胚系BRCA基因突变乳腺癌的临床诊治进展

BRCA基因是最常见的乳腺癌易感基因,胚系BRCA突变患者罹患乳腺癌的风险显著增加.随着对BRCA基因的深入研究以及聚ADP-核糖聚合酶(poly ADP-ribose polymerase,PARP)抑制剂的出现,BRCA突变已成为乳腺癌治疗的新靶点.在BRCA突变乳腺癌的治疗中,PARP抑制剂和铂类为两大主要药物选...     

353例遗传性高危乳腺癌患者BRCA1、BRCA2、PALB2基因胚系突变的分布情况研究

[目的]通过对女性乳腺癌患者进行胚系基因检测,评估BRCA1、BRCA2、PALB2基因胚系致病/可能致病性突变在高危乳腺癌患者中的分布情况。[方法]收集2016年12月1日至2022年4月30日中山大学附属第一医院收治的女性乳腺癌患者,对已进行胚系多基因检测的353例具有遗传性高危因素的女性乳腺癌患者,对她们的检测结果进行分析,评估BRCA1、BRCA2和PALB2基因胚系致病/可能致病性突变患者的病理和临床特征等情况。[结果] 353例患者中,胚系BRCA1、BRCA2和PALB2致病/可能致病突变者共59例,突变率为16.71%,年轻患者较其他年龄患者的BRCA1突变率更高（P=0.039）,相比其他分子分型,三阴性乳腺癌患者的BRCA1突变（P<0.001）和3个基因的总突变率（P=0.007）都明显更高。和没有肿瘤家族史的患者相比,有肿瘤家族史的患者并没有体现出明显的高突变率。具有2个或2个以上危险因素的患者的基因突变率要明显高于只有1个高危因素的患者（P=0.048）。[结论] PALB2基因胚系致病/可能致病突变在高危乳腺癌患者中的发生比例较高,其重要性并不亚于BR...     

遗传性乳腺癌的筛查与预防研究进展

摘 要：遗传性乳腺癌是指由乳腺癌易感基因致病性种系突变所致的恶性肿瘤。BRCA1/2等易感基因突变与乳腺癌终生风险升高密切相关。乳腺癌筛查技术和方法的不断革新,为早期发现乳腺癌和预防干预提供了可能;早期识别高危风险人群已经成为遗传性乳腺癌筛查与预防工作的重要突破点。全文综述国内外遗传性乳腺癌筛查与预防现状,重点探讨了遗传性乳腺癌的风险评估、基因检测和遗传咨询。     

Effect of pregnancy as a risk factor for breast cancer in BRCA1/BRCA2 mutation carriers

Early age at first birth and multiparity have been associated with a decrease in the risk of breast cancer in women in the general population. We examined whether this relationship is also present in women at high risk of breast cancer due to the presence of a mutation in either of the 2 breast cancer susceptibility genes, BRCA1 or BRCA2. We performed a matched case-control study of 1,260 pairs of women with known BRCA1 or BRCA2 mutations, recruited from North America, Europe and Israel. Women who had been diagnosed with breast cancer were matched with unaffected control subjects for year of birth, country of residence, and mutation (BRCA1 or BRCA2). Study subjects completed a questionnaire detailing their reproductive histories. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived by conditional logistic regression. Among BRCA1 carriers, parity per se was not associated with the risk of breast cancer (OR for parous vs. nulliparous = 0.94; 95% CI = 0.75-1.19; p = 0.62). However, women with a BRCA1 mutation and 4 or more children had a 38% decrease in breast cancer risk compared to nulliparous women (OR = 0.62; 95% CI = 0.41-0.94). In contrast, among BRCA2 carriers, increasing parity was associated with an increased risk of breast cancer; women with 2 or more children were at approximately 1.5 times the risk of breast cancer as nulliparous women (OR = 1.53; 95% CI = 1.01-2.32; p = 0.05). Among women with BRCA2 mutations and who were younger than age 50, the (adjusted) risk of breast cancer increased by 17% with each additional birth (OR = 1.17; 95% CI = 1.01-1.36; p = 0.03). There was no significant increase in the risk of breast cancer among BRCA2 carriers older than 50 (OR for each additional birth = 0.97; 95% CI = 0.58-1.53; p = 0.92). In the 2-year period following a birth, the risk of breast cancer in a BRCA2 carrier was increased by 70% compared to nulliparous controls (OR = 1.70; 95% CI = 0.97-3.0). There was a much smaller increase in breast cancer risk among BRCA2 carriers whose last birth was 5 or more years in the past (OR = 1.24; 95% CI = 0.79-1.95). A modest reduction in risk of breast cancer was observed among BRCA1 carriers with 4 or more births. Among BRCA2 carriers, increasing parity was associated with a significant increase in the risk of breast cancer before age 50 and this increase was greatest in the 2-year period following a pregnancy.     

