Prevalence and Penetrance of BRCA1 and BRCA2 Germline Mutations in Colombian Breast Cancer Patients

Pathogenic BRCA1/2 germline mutations confer high risks of breast and ovarian cancer to women of European ancestry. Characterization of BRCA1/2 mutations in other ethnic groups is also medically important. We comprehensively screened 68 Colombian breast/ovarian cancer families for small-range mutations, 221 families for large-genomic rearrangements, and 1,022 unselected breast cancer cases for Colombian founder mutations in BRCA1/2. The risk of cancer among relatives of mutation carriers and the mutation penetrance were estimated by survival analysis. Identified BRCA2 mutations included 6310delGA and the recurrent 1991del4 mutations. A novel large BRCA2 deletion was found in 0.9% of the screened families. Among unselected breast cancer cases, 3.3% tested positive for BRCA1/3450del4, 2.2% for BRCA1/A1708E, 1.1% for BRCA2/3034del4, and 0.4% for BRCA2/1991del4. Female relatives of carriers of BRCA1/2 founder mutations showed a 5.90 times higher risk of breast cancer, when the woman herself carried a BRCA1 mutation compared to a non-carrier (95% CI 2.01–17.3). The estimated cumulative risk of breast cancer by age 70 years for BRCA1 mutations carriers was 14% (95% CI 5–38) compared to 3% for the general Colombian population (relative risk of breast cancer 4.05). Together with known founder mutations, reported novel variants may ease a cost-effective BRCA1/2 screening in women with Colombian ancestry.

Abstract P3-14-09: Quality of life assessed by BREAST-Q in patients with delayed immediate tissue expander based breast reconstruction with and without radiotherapy

Introduction

Radiotherapy of the breast is known for having a negative impact on implant based breast reconstruction. Technical improvements, such as expander-implant based delayed immediate reconstruction (EIBR), seem to produce better results. The purpose of this study was to analyze the effects of prior radiotherapy (RT) and postmastectomy radiotherapy (PMRT) on patient-reported quality of life (QoL) in patients with EIBR compared to patients that underwent EIBR without any RT.

Material and methods

After a retrospective chart review, all patients with a history of EIBR at the Red Cross Hospital Munich were invited for a structured physical examination and interview. All operations were performed between 2008 and 2012 by two surgeons (H.U. and B.M.). To assess QoL, the BREAST-Q - post reconstruction module was used and results were compared between the following three cohorts: 1. patients without RT (n=65), 2. patients with PMRT (n= 27) and 3. patients with a history of breast irradiation before mastectomy (n=16). Patients with prior RT and a PMRT after local relapse were excluded.

Results

Of 161 patients eligible, 94 patients followed the invitation, 14 of them with bilateral EIBR. Baseline characteristics between participating and non-participating patients were comparable. The median follow-up time was 18.1 months. Most of the baseline

characteristics (e.g. tobacco use, diabetes) were comparable between the cohorts. Application of (neo-) adjuvant chemotherapy was significantly more frequent in cohort 2. The category Satisfaction with the breast was numerically but not significantly

better in cohort 1 than in cohort 2 (p 0,078) whereas the psychosocial well-being showed a trend in favor of cohort 2 (p 0,058). Satisfaction with breast was significantly better in cohort 1 than 3 (p 0,014) as well as Satisfaction with breast (implant only) (p=0,007). There was no difference for Satisfaction with outcome (p=0,666). Cohort 2 reached more points in all categories than cohort 3 although this difference was not significant. Of all patients, 92,7 %, 84,6 % and 78,6% (cohorts 1, 2 and 3) would undergo the operation again.

Conclusion

After short follow-up time, EIBR seems to be a feasible method for breast reconstruction resulting in a high QoL, even if PMRT is required. In patients with a prior RT, QoL is worse compared to the other groups. However, patients´ acceptance of EIBR is still high. Prospective studies and long-term follow-up are required for definitive conclusions.

Citation Format: Hamann M, Brunnbauer M, Scheithauer H, Hamann U, Pölcher M, Braun M. Quality of life assessed by BREAST-Q in patients with delayed immediate tissue expander based breast reconstruction with and without radiotherapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-14-09.

FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium

BACKGROUND

Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium.

METHODS

Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression.

