Intronic <Emphasis Type="Italic">TP53</Emphasis> Germline Sequence Variants Modify the Risk in German Breast/Ovarian Cancer Families

To establish the contribution of TP53 germline mutations to familial breast/ovarian cancer in Germany we screened the complete coding region of the TP53 gene in a series of German breast/ovarian cancer families negative for mutations in the BRCA1 and BRCA2 genes.Two different intronic TP53 sequence variants were identified in 6/48 (12.5%) breast/ovarian cancer families. A novel A to T nucleotide change at position 17708 in intron 10 segregating with the disease was detected in three breast cancer families (6.2%). One 17708 A>T-associated breast tumour showed loss of the wild-type allele. This variant was also found in 5/112 (4.5%) healthy controls indicating that it is a polymorphism. A second sequence variant changing a G to C at position 13964 in intron 6 not segregating with the disease was found in two breast cancer families and one breast-ovarian cancer family (6.2%). This variant has previously been shown to occur at an elevated frequency in hereditary breast cancer patients from North America and to be of functional importance leading to inhibition of apoptosis and prolongation of cell survival after DNA-damage. Screening of 185 consecutive unselected German breast cancer patients revealed the 13964 G>C variant in four patients (2.2%). Immunohistochemical analysis of the TP53 protein showed negative immunoreactivity in normal and tumour tissues of one 17708 A>T and six 13964 G>C carriers. TP53 overexpression was detected in the tumour tissue of one sporadic breast cancer patient carrying the 13964 G>C variant. Our results show that intronic changes of the TP53 gene may act as or be associated with risk modifiers in familial breast cancer.     

Mutation analysis of the CHK2 gene in families with hereditary breast cancer.

Recently CHK2 was functionally linked to the p53 pathway, and mutations in these two genes seem to result in a similar Li-Fraumeni syndrome (LFS) or Li-Fraumeni-like syndrome (LFL) multi-cancer phenotype frequently including breast cancer. As CHK2 has been found to bind and regulate BRCA1, the product of one of the 2 known major susceptibility genes to hereditary breast cancer, it also more directly makes CHK2 a suitable candidate gene for hereditary predisposition to breast cancer. Here we have screened 79 Finnish hereditary breast cancer families for germline CHK2 alterations. Twenty-one of these families also fulfilled the criteria for LFL or LFS. All families had previously been found negative for germline BRCA1, BRCA2 and TP53 mutations, together explaining about 23% of hereditary predisposition to breast cancer in our country. Only one missense-type mutation, Ile(157)-->Thr(157), was detected. The high Ile(157)--> Thr(157)mutation frequency (6.5%) observed in healthy controls and the lack of other mutations suggest that CHK2 does not contribute significantly to the hereditary breast cancer or LFL-associated breast cancer risk, at least not in the Finnish population. For Ile(157)--> Thr(157)our result deviates from what has been reported previously.     

Germline mutations of TP53 and BRCA2 genes in breast cancer/sarcoma families

The genetic aetiology of familial aggregations of breast cancer and sarcomas has been elucidated only in part. In this study, 23 unrelated individuals from families with one case of sarcoma and at least one case of breast cancer were screened for mutations in the TP53, BRCA1 and BRCA2 genes. Families were classified according to their conformity to the criteria defining the Li-Fraumeni syndrome (LFS), Li-Fraumeni-like (LFL) syndrome and hereditary breast/ovarian cancer (HBOC). Germline TP53 mutations were identified in three instances (13%), including one LFS and two LFL families, while none of the non-LFS/non-LFL families had a TP53 mutation. Three cases (13%), including one with a TP53 mutation, carried BRCA2 mutations. Of these, two were observed in LFL/HBOC families and the other one in a non-LFS/non-LFL/HBOC family, while none of the non-HBOC families tested positive. These findings suggest that the screening of BRCA2, in addition to TP53, may be appropriate for the molecular characterisation of breast cancer/sarcoma families, with practical implications for counselling and clinical management.     

