The aim of this investigation was to analyze whether or not ionizing radiation can induce the expression of resistance- and oncoproteins in murine sarcoma 180 cells and several human carcinoma cell lines. For assessment of the proteins the streptavidin-biotin peroxidase-complex method was performed using specific antibodies. Expression of glutathione S-transferase-pi and thymidylate-synthase was increased after a single dose of irradiation which was accompanied by a lower sensitivity against cisplatin and 5-fluorouracil. No differences in protein expression could be detected for P-glycoprotein 170 and topoisomerase II. Differences in the expression of the oncoproteins c-Fos and c-ErbB1 were also found after irradiation. In contrast, a decreased expression of topoisomerase II was found after fractionated irradiation. This was confirmed by mRNA analysis.

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