A Ser49Cys variant in the ataxia telangiectasia, mutated, gene that is more common in patients with breast carcinoma compared with population controls

The prevalence of ataxia telangiectasia mutated (ATM) variants in patients with breast cancer patients: a systematic review and meta-analysis

Breast cancer is the most common cancer in women, and its high mortality has become one of the biggest health problems globally. Several studies have reported an association between breast cancer and ATM gene variants. This study aimed to demonstrate and analyze the relationship between ATM gene polymorphisms and breast cancer prevalence rate. A systematic literature review was undertaken using the following databases: Medline (PubMed), Web of sciences, Scopus, EMBASE, Cochrane, Ovid, and CINHAL to retrieve all cross-sectional studies between January 1990 and January 2020, which had reported the frequency of ATM variants in patients with breast cancer. A random-effects model was applied to calculate the pooled prevalence with a 95% confidence interval. The pooled prevalence of ATM variants in patients with breast cancer was 7% (95% CI: 5−8%). Also, the pooled estimate based on type of variants was 6% (95% CI: 4−8%; I square: 94%; P: 0.00) for total variants¸ 0% (95% CI: 0−1%; I square: 0%; P: 0.59) for deletion variants, 12% (95% CI: 7−18%; I square: 99%; P: 0.00) for substitution variants, and 2% (95% CI: 4−9%; I square: 67%; P: 0.08) for insertion variants. This meta-analysis showed that there is a significant relationship between ATM variants in breast cancer patients. Further studies are required to determine which of the variants of the ATM gene are associated with BRCA mutations.

Polymorphism rs1801516 (G > A) in the ATM gene is not associated with overall cancer risk: an updated meta-analysis

OBJECTIVE

The ataxia telangiectasia mutated (ATM) gene contains a functional single nucleotide polymorphism (SNP) rs1801516 (G > A) that may be associated with cancer risk. This meta-analysis aimed to interrogate the relationship between rs1801516 and cancer occurrence and disease etiology.

METHODS

We retrieved and identified the available case-control studies that met the inclusion criteria from the PubMed, Web of Science, and Embase databases. Odds ratio (OR) and 95% confidence intervals (CIs) were used to measure the association between rs1801516 and cancer risk. Additionally, we performed sensitivity, subgroup, and publication bias analyses.

RESULTS

After inclusion criteria were met, the meta-analysis included 29 studies, with 9,453 cancer patients (cases) and 14,646 controls. No association was found between rs1801516 and cancer risk (pooled OR = 0.911; 95% CI, 0.740-1.123). Concordantly, no association was found between rs1801516 and cancer risk after subgroup analysis by source of controls, cancer type, or ethnicity, which confirmed the finding of the dominant model that this SNP is not involved in the occurrence of cancer.

CONCLUSIONS

Through this meta-analysis, we found no association between rs1801516 and cancer occurrence as a risk factor. These data provide useful information for future case-control studies on cancer etiology.

Clustering of known low and moderate risk alleles rather than a novel recessive high-risk gene in non-BRCA1/2 sib trios affected with breast cancer

Breast cancer risk is approximately twice as high in first‐degree relatives of female breast cancer cases than in women in the general population. Less than half of this risk can be attributed to the currently known genetic risk factors. Recessive risk alleles represent a relatively underexplored explanation for the remainder of familial risk. To address this, we selected 19 non‐BRCA1/2 breast cancer families in which at least three siblings were affected, while no first‐degree relatives of the previous or following generation had breast cancer. Germline DNA from one of the siblings was subjected to exome sequencing, while all affected siblings were genotyped using SNP arrays to assess haplotype sharing and to calculate a polygenic risk score (PRS) based on 160 low‐risk variants. We found no convincing candidate recessive alleles among exome sequencing variants in genomic regions for which all three siblings shared two haplotypes. However, we found two families in which all affected siblings carried the CHEK2*1100delC. In addition, the average normalized PRS of the “recessive” family probands (0.81) was significantly higher than that in both general population cases (0.35, P = .026) and controls (P = .0004). These findings suggest that the familial aggregation is, at least in part, explained by a polygenic effect of common low‐risk variants and rarer intermediate‐risk variants, while we did not find evidence of a role for novel recessive risk alleles.

What's new?

To find new breast cancer susceptibility alleles, these authors tested families in which at least three affected siblings had non‐BRCA1/2 breast cancer. No new susceptibility alleles emerged, but the analysis did reveal that on average, women from these families who had cancer had significantly higher polygenic risk scores than either sporadic cases or controls. This result highlights the importance of moderate risk alleles acting together in familial breast cancer.

Association between ATM rs1801516 polymorphism and cancer susceptibility: a meta-analysis involving 12,879 cases and 18,054 controls

Background

Ataxia telangiectasia mutated (ATM) gene plays a key role in response to DNA lesions and is related to the invasion and metastasis of malignancy. Epidemiological studies have indicated associations between ATM rs1801516 polymorphism and different types of cancer, but their results are inconsistent. To further evaluate the effect of ATM rs1801516 polymorphism on cancer risk, we conducted this meta-analysis.

Methods

Studies were identified according to specific inclusion criteria by searching PubMed, Web of Science, and Embase databases. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) under recessive, dominant, codominant, and overdominant models of inheritance were calculated to estimate the association between rs1801516 polymorphism and cancer risk.

