Germline Adenomatous Polyposis Coli Mutations Research Articles

Biomarkers in Gastroenterology: Between Hope and Hype Comes Histopathology

Gastrointestinal cancers account for approximately 25% of all cancer deaths in the Western world. There is a need for a preventive strategy that can utilize biomarkers in order to stratify patients into appropriate screening or surveillance programs. Biomarkers are clinical variables associated with clinical outcomes. In cancer biology, the best biomarkers are germline adenomatous polyposis coli mutations, which are highly predictive of colon cancer. In other areas, such as Barrett's esophagus, despite early excellent success in identifying the importance of p16, p53, and aneuploidy in esophageal adenocarcinoma pathogenesis, useful biomarkers are still not widely used in clinical practice. New molecular biomarkers may be identified in the next decade, such as epigenetic methylation patterns and genetic polymorphisms. In the meantime, clinicians must rely on robust, inexpensive methods such as standard histopathology. Dysplasia is still the mainstay of cancer prediction in most inflammatory disorders of the GI tract and is an independent marker of cancer risk.

Genetic Mechanisms in Apc-Mediated Mammary Tumorigenesis

Many components of Wnt/β-catenin signaling pathway also play critical roles in mammary tumor development, yet the role of the tumor suppressor gene APC (adenomatous polyposis coli) in breast oncongenesis is unclear. To better understand the role of Apc in mammary tumorigenesis, we introduced conditional Apc mutations specifically into two different mammary epithelial populations using K14-cre and WAP-cre transgenic mice that express Cre-recombinase in mammary progenitor cells and lactating luminal cells, respectively. Only the K14-cre–mediated Apc heterozygosity developed mammary adenocarcinomas demonstrating histological heterogeneity, suggesting the multilineage progenitor cell origin of these tumors. These tumors harbored truncation mutation in a defined region in the remaining wild-type allele of Apc that would retain some down-regulating activity of β-catenin signaling. Activating mutations at codons 12 and 61 of either H-Ras or K-Ras were also found in a subset of these tumors. Expression profiles of acinar-type mammary tumors from K14-cre; ApcCKO/+ mice showed luminal epithelial gene expression pattern, and clustering analysis demonstrated more correlation to MMTV-neu model than to MMTV-Wnt1. In contrast, neither WAP-cre–induced Apc heterozygous nor homozygous mutations resulted in predisposition to mammary tumorigenesis, although WAP-cre–mediated Apc deficiency resulted in severe squamous metaplasia of mammary glands. Collectively, our results suggest that not only the epithelial origin but also a certain Apc mutations are selected to achieve a specific level of β-catenin signaling optimal for mammary tumor development and explain partially the colon- but not mammary-specific tumor development in patients that carry germline mutations in APC.

Editorial: Dissecting GI Phenotype–Genotype Relationships in GERD and Dyspepsia: An SNP Here and an SNP There!

It is known that the predisposition to human disease is a mixture of inherited susceptibility and acquired exposure to environmental factors. Understanding gastrointestinal disease has indicated that germline adenomatous polyposis coli mutations predispose with a 99% certainty to colorectal cancer, whereas squamous esophageal cancer is caused by a combination of environmental exposures (including alcohol consumption, cigarette smoke, ingestion of contaminated preserved food) and/or infection (specifically with human papilloma virus), in most cases. Until now, despite the reasonably strong evidence for genetic risk from monozygotic twin studies for gastro-esophageal reflux disease (GERD), there have been no documented genetic targets in GERD. In this edition of the Journal, there is intriguing evidence that a common, single base-pair change in the secondary messenger gene GNbeta3 (i.e., a single-nucleotide polymorphism) may be important, perhaps through promoting abnormal perception of visceral pain in the esophagus. Other works link this genetic factor to functional dyspepsia, and these exciting preliminary lines of evidence are reviewed.

