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BRCA Mutations and Breast Cancer Ruth Phillips and Patty Ashby Breast Cancer • Most common cancer in women • Second cause of cancer death in women • Rates in men??? BRCA1 and BRCA2 are Oncogenes • Cancer is caused by mutations in specific oncogenes. • Mutations in oncogenes change normal cells into cancer cells. • BRCA1 and BRCA2 are recessive oncogenes. Sporadic vs Inherited Breast Cancer • Usually breast cancer is the result of sporadic mutations but about 5% of cancer patient inherit a gene mutation which predisposes them to cancer. • Tumors develop when a second mutation occurs to make the individual homozygous for the mutation. This is called loss of heterozygosity (LOH). Increased risk for Carriers of BRCA1 and BRCA2 • Carriers for mutations in these two genes account for: • 50% of all early-onset cases • Increased risk for ovarian cancer in women and breast cancer in men • In families with known cases, risk of developing breast cancer is 80% by age 70 Two Types of Recessive Oncogenes These genes function as tumor suppressors in normal cells – Gatekeepers – regulate cell growth – Caretakers – repair DNA damage BRCA1 and BRCA2 • Both are caretaker genes – Code for two different proteins involved in DNA repair – Large genes with 24 – 27 exons – Mutations are found throughout the genes with 900 different mutations for each gene Pictures of 3D Structure of Normal and Mutations BRCA1 and BRCA2 • Cancer risk is influenced by type of mutation, modifier genes, and environmental and hormonal cofactors • The risk of developing cancer is not identical for all carriers of BRCA1 and BRCA2 mutations. • Likewise, the effectiveness of different cancer therapies might vary with the type of BRCA1 or BRCA2 mutation. Can genetic information be used to: • predict the best type of therapy for a breast cancer patient? • develop new individual-based therapies? Student Project Sequences from women from two ethnic groups with inherited breast cancer are provided: includes BRCA1 and BRAC2 mutations, and one normal sequence. Question 1: Compare sequences and look for patterns among the sequences Question 2: Can you identify mutations that might be causing the disease? Results of CLUSTALW Patient 7 Patient 3 Patient 1 Patient 4 Patient 6 Patient 5 Patient 2 Patient 9 Patient 8 Results of CLUSTALW BRCA2 BRCA2 BRCA2 BRCA1 BRCA1 BRCA1 BRCA1 BRCA2 BRCA2