Results

A total of 37 studies with 12,879 cases and 18,054 controls were included in our study. No significant association was found between rs1801516 polymorphism and cancer risk in overall comparisons (AA vs GG + GA: OR = 0.91, 95% CI, 0.78–1.07; AA+GA vs GG: OR = 1.00, 95% CI, 0.90–1.11; AA vs GG: OR = 0.89, 95% CI, 0.75–1.06; GA vs GG: OR = 1.01, 95% CI, 0.91–1.13; GG + AA vs GA: OR = 1.00, 95% CI, 0.88–1.10). However, after subgroup analyses by region-specified population, significant associations were found in European (AA vs GG + GA: OR = 0.79, 95% CI, 0.65–0.96, P = 0.017; AA vs GG: OR = 0.79, 95% CI, 0.65–0.96, P = 0.017), South American (AA+GA vs GG: OR = 2.15, 95% CI, 1.37–3.38, P = 0.001; GA vs GG: OR = 2.19, 95% CI, 1.38–3.47, P = 0.001; GG + AA vs GA: OR = 0.46, 95% CI, 0.29–0.72, P = 0.001), and Asian (AA vs GG + GA: OR = 7.45, 95% CI, 1.31–42.46, P = 0.024; AA vs GG: OR = 7.40, 95% CI, 1.30–42.19, P = 0.024). Subgroup analyses also revealed that compared with subjects carrying a GG genotype, those carrying a homozygote AA had a decreased risk for breast cancer (AA vs GG: OR = 0.76, 95% CI, 0.59–0.98, P = 0.035), and the homozygote AA was associated with decreased cancer risk in subjects with family history (AA vs GG: OR = 0.68, 95% CI, 0.47–0.98, P = 0.039).

Conclusions

ATM rs1801516 polymorphism is not associated with overall cancer risk in total population. However, for subgroup analyses, this polymorphism is especially associated with breast cancer risk; in addition, it is associated with overall cancer risk in Europeans, South Americans, Asians, and those with family history.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4941-1) contains supplementary material, which is available to authorized users.

ATM in breast and brain tumors: a comprehensive review

The ATM gene is mutated in the syndrome, ataxia-telangiectasia (AT), which is characterized by predisposition to cancer. Patients with AT have an elevated risk of breast and brain tumors Carrying mutations in ATM, patients with AT have an elevated risk of breast and brain tumors. An increased frequency of ATM mutations has also been reported in patients with breast and brain tumors; however, the magnitude of this risk remains uncertain. With the exception of a few common mutations, the spectrum of ATM alterations is heterogeneous in diverse populations, and appears to be remarkably dependent on the ethnicity of patients. This review aims to provide an easily accessible summary of common variants in different populations which could be useful in ATM screening programs. In addition, we have summarized previous research on ATM, including its molecular functions. We attempt to demonstrate the significance of ATM in exploration of breast and brain tumors and its potential as a therapeutic target.

Gene-environment interaction for polymorphisms in ataxia telangiectasia-mutated gene and radiation exposure in carcinogenesis: results from two literature-based meta-analyses of 27120 participants

Purpose

We conducted two meta-analyses of ATM genetic polymorphisms and cancer risk in individuals with or without radiation exposure to determine whether there was a joint effect between the ATM gene and radiation exposure in carcinogenesis.

Results

rs1801516, which was the only ATM polymorphism investigated by more than 3 studies of radiation exposure, was eligible for the present study. The meta-analysis of 23333 individuals without radiation exposure from 24 studies showed no association between the rs1801516 polymorphism and cancer risk, without heterogeneity across studies. The meta-analysis of 3787 individuals with radiation exposure from 6 studies showed a significant association between the rs1801516 polymorphism and a decreased cancer risk, with heterogeneity across studies. There was a borderline-significant difference between the ORs of the two meta-analyses (P = 0.066), and the difference was significant when only Caucasians were included (P = 0.011).

Materials and methods

Publications were identified by searching PubMed, EMBASE, Web of Science, and CNKI databases. Odds ratios (ORs) were calculated to estimate the association between ATM genetic polymorphisms and cancer risk. Tests of interaction were used to compare differences between the ORs of the two meta-analyses.

Conclusions

Our meta-analyses confirmed the presence of a gene-environment interaction between the rs1801516 polymorphism and radiation exposure in carcinogenesis, whereas no association was found between the rs1801516 polymorphism and cancer risk for individuals without radiation exposure. The heterogeneity observed in the meta-analysis of individuals with radiation exposure might be due to gene-ethnicity or gene-gene interactions. Further studies are needed to elucidate sources of the heterogeneity.

Abnormal Expression of DNA Double-Strand Breaks Related Genes, ATM and GammaH2AX, in Thyroid Carcinoma

ATM and γH2AX play a vital role in the detection of DNA double-strand breaks (DSB) and DNA damage response (DDR). This study aims to investigate ATM and γH2AX expression in thyroid cancer and discuss possible relationship between thyroid function tests and DNA damage. The expression of ATM and γH2AX was detected by immunohistochemistry in 30 cases of benign nodular goiter, 110 cases of well differentiated thyroid cancer, 22 cases of poorly differentiated thyroid cancer, and 21 cases of anaplastic thyroid cancer. Clinicopathological features, including differentiation stages, distant metastasis, lymph node metastasis, T classification, TNM stage, and tests of thyroid functions (TPOAb, Tg Ab, T3, FT3, T4, FT4, TSH, and Tg), were reviewed and their associations with γH2AX and ATM were analyzed. γH2AX and ATM expressed higher in thyroid cancer tissues than in benign nodular goiter and normal adjacent tissues. γH2AX was correlated with ATM in thyroid cancer. Both γH2AX and ATM expression were associated with FT3. γH2AX was also associated with T classification, TNM stage, FT4, TSH, and differentiation status. Therefore both of ATM and γH2AX seem to correlate with thyroid hormones and γH2AX plays a role in the differentiation status of thyroid cancer.

