Development of a pediatric differentiated thyroid carcinoma registry within the EuRRECa project: rationale and protocol

Background

Although differentiated thyroid carcinoma (DTC) is the most frequent endocrine pediatric cancer, it is rare in childhood and adolescence. While tumor persistence and recurrence are not uncommon, mortality remains extremely low. Complications of treatment are however reported in up to 48% of the survivors. Due to the rarity of the disease, current treatment guidelines are predominantly based on the results of small observational retrospective studies and extrapolations from results in adult patients. In order to develop more personalized treatment and follow-up strategies (aiming to reduce complication rates), there is an unmet need for uniform international prospective data collection and clinical trials.

Methods and analysis

The European pediatric thyroid carcinoma registry aims to collect clinical data for all patients ≤18 years of age with a confirmed diagnosis of DTC who have been diagnosed, assessed, or treated at a participating site. This registry will be a component of the wider European Registries for Rare Endocrine Conditions project which has close links to Endo-ERN, the European Reference Network for Rare Endocrine Conditions. A multidisciplinary expert working group was formed to develop a minimal dataset comprising information regarding demographic data, diagnosis, treatment, and outcome. We constructed an umbrella-type registry, with a detailed basic dataset. In the future, this may provide the opportunity for research teams to integrate clinical research questions.

Ethics and dissemination

Written informed consent will be obtained from all participants and/or their parents/guardians. Summaries and descriptive analyses of the registry will be disseminated via conference presentations and peer-reviewed publications.

Analysis of rare disruptive germline mutations in 2,135 enriched BRCA-negative breast cancers excludes additional high-impact susceptibility genes

BACKGROUND

Breast cancer has a significant heritable basis, of which approximately 60% remains unexplained. Testing for BRCA1/BRCA2 offers useful discrimination of breast cancer risk within families, and identification of additional breast cancer susceptibility genes could offer clinical utility.

PATIENTS AND METHODS

We included 2,135 invasive breast cancer cases recruited via the BOCS study, a retrospective UK study of familial breast cancer.

ELIGIBILITY CRITERIA

female, BRCA-negative, white European ethnicity, and one of: i) breast cancer family history, ii) bilateral disease, iii) young age of onset (<30 years), iv) concomitant ovarian cancer. We undertook exome sequencing of cases and performed gene-level burden testing of rare damaging variants against those from 51,377 ethnicity-matched population controls from gnomAD.

RESULTS

159/2135 (7.4%) cases had a qualifying variant in an established breast cancer susceptibility gene, with minimal evidence of signal in other cancer susceptibility genes. Known breast cancer susceptibility genes PALB2, CHEK2 and ATM were the only genes to retain statistical significance after correcting for multiple testing. Due to the enrichment of hereditary cases in the series, we had good power (>80%) to detect a gene of BRCA1-like risk (odds ratio = 10.6) down to a population minor allele frequency of 4.6 x 10^-5 (1 in 10,799, less than one tenth that of BRCA1)and of PALB2-like risk (odds ratio = 5.0) down to a population minor allele frequency of 2.8 x 10^-4 (1 in 1,779, less than half that of PALB2). Power was lower for identification of novel moderate penetrance genes (odds ratio = 2-3) like CHEK2 and ATM.

CONCLUSIONS

This is the largest case-control whole-exome analysis of enriched breast cancer published to date. Whilst additional breast cancer susceptibility genes likely exist, those of high penetrance are likely to be of very low mutational frequency. Contention exists regarding the clinical utility of such genes.

Attitudes towards risk-reducing early salpingectomy with delayed oophorectomy for ovarian cancer prevention: a cohort study

OBJECTIVE

To determine risk-reducing early salpingectomy and delayed oophorectomy (RRESDO) acceptability and effect of surgical prevention on menopausal sequelae/satisfaction/regret in women at increased ovarian cancer (OC) risk.

DESIGN

Multicentre, cohort, questionnaire study (IRSCTN:12310993).

SETTING

United Kingdom (UK).

