ANN ARBOR, Mich. — For decades, the primary strategy in the fight against advanced prostate cancer has centered on a single biological vulnerability: the androgen receptor. By starving tumors of the hormones they need to grow, clinicians have been able to extend the lives of countless patients. However, cancer is a master of adaptation, and for many men, the disease eventually finds a way to survive without the very receptor that once fueled its progression. When this happens, the cancer becomes significantly more aggressive and far more difficult to treat.
Researchers at the University of Michigan Rogel Cancer Center have now announced a significant breakthrough in understanding this transition. In a study published in the Journal of Clinical Investigation, the team identified a specific gene, PROX1, that plays a pivotal role in prostate cancer cells that have evolved past their reliance on the androgen receptor. Perhaps most importantly, the researchers discovered that this gene can be indirectly targeted using an existing class of drugs, offering a potential lifeline for patients facing the most lethal subtypes of the disease.
The discovery addresses a phenomenon known as lineage plasticity. In the context of oncology, lineage plasticity describes a process where cancer cells shed their original identity—in this case, that of a typical prostate cell—and take on new characteristics that allow them to evade standard therapies. As these cells move away from their dependence on the androgen receptor, they enter a continuum of alternate identities, often becoming what is known as "double-negative" prostate cancer or the even more aggressive neuroendocrine prostate cancer.
"Patients whose prostate tumors lose reliance on the androgen receptor do poorly," said the study’s senior author, Joshi J. Alumkal, M.D., the Wicha Family Professor of Oncology at the University of Michigan Rogel Cancer Center. "Our results suggest a therapeutic approach for patients whose tumors have undergone that shift."
The research, led by Zhi Duan, Ph.D., began by looking for the specific factors that trigger this dangerous cellular transformation. By examining tumor biopsies from patients whose cancer had already undergone lineage plasticity, the team sought to identify which genes were working overtime. Their analysis pointed toward PROX1 as the most significantly upregulated gene in these resistant tumors.
PROX1 is a transcription factor, a type of protein that acts as a master switch by dictating which genes are turned on or off within a cell. While it is known to help determine cell identity in healthy tissues, its role in the progression of prostate cancer had not been fully realized. To confirm their findings, the University of Michigan team examined hundreds of patient tumor samples across the entire spectrum of the disease. They found that PROX1 serves as an early marker of lineage plasticity, appearing even before the cancer has fully transitioned into its most resistant forms.
The study revealed a stark inverse relationship: as PROX1 levels rise, androgen receptor expression falls. In laboratory experiments, when the researchers artificially introduced PROX1 into prostate cancer cells, those cells began to shut down their androgen receptors, mimicking the transition seen in the most difficult-to-treat clinical cases.
