Familial breast cancers without mutations in BRCA1 or BRCA2 have low cyclin E and high cyclin D1 in contrast to cancers in BRCA mutation carriers.

PURPOSE: We analyzed the expression of critical cell cycle regulators cyclin E and cyclin D1 in familial breast cancer, focusing on BRCA mutation-negative tumors. Cyclin E expression in tumors of BRCA1 or BRCA2 carriers is higher, and cyclin D1 expression lower, than in sporadic tumors. In familial non-BRCA1/2 tumors, cyclin E and cyclin D1 expression has not been studied. EXPERIMENTAL DESIGN: Cyclin E and cyclin D1 immunohistochemical expression was studied in tissue microarrays consisting of 53 BRCA1, 58 BRCA2, 798 familial non-BRCA1/2, and 439 sporadic breast tumors. RESULTS: In univariate analysis, BRCA1 tumors had significantly more frequently high cyclin E (88%) and low cyclin D1 (84%) expression than sporadic (54% and 49%, respectively) or familial non-BRCA1/2 (38% and 45%, respectively) tumors. BRCA2 tumors had significantly more frequently low cyclin D1 expression (68%) than sporadic or familial non-BRCA1/2 tumors and significantly more frequently high cyclin E expression than familial non-BRCA1/2 tumors. In a logistic regression model, cyclin expression, early age of onset, and estrogen receptor (ER) and human epidermal growth factor receptor-2 (HER2) status were the independent factors most clearly distinguishing tumors of BRCA1 mutation carriers from other familial breast cancers. High cyclin E and low cyclin D1 expression were also independent predictors of BRCA2 mutation when compared with familial non-BRCA1/2 tumors. Most interestingly, lower frequency of high cyclin E expression independently distinguished familial non-BRCA1/2 tumors also from sporadic ones. CONCLUSIONS: Cyclin E and cyclin D1 expression distinguishes non-BRCA1/2 tumors from both sporadic and BRCA1- and BRCA2-associated tumors and may reflect different predisposition and pathogenesis in these groups.     

The pathology of familial breast cancer: histological features of cancers in families not attributable to mutations in BRCA1 or BRCA2.

Breast cancers arising in carriers of mutations in the breast cancer susceptibility genes, BRCA1 and BRCA2, differ histologically from each other and from breast cancers unselected for a family history. However, a substantial proportion of families with multiple cases of breast cancer is not attributable to these two genes (non-BRCA1/2 families). We have now characterized the pathology of 82 breast cancers from non-BRCA1/2 families. Breast cancers in non-BRCA1/2 families were of lower grade (P = 0.0018), showed fewer mitoses (P < 0.0001), less nuclear pleomorphism (P = 0.0014), less lymphocytic infiltrate (P < 0.0001), a lesser extent of the tumor with a continuous pushing margin (P = 0.004), a lesser extent of the tumor composed of solid sheets of cells (P = 0.0047), less necrosis (P = 0.002), and wereparison with BRCA2 tumors, non-BRCA1/2 tumors were lower grade (P = 0.017) and exhibited less pleomorphism (P = 0.01) and more tubule formation (P = 0.05). In comparison with control breast cancers unselected for a family history of the disease, non-BRCA1/2 tumors were of significantly lower grade (P = 0.001), showed less pleomorphism (P = 0.0002), and had a lower mitotic count (P = 0.003). The results indicate that non-BRCA1/2 breast cancers differ histologically from both BRCA1 and BRCA2 breast cancers and are overall of lower grade. They also suggest that non-BRCA1/2 breast cancers differ from nonfamilial breast cancers, but these differences may be attributable to various types of bias.     

Basal cytokeratins in breast tumours among BRCA1, BRCA2 and mutation-negative breast cancer families

Introduction

Finding new immunohistochemical markers that are specific to hereditary breast cancer could help us to select candidates for BRCA1/BRCA2 mutation testing and to understand the biological pathways of tumour development.