Germline APC Mutations Are Not Commonly Seen in Children With Sporadic Hepatoblastoma

Hepatoblastoma is the most common primary liver tumor in childhood and occurs more commonly in families with familial adenomatous polyposis. Germline mutations of the gene responsible for familial adenomatous polyposis--adenomatous polyposis coli (APC)--are described in patients with hepatoblastoma even without a family history. We investigated children presenting with apparently sporadic hepatoblastoma between 1991 and 2004. Blood samples were available from 29 children (18 boys) whose conditions were diagnosed at a median age of 22 months (range 6-119 months). No germline APC mutations were found, which does not support the need for routine screening in sporadic hepatoblastoma in the absence of a suggestive family history of colorectal cancer or suspicion of familial adenomatous polyposis.

DHPLC Analysis of Adenomatous Polyposis Coli (APC) Mutations Using Ready-to-Use APC Plates: Simple Detection of Multiple Base Pair Deletion Mutations

The adenomatous polyposis coli (APC), which is the susceptible gene for familial adenomatous polyposis (FAP) and sporadic colorectal cancer, spans 15 exons. The open reading frame of APC is 8529 bp, which encodes 2843 amino acids. Conventional genetic screening involves extensive time as well as high cost and labor. Thus, we developed a novel APC ready-to-use plate for high-throughput mutational analysis by denaturing high performance liquid chromatography (DHPLC). To prepare the ready-to-use APC plate, all 38 primer pairs and PCR mixtures were aliquoted into individual wells of a 96-well plate, and frozen at -20 degrees C until use. All 38 PCR primers were designed to be amplified at the same temperature (52 degrees C). We examined a total of 27 FAP patient samples with APC germline mutations (17 for multiple bp deletions, 1 for 1 bp deletion, 9 for nonsense mutations) and 50 APC-negative noncarriers. All 17 multiple bp deletion mutations were detected during the initial 50 degrees C running analysis and thus ruled out for further analyses. All other mutations were clearly detected under specific optimized conditions. More than 50% of the APC germline mutations were multiple base pair deletions and efficiently selected by omitting time-consuming partial denaturing conditions.

Cross-Species Comparison of Human and Mouse Intestinal Polyps Reveals Conserved Mechanisms in Adenomatous Polyposis Coli ( APC)-Driven Tumorigenesis

Expression profiling is a well established tool for the genome-wide analysis of human cancers. However, the high sensitivity of this approach combined with the well known cellular and molecular heterogeneity of cancer often result in extremely complex expression signatures that are difficult to interpret functionally. The majority of sporadic colorectal cancers are triggered by mutations in the adenomatous polyposis coli (APC) tumor suppressor gene, leading to the constitutive activation of the Wnt/beta-catenin signaling pathway and formation of adenomas. Despite this common genetic basis, colorectal cancers are very heterogeneous in their degree of differentiation, growth rate, and malignancy potential. Here, we applied a cross-species comparison of expression profiles of intestinal polyps derived from hereditary colorectal cancer patients carrying APC germline mutations and from mice carrying a targeted inactivating mutation in the mouse homologue Apc. This comparative approach resulted in the establishment of a conserved signature of 166 genes that were differentially expressed between adenomas and normal intestinal mucosa in both species. Functional analyses of the conserved genes revealed a general increase in cell proliferation and the activation of the Wnt/beta-catenin signaling pathway. Moreover, the conserved signature was able to resolve expression profiles from hereditary polyposis patients carrying APC germline mutations from those with bi-allelic inactivation of the MYH gene, supporting the usefulness of such comparisons to discriminate among patients with distinct genetic defects.