Association of the ATM gene polymorphisms with papillary thyroid cancer

Papillary thyroid cancer (PTC) is the most common type of thyroid cancer, yet few genetic markers of PTC risk useful for screening exist. Our study aimed to evaluate the association between single nucleotide polymorphisms (SNPs) of the ataxia telangiectasia mutated (ATM) gene and PTC risk. 358 patients with PTC and 360 healthy controls were included in the case-control study. Four ATM SNPs (rs664677, rs373759, rs4988099, and rs189037) were genotyped by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The analysis of genetic data was performed using the SNPStats program. The allele frequencies and genotype distributions of the four ATM SNPs were not different between PTC patients and controls. We did not observe any tendency of increasing the frequency of the risk allele from controls, patients without metastasis to patients with metastasis (P(trend) > 0.05). Interestingly, the AG genotype of rs373759 was associated with PTC risk under an overdominant model of inheritance (adjusted OR = 1.38; 95 % CI, 1.03-1.87; P = 0.03). No haplotype was observed to be significantly associated with PTC risk. Our results suggest that heterozygosity for the ATM rs373759 polymorphism may be a potential risk factor for PTC.

Defining molecular and cellular responses after low and high linear energy transfer radiations to develop biomarkers of carcinogenic risk or therapeutic outcome

The variability in radiosensitivity across the human population is governed in part by genetic factors. The ability to predict therapeutic response, identify individuals at greatest risk for adverse clinical responses after therapeutic radiation doses, or identify individuals at high risk for carcinogenesis from environmental or medical radiation exposures has a medical and economic impact on both the individual and society at large. As radiotherapy incorporates particles, particularly particles larger than protons, into therapy, the need for such discriminators, (i.e., biomarkers) will become ever more important. Cellular assays for survival, DNA repair, or chromatid/chromosomal analysis have been used to identify at-risk individuals, but they are not clinically applicable. Newer approaches, such as genome-wide analysis of gene expression or single nucleotide polymorphisms and small copy number variations within chromosomes, are examples of technologies being applied to the discovery process. Gene expression analysis of primary or immortalized human cells suggests that there are distinct gene expression patterns associated with radiation exposure to both low and high linear energy transfer radiations and that those most radiosensitive are discernible by their basal gene expression patterns. However, because the genetic alterations that drive radio response may be subtle and cumulative, the need for large sample sizes of specific cell or tissue types is required. A systems biology approach will ultimately be necessary. Potential biomarkers from cell lines or animal models will require validation in a human setting where possible and before being considered as a credible biomarker some understanding of the molecular mechanism is necessary.

Functional variations in the ATM gene and susceptibility to differentiated thyroid carcinoma

CONTEXT

ATM is critical in response to ionizing radiation-induced DNA damage.

OBJECTIVE

Variations in ATM are hypothesized to affect individual susceptibility to thyroid cancer. Our objective was to evaluate the association between ATM polymorphisms and thyroid cancer risk.

DESIGN, PARTICIPANTS, AND METHODS

Six ATM single nucleotide polymorphisms (SNP) were genotyped in two independent case-control series including 592 patients with differentiated thyroid carcinoma (DTC) and 885 healthy individuals. An unconditional logistic regression model was applied to calculate odds ratios (OR) and 95% confidence intervals (CI) for each SNP with respect to risk of DTC and the combination effect of SNP on cancer risk.

RESULTS

The risk-allele frequencies of all the SNP were similar in the two case-control populations. Under a dominant model of inheritance, the G allele of ATM rs189037 exhibited a protective effect against DTC (adjusted OR = 0.8; 95% CI, 0.6-1.0; P = 0.04), and the G allele of rs1800057 was associated with increased risk of DTC (adjusted OR = 1.9; 95% CI, 1.1-3.1; P = 0.02). A protective haplotype (A-G-C-T-C-A) was associated with decreased risk of DTC in non-Hispanic whites (adjusted OR = 0.2; 95% CI, 0.0-0.8; P = 0.03). A significant dose-response relationship was observed between the total number of risk alleles of ATM and DTC risk (P = 0.01). Carriers of a combination of six to seven and eight to 10 risk alleles were at 30% (adjusted OR = 1.3; 95% CI, 1.0-1.7) and 50% (adjusted OR = 1.5; 95% CI, 1.1-2.1) increased risk of DTC, respectively.

CONCLUSION

Individual susceptibility to DTC may be attributable to polymorphisms of ATM, and the associations warrant confirmation in independent studies.

The association between ATM IVS 22-77 T>C and cancer risk: a meta-analysis

Background and Objectives

It has become increasingly clear that ATM (ataxia-telangiectasia-mutated) safeguards genome stability, which is a cornerstone of cellular homeostasis, and ATM IVS 22-77 T>C affects the normal activity of ATM proteins. However, the association between the ATM IVS 22-77 T>C genetic variant and cancer risk is controversial. Therefore, we conducted a systematic meta-analysis to estimate the overall cancer risk associated with the polymorphism and to quantify any potential between-study heterogeneity.

Methods

A total of nine studies including 4,470 cases and 4,862 controls were analyzed for ATM IVS 22-77 T>C association with cancer risk in this meta-analysis. Heterogeneity among articles and their publication bias were also tested.

Results

Our results showed that no association reached the level of statistical significance in the overall risk. Interestingly, in the stratified analyses, we observed an inverse relationship in lung and breast cancer.

Conclusion

Further functional research on the ATM mechanism should be performed to explain the inconsistent results in different cancer types.

Current chemotherapeutic strategies against bladder cancer

Urothelial cancer is a chemotherapy-sensitive malignancy, with the regimen of methotrexate, vinblastine, doxorubicin, and cisplatin (M-VAC) until recently considered to be the first choice for chemotherapy. Poor survival and substantial toxicity associated with M-VAC have led to investigations into alternative chemotherapy strategies, and the combination of gemcitabine and cisplatin (GC) may be promising. In addition, combination chemotherapy of taxanes along with gemcitabine and/or platinum-based agents is also considered to provide clinical benefits as second-line chemotherapy following M-VAC or GC therapy. In the near future, results of trials using molecular target therapies may bring improved outcomes for patients with bladder cancer.

