a more elevated p25 expression than a one-step hyperthermia. Moreover, the two-step hyperthermic treatment results in thermotolerance in terms of protein biosynthesis and cell vitality. 3. Also the appearance of p25 isoforms depends on the temperature regimes. While after a one-step hyperthermia the phosphorylated isoforms p25/2 and p25/3 predominate, the unphosphorylated isoform p25/1 is more strongly expressed after a two-step hyperthermic treatment, which results also in a more increased total p25 synthesis than a one-step treatment. 4. The synthesis of p25 and its induction by hyperthermic treatment in EAT cells depends on the stage of tumor growth from which the cells were harvested. Both, the endogenous synthesis and the induction by elevated temperature are higher in cells from the exponentially growing tumor than in cells from the stationary tumor. The results are discussed with respect to correlations between regulation of tumor growth and the abundance of p25, its synthesis and induction during tumor growth.
Department of Cell Physiology, Academy of Sciences of the GDR, Berlin-Buch.
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Oesterreich
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Benndorf
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Bielka
D000818:Animals; D001151:Arsenic / Q000494:pharmacology; D018053:Arsenites; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006360:Heat-Shock Proteins; D006358:Hot Temperature; D051379:Mice; D008813:Mice, Inbred ICR; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational
D018053:Arsenites; D006360:Heat-Shock Proteins; C486113:Hsbp1 protein, mouse; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; C015001:arsenite; D001151:Arsenic