BRCA1, BRCA2 and TP53 mutations in very early-onset breast cancer with associated risks to relatives

Pathological mutations in BRCA1, BRCA2 and TP53 are associated with an increased risk of breast cancer. This study evaluated mutation frequency of these genes in early-onset breast cancer patients, and correlated this with family history and determined relative risks to family members. Patients with breast adenocarcinoma diagnosed 30 years were ascertained between 1980 and 1997. Family history was established and mutation screening of BRCA1, BRCA2 and TP53 genes was performed. Estimates of penetrance and relative risk were undertaken. DNA was obtained from 100/139 women. 17/36 familial cases had a BRCA1, BRCA2 or TP53 mutation. Of 64 non-familial cases, one BRCA2, two BRCA1 and two TP53 mutations were detected. Penetrance estimates (by age 70) for breast cancer were 84% for BRCA1 mutations and 91% for BRCA2 mutations and for ovarian cancer, 60% and 26%, respectively. Relative risks associated with mutations were consistent with previous studies. BRCA1 and BRCA2 mutations in patients with breast cancer 30 years are predicted strongly by family history. The majority of families with ovarian cancer were due to mutations in BRCA1/2 whereas these mutations only accounted for 30-50% of the excess breast cancers.     

Germline TP53 mutations in BRCA1 and BRCA2 mutation-negative French Canadian breast cancer families

About 40% of French Canadian breast and/or ovarian cancer families harbor germline BRCA1 or BRCA1 mutations where common mutations account for about 84% of all mutations identified in cancer families. Within a series of BRCA1 and BRCA2 mutation-negative families, a germline TP53 13398 G>A (Arg213Gln) mutation was identified, which was selected for mutation analysis in this gene because of a family history consistent with Li–Fraumeni syndrome (LFS). Given the founder effects in this population, the 13398 G>A mutation was screened in series of 52 BRCA1 and BRCA2 mutation-negative cancer families, and a mutation-positive family was identified. However, pedigree inspection and expansion of mutation-positive families with the same mutation revealed that they were closely related to each other. To further characterize the contribution of TP53 in cancer families, mutation analysis was performed in the remaining BRCA1 and BRCA2 mutation-negative cancer families. Thirty sequence variants were identified, the majority of which occur in intronic sequences and are not predicted to affect the functionality of TP53. However, the 14538 G>A (Arg290His) mutation was identified in a family which did not exhibit features consistent with LFS or Li–Fraumeni-like (LFL) syndrome. Neither of the TP53 mutations was detected in 381 French Canadian women with breast cancer diagnosed before 50 years of age not selected for family history of cancer. In all, germline TP53 mutations were identified in two of 52 (3.8%) cancer families, suggesting that TP53 is not a major contributor to BRCA1 and BRCA2 mutation-negative breast and/or ovarian cancer families of French Canadian descent.     

Abnormality of the DNA double-strand-break checkpoint/repair genes, ATM, BRCA1 and TP53, in breast cancer is related to tumour grade

The role of the DNA double-strand-break (DSB) checkpoint/repair genes, ATM, BRCA1 and TP53, in sporadic breast cancer requires clarification, since ATM and BRCA1 mutations are rare in sporadic tumours. In an attempt to explain this phenomenon, we postulated that (i) in addition to genetic deletion, abnormal expression of DSB checkpoint/repair proteins might abolish the function of these genes and (ii) there might be a combined effect of individual defective genes during breast cancer pathogenesis. Using a largely homogenous group of 74 specimens of early-onset (< or =35 years of age) infiltrating ductal carcinomas, we examined associations between pathological grade and genetic deletion and/or abnormal protein expression of ATM, BRCA1 and TP53. The results showed that high-grade tumours displayed a high frequency of loss of heterozygosity (LOH) at, and/or abnormal expression of, ATM, BRCA1 and TP53. Multigenetic analysis showed abnormalities in BRCA1 to be independently associated with high-grade tumours. ATM and TP53 appeared to play an assistant role, abnormalities in these genes significantly increasing the possibility of poor differentiation in tumours with abnormalities in BRCA1. Furthermore, a higher number of abnormalities (LOH or abnormal expression) in these three genes correlated with poor tumour differentiation. Thus, this study suggests that combined changes in several DSB checkpoint/repair genes belonging to a common functional pathway are associated with breast cancer pathogenesis.     