APC mutation spectrum in ileoanal pouch polyps resembles that of colorectal polyps

Ileoanal pouch polyps commonly develop following restorative proctocolectomy in patients with familial adenomatous polyposis (FAP). In FAP adenomas, the relationship between germline and somatic adenomatous polyposis coli (APC) mutations is determined by 'just right' beta-catenin signalling in tumour cells, with respect to the 20-amino acid beta-catenin-binding/degradation repeats (20AARs) in the APC protein. However, the relationship varies, with upper gastrointestinal polyps typically retaining three to four 20AARs and colonic polyps retaining one or two. The aim of this study was to establish the mutational spectrum in ileoanal pouch polyps, to ascertain whether polyp development resembled that typical of small or large bowel. Some 151 pouch adenomas were screened from 46 patients with known germline APC mutations for 'second hits' acquired through loss of heterozygosity and truncating mutations. The number of 20AARs remaining after the 'second hit' was calculated. Loss of heterozygosity was rare in pouch polyps except when the germline mutation left one 20AAR. Overall, the combined alleles left two to three 20AARs in 40 of 51 polyps with an identified 'second hit'. This was significantly fewer than in upper gastrointestinal polyps, and more than in colorectal adenomas. Tissue environment appears to influence the position of the 'second hit' in pouch polyps and the mutations resemble those of large bowel polyps.

Identification of a novel duplication in the APC gene using multiple ligation probe amplification in a patient with familial adenomatous polyposis

Germline mutations in the adenomatous polyposis coli (APC) gene cause familial adenomatous polyposis (FAP), an autosomal dominant disease characterized by hundreds to thousands of adenomatous polyps in the colon and rectum, with progression to colorectal cancer. The majority of APC mutations are nucleotide substitutions and frameshift mutations that result in truncated proteins. Recently, large genomic alterations of the APC gene have been reported in FAP. DNA from 15 FAP patients, in whom no APC germline mutations were detected with denaturing high performance liquid chromatography, was analyzed with multiplex ligation-dependent probe amplification (MLPA) to evaluate gross genomic alterations in the APC gene. In one case, MLPA identified a novel duplication of exons 2–6 in one copy of the APC gene. Reverse transcriptase–polymerase chain reaction revealed that the mutant allele contained an in-frame multiexon duplication including 18 nucleotides located in exon 2, upstream of the ATG initiation codon. The presence of a premature stop codon in the duplicated sequence leads to the synthesis of a truncated APC polypeptide. These findings highlight the utility of evaluating infrequent APC mutation events in FAP patients using MLPA.

The in Vivo Rate of Somatic Adenomatous Polyposis Coli Mutation

Cancer arises through successive somatic mutations/epimutations of oncogenes and tumor-suppressor genes. Accurate estimates of the rates at which these (epi)mutations occur are a vital but missing link in our emerging quantitative understanding of tumorigenesis. Their absence has hindered arguments concerning the importance of genetic instability in tumorigenesis and the number of mutations that precede malignant conversion of healthy cell lineages. Herein, a novel method for calculating the in vivo mutation rate of the adenomatous polyposis coli (APC) tumor-suppressor gene is presented. The large majority of bowel cancers are thought to be initiated by a partial loss of APC function, with the age-onset pattern dramatically altered for the worse in familial adenomatous polyposis (FAP) because these patients harbor selected germline APC mutations. Colon cancer in the context of FAP can be thought of as occurring "one hit quicker" than in the sporadic setting. We were able to isolate and estimate the rate of the initiating APC mutation in sporadic cases using the age incidence of FAP to approximate the time taken for a cell lineage in a sporadic patient with one APC mutation to present clinically as a cancer. Our result of approximately 10(-5) mutations per allele per year, although higher than previous estimates, appears to be consistent with the mutational spectrum of APC. The quality of fit provided by this method supports the theory that FAP and sporadic bowel cancer follow the same genetic pathway and are separated by only one mutation.