Methods

Using breast cancer tumour microarrays, immunohistochemical expression of cytokeratin (CK)-5/6, CK-14 and CK-17 was evaluated in breast tumours from BRCA1 families (n = 46), BRCA2 families (n = 40), non-BRCA1/BRCA2 families (n = 358) and familial breast cancer patients with one first-degree relative affected by breast or ovarian cancer (n = 270), as well as from patients with sporadic breast cancer (n = 364). Staining for CK-5/6, CK-14 and CK-17 was compared between these groups and correlated with other clinical and histological factors.

Results

CK-5/6, CK-14 and CK-17 were detected mostly among oestrogen receptor (ER)-negative, progesterone receptor (PR)-negative and high-grade tumours. We found the highest percentages of samples positive for these CKs among ER-negative/HER2-negative tumours. In univariate analysis, CK-14 was significantly associated with tumours from BRCA1 (39%; P < 0.0005), BRCA2 (27%; P = 0.011), and non-BRCA1/BRCA2 (21%; P < 0.005) families, as compared with sporadic tumours (10%). However, in multivariate analysis, CKs were not found to be independently associated with BRCA1 or BRCA2 mutation status, and the most effective predictors of BRCA1 mutations were age at onset, HER2 status, and either ER or PR status.

Conclusion

Although our study confirms that basal CKs can help to identify BRCA1 mutation carriers, this effect was weaker than previously suggested and CKs did not independently predict BRCA1 mutation either from sporadic or familial breast cancer cases. The most effective, independent predictors of BRCA1 mutations were age at onset, HER2 status, and either ER or PR status, as compared with sporadic or non-BRCA1/BRCA2 cancers.     

Germline BRCA1 mutations and a basal epithelial phenotype in breast cancer

A basal epithelial phenotype is found in not more than 15% of all invasive breast cancers. Microarray studies have shown that this phenotype is associated with breast cancers that express neither estrogen receptor (ER) nor erbB-2 (HER2/neu) (i.e., ER/erbB-2-negative tumors). The ER/erbB-2- negative phenotype is also found in breast cancers occurring in BRCA1 mutation carriers (i.e., BRCA1-related breast cancers). We tested the hypothesis that BRCA1-related breast cancers are more likely than non-BRCA1/ 2-related breast cancer to express a basal epithelial phenotype. Among 292 breast cancer specimens previously analyzed for ER, erbB-2, p53, and germline mutations in BRCA1 and BRCA2, we identified 76 that did not overexpress ER or erbB-2. Of the 72 specimens with sufficient material for testing, 40 expressed stratified epithelial cytokeratin 5 and/or 6 (5/6). In univariate analysis, the expression of cytokeratin 5/6 was statistically significantly associated with BRCA1-related breast cancers (odds ratio = 9.0, 95% confidence interval = 1.9 to 43; P =.002, two-sided Fisher's exact test). Thus, germline BRCA1 mutations appear to be associated with a distinctive breast cancer phenotype.     

Immunohistochemical expression of DNA repair proteins in familial breast cancer differentiate BRCA2-associated tumors.

PURPOSE: Morphologic and immunohistochemical studies of familial breast cancers have identified specific characteristics associated with BRCA1 mutation-associated tumors when compared with BRCA2 and non-BRCA1/2 tumors, but have not identified differences between BRCA2 and non-BRCA1/2 tumors. Because BRCA1 and BRCA2 genes participate in the DNA repair pathway, we have performed an immunohistochemical study with markers related to this pathway to establish the profile of the three groups. MATERIALS AND METHODS: We have studied two tissue microarrays that include 103 familial and 104 sporadic breast tumors, with a panel of DNA repair markers including ATM, CHEK2, RAD51, RAD50, XRCC3, and proliferating cell nuclear antigen. RESULTS: We found more frequent expression of CHEK2 in BRCA1 and BRCA2 tumors than in non-BRCA1/2 and sporadic tumors. We found absence of nuclear expression and presence of cytoplasmic expression of RAD51 in BRCA2 tumors that differentiate them from other familial tumors. We validated these results with a new series of patient cases. The final study with 253 familial patient cases (74 BRCA1, 71 BRCA2, 108 non-BRCA1/2), and 288 sporadic patient cases, has allowed us to confirm our preliminary results. Because BRCA2 tumors present a specific immunohistochemical profile for RAD51 and CHEK2 markers that is different from non-BRCA1/2 tumors, we have built a multivariate model with these markers that distinguish both tumors with an estimated probability of at least 76%. CONCLUSION: Our results suggest that BRCA2 tumors demonstrate more cytoplasmic and less nuclear RAD51 staining, and increased CHEK2 staining. This pattern may distinguish BRCA2 from familial non-BRCA1/2 tumors.     