A probability model for predicting BRCA1 and BRCA2 mutations in breast and breast-ovarian cancer families

Germline mutations in BRCA1 and BRCA2 genes predispose to hereditary breast and ovarian cancer. Our aim was to find associations between the clinical characteristics and positive mutation status in 148 breast cancer families in order to predict the probability of finding a BRCA mutation in a family. Several factors were associated with mutations in univariate analysis, whereas in multivariate analysis (logistic regression with backward selection) only the age of the youngest breast cancer patient and the number of ovarian cancer cases in a family were independent predictors of BRCA mutations. A logistic model was devised to estimate the probability for a family of harbouring a mutation in either BRCA1 or BRCA2. Altogether, 63 out of 148 families (43%) and 28 out of 29 (97%) mutation carrier families obtained probabilities over 10%. The mean probability was 55% for mutation-positive families and 11% for mutation-negative families. The models by Couch et al (1997) and Shattuck-Eidens et al (1997) previously designed for BRCA1 were also tested for their applicability to distinguish carrier families with mutations in either gene. The probability model should be a useful tool in genetic counselling and focusing the mutation analyses, and thus increasing also the cost-effectiveness of the genetic screening.     

BRCA1 and BRCA2 germline mutation spectrum and frequencies in Belgian breast/ovarian cancer families

Worldwide variation in the distribution of BRCA1 and BRCA2 mutations is well recognised, and for the Belgian population no comprehensive studies about BRCA1/2 mutation spectra or frequencies have been published. We screened the complete coding region of both genes in 451 individuals from 349 Belgian families referred to a family cancer clinic and identified 49 families with a BRCA1 and 26 families with a BRCA2 mutation. Six major recurrent mutations (BRCA1 IVS5+3A>G, 2478-2479insG, E1221X and BRCA2 IVS6+1G>A, 6503-6504delTT, 9132delC) accounted for nearly 60% of all mutations identified. Besides 75 true pathogenic mutations, we identified several variants of unknown clinical significance. In combination with a family history, an early average age of female breast cancer diagnosis (P<0.001), and the presence of a relative with ovarian cancer (P<0.0001) or multiple primary breast cancers (P=0.002), increased the chance for finding a mutation. Male breast cancer was indicative of a BRCA2 mutation segregating in the family (P=0.002). Mutations in the 5'-end of BRCA1 and BRCA2 were associated with a significantly increased risk for ovarian cancer relative to the central portion of the gene. Our study suggests a role for additional breast cancer susceptibility genes in the Belgian population, since mutation detection ratios were low in high-risk breast cancer-only families as compared to breast-ovarian cancer families. Given the large proportion of recurring mutations, molecular testing can now be organised in a more cost-effective way. Our data allow optimisation of genetic counselling and disease prevention in Belgian breast/ovarian cancer families.     

Mutations of the BRCA1 and BRCA2 genes in patients with bilateral breast cancer

Mutations of the BRCA1 or BRCA2 genes have been shown to strongly predispose towards the development of contralateral breast cancer in patients from large multi-case families. In order to test the hypothesis that BRCA1 and BRCA2 mutations are more frequent in patients with bilateral breast cancer, we have investigated a hospital-based series of 75 consecutive patients with bilateral breast cancer and a comparison group of 75 patients with unilateral breast cancer, pairwise matched by age and family history, for mutations in the BRCA1 and BRCA2 genes. Five frameshift deletions (517delGT in BRCA1; 4772delA, 5946delCT, 6174delT and 8138del5 in BRCA2) were identified in patients with bilateral disease. No further mutations, apart from polymorphisms and 3 rare unclassified variants, were found after scanning the whole BRCA1 and BRCA2 coding sequence. Three pathogenic BRCA1 mutations (Cys61Gly, 3814del5, 5382insC) were identified in the group of patients with unilateral breast cancer. The frequencies of common BRCA1 and BRCA2 missense variants were not different between the 2 groups. In summary, we did not find a significantly increased prevalence of BRCA1 and BRCA2 mutations in a hospital-based cohort of German patients with bilateral breast cancer. We conclude that bilaterality of breast cancer on its own is not strongly associated with BRCA1 and BRCA2 mutations when adjusted for age and family history. The high frequency of bilateral disease in multi-case breast cancer families may be due to a familial aggregation of additional susceptibility factors modifying the penetrance of BRCA1 and BRCA2 mutations.     

Selected Aspects of Molecular Diagnostics of Constitutional Alterations in <Emphasis Type="Italic">BRCA1</Emphasis> and <Emphasis Type="Italic">BRCA2</Emphasis> Genes Associated with Increased Risk of Breast Cancer in the Polish Population

Objectives

This study was undertaken to determine: 1) Type and prevalence of founder mutations BRCA1 and BRCA2 genes in Polish families with strong aggregation of breast and/or ovarian cancer. 2) Risk of breast and/or ovarian cancer depending on type of BRCA1 gene mutation. 3) Prevalence of BRCA1 mutation and of other alleles presumably linked with predisposition to breast cancer in unselected Polish patients with breast cancer. 4) Risk of breast cancer in patients with 5972C/T polymorphism that alters the BRCA2 protein structure.

