Biomedical subjects

Heather Hampel

Publications and source records attributed to Heather Hampel.

At least 19 recordsLinked to original sources

PubMed2026

Recommendations for return of secondary genomic findings in observational cohort studies.

The return of secondary genomic findings (ROSF) to participants in observational cohort studies has evolved from a topic of debate to an accepted standard. This Perspective synthesizes the proceedings of a 2024 National Heart, Lung and Blood Institute-sponsored workshop and the broader literature to provide updated guidance for ROSF. Building on the 2010 National Heart, Lung and Blood Institute Working Group recommendations and the 2014 Clinical Sequencing Exploratory Research/Electronic Medical Records and Genomics 'floor and ceiling' framework, we address four areas: an integrated ethical framework for observational cohort settings; the emerging challenge of returning novel result types beyond monogenic variants, including polygenic risk scores, somatic mosaicism and pharmacogenomic findings; health equity and community engagement as structural prerequisites for ethical ROSF; and scalability challenges, including technology-assisted disclosure. Drawing on implementation experience from large-scale sequencing programs, we offer recommendations that balance researcher obligations with participant autonomy and equitable access to the benefits of genomic research.

Journal Article↗

PubMed2026

Bayesian Integration of Tumor Mutational Signatures and Somatic Features Refines Pathogenicity Assessment of Germline Mismatch Repair Variants.

Variants of uncertain significance (VUS) in mismatch repair (MMR) genes represent a persistent bottleneck in germline interpretation for Lynch syndrome, creating a critical opportunity to leverage tumor biology to refine pathogenicity assessment. Although tumor features such as microsatellite instability (MSI) and immunohistochemistry (IHC) are routinely evaluated, they are typically interpreted separately from germline classification, and their quantitative contribution within ACMG/AMP frameworks remains poorly defined. We therefore analyzed paired germline and tumor sequencing data from 1110 tumors across 1073 patients with colorectal or endometrial cancer to determine whether mismatch repair-deficient (MMR-d) mutational signatures can be quantitatively integrated into Bayesian germline variant interpretation. Using COSMIC single-base substitution signatures, tumors were classified as MMR-d or MMR proficient, and an empirically derived likelihood ratio (LR) quantified the association between MMR-d signatures and pathogenic germline MMR variants. The presence of an MMR-d signature increased the likelihood of an underlying pathogenic germline MMR variant approximately eightfold (LR ≈ 8; log10 LR ≈ 0.90), whereas its absence provided moderate-to-strong benign evidence (LR ≈ 0.156; log10 LR ≈ -0.81). Applying this integrative framework to 45 germline MMR VUS, joint modeling of tumor mutational signatures with additional somatic and variant-level evidence resulted in clinically significant reclassification of 38 (84.4%) variants, including three reclassified as pathogenic or likely pathogenic and 35 as likely benign. A total of 16 downgraded variants were independently downgraded by Invitae. These findings demonstrate that tumor mutational signatures can be formally incorporated into Bayesian germline interpretation, transforming tumor data into quantitative pathogenicity evidence and offering a principled strategy to reduce VUS burden in hereditary cancer genetics.

Humans↗

PubMed2006

Pathogenicity of MSH2 missense mutations is typically associated with impaired repair capability of the mutated protein.

BACKGROUND & AIMS: Inherited deleterious mutations in mismatch repair genes MLH1, MSH2, and MSH6 predispose to hereditary nonpolyposis colorectal cancer. A major diagnostic challenge is the difficulty in evaluating the pathogenicity of missense mutations. Previously we showed that most missense variants in MSH6 do not impair MMR capability and are associated with no or low cancer susceptibility, whereas in MLH1, functional studies distinguished nontruncating mutations with severe defects from those not or slightly impaired in protein expression or function. The present study was undertaken to evaluate the pathogenicity of inherited missense mutations in MSH2. METHODS: Fifteen mutated MSH2 proteins including 14 amino acid substitutions and one in-frame deletion were tested for expression/stability, MSH2/MSH6 interaction, and repair efficiency. The genetic and biochemical data were correlated with the clinical data. Comparative sequence analysis was performed to assess the value of sequence homology as a tool for predicting functional results. RESULTS: None of the studied MSH2 mutations destroyed the protein or abolished MSH2/MSH6 interaction, whereas 12 mutations impaired the repair capability of the protein. Comparative sequence analysis correctly predicted functional studies for 13 of 14 amino acid substitutions. CONCLUSIONS: Interpretation was pathogenic for 12, nonpathogenic for 2, and contradictory for 1 mutation. The pathogenicity could not be distinguished unambiguously by phenotypic characteristics, although correlation between the absence of staining for MSH2 and pathogenicity of the missense mutation was notable. Unlike in MSH6 and MLH1, the pathogenicity of missense mutations in MSH2 was always associated with impaired repair capability of the mutated protein.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Screening for Lynch syndrome (hereditary nonpolyposis colorectal cancer) among endometrial cancer patients.