High risk of contralateral breast carcinoma in women with hereditary/familial non-BRCA1/BRCA2 breast carcinoma

BACKGROUND: The objectives of the current study were to estimate the risk of developing contralateral breast carcinoma (CBC) among women with hereditary/familial non-BRCA1/BRCA2 breast carcinoma and to determine the factors that may predict their risk of CBC. METHODS: The study sample consisted of all families (n = 217 families) that were referred between 1994-2001 to the Clinic of Cancer Genetics at the University Hospital of Ume? for suspected hereditary breast carcinoma. The study included all women in the 217 families who had carcinoma of the breast as their first primary invasive malignancy diagnosed between 1970-2001 in northern Sweden. Exclusion criteria were an estimated lifetime risk < 20%, BRCA1/BRCA2 mutation, noninvasive carcinoma (ductal or lobular carcinoma in situ), and bilateral breast carcinoma. In the final analysis, 204 women were included from 120 families. RESULTS: The cumulative probability of developing CBC among women who had hereditary/familial non-BRCA1/BRCA2 breast carcinoma after 20 years was 27.3% (95% confidence interval, 15.0-37.8) compared with the expected risk (4.9%) among women in northern Sweden who had primary breast carcinoma. A significantly increased risk of CBC was associated with age younger than 50 years at the time of diagnosis of the first primary breast carcinoma (P = 0.006). Adjuvant hormone therapy reduced the risk of CBC (P = 0.036). CONCLUSIONS: Women with hereditary/familial non-BRCA1/BRCA2 breast carcinoma had a high risk of developing CBC. This risk was attenuated further among women who were younger at the time of onset, who had a cumulative probability of developing CBC of nearly 40% after 15 years, which is similar to the estimated risk among BRCA1/BRCA2 mutation carriers. The results of this study emphasized the importance of genetic counseling for these women.     

RASSF1A polymorphism A133S is associated with early onset breast cancer in BRCA1/2 mutation carriers

The tumor suppressor gene RASSF1A regulates cell cycle progression, apoptosis, and microtubule stability and is inactivated by promoter methylation in approximately 50% of breast cancers. It has been shown previously that the polymorphism A133S in RASSF1A reduces its ability to regulate cell cycle progression and this polymorphism is associated with an increased risk of breast cancer. We analyzed the frequency of RASSF1A A133S in 190 Caucasian women without breast cancer and 653 patients with breast cancer including 138 BRCA1 and BRCA2 (BRCA1/2) mutation carriers, 395 non-BRCA1/2 mutations carriers, and 120 untested for BRCA1/2 mutations. Patients with breast cancer had a higher frequency of A133S than the controls [P = 0.017; odds ratios (OR), 1.71; 95% confidence intervals (95% CI), 1.10-2.66]. There is also a higher frequency of A133S in patients with higher familial breast cancer risk (P = 0.029; OR, 1.76; 95% CI, 1.06-2.92) and patients carrying BRCA1/2 mutations (P = 0.037, OR, 1.82; 95% CI, 1.04-3.18). Importantly, we found that the co-occurrence of a BRCA1 or BRCA2 mutation and A133S in RASSF1A was associated with earlier onset of breast cancer compared with those individuals with either a BRCA1/2 mutation or the A133S polymorphism alone (36.0 versus 42.0 years old, P = 0.002). Our data suggest that the presence of the RASSF1A A133S polymorphism is associated with breast cancer pathogenesis in general and modifies breast cancer age of onset in BRCA1/2 mutations carriers. Our results warrant a large-scale study to examine the effect of the A133S polymorphism in the development of breast and other types of cancers.     

