Hepatoblastoma modeling in mice places Nrf2 within a cancer field established by mutant β-catenin
Sarah A. Comerford, … , Gail E. Tomlinson, Robert E. Hammer
Sarah A. Comerford, … , Gail E. Tomlinson, Robert E. Hammer
Published October 6, 2016
Citation Information: JCI Insight. 2016;1(16):e88549. https://doi.org/10.1172/jci.insight.88549.
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Research Article Hepatology Oncology

Hepatoblastoma modeling in mice places Nrf2 within a cancer field established by mutant β-catenin

Abstract

Aberrant wnt/β-catenin signaling and amplification/overexpression of Myc are associated with hepatoblastoma (HB), the most prevalent type of childhood liver cancer. To address their roles in the pathogenesis of HB, we generated mice in which Myc and mutant β-catenin were targeted to immature cells of the developing mouse liver. Perinatal coexpression of both genes promoted the preferential development of HBs over other tumor types in neonatal mice, all of which bore striking resemblance to their human counterparts. Integrated analysis indicated that tumors emerged as a consequence of Myc-driven alterations in hepatoblast fate in a background of pan-hepatic injury, inflammation, and nuclear factor (erythroid-derived 2)-like 2/Nrf2-dependent antioxidant signaling, which was specifically associated with expression of mutant β-catenin but not Myc. Immunoprofiling of human HBs confirmed that approximately 50% of tumors demonstrated aberrant activation of either Myc or Nfe2l2/Nrf2, while knockdown of Nrf2 in a cell line–derived from a human HB with NFE2L2 gene amplification reduced tumor cell growth and viability. Taken together, these data indicate that β-catenin creates a protumorigenic hepatic environment in part by indirectly activating Nrf2 and implicate oxidative stress as a possible driving force for a subset of β-catenin–driven liver tumors in children.

Authors

Sarah A. Comerford, Elizabeth A. Hinnant, Yidong Chen, Hima Bansal, Shawn Klapproth, Dinesh Rakheja, Milton J. Finegold, Dolores Lopez-Terrada, Kathryn A. O’Donnell, Gail E. Tomlinson, Robert E. Hammer

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Figure 6

Pan-hepatic expression of mutant β-catenin activates Nrf2-dependent antioxidant signaling.

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Pan-hepatic expression of mutant β-catenin activates Nrf2-dependent anti...
(A) Gene set enrichment analysis (GSEA) of β-catenin–regulated genes using gene sets consisting of previously annotated Nrf2 target genes and genes linked to glutathione metabolism. (B) Semiquantitative (Sq) RT-PCR of β-catenin–regulated Nrf2 target genes and other genes identified by array. mRNAs are elevated in livers expressing β-catenin (lanes 5–8) and are independent of Albumin-c-Myc transgene status. (C) Western blot analysis of NQO1 and p62/SQSTM1 expression in livers of WT (lanes 1 and 2), Alb-c-Myc (lanes 3 and 4), β-catΔEx3 (lanes 5 and 6), and β-catΔEx3:Myc (lanes 7 and 8) mice. In C, the asterisk denotes a lower molecular weight nonspecific band. (D) Sq RT-PCR showing that induction of the Nrf2 mRNA targets Nqo1 and Cbr3 and is solely a function of mutant β-catenin expression (lanes 11 and 12) and that expression of Cre recombinase, either by itself (lanes 4–6) or in combination with the Alb-c-Myc transgene (lanes 9 and 10), does not induce Nrf2 target gene expression. In D, the 85bp Nqo1 amplicon migrates just above the excess primers in the PCR reaction, denoted by the asterisk. C, Alb-Cre mice; M, Alb-c-Myc mice; CM, Alb-Cre:Alb-c-Myc bitransgenic mice; β, β-catΔEx3:Alb-Cre mice; βM, β-catΔEx3:Alb-Cre:Alb-c-Myc mice.