Endometrial cancer is the most common cancer in women with Lynch syndrome. The identification of individuals with Lynch syndrome is desirable because they can benefit from increased cancer surveillance. The purpose of this study was to determine the feasibility and desirability of molecular screening for Lynch syndrome in all endometrial cancer patients. Unselected endometrial cancer patients (N = 543) were studied. All tumors underwent microsatellite instability (MSI) testing. Patients with MSI-positive tumors underwent testing for germ line mutations in MLH1, MSH2, MSH6, and PMS2. Of 543 tumors studied, 118 (21.7%) were MSI positive (98 of 118 MSI high and 20 of 118 MSI low). All 118 patients with MSI-positive tumors had mutation testing, and nine of them had deleterious germ line mutations (one MLH1, three MSH2, and five MSH6). In addition, one case with an MSI-negative tumor had abnormal MSH6 immunohistochemical staining and was subsequently found to have a mutation in MSH6. Immunohistochemical staining was consistent with the mutation result in all seven truncating mutation-positive cases but was not consistent in two of the three missense mutation cases. We conclude that in central Ohio, at least 1.8% (95% confidence interval, 0.9-3.5%) of newly diagnosed endometrial cancer patients had Lynch syndrome. Seven of the 10 Lynch syndrome patients did not meet any published criteria for hereditary nonpolyposis colorectal cancer, and six of them were diagnosed at age >50. Studying all endometrial cancer patients for Lynch syndrome using a combination of MSI and immunohistochemistry for molecular prescreening followed by gene sequencing and deletion analysis is feasible and may be desirable.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Histologic features distinguish microsatellite-high from microsatellite-low and microsatellite-stable colorectal carcinomas, but do not differentiate germline mutations from methylation of the MLH1 promoter.

The detection of microsatellite-unstable (microsatellite instability [MSI]) colorectal carcinomas (CRCs) has prognostic value and can help screen for Lynch syndrome. We determined which histologic features are associated with MSI status and presence of germline mutation and/or methylation of MLH1 promoter. Patients diagnosed with CRC were offered participation in the Columbus-area hereditary nonpolyposis colorectal cancer syndrome study regardless of age or family history. Tumors were evaluated for MSI using a modified Bethesda panel of microsatellite markers. Methylation status of the MLH1 promoter was evaluated by methylation-specific polymerase chain reaction and bisulfite PCR followed by restriction digestion of tumor DNA. All patients with microsatellite-unstable tumors underwent mutation analysis of the MLH1, MSH2, and MSH6 genes by full sequencing of genomic DNA and by multiplex ligation probe assay of MLH1 and MSH2. Histologic end points were tumor type, grade, percentage of mucin, border, and lymphoid host response. Of the 482 CRCs, 87 were MSI with 69 MSI high (MSI-H), 18 MSI low (MSI-L), and 395 microsatellite stable (MSS). Of 87 MSI tumors, 12 had germline mutations and 34 had methylation of the MLH1 promoter. Younger age, but not histologic features, was significantly associated with a germline mutation. Percentage of mucin, histologic type, grade, and lymphoid host response differed significantly between MSI-H when compared with MSI-L or MSS. No difference was found between MSI-L versus MSS. Histologic features are associated with MSI-H CRC and are helpful to differentiate MSI-H from MSI-L and MSS. These features are not useful to distinguish MSI-L from MSS carcinomas, and those with a deleterious germline hereditary nonpolyposis colorectal cancer syndrome mutation from those with methylation of the MLH1 promoter region.

Adaptor Proteins, Signal Transducing↗

PubMed2006

American founder mutation for Lynch syndrome. Prevalence estimates and implications.

