title: The relative contribution of CHK1 and CHK2 to Adriamycin-induced checkpoint.
abstract: Topoisomerase II poisons like Adriamycin (ADR, doxorubicin) are clinically important chemotherapeutic agents. Adriamycin-induced DNA damage checkpoint activates ATM and ATR, which could in turn inhibit the cell cycle engine through either CHK1 or CHK2. In this study, we characterized whether CHK1 or CHK2 is required for Adriamycin-induced checkpoint. We found that both CHK1 and CHK2 were phosphorylated after Adriamycin treatment. Several lines of evidence from dominant-negative mutants, short hairpin RNA (shRNA), and knockout cells indicated that CHK1, but not CHK2, is critical for Adriamycin-induced cell cycle arrest. Disruption of CHK1 function bypassed the checkpoint, as manifested by the increase in CDC25A, activation of CDC2, increase in histone H3 phosphorylation, and reduction in cell survival after Adriamycin treatment. In contrast, CHK2 is dispensable for Adriamycin-induced responses. Finally, we found that CHK1 was upregulated in primary hepatocellular carcinoma (HCC), albeit as an inactive form. The presence of a stockpile of dormant CHK1 in cancer cells may have important implications for treatments like topoisomerase II poisons. Collectively, the available data underscore the pivotal role of CHK1 in checkpoint responses to a variety of stresses.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.
authors.forename: Chui Chui
authors.initials: CC
authors.lastname: Ho
authors.forename: Wai Yi
authors.initials: WY
authors.lastname: Siu
authors.forename: Jeremy P H
authors.initials: JP
authors.lastname: Chow
authors.forename: Anita
authors.initials: A
authors.lastname: Lau
authors.forename: Talha
authors.initials: T
authors.lastname: Arooz
authors.forename: Hoi Yee
authors.initials: HY
authors.lastname: Tong
authors.forename: Irene O L
authors.initials: IO
authors.lastname: Ng
authors.forename: Randy Y C
authors.initials: RY
authors.lastname: Poon
mesh_terms: D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology*; D018816:Genes, cdc; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000378:metabolism; D011494:Protein Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D012313:RNA / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D012313:RNA; D004317:Doxorubicin; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases