A novel pathogenic large germline deletion in adenomatous polyposis coli gene in a Chinese family with familial adenomatous polyposis

An APC Mutation in a Large Chinese Kindred With Familial Adenomatous Polyposis Was Identified Using Both Next Generation Sequencing and Simple STR Marker Haplotypes

Background

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder characterized primarily by the development of numerous adenomatous polyps in the colon and a high risk for colorectal cancer. FAP is caused by germline mutations of the adenomatous polyposis coli (APC) gene. The proband in this family was a 39-year-old female patient with the pathologic diagnosis of adenomatous polyps, and then a five-generation kindred with FAP was characterized in the following years. This article identified an APC mutation, and demonstrated the practical use of APC-linked STR markers, which could be used to reduce misdiagnosis of prenatal diagnosis or preimplantation genetic diagnosis resulted from contamination or allele drop-out.

Methods

Next-generation sequencing (NGS) was used to identify the possible APC mutations in an affected individual from a family with autosomal dominant colon cancer. Targeted sequencing then used to identify additional related individuals with the mutation. Three short tandem repeat (STR) loci, D5S299, D5S134, and D5S346, were used for PCR-based microsatellite analysis of the APC gene in the extended family.

Results

We identified an APC: p.W553X mutation. The STR haplotype at the APC locus, A1B4C1, was shared by all clinically affected individuals with the APC: p.W553X mutation. In addition, the APC: p.D1822V variant was observed in 40% affected individuals and in two unaffected individuals.

Conclusion

We described a protein truncation mutation, APC: p.W553X; demonstrated the value of APC-linked STR markers (D5S299, D5S134, and D5S346) haplotypes; and suggested the potential role of these haplotypes in detecting loss of heterozygosity of the APC gene.

Adenomatous Polyposis Coli Gene Mutations in 22 Chinese Pedigrees with Familial Adenomatous Polyposis

Background

Familial adenomatous polyposis (FAP), which has a very high tendency of progression to colorectal cancer, is mainly caused by mutations of the adenomatous polyposis coli (APC) gene. This study systematically screened the APC mutations and observed the correlation of APC mutations with clinical manifestations of FAP.

Material/Methods

Eighty subjects (probands and their family members of 22 FAP pedigrees) were enrolled, underwent abdominal ultrasound, computed tomography, and colonoscopic examinations, and were assessed for APC mutations between January 2010 and June 2015 at Tianjin Union Medical Center. Peripheral blood was collected from subjects, and DNA was extracted and screened for APC mutations using multiplex ligation-dependent probe amplification for large-fragment deletions or PCR-denaturing high-performance liquid chromatography with DNA sequencing for micromutations.

Results

Nineteen of 22 FAP pedigrees were found to have mutations of APC, and 17 types APC mutations were identified. All the mutations were heterozygosity with autosomal dominant inheritance. APC mutations included 8 caused by frameshift, 3 by aberrant splicing, 2 by missense mutation, 2 by nonsense mutation, and 2 by large-fragment deletion. Frameshift mutation was the most common type of APC mutation, and Coding DNA Sequence 15 was the most common mutation site. Five novel APC mutations, including 1 with large-fragment deletion, were identified.

Conclusions

We systematically screened 17 mutations of APC from 22 Chinese pedigrees with FAP. This study will broaden the spectrum of known APC germline mutations and help understand the types and distribution of APC mutations among Chinese patients with FAP.

A novel large germ line deletion in adenomatous polyposis coli (APC) gene associated with familial adenomatous polyposis

Background

Familial adenomatous polyposis (FAP) is a familial colorectal cancer predisposition syndrome characterized by the development of numerous colorectal polyps, which is inherited in an autosomal dominant manner. FAP is caused by germ line mutations in adenomatous polyposis coli (APC) gene. Here, we described the identification of a causative APC gene deletion associated with FAP in an Iranian family.

Methods

Diagnosis of FAP was based on clinical findings, family history, and medical records (colonoscopy and histopathological data) after the patients were referred to Reza Radiotherapy and Oncology Center, Iran, for colonoscopy. Blood samples were collected, and genomic DNA was extracted. APC mutation screening was conducted by target next‐generation sequencing and quantitative real‐time PCR.

Results

A novel heterozygous large deletion mutation, c.(135+1_136–1)_(*2113+1_*2114–1) spanning exon 3 to 16 [EX3_16 DEL] of APC gene (GenBank Accession# MG712911), was detected in a proband and all her affected relatives in five generations, which was absent in unaffected family members and normal controls.

