The Mutation Spectrum and Two Novel Point Mutations in the APC Gene in Vietnamese Patients with Familial Adenomatous Polyposis

Background: Familial adenomatous polyposis (FAP) is a hereditary disorder primarily caused by germline mutations in the APC gene. The most common type of mutation in the APC gene is point mutation, while deletion mutation is much less frequent. The current study was conducted to investigate the mutation spectrum of the APC gene in Vietnamese FAP patients. Methods: Patients with the clinical diagnosis of FAP on colorectal endoscopy were screened for mutations in the APC gene using Sanger sequencing. Those who exhibited no point mutation subsequently underwent MLPA assay to detect deletion and duplication mutations. Besides, the relatives of patients with mutated APC genes were recruited for detecting carrier status. Results: Sixty-three patients with clinical colorectal polyposis were recruited. Mutations in the APC gene were detected in 26/63 patients (41.3%). Genetic analysis of 105 asymptomatic relatives of these 26 patients found mutations in the APC gene in 55 individuals (52.4%). Conclusion: We successfully established the APC gene mutation spectrum in Vietnamese FAP patients for the first time. Of importance, we discovered two novel point mutations in the APC gene. The high prevalence of carrier status in asymptomatic family members of patients with mutation emphasizes the crucial role of appropriate genetic screening for early diagnosis, surveillance, and preventive measurements.     

Somatic Mutation of the APC Gene in Thyroid Carcinoma Associated with Familial Adenomatous Polyposis

We report the existence of both germline and somatic mutations of the APC gene in thyroid carcinomas from familial adenomatous polyposis (FAP) patients. One papillary thyroid carcinoma from a 20-year-old woman, with germline mutation of the APC gene (TCA to TGA at codon 1110), showed a somatic mutation of AAAAC deletion between codons 1060 and 1063. Another somatic mutation of CAG to TAG at codon 886 was also found in one of multiple thyroid carcinomas from a 26-year-old woman with attenuated FAP and germline mutation at codon 175 (C deletion). This is the first evidence that total absence of the normal function of the APC gene is involved in development of thyroid carcinomas in FAP.     

3例家族性腺瘤性息肉病家系诊治分析

目的 分析一家族性腺瘤性息肉病（FAP）家系的临床表型,对显性发病患者确定结肠镜随访间隔时间,探讨大数量切除结肠息肉的安全性与临床意义。 方法 在确定先证者后,对该家族成年成员进行结肠镜检查,对发现的显性发病患者进行结肠息肉的结肠镜下治疗以及随访。 结果 该家系成员共25人,其中女性14人,男性11人;显性发病3人,均属于传统型FAP,其中女性2人,男性1人且为其中1位女性之子;向上家系追溯,该家系有3位女性发病且故于结肠癌。自2007年10月至2012年11月,对3例显性发病患者共进行结肠镜随访与治疗27次,切除息肉1 801枚,除2枚（2.5 cm和3.0 cm）分别进行息肉剥脱+圈套切除术外,其余息肉均采用高频电圈套法、热活检钳摘除与灼除等方式。在集中处理高危息肉后,结肠镜随访间隔时间为每6月1次。手术过程安全,随访中未发现癌变腺瘤,但发现高危腺瘤（伴鱼鳞样黏膜）。结论 结肠镜下大数量切除结肠息肉具有较高的安全性,此种方式对不接受结肠手术的人群具有临床意义。从预防角度初步确定结肠镜随访间隔时间为6月,但需要进一步探讨,包括同时增加药物预防措施。     

Chromosome Changes in Desmoid Tumors Developed in Patients with Familial Adenomatous Polyposis

Chromosome analyses were performed on benign desmoid tumors obtained from two female patients with familial adenomatous polyposis (FAP), one of whom was diagnosed as having Gardner syndrome (GS). The modal chromosome number was 46 in both specimens, and detailed Q-banding analysis in Case 1 (GS) revealed a clonal abnormality of an interstitial deletion of the long arm of chromosome 5, del(5)(q2lq31). The deleted region included an assigned locus for an FAP major gene (5q21-q22). All of the metaphases analyzed in this case showed an extra segment of bright fluorescence on the short arm of chromosome 15, but this unusual chromosome (15p +) was observed in both peripheral lymphocyte and skin fibroblast cultures from the patient, indicating that the 15p+ was constitutional in nature. In Case 2, no clonal rearrangements were Identified and most cells had a normal karyotype. However, two cells showed rearrangements involving a 17q with non-identical breakpoints, one of which was observed as a solitary chromosome change. Based on the present findings in Case 1 and those reported so far, the chromosomal defect on 5q might be one of the causal genetic events primarily associated with the development of both benign desmoid tumors and colorectal adenomas and carcinomas in FAP patients.     