Aurora-A amplification associated with BRCA2 mutation in breast tumours

Potential interaction of Aurora-A amplification and BRCA2 mutation was examined in breast tumours from BRCA2 999del5 mutation carriers (n=20) and non-carriers (n=41). Aurora-A amplification studied by FISH was significantly more common in breast tumours from BRCA2 mutation carriers (p=0.0005). Extensive Aurora-A amplification was also detected on metaphase chromosomes in three breast epithelial cell lines with the same BRCA2 mutation. In addition, significant association was found between Aurora-A amplification and TP53 mutations in non-BRCA2 mutation carrier tumours (p=0.007). These results suggest that breast tumours with mutations in BRCA2 or TP53 could be promising candidates for Aurora-A targeted treatment.     

Risk of breast cancer recurrence and contralateral breast cancer in relation to BRCA1 and BRCA2 mutation status following breast-conserving surgery and radiotherapy

BRCA1 and BRCA2 germline mutations are associated with a strong risk of breast cancer, which may preclude breast-conserving treatment in carriers. This study examined whether mutation status influenced the rate of breast cancer recurrence following breast-conserving treatment. BRCA1 and BRCA2 genes were screened for germline mutations in 131 patients with a family history of breast and/or ovarian cancer, who had been treated with breast-conserving surgery and radiotherapy. The 131 patients with familial history were matched to 261 patients without, according to age at diagnosis and year of treatment. The follow-up of controls was at least equal to the time-interval between diagnosis and genetic testing in familial cases. Matched cohorts were compared according to rates of breast cancer recurrence as first event and contralateral breast cancer using log-rank tests. BRCA1/2 mutations were found in 20.6% patients with a family history. Nineteen patients had a BRCA1 mutation and 8 had a BRCA2 mutation. Breast cancers in mutation carriers were more often grade III (p<10-4) and oestrogen receptor negative (p=0.005) than tumours in both non-carriers and controls. Median follow-up for all 392 patients was 8.75 years. No significant differences in breast cancer recurrence as first event were seen between BRCA1/2 tumours and controls (p=0.47), carriers and non-carriers with a family history (p=0.96), or non-carriers and controls (p=0.10). On multivariate analysis, age was the most important factor significantly predicting for breast cancer recurrence. The rate of contralateral breast cancer was significantly increased in all patients with a family history: BRCA1/2 carriers versus controls (p=0.0003), non-carriers versus controls (p=0.0034) and carriers versus non-carriers (p=0.02). At a 9-year median follow-up, the rate of ipsilateral breast cancer recurrence was not higher in BRCA1 and BRCA2 mutation carriers than in non-carriers with a family history or sporadic cases. These results support the hypothesis that breast tumours in BRCA carriers are more sensitive to radiation. Therefore, breast-conserving treatment can be offered to these patients. However, longer follow-up is needed to ensure that the rate of new primary cancer in the treated breast does not increase in the long-term.     

A comprehensive model for familial breast cancer incorporating BRCA1, BRCA2 and other genes

In computing the probability that a woman is a BRCA1 or BRCA2 carrier for genetic counselling purposes, it is important to allow for the fact that other breast cancer susceptibility genes may exist. We used data from both a population based series of breast cancer cases and high risk families in the UK, with information on BRCA1 and BRCA2 mutation status, to investigate the genetic models that can best explain familial breast cancer outside BRCA1 and BRCA2 families. We also evaluated the evidence for risk modifiers in BRCA1 and BRCA2 carriers. We estimated the simultaneous effects of BRCA1, BRCA2, a third hypothetical gene 'BRCA3', and a polygenic effect using segregation analysis. The hypergeometric polygenic model was used to approximate polygenic inheritance and the effect of risk modifiers. BRCA1 and BRCA2 could not explain all the observed familial clustering. The best fitting model for the residual familial breast cancer was the polygenic, although a model with a single recessive allele produced a similar fit. There was also significant evidence for a modifying effect of other genes on the risks of breast cancer in BRCA1 and BRCA2 mutation carriers. Under this model, the frequency of BRCA1 was estimated to be 0.051% (95% CI: 0.021-0.125%) and of BRCA2 0.068% (95% CI: 0.033-0.141%). The breast cancer risk by age 70 years, based on the average incidence over all modifiers was estimated to be 35.3% for BRCA1 and 50.3% for BRCA2. The corresponding ovarian cancer risks were 25.9% for BRCA1 and 9.1% for BRCA2. The findings suggest that several common, low penetrance genes with multiplicative effects on risk may account for the residual non-BRCA1/2 familial aggregation of breast cancer. The modifying effect may explain the previously reported differences between population based estimates for BRCA1/2 penetrance and estimates based on high-risk families.     