BACKGROUND: Recently, a new founder mutation, an exon 1-6 deletion in a mismatch repair gene (MMR), MSH2, in nine kindreds with Lynch syndrome was reported. In 3 of the kindreds this mutation was traced by genealogy through 11-12 generations to a common founder, and thus termed the American Founder Mutation (AFM). Since then, 13 additional 'unrelated' kindreds with AFM were detected by a recently designed single polymerase chain reaction. This test might serve as first-line screening for Lynch syndrome mutations, provided AFM was prevalent, which is assessed in the current study. METHODS: The number of current AFM carriers and the incidence of Lynch syndrome caused by AFM were estimated based on population growth of mutation carriers derived from genealogy data. For cross-checking, its annual incidence was also estimated based on published epidemiology data. RESULTS: There are 18,981 (5th and 95th percentiles, 6038 and 34,466, respectively) expected current AFM carriers, or 160 (range 51-290) Lynch syndrome cases diagnosed per year due to AFM estimated based on genealogy data. The incidence estimate closely overlaps with that based on published epidemiology data, which is 114-400 cases per year. CONCLUSIONS: A large number of AFM carriers are likely to exist in the U.S., which harbors significant implications for cancer control. Given the ease of detection, testing for AFM not only among members of the existing AFM families, but also among all patients with Lynch syndrome in the U.S. is proposed.

Colorectal Neoplasms, Hereditary Nonpolyposis↗

PubMed2006

Long-range PCR facilitates the identification of PMS2-specific mutations.

Mutations within the DNA mismatch repair gene, "postmeiotic segregation increased 2" (PMS2), have been associated with a predisposition to hereditary nonpolyposis colorectal cancer (HNPCC; Lynch syndrome). The presence of a large family of highly homologous PMS2 pseudogenes has made previous attempts to sequence PMS2 very difficult. Here, we describe a novel method that utilizes long-range PCR as a way to preferentially amplify PMS2 and not the pseudogenes. A second, exon-specific, amplification from diluted long-range products enables us to obtain a clean sequence that shows no evidence of pseudogene contamination. This method has been used to screen a cohort of patients whose tumors were negative for the PMS2 protein by immunohistochemistry and had not shown any mutations within the MLH1 gene. Sequencing of the PMS2 gene from 30 colorectal and 11 endometrial cancer patients identified 10 novel sequence changes as well as 17 sequence changes that had previously been identified. In total, putative pathologic mutations were detected in 11 of the 41 families. Among these were five novel mutations, c.705+1G>T, c.736_741del6ins11, c.862_863del, c.1688G>T, and c.2007-1G>A. We conclude that PMS2 mutation detection in selected Lynch syndrome and Lynch syndrome-like patients is both feasible and desirable.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Improved survival with an intact DNA mismatch repair system in endometrial cancer.

OBJECTIVE: To correlate survival and surgical-pathologic factors with DNA mismatch repair status in patients with endometrial cancer. METHODS: Specimens from 336 patients with endometrial cancer were used to create a tissue microarray. Immunohistochemistry with antibodies against the mismatch repair genes MLH1, MSH2, MSH6, and PMS2 were used to stain the tissue microarray. Clinical, pathologic, and survival data were collected and correlated with the immunohistochemistry results. RESULTS: Mismatch repair deficiency was seen in 29% (84 of 294) of cases. Correlation was noted between lack of expression of MLH1 and an increased risk for lymphvascular space involvement (32% versus 21%, P=.05) and cervical involvement (26% versus 14%, P=.02). Lack of expression of either MLH1 or MSH2 was associated with thinner patients (85% had a body mass index less than 40 versus 73% of patients with normal expression, P=.02), as well as with the absence of a history of previous primary malignancy (0 verus 13 cases [4%], P=.023). The estimated disease-free survival is 88%; despite a small number of recurrences, there was a nonsignificant improvement in disease-free survival in tumors with an intact mismatch repair system (P=.1). Significantly improved disease-free survival was seen in patients with normal MLH1 and MSH2 expression compared with those with abnormal expression (92% versus 81%, P=.035). CONCLUSION: Defects in DNA mismatch repair in endometrial cancer is correlated with negative prognostic factors and worse progression-free survival (without a difference in overall survival) compared with tumors with an intact mismatch repair system. LEVEL OF EVIDENCE: II-3.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Somatic acquisition and signaling of TGFBR1*6A in cancer.

