Germline SMAD4 Mutation Research Articles

Molecular and clinicopathological analysis of three cases of gastric juvenile polyposis.

Background and AimJuvenile polyposis (JP) is a rare disease known to be associated with mutations either in SMAD4/BMPR1A. JP is known to often develop into malignant tumors, with a reported probability of 9–50%. However, the mechanisms of its carcinogenesis are not fully understood. We tried to elucidate the mechanisms of malignant transformation underlying this condition in three cases of gastric JP.MethodsWe selected polyps from each patient displaying varying degrees of atypia and their nearby normal polyps and compared them using immunohistochemistry, Sanger sequencing, and loss of heterozygosity (LOH) analysis of SMAD4, BMPR1A, and TP53. ResultsTwo of the three cases were suspected of having germline SMAD4 mutations based on their familial medical histories; the remaining case was found to have a SMAD4 germline mutation following preoperative genetic testing. All three cases were shown to present with both SMAD4 positive and negative areas across each lesion, with the neoplastic lesions tending to show stronger nuclear SMAD4 expression. This expression was closely associated with the SMAD4 LOH status; however, we also noted paradoxical SMAD4 expression in the neoplastic lesions despite the biallelic inactivation of SMAD4 revealed in the genetic evaluation.ConclusionsThese data suggest that strong nuclear expression of SMAD4, even when seemingly paradoxical, seems to be closely associated with dysplastic polyps in JP. Complete inactivation of SMAD4 was not shown to be essential for the development of dysplastic polyps in gastric JP, and other pathways seemed to be involved in the acquisition of the malignant phenotype.

Gastrointestinal: Massive gastric juvenile polyposis.

A 46-year-old man presented with a 3-month history of fatigue and bilateral lower limb edema. His father developed colon cancer at age 30s, and his uncle has a suspected polyp discovery. Laboratory tests revealed iron deficiency anemia, hypoproteinemia, and a positive fecal immunochemical testing for occult blood. Contrast-enhanced computed tomography showed space-occupying lesions in the fundus, lesser curvature, and antrum of the stomach. Esophagogastroduodenoscopy showed massive, papillary polyposis of gastric fundus and body (Fig. 1a). Involvement was limited to the antrum, and one duodenal polypoid lesion was found. Larger polyps ranged from 30 to 40 mm in diameter (Fig. 1b), with spontaneous bleeding of some lesions. Narrow band imaging and indigo carmine dye did not reveal neoplastic micro vessels and microstructures. A few colorectal polyps were easily removed by colonoscopy, which showed features of inflammatory polyps. Enteroscopy demonstrated no bleeding in the small intestine. Piecemeal endoscopic mucosal resection was performed to deal with huge subcardial polyps with severe spontaneous bleeding. Tissue pathology confirmed a diagnosis of hamartomatous polyps without presence of dysplasia (Fig. 1c). Meanwhile, considering the family history of gastrointestinal malignancy, the patient was recommended for possible genetic testing and a heterozygous mutation in SMAD4 gene was identified. The patient exhibited a frameshift mutation in exon 11 (c.1430del:p.G477fs), leading to a premature stop codon. Finally, a diagnosis of juvenile polyposis syndrome (JPS) was proven by pathological and genetic results. Because conservative treatments and endoscopic surveillance failed to correct chronic blood loss and hypoalbuminemia, the patient finally underwent a laparoscopic total gastrectomy (Fig. 1d). The hemoglobin increased from 37 to 107 g/L, and the plasma albumin level increased from 22 to 34 g/L postoperatively. JPS is an autosomal dominant disorder with multiple juvenile polyps in the gastrointestinal tract. Gastric juvenile polyposis is rare and is most commonly associated with germline SMAD4 mutations. Unusual patterns of polyps which could mimic hyperplastic polyps make diagnosis more difficult. Typical pathological findings include the dense stroma and dilated cystic spaces. JPS should be differentiated from other diseases such as Peutz-Jeghers polyposis, Cronkhite-Canada syndrome, Ménétrier disease. Partial or total gastrectomy should be considered when high grade dysplasia occurs or when endoscopic resection may not be possible.

Massive gastric juvenile-type polyposis: a clinicopathological analysis of 22 cases.