Common breast cancer susceptibility alleles are associated with tumour subtypes in BRCA1 and BRCA2 mutation carriers: results from the Consortium of Investigators of Modifiers of BRCA1/2

Introduction

Previous studies have demonstrated that common breast cancer susceptibility alleles are differentially associated with breast cancer risk for BRCA1 and/or BRCA2 mutation carriers. It is currently unknown how these alleles are associated with different breast cancer subtypes in BRCA1 and BRCA2 mutation carriers defined by estrogen (ER) or progesterone receptor (PR) status of the tumour.

Methods

We used genotype data on up to 11,421 BRCA1 and 7,080 BRCA2 carriers, of whom 4,310 had been affected with breast cancer and had information on either ER or PR status of the tumour, to assess the associations of 12 loci with breast cancer tumour characteristics. Associations were evaluated using a retrospective cohort approach.

Results

The results suggested stronger associations with ER-positive breast cancer than ER-negative for 11 loci in both BRCA1 and BRCA2 carriers. Among BRCA1 carriers, single nucleotide polymorphism (SNP) rs2981582 (FGFR2) exhibited the biggest difference based on ER status (per-allele hazard ratio (HR) for ER-positive = 1.35, 95% CI: 1.17 to 1.56 vs HR = 0.91, 95% CI: 0.85 to 0.98 for ER-negative, P-heterogeneity = 6.5 × 10^-6). In contrast, SNP rs2046210 at 6q25.1 near ESR1 was primarily associated with ER-negative breast cancer risk for both BRCA1 and BRCA2 carriers. In BRCA2 carriers, SNPs in FGFR2, TOX3, LSP1, SLC4A7/NEK10, 5p12, 2q35, and 1p11.2 were significantly associated with ER-positive but not ER-negative disease. Similar results were observed when differentiating breast cancer cases by PR status.

Conclusions

The associations of the 12 SNPs with risk for BRCA1 and BRCA2 carriers differ by ER-positive or ER-negative breast cancer status. The apparent differences in SNP associations between BRCA1 and BRCA2 carriers, and non-carriers, may be explicable by differences in the prevalence of tumour subtypes. As more risk modifying variants are identified, incorporating these associations into breast cancer subtype-specific risk models may improve clinical management for mutation carriers.     

中国汉族BRCA1/2突变的乳腺癌家系中其他肿瘤发病风险分析

目的 研究携带BRCA1/2突变的中国汉族家族性乳腺癌家系中非乳腺癌和卵巢癌的其他肿瘤发病风险.方法 采用聚合酶链反应(PCR)-直接测序法检测465个汉族家族性乳腺癌家系中先证者的BRCA1/2基因胚系突变,比较突变组与非突变组有非乳腺癌和卵巢癌的其他肿瘤家族史的比例.结果 在465例汉族家族性乳腺癌先证者中,BRCA1/2突变者47例(10.1％),非突变者418例(89.9％).在BRCA1/2突变组和非突变组中,两者总的非乳腺癌和卵巢癌的其他肿瘤家族史比例差异无统计学意义(突变组与非突变组,27.7％∶29.9％,x2=0.10,P=0.75);但两组的瘤谱分布有差别,在突变组的家族中最常见肿瘤为胃癌、胰腺癌和前列腺癌;而在非突变组家族中最常见的为肺癌、胃癌和食管癌.进一步分析发现胃癌、胰腺癌和前列腺癌3种肿瘤家族史总的比例在突变组中显著高于非突变组(突变组与非突变组,17％∶7.7％,Fisher精确概率法P=0.048).突变组家族中发生胃癌、胰腺癌和前列腺癌的风险为非突变组家族的2.47倍(95％ CI为1.07 ～ 5.74).结论 在中国汉族家族性乳腺癌患者中,相比较于非BRCA1/2突变家系,BRCA1/2突变患者的家系有相对较高的风险发生胃癌、胰腺癌和前列腺癌.     