Summary of the results

1. Among 66 families from several regions in Poland with a strong aggregation of breast/ovarian cancer, founder mutation of the BRCA1 gene were disclosed in 34 families and of the BRCA2 gene in on family. Altogether, seven different mutations were disclosed. Five mutations were found in at least two families in this group. The most frequent mutation was 5382insC (18 families), followed by C61G (7 families) and 4153delA (4 families). 2. Among 200 families representative for Poland with strong aggregation of breast/ovarian cancer, mutation of the BRCA1 gene were found in 122 families (61%) and of the BRCA2 gene in seven families (3,5%). 119 out of 122 mutations of the BRCA1 gene (97,5%) were repeatable. Three recurrent mutations of the BRCA1 gene (5382insC, C61G, 4153delA) characteristic for the Polish population were disclosed in 111 families representing 86% of all pathogenic sequences of this gene. 3. The risk of ovarian cancer in carriers of the three most frequent recurrent mutation of the BRCA1 gene in Poland is similar (OR 43.6 for 5382insC and 50 for 4153delA). The risk of breast cancer is significantly different for 4153delA (OR 1) and for other mutations (OR 10.9). 4. Among 2012 unselected breast cancers diagnosed in hospitals of nine Polish cities, mutations of the BRCA1 gene (5382insC, C61G, 4153delA) were disclosed in 2.9% patients. CHEK2 alternation (1100delC, IVS2+1G>A, I157T) was discovered in 8.1% and NBS1 mutation (657del5) in 0.8% of the patients. The changes were more frequent in the study than the control group. However, the risk of breast cancer was significantly higher for only three of them. Two changes, namely 5382insC and C61G of the BRCA1 gene revealed a high penetrance (OR 6.2 and 15.0, respectively), while I157T of the CHEK2 gene was associated with a low risk of breast cancer (OR 1.4). Mutations of the BRCA1, CHEK2 and NSB1 genes were significantly more frequent in patients with breast cancer diagnosed prior to 50 years of age. The mean age at diagnosis was 47.2 years for carriers of the BRCA1 mutation, 50.7 years for NBS1 and 54.2 for CHEK2. The mean age at diagnosis in the group of patients without any if the mutations described above was 56.1 years. When breast cancer patients with the diagnosis before and after 50 years of age were compared, the greatest difference in the frequency of mutation was revealed for the BRCA1 gene (5.5% vs 1.5%).BRCA1 mutations were significantly more frequent I familial aggregates of the tumor (10.8%), but were also present in sporadic cases (1.8%). For the CHEK2 and NBS1 genes, there was no correlation between frequency and family history of cancer in probands. 5. A higher frequency of heterozygous carriers of 5972C/T polymorphism of the BRCA2 gene was demonstrated for breast cancer prior to 50 years of age (OR 1.4). the risk of breast cancer prior to 50 years of age was particularly high in 5972T/T homozygote (OR 4.7). This polymorphism was associated with breast cancer notable for intraductal growth.

Conclusions

1. Efficient molecular diagnostics of genetic predisposition to breast/ovarian cancer in Poland could be based on relatively simple tests disclosing some of the most frequent recurrent mutations of the BRCA1 gene. 2. The risk of breast cancer seems to be only slightly higher in carriers of some BRCA1 gene mutations. This finding should be taken into account during work on prevention schemes for carriers of the BRCA1 mutations. 3. 5382insC and C61G mutations of the BRCA1 gene are linked with high risk of breast cancer. Changes in the CHEK2 and NBS1 genes appear to be linked with a higher risk of breast cancers, particularly at young age. However, penetrance in this case is low. All patients with breast cancer should be tested for BRCA1 gene mutations because the percentage of mutations is also high in patients older than 50 years of age or without familiar aggregation of breast/ovarian cancer. 4. Polymorphic changes in the BRCA2 gene sequence previously regarded as non-pathogenic may nevertheless predispose, homozygotes in particular, to breast cancer. Apparently, the recessive character of these changes is responsible for the negative family history in most cases. The use of DNA tests is the only way to disclose increased risk of breast cancer in carriers of the 5972T/T mutation.