Wnt Pathway, Angiogenetic and Hormonal Markers in Sporadic and Familial Adenomatous Polyposis-associated Juvenile Nasopharyngeal Angiofibromas (JNA)

Juvenile nasopharyngeal angiofibroma (JNA) is a rare, invasive, and locally destructive tumor of the nasopharynx. The Wnt pathway, angiogenetic and hormonal factors are involved in the pathophysiology of JNA; it can result in an extracolonic manifestation of familial adenomatous polyposis (FAP) or in a sporadic tumor. All patients who underwent resection of JNA between 1991 and 2006 at the University of Modena and Reggio Emilia were studied to identify immunohistochemical markers of associated FAP syndrome. Paraffin-embedded JNA samples were analyzed immunohistochemically for the expression of adenomatous polyposis coli (APC), beta-catenin, E-cadherin, androgen receptor, and vascular endothelial growth factors receptor (VEGFR2). In one out of the 4 (25%) young patients affected by JNA the diagnosis of FAP syndrome linked to APC mutation was made. All of the sporadic and familial JNA tumors showed nuclear staining of beta-catenin, whereas altered APC expression was seen only in FAP-associated JNA. All cases were stained with VEGFR2. A combined clinical, immunohistochemical, and biomolecular screening may be useful for the identification of FAP among patients with a diagnosis of JNA. The Wnt pathway can be involved in the JNA pathogenesis either by somatic mutations of beta-catenin or by germline APC mutations. As the VEGFR has an important impact on the pathogenesis of JNA, we suggest that a targeted therapy with monoclonal antibodies against VEGFR might lead to a specific chemoprevention and treatment of these tumors and their recurrences.

Desmoid Tumors in a Dutch Cohort of Patients With Familial Adenomatous Polyposis

Desmoid tumors are a severe extracolonic manifestation in familial adenomatous polyposis (FAP). Identification of risk factors might be helpful in the management of FAP patients with such tumors. The aim of this study was to assess potential risk factors for the development of desmoids in a cohort of Dutch FAP patients. The medical records of 735 FAP patients were analyzed for the occurrence of desmoids. Relative risks and survival times were calculated to assess the influence of potential risk factors (female sex, family history, mutation site, abdominal surgery, and pregnancy) on desmoid development. Desmoid tumors were identified in 66 of the 735 patients (9%). The cumulative risk of developing desmoids was 14%. No correlation was found between specific adenomatous polyposis coli mutation sites and desmoid development. Patients with a positive family history for desmoids had a significant increased risk to develop this tumor (30% vs 6.7%, P < .001). No association was found between female sex or pregnancy and desmoid development. Most desmoid patients (95%) had undergone previous abdominal surgery. In a substantial proportion of patients with an ileorectal anastomosis, it was impossible to convert the ileorectal anastomosis to an ileal pouch-anal anastomosis as a result of desmoid development. A positive family history of desmoids is an evident risk factor for developing desmoids. Most desmoids develop after colectomy. No correlation was found between desmoids and the adenomatous polyposis coli gene mutation site, female sex, and pregnancy. Ileal pouch-anal anastomosis is the appropriate type of surgery in FAP patients with a positive family history for desmoids.

Inherited multitumoral syndromes including colorectal carcinoma

Inherited multitumoral syndromes including colorectal carcinoma are the followings: familial adenomatous polyposis (FAP), hereditary non-polyposis colon cancer (HNPCC) and Peutz-Jeghers syndrome (PJS). The studies of genotype-phenotype correlation have shown that various types of colonic polyposis are related with germline mutation of adenomatous polyposis coli (APC) gene, that is also responsible for a wide number of extracolonic manifestations. Concerning severity of polyposis, it has been suggested to perform ileorectal anastomosis in patients with intermediate FAP, whereas it has been suggested to remove the rectum from the beginning and to perform ileopouch anastomosis in patients with severe FAP (germline APC mutations between codons 1250 and 1464, i.e. mutation cluster region-MCR). Concerning extracolonic manifestations, original studies from our laboratory have shown that three peculiar, even if unusual extracolonic manifestations of FAP, were in the 5' portion of the gene, but almost always outside of MCR. In particular, in some patients or in some kindreds all these manifestations may be present together. It is suggested, from one hand, because of the wide variety of genotype-phenotype correlation word of caution before selecting surgical treatment simply on the basis of the germline mutations, on the other hand co-segregation of some extracolonic manifestations could facilitate intensive screening, early diagnosis and optimal time for treatment.

