Clinical characterization and mutation spectrum in patients with familial adenomatous polyposis in China

Monoallelic deleterious MUTYH mutations generate colorectal cancer: A case report

Here we reported a particular case of MUTYH-associated polyposis (MAP) that had only one rare heterozygous variant, but some particular clinical manifestations contributed to occur in this male patient by only one defective MUTYH allele were worth of further investigation. We reported a case of MAP. It is about a 33-year-old man with chief complaints of hematochezia who had multiple polyps that were found in his colon via colonoscopy. He followed his doctor's advice and performed a genetic analysis examination. Germline test was positive for a major heterozygous variant: chr1:45800165 on the MUTYH gene. MUTYH gene sequence analysis confirmed the following heterozygous variant: c.55CT (p.R19X) in exon 2 (ClinVar NM_001128425). Unfortunately, his mother and daughter have the ILK variant according to genetic analysis. However, this variant at the site was not detected in his father. Various types of polyps were found on repeated colonoscopy, which tended to become latent cancerous in the future. This case indicated that awareness of the risk of carcinogenesis of polyps in carriers of monoallelic variants might accordingly increase, and our understanding of the type of genetically related disease will be enhanced by us.

The Progress of Colorectal Polyposis Syndrome in Chinese Population

The pathogenesis, clinical phenotype, treatment strategy, and family management of hereditary tumor syndromes are different from those of sporadic tumors. Nearly a quarter of patients with colorectal cancer show significant familial aggregation and genetic predisposition, and 5 to 10% are associated with definite genetic factors. According to the clinical phenotype, it can be divided into nonpolyposis syndrome and polyposis syndrome. Among the polyposis syndrome patients with definite clinical symptoms, there are still some patients with unknown etiology (especially attenuated familial adenomatous polyposis), which is a difficult problem in clinical diagnosis and treatment. Therefore, for this rare disease, it is urgent to carry out multicenter studies, complete the gene variation spectrum, explore new pathogenic factors, and accumulate clinical experience. This article mainly introduces the research progress and related work of colorectal polyposis syndrome in China.

Update on Surgical Management of FAP

Familial adenomatous polyposis (FAP) is an autosomal dominant disease caused by pathogenic germline adenomatous polyposis coli mutation, and characterized with multiple adenomas in the colon and the rectum. Various genetic variants have been confirmed to be associated with corresponding FAP phenotypes, which play important roles in the diagnosis and surgical treatment of FAP. Generally, proctocolectomy is recommended for FAP patients at the age of 20s. Exceptionally, for patients with attenuated FAP, high-risk of desmoid, chemoprevention therapy, or other circumstances, surgery can be postponed. With the wide application of minimal invasive surgery in colorectal cancer, laparoscopic, robotic surgery, and natural orifice specimen extraction are proved to be feasible for FAP patients, but high-level evidences are needed to confirm their safety and advantages. In the times of precise medicine, the surgical management of FAP should vary with individuals based on genotype, phenotype, and clinical practice. Therefore, in addition to innovation in surgical procedures, investigation in links between genetic features and phenotypes will be helpful to optimize the surgical management of FAP in the future.

Factors influencing age at onset of colorectal polyps and benefit-finding after polypectomy

Screening, followed by colonoscopic polypectomy, has been widely performed in China. However, factors influencing age at onset of colorectal polyps and benefit-finding after polypectomy have been insufficiently studied or ignored. A total of 152 patients with colorectal polyps first detected in First Affiliated Hospital of Huzhou University from July to September 2022 were enrolled in this study. We selected 11 factors associated with the risk of colorectal polyps, including gender, body mass index, occupational stress, education level, income satisfaction, smoking, alcohol consumption, exercise frequency, diet, family history and polyp characteristics. Benefit-finding after polypectomy was obtained by follow-up for 142 of these patients. Multivariate linear regression analysis showed that being overweight (i.e., body mass index ≥25 kg/m2), higher education level, lower exercise frequency, and refrigerated food preference were associated with early-onset colorectal polyps. Patients with a preference for pickled food and age ≥50 years at first colorectal polyp detection had lower benefit findings after colonoscopic polypectomy. Colorectal polyps may develop earlier in people who are overweight, well-educated, exercise less, and prefer refrigerated food. In addition, patients who prefer pickled food and age at onset ≥50 years have lower benefit-finding requiring more attention in future colonoscopy follow-ups.