Novel genetic variants in microRNA genes and familial breast cancer

MicroRNA (miRNA) plays an important role in tumorigenesis, but whether miRNA is a cancer predisposition factor or not is still unknown. Considering the fact that miRNA regulates a number of tumor suppressor genes (TSGs) and oncogenes, genetic variations in miRNA genes could affect the levels of expression of TSGs or oncogenes and, thereby, cancer risk. To test this hypothesis, we screened genetic variants in 17 selected miRNA genes, which are predicted to regulate key breast cancer genes, in 42 patients with familial breast cancer. Seven novel genetic variants were observed in 7 primary or precursor miRNA genes. Among them, 1 rare variant in the precursor of miR‐30c‐1 and 1 rare variant in the primary precursor of miR‐17 were only observed in noncarriers of BRCA1/2 mutations. In functional assays, these 2 variants resulted in conformational changes in the predicted secondary structures, and consequently altered the expression of mature miR‐30c‐1 and miR‐17. In the target in vitro assay, we observed that miR‐17 could bind to the 3′UTR of BRCA1 mRNAs, which is predicted to be a target for miR‐17. Our findings suggest that functional genetic variants in miRNA genes can potentially alter the regulation of key breast cancer genes. Whether they confer genetic susceptibility to breast cancer remains to be determined. © 2008 Wiley‐Liss, Inc.     

Identification of novel BRCA founder mutations in Middle Eastern breast cancer patients using capture and Sanger sequencing analysis

Ethnic differences of breast cancer genomics have prompted us to investigate the spectra of BRCA1 and BRCA2 mutations in different populations. The prevalence and effect of BRCA 1 and BRCA 2 mutations in Middle Eastern population is not fully explored. To characterize the prevalence of BRCA mutations in Middle Eastern breast cancer patients, BRCA mutation screening was performed in 818 unselected breast cancer patients using Capture and/or Sanger sequencing. 19 short tandem repeat (STR) markers were used for founder mutation analysis. In our study, nine different types of deleterious mutation were identified in 28 (3.4%) cases, 25 (89.3%) cases in BRCA 1 and 3 (10.7%) cases in BRCA 2. Seven recurrent mutations identified accounted for 92.9% (26/28) of all the mutant cases. Haplotype analysis was performed to confirm c.1140 dupG and c.4136_4137delCT mutations as novel putative founder mutation, accounting for 46.4% (13/28) of all BRCA mutant cases and 1.6% (13/818) of all the breast cancer cases, respectively. Moreover, BRCA 1 mutation was significantly associated with BRCA 1 protein expression loss (p = 0.0005). Our finding revealed that a substantial number of BRCA mutations were identified in clinically high risk breast cancer from Middle East region. Identification of the mutation spectrum, prevalence and founder effect in Middle Eastern population facilitates genetic counseling, risk assessment and development of cost‐effective screening strategy.     

