title: RNF43 germline and somatic mutation in serrated neoplasia pathway and its association with BRAF mutation.
abstract: Serrated polyps (hyperplastic polyps, sessile or traditional serrated adenomas), which can arise in a sporadic or polyposis setting, predispose to colorectal cancer (CRC), especially those with microsatellite instability (MSI) due to MLH1 promoter methylation (MLH1me+). We investigate genetic alterations in the serrated polyposis pathway.
  
  
  
  We used a combination of exome sequencing and target gene Sanger sequencing to study serrated polyposis families, sporadic serrated polyps and CRCs, with validation by analysis of The Cancer Genome Atlas (TCGA) cohort, followed by organoid-based functional studies.
  
  
  
  In one out of four serrated polyposis families, we identified a germline RNF43 mutation that displayed autosomal dominant cosegregation with the serrated polyposis phenotype, along with second-hit inactivation through loss of heterozygosity or somatic mutations in all serrated polyps (16), adenomas (5) and cancer (1) examined, as well as coincidental BRAF mutation in 62.5% of the serrated polyps. Concurrently, somatic RNF43 mutations were identified in 34% of sporadic sessile/traditional serrated adenomas, but 0% of hyperplastic polyps (p=0.013). Lastly, in MSI CRCs, we found significantly more frequent RNF43 mutations in the MLH1me+(85%) versus MLH1me-(33.3%) group (p<0.001). These findings were validated in the TCGA MSI CRCs (p=0.005), which further delineated a significant differential involvement of three Wnt pathway genes between these two groups (RNF43 in MLH1me+; APC and CTNNB1 in MLH1me-); and identified significant co-occurrence of BRAF and RNF43 mutations in the MSI (p<0.001), microsatellite stable (MSS) (p=0.002) and MLH1me+MSI CRCs (p=0.042). Functionally, organoid culture of serrated adenoma or mouse colon with CRISPR-induced RNF43 mutations had reduced dependency on R-spondin1.
  
  
  
  These results illustrate the importance of RNF43, along with BRAF mutation in the serrated neoplasia pathway (both the sporadic and familial forms), inform genetic diagnosis protocol and raise therapeutic opportunities through Wnt inhibition in different stages of evolution of serrated polyps.
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Helen H N
authors.initials: HHN
authors.lastname: Yan
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Jeffrey C W
authors.initials: JCW
authors.lastname: Lai
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Siu Lun
authors.initials: SL
authors.lastname: Ho
authors.affiliation: Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Wai Keung
authors.initials: WK
authors.lastname: Leung
authors.affiliation: Department of Surgery, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Wai Lun
authors.initials: WL
authors.lastname: Law
authors.affiliation: Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Janet F Y
authors.initials: JFY
authors.lastname: Lee
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Anthony K W
authors.initials: AKW
authors.lastname: Chan
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Wai Yin
authors.initials: WY
authors.lastname: Tsui
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Annie S Y
authors.initials: ASY
authors.lastname: Chan
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Bernard C H
authors.initials: BCH
authors.lastname: Lee
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Sarah S K
authors.initials: SSK
authors.lastname: Yue
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Alice H Y
authors.initials: AHY
authors.lastname: Man
authors.affiliation: Hubrecht Institute for Developmental Biology and Stem Cell Research, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Clevers
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Siu Tsan
authors.initials: ST
authors.lastname: Yuen
authors.affiliation: Hereditary Gastrointestinal Cancer Genetic Diagnosis Laboratory, Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong.
authors.forename: Suet Yi
authors.initials: SY
authors.lastname: Leung
mesh_terms: D000236:Adenoma / Q000235:genetics* / Q000473:pathology; D000328:Adult; D003111:Colonic Polyps / Q000235:genetics* / Q000473:pathology; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D004268:DNA-Binding Proteins / Q000235:genetics*; D005190:Family; D005260:Female; D020022:Genetic Predisposition to Disease; D005820:Genetic Testing / Q000379:methods; D006723:Hong Kong; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D000070957:MutL Protein Homolog 1 / Q000378:metabolism*; D009154:Mutation; D015513:Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases; D060449:Wnt Signaling Pathway / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; D015513:Oncogene Proteins; C496945:RNF43 protein, human; D044767:Ubiquitin-Protein Ligases; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D000070957:MutL Protein Homolog 1
keywords: CANCER GENETICS; CANCER SYNDROMES; COLONIC POLYPS; COLORECTAL CANCER GENES; GENETIC TESTING