A groundbreaking study led by scientists at NYU Langone Health has uncovered the molecular mechanism behind why PARP inhibitors—a class of precision cancer drugs—are effective in only certain cancer patients. The research, recently published in Nature, reveals an unexpected role for the major cancer gene BRCA2 in determining treatment outcomes.
The BRCA2-PARP1 Connection
As human cells divide and grow, DNA damage occurs continuously and must be swiftly repaired to prevent cancer. BRCA2 plays a crucial role in homology-directed repair, a key DNA repair mechanism. When mutations compromise BRCA2 function, cancer cells rely on the poly ADP-ribose polymerase 1 (PARP1) pathway for backup DNA repair to continue their abnormal growth.
The NYU Langone team discovered that BRCA2 functions as a molecular shield, physically preventing PARP1 from remaining stuck at DNA repair sites—the very mechanism by which PARP inhibitors exert their therapeutic effect.
"This finding would not have been possible without the specialized imaging tools pioneered by the Single Molecule Biophotonics program here," said Dr. Eli Rothenberg, senior study author and professor in the Department of Biochemistry and Molecular Pharmacology at NYU Grossman School of Medicine. "They gave us a molecular window into how BRCA2 protects DNA repair complexes from disruption in living human cells in real time."
Molecular Shield Mechanism
Using single-molecule imaging techniques, researchers observed that intact BRCA2 ensures that RAD51—a protein essential for accurate DNA repair—can access repair sites instead of PARP1 and carry out its function. This prevents the treatment-generated buildup of harmful DNA breaks in cancer cells that resist PARP inhibition.
Conversely, in cells with defective BRCA2, PARP1 freely binds to and persists at DNA damage sites. This blocks RAD51 access and halts proper repair, causing fatal damage to cancer cells—explaining why BRCA2-deficient tumor cells are more vulnerable to PARP inhibitors.
"The finding that variable BRCA2 activity dictates PARP inhibitor efficacy points to the need for patient-specific tumor profiling and may inform how clinicians select therapies," explained Dr. Sudipta Lahiri, first study author and postdoctoral fellow at NYU Langone.
Clinical Implications for Multiple Cancer Types
The prevalence of BRCA2 mutations varies across cancer types, with approximately 15-20% of ovarian cancers, 6-8% of breast cancers, and 8-10% of both prostate and pancreatic cancers featuring either inherited BRCA2 mutations or those that arise during tumor development.
This research complements clinical findings on PARP inhibitors like olaparib, which has shown effectiveness against advanced pancreatic and prostate cancers in patients with BRCA mutations. In the largest clinical trial examining PARP inhibitor therapy in BRCA1/2 carriers with diseases beyond breast and ovarian cancer, researchers found that 22% of pancreatic cancer patients and 50% of prostate cancer patients responded to olaparib therapy.
"Our results show that the BRCA1 or BRCA2 genes inherited by some patients can actually be the Achilles heel in a novel, personalized approach to treat any type of cancer the patient has," noted Dr. Susan Domchek, director of Penn's Basser Research Center for BRCA, commenting on related clinical research.
Future Directions
The NYU Langone team is now focusing on translating this mechanism into clinical applications. They are examining the structure of BRCA2 domains involved in shielding repair complexes from PARP1, with the goal of designing therapies that overcome resistance.
This work is part of a larger effort across NYU Langone and Perlmutter Cancer Center to connect molecular discovery with clinical advances. Through collaborations with clinical teams, researchers aim to translate insights about BRCA-related pathways into actionable diagnostics and new treatment strategies.
The study was supported by multiple National Institutes of Health grants and additional funding from the V Foundation, the Gray Foundation, and other organizations.
