title: CHK2 overexpression and mislocalisation within mitotic structures enhances chromosomal instability and hepatocellular carcinoma progression.
abstract: Chromosomal instability (CIN) is the most common form of genomic instability, which promotes hepatocellular carcinoma (HCC) progression by enhancing tumour heterogeneity, drug resistance and immunity escape. CIN per se is an important factor of DNA damage, sustaining structural chromosome abnormalities but the underlying mechanisms are unknown.
  
  
  
  DNA damage response protein checkpoint kinase 2 (Chk2) expression was evaluated in an animal model of diethylnitrosamine-induced HCC characterised by DNA damage and elevated mitotic errors. Chk2 was also determined in two discrete cohorts of human HCC specimens. To assess the functional role of Chk2, gain on and loss-of-function, mutagenesis, karyotyping and immunofluorescence/live imaging were performed by using HCT116, Huh7 and human hepatocytes immortalised with hTERT gene (HuS).
  
  
  
  We demonstrate that mitotic errors during HCC tumorigenesis cause lagging chromosomes/DNA damage and activation of Chk2. Overexpression/phosphorylation and mislocalisation within the mitotic spindle of Chk2 contributes to induce lagging chromosomes. Lagging chromosomes and mitotic activity are reversed by knockdown of Chk2. Furthermore, upregulated Chk2 maintains mitotic activity interacting with Aurora B kinase for chromosome condensation and cytokinesis. The forkhead-associated domain of Chk2 is required for Chk2 mislocalisation to mitotic structures. In addition, retinoblastoma protein phosphorylation contributes to defective mitoses. A cohort and independent validation cohort show a strong cytoplasm to nuclear Chk2 translocation in a subset of patients with HCC.
  
  
  
  The study reveals a new mechanistic insight in the coinvolvement of Chk2 in HCC progression. These findings propose Chk2 as a putative biomarker to detect CIN in HCC providing a valuable support for clinical/therapeutical management of patients.
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Vinicio
authors.initials: V
authors.lastname: Carloni
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, General Pathology Unit, University of Florence, Florence, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Lulli
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Madiai
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, Gastroenterology Unit, University of Florence, Florence, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Mello
authors.affiliation: Department of Cellular Pathology, Royal Free Hospital, London, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hall
authors.affiliation: Department of Cellular Pathology, Royal Free Hospital, London, UK.
authors.forename: Tu Vinh
authors.initials: TV
authors.lastname: Luong
authors.affiliation: University College London (UCL) Institute for Liver & Digestive Health, London, UK.
authors.forename: Massimo
authors.initials: M
authors.lastname: Pinzani
authors.affiliation: University College London (UCL) Institute for Liver & Digestive Health, London, UK.
authors.forename: Krista
authors.initials: K
authors.lastname: Rombouts
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, Gastroenterology Unit, University of Florence, Florence, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Galli
mesh_terms: D000818:Animals; D064107:Aurora Kinase B / Q000378:metabolism; D001692:Biological Transport; D002273:Carcinogens; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D064447:Checkpoint Kinase 2 / Q000235:genetics* / Q000378:metabolism; D043171:Chromosomal Instability / Q000235:genetics*; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics* / Q000378:metabolism; D030541:Databases, Genetic; D004052:Diethylnitrosamine; D005260:Female; D055785:Gene Knockdown Techniques; D045325:HCT116 Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000235:genetics; D010766:Phosphorylation; D017208:Rats, Wistar; D016160:Retinoblastoma Protein / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics; D015854:Up-Regulation
chemical_list: D002273:Carcinogens; D004273:DNA, Neoplasm; D016160:Retinoblastoma Protein; D004052:Diethylnitrosamine; D064447:Checkpoint Kinase 2; C576921:AURKB protein, human; D064107:Aurora Kinase B; C578634:CHEK2 protein, human; C578632:Chek2 protein, rat
keywords: GENETIC INSTABILITY; HEPATOBILIARY CANCER