title: Apoptosis, cell cycle progression and gene expression in TP53-depleted HCT116 colon cancer cells in response to short-term 5-fluorouracil treatment.
abstract: Loss of TP53 function may contribute to 5-fluorouracil (5-FU) resistance in colorectal cancer since TP53-deficient cells may be unable to undergo apoptosis in response to 5-FU-induced DNA damage. 5-FU treatment of TP53-deficient cells would provide useful information on the apoptotic response to drug-induced DNA damage in the absence of TP53 and its transcriptional targets. We investigated apoptosis induction and cell cycle alterations in response to short-term treatment with two different 5-FU concentrations following siRNA-mediated knockdown of TP53 in the TP53-proficient HCT116 colon cancer cell line. We focused on high-dose 5-FU treatment to investigate the apoptotic phenotype in 5-FU-treated cultures since this dose resulted in apoptosis induction at 24 h of treatment, whereas clinically-relevant bolus 5-FU treatment of HCT116 cultures did not. Gene expression alterations were also assessed in 5-FU-treated HCT116 cultures using whole genome expression arrays. Compared to 5-FU-treated TP53-proficient HCT116 cultures, 5-FU-treated TP53-depleted HCT116 cultures showed lack of CDKN1A induction, decreased apoptotic levels, decreased FAS and TNFRSF10B transcript levels and cleaved PARP protein levels, G1/S transition arrests, decreased CCND1 protein levels, and smaller intra-S phase arrests. Alterations in gene expression in 5-FU-treated TP53-depleted HCT116 cultures confirmed previously-reported TP53 target genes and suggested potentially novel TP53 target genes (e.g. APOBEC3C, BIRC3, JMJD2B, LAMP3, MYO1E, PRRG1, SULF2, TACSTD2, TncRNA, ZFYVE20) that may play a role in mediating the 5-FU-induced DNA damage response in TP53-proficient cells. Abrogation of TP53 function in 5-FU-treated HCT116 cultures results in reduced apoptosis, TP53- and CDKN1A-independent G1/S phase arrests that may be protective against apoptosis, smaller intra-S phase arrests, and transcript level decreases of both reported TP53 target genes as well as potentially novel TP53 target genes.
authors.affiliation: The Pathology Clinic, Rikshospitalet-Radiumhospitalet Medical Center, Oslo, Norway.
authors.forename: Birgitte Lid
authors.initials: BL
authors.lastname: Adamsen
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Kravik
authors.forename: Ole P F
authors.initials: OP
authors.lastname: Clausen
authors.forename: Paula M
authors.initials: PM
authors.lastname: De Angelis
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D056741:Cyclin D; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology; D016213:Cyclins / Q000378:metabolism; D005472:Fluorouracil / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D045325:HCT116 Cells; D006801:Humans; D034741:RNA, Small Interfering / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: D000964:Antimetabolites, Antineoplastic; C493956:CDKN1A protein, human; D056741:Cyclin D; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D005472:Fluorouracil