RESULTS

Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95% confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2.

CONCLUSION

Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

BACKGROUND

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

METHODS

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

RESULTS

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

CONCLUSION

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

Evaluation of a candidate breast cancer associated SNP in ERCC4 as a risk modifier in BRCA1 and BRCA2 mutation carriers. Results from the Consortium of Investigators of Modifiers of BRCA1/BRCA2 (CIMBA)

Background:

In this study we aimed to evaluate the role of a SNP in intron 1 of the ERCC4 gene (rs744154), previously reported to be associated with a reduced risk of breast cancer in the general population, as a breast cancer risk modifier in BRCA1 and BRCA2 mutation carriers.

Methods:

We have genotyped rs744154 in 9408 BRCA1 and 5632 BRCA2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) and assessed its association with breast cancer risk using a retrospective weighted cohort approach.

Results:

We found no evidence of association with breast cancer risk for BRCA1 (per-allele HR: 0.98, 95% CI: 0.93–1.04, P=0.5) or BRCA2 (per-allele HR: 0.97, 95% CI: 0.89–1.06, P=0.5) mutation carriers.

Conclusion:

This SNP is not a significant modifier of breast cancer risk for mutation carriers, though weak associations cannot be ruled out.

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.

Estrogen receptor polymorphisms and the risk of endometrial cancer

OBJECTIVE

There is evidence that estrogens and some of their metabolites are involved in endometrial cancer pathogenesis. As estrogens mediate their effects via the estrogen receptors, ESR1 and ESR2, the objective of this investigation was to determine whether six single nucleotide polymorphisms (SNPs) in these two genes were over-represented in a population of endometrial cancer patients compared with a healthy matched control population, thereby associating differences in these genes with endometrial cancer.

DESIGN

The study is a case-control investigation large enough to detect a two-fold increased risk, assuming a dominant genetic model, with P = 0.05 and 80% power.

SETTING

The study and control populations were all from the Hunter-New England region of New South Wales, Australia collected between the years 1992 and 2005.

POPULATION

The study consisted of 191 endometrial cancer patients and 291 healthy controls matched for gender and age.

METHODS

Two SNPs in ESR1 and four SNPs in ESR2 were genotyped using PCR-based restriction fragment length polymorphism analysis and real-time PCR. Odds ratios were calculated using unconditional logistic regression and SIMHAP was used for haplotype analysis, adjusting for potential endometrial cancer risk factors. Kaplan-Meier survival analysis, Cox regression and t tests were used to examine the patient's age of diagnosis of endometrial cancer and genotype.

MAIN OUTCOME MEASURES

Over-representation of ESR1 and ESR2 polymorphisms in the endometrial cancer population compared with the control population indicates an involvement in the development and/or progression of disease.

RESULTS

Two ESR1 (rs2234693 and rs9340799) and two ESR2 (rs1255998 and rs944050) polymorphisms were associated with an increased risk of endometrial cancer. Following adjustment for risk factors, the association with the ESR1 and ESR2 polymorphisms (rs2234693, rs1255998 and rs944050) remained highly significant. Haplotype analysis revealed that carriers of the ESR1 haplotype (variant alleles; rs2234693 and rs9340799) and the ESR2 haplotype (variant allele; rs1255998 and wild-type alleles; rs944050, rs4986938 and rs1256049) were at an increased risk (OR 1.862, P = 0.013 and OR 1.918, P = 0.046 respectively). This risk was even greater in women carrying both risk haplotypes (OR 5.041, P = 0.007).

CONCLUSIONS

Our data suggest that the ESR1 (rs2234693 and rs9340799) and the ESR2 (rs1255998 and rs944050) polymorphisms may be associated with an increased risk of developing endometrial cancer.

An evaluation of the polymorphisms Ins16bp and Arg72Pro in p53 as breast cancer risk modifiers in BRCA1 and BRCA2 mutation carriers

The close functional relationship between p53 and the breast cancer susceptibility genes BRCA1 and BRCA2 has promoted the investigation of various polymorphisms in the p53 gene as possible risk modifiers in BRCA1/2 mutation carriers. Specifically, two polymorphisms in p53, c.97-147ins16bp and p.Arg72Pro have been analysed as putative breast cancer susceptibility variants, and it has been recently reported that a p53 haplotype combining the absence of the 16-bp insertion and the presence of proline at codon 72 (No Ins-72Pro) was associated with an earlier age at the onset of the first primary tumour in BRCA2 mutation carriers in the Spanish population. In this study, we have evaluated this association in a series of 2932 BRCA1/2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2.