云南省家族性腺瘤性息肉病APC基因胚系突变的研究

目的研究云南省家族性腺瘤性息肉病(FAP)APC基因胚系突变的特点。方法收集云南地区10个FAP家系,抽取10例先证者的外周静脉血,提取脱氧核糖核酸(DNA),应用聚合酶链反应(PCR)方法扩增APC基因,应用DNA自动测序仪进行测序。结果 10例FAP先证者中,1例检出APC基因致病突变,此突变存在于APC基因第15外显子上c.3587 C>A(S1196X);随后对检出突变的先证者家系中另外8名成员进行该突变位点筛查,其中7人有突变。结论云南地区FAP患者APC基因致病突变检出率明显低于国内外报道;未检出APC基因致病突变的FAP患者可能存在其他发病的因素。     

Evaluation of Endoscopic Characteristics of Upper Gastrointestinal Polyps in Patients with Familial Adenomatous Polyposis

Background: Familial adenomatous polyposis (FAP) is a disease inherited in an autosomal dominant fashion. Most FAP patients develop upper gastrointestinal polyps; especially those in the antrum and duodenum are usually neoplastic. The aim of this study was to evaluate the prevalence of gastroduodenal polyps in Iranian FAP patients. Materials and Methods: 28 patients affected by FAP underwent front-view and side-view endoscopy. Papillary biopsies were performed in all patients. Location of polyps, their number and size, pathology study, patient general information (gender, age, family history of FAP or colorectal cancer and gastroduodenal polyps) were analyzed. Results: Gastric polyps were seen in 39.3 % of patients. Some 72.7% of the affected individuals had fundic gland polyps and 36.36% had hyperplastic polyps. Duodenal adenoma was observed in 25% of patients. While 57% of patients had tubular adenoma with low grade dysplasia, 42.8% showed tubulovillous adenoma with low grade dysplasia. Conclusions: Findings of this study indicated that the prevalence of gastroduodenal polyps in FAP patients is high and dysplasia may be evident in duodenal polyps. Therefore, it appears that routine gastroduodenal endoscopy in FAP patients is necessary.     

Familial Adenomatous Polyposis: Experience from a Study of 1164 Unrelated German Polyposis Patients

The autosomal-dominant precancerous condition familial adenomatous polyposis (FAP) is caused by germline mutations in the tumour suppressor gene APC. Consistent correlations between the site of mutations in the gene and clinical phenotype have been published for different patient groups. We report our experiences of APC mutation analysis and genotype-phenotype correlations in 1166 unrelated polyposis families and discuss our results in the light of literature data. We show that the mutation detection rates largely depend on the family history and clinical course of the disease. We present a list of 315 different point mutations and 37 large deletions detected in 634 of the 1166 index patients. Our results confirm previously published genotype-phenotype correlations with respect to the colorectal phenotype and extracolonic manifestations. However, 'exceptions to the rule' are also observed, and possible explanations for this are discussed. The discovery of autosomal-recessive MUTYH-associated polyposis (MAP) as a differential diagnosis to FAP implies that some results have to be reinterpreted and surveillance guidelines in the families have to be reevaluated.     