CONTEXT: TGFBR1*6A is a common polymorphism of the type I transforming growth factor beta receptor (TGFBR1). Epidemiological studies suggest that TGFBR1*6A may act as a tumor susceptibility allele. How TGFBR1*6A contributes to cancer development is largely unknown. OBJECTIVES: To determine whether TGFBR1*6A is somatically acquired by primary tumors and metastases during cancer development and whether the 3-amino acid deletion that differentiates TGFBR1*6A from TGFBR1 is part of the mature receptor or part of the signal sequence and to investigate TGFBR1*6A signaling in cancer cells. DESIGN, SETTING, AND PATIENTS: Tumor and germline tissues from 531 patients with a diagnosis of head and neck, colorectal, or breast cancer recruited from 3 centers in the United States and from 1 center in Spain from June 1, 1994, through June 30, 2004. In vitro translation assays, MCF-7 breast cancer cells stably transfected with TGFBR1*6A, TGFBR1, or the vector alone, DLD-1 colorectal cancer cells that endogenously carry TGFBR1*6A, and SW48 colorectal cancer cells that do not carry TGFBR1*6A. MAIN OUTCOME MEASURES: TGFBR1*6A somatic acquisition in cancer. Determination of the amino terminus of the mature TGFBR1*6A and TGFBR1 receptors. Determination of TGF-beta-dependent cell proliferation. RESULTS: TGFBR1*6A was somatically acquired in 13 of 44 (29.5%) colorectal cancer metastases, in 4 of 157 (2.5%) of colorectal tumors, in 4 of 226 (1.8%) head and neck primary tumors, and in none of the 104 patients with breast cancer. TGFBR1*6A somatic acquisition is not associated with loss of heterozygosity, microsatellite instability, or a mutator phenotype. The signal sequences of TGFBR1 and TGFBR1*6A are cleaved at the same site resulting in identical mature receptors. TGFBR1*6A may switch TGF-beta growth inhibitory signals into growth stimulatory signals in MCF-7 breast cancer cells and in DLD-1 colorectal cancer cells. CONCLUSIONS: TGFBR1*6A is somatically acquired in 29.5% of liver metastases from colorectal cancer and may bestow cancer cells with a growth advantage in the presence of TGF-beta. The functional consequences of this conversion appear to be mediated by the TGFBR1*6A signal sequence rather than by the mature receptor. The results highlight a new facet of TGF-beta signaling in cancer and suggest that TGFBR1*6A may represent a potential therapeutic target in cancer.

Activin Receptors, Type I↗

PubMed2005

Screening for the Lynch syndrome (hereditary nonpolyposis colorectal cancer).

BACKGROUND: Germ-line mutations in the mismatch-repair genes MLH1, MSH2, MSH6, and PMS2 lead to the development of the Lynch syndrome (hereditary nonpolyposis colorectal cancer), conferring a strong susceptibility to cancer. We assessed the frequency of such mutations in patients with colorectal cancer and examined strategies for molecular screening to identify patients with the syndrome. METHODS: Patients with a new diagnosis of colorectal adenocarcinoma at the major hospitals in metropolitan Columbus, Ohio, were eligible for the study. Genotyping of the tumor for microsatellite instability was the primary screening method. Among patients whose screening results were positive for microsatellite instability, we searched for germ-line mutations in the MLH1, MSH2, MSH6, and PMS2 genes with the use of immunohistochemical staining for mismatch-repair proteins, genomic sequencing, and deletion studies. Family members of carriers of the mutations were counseled, and those found to be at risk were offered mutation testing. RESULTS: Of 1066 patients enrolled in the study, 208 (19.5 percent) had microsatellite instability, and 23 of these patients had a mutation causing the Lynch syndrome (2.2 percent). Among the 23 probands with the Lynch syndrome, 10 were more than 50 years of age and 5 did not meet the Amsterdam criteria or the Bethesda guidelines for the diagnosis of hereditary nonpolyposis colorectal cancer (including the use of age and family history to identify patients at high risk for the Lynch syndrome). Genotyping for microsatellite instability alone and immunohistochemical analysis alone each failed to identify two probands. In the families of 21 of the probands, 117 persons at risk were tested, and of these, 52 had Lynch syndrome mutations and 65 did not. CONCLUSIONS: Routine molecular screening of patients with colorectal adenocarcinoma for the Lynch syndrome identified mutations in patients and their family members that otherwise would not have been detected. These data suggest that the effectiveness of screening with immunohistochemical analysis of the mismatch-repair proteins would be similar to that of the more complex strategy of genotyping for microsatellite instability.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Cancer risk in hereditary nonpolyposis colorectal cancer syndrome: later age of onset.

