title: Thymoquinone triggers inactivation of the stress response pathway sensor CHEK1 and contributes to apoptosis in colorectal cancer cells.
abstract: There are few reports describing the role of p53-dependent gene repression in apoptotic cell death. To identify such apoptosis-associated p53 target genes, we used the pro-oxidant plant-derived drug thymoquinone and compared p53+/+ and p53-/- colon cancer cells HCT116. The p53 wild-type (wt) status correlated with more pronounced DNA damage and higher apoptosis after thymoquinone treatment. A significant up-regulation of the survival gene CHEK1 was observed in p53-/- cells in response to thymoquinone due to the lack of transcriptional repression of p53. In p53-/- cells, transfection with p53-wt vector and CHEK1 small interfering RNA treatment decreased CHEK1 mRNA and protein levels and restored apoptosis to the levels of the p53+/+ cells. p53-/- cells transplanted to nude mice treated with thymoquinone up-regulated CHEK1 expression and did not undergo apoptosis unlike p53+/+ cells. Immunofluorescence analysis revealed that the apoptosis resistance in p53-/- cells after thymoquinone treatment might be conveyed by shuttling of CHEK1 into the nucleus. We confirmed the in vivo existence of this CHEK1/p53 link in human colorectal cancer, showing that tumors lacking p53 had higher levels of CHEK1, which was accompanied by poorer apoptosis. CHEK1 overexpression was correlated with advanced tumor stages (P = 0.03), proximal tumor localization (P = 0.02), and worse prognosis (1.9-fold risk, univariate Cox regression; Kaplan-Meier, P = 0.04). We suggest that the inhibition of the stress response sensor CHEK1 might contribute to the antineoplastic activity of specific DNA-damaging drugs.
authors.affiliation: Department of Biology, American University of Beirut, Beirut, Lebanon.
authors.forename: Hala
authors.initials: H
authors.lastname: Gali-Muhtasib
authors.forename: Doerthe
authors.initials: D
authors.lastname: Kuester
authors.forename: Christian
authors.initials: C
authors.lastname: Mawrin
authors.forename: Khuloud
authors.initials: K
authors.lastname: Bajbouj
authors.forename: Antje
authors.initials: A
authors.lastname: Diestel
authors.forename: Matthias
authors.initials: M
authors.lastname: Ocker
authors.forename: Caroline
authors.initials: C
authors.lastname: Habold
authors.forename: Charlotte
authors.initials: C
authors.lastname: Foltzer-Jourdainne
authors.forename: Peter
authors.initials: P
authors.lastname: Schoenfeld
authors.forename: Brigitte
authors.initials: B
authors.lastname: Peters
authors.forename: Mona
authors.initials: M
authors.lastname: Diab-Assaf
authors.forename: Ulf
authors.initials: U
authors.lastname: Pommrich
authors.forename: Wafica
authors.initials: W
authors.lastname: Itani
authors.forename: Hans
authors.initials: H
authors.lastname: Lippert
authors.forename: Albert
authors.initials: A
authors.lastname: Roessner
authors.forename: Regine
authors.initials: R
authors.lastname: Schneider-Stock
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D016227:Benzoquinones / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology*; D004249:DNA Damage; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D006801:Humans; D016016:Proportional Hazards Models; D011494:Protein Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species
chemical_list: D000970:Antineoplastic Agents; D016227:Benzoquinones; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C003466:thymoquinone