Allelic imbalance and fine mapping of the 17p13.3 subregion in sporadic breast carcinomas

Chromosome arm 17p is frequently altered in a variety of human cancers, especially in breast cancer, and allelic imbalances (AIs) in the region 17p13.1 do not always coincide with mutations in the TP53 gene. A second interval that frequently shows AIs at 17p is the chromosomal band 17p13.3. This region is suspected to harbor another tumor suppressor gene. In order to get more information concerning the pattern of AIs in 17p13.3, we performed analysis of AI of 49 breast carcinomas at 6 polymorphic loci in 17p13.3. Eighty-six percent of the tumors present AI at least at one marker in 17p13.3. Among all loci tested, the highest percentage of Al was observed at loci D17S5 (77%) and D17S1528 (72%). According to these results, a minimal region of deletion could be determined between the markers D17S28 and D17S5. Fine mapping of this region revealed that the size of the deleted region is about 100-150 kb. Furthermore, a subset of the patients shows two other areas with AI close to the markers D17S1574/D17S513 and D17S849, respectively.

Hereditary breast cancer: high risk genes, genetic testing and clinical implications

About one in eight to ten women living in Western countries will develop breast cancer during her lifetime and between 5-10% of these cases result from an inherited susceptibility to the disease. Within the past few years, a number of genes associated with a high risk of breast cancer have been identified, including BRCA1, BRCA2, TP53, PTEN, MLH1, MSH2, and STK11. The identification of these genes, together with the rapid advances in molecular genetic analyses, should improve the diagnosis and therapy of breast cancer. This article reviews the genetic basis of hereditary breast cancer, in particular the contribution of BRCA1 and BRCA2 and discusses the clinical application of this new molecular knowledge with regard to molecular testing, surveillance and prevention in women with a hereditary predisposition to breast cancer.

Survival and tumor characteristics of German hereditary breast cancer patients

Reports from different countries have been inconclusive in attempting to relate the BRCA1 mutation status to the survival of breast cancer patients. The purpose of this study was to investigate overall and disease-free survival for German hereditary breast cancer patients. Data on clinical outcome and data on age at diagnosis of breast cancer, histology, tumor size, lymph node status, histological grade, and laterality of 36 breast cancer patients from 12 families with a BRCA1 mutation and from one family with strong evidence for linkage to BRCA1 were compared with those of 49 hereditary breast cancer patients from 23 families that did not harbor a BRCA1 mutation. Overall and disease-free survival was estimated for both groups. BRCA1 mutation carriers had a significantly earlier age of diagnosis than non-carriers (p = 0.0001) and more frequently developed contralateral breast cancer (p = 0.04). Also, BRCA1-associated tumors more frequently were of larger size (p = 0.041) and higher grade of malignancy (p = 0.005) than non-BRCA1-associated tumors. Whereas no difference in overall survival was seen, disease-free survival at 10 years differed significantly with 53.3% for BRCA1 mutation carriers and 76% for non-carriers (p = 0.02). However, after stratification for age and in multivariate analysis for mutation status, age, and bilaterality, it was shown that the worse prognosis for BRCA1 mutation carriers disappeared. Our results suggest that the worse prognosis of BRCA1 mutation carriers in terms of disease-free survival may in large part be due to the age of onset of breast cancer in this population. Thus, BRCA1 mutation status does not appear to be an independent prognostic factor.

Multifactorial analysis of differences between sporadic breast cancers and cancers involving BRCA1 and BRCA2 mutations

BACKGROUND

We have previously demonstrated that breast cancers associated with inherited BRCA1 and BRCA2 gene mutations differ from each other in their histopathologic appearances and that each of these types differs from breast cancers in patients unselected for family history (i.e., sporadic cancers). We have now conducted a more detailed examination of cytologic and architectural features of these tumors.

