The effect of the Fanconi anemia polypeptide, FAC, upon p53 induction and G2 checkpoint regulation.
Fanconi anemia (FA) is an autosomal recessive disease marked by developmental defects, bone marrow failure, and cancer susceptibility. FA cells are hypersensitive to DNA cross-linking and alkylating agents and accumulate in the G2 phase of the cell cycle in response to these agents. FA cells also display genomic instability, suggesting a possible defect in the p53 pathway. To test the effect of heterologous expression of FAC cDNA on drug-induced cytotoxicity, G2 accumulation, and p53 induction in FA cells, we compared two isogenic FA cell lines: HSC536N (mock), a FA type C cell line sensitive to mitomycin C (MMC), and the same cell line transfected (corrected) with wild-type FAC cDNA (HSC536N [+FAC]). HSC536N (+FAC) cells showed a 30-fold increase in resistance to MMC concentration. Similarly, increases in resistance were observed following exposure to cisplatin, carboplatin, and cyclophosphamide. In addition, HSC536N (+FAC) cells showed a twofold lower G2 accumulation following MMC treatment. To analyze the possible interaction of FAC with the p53 pathway, we analyzed p53 induction in mock and corrected cell lines following exposure to MMC. HSC536N (mock) cells induced p53 at lower MMC concentrations than HSC536N (corrected). Caffeine, a known G2 checkpoint inhibitor, not only inhibited G2 accumulation seen in both cell lines but also caused the resistant HSC536N (+FAC) to become as sensitive to MMC as HSC536N (mock) cell line. We conclude that the FAC protein has a specific cytoprotective effect and may function as a cell cycle regulator of the G2 phase of the cell cycle.
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Division of Pediatric Oncology, Dana-Farber Cancer Institute, Boston MA, USA.
D'Andrea
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D000970:Antineoplastic Agents / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D018797:Cell Cycle Proteins; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004249:DNA Damage; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins; D004351:Drug Resistance / Q000235:genetics; D005199:Fanconi Anemia / Q000235:genetics*; D051856:Fanconi Anemia Complementation Group Proteins; D016195:G2 Phase / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics*; D016158:Genes, p53; D006801:Humans; D009153:Mutagens / Q000494:pharmacology; D009687:Nuclear Proteins; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis
D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051856:Fanconi Anemia Complementation Group Proteins; D009153:Mutagens; D009687:Nuclear Proteins; D011506:Proteins; D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D002110:Caffeine