Scientists at The University of Texas Health Science Center at San Antonio (UT Health San Antonio), in collaboration with Dana-Farber Cancer Institute at Harvard Medical School, Columbia University and Irving Medical Center, have made a critical breakthrough in understanding why cancers with BRCA1 mutations become resistant to a widely used class of drugs known as PARP inhibitors – pharmacological inhibitors of poly ADP ribose polymerase (PARP), which plays a role in repairing DNA in damaged cells.