POPULATION

UK women without OC ≥18 years, at increased OC risk, with/without previous RRSO, ascertained through specialist familial cancer/genetic clinics and BRCA support groups.

METHODS

Participants completed a 39-item questionnaire. Baseline characteristics were described using descriptive statistics. Logistic/linear regression models analysed the impact of variables on RRESDO acceptability and health outcomes.

MAIN OUTCOMES

RRESDO acceptability, menopausal sequelae, satisfaction/regret.

RESULTS

In all, 346 of 683 participants underwent risk-reducing salpingo-oophorectomy (RRSO). Of premenopausal women who had not undergone RRSO, 69.1% (181/262) found it acceptable to participate in a research study offering RRESDO. Premenopausal women concerned about sexual dysfunction were more likely to find RRESDO acceptable (odds ratio [OR] = 2.9, 95% CI 1.2-7.7, P = 0.025). Women experiencing sexual dysfunction after premenopausal RRSO were more likely to find RRESDO acceptable in retrospect (OR = 5.3, 95% CI 1.2-27.5, P < 0.031). In all, 88.8% (143/161) premenopausal and 95.2% (80/84) postmenopausal women who underwent RRSO, respectively, were satisfied with their decision, whereas 9.4% (15/160) premenopausal and 1.2% (1/81) postmenopausal women who underwent RRSO regretted their decision. HRT uptake in premenopausal individuals without breast cancer (BC) was 74.1% (80/108). HRT use did not significantly affect satisfaction/regret levels but did reduce symptoms of vaginal dryness (OR = 0.4, 95% CI 0.2-0.9, P = 0.025).

CONCLUSION

Data show high RRESDO acceptability, particularly in women concerned about sexual dysfunction. Although RRSO satisfaction remains high, regret rates are much higher for premenopausal women than for postmenopausal women. HRT use following premenopausal RRSO does not increase satisfaction but does reduce vaginal dryness.

TWEETABLE ABSTRACT

RRESDO has high acceptability among premenopausal women at increased ovarian cancer risk, particularly those concerned about sexual dysfunction.

Genetics and the clinical approach to paragangliomas

This study analyses new information on gene mutations in paragangliomas and puts them into a clinical context. A suspicion of malignancy is critical to determine the workup and surgical approach in adrenal (A-PGL) and extra-adrenal (E-PGL) paragangliomas (PGLs). Malignancy rates vary with location, family history, and gene tests results. Currently there is no algorithm incorporating the above information for clinical use. A sum of 1,821 articles were retrieved from PubMed using the search terms "paraganglioma genetics". Thirty-seven articles were selected of which 9 were analyzed. It was found that 599/2,487 (24%) patients affected with paragangliomas had a germline mutation. Of these 30.2% were mutations in SDHB, 25% VHL, 19.4% RET, 18.4% SDHD, 5.0% NF1, and 2.0% SDHC genes. A family history was positive in 18.1-64.3% of patients. Adrenal PGLs accounted for 55.1% in mutation (+) and 81.0% in mutation (-) patients (RR 1.2, p < 0.0001). Bilateral A-PGLs accounted for 56.4% in mutation (+) and 3.2% in mutation (-) patients (RR 8.7, p < 0.0001). E-PGL were found in 33.6% of mut+ and 17.3% of mut- (RR 1.7, p < 0.0001). In mutation (+) patients PGLs malignancy varied with location, adrenal (6.4%) thoraco-abdominal E-PGL (38%), H & N E-PGL (10%). Malignancy rates were 8.2% in mutation (-) and lower in mutation (+) PGLs except for SDHB 36.5% and SDHC 8.3%. Exclusion of a mutation lowered the probability of malignancy significantly in E-PGL (RR 0.03 (95% CI 0.1-0.6); p < 0.001). Mutation analysis provides valuable preoperative information to assess the risk of malignancy in A-PG and E-PGLs and should be considered in the work up of all E-PGL lesions.