The CHEK2*1100delC variant acts as a breast cancer risk modifier in non-BRCA1/BRCA2 multiple-case families

The frame-shifting mutation 1100delC in the cell-cycle-checkpoint kinase 2 gene (CHEK2) has been reported to be associated with familial breast cancer in families in which mutations in BRCA1 and BRCA2 were excluded. To investigate the role of this variant as a candidate breast cancer susceptibility allele, we determined its prevalence in 237 breast cancer patients and 331 healthy relatives derived from 71 non-BRCA1/BRCA2 multiple-case early onset breast cancer families. Twenty-seven patients (11.4%) were carrying the CHEK2*1100delC variant. At least one carrier was found in 15 of the 71 families (21.1%). There was no evidence of cosegregation between the variant and breast cancer, but carrier patients developed breast cancer earlier than did noncarriers. We studied CHEK2 protein expression in 111, and loss of heterozygosity at CHEK2 in 88 breast tumors from these patients. Twelve of 15 tumors from carriers showed absent protein expression as opposed to 3 of 76 tumors from noncarriers (P < 0.001). CHEK2 loss of heterozygosity was associated with absence of protein expression but not with 1100delC carrier status. Thus, selecting for breast cancer cases with a strong familial background not accounted for by BRCA1 or BRCA2 strongly enriches for carriers of CHEK2*1100delC. Our results support a model in which CHEK2*1100delC interacts with an as yet unknown gene (or genes) to increase breast cancer risk.     

Survival of breast cancer patients in BRCA1, BRCA2, and non-BRCA1/2 breast cancer families: a relative survival analysis from Finland.

Reports on the prognosis of familial breast cancer patients have been contradictory. True differences in survival, if they exist, would have important implications for genetic counselling and in treatment of hereditary breast cancer. We assessed the survival rates of 359 familial breast cancer patients (32 patients from BRCA1-positive families, 43 patients from BRCA2-positive families and 284 patients from BRCA1/2-negative breast cancer families) and compared them with those of all other breast cancer patients diagnosed in Finland from 1953 to 1995 (n = 59,517). Cumulative relative survival rates (RSR) were calculated by dividing the observed survival rates by the expected ones. The expected survival rates were derived from the sex, age and calendar year specific life-tables of the general population in Finland. Regression model was used to calculate relative excess risk of death (RR) and to adjust for confounding factors. The overall 5-year RSR of the patients in the BRCA1 families, BRCA2 families, non-BRCA1/2 families and among sporadic cases was 67%, 77%, 86% and 78%, respectively. However, we found no significant differences in the RR adjusted for age, stage and year of diagnosis between the different familial patient groups or the general breast cancer population. In the BRCA1 families the RR tended to be higher [RR 1.30, 95% confidence interval (CI) 0.63--2.70] and in the BRCA2 families lower (RR 0.78, 95% CI 0.39--1.57) than among the general breast cancer patient population. The RR among patients in the non-BRCA1/2 families did not differ from that of the general patient population.     

Breast tumor immunophenotype of BRCA1-mutation carriers is influenced by age at diagnosis.

