Hereditary Breast Cancer and Novel Hispanic BRCA Mutations

Institution: Beckman Research Institute of the City of Hope
Investigator(s): Jeffrey Weitzel, M.D. -
Award Cycle: 2006 (Cycle 12) Grant #: 12IB-0050 Award: $253,500
Award Type: IDEA
Research Priorities
Etiology and Prevention>Etiology: the role of environment and lifestyle



Initial Award Abstract (2006)
Non-technical introduction to the research topics: Breast cancer (BC) is the most commonly diagnosed cancer in Hispanic women, and is the leading cancer cause of death in this population. Mutations in the BRCA genes are associated with 5-10% of BC cases. The lifetime risk of developing BC in individuals with a BRCA mutation may be as high as 85%. There is little information on BRCA mutations in Hispanics. We recently reported on the frequency of BRCA mutations in a group of 110 Hispanic individuals of predominantly Mexican descent living in Southern California. Thirty-four (31%) of these individuals were found to have a BRCA mutation. A BRCA mutation common to individuals of Ashkenazi Jewish descent known as BRCA1 185delAG was detected in 4 of the 34 (3.6%) individuals. DNA from 67 of the 76 patients without a BRCA mutation was analyzed for the presence of large missing DNA segments (deletions) and a deletion of part of the BRCA1 gene was found in 3 of 67 (4.5%) individuals. All 3 individuals are of Mexican ancestry and are unrelated through at least a four-generation family tree, suggesting this mutation may be specific to this population. We have identified the DNA sequences on each side of this deletion and have determined its consequences at the protein-level.

The question(s) or central hypotheses of the research: The purpose of this project is to gather data on the frequency of BRCA mutations that are common among Hispanics in order to develop a more efficient way of providing genetic cancer risk assessment to women of Hispanic ancestry.

We hypothesize that: 1) the BRCA1 185delAG mutation is common in this population; 2) the large BRCA1 deletion mutation will be found at a high frequency among Hispanic families at high-risk for breast cancer; and 3) a test which includes several BRCA mutations that are common among the Hispanic population will be effective in detecting mutations in high-risk Hispanic families.

The general methodology: Tests for the BRCA1 185delAG, the BRCA1 large deletion and a panel of BRCA mutations common to the Hispanic population will be designed. Clinical data and DNA samples will be collected from two population-based and two high-risk clinic-based cohorts. Several groups of women who have been followed in other studies (cohorts) will be tested for the BRCA1 185delAG mutation and the BRCA1 large deletion mutation to determine the prevalence of these mutations. The high-risk clinic based cohorts will also be tested for the BRCA mutations common to the Hispanic population using the developed Hispanic BRCA mutation panel. We will also estimate the age of the large deletion mutation and determine if the mutation is specific to this population through analysis of DNA markers.

Innovative elements of the project: The unique Hispanic BRCA mutation panel that will be developed will help to greatly reduce the cost associated with testing high-risk Hispanic individuals for BRCA mutations. Possible outcomes of this study include more efficient breast cancer risk assessment for Hispanic women, which will allow them to choose the best way (increased breast cancer screening, healthier lifestyle choices, risk-reducing drugs, or surgery) to reduce the risk of advanced breast cancers.

Advocacy involvement and human issues: The data from this study will provide a foundation for the development of cost-effective interventions for ethnic and minority individuals at high-risk for breast cancer. There is a role for advocacy involvement in the translational phases to follow.


Final Report (2008)
Breast cancer (BC) is the most commonly diagnosed cancer in Hispanic women, and is the leading cancer cause of death in this population. Mutations in the BRCA genes are associated with 5-10% of BC cases. The lifetime risk of developing breast cancer in individuals with a BRCA mutation may be as high as 85%. Little research has been performed to “map” and assess the relative frequencies of BRCA mutations in the Hispanic population. We previously reported on the frequency of BRCA mutations in a Hispanic clinic population, wherein we identified several unrelated families that had the same mutation. A BRCA mutation common to individuals of Ashkenazi Jewish ancestry, BRCA1 185delAG, was found in 4 of 34 families with BRCA mutations. We also detected a unique, large deletion (exons 9-12) of part of the BRCA1 gene in three unrelated families of Mexican ancestry.