Severe reaction to radiotherapy for breast cancer as the presenting feature of ataxia telangiectasia

Background:

Severe early and late radiation reaction to radiotherapy is extremely rare in breast cancer patients. Such a reaction prompted an investigation into a 44-year-old mother (patient A-T213).

Methods:

A neurological examination was performed and blood lymphocytes and skin fibroblasts were assessed for radiosensitivity chromosomally and by colony-forming assay. The ATM gene was sequenced and ATM mutations modelled by site-directed mutagenesis. The ATM kinase activity was also assessed.

Results:

Patient A-T213 was normally ambulant with no ataxia and minimal other neurological features. T lymphocytes and skin fibroblasts were unusually radiosensitive, although less sensitive than in classical ataxia telangiectasia (A-T). A lymphoblastoid cell line and skin fibroblasts expressed ATM protein with some retained kinase activity. One missense ATM mutation c.8672G>A (p.Gly2891Asp) and a c.1A>G substitution were identified. In the modelling system, the p.Gly2891Asp mutant protein was expressed and shown to have residual ATM kinase activity.

Conclusion:

Patient A-T213 has a milder form of A-T with biallelic ATM mutations, which may have contributed to breast cancer development, and certainly caused the severe radiation reaction. Ataxia telangiectasia should be investigated as a potential cause of untoward severe early and late radiation reactions in breast cancer patients.

Lymphoid tumours and breast cancer in ataxia telangiectasia; substantial protective effect of residual ATM kinase activity against childhood tumours

Background:

Immunodeficiency in ataxia telangiectasia (A-T) is less severe in patients expressing some mutant or normal ATM kinase activity. We, therefore, determined whether expression of residual ATM kinase activity also protected against tumour development in A-T.

Methods:

From a total of 296 consecutive genetically confirmed A-T patients from the British Isles and the Netherlands, we identified 66 patients who developed a malignant tumour; 47 lymphoid tumours and 19 non-lymphoid tumours were diagnosed. We determined their ATM mutations, and whether cells from these patients expressed any ATM with residual ATM kinase activity.

Results:

In childhood, total absence of ATM kinase activity was associated, almost exclusively, with development of lymphoid tumours. There was an overwhelming preponderance of tumours in patients <16 years without kinase activity compared with those with some residual activity, consistent with a substantial protective effect of residual ATM kinase activity against tumour development in childhood. In addition, the presence of eight breast cancers in A-T patients, a 30-fold increased risk, establishes breast cancer as part of the A-T phenotype.

Conclusion:

Overall, a spectrum of tumour types is associated with A-T, consistent with involvement of ATM in different mechanisms of tumour formation. Tumour type was influenced by ATM allelic heterogeneity, residual ATM kinase activity and age.

Evaluation of the XRCC1 gene as a phenotypic modifier in BRCA1/2 mutation carriers. Results from the consortium of investigators of modifiers of BRCA1/BRCA2

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in genes involved in DNA repair are good candidates to be tested as phenotypic modifiers for carriers of mutations in the high-risk susceptibility genes BRCA1 and BRCA2. The base excision repair (BER) pathway could be particularly interesting given the relation of synthetic lethality that exists between one of the components of the pathway, PARP1, and both BRCA1 and BRCA2. In this study, we have evaluated the XRCC1 gene that participates in the BER pathway, as phenotypic modifier of BRCA1 and BRCA2.

METHODS

Three common SNPs in the gene, c.-77C>T (rs3213245) p.Arg280His (rs25489) and p.Gln399Arg (rs25487) were analysed in a series of 701 BRCA1 and 576 BRCA2 mutation carriers.

RESULTS

An association was observed between p.Arg280His-rs25489 and breast cancer risk for BRCA2 mutation carriers, with rare homozygotes at increased risk relative to common homozygotes (hazard ratio: 22.3, 95% confidence interval: 14.3-34, P<0.001). This association was further tested in a second series of 4480 BRCA1 and 3016 BRCA2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2.

CONCLUSIONS AND INTERPRETATION

No evidence of association was found when the larger series was analysed which lead us to conclude that none of the three SNPs are significant modifiers of breast cancer risk for mutation carriers.

