title: Exome sequencing of hepatoblastoma reveals novel mutations and cancer genes in the Wnt pathway and ubiquitin ligase complex.
abstract: Hepatoblastoma (HB) is the most common primary liver tumor in children. Mutations in the β-catenin gene that lead to constitutive activation of the Wnt pathway have been detected in a large proportion of HB tumors. To identify novel mutations in HB, we performed whole-exome sequencing of six paired HB tumors and their corresponding lymphocytes. This identified 24 somatic nonsynonymous mutations in 21 genes, many of which were novel, including three novel mutations targeting the CTNNB1 (G512V) and CAPRIN2 (R968H/S969C) genes in the Wnt pathway, and genes previously shown to be involved in the ubiquitin ligase complex (SPOP, KLHL22, TRPC4AP, and RNF169). Functionally, both the CTNNB1 (G512V) and CAPRIN2 (R968H/S969C) were observed to be gain-of-functional mutations, and the CAPRIN2 (R968H/S969C) was also shown to activate the Wnt pathway in HB cells. These findings suggested the activation of the Wnt pathway in HB, which was confirmed by immunohistochemical staining of the β-catenin in 42 HB tumors. We further used short hairpin RNA (shRNA)-mediated interference to assess the effect of 21 mutated genes on HB cell survival. The results suggested that one novel oncogene (CAPRIN2) and three tumor suppressors (SPOP, OR5I1, and CDC20B) influence HB cell growth. Moreover, we found that SPOP S119N is a loss-of-function mutation in HB cells. We finally demonstrated that one of the mechanisms by which SPOP inhibits HB cell proliferation is through regulating CDKN2B expression.
  
  
  CONCLUSIONS
  These results extend the landscape of genetic alterations in HB and highlight the dysregulation of Wnt and ubiquitin pathways in HB tumorigenesis.
authors.affiliation: State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Deshui
authors.initials: D
authors.lastname: Jia
authors.forename: Rui
authors.initials: R
authors.lastname: Dong
authors.forename: Ying
authors.initials: Y
authors.lastname: Jing
authors.forename: Dan
authors.initials: D
authors.lastname: Xu
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Qigen
authors.initials: Q
authors.lastname: Li
authors.forename: Yuping
authors.initials: Y
authors.lastname: Huang
authors.forename: Yuannv
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Shan
authors.initials: S
authors.lastname: Zheng
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xia
authors.forename: Hongyang
authors.initials: H
authors.lastname: Wang
authors.forename: Kuiran
authors.initials: K
authors.lastname: Dong
authors.forename: Xianghuo
authors.initials: X
authors.lastname: He
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000378:metabolism; D056915:DNA Copy Number Variations; D004252:DNA Mutational Analysis; D059472:Exome; D005260:Female; D018197:Hepatoblastoma / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D012097:Repressor Proteins / Q000235:genetics; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics*; D051153:Wnt Proteins / Q000235:genetics*; D055815:Young Adult; D051176:beta Catenin / Q000378:metabolism
chemical_list: C493966:CDKN2B protein, human; D050762:Cyclin-Dependent Kinase Inhibitor p15; D009687:Nuclear Proteins; D012097:Repressor Proteins; C509761:SPOP protein, human; D051153:Wnt Proteins; D051176:beta Catenin; D043743:Ubiquitin-Protein Ligase Complexes