BACKGROUND & AIMS: Mutations in the mismatch repair genes cause hereditary nonpolyposis colorectal cancer (HNPCC) syndrome and convey high lifetime cancer risks for colorectal (CRC) and endometrial cancer. Currently, cancer risks for individuals with HNPCC are based on data from clinically ascertained families. The purpose of this study was to re-examine the penetrance in HNPCC using a comprehensive dataset from a geographically defined region. METHODS: A combined dataset of 70 HNPCC families ascertained by traditional high-risk criteria and by molecular screening comprising 88 probands and 373 mutation-positive family members was used. Statistical methods were modified survival analysis techniques. RESULTS: In mutation-positive relatives (excluding probands), the median age at diagnosis of CRC was 61.2 years (confidence interval [CI], 56.3-68.0 y). The lifetime risk for CRC was 68.7% (CI, 58.6%-78.9%) for men and 52.2% (CI, 37.6%-66.9%) for women. Considering only probands, the median age at diagnosis of CRC was 44.0 years (CI, 41.0-46.3 y). Median age of onset of EC was 62.0 years (CI, 55.9 y to an upper limit too high to calculate) with a lifetime cancer risk of 54% (CI, 41.9%-66.1%). CONCLUSIONS: A markedly later age of onset for CRC at 61 y than previously reported (approximately 44 y) is suggested, resulting mainly from a more rigorous method of analysis in which all gene-positive individuals (both affected and unaffected with cancer) are considered. Lifetime cancer risks may be lower for CRC and endometrial cancer than presently assumed. If confirmed, these data suggest a need to alter counseling practices, and to consider HNPCC in older individuals than before.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Functional significance and clinical phenotype of nontruncating mismatch repair variants of MLH1.

BACKGROUND & AIMS: Germline mutations in mismatch repair genes are associated with hereditary nonpolyposis colorectal cancer. A significant proportion of mutations are nontruncating and associated with a variability of clinical phenotype and microsatellite instability and with occasional presence of residual protein in tumor tissue that suggests impaired functional activity but not total lack of mismatch repair. To address pathogenic significance and mechanism of pathogenicity, we studied the functionality of 31 nontruncating MLH1 mutations found in clinically characterized colorectal cancer families and 3 other variations listed in a mutation database. METHODS: Mutations constructed by site-directed mutagenesis were studied for protein expression/stability, subcellular localization, protein-protein interaction, and repair efficiency. The genetic and biochemical data were correlated with clinical data. Finally, comparative sequence analysis was performed to assess the value of sequence homology as a tool for predicting functional results. RESULTS: Altogether, 22 mutations were pathogenic in more than one assay, 2 variants were impaired in one assay, and 10 variants acted like wild-type protein. Twenty of 34 mutations affected the quantity of MLH1 protein, whereas only 15 mainly amino-terminal mutations were defective in an in vitro repair assay. Comparative sequence analysis correctly predicted functional studies for 82% of variants. CONCLUSIONS: Pathogenic nontruncating alterations in MLH1 may interfere with different biochemical mechanisms but generally more than one. The severe biochemical defects are mirrored by phenotypic characteristics such as early age at onset and high microsatellite instability, whereas variants with no or mild defects in functionality are associated with variable clinical phenotypes.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Mismatch repair gene PMS2: disease-causing germline mutations are frequent in patients whose tumors stain negative for PMS2 protein, but paralogous genes obscure mutation detection and interpretation.

