| NUKLEONIKA 2008, 53(2):37-44
RELATIONSHIPS BETWEEN EGFR-INITIATED SIGNALLING, DNA DOUBLE-STRAND BREAK REJOINING AND SURVIVAL IN X-IRRADIATED HUMAN GLIOMA M059 CELLSIwona Grądzka, Iwona Buraczewska, Irena Szumiel Department of Radiobiology and Health Protection, Institute of Nuclear Chemistry and Technology, 16 Dorodna Str., 03-195 Warsaw, Poland The aim of this study was to investigate the effect of signalling inhibition on survival and double-strand break (DSB) rejoining in cells differing in sensitivity to inhibitors, X-rays and bleomycin. Human glioma M059 cells, K (relatively radioresistant) and J (radiosensitive, defective in DSB rejoining for lack of DNA-dependent protein kinase catalytic subunit, DNA-PKcs) were pretreated with signalling inhibitors: tyrphostin AG 1478, specific for epidermal- growth-factor-receptor (EGFR) kinase or PD 98059, specific for kinase MEK 1/2 (mitogen-activated, extracellular signal-activated kinases 1 and 2). Subsequently, the cells were X-irradiated or treated with bleomycin. Cell survival was determined by clonogenicity test. DSB rejoining was monitored with the use of pulsed-field gel electrophoresis (PFGE). We found that in X-irradiated M059 K cells EGFR kinase activity was necessary for efficient DSB rejoining and the kinase inhibitor, tyrphostin AG 1478, acted as radiosensitizer in the dose range that reduced cell survival to 0.7–0.8. Inhibition of EGFR kinase, however, did not decrease survival or affect DSB rejoining in DNA-PKcs-deficient M059 J cells. These results indicated that the decrease in cell survival was due to a disturbed DSB rejoining by the DNA-PK dependent system. In contrast, inhibition of MEK 1/2 kinase on EGFR downstream signalling pathway by PD 98059 did not affect DSB rejoining in either cell line and exerted a radioprotective effect. Close X |