Novel one-stop multidisciplinary follow-up clinic significantly improves cancer risk management in BRCA1/2 carriers

The purpose of this study is to measure the impact of a multidisciplinary one-stop follow-up clinic (MDOSC) on breast and ovarian surveillance, risk reducing surgery and enrolment in clinical trials in BRCA1/2 carriers. All BRCA1/2 carriers in our region were invited and chose which specialists to see in our MDOSC offering best practice using clinical protocols based on national guidelines and published data. Uptake was evaluated over 24 months recording numbers of individuals undergoing breast and ovarian surveillance, risk reducing surgery, newly diagnosed cancers, their method of detection and participation in clinical trials. 172 (60%) of invited BRCA1/2 carriers chose to attend the MDOSC. Breast surveillance was initiated in 88% and screening frequency altered in 14% of women to comply with national guidelines. Risk reducing salpingo-oophorectomy was chosen by 47% of women and an additional 39% were considering it. The rate of failure to remove fallopian tubes fell from 15 to 3% of procedures (P < 0.01) and peritoneal washings and serial sectioning of tubes and ovaries rose from 25% and 14% before, to 67% (P < 0.001) and 63% (P < 0.001) procedures, respectively, after initiation of our MDOSC. 24% of women considered and 18% decided to undergo risk reducing mastectomy during the follow-up period. Participation in clinical trials increased significantly from 51 to 229 enrolments (P < 0.001). Our novel MDOSC designed to devise an individually tailored cancer risk management strategy had a high uptake amongst our BRCA1/2 carriers. Attendance resulted in improved breast and ovarian cancer risk management.

Targeted prostate cancer screening in men with mutations in BRCA1 and BRCA2 detects aggressive prostate cancer: preliminary analysis of the results of the IMPACT study

OBJECTIVE

To evaluate the role of targeted prostate cancer screening in men with BRCA1 or BRCA2 mutations, an international study, IMPACT (Identification of Men with a genetic predisposition to ProstAte Cancer: Targeted screening in BRCA1/2 mutation carriers and controls), was established. This is the first multicentre screening study targeted at men with a known genetic predisposition to prostate cancer. A preliminary analysis of the data is reported.

PATIENTS AND METHODS

Men aged 40-69 years from families with BRCA1 or BRCA2 mutations were offered annual prostate specific antigen (PSA) testing, and those with PSA > 3 ng/mL, were offered a prostate biopsy. Controls were men age-matched (± 5 years) who were negative for the familial mutation.

RESULTS

In total, 300 men were recruited (205 mutation carriers; 89 BRCA1, 116 BRCA2 and 95 controls) over 33 months. At the baseline screen (year 1), 7.0% (21/300) underwent a prostate biopsy. Prostate cancer was diagnosed in ten individuals, a prevalence of 3.3%. The positive predictive value of PSA screening in this cohort was 47·6% (10/21). One prostate cancer was diagnosed at year 2. Of the 11 prostate cancers diagnosed, nine were in mutation carriers, two in controls, and eight were clinically significant.

CONCLUSIONS

The present study shows that the positive predictive value of PSA screening in BRCA mutation carriers is high and that screening detects clinically significant prostate cancer. These results support the rationale for continued screening in such men.

Predicting the likelihood of carrying a BRCA1 or BRCA2 mutation: validation of BOADICEA, BRCAPRO, IBIS, Myriad and the Manchester scoring system using data from UK genetics clinics

OBJECTIVES

Genetic testing for the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 has important implications for the clinical management of people found to carry a mutation. However, genetic testing is expensive and may be associated with adverse psychosocial effects. To provide a cost-efficient and clinically appropriate genetic counselling service, genetic testing should be targeted at those individuals most likely to carry pathogenic mutations. Several algorithms that predict the likelihood of carrying a BRCA1 or a BRCA2 mutation are currently used in clinical practice to identify such individuals.