The MutLalpha heterodimer formed by mismatch repair (MMR) proteins MLH1 and PMS2 is a major component of the MMR complex, yet mutations in the PMS2 gene are rare in the etiology of hereditary nonpolyposis colorectal cancer. Evidence from five published cases suggested that contrary to the Knudson principle, PMS2 mutations cause hereditary nonpolyposis colorectal cancer or Turcot syndrome only when they are biallelic in the germline or abnormally expressed. As candidates for PMS2 mutations, we selected seven patients whose colon tumors stained negative for PMS2 and positive for MLH1 by immunohistochemistry. After conversion to haploidy, truncating germline mutations of PMS2 were found in two patients (2192delTAACT and deletion of exon 8). These mutations abrogated PMS2 protein in germline cells by Western analysis. In two additional patients, PMS2 protein from one allele also was abrogated. Novel or previously described missense variants of PMS2 were detected, but their pathogenicity is undetermined. We detected and characterized a new transcript, PMS2CL, showing 98% sequence identity with exons 9 and 11-15 of PMS2 and emanating from a locus close to PMS2 in chromosome 7p. Its predicted protein product was not detected. Thus, in addition to several previously described PMS2-related genes resembling the 5' end of PMS2, at least one related gene resembles the 3' end of PMS2. In conclusion, both detectable and presently undefined germline mutations are deleterious and produce susceptibility to cancer by the two-hit mechanism. Paralogous genes interfere with mutation detection, resulting in underdiagnosis of PMS2 mutations. Mutation detection in PMS2 requires haploid DNA.

Adaptor Proteins, Signal Transducing↗

PubMed2004

A founder mutation of the MSH2 gene and hereditary nonpolyposis colorectal cancer in the United States.

CONTEXT: Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is caused by mutations in the mismatch repair genes and confers an extraordinarily high risk of colorectal, endometrial, and other cancers. However, while carriers of these mutations should be identified, counseled, and offered clinical surveillance, at present the mutations are not tested for in mutation analyses. OBJECTIVE: To describe the prevalence of a large genomic deletion encompassing exons 1 to 6 of the MSH2 gene that is widespread in the US population as a result of a founder effect. DESIGN, SETTING, AND PATIENTS: Ongoing genealogical and historical study conducted to assess the origin and spread of an MSH2 mutation previously identified in 9 apparently unrelated families with putative HNPCC and living in widely different geographic locations in the United States. MAIN OUTCOME MEASURES: Classification of family members as carriers or noncarriers of the MSH2 mutation; spread of the mutation across the continental United States. RESULTS: To date, 566 family members of the 9 probands have been identified to be at risk and counseled; 137 of these have been tested, and 61 carry the founder mutation. Three families have been genealogically shown to descend from a German immigrant family that arrived and first settled in Pennsylvania in the early 1700s. Movements of branches of the family from Pennsylvania through North Carolina, Alabama, Kentucky, Missouri, Iowa, Nebraska, Utah, Texas, and California have been documented, and carriers of the mutation have already been diagnosed in 14 states. In contrast, the deletion was not found among 407 European and Australian families with HNPCC. CONCLUSION: The postulated high frequency and continent-wide geographic distribution of a cancer-predisposing founder mutation of the MSH2 gene in a large, outbred (as opposed to genetically isolated) population, and the ease with which the mutation can be detected, suggest that the routine testing of individuals at risk for HNPCC in the United States should include an assay for this mutation until more is learned about its occurrence.

