Most inherited cases of breast cancer are associated with two gene mutations: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two). Women with a mutated BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. Their risk of ovarian cancer also is higher than average. Men with a BRCA gene mutation have a higher risk of both breast and prostate cancer.
DNA carries genetic information in both healthy cells and cancer cells. Cells can develop DNA damage spontaneously or from exposure to specific things in the environment (too much sun, for example) that make DNA damage more likely to happen. But cells can detect and repair damage to DNA. When DNA is damaged in a healthy cell and the damage isn't fixed, that cell can become cancerous. The function of the BRCA genes is to keep breast cells growing normally and prevent any cancer growth. But if there is a mutation in the BRCA1 or BRCA2 gene, it increases the risk of breast and other cancers because these gene mutations interfere with cells' ability to repair damaged DNA.
The poly ADP-ribose polymerase (PARP) enzyme fixes DNA damage in both healthy and cancer cells. Research has shown that a medicine like Lynparza, which interferes with (inhibits) the PARP enzyme, makes it even harder for cancer cells with a BRCA1 or BRCA2 mutation to fix DNA damage. This makes it harder for the cancer cells to survive. In other words, a PARP inhibitor makes some cancer cells less likely to survive their DNA damage.