In the Beginning There Was Colectomy: Current Surgical Options in Familial Adenomatous Polyposis

Multiple colonic polyps, almost guaranteed colorectal cancer by the age of forty-five and an increased risk of non-colonic cancers characterise the autosomal dominant condition Familial Adenomatous Polyposis (FAP) [1]. The patients and families faced with such a diagnosis present many difficult management challenges, both surgical and non-surgical. We discuss the current surgical options for treatment of the more significant manifestations of FAP arising in the colorectum and duodenum as well as desmoid disease     

Congenital Hypertrophy of Retinal Pigment Epithelium for Diagnosis of Familial Adenomatous Polyposis - the First FAP registry in Iran

Objective: Familial adenomatous polyposis (FAP), an autosomal dominant inherited disorder is characterized by the presence of multiple adenomatous colorectal polyps, which can develop into cancer during early adulthood. Therefore, early diagnosis is essential. Most FAP patients have several extracolonic manifestations, including congenital hypertrophy of the retinal pigment epithelium (CHRPE). Whereas genetic markers may provide the main route to detection of ‘‘at risk’’ subjects , at present this approach is clearly limited and searches for a noninvasive phenotypic marker continue to be high priority.The aim of this study was to describe the pattern of distribution of CHRPE lesions and evaluate their diagnostic value in FAP patients and their family members in a local population. Methods: A total of 23 FAP patients and 26 relatives belonging to 12 families at high risk of developing FAP were subjected to colonoscopic and ophthalmological examination. Result: Retinal examinations demonstrated prevalences of CHRPE in FAP patents and their siblings of 78% and 38%, respectively. We were able to illustrate a significant correlation between FAP disease and the presence of retinal lesions. Sensitivity and specificity of CHRPE as a screening test to detect the presence of FAP are 78.3% and 61.5%, respectively, with a positive predictive value of 64.3% and a negative predictive value of 76.2 %. A "lesion form" significant difference was found between FAP and normal participants.Spearman nonparametric analysis revealed no correlation between age and number or size of lesions. Conclusion: Multiple CHRPE lesions are a diagnostic feature of FAP patients They are specific and sensitive clinical markers of this disease (specificity 60% and sensitivity 77%).     

Colon Cancer Prevention by Detection of APC Gene Mutation in a Family with Attenuated Familial Adenomatous Polyposis

Background: Genetic mutation is a significant factor in colon CA pathogenesis. Familial adenomatous polyposis(FAP) is an autosomal dominant hereditary disease characterized by multiple colorectal adenomatous polypsaffecting a number of cases in the family. This report focuses on a family with attenuated familial adenomatouspolyposis (AFAP) with exon 4 mutation, c.481C>T p.Q161X of the APC gene. Methods: We analyzed 20 membersof a family with AFAP. Clinical and endoscopic data were collected for phenotype determination. Genetic analysiswas also performed by direct sequencing of the APC gene. Result: Five patients with a phenotype of AFAP werefound. Endoscopic polyposis was demonstrated among the second generation with genotype mutation of thedisease (age > 50 years) consistent with delayed phenotypic adenomatous polyposis in AFAP. APC gene mutationwas identified in exon 4 of the APC gene, with mutation points of c.481C>T p.Q161X. Laparoscopic subtotalcolectomy was performed to prevent carcinogenesis. Conclusion: A family with attenuated familial adenomatouspolyposis of APC related to exon 4 mutation, c.481C>T p.Q161X, was reported and the phenotypic finding wasconfirmed by endoscopic examination. Genetic mutation analysis might be advantageous in AFAP for longterm colon cancer prevention and management due to subtle or asymptomatic phenotype presentation in earlyadulthood.     

Using genotype to assist clinical surveillance: a retrospective study of Chinese familial adenomatous polyposis patients