Conclusions

This novel deletion is the first report, describing the largest deletion of APC gene. Our novel finding contributes to a more comprehensive database of germ line mutations of APC gene that could be used in medical practice for the molecular diagnosis, risk assessment susceptibility of the disease for the FAP patients.

iTRAQ-based proteomic analysis of DMH-induced colorectal cancer in mice reveals the expressions of β-catenin, decorin, septin-7, and S100A10 expression in 53 cases of human hereditary polyposis colorectal cancer

PURPOSE

The aim of this study is to explore the roles of β-catenin, decorin, septin-7, and S100A10 expression in colorectal cancer development.

METHODS

Twenty-five BALB/c mice were divided into five groups; four groups were administrated N,N-dimethylhydrazine for 0, 10, 15, and 20 weeks, and one group was administrated normal saline for 20 weeks. The colons were collected for histopathological analysis. Protein samples prepared from the frozen colon tissues of mice treated with N,N-dimethylhydrazine for the different time points were evaluated using the isobaric tags for relative and absolute quantification (iTRAQ) labeling technique coupled with the 2D liquid chromatography-tandem mass spectrometry analysis. Based on the proteomic analysis results, immunohistochemical staining of β-catenin, decorin, septin-7, and S100A10 was performed in paraffin-embedded mice colorectal tissue, and 53 cases of human hereditary polyposis colorectal cancer samples.

RESULTS

Colorectal cancer was observed in mice treated with N,N-dimethylhydrazine for 20 weeks, and adenomas were observed in mice subjected to the 10-, and 15-week treatments. Seventy-two differentially expressed proteins were involved in the development of cancer as per the iTRAQ and spectrometry analysis. In normal epithelium, adenoma, and cancer from human hereditary polyposis colorectal cancer, S100A10 expression (c2 = 100.989, P = 0.000) was highest in cancer, whereas decorin (c2 = 12.852, P = 0.002) and septin-7 (c2 = 66.519, P = 0.002) expressions were highest in the normal epithelium, which was confirmed via immunohistochemical staining.

CONCLUSIONS

The subcellular localization of β-catenin and decorin, septin-7, and S100A10 expressions are associated with the development of colorectal cancer in mice after N,N-dimethylhydrazine treatment and in human hereditary polyposis colorectal cancers.

A novel APC mutation identified in a large Chinese family with familial adenomatous polyposis and a brief literature review

Familial adenomatous polyposis (FAP), an autosomal dominant disease, is a colon cancer predisposition syndrome that manifests as a large number of adenomatous polyps. Mutations in the Adenomatous polyposis coli (APC) gene are responsible for the majority of cases of FAP. The purpose of the present study was to report the clinical features of a Chinese family with FAP and screen for novel mutations using the targeted next‑generation sequencing technology. Among the 29 family members, 12 were diagnosed of FAP. Based on an established filtering strategy and data analyses, along with confirmation by Sanger sequencing and co‑segregation, a novel frameshift mutation c.1317delA (p.Ala440LeufsTer14) in exon 10 of the APC gene was identified. To the best of our knowledge, this mutation has not been reported prior to the present study. In addition, it was correlated with extra‑colonic phenotypes featuring duodenal polyposis and sebaceous cysts in this family. This novel frameshift mutation causing FAP not only expands the germline mutation spectrum of the APC gene in the Chinese population, but it also increases the understanding of the phenotypic and genotypic correlations of FAP, and may potentially lead to improved genetic counseling and specific treatment for families with FAP in the future.

A novel pathogenic splice acceptor site germline mutation in intron 14 of the APC gene in a Chinese family with familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant precancerous condition, clinically characterized by the presence of multiple colorectal adenomas or polyps. Patients with FAP has a high risk of developing colorectal cancer (CRC) from these colorectal adenomatous polyps by the mean age of diagnosis at 40 years. Germline mutations of the APC gene cause familial adenomatous polyposis (FAP). Colectomy has recommended for the FAP patients with significant polyposis. Here, we present a clinical molecular study of a four generation Chinese family with FAP. Clinical diagnosis of FAP has been done according to the phenotype, family history and medical records. Patient's blood samples were collected and genomic DNA was extracted. In order to identify the pathogenic mutation underlying the disease phenotype targeted next-generation sequencing and confirmatory sanger sequencing has undertaken. Targeted next generation sequencing identified a novel heterozygous splice-acceptor site mutation [c.1744-1G>A] in intron 14 of APC gene, which is co-segregated with the FAP phenotypes in the proband and amongst all the affected family members. This mutation is not present in unaffected family members and in normal healthy controls of same ethnic origin. According to the LOVD database for Chinese colorectal cancer patients, in Chinese population, 60% of the previously reported APC gene mutations causes FAP, are missense mutations. This novel splice-acceptor site mutation causing FAP in this Chinese family expands the germline mutation spectrum of the APC gene in the Chinese population.