Colorectal Neoplasms, Hereditary Nonpolyposis↗

PubMed2004

Lynch Syndrome

CLINICAL CHARACTERISTICS: Lynch syndrome is characterized by an increased risk for colorectal cancer (CRC) and cancers of the endometrium, ovary, stomach, small bowel, urinary tract, biliary tract, prostate, brain (usually glioblastoma), skin (sebaceous adenomas, sebaceous epithelioma, sebaceous carcinomas, and keratoacanthomas), and pancreas. Cancer risks and age of onset vary depending on the associated gene. Several other cancer types have been reported to occur in individuals with Lynch syndrome (e.g., sarcomas, adrenocortical carcinoma). However, the data are not sufficient to demonstrate that the risk of developing these cancers is increased in individuals with Lynch syndrome. DIAGNOSIS/TESTING: The diagnosis of Lynch syndrome is established in a proband with a germline heterozygous pathogenic variant in MLH1, MSH2, MSH6, or PMS2 or a 3' EPCAM deletion identified by molecular genetic testing, or, rarely, constitutional inactivation of the MLH1 promotor due to methylation identified by DNA methylation analysis. MANAGEMENT: Treatment of manifestations: Polypectomy at the time of colonoscopy; referral to advanced endoscopist for lesions requiring advanced resection techniques; surgical resection of polyps when needed; individualized surgical management for colon cancer based on tumor location, stage, Lynch syndrome-associated gene, age, comorbidity, bowel function, anticipated quality of life, and risk of metachronous CRC; mismatch repair (MMR) testing, microsatellite instability (MSI) testing, and multidisciplinary evaluation for rectal cancer prior to treatment; consider immune checkpoint inhibitor therapy for metastatic or unresectable MMR-deficient or MSI-high tumors; other tumors are managed as in the general population. Prevention of primary manifestations: Risk-reducing hysterectomy with bilateral salpingo-oophorectomy can be considered after childbearing is completed. Prophylactic colectomy prior to the development of colon cancer is generally not recommended for individuals known to have Lynch syndrome because screening colonoscopy with polypectomy is an effective preventive measure. Aspirin therapy has been shown to decrease the risk for CRC in individuals with Lynch syndrome. Surveillance: Colonoscopy with removal of precancerous polyps with frequency and initial screening based on gene involved and family history; annual education for females regarding the symptoms of endometrial and ovarian cancers; consider transvaginal ultrasound examination and endometrial biopsy every one to two years beginning at age 30 to 35 years; consider upper endoscopy examination particularly for individuals with a family history of gastric cancer and those of Asian ancestry with frequency and initial screening based on gene involved and family history; biopsies should be evaluated for H pylori infections so that appropriate treatment can be given as needed; consider capsule endoscopy and small bowel enterography for distal small bowel cancers in symptomatic persons; consider urinalysis with urine cytology annually beginning between ages 30 and 35 years; consider pancreatic cancer screening in individuals with a family history of pancreatic cancer; follow population screening guidelines and maintain awareness for signs and symptoms of other cancers. Agents/circumstances to avoid: Obesity, physical inactivity, cigarette smoking, alcohol consumption, and type 2 diabetes may increase CRC risk in individuals with Lynch syndrome. Evaluation of relatives at risk: Molecular genetic testing for the familial Lynch syndrome-related pathogenic variant is recommended for all first-degree relatives (parents, sibs, and offspring) of an affected individual in order to identify as early as possible those who would benefit from surveillance, risk-reducing interventions, and other preventive measures. Testing for constitutional MLH1 hypermethylation is recommended for all first-degree relatives of individuals with Lynch syndrome caused by constitutional MLH1 methylation. GENETIC COUNSELING: Lynch syndrome caused by a heterozygous germline Lynch syndrome-related pathogenic variant (i.e., a pathogenic variant in MLH1, MSH2, MSH6, or PMS2 or a 3' EPCAM deletion) is inherited in an autosomal dominant manner. Individuals with Lynch syndrome caused by constitutional inactivation of MLH1 by methylation typically represent simplex cases, although affected individuals from a few families have been reported with inherited MLH1 promoter methylation. The majority of individuals with a heterozygous germline Lynch syndrome-related pathogenic variant inherited the pathogenic variant from a parent who may or may not have had cancer. Each child of an individual with Lynch syndrome has a 50% chance of inheriting the Lynch syndrome-related pathogenic variant and the related cancer risks. If the reproductive partner of an individual with Lynch syndrome has a germline heterozygous pathogenic variant in the same Lynch syndrome-related gene, offspring are at risk of inheriting biallelic pathogenic variants and having constitutional mismatch repair deficiency. Once a germline Lynch syndrome-related pathogenic variant has been identified in an affected family member, predictive testing for at-risk asymptomatic family members and prenatal/preimplantation genetic testing are possible.

Hereditary Non-Polyposis Colorectal Cancer (HNPCC)↗

PubMed2003

Germline PTEN promoter mutations and deletions in Cowden/Bannayan-Riley-Ruvalcaba syndrome result in aberrant PTEN protein and dysregulation of the phosphoinositol-3-kinase/Akt pathway.