The association between ATM D1853N polymorphism and breast cancer susceptibility: a meta-analysis

Background

Emerging evidence suggests that ataxia telangiectasia-mutated (ATM) is involved in numerous damage repair signaling pathways and cell-cycle checkpoints. Heterozygous carriers of ATM-mutations have an increased risk for the development of breast cancer. The purpose of this study is to evaluate the association between ATM exon39 5557G > A (D1853N, rs1801516) polymorphism and breast cancer susceptibility with the use of a meta-analysis.

Methods

By searching PubMed and Embase databases, a total of 9 epidemiological studies with 4,191 cases and 3,780 controls were identified. Crude odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) for ATM D1853N polymorphism and breast cancer risk were calculated using fixed- or random-effects model based on the degree of heterogeneity among studies.

Results

No significant association between the ATM D1853N polymorphism and breast cancer risk was observed in overall analysis (GA versus GG: OR = 1.18; 95% CI, 0.90-1.53; AA versus GG: OR = 0.77; 95% CI, 0.58-1.03; dominant model: OR = 1.16; 95% CI, 0.89-1.51; and recessive model: OR = 0.78; 95% CI, 0.59-1.04, respectively).

Conclusion

Our results indicate that ATM D1853N polymorphism is not a risk factor for developing breast cancer.

Single-nucleotide polymorphisms in the p53 signaling pathway

The p53 tumor suppressor pathway is central both in reducing cancer frequency in vertebrates and in mediating the response of commonly used cancer therapies. This article aims to summarize and discuss a large body of evidence suggesting that the p53 pathway harbors functional inherited single-nucleotide polymorphisms (SNPs) that affect p53 signaling in cells, resulting in differences in cancer risk and clinical outcome in humans. The insights gained through these studies into how the functional p53 pathway SNPs could help in the tailoring of cancer therapies to the individual are discussed. Moreover, recent work is discussed that suggests that many more functional p53 pathway SNPs are yet to be fully characterized and that a thorough analysis of the functional human genetics of this important tumor suppressor pathway is required.

Rare, evolutionarily unlikely missense substitutions in ATM confer increased risk of breast cancer

The susceptibility gene for ataxia telangiectasia, ATM, is also an intermediate-risk breast-cancer-susceptibility gene. However, the spectrum and frequency distribution of ATM mutations that confer increased risk of breast cancer have been controversial. To assess the contribution of rare variants in this gene to risk of breast cancer, we pooled data from seven published ATM case-control mutation-screening studies, including a total of 1544 breast cancer cases and 1224 controls, with data from our own mutation screening of an additional 987 breast cancer cases and 1021 controls. Using an in silico missense-substitution analysis that provides a ranking of missense substitutions from evolutionarily most likely to least likely, we carried out analyses of protein-truncating variants, splice-junction variants, and rare missense variants. We found marginal evidence that the combination of ATM protein-truncating and splice-junction variants contribute to breast cancer risk. There was stronger evidence that a subset of rare, evolutionarily unlikely missense substitutions confer increased risk. On the basis of subset analyses, we hypothesize that rare missense substitutions falling in and around the FAT, kinase, and FATC domains of the protein may be disproportionately responsible for that risk and that a subset of these may confer higher risk than do protein-truncating variants. We conclude that a comparison between the graded distributions of missense substitutions in cases versus controls can complement analyses of truncating variants and help identify susceptibility genes and that this approach will aid interpretation of the data emerging from new sequencing technologies.

Description and validation of high-throughput simultaneous genotyping and mutation scanning by high-resolution melting curve analysis

Mutation scanning using high-resolution melting curve analysis (HR-melt) is an effective and sensitive method to detect sequence variations. However, the presence of a common SNP within a mutation scanning amplicon may considerably complicate the interpretation of results and increase the number of samples flagged for sequencing by interfering with the clustering of samples according to melting profiles. A protocol describing simultaneous high-resolution gene scanning and genotyping has been reported. Here, we show that it can improve the sensitivity and the efficiency of large-scale case-control mutation screening. Two exons of ATM, both containing an SNP interfering with standard mutation scanning, were selected for screening of 1,356 subjects from an international breast cancer genetics study. Asymmetric PCR was performed in the presence of an SNP-specific unlabeled probe. Stratification of the samples according to their probe-target melting was aided by customized HR-melt software. This approach improved identification of rare known and unknown variants, while dramatically reducing the sequencing effort. It even allowed genotyping of tandem SNPs using a single probe. Hence, HR-melt is a rapid, efficient, and cost-effective tool that can be used for high-throughput mutation screening for research, as well as for molecular diagnostic and clinical purposes.

Determinants of protein function revealed by combinatorial entropy optimization

We use a new algorithm (combinatorial entropy optimization [CEO]) to identify specificity residues and functional subfamilies in sets of proteins related by evolution. Specificity residues are conserved within a subfamily but differ between subfamilies, and they typically encode functional diversity. We obtain good agreement between predicted specificity residues and experimentally known functional residues in protein interfaces. Such predicted functional determinants are useful for interpreting the functional consequences of mutations in natural evolution and disease.

Risk of cancer by ATM missense mutations in the general population

PURPOSE

Truncating and missense mutations in the ATM gene, which cause insufficient DNA damage surveillance, allow damaged cells to proceed into mitosis, which eventually results in increased cancer susceptibility. We tested the hypotheses that ATM Ser49Cys and ATM Ser707Pro heterozygosity increase the risk of cancer overall, of breast cancer, and of 26 other cancer subtypes in the general population.

PATIENTS AND METHODS

We genotyped 10,324 individuals from the Danish general population who were observed prospectively for 36 years, during which 2,056 developed cancer.