Massive gastric polyposis is a rare entity that is often associated with juvenile polyposis syndrome (JPS). The aim of this study was to evaluate the clinicopathological features of 22 patients with abundant gastric juvenile-type or hyperplastic-like polyps. The study included 12 males and 10 females with a median age of 48 years (range: 13-79 years). Fourteen (64%) patients carried a diagnosis of JPS, and three had prior gastrointestinal adenocarcinomas. Patients without known JPS presented at an older median age (60 years versus 40 years; P = 0.0068). Clinical symptoms included nausea, vomiting, and abdominal pain; 23% of patients were asymptomatic. Eighteen cases showed complete or near-complete carpeting of the gastric mucosa by innumerable polyps, ranging from a few millimetres to ~100 mm. Most polyps formed long, bulbous projections and had characteristic histological features, including a smooth outer contour, prominent stromal oedema, and widely spaced, often cystically dilated glands lined by foveolar epithelium; some polyps had less stroma and more hyperplastic foveolar epithelium. All had normal underlying or adjacent mucosa. Four (18%) cases harboured adenocarcinoma, and seven (32%) others showed dysplasia. SMAD4 immunohistochemical staining showed patchy loss in polyps from 19 of 20 cases tested. Five of six (84%) patients tested had a germline SMAD4 mutation. Massive gastric juvenile-type polyposis can occur in patients with and without known JPS, and may mimic different conditions, such as other polyposis syndromes and Ménétrier disease. Pathologists play an important role in disease classification, as some patients lack a family or personal history of JPS, have few if any colonic polyps, and may not harbour diagnostic germline mutations.

SMAD4遺伝子変異が診断に有用であった胃限局型若年性ポリポーシスの1例

症例は42歳の女性で，胃限局型ポリポーシスに対し，前医でCronkhite-Canada症候群を疑われ，ステロイド治療が行われたが奏効せず，内科的コントロール不良の貧血と低蛋白血症を主訴に当院紹介受診した．腹腔鏡補助下胃全摘出術を施行し，症状は改善した．標本肉眼所見にて胃に限局して密生する多発ポリープを認め，病理組織学的検査では過誤腫性ポリープの形態を呈していた．大腸に特異的な病変が存在せず，臨床病理像だけからは鑑別診断に難渋したが，末梢血DNAの遺伝子診断を施行したところ，若年性ポリポーシス（以下，JPsと略記）関連遺伝子であるSMAD4遺伝子変異を認め，胃限局型JPsの最終診断に至った．さらに，本症例は，世界的にも過去に報告のないnovel mutationを有していた．本邦ではJPsにおけるSMAD4遺伝子変異の報告はいまだ少ないが，同遺伝子の変異検索は診断確定に有用であるため，胃限局型ポリポーシスの鑑別診断に際し念頭におく必要がある．

The prevalence of hereditary hemorrhagic telangiectasia in Juvenile Polyposis syndrome patients with SMAD4 mutations

Background Juvenile Polyposis Syndrome (JPS) is defined by the presence of ≥ 5 colorectal juvenile polyps or any number of juvenile polyps in an individual with a family history of JPS. Genetic alterations including either point mutations or large rearrangements in BMPR1A or SMAD4 are found in 50% of affected individuals. Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disease diagnosed upon the presence of epistaxis, visceral arteriovenous malformations (AVM) or mucutaneous telangiectasias. HHT is diagnosed when there are ≥ 3 manifestations and is suspected when there are at least 2 manifestations. Most HHT cases are caused by a germline mutation in ALK1 or ENG ,m embers of the TGFb signaling pathway. Approximately 22% of patients with Juvenile Polyposis Syndrome (JPS) due to a SMAD4 mutation have been reported to also have HHT [1]. Most prior publications have few patients and no systematic approach to screening, so the true incidence of the combined JPS/HHT syndrome is not known. Our aim was to determine the prevalence of HHT in our patients with JPS with a SMAD4 mutation including those who underwent systematic screening for AVM’s. Methods JPS patients were identified from a comprehensive polyposis database using Cologene© software. Families carrying a germline SMAD4 mutation were studied by screening affected patients for cutaneous telangiectases and with cardiac bubble ECHO, CAT scan chest, or MRI of brain for other AVMs. Results

SMAD4 Immunohistochemistry Reflects Genetic Status in Juvenile Polyposis Syndrome