Germline intragenic mutations in PTEN are associated with 80% of patients with Cowden syndrome (CS) and 60% of patients with Bannayan-Riley-Ruvalcaba syndrome (BRRS). The underlying genetic causes remain to be determined in a considerable proportion of classic CS and BRRS without a polymerase chain reaction (PCR)-detectable PTEN mutation. We hypothesized that gross gene deletions and mutations in the PTEN promoter might alternatively account for a subset of apparently mutation-negative patients with CS and BRRS. Using real time and multiplex PCR techniques, we identified three germline hemizygous PTEN deletions in 122 apparently mutation-negative patients with classic CS (N=95) or BRRS (N=27). Fine mapping suggested that one deletion encompassed the whole gene and the other two included exon 1 and encompassed exons 1-5 of PTEN, respectively. Two patients with the deletion were diagnosed with BRRS, and one patient with the deletion was diagnosed with BRRS/CS overlap (features of both). Thus 3 (11%) of 27 patients with BRRS or BRRS/CS-overlap had PTEN deletions. Analysis of the PTEN promoter revealed nine cases (7.4%) harboring heterozygous germline mutations. All nine had classic CS, representing almost 10% of all subjects with CS. Eight had breast cancers and/or benign breast tumors but, otherwise, oligo-organ involvement. PTEN protein analysis, from one deletion-positive and five PTEN-promoter-mutation-positive samples, revealed a 50% reduction in protein and multiple bands of immunoreactive protein, respectively. In contrast, control samples showed only the expected band. Further, an elevated level of phosphorylated Akt was detected in the five promoter-mutation-positive samples, compared with controls, indicating an absence of or marked reduction in functional PTEN. These data suggest that patients with BRRS and CS without PCR-detected intragenic PTEN mutations be offered clinical deletion analysis and promoter-mutation analysis, respectively.

Base Sequence↗

PubMed2003

Identification and characterization of genomic rearrangements of MSH2 and MLH1 in Lynch syndrome (HNPCC) by novel techniques.

It has recently been suggested that large genomic rearrangements account for 10-20% of all MSH2 mutations, and a lower proportion of all MLH1 mutations, among individuals with Lynch syndrome (hereditary non-polyposis colorectal cancer, HNPCC). These rearrangements are notoriously difficult to detect; moreover, for clinical purposes, simple tests must be devised to screen family members at risk. Here we used the multiplex ligation-dependent probe amplification (MLPA) method to screen for MSH2 and MLH1 deletions in 70 patients whose colorectal or endometrial tumors were MSI positive, yet no mutation had been found by genomic exon-by-exon sequencing of MSH2, MLH1, and MSH6. We identified five candidates with four different MSH2 deletions (exons 1-2, exons 1-6, exons 1-7 and exon 8) and one candidate with an MLH1 deletion (exons 3-6). To confirm the screening results and to characterize the breakpoints of these genomic deletions precisely, we used diploid-to-haploid conversion and inverse PCR as well as long-range PCR. In each case, we were able to pinpoint the breakpoint and design a simple diagnostic PCR. The procedures we used appear to be sensitive, specific, and simple enough for clinical use.

Adaptor Proteins, Signal Transducing↗

PubMed2003

GI polyposis and glycogenic acanthosis of the esophagus associated with PTEN mutation positive Cowden syndrome in the absence of cutaneous manifestations.

A 62-yr-old man was referred for management of GI polyposis. Large bowel polyps were initially diagnosed >25 yr ago, and the patient had undergone multiple colonoscopies and polypectomies. Personal and family history were notable for thyroid goiter and hypothyroidism. Physical examination was notable for lingular papillomatosis. No cutaneous lesions were seen. Upper endoscopy revealed esophageal glycogen acanthosis. There were multiple polyps throughout the stomach and the small and large intestines. Histology of these polyps showed multiple cell types including juvenile polyps, inflammatory polyps with fibromuscular proliferation and lamina propria ganglion cells, and focal adenomatous change. A clinical diagnosis of Cowden syndrome was made. Mutation analysis revealed a variant in exon 8 of the PTEN gene. Direct sequencing revealed a germline heterozygous C.892-895InsA, which is predicted to result in a truncated PTEN protein. Cowden syndrome is an underdiagnosed, underrecognized, autosomal dominant, inherited syndrome. For the gastroenterologist, esophageal acanthosis and multiple hamartomatous polyps should suggest the diagnosis. Sensitive molecular diagnostic tests looking for mutations in the appropriate genes are clinically available. Together with genetic counseling, molecular diagnostic testing will allow more accurate risk assessment and surveillance for cancer for both the patient and family members.

Endoscopy↗