RESULTS

Multifactorially adjusted hazard ratios for ATM Ser49Cys heterozygotes versus noncarriers were 1.2 (95% CI, 0.9 to 1.5) for cancer overall, 0.8 (95% CI, 0.3 to 2.0) for breast cancer, 4.8 (95% CI, 2.2 to 11) for melanoma, 2.3 (95% CI, 1.1 to 5.0) for prostate cancer, and 3.4 (95% CI, 1.1 to 11) for cancer of the oral cavity/pharynx. Multifactorially adjusted hazard ratios for ATM Ser707Pro heterozygotes versus noncarriers were 0.8 (95% CI, 0.6 to 1.2) for cancer overall, 0.6 (95% CI, 0.2 to 1.6) for breast cancer, 10 (95% CI, 1.1 to 93) for thyroid/other endocrine tumors, and 2.7 (95% CI, 1.0 to 7.6) for cancer of corpus uteri.

CONCLUSION

ATM missense mutations do not increase the risk of cancer overall or of breast cancer in the general population; however, we observed in exploratory analyses that ATM missense mutations may be associated with an increased risk of other cancer subtypes. As we did multiple comparisons, some of these findings could represent chance findings rather than real phenomena.

Links between DNA double strand break repair and breast cancer: Accumulating evidence from both familial and nonfamilial cases

DNA double strand break (DSB) repair dysfunction increases the risk of familial and sporadic breast cancer. Advances in the understanding of genetic predisposition to breast cancer have also been made by screening naturally occurring polymorphisms. These studies revealed that subtle defects in DNA repair capacity arising from low-penetrance genes, or combinations thereof, are modified by other genetically determined or environmental risk factors and correlate to breast cancer risk. Overexpression of DSB repair enzymes, absence of surveillance factors and mutation or loss of heterozygosity in any of these genes contributes to the pathogenesis of sporadic breast cancers. The results identifying DSB repair defects as a common denominator for breast cancerogenesis focus attention on functional assays in order to assess DSB repair capacity as a diagnostic tool to detect increased breast cancer risk and to enable therapeutic strategies specifically targeting the tumor.

A hypothesis-generating search for new genetic breast cancer syndromes--a national study in 803 Swedish families

Among Swedish families with an inherited predisposition for breast cancer, less than one third segregate mutations in genes known to be associated with an increased risk of breast cancer in combination with other types of tumours. In a search for new putative familial breast cancer syndromes we studied Swedish families undergoing genetic counselling during 1992-2000.

Four thousand families from counselling clinics in Sweden were eligible for study. Families with breast cancer only were excluded, as were families with mutations in genes already known to be associated with malignant diseases. We identified 803 families with two or more cases of breast cancer and at least one other type of cancer. The observed proportion of different types of non-breast cancer was compared with the percentage distribution of non-breast cancer tumours in Sweden in 1958 and 1999.

We found tumours in the colon, ovary, endometrium, pancreas and liver, as well as leukaemia in a significantly larger proportion of the study population than in the general population in both years. These tumours were also seen among families where several members had one additional tumour, suggesting that malignancies at these sites, in combination with breast tumours, could constitute genetic syndromes. Endometrial carcinoma has not previously been described in the context of breast cancer syndromes and the excess of malignancies at this site could not be explained by secondary tumours. Thus, we suggest that endometrial carcinoma and breast cancer constitute a new breast cancer syndrome. Further investigation is warranted to categorize phenotypes of both breast and endometrial tumours in this subgroup.

Two-stage case-control study of common ATM gene variants in relation to breast cancer risk

The ataxia telangiectasia mutated (ATM) gene is a tumor suppressor gene that plays a critical role in cell cycle arrest, apoptosis, and DNA repair. We evaluated two reported nonsynonymous SNPs (rs1800054 and rs1800058) and three additional common gene variants (rs664143, rs228589, rs1003623) in the ATM gene in relation to breast cancer risk. A two-stage case-control study, using data from the Shanghai Breast Cancer Study, was conducted in which all SNPs were screened in the stage I study, including 1,123 cases and 1,232 controls. Any promising associations were re-evaluated in the stage II study, including 2,003 cases and 1,918 controls. In the stage I study, with the exception of rs1003623, no apparent association was found for any other SNPs with breast cancer risk. For the rs1003623, the T allele was associated with an increased breast cancer risk among postmenopausal women with odds ratios (ORs) of 1.4 (95% Confidence Intervals (CIs) = 1.0-1.9) for the CT and 1.6 (95% CIs = 1.0-2.4) for the TT, (P for trend = 0.03). This association, however, was not replicated in the stage II study, suggesting that the positive association identified in stage I for rs1003623 may be due to chance. Our study reveals no apparent association of common ATM variants with breast cancer risk and underscores the importance of replication using independent samples to reduce type I errors in association studies of low-penetrance genetic factors.

Comprehensive analysis of the ATM, CHEK2 and ERBB2 genes in relation to breast tumour characteristics and survival: a population-based case-control and follow-up study

BACKGROUND

Mutations in the ataxia-telangiectasia mutated (ATM) and checkpoint kinase 2 (CHEK2) genes and amplification of the v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2 (ERBB2) gene have been suggested to have an important role in breast cancer aetiology. However, whether common variation in these genes has a role in the development of breast cancer or breast cancer survival in humans is still not clear.

METHODS

We performed a comprehensive haplotype analysis of the ATM, CHEK2 and ERBB2 genes in a Swedish population-based study, which included 1,579 breast cancer cases and 1,516 controls. We followed the cases for 8.5 years, on average, and retrieved information on the date and cause of death during that period from the nationwide Swedish causes of death registry. We selected seven haplotype-tagging SNPs (tagSNPs) in the ATM gene, six tagSNPs in the CHEK2 gene and seven tagSNPs in the ERBB2 gene that predicted both haplotypic and single locus variations in the respective genes with R2 values > or = 0.8. These tagSNPs were genotyped in the complete set of cases and controls. We computed expected haplotype dosages of the tagSNP haplotypes and included the dosages as explanatory variables in Cox proportional hazards or logistic regression models.

