A new study from researchers 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, has uncovered a crucial mechanism behind resistance to PARP inhibitors in BRCA1-deficient cancers.

The research offers potential new avenues for developing more effective and personalized cancer treatments.

It is estimated that approximately one in 300 individuals in the United States carries a mutation in either the BRCA1 or BRCA2 gene. These genes play a vital role in DNA repair,and mutations significantly elevate the risk of developing cancers,including breast,prostate,and ovarian cancers.

PARP inhibitors are frequently used to treat these cancers by preventing cancer cells from repairing their damaged DNA. However, resistance to these drugs often develops over time, limiting their long-term effectiveness.

Patrick sung, DPhil, director of the Greehey Children’s Cancer Research Institute and associate dean for research at the Joe R. and Teresa Lozano Long School of Medicine at UT Health San Antonio,who co-led the study,stated,”Of all the things we have done,this one has the most impact on clinical practice over the long run. Everyone expects malfunction in these proteins to give rise to drug resistance, but they do not know why and how.”

The study,published in Science on May 22,details how issues within the CST complex,a critical component of DNA repair,can lead to PARP inhibitor resistance in BRCA1-deficient cancer cells.

Robert Hromas, MD, FACP, dean of the Joe R. and Teresa Lozano Long School of Medicine at UT Health San Antonio, commented, “This seminal discovery opens the door to understanding how some breast, prostate and ovarian cancers become resistant to an critically important class of cancer drugs called the PARP inhibitors. these drugs can generate tumor regressions lasting years, but ultimately almost everyone relapses due to resistance.”

The Role of the CST Complex

The CST complex, comprised of three proteins, plays a crucial role in DNA repair by directing the cell to use a specific repair pathway. When functioning correctly, PARP inhibitors can effectively target and kill BRCA-deficient cancer cells by preventing them from repairing their DNA. However, if the CST complex is mutated or silenced, cancer cells can bypass the effects of PARP inhibitors and continue to grow.

“This seminal discovery opens the door to understanding how some breast, prostate and ovarian cancers become resistant to an important class of cancer drugs called the PARP inhibitors.”

Sung emphasized, “This is a crucial first step to providing an intellectual framework to understanding why defects in this particular complex, and other proteins associated with this complex, can lead to cancer-drug resistance. This will also form the basis of finding compounds that interfere with protein function or enhance the stability of DNA-bound protein complexes to boost the therapeutic efficacy of PARP inhibitors and other cancer drugs.”

Future Implications

The findings from this research pave the way for the progress of future therapies designed to overcome PARP inhibitor resistance. By targeting the CST complex,treatments could be tailored to individual patients,offering a more personalized approach to cancer care.