DESIGN

We evaluated the performance of the carrier prediction algorithms BOADICEA, BRCAPRO, IBIS, the Manchester scoring system and Myriad tables, using 1934 families seen in cancer genetics clinics in the UK in whom an index patient had been screened for BRCA1 and/or BRCA2 mutations. The models were evaluated for calibration, discrimination and accuracy of the predictions.

RESULTS

Of the five algorithms, only BOADICEA predicted the overall observed number of mutations detected accurately (ie, was well calibrated). BOADICEA also provided the best discrimination, being significantly better (p<0.05) than all models except BRCAPRO (area under the receiver operating characteristic curve statistics: BOADICEA = 0.77, BRCAPRO = 0.76, IBIS = 0.74, Manchester = 0.75, Myriad = 0.72). All models underpredicted the number of BRCA1 and BRCA2 mutations in the low estimated risk category.

CONCLUSIONS

Carrier prediction algorithms provide a rational basis for counselling individuals likely to carry BRCA1 or BRCA2 mutations. Their widespread use would improve equity of access and the cost-effectiveness of genetic testing.

Variation of a variation: case report of attenuated familial adenomatous polyposis

BACKGROUND

First described in 1988, attenuated familial adenomatous polyposis (AFAP) is a rare autosomal dominant precancerous condition of the gastrointestinal tract. Few reports have described adenocarcinomatous change in the gastroduodenal region thus far.

CASE OUTLINE

We report a case of AFAP presenting with extensive gastric polyposis and ampullary adenocarcinoma in absence of a positive family history of gastrointestinal cancer and a novel mutation.

Genetic, functional, and histopathological evaluation of two C-terminal BRCA1 missense variants

BACKGROUND

The vast majority of BRCA1 missense sequence variants remain uncharacterized for their possible effect on protein expression and function, and therefore are unclassified in terms of their pathogenicity. BRCA1 plays diverse cellular roles and it is unlikely that any single functional assay will accurately reflect the total cellular implications of missense mutations in this gene.

OBJECTIVE

To elucidate the effect of two BRCA1 variants, 5236G>C (G1706A) and 5242C>A (A1708E) on BRCA1 function, and to survey the relative usefulness of several assays to direct the characterisation of other unclassified variants in BRCA genes.

METHODS AND RESULTS

Data from a range of bioinformatic, genetic, and histopathological analyses, and in vitro functional assays indicated that the 1708E variant was associated with the disruption of different cellular functions of BRCA1. In transient transfection experiments in T47D and 293T cells, the 1708E product was mislocalised to the cytoplasm and induced centrosome amplification in 293T cells. The 1708E variant also failed to transactivate transcription of reporter constructs in mammalian transcriptional transactivation assays. In contrast, the 1706A variant displayed a phenotype comparable to wildtype BRCA1 in these assays. Consistent with functional data, tumours from 1708E carriers showed typical BRCA1 pathology, while tumour material from 1706A carriers displayed few histopathological features associated with BRCA1 related tumours.

CONCLUSIONS

A comprehensive range of genetic, bioinformatic, and functional analyses have been combined for the characterisation of BRCA1 unclassified sequence variants. Consistent with the functional analyses, the combined odds of causality calculated for the 1706A variant after multifactorial likelihood analysis (1:142) indicates a definitive classification of this variant as "benign". In contrast, functional assays of the 1708E variant indicate that it is pathogenic, possibly through subcellular mislocalisation. However, the combined odds of 262:1 in favour of causality of this variant does not meet the minimal ratio of 1000:1 for classification as pathogenic, and A1708E remains formally designated as unclassified. Our findings highlight the importance of comprehensive genetic information, together with detailed functional analysis for the definitive categorisation of unclassified sequence variants. This combination of analyses may have direct application to the characterisation of other unclassified variants in BRCA1 and BRCA2.

Analysis of somatic molecular changes, clinicopathological features, family history, and germline mutations in colorectal cancer families: evidence for efficient diagnosis of HNPCC and for the existence of distinct groups of non-HNPCC families

OBJECTIVE

To analyse somatic molecular changes, clinicopathological features, family history, and germline mutations in families with colorectal cancer (CRC).