RESULTS

We found no association between any genetic variation in the ATM, CHEK2 or ERBB2 genes and breast cancer survival or the risk of developing tumours with certain characteristics.

CONCLUSION

Our results indicate that common variants in the ATM, CHEK2 or ERBB2 genes are not involved in modifying breast cancer survival or the risk of tumour-characteristic-defined breast cancer.

A common coding variant in CASP8 is associated with breast cancer risk

The Breast Cancer Association Consortium (BCAC) has been established to conduct combined case-control analyses with augmented statistical power to try to confirm putative genetic associations with breast cancer. We genotyped nine SNPs for which there was some prior evidence of an association with breast cancer: CASP8 D302H (rs1045485), IGFBP3 -202 C --> A (rs2854744), SOD2 V16A (rs1799725), TGFB1 L10P (rs1982073), ATM S49C (rs1800054), ADH1B 3' UTR A --> G (rs1042026), CDKN1A S31R (rs1801270), ICAM5 V301I (rs1056538) and NUMA1 A794G (rs3750913). We included data from 9-15 studies, comprising 11,391-18,290 cases and 14,753-22,670 controls. We found evidence of an association with breast cancer for CASP8 D302H (with odds ratios (OR) of 0.89 (95% confidence interval (c.i.): 0.85-0.94) and 0.74 (95% c.i.: 0.62-0.87) for heterozygotes and rare homozygotes, respectively, compared with common homozygotes; P(trend) = 1.1 x 10(-7)) and weaker evidence for TGFB1 L10P (OR = 1.07 (95% c.i.: 1.02-1.13) and 1.16 (95% c.i.: 1.08-1.25), respectively; P(trend) = 2.8 x 10(-5)). These results demonstrate that common breast cancer susceptibility alleles with small effects on risk can be identified, given sufficiently powerful studies.

Breast cancer in patients carrying a germ-line CHEK2 mutation: Outcome after breast conserving surgery and adjuvant radiotherapy

BACKGROUND AND PURPOSE

Women carrying mutations in the CHEK2 gene are at an increased breast cancer risk. Data about outcome and prognosis for these patients after standard multimodality treatment are scarce at present.

MATERIALS AND METHODS

One-hundred and fifty (150) patients with non-metastasized early-stage breast cancer (T1-2) receiving postoperative radiotherapy following breast-conservative surgery at our department were included in this analysis. Carriers were identified using mutation-specific restriction enzyme-based screening assays in previous investigations. Twenty-five breast cancer patients were heterozygous for one of three CHEK2 gene mutations (I157T, n=13; 1100delC, n=10; IVS2+1G>A, n=2). The comparison group consisted of 125 early-stage breast cancer patients without a CHEK2 gene mutation (non-carriers). Median follow-up was 87 months for the total cohort of patients.

RESULTS

Local recurrences occurred in 13 patients (carriers, 3 (12%); non-carriers, 10 (8%)) and distant metastases occurred in 27 patients (carriers, 8 (32%); non-carriers, 19 (15%)). Twenty-five patients had deceased (carriers, 8 (32%); non-carriers, 17 (14%)) with all but 3 deaths related to breast cancer. Actuarial 7-year local relapse-free survival was 86% in carriers versus 90% in non-carriers (p=0.48). Actuarial metastasis-free, disease-free and overall survival at 7 years were 64% vs. 84% (p=0.045), 59% vs. 78% (p=0.07) and 69% vs. 87% (p=0.10), respectively. In a multivariate step-wise Cox regression analysis presence of a CHEK2 mutation remained a borderline significant discriminator for metastasis-free survival (p=0.048; OR=0.4; 95% CI 0.2-1.0) next to T-stage (p=0.001; OR 0.3; 95% CI 0.1-0.6).

CONCLUSIONS

Heterozygosity for a germline CHEK2 mutation appears to represent an adverse prognostic factor in patients with early-stage breast cancer. If confirmed in larger studies these data may serve as a basis for future surveillance and treatment strategies taking into account individual germline mutational status.

Population-based estimates of breast cancer risks associated with ATM gene variants c.7271T>G and c.1066-6T>G (IVS10-6T>G) from the Breast Cancer Family Registry

The ATM gene variants segregating in ataxia-telangiectasia families are associated with increased breast cancer risk, but the contribution of specific variants has been difficult to estimate. Previous small studies suggested two functional variants, c.7271T>G and c.1066-6T>G (IVS10-6T>G), are associated with increased risk. Using population-based blood samples we found that 7 out of 3,743 breast cancer cases (0.2%) and 0 out of 1,268 controls were heterozygous for the c.7271T>G allele (P=0.1). In cases, this allele was more prevalent in women with an affected mother (odds ratio [OR]=5.5, 95% confidence interval [CI]=1.2-25.5; P=0.04) and delayed child-bearing (OR=5.1; 95% CI=1.0-25.6; P=0.05). The estimated cumulative breast cancer risk to age 70 years (penetrance) was 52% (95% CI=28-80%; hazard ratio [HR]=8.6; 95% CI=3.9-18.9; P<0.0001). In contrast, 13 of 3,757 breast cancer cases (0.3%) and 10 of 1,268 controls (0.8%) were heterozygous for the c.1066-6T>G allele (OR=0.4; 95% CI=0.2-1.0; P=0.05), and the penetrance was not increased (P=0.5). These findings suggest that although the more common c.1066-6T>G variant is not associated with breast cancer, the rare ATM c.7271T>G variant is associated with a substantially elevated risk. Since c.7271T>G is only one of many rare ATM variants predicted to have deleterious consequences on protein function, an effective means of identifying and grouping these variants is essential to assess the contribution of ATM variants to individual risk and to the incidence of breast cancer in the population.

