title: Dissociation of gemcitabine chemosensitization by CHK1 inhibition from cell cycle checkpoint abrogation and aberrant mitotic entry.
abstract: In order to determine the relative contribution of checkpoint abrogation and subsequent aberrant mitotic entry to gemcitabine chemosensitization by CHK1 inhibition, we established a model utilizing the CDK inhibitors roscovitine or purvalanol A to re-establish cell cycle arrest and prevent aberrant mitotic entry in pancreatic cancer cells treated with gemcitabine and the CHK inhibitor AZD7762. In this study, we report that the extent of aberrant mitotic entry, as determined by flow cytometry for the mitotic marker phospho-Histone H3 (Ser10), did not reflect the relative sensitivities of pancreatic cancer cell lines to gemcitabine chemosensitization by AZD7762. In addition, re-establishing gemcitabine-induced cell cycle arrest either pharmacologically, with roscovitine or purvalanol A, or genetically, with cyclin B1 siRNA, did not inhibit chemosensitization uniformly across the cell lines. Furthermore, we found that AZD7762 augmented high-intensity γH2AX signaling in gemcitabine-treated cells, suggesting the presence of replication stress when CHK1 is inhibited. Finally, the ability of roscovitine to prevent chemosensitization correlated with its ability to inhibit AZD7762-induced high-intensity γH2AX, but not aberrant pHH3, suggesting that the effects of AZD7762 on DNA replication or repair rather than aberrant mitotic entry determine gemcitabine chemosensitization in pancreatic cancer cells.
authors.affiliation: a Department of Radiation Oncology , University of Michigan Medical School , Ann Arbor , MI , USA.|b Department of Pharmacology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Parsels
authors.affiliation: b Department of Pharmacology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Daria M
authors.initials: DM
authors.lastname: Tanska
authors.affiliation: a Department of Radiation Oncology , University of Michigan Medical School , Ann Arbor , MI , USA.|b Department of Pharmacology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Parsels
authors.affiliation: c AstraZeneca R&D Boston , Waltham , MA , USA.|d Zabludoff Consulting San Diego , CA , USA.
authors.forename: Sonya D
authors.initials: SD
authors.lastname: Zabludoff
authors.affiliation: a Department of Radiation Oncology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Kyle C
authors.initials: KC
authors.lastname: Cuneo
authors.affiliation: a Department of Radiation Oncology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Lawrence
authors.affiliation: a Department of Radiation Oncology , University of Michigan Medical School , Ann Arbor , MI , USA.|b Department of Pharmacology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Maybaum
authors.affiliation: a Department of Radiation Oncology , University of Michigan Medical School , Ann Arbor , MI , USA.
authors.forename: Meredith A
authors.initials: MA
authors.lastname: Morgan
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1 / Q000037:antagonists & inhibitors*; D056744:Cyclin B1 / Q000378:metabolism; D004249:DNA Damage; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D059565:G2 Phase Cell Cycle Checkpoints; D006801:Humans; D008938:Mitosis; D015739:Nocodazole / Q000494:pharmacology; D010190:Pancreatic Neoplasms / Q000188:drug therapy; D013876:Thiophenes / Q000494:pharmacology*; D014508:Urea / Q000031:analogs & derivatives* / Q000494:pharmacology; D000093542:Gemcitabine
chemical_list: C532363:3-(carbamoylamino)-5-(3-fluorophenyl)-N-(3-piperidyl)thiophene-2-carboxamide; D000964:Antimetabolites, Antineoplastic; C534699:CCNB1 protein, human; D056744:Cyclin B1; D013876:Thiophenes; D003841:Deoxycytidine; D014508:Urea; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D015739:Nocodazole; D000093542:Gemcitabine
keywords: AZD7762; CHK1; aberrant mitotic entry; checkpoint abrogation; gemcitabine; pancreatic cancer