Answer- Case study- Breast lump

A 23-year-old woman is seen for a lump in her breast that she palpated on self breast examination. History reveals that her mother and her aunt both had breast and ovarian cancer. Given this presentation, it is suspected that the patient might be having a mutation in which of the following genes involved in DNA repair?

A. BRCA-1

B. p53

C. Rb

D. p10

E. ras

Answer- The correct answer is- A.

BRCA- 1 gene is implicated in breast and ovarian cancer. A major cause of familial breast cancer results from mutation in the breast cancer susceptibility gene, BRCA1. BRCA1 gene product is a nuclear protein. that functions as a cell cycle regulator in response to DNA damage.

Cells defective in BRCA1 possesses numerous cytological and biological features that have been correlated with perturbation in the maintenance of chromosome stability. The BRCA1 tumor suppressor interacts with numerous cellular proteins in large complexes. This includes a variety of proteins implicated in various DNA repair and cell cycle processes. In fact, BRCA1 has been reported to interact with as many as 50 proteins.  Moreover, BRCA1 has been shown to function in various transcriptional mechanisms, suggesting that the function of this important protein may go well beyond its well-documented role in Double Strand Break repair.

BRCA-1

Figure- The human BRCA1 gene is located on the long (q) arm of chromosome 17

How the inactivation of BRCA1 predisposes women to inherited forms of breast cancer, remains a mystery and the subject of much debate. Given that BRCA1 appears to have key roles in transcriptional regulation, it has been suggested that BRCA1 could influence mammary tissue through pathways that impinge on the biology of estrogen and estrogen-related metabolites. In addition, it has been suggested that breast tissue differs from other tissues in the types of DNA repair processes that are used. Perhaps there are redundant DNA repair pathways in non-mammary tissue. In any event, the complex behavior of BRCA1 promises to challenge future researchers as they search for the underlying mechanisms that initiate familial breast cancer.

p 53 is another DNA repair gene but p10 and Rb gene products  are not involved in DNA repair mechanisms.

Mutations in one of the RAS genes (HRAS, KRAS, or NRAS) are present in up to 85% of pancreatic cancers and 50% of colon cancers but are relatively uncommon in other cancer types. RAS gene is also not involved in DNA repair mechanisms.

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