Juvenile polyposis syndrome (JPS) can be caused by a germline defect of the SMAD4 gene. Somatic inactivation of SMAD4 occurs in pancreatic and colorectal cancers and is reflected by loss of SMAD4 immunohistochemistry. Here, SMAD4 immunohistochemistry as a marker of SMAD4 gene status and the role of SMAD4 in the adenoma-carcinoma sequence in neoplastic progression in JPS are studied. Twenty polyps with a SMAD4 germline defect and 38 control polyps were studied by SMAD4 immunohistochemistry. Inactivation of the SMAD4 wild-type allele was studied in dysplastic epithelium and in areas with aberrant SMAD4 expression. APC, beta-catenin, p53, and K-ras were studied to evaluate the adenoma-carcinoma sequence. Nine of 20 polyps with a SMAD4 germline defect showed loss of epithelial SMAD4 expression. Loss of heterozygosity of SMAD4 was found in five polyps and a somatic stop codon mutation was found in two polyps without loss of heterozygosity. Remarkably, somatic inactivation of epithelial SMAD4 did not always coincide with dysplasia and aberrant p53 staining was found in four of six dysplastic polyps with normal SMAD4 staining. One K-ras mutation was found in nine juvenile polyps with dysplasia. No evidence for Wnt activation was found. SMAD4 immunohistochemistry mirrors genetic status and provides a specific adjunct in the molecular diagnosis of JPS. However, epithelial SMAD4 inactivation is not required for polyp formation and is not obligatory for neoplastic progression in JPS. Instead, different routes to neoplasia in JPS caused by germline SMAD4 mutation seem to be operative, including somatic loss of SMAD4 and p53 inactivation without somatic loss of SMAD4.

Juvenile polyps have gastric differentiation with MUC5AC expression and downregulation of CDX2 and SMAD4

CDX2 is a homeobox transcription factor that works as a master gene in intestinal differentiation, both in the colon and in aberrant locations such as intestinal metaplasia (IM) of the stomach. Transgenic mice with Cdx2 expression in the stomach develop IM and Cdx2(+/-) mice develop hamartomatous polyps in the colon presenting gastric differentiation. We previously observed regulation of CDX2 by the BMP/SMAD pathway in the gastric context. Here, we hypothesized that juvenile polyps, which are hamartomatous polyps caused by mutations in members of the BMP/SMAD pathway, might recapitulate the gastric differentiation observed in Cdx2(+/-) mice due to SMAD4 and CDX2 downregulation. We characterized SMAD4 and CDX2 expression in a series of 18 solitary juvenile polyps and 2 polyps from juvenile polyposis (JP) patients, one with a germline SMAD4 mutation and one with a germline BMPRIA mutation, as well as the expression of an intestinal differentiation marker, MUC2 (by immunohistochemistry and in situ hybridization), and gastric differentiation markers, MUC5AC and MUC6 (by immunohistochemistry). We observed that juvenile polyps have a heterogeneous expression of CDX2, MUC2 and SMAD4, with negative areas, and 15 of the 18 solitary polyps and the JP case with SMAD4 mutation exhibit de novo expression of MUC5AC but not MUC6. In conclusion, juvenile polyps have gastric transdifferentiation associated with downregulation of CDX2 and SMAD4, lending support to the role of the BMP/SMAD pathway in CDX2 regulation.

Smad4 haploinsufficiency: a matter of dosage

BackgroundThe inactivation of tumor suppressor genes follows Alfred Knudson's 'two-hit' model: both alleles need to be inactivated by independent mutation events to trigger tumor formation. However, in a minority of tumor suppressor genes a single hit is sufficient to initiate tumorigenesis notwithstanding the presence of the wild-type allele, a condition known as haploinsufficiency. The SMAD4 gene is an intracellular mediator of the TGF-β and BMP signal transduction pathways and a tumor suppressor involved in pancreatic and colorectal tumorigenesis. In Smad4-mutant mouse models, haploinsufficiency characterizes the development of gastrointestinal polyps with initial retention of the wild-type allele and protein expression within the nascent tumors and in their direct microenvironment. Similarly, germline SMAD4 mutations are responsible for a subset of patients affected by juvenile polyposis syndrome, an autosomal dominant intestinal cancer syndrome. To date, the molecular and cellular consequences of SMAD4 haploinsufficiency on TGF-β and BMP signaling and on genome-wide gene expression have not been investigated.ResultsHere we show that, similar to previous observations in Smad4-mutant mouse models, haploinsufficiency characterizes a substantial fraction of the juvenile polyps arising in patients with germline SMAD4 mutations. Also, mouse embryonic and intestinal cells heterozygous for a targeted Smad4 null mutation are characterized by a corresponding 50% reduction of the Smad4 protein levels. Reporter assays revealed that mouse Smad4+/- cells exert intermediate inhibitory effects on both TGF-β and BMP signaling. Genome-wide expression profiling analysis of Smad4+/- and Smad4-/- cells pinpointed a subset of dosage-dependent transcriptional target genes encompassing, among others, members of the TGF-β and Wnt signaling pathways. These SMAD4 dosage-dependent transcriptional changes were confirmed and validated in a subset of target genes in intestinal tissues from juvenile polyposis syndrome patients.ConclusionSmad4 haploinsufficiency is sufficient to significantly inhibit both TGF-β and BMP signal transduction and results in the differential expression of a broad subset of target genes likely to underlie tumor formation both from the mesenchymal and epithelial compartments. The results of our study, performed in normal rather than tumor cells where additional (epi-) genetic alterations may confound the analysis, are relevant for our understanding and elucidation of the initial steps underlying SMAD4-driven intestinal tumorigenesis.