Major accomplishments:
Based on the above preliminary findings, we developed genetic tests for the BRCA1 large deletion and a panel of BRCA mutations common in the Hispanic population, including the BRCA1 185delAG mutation. The latter was so common that it accounted for 11% of all the positive test results, and was similarly common in other published reports that we reviewed. Using newly available technology we were able to more rapidly and cheaply screen for more common Hispanic BRCA mutations. Our prototype panel included 18 different mutations. Along with our new BRCA1 large deletion test, we used this panel to rapidly pre-screen Hispanic women with BC—it detected 57% of the BRCA mutations in this group of patients. We recruited >400 women for our studies.

Plans for continuation of the project:
We will revise our panel of common Hispanic BRCA mutations to include a total of 56 mutations that we predict will account for up to 90% of all BRCA mutations among Hispanic women undergoing genetic counseling and genetic testing for predisposition to breast and ovarian cancer. Our revised Hispanic mutation panel will also be used to pre-screen the high-risk clinic patients—if they have one of the common mutations a much cheaper confirmation test can be used-, if no mutation is found they will have the much more expensive full BRCA gene testing. As we have already proven in our initial project, our unique Hispanic BRCA mutation panel will help to reduce the cost associated with testing high-risk Hispanic individuals for BRCA mutations. As many of our high-risk clinics are caring for underserved Hispanic families, this will enable more women to benefit from limited resources. Knowledge of the ancestry of recurrent Hispanic BRCA mutations may make the panel more effective. Possible outcomes of this study include more efficient BC risk assessment for Hispanic women, which will allow them to choose the best way (increased breast cancer screening, healthier lifestyle choices, risk-reducing drugs, or surgery) to reduce the risk of advanced breast cancers


Symposium Abstract (2007)
Goal of the research project: Breast cancer is the most commonly diagnosed cancer in Hispanic women, and is the leading cancer cause of death in this population. Mutations in the BRCA genes are associated with 5-10% of breast cancer cases. The lifetime risk of developing breast cancer in individuals with a BRCA mutation may be as high as 85%. Large rearrangements, deletions or duplications of a portion of a gene that are not detectable by the standard sequencing test, account for up to 15% of deleterious BRCA mutations. There is little information on BRCA mutations in Hispanics. The purpose of this study was to identify rearrangements in the BRCA genes in a cohort of high-risk Hispanic patients.

Work performed to date: DNA from 106 Hispanic patients without an identifiable BRCA mutation by standard commercially available techniques was analyzed by a multiplexed quantitative differential PCR (MQDP), a new method to identify large rearrangements. Long range PCR was used to confirm deletion events and to clone and sequence genomic breakpoints, and splicing patterns were derived by sequencing cDNA from the RNA of affected individuals. The extent of shared chromosome markers (e.g. haplotype analysis) was conducted to confirm ancestral links among unrelated families with the same mutation.

Results to date: The same deletion of BRCA1 exons 9 through 12 was identified in five unrelated families. Long range PCR and sequencing indicated a deletion event of 14.7 kb. A 3-primer PCR assay was designed based on the deletion breakpoints, identified within repetitive sequence elements that are prone to rearrangements (AluSp in intron 8 and AluSx in intron 12). Haplotype analysis confirmed common ancestry. Analysis of cDNA demonstrated direct splicing of exon 8 to exon 13 resulting in a frameshift mutation and premature truncation of the BRCA1 protein, typical of deleterious mutations.

Potential impact of work on breast cancer research and patients: We identified and characterized a novel large BRCA1 deletion in five unrelated families–four of Mexican ancestry and one of African and Native American ancestry, suggesting common ancestry. This BRCA1 rearrangement was detected in 3.8% (4/106) of BRCA sequence negative Hispanic families and may account for a substantial proportion of high-risk Hispanic families. An assay for this mutation should be considered for BRCA sequence negative high-risk Hispanic patients. Additional studies are ongoing to determine the prevalence of this rearrangement among similar cohorts. Although the incidence of breast cancer in Hispanic women is less than that for non-Hispanic white women, the results of this study and of our previous work suggest that BRCA mutations may account for a higher proportion of the breast cancers in young Hispanic women.