Germline mutations in APC and MUTYH are responsible for the majority of families with attenuated familial adenomatous polyposis

A small fraction of families with familial adenomatous polyposis (FAP) display an attenuated form of FAP (AFAP). We aimed to assess the presence of germline mutations in the MUTYH and adenomatous polyposis coli (APC) genes in AFAP families and to compare the clinical features between the two causative genes. Families with clinical AFAP were selected from the Dutch Polyposis Registry according to the following criteria: (a) at least two patients with 10-99 adenomas diagnosed at age >30 years or (b) one patient with 10-99 adenomas at age >30 years and a first-degree relative with colorectal cancer (CRC) with a few adenomas, and, applying for both criteria, no family members with more than 100 polyps before the age of 30 years. All probands were screened for germline mutations in the APC and MUTYH genes. Twenty-five of 315 Dutch families with FAP (8%) met our criteria for AFAP. These families included 146 patients with adenomas and/or CRC. Germline APC mutations were identified in nine families and biallelic MUTYH mutations in another nine families. CRC was identified at a mean age of 54 years (range 24-83 years) in families with APC and at 50 years (range 39-70 years) in families with MUTYH (p = 0.29). APC and biallelic MUTYH mutations are responsible for the majority of AFAP families. Based on our results and those reported in the literature, we recommend colonoscopy once every 2 years in AFAP families, starting surveillance from the late teens in APC mutation carriers and from age 20-25 years in biallelic MUTYH mutation carriers.

Germline mutations of the MYH gene in Korean patients with multiple colorectal adenomas

Most investigations on MutY human homolog (MYH)-associated polyposis (MAP) have been conducted in Western countries. Limited data on MAP in Asia are currently available. The present study investigated germline mutations of the MYH gene among patients with 10 to 99 adenomatous colorectal polyps and familial adenomatous polyposis (FAP) without adenomatous polyposis coli (APC) germline mutations in Korea. The study population included 46 patients with 10 to 99 adenomatous polyps in the colorectum and 16 FAP patients with no identified APC germline mutations. Subjects were screened for MYH germline mutations, and we additionally screened for MYH mutations in 96 normal control individuals. Two of 46 (4.3%) patients with multiple polyps displayed heterozygous biallelic germline mutations of the MYH gene. A 39-year-old male patient with biallelic MYH mutations (p.G272E and p.A359V) received total proctocolectomy for rectal cancer and 36 colorectal polyps. A 58-year-old female patient with biallelic MYH mutations (p.Q253X and p.Q440P) received right hemicolectomy for ascending colon cancer and 16 colonic polyps. The frequency of biallelic MYH mutation in 14 of 46 multiple-polyp patients, who had 15 to 99 polyps, was 14.3% (2 of 14). No biallelic MYH mutations were detected in the 32 patients with 10 to 14 colorectal polyps, 16 FAP patients, or 96 normal controls. We identified biallelic MYH germline mutations in 2 of 14 (14.3%) Korean patients with 15 to 99 colorectal polyps. In this study, there was no Y165C or G382D hot-spot mutation, which had been reported most frequently in previous studies.

Balance between endoscopic and genetic information in the choice of ileorectal anastomosis for familial adenomatous polyposis