Gastric involvement in juvenile polyposis associated with germline SMAD4 mutations: An entity characterized by a mixed hypertrophic and polypoid gastropathy

Exclusively gastric form of juvenile polyposis associated with germline SMAD4 mutation is a rare clinical entity and is usually difficult to diagnose in the absence of colorectal lesions. We describe the phenotype of two unrelated cases of exclusive or predominant gastric expression of juvenile polyposis. Endoscopically, we found an unusual hypertrophic and polypoid gastropathy with abundant mucus adhering to the mucosal surface. Initially diagnosed as hyperplastic polyps, examination of gastric macrobiopsy specimens and identification of SMAD4 gene mutation in both cases confirmed the diagnosis. Close upper GI surveillance was proposed in case 1 and prophylactic total gastrectomy in the second one. Juvenile polyposis limited to the stomach is a rare condition that is linked to SMAD4 mutations. Such a diagnosis should be considered whenever a mixed, hypertrophic and polypoid gastropathy is encountered.

Gastric juvenile polyposis associated with germline SMAD4 mutation

We treated a 39-year-old woman with hypoproteinemia and anemia who had profuse gastric polyposis. Radiographic and endoscopic examination showed numerous polyps restricted to the stomach. The patient had pulmonary arteriovenous malformations in the left lung. Histological examination of the resected stomach revealed the gastric polyposis to be composed of cystic dilatation of the glands with small areas of adenocarcinoma. These findings were compatible with gastric juvenile polyposis (GJP) accompanied by gastric cancer. Analysis of genomic DNA revealed that the patient had truncating mutation of SMAD4, a responsible gene for juvenile polyposis (JP). Our case suggests that SMAD4 is possibly a responsible gene for GJP.

Germline SMAD4 or BMPR1A mutations and phenotype of juvenile polyposis.

Juvenile polyposis (JP) is an inherited condition predisposing to upper gastrointestinal (UGI) polyps and colorectal cancer. Two genes are known to predispose to JP, SMAD4 and bone morphogenetic protein receptor type 1A (BMPR1A). The object of this study was to determine the differences in phenotype of patients with SMAD4 or BMPR1A mutations (MUT+) compared with those without (MUT-). DNA was extracted from 54 JP probands and used for polymerase chain reaction of all exons of SMAD4 and BMPR1A. Products were then sequenced and analyzed for mutations. Medical record data were used to create a JP database, and statistical analysis was performed using Fisher's exact and unpaired t-tests. Nine of 54 patients had germline SMAD4 mutations, 13 had BMPR1A mutations, and 32 had neither. There were no significant differences between SMAD4+ and BMPR1A+ cases in terms of clinical factors examined, except for a family history of UGI involvement (P <.01). There was a higher prevalence of familial cases in MUT+ patients (P =.09), >10 lower gastrointestinal polyps (P =.06), and frequency of family history of gastrointestinal cancer compared with MUT- patients (P =.01). Patients with germline SMAD4 or BMPR1A mutations have a more prominent JP phenotype than those without, and SMAD4 mutations predispose to UGI polyposis.

