Inhibition of the Jun kinase pathway blocks DNA repair, enhances p53-mediated apoptosis and promotes gene amplification.
We have previously shown, by expression of a nonphosphorylatable dominant inhibitor mutant of c-Jun [cJun(S63A,S73A)], that activation of the NH2-terminal Jun kinase/stress-activated protein kinase by genotoxic damage is required for DNA repair. Here, we examine the consequences of inhibition of DNA repair on p53-induced apoptosis in T98G cells, which are devoid of endogenous wild-type p53. Relative to parental or wild-type c-Jun-expressing control cells, mutant Jun-expressing T98G clones show similar growth rates and plating efficiencies. However, these cells are unable to repair DNA (PCR-stop assays) and exhibit up to an 80-fold increased methotrexate-induced colony formation due to amplification of the dihydrofolate reductase gene. Moreover, the mutant c-Jun clones exhibit increased apoptosis and elevated bax:bcl2 ratios on expression of wild-type p53. These results indicate that inhibition of DNA repair leads to accumulation of DNA damage in tumor cells with unstable genomes and this, in turn, enhances p53mediated apoptosis.
Gjerset
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RA
Sidney Kimmel Cancer Center, San Diego, California 92121, USA. rgjerset@skcc.org
Lebedeva
S
S
Haghighi
A
A
Turla
S T
ST
Mercola
D
D
D017209:Apoptosis; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002945:Cisplatin / Q000378:metabolism; D002999:Clone Cells; D018736:DNA Adducts / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D006801:Humans; D008727:Methotrexate / Q000494:pharmacology; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D018736:DNA Adducts; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016755:Proto-Oncogene Proteins c-jun; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D013762:Tetrahydrofolate Dehydrogenase; D002945:Cisplatin; D008727:Methotrexate