The number of rectal polyps and the site of mutations in the APC (Adenomatous polyposis coli) gene have been used to guide the surgical management in patients with familial adenomatous polyposis (FAP). The aim of this study is to assess the utility of the APC mutation screening compared to the degree of the rectal polyposis in surgical decision making. The post-surgical courses of 25 patients submitted to subtotal colectomy with ileorectal anastomosis (IRA) were reviewed. Preservation of the rectum was prospectively decided on the basis of well-defined endoscopic criteria. The number of rectal polyps was assessed preoperatively and every 6-12 months. APC gene was screened for mutations by heteroduplex analysis, single strand conformation polymorphism, in vitro synthesized protein (IVSP), and DNA sequencing. Patients negative for APC mutations were tested for MYH mutations. On the basis of preoperative polyp rectal count we categorized patients as follows: Group I, 5 or fewer adenomas; Group II, 6-9 adenomas; Group III, 10 or more adenomas. After a follow-up ranging from 12 to 225 months we have observed a significant difference of recurrent rectal adenomas between Groups I-II versus III. No difference was detected among patients of Group I and II. The mean number of adenomas/year/patient was 0.67, 1.62, and 9.29 for Group I, II, and III, respectively. Carpeting polyposis of the rectal stump developed in three patients with APC mutation at codon 1309 and two of them needed later proctectomy. Diffuse rectal polyposis was observed in one patient with mutation at exon 9 who had 10 small polyps at time of surgery. Mutation at the 5'-end of APC (codons 144-232), mutation of MYH and unknown APC or MYH mutation were correlated with a low number of polyps both at presentation and follow-up. No IRA patients developed rectal cancer. In our experience fewer than 10 rectal polyps at presentation can predict a favorable outcome after IRA. Identification of specific germ-line APC or MYH mutation can address the choice of surgical treatment.

Modifiers of risk in familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant condition caused by mutations in the adenomatous polyposis coli (APC) gene. The phenotypic expression of FAP is extremely variable, and only part of this variability reflects the influence of different germline APC mutations. The remaining differences are likely attributable to the action of modifier genes and environmental (including pharmacologic) factors. In this review, we discuss recent investigations of candidate modifiers of FAP risk, including studies examining the roles of the MutY homolog, insulin-like growth factor-2, EphB receptors, detoxification enzymes, cyclooxygenase-2, and lipoprotein lipase. Identification of FAP modifier genes will provide new insight into the mechanisms of colorectal cancer development and may suggest novel therapeutic targets as well as candidate genes for colorectal cancer susceptibility in the general population.

Immunohistochemical Expression of MYH Protein Can Be Used to Identify Patients With MYH-Associated Polyposis

MYH-associated polyposis is a recently described, autosomal-recessive disease characterized by multiple colorectal adenomas and cancer. There are only few immunohistochemical studies of the MYH protein. We investigated the expression pattern of the MYH protein to evaluate whether a immunohistochemical approach could be used in clinical practice to screen patients for germline mutations in the MYH gene. The expression of MYH, MSH2, MLH1, and MSH6 proteins was studied by immunohistochemistry in 20 samples (colorectal adenomas or cancer) from 18 patients with biallelic MYH mutation, in 11 samples from patients with germline adenomatous polyposis coli (APC) mutations, in 20 samples from patients with sporadic colorectal cancers, and in 10 samples from patients with normal colonic mucosa without malignancies. In all cases the mismatch repair proteins were expressed normally. Nuclear and cytoplasmic immunoreactivity for the MYH protein were observed in normal colorectal mucosa, in sporadic colorectal carcinomas, and in adenomas and carcinomas from patients carrying APC germline mutations. Adenomas and carcinomas from patients with MYH biallelic mutation showed a different pattern of expression: a strong granular cytoplasmic staining was observed without any nuclear expression. The same immunophenotype was observed in the surrounding normal mucosa. Patients with biallelic MYH mutations showed disappearance of staining from the nucleus, and segregation of immunoreactivity in the cytoplasm, both in neoplastic and surrounding healthy mucosa. Because this pattern of expression seems to be specific for biallelic mutations, it follows that immunohistochemistry might be used in clinical practice to screen patients at risk for MYH-associated polyposis.