Symposium Abstract (2010)

Raquel M. Ogaz, B.A.1 , Kathleen R. Blazer, M.S.1, Josef Herzog, B.S.1, Christopher Haiman, Ph.D.2, Rohit Varma, M.D.,2 Guillermo Rivas1, Garry Larson, Ph.D.1, Jeffrey N. Weitzel, M.D.1
1Division of Clinical Cancer Genetics, City of Hope, Duarte, CA
1University of Southern California, Los Angeles, CA

Breast cancer is the most common cancer and the leading cause of cancer death in Latina women. Mutations in BRCA genes are associated with 5% of all BC and a larger proportion of young women with BC. Large rearrangements, not detectable by standard sequencing, account for up to 15% of deleterious BRCA mutations. The lifetime risk of developing BC associated with a BRCA mutation may be as high as 85%. We previously reported on the prevalence of deleterious BRCA mutations (31% of 110 families) in a Latina high-risk clinic in Los Angeles, and also identified a unique recurrent large BRCA1 rearrangement (deletion of BRCA1 exons 9-12). BRCA1 185delAG was detected in independent Latina families, and through haplotyping we established that they shared a common ancestral origin with Jewish carrier families. We hypothesized that a panel of recurrent Latina BRCA mutations to pre-screen high risk patient samples will demonstrate clinical utility and reduce genotyping cost.

Using a new high-throughput Sequenom® platform, we developed a prototype multiplex panel to test for recurrent BRCA mutations, including 185delAG, and a 3-primer assay to test for the BRCA1 rearrangement mutation. We screened two population-based cohorts (combined n=2,702), the Multiethnic Cohort (MEC) and the La Puente Latino Eye Study (LALES) cohort. BRCA1 del (ex 9-12) was detected in the LALES cohort and BRCA2 3492insT, a known founder mutation of Spanish origin, was detected in both cohorts. We created a clinical protocol and procedure that enabled sample collection, DNA extraction, amplification and mutation panel analysis on the Sequenom platform within a 72 hour time frame. We piloted this 18 mutation panel in the clinical genetic cancer risk assessment setting. Positive assays were confirmed in a CLIA-approved laboratory by sequencing of the specific segment, and comprehensive BRCA sequencing was performed on all samples with negative results. We applied the panel prospectively in a pilot study of 23 consecutive Latina breast cancer patients referred to the City of Hope Cancer Screening & Prevention Program Network for genetic cancer risk assessment.

A substantial proportion (4/7, 57%) of deleterious BRCA mutations were detected by the panel in this proof of principle pilot study in our high risk clinic, suggesting strong translational potential. All 4 mutations were confirmed by commercial sequencing.  The majority of these patients were from an underserved/uninsured clinic, and the pre-screening procedure (with an estimated panel assay cost of $5/sample, and $250 for re-confirmation of detected mutations by the CLIA-certified commercial laboratory) saved an estimated $6,600 over the alternative of complete sequencing (representing a 15% savings on the budget for genotyping all 23 patients).

Our data suggest that the development of and testing for a panel of recurrent BRCA mutations in high risk Latina populations will reduce testing cost and enable more women to benefit from limited resources. Knowledge about the genetic etiology of breast cancer in Latinas will facilitate screening and cancer prevention.

Acknowledgements: CBCRP Grant #12IB-0050; NCI 1R03 CA139588



Evidence for common ancestral origin of a recurring BRCA1 genomic rearrangement identified in high-risk Hispanic families.
Periodical:Cancer, Epidemiology, Biomarkers and Prevention
Index Medicus: Cancer Epidemiol Biomarkers Prev
Authors: Weitzel JN, et al.
Yr: 2007 Vol: 16 Nbr: 8 Abs: Pg:1615-20