A key, previously overlooked protein may reshape our understanding of prostate cancer biology. In a collaborative study by Arc Institute, UCSF, and Fred Hutchinson Cancer Center, PTGES3—the so-called third prostaglandin E synthase protein—emerges as an unexpected regulator of the androgen receptor (AR). The findings, published November 5 in Nature Genetics, suggest PTGES3 may not function primarily as an enzyme and could serve as a novel therapeutic target for aggressive, hormone-resistant prostate cancers.
Discovery Through Real-Time AR Tracking
The researchers engineered a fluorescent tag to monitor AR levels in real time, enabling genome-wide CRISPR screens in aggressive prostate cancer cells. AR, a hormone-sensing protein essential for prostate development, becomes highly amplified in cancer and drives tumor progression, making it a central target of current treatments. The tagging approach validated known AR regulators such as HOXB13 and GATA2, confirming the method, while revealing PTGES3 as a surprising regulator.
The screens showed that turning off PTGES3 reduced AR levels, and among the trio of prostaglandin-synthesizing enzymes, PTGES3 was uniquely impactful. This observation led the team to hypothesize a role for PTGES3 beyond its presumed enzymatic activity.
Ptges3’S Dual Mechanism In Cancer Cells
Patient data analysis indicated that high PTGES3 expression correlates with poorer outcomes after hormone therapy, highlighting its clinical relevance. In mouse models, PTGES3 suppression slowed tumor growth and lowered AR levels within tumors, supporting its potential as a therapeutic target in treatment-resistant disease.
The team proposes that PTGES3 operates via two complementary pathways:
As a co-chaperone in the cytoplasm, PTGES3 helps stabilize the AR protein.
As a nuclear co-factor, PTGES3 facilitates AR binding to DNA and activation of AR target genes.
These dual roles suggest that AR-driven tumor growth may depend on PTGES3’s support, making disruption of this interaction an attractive strategy for countering resistant cancers.
Implications For Therapy And Future Directions
This work demonstrates the power of unbiased CRISPR screening to redefine what a well-studied protein does in cancer biology. The study also points toward developing therapeutics that target the AR–PTGES3 interaction, including strategies to degrade PTGES3 or block its interaction with AR. Such approaches could complement or overcome limitations of current hormone therapies.
The researchers are pursuing structural analyses to detail how PTGES3 engages AR, with an eye toward translating these insights into targeted treatments. They envision a pipeline that may extend to other transcription factors implicated in hormone-driven cancers, using PTGES3 as a model for discovering non-canonical regulators of transcription factor stability.
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