Comprehensive Analysis of SMAD4 Mutations and Protein Expression in Juvenile Polyposis : Evidence for a Distinct Genetic Pathway and Polyp Morphology in SMAD4 Mutation Carriers

Juvenile polyposis syndrome (JPS; OMIM 174900) is a rare disorder which is characterized by the presence of hamartomatous polyps throughout the gastrointestinal tract and an increased risk of gastrointestinal malignancy. Mutations of the SMAD4 gene on chromosome 18q21.1 have been shown to cause a subset of JPS cases, with estimates ranging from 20% to >50%. Characterization of the genes that cause the remainder of JPS cases relies on the certainty that SMAD4 is not the causative gene. We have undertaken a comprehensive analysis of germline SMAD4 mutations in a cohort of JPS patients to define the spectrum of mutations that cause JPS. We have analyzed a series of polyps from these patients for SMAD4 protein expression. We have also performed a blinded assessment of polyp material to look for morphological differences between polyps from patients with and without a germline SMAD4 mutation. The results indicate that almost all germline SMAD4 mutations are readily detectable by screening genomic DNA using polymerase chain reaction-based methods; SMAD4 can be excluded as the causative gene in the majority of our JPS cohort. Loss of SMAD4 expression occurs in most polyps from SMAD4 mutation carriers, even those with missense germline mutations. SMAD4 loss in polyps is, however, not a feature of cases that are not caused by SMAD4 mutations, indicating that these polyps develop along a SMAD4-independent pathway. The morphology of polyps from SMAD4 mutation carriers is subtly different from other JPS polyps, notably including a more prominent epithelial component in the former.

Direct genetic testing for Smad4 mutations in patients at risk for juvenile polyposis

Background: The identification of germline mutations in juvenile polyposis (JP) families has made presymptomatic genetic testing possible. In this study we report the results of genetic testing in two large JP families and develop an algorithm for the clinical management of these patients. Methods: DNA was extracted from 55 members of 2 JP kindreds, and the Smad4 mutations in the germline were determined by direct sequencing. All family members were then tested for mutations with use of single-strand conformational polymorphism analysis and were invited for genetic counseling. Results: All 18 affected members of both kindreds had a 4-bp deletion in exon 9 of the Smad4 gene. In 30 patients at risk for JP, 17 had previously had negative endoscopic screening results and 13 had never been screened. Five patients at risk had inherited germline Smad4 mutations. Two carriers have had hematochezia but have not been screened, whereas 3 were asymptomatic. The mean age of carriers was 29.8 years (range 9.1-49.5 years), whereas that of noncarriers was 41.0 years (range 8.1-76.5 years). Conclusions: Compliance has been a problem with endoscopic screening for JP. With genetic testing noncarriers may no longer require frequent screening endoscopy, whereas gene carriers can be targeted for close endoscopic surveillance and early intervention to prevent the development of gastrointestinal cancers. Direct genetic testing significantly improves the presymptomatic diagnosis of gene carriers in JP families with Smad4 mutations. (Surgery 1999;126:162-70.)

Direct genetic testing for mutations in patients at risk for juvenile polyposis

<h2>Abstract</h2> <b>Background:</b> The identification of germline mutations in juvenile polyposis (JP) families has made presymptomatic genetic testing possible. In this study we report the results of genetic testing in two large JP families and develop an algorithm for the clinical management of these patients. <b>Methods:</b> DNA was extracted from 55 members of 2 JP kindreds, and the Smad4 mutations in the germline were determined by direct sequencing. All family members were then tested for mutations with use of single-strand conformational polymorphism analysis and were invited for genetic counseling. <b>Results:</b> All 18 affected members of both kindreds had a 4-bp deletion in exon 9 of the Smad4 gene. In 30 patients at risk for JP, 17 had previously had negative endoscopic screening results and 13 had never been screened. Five patients at risk had inherited germline Smad4 mutations. Two carriers have had hematochezia but have not been screened, whereas 3 were asymptomatic. The mean age of carriers was 29.8 years (range 9.1-49.5 years), whereas that of noncarriers was 41.0 years (range 8.1-76.5 years). <b>Conclusions:</b> Compliance has been a problem with endoscopic screening for JP. With genetic testing noncarriers may no longer require frequent screening endoscopy, whereas gene carriers can be targeted for close endoscopic surveillance and early intervention to prevent the development of gastrointestinal cancers. Direct genetic testing significantly improves the presymptomatic diagnosis of gene carriers in JP families with Smad4 mutations. (Surgery 1999;126:162-70.)