Without treatment, familial adenomatous polyposis (FAP) patients will inevitably develop colorectal cancer (CRC) during lifetime. Yet, surgical trauma is a high risk of desmoid tumor (DT), one of the main causes of death in FAP patients. So far, the timing for colectomy is primarily based on the clinician’s experience and the patient’s preference; most patients undergo surgery at mid-20’s. In this study, we analyzed the germline mutation distribution in 35 FAP patients from different families, 16 of them diagnosed with DTs. We also investigated the association between the molecular alterations and the clinicopathological features. Capture-based targeted sequencing using a panel of 520 genes was performed on tumor tissue and paired normal mucosa or white blood cells from 18 FAP probands who were initially diagnosed with CRC. Of all 35 FAP patients, 30 (85.7%) of them harbored germline APC mutations scattered from codon 161 to 1578. The mutations in the 16 DT patients scattered from codon 457 to 1578. All three patients with the mutation at the 3’ of 1444 codon were diagnosed with DT. The percentage of high-risk DT (stage III or IV) harboring mutations at the 5’ of 1062 or 1062-1578 was 14.3% and 77.8%, respectively, and all three patients with 3’ of 1399 codon mutation had high risk. In addition, by using public database, we compared 140 FAP patients with DT to all 1880 FAP patients on the Leiden Open Variation Database and found that the odd ratio of DT in codon 159 to 495 was 0.34, while in codon 1310 to 2011 was 2.36. Compared to sporadic CRCs, the somatic spectrum of FAP CRCs was similar to the early onset CRCs, with higher TP53 (94.1%) and lower somatic APC mutations (65.7%), but the KRAS mutation rate was the highest (58.5%). One of the 18 FAP CRCs was identified as microsatellite instability-high (MSI-H), with tumor mutation burden (TMB) of 115.65 mut/Mb. Given that no TP53 mutations were detected in the low- and high-grade adenomas, ctDNA TP53 sequencing might be used for the close monitoring before FAP colectomy. In conclusion, except mutations at the 5’ end of APC (5’ to 495), all FAP patients need to consider the risk of DT after colectomy. The chance of life-threating DTs was higher in patients with 3’ 1062 codon mutation and peaked in patients with 3’ 1399 codon mutation. Scheduled monitoring of TP53 ctDNA is proposed to be a novel tool for optimizing the operation time.     

Prevalence of MYH germline mutations in Swiss APC mutation-negative polyposis patients

In 10-30% of patients with classical familial adenomatous polyposis (FAP) and up to 90% of those with attenuated (<100 colorectal adenomas; AFAP) polyposis, no pathogenic germline mutation in the adenomatous polyposis coli (APC) gene can be identified (APC mutation-negative). Recently, biallelic mutations in the base excision repair gene MYH have been shown to predispose to a multiple adenoma and carcinoma phenotype. This study aimed to (i) assess the MYH mutation carrier frequency among Swiss APC mutation-negative patients and (ii) identify phenotypic differences between MYH mutation carriers and APC/MYH mutation-negative polyposis patients. Seventy-nine unrelated APC mutation-negative Swiss patients with either classical (n=18) or attenuated (n=61) polyposis were screened for germline mutations in MYH by dHPLC and direct genomic DNA sequencing. Overall, 7 (8.9%) biallelic and 9 (11.4%) monoallelic MYH germline mutation carriers were identified. Among patients with a family history compatible with autosomal recessive inheritance (n=45), 1 (10.0%) out of 10 classical polyposis and 6 (17.1%) out of 35 attenuated polyposis patients carried biallelic MYH alterations, 2 of which represent novel gene variants (p.R171Q and p.R231H). Colorectal cancer was significantly (p<0.007) more frequent in biallelic mutation carriers (71.4%) compared with that of monoallelic and MYH mutation-negative polyposis patients (0 and 13.8%, respectively). On the basis of our findings and earlier reports, MYH mutation screening should be considered if all of the following criteria are fulfilled: (i) presence of classical or attenuated polyposis coli, (ii) absence of a pathogenic APC mutation, and (iii) a family history compatible with an autosomal recessive mode of inheritance.     

Profuse familial adenomatous polyposis with an Adenomatous Polyposis Coli exon 3 mutation

The attenuated form of familial adenomatous polyposis coli (AAPC) is associated with mutations in the adenomatous polyposis coli (APC) gene which cluster in the 5 region of the gene. It has been proposed that a 'genotype–phenotype boundary' exists at codons 159–163, and mutations that are 5 of this boundary will produce AAPC. Herein we document a three-generation family with an exon 3 mutation well to the 5 side of the proposed boundary, in which two affected individuals have had, in their 40s, a profuse form of familial adenomatous polyposis coli. We conclude that the codon 159–163 'boundary' is indicative rather than definitive. These two patients also had postoperative intra-abdominal adhesions, severely so in one.     