METHODS

Specimens of tumor tissue (5-microm-thick sections) were examined independently by two pathologists, who were unaware of the case or control subject status, for the presence of cell mitosis, lymphocytic infiltration, continuous pushing margins, and solid sheets of cancer cells; cell nuclei, cell nucleoli, cell necrosis, and cell borders were also evaluated. The resulting data were combined with previously available information on tumor type and tumor grade and further evaluated by multifactorial analysis. All statistical tests are two-sided.

RESULTS

Cancers associated with BRCA1 mutations exhibited higher mitotic counts (P = .001), a greater proportion of the tumor with a continuous pushing margin (P<.0001), and more lymphocytic infiltration (P = .002) than sporadic (i.e., control) cancers. Cancers associated with BRCA2 mutations exhibited a higher score for tubule formation (fewer tubules) (P = .0002), a higher proportion of the tumor perimeter with a continuous pushing margin (P<.0001), and a lower mitotic count (P = .003) than control cancers.

CONCLUSIONS

Our study has identified key features of the histologic phenotypes of breast cancers in carriers of mutant BRCA1 and BRCA2 genes. This information may improve the classification of breast cancers in individuals with a family history of the disease and may ultimately aid in the clinical management of patients.

Consortium study on 1280 breast carcinomas: allelic loss on chromosome 17 targets subregions associated with family history and clinical parameters

The pattern of loss of heterozygosity (LOH) on chromosome 17 in human breast cancer is complicated and shows many different regions of loss. In an attempt to narrow down the relevant regions of LOH on chromosome 17, we have studied the deletion pattern and its association with clinical parameters in 1280 breast carcinoma-venous blood lymphocyte pairs. In total, 42 different chromosome 17 loci were investigated, and between 25 and 625 cases were analyzed at each locus. The frequency of LOH observed on the p arm was much higher than that observed on the q arm. The opposite effect was observed in 52 ovarian cancer cases investigated, with less LOH on 17p than on 17q. Patterns of loss consistent with interstitial and terminal deletions, as well as loss of either the p or q arm or monosomy 17 were observed. To determine whether loss at particular loci may be associated with biological features of breast tumors, clinical data including age of onset, family history of breast cancer, tumor histopathology, tumor size, estrogen receptor (ER) status, and occurrence of lymph node or distant metastases were collected for each case. Overall, large-sized, ER-negative, lymph node-positive ductal tumors showed the highest frequencies of LOH, with ER-negative and ductal tumors showing LOH for markers along the majority of the chromosome. Eight regions of chromosome 17 appear to be associated with human breast cancer, two on 17p and six on 17q. These regions were not necessarily in the areas exhibiting the highest frequencies of LOH but were defined by interstitial and terminal deletions in multiple independent cases. Seven of these regions showed statistically significant differences in LOH associated with clinical parameters. These data strongly suggest that loci on chromosome 17 may determine aspects of tumor presentation and disease behavior in human breast cancer and pinpoint candidate tumor suppressor gene loci.

Low frequency of BRCA1 germline mutations in 45 German breast/ovarian cancer families

In this study we investigated 45 German breast/ovarian cancer families for germline mutations in the BRCA1 gene. We identified four germline mutations in three breast cancer families and in one breast-ovarian cancer family. among these were one frameshift mutation, one nonsense mutation, one novel splice site mutation, and one missense mutation. The missense mutation was also found in 2.8% of the general population, suggesting that it is not disease associated. The average age of disease onset in those families harbouring causative mutations was between 32.3 and 37.4 years, whereas the family harbouring the missense mutation had an average age of onset of 51.2 years. These findings show that BRCA1 is implicated in a small fraction of breast/ovarian cancer families suggesting the involvement of another susceptibility gene(s).

Loss of heterozygosity at 7q31 in breast cancer: results from an International Collaborative Study Group. The Breast Cancer Somatic Genetics Consortium

Loss of heterozygosity (LOH) at 7q31 has been claimed to occur in over 80% of all breast cancers and to be of prognostic significance. This would make this genetic alteration the most common event observed in breast cancer to date. Others, however, have been unable to confirm this high incidence. In this multicenter study, we have complied LOH scorings for three polymorphic markers for 7q31-q32 in 683 breast tumors. Although some significant differences between centers existed, no center reported more than 40% LOH, and the average rate was 19%. Disease-free and overall survival of the patients whose tumors carried LOH at 7q31 did not differ significantly from those patients whose tumors showed retention of heterozygosity at 7q31. In a double-blind scoring of a subset of the raw data, an average discordant rate of LOH scoring of 12% was observed. While startling in itself, this was unable to explain the variation among centers, nor the difference with the initially reported high rate of LOH. We conclude that LOH at 7q31 is not important as a genetic alteration in breast cancer as originally suggested, nor a strong determinant of disease outcome.