METHODS

Molecular changes (K-ras and beta-catenin mutations, chromosome 18q allele loss (LOH), APC LOH, microsatellite instability (MSI), and expression of beta-catenin and p53) were examined in four series of CRC patients with proven or probable hereditary disease: hereditary non-polyposis colon cancer (HNPCC); MYH associated polyposis (MAP); multiple (>5) colorectal adenomas without familial adenomatous polyposis (FAP); and other families/cases referred to family cancer clinics (FCC series). HNPCC was diagnosed using a combination of germline mutation screening and tumour studies. A series of unselected CRC patients was also studied.

RESULTS

There was overlap between genetic pathways followed by each type of CRC, but significant differences included: increased frequency of K-ras mutation and reduced frequency of APC LOH in cancers from MAP, but not from multiple adenoma patients; reduced frequency of LOH in HNPCC CRCs; and increased MSI in CRCs from HNPCC, but not from FCC or multiple adenoma patients. HNPCC was apparently detected efficiently by combined germline and somatic analysis. Cancers from the FCC, unselected, and multiple adenoma series shared similar molecular characteristics. In the FCC and multiple adenoma series, hierarchical cluster analysis using the molecular features of the cancers consistently identified two distinct groups, distinguished by presence or absence of K-ras mutation.

CONCLUSIONS

While K-ras mutation status is known to differentiate hereditary bowel cancer syndromes such as MAP and FAP, it may also distinguish groups of non-HNPCC, FCC patients whose disease has different, as yet unknown, genetic origins.

Refining the Amsterdam Criteria and Bethesda Guidelines: testing algorithms for the prediction of mismatch repair mutation status in the familial cancer clinic

PURPOSE

Hereditary nonpolyposis colon cancer (HNPCC) is a Mendelian dominant syndrome of bowel, endometrial, and other cancers and results from germline mutations in mismatch repair (MMR) genes. HNPCC is now best diagnosed on molecular grounds using MMR mutation screening, aided by microsatellite instability (MSI) and immunohistochemistry in tumors. Selection of families for molecular investigation of HNPCC is usually based on suboptimal methods (Amsterdam Criteria or Bethesda Guidelines), but these can be improved using additional clinical data (mean ages of affected persons and presence of endometrial cancer) in a quantitative model.

METHODS

We have verified the performance of the Wijnen model and have shown that it remains valid when HNPCC is diagnosed using mutation screening, MSI, and immunohistochemistry. We have also set up and verified our own models (Amsterdam-plus and Alternative), which perform at least as well as the Wijnen model.

RESULTS

The Amsterdam-plus model improves on the Amsterdam Criteria by using five extra variables (numbers of colorectal and endometrial cancers in the family, number of patients with five or more adenomas, number with more than one primary cancer of the colorectum or endometrium, and mean age of presentation) and performs better than the Wijnen model. The Alternative model avoids the need to evaluate the Amsterdam Criteria and performs nearly as well as the other models.

CONCLUSION

We believe that a quantitative model, such as the Amsterdam-plus model, should be the first choice for selecting families or patients for evaluation of HNPCC using molecular tests. We present an algorithm for this process.

Molecular prenatal diagnosis in a case of an X-linked dominant chondrodysplasia punctata

X-linked dominant chondrodysplasia punctata, (CDPX2-MIM302960) also known as Conradi-Hünermann-Happle syndrome, is a rare form of skeletal dysplasia that affects the skeleton, skin, hair, and eyes. The disorder is caused by mutations within the emopamil binding protein (Ebp) that functions as a delta(8), delta(7) sterol isomerase in the cholesterol biosynthesis pathway. To date, over 40 separate mutations have been reported in the Ebp gene, EBP, with no obvious correlation between the molecular defects and the severity of the clinical phenotype. We have studied a 30-year-old woman who presented in adulthood with skin, hair, and mild skeletal defects but no ocular abnormalities and have identified a heterozygous missense mutation within the third transmembrane domain of the protein. In addition, we have performed molecular prenatal testing on her unborn fetus. The results demonstrate inter-familial variability for missense mutations within the emopamil binding protein and add to the molecular data for CDPX2.