Analysis of a panel of antibodies to APC reveals consistent activity towards an unidentified protein

Acquisition of truncating mutations in the adenomatous polyposis coli (APC) protein underlies the progression of the majority of sporadic and familial colorectal cancers. As such, the localisation patterns and interacting partners of APC have been extensively studied in a range of systems, relying on the use of a broad panel of antibodies. Until recently, antibodies to APC have been used largely unchecked. However, several recent reports have been invaluable in clarifying the use of a number of antibodies commonly used to detect APC. Here, we analyse the specificity of a further subset of antibodies to APC. We used a panel of six commercially available antibodies (directed to the amino and carboxy termini of APC) and confirm the detection of full-length APC by immunoblotting. We demonstrate that a 150 kDa protein, also reproducibly detected by this panel of antibodies, is unlikely to be APC. We present data for the immunological staining patterns of the APC antibodies and validate the results through RNAi. Using this approach, we confirm that the apical staining pattern, observed by immunofluorescence and previously reported in cell systems, is unlikely to be APC. Finally, we present our data as a summary of APC-antibody specificities for APC.     

Nuclear Localization of Immunoreactive β-Catenin Is Specific to Familial Adenomatous Polyposis in Papillary Thyroid Carcinoma

Thyroid carcinoma is the first symptom in some patients with familial adenomatous polyposis (FAP). We evaluated the cellular localization of β-catenin in thyroid carcinomas associated (n=4) or not associated (n=173) with FAP, since loss of functional protein of the adenomatous polyposis coli (APC) gene leads to nuclear accumulation of β-catenin in adenomas and carcinomas of the FAP colon. Immunoreactive β-catenin was demonstrated at the cell membrane of glandular cells of the non-neoplastic thyroid and non-FAP carcinomas. On the other hand, cytoplasmic and nuclear accumulation of β-catenin is specific to FAP-associated papillary carcinomas. The abnormality in the APC/β-catenin pathway is thus also important in FAP-associated thyroid carcinoma, and β-catenin immunohistochemistry is a feasible screening method to identify occult FAP in young patients with thyroid tumors.     

A Novel Exon Duplication Event Leading to a Truncating Germ-line Mutation of the APC Gene in a Familial Adenomatous Polyposis Family

Familial Adenomatous Polyposis (FAP) is an autosomal dominant condition predisposing to multiple adenomatous polyps of the colon. FAP patients frequently carry heterozygous mutations of the APC tumour suppressor gene. Affected individuals from a cohort of FAP families (n=22), where no germ-line APC mutation was detected by direct sequencing, were analysed by Multiplex Ligation-dependent Probe Amplification (MLPA). MLPA identified a previously unreported APC mutation involving duplication of exon 4. Subsequent analysis of cDNA from affected family members revealed expression of mutant mRNA species containing two copies of exon 4, resulting in a frameshift and premature stop codon. Bioinformatic analysis of the relevant APC genomic segment predicted a role for homologous recombination possibly involving Alu repeats in the generation of this genotype. Our results highlight the importance of MLPA as an adjunct to exon-by-exon sequencing in identifying infrequent mutational events in cancer predisposing genes. Amy McCart and Andrew Latchford contributed equally to this work.     

家族性结肠腺瘤病—家系分析

本文报道FP一个家族4代13人,发病5人,1人已有二处癌变,与常染色体显性遗传律完全相符。该病主诉多以粘液血便为主,发生时间也很不相同,极易癌变。其特点是癌变早,癌变率高,可多中心同时发生。治疗上作者推荐用全结肠和直肠粘膜切除,经直肠腔内施出回肠,行回肛吻合术。以免腺瘤复发和癌变。     

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) in familial colorectal cancer