An update of the variant spectrum of the APC gene in Iranian familial adenomatous polyposis patients

Familial adenomatous polyposis (FAP) is an autosomal dominant colorectal cancer syndrome that is characterized by the development of multiple adenomas in the colon and rectum with high penetrance rates. This disease has specific features like the occurrence of pathogenic variations in the APC gene and diverse FAP phenotypes due to the occurrence region. In this study we aimed to evaluate pathogenic variants in exons of the APC gene in Iranian patients with FAP. A total of 35 FAP individuals were referred to the gastroenterology ward of Taleghani Hospital. As the aim of the study was to study the germline variations in the participants, the peripheral blood was collected and after the DNA extraction, PCR, and Sanger sequencing processes for the APC gene, the results were evaluated by the ACMG classification guidelines to report their pathogenicity. Accordingly, out of eight specific detected variants, three of them were novel, and the rest were reported previously. These eight variants were all truncating protein and pathogenic, and they were limited to 849-1378 codons. Overall, detected variants revealed discrepancies and parallels with previous reported cases in terms of quantity, occurrence region, and association with demographic and clinicopathological characteristics of patients. The spectrum of detected variants and the patient's phenotype showed distinct characteristics, such as occurrence in specific regions and the absence of extracolonic symptoms like Congenital hypertrophy of the retinal pigment epithelium (CHRPE). These findings open the path to comprehending the typical symptoms, their rarity, and their occurrence in the Iranian population and also due to the facts, we found that the studying of the APC gene alone for diagnosing FAP disease is not sufficient, and considering other genes are completely rational in the case of sequencing and studying the variants.

Genotype-Phenotype Correlations in Autosomal Dominant and Recessive APC Mutation-Negative Colorectal Adenomatous Polyposis

The most prevalent type of intestinal polyposis, colorectal adenomatous polyposis (CAP), is regarded as a precancerous lesion of colorectal cancer with obvious genetic characteristics. Early screening and intervention can significantly improve patients' survival and prognosis. The adenomatous polyposis coli (APC) mutation is believed to be the primary cause of CAP. There is, however, a subset of CAP with undetectable pathogenic mutations in APC, known as APC (-)/CAP. The genetic predisposition to APC (-)/CAP has largely been associated with germline mutations in some susceptible genes, including the human mutY homologue (MUTYH) gene and the Nth-like DNA glycosylase 1 (NTHL1) gene, and DNA mismatch repair (MMR) can cause autosomal recessive APC (-)/CAP. Furthermore, autosomal dominant APC (-)/CAP could occur as a result of DNA polymerase epsilon (POLE)/DNA polymerase delta 1 (POLD1), axis inhibition protein 2 (AXIN2), and dual oxidase 2 (DUOX2) mutations. The clinical phenotypes of these pathogenic mutations vary greatly depending on their genetic characteristics. Therefore, in this study, we present a comprehensive review of the association between autosomal recessive and dominant APC (-)/CAP genotypes and clinical phenotypes and conclude that APC (-)/CAP is a disease caused by multiple genes with different phenotypes and interaction exists in the pathogenic genes.

Genotype-phenotype correlation of small-intestinal polyps on small-bowel capsule endoscopy in familial adenomatous polyposis

BACKGROUND AND AIMS

In familial adenomatous polyposis (FAP), neoplastic lesions outside the colon have become increasingly important. The genotype-phenotype correlation has been established for duodenal polyps, and regular screening is recommended. However, this correlation remains unclear for small-intestinal lesions, except for reports on the relationship between their occurrence and Spigelman stage. Here, we used small-bowel capsule endoscopy (SBCE) to investigate the genotype-phenotype correlation of small-intestinal polyps in FAP.

METHODS

The genotype-phenotype correlation of small-intestinal polyps was investigated in patients with FAP who underwent SBCE, Esophagogastroduodenoscopy (EGD), and adenomatous polyposis coli (APC) gene analysis. Of 64 patients with FAP who underwent SBCE, 41 were included in the final analysis, 4 did not undergo a complete small intestine examination, and 19 did not undergo genetic analysis.

RESULTS

The prevalence (median number) of small-intestinal polyps by Spigelman stage was 26% (1.5), 0% (0), 44% (5), 60% (4), and 73% (25.5) for stages 0 to IV, respectively. Significantly more small-intestinal polyps were found in Spigelman stage III and IV groups than in the stage 0 group (P < .05). The APC variant was negative for 6 patients (15%), and the sites associated with more than 5 small-intestinal polyps were codons 278, 1062, 1114, 1281, 1307, 1314, and 1504.

CONCLUSIONS

In FAP patients, SBCE surveillance is potentially recommended for patients with pathogenic variants in the APC gene at codons 278 and 1062 to 1504 or with Spigelman stage III or higher.