Effect of chemotherapy on survival in metastatic breast cancer

Summary In order to assess the impact of modern combination chemotherapy on overall survival of metastatic breast cancer patients, we retrospectively analysed survival data of those patients who presented with breast cancer and developed metastases at our clinic from 1971–78 inclusive. Our results indicate a trend towards improved survival from onset of first distant metastasis after 1975. Assessment of survival by treatment modality revealed significantly longer survival from first metastasis for those patients receiving predominantly endocrine treatment compared to chemotherapy, median survival being 32.5 versus 23 months for endocrine therapy and chemotherapy respectively. Patients receiving adriamycin in combination with other drugs, had longer survival from first metastasis than those patients receiving chemotherapy without adriamycin (median survival being 25 versus 18.5 months respectively). These differences are most probably due to patient selection. On the basis of these results it would appear that chemotherapy may be improving short-term survival in some patients, but is making no major impact on long-term survival. Address for reprints: Dr. A.H.G. Paterson, Dept. of Medicine, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta, Canada T6G 1Z2.     

Estimates of the likely prophylactic effect of tamoxifen in women with high risk BRCA1 and BRCA2 mutations

The development of breast cancer control strategies in women at high genetic risk of breast cancer is an important issue. The likely benefit of chemopreventive approaches is of particular interest. Tamoxifen tends to be more effective in both prevention and treatment of oestrogen receptor positive tumours than oestrogen receptor negative. In this study, we combine the oestrogen-receptor specific effects of tamoxifen from randomized preventive or therapeutic trials with the oestrogen receptor status of tumours in BRCA1 and BRCA2 mutation positive women from published tumour surveys to obtain estimates of the likely effect of tamoxifen administration in mutation carriers. We used a simple two-stage procedure to estimate the benefit as a weighted average of the effect on oestrogen receptor positive tumours and oestrogen receptor negative, and using a more complex hierarchical modelling approach. Using the simple procedure and deriving the estimates of benefit from both primary prevention and therapeutic trials, we obtain an estimated reduction in risk of breast cancer from administration of tamoxifen in BRCA1 mutation positive women of 13% (RR=0.87, 95% CI 0.68--1.11). The corresponding estimated reduction in BRCA2 mutation positive women was 27% (RR=0.73, 95% CI 0.59--0.90). Using the more complex models gave essentially the same results. Using only the primary prevention trials gave smaller estimates of benefit in BRCA1 carriers but larger estimates in BRCA2, in both cases with wider confidence intervals. The benefit of prophylactic use of tamoxifen in BRCA1 mutation carriers is likely to be modest, and the effect in BRCA2 mutation carriers somewhat greater.     

Screening for BRCA2 mutations in 81 Dutch breast-ovarian cancer families

We have analysed 81 families with a history of breast and/or ovarian cancer for the presence of germline mutations in BRCA2 with a number of different mutation screening techniques. The protein truncation test (PTT) for exons 10 and 11 detected four different frame-shifting mutations in six of these families. Four of the remaining 75 families had given positive linkage evidence for being due to BRCA2. In these families the entire coding region was analysed by single-strand conformational polymorphism, leading to the detection of a non-sense and a splice-site mutation in two of them. While these studies were in progress, Southern analysis of BRCA1 revealed that in our study-population of 81 families, 15 families were segregating either the exon 13 or exon 22 deletion in BRCA1 (Petrij-Bosch et al (1997) Nat Genet 17: 341-345). This prompted us to examine BRCA2 in the remaining 58 families by Southern analysis, using two different restriction enzymes. No aberrations were found in the restriction patterns. Thus, contrary to BRCA1, large genomic rearrangements within the BRCA2 gene do not represent a major mutation mechanism among Dutch breast cancer families.     

