To understand PARP and PARP inhibitors, it helps to know about DNA. Every cell in our bodies contains DNA, which is like a blueprint that tells the cell how to function. Over time, DNA can be damaged by the environment, normal aging, and many other factors. This damage results in hundreds of thousands of tiny breaks in the DNA. Usually, healthy cells can easily repair these breaks. When cells are unable to repair the breaks, the cells can die.
The BRCA gene creates a protein that helps DNA repair itself. If the BRCA gene is damaged, the repair process doesn’t work the way it should. Instead, the repair process sometimes creates cancerous cells. People who inherit a damaged BRCA gene are at increased risk for developing breast cancer, ovarian cancer and certain other cancers.
Another protein involved in DNA repair is PARP, or poly(ADP-ribose)polymerase. The PARP protein travels along DNA looking for breaks. When it finds these breaks, it repairs them.
PARP inhibitors prevent PARP from doing its job. While we wouldn’t want to prevent PARP from doing its job in healthy cells, preventing it in cancerous cells might be beneficial. Researchers believe that certain PARP inhibitors can target cancerous cells, preventing them from repairing themselves and causing them to die. These PARP inhibitors do not stop healthy cells from repairing their DNA. In clinical research studies, PARP inhibitors have been able to decrease tumor size and prolong the time to recurrence of cancer in patients who have a damaged BRCA gene.