Identification of germline missense mutations and rare allelic variants in the ATM gene in early-onset breast cancer

Epidemiological studies have shown an increased risk of breast cancer in obligate ataxia telangiectasia (A-T) heterozygotes. We analyzed 100 samples from young breast cancer patients for mutations in ataxia-telangiectasia mutated (ATM), the gene responsible for the autosomal recessive condition, A-T, to determine whether A-T heterozygosity predisposes such individuals to develop breast cancer. These patients were selected from families with a moderate or absent family history of breast cancer and included a subset of 16 radiosensitive patients. Forty-four germline sequence variants were detected by fluorescent chemical cleavage of mismatch of RT-PCR products. These included seven rare variants found in nine patients (three described for the first time), but no truncating mutations. Although three variants were detected in the radiosensitive subset, this was not statistically significant compared to the nonradiosensitive group. One variant, G2765S, is likely to be a missense mutation, but the other six variants probably represent rare polymorphisms. However, five of the seven rare germline variants detected showed loss of heterozygosity of the wild-type ATM allele for one or more markers close to the ATM locus in matched tumor DNA. This high rate of somatic inactivation of ATM may indicate either that these rare variants play a role in breast cancer development or alternatively that a neighboring tumor suppressor gene is important for tumorigenesis. We found germline truncating ATM mutations to be rare in these young breast cancer patients and therefore they are unlikely to play a role in the etiology of their disease. Genes Chromosomes Cancer 26:286-294, 1999.

Rapid and efficient ATM mutation detection by fluorescent chemical cleavage of mismatch: identification of four novel mutations

Mutations in the Ataxia Telangiectasia Mutated (ATM) gene are responsible for the autosomal recessive disease Ataxia Telangiectasia (A-T). A wide variety of mutations scattered across the entire coding region (9168bp) of ATM have been found, which presents a challenge in developing an efficient mutation screening strategy for detecting unknown mutations. Fluorescent chemical cleavage of mismatch (FCCM) is an ideal mutation screening method, offering a non-radioactive alternative to other techniques such as restriction endonuclease fingerprinting (REF). Using FCCM, we have developed an efficient, accurate and sensitive mutation detection method for screening RT-PCR products for ATM mutations. We have identified seven ATM mutations in five A-T families, four of which are previously unknown. We quantified ATM protein expression in four of the families and found variable ATM protein expression (0-6.4%), further evidence for mutant ATM protein expression in both classic and variant A-T patients. We conclude that FCCM offers a robust ATM mutation detection method and can be used to screen for ATM mutations in cancer-prone populations.

Identification of missense and truncating mutations in the BRCA1 gene in sporadic and familial breast and ovarian cancer

The cloning of the breast and ovarian cancer susceptibility gene, BRCA1, allows direct estimation of the proportion of these cancers in the general population which can be attributed to germline mutations in this gene. We have used a combination of SSCP, heteroduplex analysis, and chemical cleavage of mismatch to screen the BRCA1 gene for mutations in the germline of 42 patients with breast or ovarian cancer who either have a moderate family history of these cancers, or have no family history of malignancy but a very early onset of the disease. A total of 30 sequence variants were observed, eight of which have not been described previously. Three sequence changes detected by chemical cleavage or heteroduplex analysis were missed by SSCP. The variants included 13 missense mutations, which were assessed for their pathogenic implications. Two of these (M18T and A1708E) are nonconservative substitutions which are located in evolutionarily conserved regions of the gene: M18T lies just upstream of the RING finger motif, and A1708E abolishes the transcriptional transactivation activity of the carboxy-terminal region of BRCA1. Mutations were observed in eight patients overall (19.0%), and protein-truncating mutations occurred in five of 27 (18.5%) families with 1-3 cases of breast or ovarian cancer. The data suggest that a significant proportion of patients with a modest or no family history of these cancers may carry germline mutations in BRCA1.