Novel germline mutations in the APC gene of Cypriot patients with familial and sporadic adenomatous polyposis

Germline Mutations in CDH23, Encoding Cadherin-Related 23, Are Associated with Both Familial and Sporadic Pituitary Adenomas

Pituitary adenoma (PA) is one of the most common intracranial neoplasms. Several genetic predisposing factors for PA have been identified, but they account for a small portion of cases. In this study, we sought to identify the PA genetic risk factors by focusing on causative mutations for PAs. Among the 4 affected and 17 asymptomatic members from one family with familial PA, whole-exome sequencing identified cosegregation of the PA phenotype with the heterozygous missense mutation c.4136G>T (p.Arg1379Leu) in cadherin-related 23 (CDH23). This mutation causes an amino acid substitution in the calcium-binding motif of the extracellular cadherin (EC) domains of CDH23 and is predicted to impair cell-cell adhesion. Genomic screening in a total of 12 families with familial PA (20 individuals), 125 individuals with sporadic PA, and 260 control individuals showed that 33% of the families with familial PA (4/12) and 12% of individuals with sporadic PA (15/125) harbored functional CDH23 variants. In contrast, 0.8% of the healthy control individuals (2/260) carried functional CDH23 variants. Gene-based analysis also revealed a significant association between CDH23 genotype and PA (p = 5.54 × 10^-7). Moreover, PA individuals who did not harbor functional CDH23 variants displayed tumors that were larger in size (p = 0.005) and more invasive (p < 0.001). Therefore, mutations in CDH23 are linked with familial and sporadic PA and could play important roles in the pathogenesis of PA.

Cancer trends and risk factors in Cyprus

Cyprus, a European Union member state, is a small island in the Mediterranean with a population approaching 900,000 people. Cancer is the second leading cause of death; more therapeutic options for any patient with the disease are available in a central oncology centre in the capital of the island (Nicosia) and fewer therapeutic options (e.g. chemotherapy and hormone therapy only) in a few other public hospitals. Palliative care is offered in several hospices and hospitals, although the field needs improvement. With regards to screening, a national breast cancer screening programme has been in place countrywide since 2007 and is offered free of charge to women between the ages of 50 and 69 years, while colorectal and prostate cancer screening is performed on an individual basis (a pilot programme for colorectal cancer screening was recently initiated). Genetic testing is available for breast and colon cancer. To improve understanding of the causes of cancer in the country, a cancer research centre was established in 2010 (Mediterranean Centre for Cancer Research). Recent epidemiologic work has revealed increasing cancer trends in Cyprus; prostate cancer is the most common in men and breast cancer is the most common in women. Interestingly, thyroid cancer incidence in women has been rising from 1998 to 2008. Cancer of the colon and rectum is also on the rise affecting both sexes. Overall, cancer incidence in Cyprus is lower than other EuroMed countries with similar lifestyle and geography.

A De Novo Germline APC Mutation (3927del5) in a Patient with Familial Adenomatous Polyposis: Case Report and Literature Review

Introduction

Characterized by the development of hundreds to thousands of colonic adenomas, classic familial adenomatous polyposis (FAP) is one of the most common hereditary syndromes associated with an increased risk of colorectal cancer. Several studies have attempted to correlate specific APC mutations with clinical phenotype.6 However, there is considerable variability in the expression of specific phenotypes within families and among individuals with identical mutations.7

Case presentation

A 30 year-old Hispanic female presented to the emergency department with a 2-week history of persistent, worsening, left lower quadrant abdominal pain. She had no family history of malignancy. Sigmoidoscopy revealed innumerable polyps in the rectum and sigmoid colon and a large mass in the sigmoid colon. Biopsy of the mass revealed a moderately differentiated adenocarcinoma invading the subserosa. Endoscopy revealed innumerable polyps. Genetic testing of the patient via southern blot revealed a germline APC mutation 3927del5, resulting in a premature truncation of the APC protein at amino acid position 1312.

Conclusion

Genetic information has only recently started being incorporated into clinical care. More research and randomized clinical trials need to be conducted to definitively characterize random mutations. Once these mutations are further understood, FAP patients may be able to be risk stratified and this may ultimately improve the screening, diagnosis, and treatment of this rare condition.

Somatic APC inactivation mechanisms in sporadic colorectal cancer cases in Hungary

The role of germline inactivation of the adenomatosis polyposis coli (APC) gene in hereditary colorectal cancer is well known, being the most important cause of familial adenomatosus polyposis (FAP) syndrome. Hereditary cases with germline mutations, however, account only for 5-10% of colorectal cancers. The somatic inactivation of this gene has also been observed in sporadic cases. In order to examine the inactivation mechanisms of the APC gene we screened 70 sporadic colorectal cancer cases (27 rectal, 43 intestinal) of different stages for promoter hypermethylation, allelic imbalance (AI) and somatic mutations. The presence of promoter hypermethylation was observed in 21 cases (30%). Fifteen of the examined tumors (21%) showed AI, and also 15 tumors (21%) carried at least one somatic mutation. Thirteen of the detected alterations were novel variations: seven frameshifts, four missense mutations and two polymorphisms. Biallelic inactivation was found in 15 patients (21%). These results suggest that the inactivation of the APC gene is very common in sporadic colorectal cancer, and the main inactivation mechanism of the APC gene is promoter hypermethylation. Allelic imbalance has the same frequency as mutations, and mutations in the APC gene are more common in the early stages and in tumors located in the rectum.