PURPOSE: Breast tumors of BRCA1 mutation carriers and those of early onset breast cancer cases share similar histological features, being generally high-grade, highly proliferative, aneuploid tumors that are predominantly estrogen- and progesterone-receptor negative. Because histological features of tumors of premenopausal women differ from those of tumors of older women, we sought to determine whether the immunophenotype of breast tumors of BRCA1 mutation carriers was influenced by age at diagnosis. EXPERIMENTAL DESIGN: We examined 31 breast tumors from BRCA1 mutation carriers and compared them with 81 tumors of age-matched (plus or minus 5 years) breast cancer patients unselected for family history. Tumors were further matched for histology, grade, and size. Paraffin-embedded tumor tissues were examined for protein expression of estrogen receptor (ER), PR, Ki-67, cyclin D1, TP53, HER2, beta-catenin, and cyclin E using immunohistochemical approaches. RESULTS: ER (P = 0.01), PR (P = 0.06), and cyclin D1 (P = 0.002) were less frequently expressed and Ki-67 (P = 0.01) and beta-catenin (P = 0.04) were more frequently expressed in tumors of BRCA1 mutation carriers than controls. After age stratification, we found a significant difference in the frequency of tumors of BRCA1 mutation carriers diagnosed before 50 years of age compared with age-matched controls that stained positive for ER (P = 0.01), PR (P = 0.03), Ki-67 (P = 0.008), cyclin D1 (P < 0.001), HER2 (P = 0.04), and beta-catenin (P = 0.05). However, no significant differences were observed in tumors of BRCA1 mutation carriers diagnosed at age 50 or older compared with age-matched controls. CONCLUSIONS: These data suggest that age at diagnosis, possibly related to menopausal status, may be an important factor in the expression of specific proteins in breast tumors of BRCA1 mutation carriers.     

Aberrations of the MRE11–RAD50–NBS1 DNA damage sensor complex in human breast cancer: MRE11 as a candidate familial cancer-predisposing gene

The MRE11, RAD50, and NBS1 genes encode proteins of the MRE11–RAD50–NBS1 (MRN) complex critical for proper maintenance of genomic integrity and tumour suppression; however, the extent and impact of their cancer-predisposing defects, and potential clinical value remain to be determined. Here, we report that among a large series of approximately 1000 breast carcinomas, around 3%, 7% and 10% tumours showed aberrantly reduced protein expression for RAD50, MRE11 and NBS1, respectively. Such defects were more frequent among the ER/PR/ERBB2 triple-negative and higher-grade tumours, among familial (especially BRCA1/BRCA2-associated) rather than sporadic cases, and the NBS1 defects correlated with shorter patients’ survival. The BRCA1-associated and ER/PR/ERBB2 triple-negative tumours also showed high incidence of constitutively active DNA damage signalling (γH2AX) and p53 aberrations. Sequencing the RAD50, MRE11 and NBS1 genes of 8 patients from non-BRCA1/2 breast cancer families whose tumours showed concomitant reduction/loss of all three MRN-complex proteins revealed two germline mutations in MRE11: a missense mutation R202G and a truncating mutation R633STOP (R633X). Gene transfer and protein analysis of cell culture models with mutant MRE11 implicated various destabilization patterns among the MRN complex proteins including NBS1, the abundance of which was restored by re-expression of wild-type MRE11. We propose that germline mutations qualify MRE11 as a novel candidate breast cancer susceptibility gene in a subset of non-BRCA1/2 families. Our data have implications for the concept of the DNA damage response as an intrinsic anti-cancer barrier, various components of which become inactivated during cancer progression and also represent the bulk of breast cancer susceptibility genes discovered to date.     

Clinical impact of detection of loss of heterozygosity of BRCA1 and BRCA2 markers in sporadic breast cancer.

The development of familial and sporadic breast cancer is based on genetic alterations of tumour-suppressor genes, for which loss of heterozygosity (LOH) is one mechanism of gene inactivation. To investigate LOH of BRCA1 (17q21) and BRCA2 (13-q12-13) in sporadic breast cancer, polymerase chain reaction (PCR)-based fluorescent DNA technology for detection of microsatellite polymorphisms was applied. A total of 137 breast cancer and 15 benign breast specimens with matched normal tissue were examined. Fluorescent-labelled PCR products were analysed in an automated DNA sequencer (ALFTM Pharmacia). Losses at both loci were correlated with different histological types, age, tumour size, lymph node status, grading and steroid hormone receptor expression, [SHR: oestrogen receptor (ER), progesterone receptor (PgR)]. For BRCA1 (D17S855, THRA1, D17S579) losses could be detected in invasive ductal carcinoma (IDC; n = 108) in 32-38%, invasive lobular carcinoma (ILC; n = 19) in 21-42% depending on the marker applied, but not in benign breast tumours (n = 15). Losses of BRCA1 markers correlated with larger tumour size, higher grade, and PgR expression. For BRCA2 (D13S260, D13S267, D13S171) losses could be detected in 108 IDCs in 30-38%, in 19 ILCs in 17-39% depending on the marker applied, but not in benign breast tumours. Losses of BRCA2 markers correlated only with higher grade. Microsatellite analyses combined with detection of fluorescent-labelled PCR products by an automated laser DNA sequencer can be used for routine determination of LOH. In sporadic breast cancer, LOH of BRCA1 of BRCA2 does not add decisive prognostic value as stated for familial breast cancer.     