ATM and breast cancer susceptibility

ATM was originally identified by positional cloning as the gene that underlies the autosomal recessive condition ataxia-telangiectasia. The encoded protein plays a central role in the complex processes that repair DNA double-strand breaks. Nearly 20 years ago, epidemiological surveys of relatives of ataxia-telangiectasia cases suggested that female relatives were at modestly increased risk of breast cancer. Subsequently, many studies have tried to clarify the role of ATM in breast cancer susceptibility, but have produced inconclusive and/or inconsistent results. Recently, large epidemiological and molecular studies have finally provided conclusive evidence that ATM mutations that cause ataxia-telangiectasia are breast cancer susceptibility alleles.

The ATM missense mutation p.Ser49Cys (c.146C>G) and the risk of breast cancer

Homozygous mutation in the ATM gene causes ataxia telangiectasia and heterozygous mutation carriers may be at increased risk of breast cancer. We studied a total of 22 ATM variants; 18 variants were analyzed in one of two large population-based studies from the U.S. and Poland, and four variants were analyzed in all 2,856 breast cancer cases and 3,344 controls from the two studies. The missense mutation Ser49Cys (c.146C>G, p.S49C), carried by approximately 2% of subjects, was more common in cases than controls in both study populations, combined odds ratio (OR) 1.69 (95% CI, 1.19-2.40; P=0.004). Another missense mutation at approximately 2% frequency, Phe858Leu (c.2572T>C, p.F858L), was associated with a significant increased risk in the U.S. study but not in Poland, and had a combined OR of 1.44 (95% CI, 0.98-2.11; P=0.06). These analyses provide the most convincing evidence thus far that missense mutations in ATM, particularly p.S49C, may be breast cancer susceptibility alleles. Because of their low frequency, even larger sample sizes are required to more firmly establish these associations.

Radiobiology of Breast Cancer

Advances in molecular and cellular biology are transforming our understanding of breast cancer and promise the same for radiotherapy over the next few years. At the clinical level, the molecular basis of fractionation dependency and other tumour and normal tissue responses are likely to become clearer. More importantly, they will become useful in the clinic, where molecular characterisation of the patient and tumour will start to determine therapeutic options. Although many of the fundamental processes are only amenable to study in laboratory systems, the power of array-based technologies makes it possibly to address highly relevant questions in the clinic, using functional imaging and/or tissue biopsies. To help clinical oncologists exploit these opportunities in translational research, some aspects of the molecular and cellular basis of radiotherapy are described below in their relation to breast cancer.

ATM Gene Founder Haplotypes and Associated Mutations in Polish Families with Ataxia-Telangiectasia

Ataxia-telangiectasia (A-T) is an early onset autosomal recessive ataxia associated with characteristic chromosomal aberrations, cell cycle checkpoint defects, cancer susceptibility, and sensitivity to ionizing radiation. We utilized the protein truncation test (PTT), and single strand conformation polymorphism (SSCP) on cDNA, as well as denaturing high performance liquid chromatography (dHPLC) on genomic DNA (gDNA) to screen for mutations in 24 Polish A-T families. Twenty-six distinct Short Tandem Repeat (STR) haplotypes were identified. Three founder mutations accounted for 58% of the alleles. Three-quarters of the families had at least one recurring (shared) mutation, which was somewhat surprising given the low frequency of consanguinity in Poland. STR haplotyping greatly improved the efficiency of mutation detection. We identified 44 of the expected 48 mutations (92%): sixty-nine percent were nonsense mutations, 23% caused aberrant splicing, and 5% were missense mutations. Four mutations have not been previously described. Two of the Polish mutations have been observed previously in Amish and Mennonite A-T patients; this is compatible with historical records. Shared mutations shared the same Single Nucleotide Polymorphism (SNP) and STR haplotypes, indicating common ancestries. The Mennonite mutation, 5932 G>T, is common in Russian A-T families, and the STR haplovariants are the same in both Poland and Russia. Attempts to correlate phenotypes with genotypes were inconclusive due to the limited numbers of patients with identical mutations.

The Ataxia-telangiectasia mutated gene and breast cancer: gene expression profiles and sequence variants

The role of the Ataxia-telangiectaisa mutated (ATM) gene, as a risk factor for breast cancer has been a consistent theme in the literature since the first reports by Swift and colleagues who reported that ATM heterozygotes in AT families had increased risks of developing breast cancer. Loss of heterozygosity at the ATM locus has been reported in 30-40% of breast tumours and 50-70% show altered ATM protein levels. Germline ATM sequence variants have been reported in breast cancer cases, however, it is difficult to fully evaluate the increased risk associated with their presence. The potential role of such variants needs to be further assessed, together with functional studies to model their impact on ATM function.

Cancer risks and mortality in heterozygous ATM mutation carriers

BACKGROUND

Homozygous or compound heterozygous mutations in the ATM gene are the principal cause of ataxia telangiectasia (A-T). Several studies have suggested that heterozygous carriers of ATM mutations are at increased risk of breast cancer and perhaps of other cancers, but the precise risk is uncertain.

METHODS

Cancer incidence and mortality information for 1160 relatives of 169 UK A-T patients (including 247 obligate carriers) was obtained through the National Health Service Central Registry. Relative risks (RRs) of cancer in carriers, allowing for genotype uncertainty, were estimated with a maximum-likelihood approach that used the EM algorithm. Maximum-likelihood estimates of cancer risks associated with three groups of mutations were calculated using the pedigree analysis program MENDEL. All statistical tests were two-sided.