     

Mutational profiling of familial male breast cancers reveals similarities with luminal A female breast cancer with rare TP53 mutations

Background:

Male breast cancer (MBC) is still poorly understood with a large proportion arising in families with a history of breast cancer. Genomic studies have focused on germline determinants of MBC risk, with minimal knowledge of somatic changes in these cancers.

Methods:

Using a TruSeq amplicon cancer panel, this study evaluated 48 familial MBCs (3 BRCA1 germline mutant, 17 BRCA2 germline mutant and 28 BRCAX) for hotspot somatic mutations and copy number changes in 48 common cancer genes.

Results:

Twelve missense mutations included nine PIK3CA mutations (seven in BRCAX patients), two TP53 mutations (both in BRCA2 patients) and one PTEN mutation. Common gains were seen in GNAS (34.1%) and losses were seen in GNAQ (36.4%), ABL1 (47.7%) and ATM (34.1%). Gains of HRAS (37.5% vs 3%, P=0.006), STK11 (25.0% vs 0%, P=0.01) and SMARCB1 (18.8% vs 0%, P=0.04) and the loss of RB1 (43.8% vs 13%, P=0.03) were specific to BRCA2 tumours.

Conclusions:

This study is the first to perform high-throughput somatic sequencing on familial MBCs. Overall, PIK3CA mutations are most commonly seen, with fewer TP53 and PTEN mutations, similar to the profile seen in luminal A female breast cancers. Differences in mutation profiles and patterns of gene gains/losses are seen between BRCA2 (associated with TP53/PTEN mutations, loss of RB1 and gain of HRAS, STK11 and SMARCB1) and BRCAX (associated with PIK3CA mutations) tumours, suggesting that BRCA2 and BRCAX MBCs may be distinct and arise from different tumour pathways. This has implications on potential therapies, depending on the BRCA status of MBC patients.     

Genetic testing in a cohort of young patients with HER2-amplified breast cancer

BackgroundYoung age at diagnosis for breast cancer raises the question of genetic susceptibility. We explored breast cancer susceptibility genes testing on ≤40-year-old patients with HER2-amplified invasive breast cancer.Patients and methodsPatients were selected from a large UK cohort study. The inclusion criterion was age ≤40 at diagnosis with confirmed HER2-amplified breast cancer. The probability of finding a BRCA gene mutation was calculated based on family history. Genetic testing used was either clinical testing for BRCA1 and BRCA2, with a subset also tested for TP53 mutations, or research-based testing using a typical panel comprising 17 breast cancer susceptibility genes (CSGs) including BRCA1, BRCA2 and TP53.ResultsOf the 591 eligible patients, clinical testing results were available for 133 cases and an additional 263 cases had panel testing results. BRCA testing across 396 cases found 8 BRCA2 (2%) and 6 BRCA1 (2%) pathogenic mutations. Of the 304 patients tested for TP53 mutations, overall 9 (3%) had deleterious TP53 mutations. Of the 396 patients, 101 (26%) met clinical criteria for BRCA testing (≥10% probability), among whom 11% had pathogenic BRCA mutations (6 BRCA2, 5 BRCA1). Where the probability was calculated to be <10%, only 4 of 295 (1%) patients had BRCA mutations. Among the 59 patients who had TP53 testing meeting the 10% threshold, 7 had mutations (12%). Likely functionally deleterious mutations in 14 lower penetrance CSGs were present in 12 of 263 (5%) panel-tested patients.ConclusionPatients aged <41 at diagnosis with HER2+ breast cancer and no family history of breast cancer can be reassured that they have a low chance of being a high-risk gene carrier. If there is a strong family history, not only BRCA but also TP53 gene testing should be considered. The clinical utility of testing lower penetrance CSGs remains unclear.     

The prevalence of germ-line TP53 mutations in women diagnosed with breast cancer before age 30

Germ-line mutations in the TP53 gene are rare, but predispose women to a range of cancer types, including early-onset breast cancer. Breast cancers in women from families with the Li-Fraumeni syndrome often occur before age 30. The prevalence of deleterious TP53 mutations in unselected women with early-onset breast cancer is not precisely known. If mutations were found to be sufficiently common, it might be prudent to offer genetic testing to affected women in this age group. We screened the entire TP53 gene in the germ-line DNA from 95 women of various ethnic groups who were diagnosed with breast cancer before age 30, and who had previously been found to be negative for BRCA1 and BRCA2 mutations. No TP53 mutation was found. This study does not support a policy that TP53 testing should be offered routinely to unselected women with early-onset breast cancer in the absence of a family history of cancer.     