German family study on hereditary breast and/or ovarian cancer: germline mutation analysis of the BRCA1 gene

Women harboring BRCA1 germline mutations carry an 85% lifetime risk of developing breast cancer and a 63% risk of ovarian cancer. In this first systematic study of familial breast and/or ovarian cancer in Germany we investigated 29 families for germline mutations in the BRCA1 gene. We identified mutations in three breast cancer families and in four breast-ovarian cancer families. The mutations include one missense mutation, one frameshift mutation, one splice mutation, and four nonsense mutations cosegregating with breast and/or ovarian susceptibility in five of ten (50%) families showing positive evidence of linkage to chromosome band 17q21 and in two of 19 (11%) families where linkage data was not available. Two apparently unrelated families carried the same nonsense mutation at codon 1835 and three families harbored a C to T transition at nucleotide 49 of the untranslated exon 4. Allelotyping of the markers D17S855, D17S1322, D17S1323, and D17S1327 located within or near BRCA1 revealed that all affected individuals in the two families harboring the mutation at codon 1835 shared at least one allele indicating a founder mutation. With respect to the overall mutation spectrum, no mutations were identified in exon 11 (0/7) in this set of German families. These findings differed significantly from those in British (17/32)(P = 0.012) and Southern Swedish (13/15) (P < 0.001) families. The lack of BRCA1 mutations in exon 11 which represents 61% of the entire coding sequence may provide additional insight into BRCA1 associated breast and ovarian tumor development.

Modifying effect of reproductive risk factors on the age at onset of breast cancer for German BRCA1 mutation carriers

Female carriers of mutations in the BRCA1 gene on chromosome 17q have a very high risk of developing breast and/or ovarian cancer during their lifetime. There is, however, little knowledge of to what extent non-genetic risk factors, such as age at menarche, age at first birth, and body mass index, alter the age at onset of disease. We identified individuals showing a high probability of linkage to BRCA1 and examined the effect of other known risk factors on disease risk. A total of 43 families with at least three breast or ovarian cancer cases, including two affected before 60 years of age, were studied for linkage to the susceptibility locus BRCA1. Blood samples from relevant family members were used to genotype for at least three chromosome 17q polymorphic markers. Information on reproductive history, hormone use and lifestyle factors was collected from female members using a self-administered questionnaire. Diagnoses of breast and ovarian cancer were verified through pathology reports and paraffin blocks were obtained when available. Multipoint LOD (logarithm of the odds) scores were calculated and individuals from 10 families with a posteriori probability for linkage greater than 0.90 were used for further analysis. Forty-six BRCA1 carriers were identified by the disease haplotype; 30 were affected with breast cancer and 5 with ovarian cancer. Proportional- hazards analysis of age at onset of breast cancer yielded increased relative risks of 1.74 for early age at menarche (< 14 years), 1.58 for late age at first birth (> or = 25 years) or nulliparity, and 2.78 for recent year of birth (> or = 1940); however, none of the risk estimates was statistically significant. When both breast and ovarian cancer were considered as disease endpoints, the birth cohort effect was stronger and age at first birth showed no effect. Our data provide some evidence that reproductive risk factors for breast cancer have an effect on age at onset for BRCA1 carriers. However, considering that our analyses were based on limited numbers, these results warrant further clarification.

German family study on hereditary breast-ovarian cancer

An estimated 5% to 10% of all breast and ovarian cancers are attributed to dominant susceptibility genes. Two such genes, BRCA1 and BRCA2, were recently identified. The involvement of these genes was studied in 43 German breast only and breast-ovarian cancer families. All families contained three or more cases of breast or ovarian cancer, with at least two diagnosed under the age of 60 years. Multipoint linkage analysis gave a maximum lod score of 2.13 at the BRCA1 locus under the assumption of genetic heterogeneity, with an estimated 50% of families being linked. Among the 33 breast only cancer and 10 breast-ovarian cancer families, the estimated proportions of linked families were 35% and 75%, respectively. Sixteen families with at least four cases of female breast cancer diagnosed under the age of 60 years, or male breast cancer diagnosed at any age, were analysed for linkage to BRCA2. Positive lod scores at BRCA2 were obtained in six families.