RESULTS

The overall relative risk of breast cancer in carriers was 2.23 (95% confidence interval [CI] = 1.16 to 4.28) compared with the general population but was 4.94 (95% CI = 1.90 to 12.9) in those younger than age 50 years. The relative risk for all cancers other than breast cancer was 2.05 (95% CI = 1.09 to 3.84) in female carriers and 1.23 (95% CI = 0.76 to 2.00) in male carriers. Breast cancer was the only site for which a clear risk increase was seen, although there was some evidence of excess risks of colorectal cancer (RR = 2.54, 95% CI = 1.06 to 6.09) and stomach cancer (RR = 3.39, 95% CI = 0.86 to 13.4). Carriers of mutations predicted to encode a full-length ATM protein had cancer risks similar to those of people carrying truncating mutations.

CONCLUSION

These results confirm a moderate risk of breast cancer in A-T heterozygotes and give some evidence of an excess risk of other cancers but provide no support for large mutation-specific differences in risk.

Breast cancer in female carriers of ATM gene alterations: outcome of adjuvant radiotherapy

BACKGROUND AND PURPOSE

We analyzed the clinical outcome of breast cancer patients carrying sequence variants in the ATM gene who received postoperative radiotherapy after breast conservative surgery to test whether an increased cellular radiosensitivity may translate into enhanced tumor cell killing and thereby result in an improvement of the therapeutic ratio.

PATIENTS AND METHODS

We investigated a cohort of 138 breast cancer patients who received adjuvant radiotherapy following breast conservative surgery for T1 and T2 tumors. Genomic DNA samples of these patients had previously been scanned for mutations in the ATM gene. Follow-up data were available in 135 patients, with a median follow-up of 87 months. Local relapse-free, metastasis-free and overall survival were compared between carriers and non-carriers of a sequence variant in the ATM gene.

RESULTS

Twenty patients were found to carry a sequence variant in the ATM gene (truncating, 7; missense, 13). The actuarial 7-year local relapse-free survival of carriers vs. non-carriers were 88 vs. 94% (P=0.34). Actuarial metastasis-free and overall survival after 7 years were 63 vs. 85% (P=0.01) and 73 vs. 89% (P=0.055), respectively. However, the presence of a variant in the ATM gene did not remain a significant discriminator for metastasis-free survival in a multivariate Cox regression analysis (P=0.068).

CONCLUSIONS

Our results do not support the hypothesis that breast cancer patients carrying a sequence variant in the ATM gene differentially benefit from postoperative radiotherapy. These findings have to be verified using larger number of cases to clarify the clinical consequences of sequence variants in the ATM gene.

Immunoassay to measure ataxia-telangiectasia mutated protein in cellular lysates

BACKGROUND

Ataxia-telangiectasia (A-T) is a neurologic disorder caused by mutations in the ataxia-telangiectasia mutated (ATM) gene. A clinical diagnosis of A-T is confirmed by radiosensitivity testing and immunoblotting for ATM protein. Because both of these tests have long turnaround times (> or =3 months), we developed a rapid immunoassay to measure ATM protein and determined its sensitivity and specificity for diagnosing A-T.

METHODS

Recombinant ATM protein was used for standardization. Lysates of lymphoblastoid cell lines (LCLs) and peripheral blood mononuclear cells (PBMCs) from A-T patients, controls, and A-T heterozygotes were tested for ATM protein by immunoassay.

RESULTS

Between-run imprecision (CV) was < or =13%. Nuclear lysates from control LCLs and PBMCs had ATM protein concentrations of 49-610 microg/L and 48-943 microg/L, respectively. ATM protein was not detectable in LCL nuclear lysates from 18 of 21 A-T patients. The three remaining A-T patients had trace amounts of ATM protein, which was confirmed on immuoblots. ATM protein was also detectable in whole-cell lysates from 4 x 10(6) cells at concentrations of 64-463 microg/L and 42-444 microg/L for control LCLs and PBMCs, respectively. A-T heterozygotes had ATM protein concentrations of 52-98 microg/L. ATM protein was stable in PBMCs stored for 1 month at -70 degrees C, but rapidly decreased after 1 day in unprocessed blood.

CONCLUSIONS

This ATM protein immunoassay can be used to confirm a diagnosis of A-T in 2 days on small numbers of PBMCs and can potentially identify A-T carriers and individuals at increased risk for cancer.

Pattern of sequence variation across 213 environmental response genes

To promote the clinical and epidemiological studies that improve our understanding of human genetic susceptibility to environmental exposure, the Environmental Genome Project (EGP) has scanned 213 environmental response genes involved in DNA repair, cell cycle regulation, apoptosis, and metabolism for single nucleotide polymorphisms (SNPs). Many of these genes have been implicated by loss-of-function mutations associated with severe diseases attributable to decreased protection of genomic integrity. Therefore, the hypothesis for these studies is that individuals with functionally significant polymorphisms within these genes may be particularly susceptible to genotoxic environmental agents. On average, 20.4 kb of baseline genomic sequence or 86% of each gene, including a substantial amount of introns, all exons, and 1.3 kb upstream and downstream, were scanned for variations in the 90 samples of the Polymorphism Discovery Resource panel. The average nucleotide diversity across the 4.2 MB of these 213 genes is 6.7 x 10(-4), or one SNP every 1500 bp, when two random chromosomes are compared. The average candidate environmental response gene contains 26 PHASE inferred haplotypes, 34 common SNPs, 6.2 coding SNPs (cSNPs), and 2.5 nonsynonymous cSNPs. SIFT and Polyphen analysis of 541 nonsynonymous cSNPs identified 57 potentially deleterious SNPs. An additional eight polymorphisms predict altered protein translation. Because these genes represent 1% of all known human genes, extrapolation from these data predicts the total genomic set of cSNPs, nonsynonymous cSNPs, and potentially deleterious nonsynonymous cSNPs. The implications for the use of these data in direct and indirect association studies of environmentally induced diseases are discussed.