The battle against ovarian cancer has long been hindered by the failure of anti-estrogen therapy, even when tumors express the hormone receptor that should make them responsive. But a breakthrough discovery by scientists at The Wistar Institute has shed light on this puzzle, offering a glimmer of hope for more effective treatment strategies.
Unveiling the Mystery of Treatment Resistance
In a recent study published in Genes & Development, researchers revealed that mutant p53, present in 96% of high-grade serous ovarian cancers, plays a crucial role in blocking estrogen signaling, leading to treatment resistance. This finding is a game-changer, as it fundamentally alters our understanding of hormone therapy resistance in ovarian cancer.
"We've not only unraveled the reason behind treatment failures but also identified a potential solution," said Maureen Murphy, Ph.D., a leading researcher at The Wistar Institute. "For patients with specific p53 variants, we can potentially combine existing FDA-approved drugs to overcome resistance."
The Challenge of Hormone Therapy
High-grade serous ovarian cancer is an aggressive form of the disease, with an alarming 80% relapse rate after initial chemotherapy. Despite nearly three-quarters of these tumors expressing estrogen receptors, clinical trials of hormone-blocking drugs have shown a disappointing clinical benefit rate of only 41%.
Murphy's journey to uncover this discrepancy began with an unexpected discovery during her research on genetic variants of p53 in people of African descent. Her team's analysis of blood samples from carriers of these variants revealed dampened activity in estrogen-responsive genes, prompting them to delve deeper into the connection between p53 and estrogen receptors.
Unraveling the Role of Mutant p53
In their latest study, Murphy's team found that the mutant p53 protein binds to estrogen receptors, disrupting a critical hormone signaling pathway. This binding renders the tumor resistant to hormone treatments. Through collaborations with key consortium partners, the researchers obtained human ovarian cancer cells and patient tissue samples to test their hypothesis.
"When we silenced mutant p53, previously resistant tumors responded to treatment," Murphy explained. "We confirmed these findings in the earliest stages of ovarian cancer, thanks to our collaboration with Ronny Drapkin at the University of Pennsylvania."
Promising Drug Combinations and Future Directions
The most exciting development came when the team tested a compound called rezatapopt. This drug has the ability to refold a specific variant form of p53, known as Y220C, back into its normal shape. When combined with hormone therapy, tumors with this mutation became significantly more responsive to treatment.
The good news is that rezatapopt is already undergoing clinical trials at Penn and other institutions, which means this combination approach could be tested in patients sooner rather than later. Moreover, the findings have broader implications for other hormone-driven cancers, potentially explaining why endocrine therapy sometimes fails in breast cancer patients with p53 mutations.
Murphy's team is now focused on expanding their research to include other variant forms of p53 and developing more precise methods to identify patients who would benefit most from p53-targeted combination treatments.
"Our ultimate goal is to translate this laboratory discovery into a clinical tool that directly benefits patients," Murphy emphasized. "We've demonstrated the scientific principle, and now we're working to develop treatment protocols that oncologists can use to improve patient outcomes."
The study, "Mutant p53 binds and controls estrogen receptor activity to drive endocrine resistance in ovarian cancer," is available in Genes & Development (2025). DOI: 10.1101/gad.352953.125