BRCA1对辐射诱发乳腺癌的作用研究进展

抑癌基因BRCA1的突变几乎存在于所有遗传性乳腺癌与卵巢肿瘤的家属,大约一半家属仅发生乳腺癌,而且其遗传能增加发生乳腺癌和卵巢癌的概率也已被确认,但这种特殊肿瘤的易感性机制还尚未明确。抑癌基因BRCA1产物至少可以通过参与DNA损伤和修复反应途径发挥其肿瘤抑制功能。细胞对DNA损伤反应缺陷会诱发肿瘤,电离辐射可引起DNA簇损伤和双链断裂,成为细胞修复过程的问题。ATM、BRCA1和BRCA2三个基因的编码产物是正常细胞对DNA双链断裂反应所必不可少的,它们突变时就会诱发乳腺癌。其中BRCA1发挥重要作用。     

Familial non-BRCA1/BRCA2-associated breast cancer

Multidisciplinary breast-cancer teams commonly encounter women, both premenopausal and postmenopausal, presenting with breast cancer who also have a family history of this disease. Much of the published work on management of hereditary breast cancer focuses on women with known mutations in BRCA1 and BRCA2, in whom high-grade tumours, common second primaries, and a differential response to adjuvant chemotherapies could be relevant in finding the most effective management strategies. Extrapolation of some of these findings to all patients with familial breast cancer is tempting. However, for women in whom BRCA1 or BRCA2 mutations are unlikely or not found, what evidence is there to inform choices about the various management options? We review the published work on management issues for patients with familial breast cancer not due to a detectable mutation in BRCA1/BRCA2 and compare it with the issues for BRCA1 and BRCA2 carriers on whom more information is available.     

Estrogen receptor status in BRCA1- and BRCA2-related breast cancer: the influence of age, grade, and histological type.

PURPOSE: BRCA1-related breast cancers are more frequently estrogen receptor (ER) negative than are either BRCA2-related or nonhereditary breast cancers. The relationship between ER status and other clinical features of hereditary breast cancers has not been well studied. EXPERIMENTAL DESIGN: ER status, grade, and histological tumor type were evaluated in 1131 women with invasive breast cancer, ascertained at 10 centers in North America. There were 208 BRCA1 mutation carriers, 88 BRCA2 carriers, and 804 women without a known mutation. We stratified the patients by mutation status, grade, age, and histological type and calculated the percentage of ER-positive tumors within each stratum. RESULTS: BRCA1 mutation carriers were more likely to have ER-negative breast cancers than were women in other groups, after adjustment for age, grade, and histological subtype (P < 0.001). Only 3.9% of BRCA1-related breast cancers were ER-positive cancers occurring in women in their postmenopausal years. The direction and magnitude of the change in ER status with increasing age at diagnosis in BRCA1 carriers was significantly different from in BRCA2 carriers (P(intercept) = 0.0002, P(slope) = 0.04). Notably, changes in ER status with age at diagnosis for BRCA1 carriers and noncarriers were almost identical (P(slope) = 0.98). CONCLUSIONS: The strong relationship between the presence of a BRCA1 mutation and the ER-negative status of the breast cancers is neither a consequence of the young age at onset nor the high grade but is an intrinsic property of BRCA1-related cancers. The ER-negative status of these cancers may reflect the cell of origin of BRCA1-related cancers.