TP53 mutations in breast cancer associated with BRCA1 or BRCA2 germ-line mutations: distinctive spectrum and structural distribution

Several groups have studied the molecular pathology of inherited breast cancer. By combining several such studies, we show in this study that somatic TP53 abnormalities are more common in breast cancer associated with BRCA1 or BRCA2 germ-line mutations than in sporadic breast cancers (odds ratio, 2.8; P = 0.0003). Then, we compared the spectrum of TP53 mutations for breast cancers in the IARC TP53 mutation database with the 82 mutations reported in BRCA1/2-associated breast cancers. The spectrum differed significantly both in distribution (P < 1 x 10(-6)) and in base changes (P = 0.025). Mutations at A:T bp were more common in BRCA1/2-associated tumors and strand bias suggesting DNA repair abnormalities was found. Changes were common at TP53 codons that are not mutation hotspots. Structural modeling showed that most of these p53 non-hotspot amino acids characterized in breast tumors isolated from patients with deficient BRCA1/2 function are distributed in a region of the protein on the opposite side of the p53 DNA-binding surface. Our results suggest that BRCA1/2 mutations influence the type and distribution of TP53 mutations seen in breast cancer.     

<Emphasis Type="Italic">TP53</Emphasis> p.R337H prevalence in a series of Brazilian hereditary breast cancer families

Background

Approximately 5-10% of breast cancers are hereditary. Among hereditary syndromes, Hereditary Breast and Ovarian Cancer Syndrome (HBOC) and Li-Fraumeni Syndrome (LFS) have received the most attention. HBOC is due to mutations in the BRCA1 and BRCA2 genes and is characterized by breast adenocarcinoma and/or epithelial ovarian carcinoma. LFS is associated with germline mutations in TP53; the most frequent cancer types associated with this syndrome are sarcoma, breast cancer, leukemia, brain tumors and adrenocortical carcinomas. Other cancers related to LFS are found at lower frequencies. In Brazil, especially in the southern part of the country, a specific mutation in the TP53 gene, TP53 p.R337H, occurs at a high frequency in childhood adrenocortical tumors. It has been proposed that this mutation increases breast cancer risk in southern Brazilian women.

Methods

We carried out a case-control study to determine the prevalence of the TP53 p.R337H mutation in 28 female cancer patients attended at the Cancer Genetic Counseling Service of the General Hospital of the University of São Paulo Medical School of Ribeirão Preto who fulfilled Hereditary Breast and Ovary Cancer Syndrome genetic test criteria compared to healthy woman (controls). TP53 p.R337H mutation status was determined using the High Resolution Melting (HRM) method, followed by DNA sequencing. Fisher’s test was used to compare the prevalence of TP53 p.R337H in the patient and control groups.

Results

Two of the breast cancer cases (7.1%) and none of the controls carried the TP53 p.R337H mutation. At the time of the investigation, both cases fulfilled testing criteria for Hereditary Breast and Ovary Cancer Syndrome but not Li-Fraumeni or Li-Fraumeni-like Syndrome, based on genetic testing criteria of NCCN Clinical Practice Guidelines in Oncology (v.1.2010).

Conclusions

We suggest that genetic screening of Brazilian breast cancer patients who fulfill Hereditary Breast and Ovary Cancer Syndrome criteria and have a family history that includes other tumors of the LFS/LFL spectrum be tested for the TP53 p.R337H mutation.

     

Identification of the prevalent BRCA1 and BRCA2 mutations in the female population of Puerto Rico

Mutations in the breast cancer 1, early onset (BRCA1) and breast cancer 2 (BRCA2) genes are responsible for the majority of hereditary breast cancers. Knowledge of the incidence and prevalence of BRCA mutations in a specific population or ethnic group is necessary to provide accurate genetic counseling for breast cancer patients and their families; however, these data have not been gathered in the population of Puerto Rico. We conducted a retrospective study of female breast cancer patients undergoing genetic testing for BRCA mutations in the highest-volume breast surgery practices in San Juan, Puerto Rico. Data collection includes three-generation family cancer history and results from complete BRCA sequencing. A total of six different deleterious mutations were observed, including one mutation in BRCA1 and five mutations in BRCA2. Three recurrent mutations (BRCA1 del exon1-2, BRCA2 4150G>T, and BRCA2 6027del4) account for over 70% of all the BRCA mutations observed in this study population. This study examines for the first time the characteristics of hereditary breast cancer in Puerto Rico and assesses the accuracy of existing genetic risk assessment tools in that population. This data is expected to contribute to providing accurate and efficient tools for the clinical management of hereditary breast cancer in Puerto Rico.     