CHEK2 1100delC is not a risk factor for male breast cancer population

Genetic risk factors for male breast cancer (MBC) are poorly understood. High penetrance genes such as BRCA1 or BRCA2 account for only a small proportion of the disease. A 1100delC mutation in CHEK2 (previously known as CHK2), a cell-cycle checkpoint kinase, has been implicated in predisposition of Li-Fraumeni syndrome (LFS) and breast cancer in families suggestive of LFS. This 1100delC mutation has also been shown to confer a 2-fold increase of breast cancer risk in women and a 10-fold increase of risk in men. It was estimated to account for 1% of breast cancers in women and as much as 9% of breast cancers in men at the population level based on analysis of breast cancer families without BRCA1 or BRCA2 mutations. We wanted to evaluate the significance of CHEK2 1100delC in predisposition to MBC by assessing its frequency in a population-based material of 114 Finnish MBC patients. Two patients (1.8%) carried the 1100delC mutation. The mutation frequency among MBC cases was similar to that seen in population controls (26/1885, 1.4%). Our results indicate that CHEK2 1100delC variant does not substantially increase the risk of male breast cancer at the population level. We cannot exclude the fact that a small fraction of hereditary, family-positive male breast cancers could be attributable to CHEK2 mutations.     

Early onset HER2-positive breast cancer is associated with germline TP53 mutations

BACKGROUND:

Germline TP53 mutations predispose to early onset breast cancer in women and are associated with Li‐Fraumeni syndrome. Published data on the pathological characteristics of breast cancer among women with TP53 mutations is limited.

METHODS:

We retrospectively reviewed the clinical records of women who underwent genetic testing for suspected germline TP53 mutations and who were diagnosed with breast cancer between 2000 and 2011. The pathological characteristics of the breast tumors from patients testing positive for a mutation (cases) were compared with those testing negative (controls).

RESULTS:

Patients who tested positive for germlineTP53 mutations (n = 30) were compared with controls (n = 79). Human epidermal growth factor receptor 2 (HER2) amplification and/or overexpression was found in 67% of the tumors from the cases, compared with 25% for the controls (P = .0001). Among patients with a mutation, 70% had estrogen receptor‐ and/or progesterone receptor‐positive tumors, compared with 68% in the control group (P = .87). After adjusting for age at breast cancer diagnosis, having a HER2‐positive tumor increased the odds of testing positive for a germline TP53 mutation (odds ratio, 6.9; 95% confidence interval, 2.6‐18.2). For each yearly increment in age at breast cancer diagnosis, there was decreased likelihood of having a TP53 mutation of 5% (odds ratio, 0.95; 95% confidence interval0.91‐0.99).

CONCLUSIONS:

This study suggests an association between germline TP53 mutations and early onset HER2‐positive breast cancer. If confirmed in a larger cohort, these results could guide genetic testing strategies, lead to chemoprevention trials incorporating HER2‐targeted therapies, and elucidate some of the molecular pathways involved in breast cancer. Cancer 2012;. © 2011 American Cancer Society.     

A new germline mutation in BRCA1 gene in a sicilian family with ovarian cancer

Summary A group of 103 sicilian patients with hereditary and familiar breast and/or ovarian cancer were screened for Breast Cancer 1 gene (BRCA1) mutations by direct sequencing PCR products spanning the coding region and partial intronic regions of the BRCA1 gene. In this study, we report a new germline mutation in BRCA1 gene, not previously reported in the BIC database, in a woman with ovarian cancer at 46 years old. Mother’s proband has been diagnosed the same histotype of ovarian cancer at 42 age. The mutational analyses that shown a 4843delC frameshift mutation in exon 16 of BRCA1 gene was extended to other family members including the proband’s brother and her two sons. Direct automatic sequencing of DNA extracted from the lymphocytes showed exactly the same 4843delC frameshift mutation only in the brother. In conclusion, the characterization of this mutation could help in the identification of a founder mutation of sicilian area and this may provide significant advantages for genetic counselling.  *Both authors have contributed equally to this work     

Vascular endothelial growth factor (VEGF) levels and mutation of the BRCA1 gene in breast cancer patients

The aim of the study was to compare VEGF serum levels in breast cancer patients with and without BRCA1 gene mutation. We enrolled 80 patients, 22 premenopausal and 58 postmenopausal. We found statistically significant lower levels of VEGF in patients with BRCA1 gene mutation as compared with breast cancer patients without this mutation.