BRCA Sequencing

The human genes BRCA1 and BRCA2 produce tumor suppressor proteins that help repair damaged DNA playing a very important role ensuring the stability of genetic cell material. If the genes are mutated, the proteins will either not be produced or will not be functional. As a result, cells are more likely to develop additional genetic alterations that can lead to cancer.

In the general population, approximately 1 in 8 women (12%) will develop breast cancer in their lifetime, and 1 in 75 women (1.4%) will be diagnosed with ovarian cancer in their lifetime (SEER seer.cancer.gov/). Most cases of breast or ovarian cancers develop sporadically with no family history of the cancer. Individual risk factors and exposures, such as age, pregnancy history, menstrual history, benign breast disease, radiation exposure, and alcohol intake, are known to modify a woman’s chance of developing these types of cancers. However, 5-10% of breast cancer cases and 15-20% of ovarian cancer cases are thought to be due to a hereditary predisposition (1,2). BRCA1 ex9-12del seems to be a Mexican founder mutation and represents 10% to 12% of all BRCA1 mutations in clinic- and population-based cohorts in the United States. (3) In Ashkenazi Jews, there is a high population frequency (approximately 2%) of three founder mutations: BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT (4). This test is aimed to target these variations. Important to mention that the variation had been found in other non-Jewish ethnic groups such as: Austrian, Slovenian, Spanish, German, Czech, Hungarian, Greek Danish, Polish, Latvian, Lithuanian, Belarusian, Russian. (5)

BRCA Mutations
BRCA Gene Mutation Name SNP Number Gene Position
BRCA1 c.68_69 delAG rs386833395 Exon 2
BRCA1 c.5263_5264 insC rs80357906 Exon 20
BRCA2 c.5946 delT rs80359550 Exon 11

Soon the full sequence of BRCA1 and BRCA2 will be available.

Abnormal Test Sample Report

Test Description:

The analysis of common variants in the BRCA1 and BRCA2 genes is detected by automated DNA sequencing. The gene is analyzed by PCR-based double-stranded automated sequencing in the sense and antisense directions.

Specimen Requirements:

  • Specimen and Volume: Buccal epithelial cells collected on standard cotton tip swabs. Alternative acceptable specimens include 3-5 cc of blood in EDTA or ACD BD Vacutainer tubes guide. Other types of tissue may be accepted (please call 818-789-1033 to verify before sending).
  • Contact your doctor's office or FirmaLab for buccal swab kits. Buccal Swab Kit Instructions
  • Temperature: can be at room temperature the specimen needs to be at the laboratory no more then 72hrs. Do not freeze whole blood.
  • Turn around time: 7-10 days

Specimen Rejection Criteria: Below are general rejection criteria. If the specimen must be rejected based on the following criteria, or specific criteria for the requested test:

  1. The test requisition form has missing information. Requisition must contain the required information including:
    • Requesting party and referring authority, usually a healthcare professional.
    • Patient identifying information - Name or alias if anonymous;
    • Test requested, Clinical indication for testing;
    • Date and time of specimen collection;
    • Type of sample (e.g. whole blood or epithelial cells obtained by buccal swab);
    • All other identifying information (e.g. social security number, telephone number, hospital ID, sex … etc.) is optional, but useful for accurate differentiating between patients with similar names.
  2. Label is unclear;
  3. Blood specimen is from a recipient of bone marrow transplant;
  4. Specimen is inappropriate for test requested;
  5. Blood sample is clotted or hemolyzed;
  6. Incorrect container or Vacutainer used;

References

1. Claus EB, Schildkraut JM, Thompson WD, Risch NJ. The genetic attributable risk of breast and ovarian cancer. Cancer. 1996;77(11):2318–2324.

2. Pal T, Permuth-Wey J, Holtje T, Sutphen R. BRCA1 and BRCA2 mutations in a study of African American breast cancer patients. Cancer Epidemiol Biomarkers Prev. 2004;13(11 pt 1):1683–1686.

3. Weitzel JN, Lagos VI, Herzog JS, et al. Evidence for common ancestral origin of a recurring BRCA1 genomic rearrangement identified in high-risk Hispanic families. Cancer Epidemiol Biomarkers Prev. 2007;16:1615–1620.

4. Levy-Lahad E, Catane R, Eisenberg S, et al. Founder BRCA1 and BRCA2 mutations in Ashkenazi Jews in Israel: frequency and differential penetrance in ovarian cancer and in breast-ovarian cancer families. American Journal of Human Genetics. 1997;60(5):1059-1067.

5. Janavičius R. Founder BRCA1/2 mutations in the Europe: implications for hereditary breast-ovarian cancer prevention and control. The EPMA Journal. 2010;1(3):397-412. doi:10.1007/s13167-010-0037-y.

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