Germline mutations of the adenomatous polyposis coli (APC) gene in Algerian familial adenomatous polyposis cohort: first report

BACKGROUND

Familial adenomatous polyposis (known also as classical or severe FAP) is a rare autosomal dominant colorectal cancer predisposition syndrome, characterized by the presence of hundreds to thousands of adenomatous polyps in the colon and rectum from an early age. In the absence of prophylactic surgery, colorectal cancer (CRC) is the inevitable consequence of FAP. The vast majority of FAP is caused by germline mutations in the adenomatous polyposis coli (APC) tumor suppressor gene (5q21). To date, most of the germline mutations in classical FAP result in truncation of the APC protein and 60% are mainly located within exon 15.

MATERIAL AND METHODS

In this first nationwide study, we investigated the clinical and genetic features of 52 unrelated Algerian FAP families. We screened by PCR-direct sequencing the entire exon 15 of APC gene in 50 families and two families have been analyzed by NGS using a cancer panel of 30 hereditary cancer genes.

RESULTS

Among 52 FAP index cases, 36 had 100 or more than 100 polyps, 37 had strong family history of FAP, 5 developed desmoids tumors, 15 had extra colonic manifestations and 21 had colorectal cancer. We detected 13 distinct germline mutations in 17 FAP families. Interestingly, 4 novel APC germline pathogenic variants never described before have been identified in our study.

CONCLUSIONS

The accumulating knowledge about the prevalence and nature of APC variants in Algerian population will contribute in the near future to the implementation of genetic testing and counseling for FAP patients.

Chinese consensus on prevention of colorectal neoplasia (2021, Shanghai)

Most patients with colorectal cancer (CRC) were diagnosed in advanced stage and the prognosis is poor. Therefore, early detection and prevention of CRC are very important. As with other cancers, there is also the tertiary prevention for CRC. The primary prevention is etiological prevention, which is mainly the treatment of adenoma or inflammation for preventing the development into cancer. The secondary prevention is the early diagnosis and early treatment for avoiding progressing to advanced cancer. The tertiary prevention belongs to the broad category of prevention, mainly for advanced CRC, through surgical treatment and postoperative adjuvant chemotherapy, radiotherapy, targeted therapy, immunotherapy for preventing tumor recurrence or metastasis. This consensus is based on the recent domestic and international consensus guidelines and the latest progress of international researches in the past five years. This consensus opinion seminar was hosted by the Chinese Society of Gastroenterology and Cancer Collaboration Group of Chinese Society of Gastroenterology, and was organized by the Division of Gastroenterology and Hepatology & Shanghai Institute of Digestive Disease, Renji Hospital, School of Medicine, Shanghai Jiao Tong University. The consensus opinion contains 60 statement clauses, the standard and basis of the evidence-based medicine grade and voting grade of the statement strictly complied with the relevant international regulations and practice.

Definition and management of colorectal polyposis not associated with APC/MUTYH germline pathogenic variants: AIFEG consensus statement

An expert consensus panel convened by the Italian Association for Inherited and Familial Gastrointestinal Tumors (Associazione Italiana per lo Studio della Familiarità ed Ereditarietà dei Tumori Gastrointestinali, AIFEG) reviewed the literature and agreed on a number of position statements regarding the definition and management of polyposis coli without an identified pathogenic mutation on the APC or MUTYH genes, defined in the document as NAMP (non-APC/MUTYH polyposis).

Association of Pathogenic Missense and Nonsense Mutations in Mitochondrial COII Gene with Familial Adenomatous Polyposis (FAP)

Nuclear genetic mutations have been extensively investigated in solid tumors. However, the role of the mitochondrial genome remains uncertain. Since the metabolism of solid tumors is associated with aerobic glycolysis and high lactate production, tumors may have mitochondrial dysfunctions. Familial adenomatous polyposis (FAP) is a rare form‌ of colorectal cancer and an autosomal dominant inherited condition that is characterized by the progress of numerous adenomatous polyps in the rectum and colon. The present study aimed at understanding the nature and effect of mitochondrial cytochrome c oxidase subunit 2 (COII) gene mutations in FAP tumorigenesis. Fifty-six (26 familial and 30 sporadic) FAP patients and 60 normal controls were enrolled in this study. COII point mutations were evaluated by PCR and direct sequencing methods, and a total of 7 mtDNA mutations were detected (3 missense, 1 nonsense, and 3 synonymous variations). Novel non-synonymous COII gene mutations were mostly in heteroplasmic state. These mutations change amino acid residues in the N-terminal and C-terminal regions of COXII. Bioinformatics analysis and three-dimensional structural modeling predicted that these missense and nonsense mutations have functional importance, and mainly affected on cytochrome c oxidase (complex IV). Also, FAP patients carried a meaningfully higher prevalence of mutations in the COII gene in comparison with healthy controls (P <0.001). Analysis of cancer-associated mtDNA mutation could be an invaluable tool for molecular assessment of FAP so that these findings can be helpful for the development of potential new biomarkers in the diagnosis of cancer for future clinical assessments.