Background and aim Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is a pigmented fundus lesion associated with familial adenomatous polyposis (FAP). CHRPE prevalence has been reported to be increased in subjects with familial or sporadic non-polyposis colorectal cancer (CRC), suggesting that some individuals with non-polyposis CRC have an attenuated form of FAP. Other studies have not confirmed these clinical observations and have failed to identify mutations in the gene responsible for FAP, but the reason for the discrepancy in relation to CHRPE prevalence has not been resolved. We determined the prevalence of CHRPE in subjects without CRC (negative control cohort), subjects with FAP (positive control cohort), and subjects with familial non-polyposis CRC (test cohort).Method A cohort study consisting of 37 negative control subjects, 9 positive control subjects with documented APC gene mutations, and 36 test subjects with familial non-polyposis CRC but no identified pathogenic APC gene mutation. The diagnosis of hereditary non-polyposis colon cancer was excluded in the test cohort by testing for microsatellite instability in tumour tissue.Results None of the 37 people in the negative control group had CHRPE. Five of nine (56%) patients with FAP had multiple CHRPE lesions. None of the 36 subjects in the test cohort had CHRPE lesions.Conclusions Ophthalmoscopy may contribute to risk assessment in families with FAP but not in familial non-polyposis CRC. Care must be exercised when interpreting pigmented fundus lesions because 8–13% of subjects in each of the cohorts had pigmented retinal lesions that were not CHRPE. Bilateral lesions and lesions with a depigmented halo␣were the hallmarks of CHRPE associated with FAP.     

Possible involvement of hyperlipidemia in increasing risk of colorectal tumor development in human familial adenomatous polyposis

BACKGROUND: Familial adenomatous polyposis (FAP) results from germline adenomatous polyposis coli (APC) gene mutations and many affected patients die from colorectal cancers which arise from colorectal polyps. We previously reported that two strains of Apc gene-deficient mice developing multiple intestinal polyps exhibit a hyperlipidemic state. The triglyceride (TG) levels were approximately 10-fold higher than the levels observed in wild-type mice. METHODS: To examine whether a positive relationship might exist between hyperlipidemia and colorectal tumor development in FAP patients, as with Apc gene-deficient mice, a pilot experiment was performed using readily available clinical data such as ages, serum lipid levels, number of colorectal polyps and cancer development in 28 FAP patients from the National Cancer Center Hospital, Japan. RESULTS: The overall prevalence of hyperlipidemia in FAP cases was 58%. Average TG levels in the 40-60 year age groups of FAP patients were > or =150 mg/dl (the defined threshold level of hyperlipidemia). Moreover, there was a tendency for higher serum TG levels in patients who developed colorectal cancer, as compared with those without colorectal cancer. CONCLUSIONS: These results show that a hyperlipidemic state occurs in FAP patients. Although it is weaker than that in Apc gene-deficient mice, it may be linked to colon tumor development. These data warrant further studies for wider populations of FAP patients.     

Thyroid cancer complicating familial adenomatous polyposis: mutation spectrum of at-risk individuals

Background

Lifetime risk of thyroid cancer associated with FAP has been reported as 1-2%. The mean age at diagnosis of thyroid carcinoma in FAP has been reported at 28 years. The aims of this paper are to better understand gene mutations associated with thyroid cancer and refine surveillance recommendations for patients with FAP.

Methods

We performed a search in Pubmed, Ovid Medline and Embase with the terms ("Thyroid Gland"[Mesh] OR "Thyroid Neoplasms"[Mesh]) AND "Adenomatous Polyposis Coli"[Meshdenomatous Polyposis Coli"[Mesh] to identify subjects with thyroid cancer and FAP. As a reference group for APC mutations in the unselected FAP population, we used the UMD-APC database referenced in the Orphanet portal, which includes APC mutation data on 2040 individuals with FAP.

Results

There were 115 reported cases of thyroid cancer in patients with FAP (95 female: 11 male) with an average age of 29.2 years. Gene mutation testing results were reported in 48 patients. On comparing the prevalence of APC mutation in the population of FAP patients with thyroid cancer and the prevalence of the same mutation in the reference population an increased odds ratio was evident in individuals harboring an APC mutation at codon 1061 (OR: CI 4.1: 1.7-8.9). Analysis of the prevalence of thyroid cancer in individuals with FAP segregated by the region of the gene affected shows an increased risk of thyroid cancer in individuals harboring mutations proximal to codon 512 (OR 2.6, p 0.0099).

Conclusions

There is increased risk for thyroid cancer in individuals with APC mutations at the 5' end (proximal to codon 528) along with the established high risk group harboring mutation at codon 1061. It is suggested that these patients might benefit from directed surveillance by annual ultrasound from age 18 years onwards.