A novel tissue‐based ß‐catenin gene and immunohistochemical analysis to exclude familial adenomatous polyposis among children with hepatoblastoma tumors

Abstract

Background: The Wnt/ -catenin pathway plays a central role in the pathogenesis of most hepatoblastomas (HBs), that is, up to 60-80% carry activating CTNNB1 mutations. HBs can however also be the first manifestation of familial adenomatous polyposis (FAP). As this is a severe disease, it is important for the patient and related family members to firmly exclude FAP at an early stage.Current diagnosis largely depends on APC germline mutation detection on genomic DNA, which is associated with 10-20% false-negative results. Here, we establish and validate a tissue-basedcatenin gene and immunohistochemical analysis, which complements germline mutation screening to exclude the diagnosis of FAP among HB patients.Methods: Tumor tissues of 18 HB patients, including three FAP cases were subjected to CTNNB1 exon 3 mutational analysis and immunohistochemistry comparing staining patterns for total and exon 3 specific -catenin antibodies.Results: Our novel tissue-based method reliably identified all three FAP patients. Their tumors were characterized by a wild-type exon 3 sequence and a comparable nuclear staining for both antibodies. In contrast, the non-FAP tumors carried missense CTNNB1 mutations combined with a clearly reduced staining for the exon 3 antibody, or complete loss of staining in case of lesions with exon 3 deletions. Conclusion:We have successfully established and validated a novel ß-catenin gene and immunohistochemical diagnostic method, which, when combined with routine germline DNA testing, allows the exclusion of the diagnosis of FAP among HB patients.

Wnt/β-Catenin Signaling in Liver Cancers

“…Activation of the Wnt/β-catenin signaling pathway is deemed an important hallmark during the development of hepatoblastomas [96]. Around 60–80% of hepatoblastomas possess activating mutations in CTNNB1 , including point mutation or deletions in exon 3 [97]. Other mutations observed occur in APC (20.51%), AXIN1 (1.67%), AXIN2 (3.75%), and LGR6 (12.5%) [82].…”

DNA methylation in Hepatoblastoma-a literature review

“…to activate the transcription of downstream target genes [ 8 ]. Approximately 60–80% of HBs have CTNNB1 mutations, including point mutations and deletions in exon 3 [ 9 ]. Other genes with mutations in HBs include APC (20.51%), AXIN1 (1.67%), AXIN2 (3.75%), and leucine-rich repeat-containing G protein-coupled receptor 6 (LGR6) (12.5%) [ 10 ].…”

Response to: An immunohistochemical approach to detect oncogenic CTNNB1 mutations in primary neoplastic tissues

“…The 8E7 clone used by the authors, was shown to recognize residues 36-44 and provide a positive staining for the commonly observed S33 and S45 β-catenin mutations [4]. The same holds true for another commercially available exon 3 antibody (clone D13A1) [3]. In some cases both antibodies may identify tumors carrying these mutations, but this may be the result of a strong hyperphosphorylation of S37/T41, which will also preclude antibody binding.…”

“…Akyol et al describe a straightforward and elegant method to identify tumors carrying such mutations using paraffin sections. We have used an identical approach to exclude familial adenomatous polyposis (FAP) carriers among children with hepatoblastoma tumors, thereby supporting the genetic counseling process [3]. The method is based on staining consecutive slides of the tumor for total and exon 3-specific β-catenin monoclonal antibodies.…”