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Gastroenterology. 2020 Mar 13. pii: S0016-5085(20)30336-X. doi: 10.1053/j.gastro.2020.03.015. [Epub ahead of print]

GERMLINE MUTATIONS IN FAF1 ARE ASSOCIATED WITH HEREDITARY COLORECTAL CANCER.

Author information

1
Gastroenterology Department, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Hospital Clínic, Universitat de Barcelona, Barcelona, Spain.
2
Molecular Oncology Laboratory, Centro Investigación Biomédica en Red de Cáncer (CIBERONC). Hospital Clínico San Carlos. Instituto de Investigación Sanitaria San Carlos (IdISSC). Madrid. Spain.
3
Hereditary Cancer Program, Catalan Institute of Oncology, Oncobell, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain.
4
Gene therapy and cancer. Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Universitat de Barcelona, Barcelona, Spain.
5
Pathology Department, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD) and Tumor Bank-Biobank, Hospital Clínic, Barcelona, Spain.
6
Gastroenterology Department, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Hospital Clínic, Universitat de Barcelona, Barcelona, Spain. Electronic address: sbel@clinic.cat.

Abstract

BACKGROUND & AIMS:

A significant proportion of colorectal cancer (CRC) cases have familial aggregation but little is known about the genetic factors that contribute to these cases. We performed an exhaustive functional characterization of genetic variants associated with familial CRC.

METHODS:

We performed whole-exome sequencing analyses of 75 patients from 40 families with a history of CRC (including early-onset cases) of an unknown germline basis (discovery cohort). We also sequenced specific genes in DNA from an external replication cohort of 473 families, including 488 patients with colorectal tumors that had normal expression of mismatch repair proteins (validation cohort). We disrupted the Fas associated factor 1 gene (FAF1) in DLD-1 CRC cells using CRISPR/Cas9 gene editing; some cells were transfected with plasmids that express FAF1 missense variants. Cells were analyzed by immunoblots, quantitative real-time PCR, and functional assays monitoring apoptosis, proliferation, and assays for Wnt signaling or NF-κB activity.

RESULTS:

We identified predicted pathogenic variant in the FAF1 gene (c.1111G>A; p.Asp371Asn) in the discovery cohort; it was present in 4 patients of the same family. We identified a second variant in FAF1 in the validation cohort (c.254G>C; p.Arg85Pro). Both variants encoded unstable FAF1 proteins. Expression of these variants in CRC cells caused them to become resistant to apoptosis, accumulate b-catenin in the cytoplasm, and translocate NF-kB to the nucleus.

CONCLUSIONS:

In whole-exome sequencing analyses of patients from families with a history of CRC, we identified variants in FAF1 that associate with development of CRC. These variants encode unstable forms of FAF1 that increase resistance of CRC cells to apoptosis and increase activity of b-catenin and NF-kB.

KEYWORDS:

Wnt signaling; functional genomics; gene editing; programmed cell death

PMID:
32179092
DOI:
10.1053/j.gastro.2020.03.015
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