The TP53 Arg72Pro and MDM2 309G>T polymorphisms are not associated with breast cancer risk in BRCA1 and BRCA2 mutation carriers

Background:

The TP53 pathway, in which TP53 and its negative regulator MDM2 are the central elements, has an important role in carcinogenesis, particularly in BRCA1- and BRCA2-mediated carcinogenesis. A single nucleotide polymorphism (SNP) in the promoter region of MDM2 (309T>G, rs2279744) and a coding SNP of TP53 (Arg72Pro, rs1042522) have been shown to be of functional significance.

Methods:

To investigate whether these SNPs modify breast cancer risk for BRCA1 and BRCA2 mutation carriers, we pooled genotype data on the TP53 Arg72Pro SNP in 7011 mutation carriers and on the MDM2 309T>G SNP in 2222 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). Data were analysed using a Cox proportional hazards model within a retrospective likelihood framework.

Results:

No association was found between these SNPs and breast cancer risk for BRCA1 (TP53: per-allele hazard ratio (HR)=1.01, 95% confidence interval (CI): 0.93–1.10, P_trend=0.77; MDM2: HR=0.96, 95%CI: 0.84–1.09, P_trend=0.54) or for BRCA2 mutation carriers (TP53: HR=0.99, 95%CI: 0.87–1.12, P_trend=0.83; MDM2: HR=0.98, 95%CI: 0.80–1.21, P_trend=0.88). We also evaluated the potential combined effects of both SNPs on breast cancer risk, however, none of their combined genotypes showed any evidence of association.

Conclusion:

There was no evidence that TP53 Arg72Pro or MDM2 309T>G, either singly or in combination, influence breast cancer risk in BRCA1 or BRCA2 mutation carriers.     

Identification of a founder BRCA2 mutation in Sardinia

Sardinian population can be instrumental in defining the molecular basis of cancer, using the identity-by-descent method. We selected seven Sardinian breast cancer families originating from the northern-central part of the island with multiple affected members in different generations. We genotyped 106 members of the seven families and 20 control nuclear families with markers flanking BRCA2 locus at 13q12-q13. The detection of a common haplotype shared by four out of seven families (60%) suggests the presence of a founder BRCA2 mutation. Direct sequencing of BRCA2 coding exons of patients carrying the shared haplotype, allowed the identification of a 'frame-shift' mutation at codon 2867 (8765delAG), causing a premature termination-codon. This mutation was found in breast cancer patients as well as one prostate and one bladder cancer patient with shared haplotype. We then investigated the frequency of 8765delAG in the Sardinian breast cancer population by analysing 270 paraffin-embedded normal tissue samples from breast cancer patients. Five patients (1.7%) were found to be positive for the 8765delAG mutation. Discovery of a founder mutation in Sardinia through the identity-by-descent method demonstrates that this approach can be applied successfully to find mutations either for breast cancer or for other types of tumours.     

Genes implicated in hereditary breast cancer syndromes

The medical histories of breast cancer-prone families have been described for over a century. The pattern of breast cancer occurrences in these families is most consistent with an autosomal dominant mode of inheritance. The location of a gene that could explain the pattern of transmission of the breast cancer trait in families averaging early (pre-menopausal) onset of breast cancer was reported in 1990. Since then, two genes have been identified: BRCA1 and BRCA2. Germ-line mutations in these two genes confer susceptibility to breast (female and male) and ovarian cancer, and account for a significant proportion of hereditary breast cancer in two cancer syndromes: site-specific breast cancer and the breast-ovarian cancer syndrome. Other hereditary syndromes that feature breast cancer are Li-Fraumeni syndrome, Cowden disease, and ataxia telangiectasia, whose carriers have been shown to harbor germ-line mutations in TP53, PTEN, and ATM, respectively. There may be other genetic factors that contribute to hereditary breast cancer, since not all families with multiple cases of breast cancer harbor germ-line BRCA1 or BRCA2 mutations. Host factors (such as lifestyle choices) and other genes may modulate risk of breast cancer in mutation carriers.