Detection of APC gene deletion by double competitive polymerase chain reaction in patients with familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant familial cancer syndrome caused by germline mutations of the tumor suppressor adenomatous polyposis coli (APC) gene. Heterozygous apc mutations have been identified in the majority of classical FAP patients who develop more than 100 colorectal adenomas. However, classical FAP patients often fail to display germline APC mutations detectable by routine mutation analysis. These apparently mutation-negative cases may be caused by heterozygous large genomic deletions. In the present study, FAP patients who showed no APC germline mutation detectable by the protein truncation assay and direct sequencing of protein coding exons were screened for APC gene deletion by a gene dose assay based on double competitive polymerase chain reaction. Gene dosage measurements within exon 15 of the APC gene identified two patients with gene deletion and one with possible gene duplication among 41 apparently mutation-negative patients. The deleted sequences in the two patients were determined by fine gene dose mapping around the APC gene and nucleotide sequencing of the deletion breakpoints. They were approximately 435-kilobase pair (kb) and 737-kb regions including the whole APC gene and flanked by a 4-base pair repeat and LINE-1 repetitive sequences, respectively. The chimeric LINE-1 element created at the breakpoint in the latter case also contained a short sequence derived from another LINE-1 element, suggesting a complex unequal homologous recombination event. These findings indicate that this gene dose assay is a useful technique to detect large gene deletions of the APC gene and to determine their genomic breakpoints.

Mutation spectrum of the APC gene in 83 Korean FAP families

Familial adenomatous polyposis (FAP) is a clinically well-defined hereditary disease caused by germline mutations in the adenomatous polyposis coli (APC) gene. FAP is characterized by polyposis in the large bowel and variable extracolonic manifestations. With an increase of reported APC germline mutations, many reports have investigated genotype-phenotype correlations in FAP patients. Here, we analyzed the APC gene for germline mutations in 83 unrelated Korean FAP patients and investigated genotype-phenotype correlations. We identified germline APC mutations in 59 (71%) of the cases, including 34 frameshift mutations, 19 nonsense mutations, and six splice site mutations. Among 59 patients with the identified germline mutation of the APC gene, 37 had been reported previously and were included in the genotype-phenotype analysis. In the other 22 patients, we identified seven novel mutations: c.1438C>T, c.2232_2233dupCT, c.3426delT, c.3739_3769del31, c.3931_3935delATTGG, c.4332dupA, and c.4722_4725delACTA. Desmoid tumors were identified in six of the examined FAP patients, five of whom had APC germline mutations; these mutations involved codons 849, 864, 1309, 1444 and 1464, respectively (c.2547_2548delTA, c.2592_2593insCT, c.3927_3931delAAAGA, c.4332dupA and c.4391-4394delAGAG). Four of the included FAP patients had papillary thyroid cancers; all were female and had germline APC mutations (c.1863_1865delTTAincCT, c.2805C>A, c.3183_3187delACAAA and c.3927_3931delAAAGA).

Cyclooxygenase-2 Expression in FAP Patients Carrying Germ Line MYH Mutations

Familial adenomatous polyposis (FAP) is an autosomal condition caused by inherited mutations in the adenomatous polyposis coli (APC) or in the MYH genes. Clinical trials have established that nonsteroidal anti-inflammatory drugs (NSAID) are effective in preventing the development as well as reducing the size and decreasing the number of adenomas in FAP patients. Our aim was to evaluate the cyclooxygenase-2 (COX-2) expression in surgical specimens from patients with no evidence of germ line APC mutations but carrying germ line MYH mutations. COX-2 expression was evaluated through immunohistochemical and mRNA analysis in carcinomas, adenomas, and healthy mucosa from six patients carrying germ line biallelic MYH mutations. A modulation of COX-2 expression from adenoma (lower level) to carcinoma (higher level) was observed in all patients by both immunohistochemical and mRNA analysis. Moreover, patients with MYH mutations showed a weak COX-2 expression in the whole colorectal mucosa, as for classic FAP patients carrying germ line APC mutations. All together, our data suggest that biallelic MYH patients might benefit from NSAID treatment, because in these patients COX-2 is overexpressed in the whole colorectal mucosa, a finding possibly related to the interplay between COX-2 and APC protein being the APC gene a common target of mutations in MYH patients.