Allelic imbalance on chromosome 13q: evidence for the involvement of BRCA2 and RB1 in sporadic breast cancer

Recently, the breast cancer susceptibility gene BRCA2 has been identified in chromosome 13q, a region that also contains the retinoblastoma gene RB1. To elucidate a possible role of BRCA2 and RB1 in sporadic breast tumorigenesis, allelic imbalance (AI) at 13q loci was examined in 78 primary sporadic breast tumors. AI was found in 52-63% of tumors. Nine tumors showed AI only in the BRCA2 region but not at RB1. Six tumors showed AI at RB1 but not in the BRCA2 region. AI in the BRCA2 region correlated significantly with aneuploidy (P = 0.032) and AI at RB1 with small tumor size (P = 0.025). Our data suggest that BRCA2 and RB1 may be both distinct target loci for AI on chromosome 13 in sporadic breast cancer.

High allele loss rates at 17q12-q21 in breast and ovarian tumors from BRCAl-linked families. The Breast Cancer Linkage Consortium

Loss of heterozygosity (LOH) was evaluated in 174 breast and ovarian tumors derived from 94 families with at least 3 first-degree relatives affected with either of these cancers. By linkage analysis 26 families were identified as having a high posterior probability of being due to BRCAl (the breast/ovarian cancer susceptibility locus on 17q12-21) with lod scores varying from 0.51 to 9.49. Tumor genotypes were determined at at least 2 constitutionally heterozygous markers flanking BRCAl in a total of 58 tumors from these families. These tumors were derived from 52 patients, the BRCAl mutation carrier status of which was evidenced by DNA sequencing in 20, and inferred by reconstructing haplotypes in the remainder. LOH was detected in 50 (86%) tumors, and invariably involved the wild-type allele. Where informative, this allele was of paternal origin in 33 cases and of maternal origin in 10 cases. These results strongly suggest that BRCAl is a tumor suppressor gene and that LOH is greatly favored to fully inactivate it.

Mutations in the putative lipid-interaction domain of complement C9 result in defective secretion of the functional protein

Complement protein C9 assembles with C5, C6, C7, C8 on the surface of target cells to form the lytic membrane attack complex (MAC). During MAC assembly and insertion into the target membrane, the hydrophilic, globular C9 partially unfolds to expose a hydrophobic lipid interaction domain. Several copies of amphiphilic C9 subsequently polymerize to form the characteristic ring-like MAC. Using a combined photoaffinity label and computer modeling approach, two amphipathic helices in a segment encompassing the amino acids 293-334 have been predicted to interact with membrane lipids. To elucidate the mechanism of C9 lipid binding and insertion, site-directed mutagenesis was used to change the amphipathic character of the helices. While some conservative amino acid replacements such as Thr307 by a Leu were tolerated and yielded fully active C9 when expressed in COS cells, successive changes of Leu305 into Val, Ala, and Glu on the hydrophobic site of the first helix gave rise to only partly or not secreted C9. All non-conservative amino acid replacements introduced on either side of the helices resulted in non-secreted C9 that was subsequently degraded intracellularly, indicating the importance of the correct folding of the presumptive transmembrane domain during biosynthesis. A natural secretion-incompetent mutant was found in which Val293, located in the proposed lipid-binding region, was lacking. Taken together, these findings suggest that the high incidence of homozygous C9 deficiencies may be due to a blockage in intracellular transport and secretion due to point mutations in this 'hot spot' region of the molecule.

