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The risks of exposure to low dose ionizing radiation (below 100 mSv) are estimated by extrapolating from data obtained after exposure to high dose radiation, using a linear no-threshold model (LNT model). However, the validity of using this dose-response model is controversial because evidence accumulated over the past decade has indicated that living(More)
  • A Takahashi
  • 2001
PURPOSE This study was undertaken to clarify the effects of acute or chronic pre-irradiation on the induction of p53-dependent apoptosis by X-rays or heat shock. MATERIALS AND METHODS Having an identical genotype except for p53-status, the human cultured squamous cell carcinoma cells (SAS) were transfected with a mutant p53 gene (SAS/mp53) or neo alone(More)
The role of the Fanconi anemia (FA) repair pathway for DNA damage induced by formaldehyde was examined in the work described here. The following cell types were used: mouse embryonic fibroblast cell lines FANCA(-/-), FANCC(-/-), FANCA(-/-)C(-/-), FANCD2(-/-) and their parental cells, the Chinese hamster cell lines FANCD1 mutant (mt), FANCGmt, their(More)
The cytotoxic effects of alkylating agents are strongly attenuated by cellular DNA repair processes, necessitating a clear understanding of the repair mechanisms. Simple methylating agents form adducts at N- and O-atoms. N-methylations are removed by base excision repair, AlkB homologues, or nucleotide excision repair (NER). O(6)-methylguanine (MeG), which(More)
PURPOSE We analyzed the death pattern of human lung cancer cells harboring different p53 statuses after irradiation with different levels of linear energy transfer (LET). METHODS AND MATERIALS We used three kinds of human lung cancer cell lines with identical genotypes, except for the p53 gene. These cells were exposed to X-rays or accelerated carbon-ion(More)
Viable organisms recognize and respond to environmental changes or stresses. When these environmental changes and their responses by organisms are extreme, they can limit viability. However, organisms can adapt to these different stresses by utilizing different possible responses via signal transduction pathways when the stress is not lethal. In particular,(More)
Temozolomide (TMZ) is a methylating agent used in chemotherapy against glioblastoma. This work was designed to clarify details in repair pathways acting to remove DNA double-strand breaks (DSBs) induced by TMZ. Cultured mouse embryonic fibroblasts were used which were deficient in DSB repair genes such as homologous recombination repair-related genes X-ray(More)
Photoreactivation (PR) is an efficient survival mechanism that helps protect cells against the harmful effects of solar-ultraviolet (UV) radiation. The PR mechanism involves photolyase, just one enzyme, and can repair DNA damage, such as cyclobutane-pyrimidine dimers (CPD) induced by near-UV/blue light, a component of sunlight. Although the balance of(More)
NBS1 is essential for the repair of radiation-induced DNA double-strand breaks (DSBs) in yeast and higher vertebrate cells. In this study, we examined whether suppressed NBS1 expression by small interference RNA (siRNA) could enhance radiation sensitivity in cancer cells with different TP53 status. We used human non-small cell lung cancer cells differing in(More)
The X-chromosome-linked inhibitor of the apoptosis protein (XIAP) is known to be an inhibitory factor for caspase-3. The aim of our study was to see whether radiation-induced apoptosis is enhanced by RNA interference targeting the XIAP through an elevation of caspase-3 activity, and whether the effect of XIAP depression depends on the p53 status of cancer(More)