The N-Myc oncoprotein is associated in vivo with the phosphoprotein Max(p20/22) in human neuroblastoma cells

Proteins encoded by the proto-oncogenes c-myc, L-myc, and N-myc contain at their carboxy-terminus a tripartite segment comprising a basic DNA binding region (BR), a helix-loop-helix (HLH) and a leucine zipper motif (Zip), that are believed to be involved in DNA binding and protein-protein interaction. The N-Myc oncoprotein is overexpressed in certain human tumors that share neuroectodermal features due to amplification of the N-myc gene. Using a monoclonal antibody directed against an N-terminal epitope of the N-Myc protein in immunoprecipitations performed with extracts of neuroblastoma cells, two nuclear phosphoprotein, p20/22, forming a hetero-oligomeric complex with N-Myc are identified. Both proteins are phosphorylated by casein kinase II in vitro. By partial proteolytic maps we show that p20 and p22 are structurally related to each other and that p20 is identical with Max, a recently described in vitro binding partner of myc proteins. Time course experiments show the presence of the complex in cellular extracts immunoprecipitated within a 5 min interval after the preparation of the cell extract. While the expression of N-myc is restricted, expression of both Max(p20/22) and the murine homolog Myn(p20/22) was observed in cells of diverse human and murine embryonal lineages as detected by heterologous complex formation. By introduction of expression vectors containing the wild type N-myc gene or N-myc genes with in frame deletions or point mutations into recipient cells and subsequent immunoprecipitation of the resulting N-Myc proteins we show that the HLH-Zip region is essential to the formation of the N-Myc-p20/22 complex.

The MYCN protein of human neuroblastoma cells is phosphorylated by casein kinase II in the central region and at serine 367

The MYCN gene has been implicated in certain neuronal tumours, such as neuroblastomas and retinoblastomas. These tumours express high levels of mRNA and protein of MYCN as a result of amplification. MYCN encodes a short-lived nuclear phosphoprotein whose function has not yet been elucidated. This study was undertaken to determine the pattern of MYCN protein (pMYCN) phosphorylation in human neuroblastoma cells. We report that pMYCN is phosphorylated in vitro by purified casein kinase II (CK-II). Two-dimensional phosphopeptide maps showed that most of the phosphopeptides of pMYCN phosphorylated in vitro by CK-II correspond to those phosphorylated in vivo. Fine mapping of the phosphorylation sites was performed using two synthetic MYCN peptides corresponding to pMYCN CK-II consensus sequences. Both peptides were found to be phosphorylated by CK-II and competitively inhibited CK-II phosphorylation of pMYCN in vitro. Thus, we have localized two major CK-II phosphorylation sites in pMYCN, one to the highly acidic central region and the second to serine 367 proximal to the C-terminus. Our data demonstrate that pMYCN is a physiological substrate for CK-II and, since CK-II activity is stimulated in response to mitogens, CK-II phosphorylation of pMYCN may, therefore, represent one signal transduction pathway used by neuroblastoma cells.

A nucleoprotein peptide of influenza A virus stimulates assembly of HLA-B27 class I heavy chains and beta 2-microglobulin translated in vitro

Most cytotoxic T lymphocytes (CTL) recognize epitopes of foreign viral proteins in association with class I major histocompatibility complex (MHC) molecules. Viral proteins synthesized in the cytoplasm require intracellular fragmentation and exposure to the class I antigens for the development of CTL responses. Although indirect evidence for binding of peptides to class I antigens has accumulated, direct binding has only been shown recently. The formation of complexes between peptide and class I antigen may occur in the endoplasmic reticulum (ER) and peptides have been shown to induce assembly of the class I complex. We have translated the messenger RNAs encoding HLA-B27 (subtype 2705) and beta 2-microglobulin in a rabbit reticulocyte lysate supplemented with human microsomal membranes (to mimic ER membranes), in the absence and presence of a peptide derived from the nucleoprotein (residues 384-394) of influenza A virus. This peptide induces CTL activity against target cells expressing the HLA-B27 antigen. Here we report direct evidence that the nucleoprotein peptide promotes assembly of the HLA-B27 heavy chain and beta 2-microglobulin, and that this can occur in the ER immediately after synthesis of the two proteins.

Surface location and high affinity for calcium of a 500-kd liver membrane protein closely related to the LDL-receptor suggest a physiological role as lipoprotein receptor

We describe a cell surface protein that is abundant in liver and has close structural and biochemical similarities to the low density lipoprotein (LDL) receptor. The complete sequence of the protein containing 4544 amino acids is presented. From the sequence a remarkable resemblance to the LDL-receptor and epidermal growth factor (EGF) precursor is apparent. Three types of repeating sequence motifs entirely account for the extracellular domain of the molecule. These are arranged in a manner resembling four copies of the ligand binding and the EGF-precursor homologous region of the LDL-receptor. Following a proline-rich segment of 17 amino acids are found six consecutive repeats with close homology to EGF. A single membrane-spanning segment precedes a carboxy-terminal 'tail' of 100 amino acids. This contains two seven-amino acid sequences with striking homology to the cytoplasmic tail of the LDL-receptor in the region that contains the signal for clustering into coated pits. The mRNA for this protein is most abundant in liver, brain and lung. By using an antibody raised against a 13-amino acid peptide corresponding to the deduced amino acid sequence of the carboxy-terminus of the protein we have demonstrated its existence on the cell surface and its abundance in liver. Like the LDL-receptor this protein also strongly binds calcium, a cation absolutely required for binding of apolipoproteins B and E to their receptors. We propose that this LDL-receptor related protein (LRP) is a recycling lipoprotein receptor with possible growth-modulating effects.

Activation of macrophage tumor cytotoxicity by the synergism of two T cell-derived lymphokines: immune interferon (IFN-gamma) and macrophage cytotoxicity-inducing factor 2 (MCIF2)

This report describes the role of T cell-derived lymphokines in induction of macrophage (M phi) tumor cytotoxicity. M phi tumor cytotoxicity was tested with the murine M phi-like tumor PU5-1.8. This M phi-like tumor reacts to stimulation with T cell-derived lymphokines and shows tumor cytotoxicity comparable to resident peritoneal M phi. The experiments demonstrate that immune interferon (IFN-gamma) secreted by T cell clones in limiting dilution microcultures was insufficient to induce M phi tumor cytotoxicity. Induction of M phi tumor cytotoxicity by T cell-derived supernatants with quantities of IFN-gamma undetectable in the IFN assay, however, was completely inhibited by an antiserum raised against recombinant IFN-gamma. Taken together, these results could be thus explained: (a) a T cell-derived lymphokine distinct from but serologically cross-reactive with IFN-gamma induces M phi tumor cytotoxicity, and (b) IFN-gamma activity in supernatants positive for induction of M phi tumor cytotoxicity escapes detection in the IFN assay but can still be inhibited by the anti-IFN-gamma antiserum in the M phi tumor cytotoxicity assay. The latter explanation requires positive evidence for another T cell-derived lymphokine inducing M phi tumor cytotoxicity together with IFN-gamma. This lymphokine was found in the supernatant of T cells in limiting dilution cultures and a long-term T cell clone and was called M phi cytotoxicity-inducing factor 2 (MCIF2). MCIF2 synergizes with IFN-gamma in induction of M phi tumor cytotoxicity; IFN-gamma and MCIF2 alone were ineffective.

Cytolytic T cells recognize the two amino-terminal domains of H-2 K antigens in tandem in influenza A infected cells

We have genetically engineered three alleles of the K locus of the major histocompatibility complex (MHC) of the mouse. These novel hybrid H-2K genes were introduced into mouse 1T 22-6 cells (H-2q), and their products were shown to be expressed on the cell surface. The hybrid H-2 K antigens were examined for their ability to function as restricting elements for cytotoxic T lymphocytes during influenza A infection. Both the alpha 1 and alpha 2 domains of the Kd antigen were required for T cell recognition. This implies an important role for "conformational determinants" on H-2 antigens acting as restricting elements. The cytoplasmic domain of the Kb antigen is not phenotypically important for recognition by T cells.

[Experiences from laboratory tests with potato breeding material resistant to leaf roll virus]

A description of the laboratory method for testing the resistance of potato breeding material to lea roll virus is given. The main steps of this method are as follows: Three days after emergence potato plants should be infected with potato leaf roll carrying peach aphids.The aphids are separated from feeding plants by treating plants and aphids in a refrigerator at -5 °C to -7 °C for two hours. After this, the aphids are distributed into infection tubes by a special light box.The results obtained from testing the resistance of varieties and breeding material (clonal material and seedling populations) to potato leaf roll virus in the laboratory and in the field were compared. Because of the positive correlation between the results in the field and laboratory, the laboratory method can be recommended for use in practical breeding for leaf roll resistance.