The work, carried out by a multidisciplinary team and published in the British Journal of Cancer, focuses on the interplay between androgen receptor signaling and the machinery that mends double‑strand DNA breaks. Androgen receptor pathway inhibitors—enzalutamide, apalutamide, and darolutamide—are mainstays of advanced prostate cancer care. They throttle the receptor that drives tumor growth, but the new data reveal a far more profound secondary effect: a profound, orchestrated suppression of the homologous recombination repair apparatus. In essence, the drugs chemically castrate the cancer cell’s ability to faithfully stitch broken DNA back together.

Through a battery of functional assays, the researchers documented that prolonged exposure to androgen receptor blockade forces prostate cancer cells into a state of chronic DNA damage. Comet assays and γH2AX focus formation—direct measures of DNA fracture—spiked dramatically after treatment. The cells did not simply accumulate breaks; they became unable to deploy RAD51, the central recombinase protein that searches for intact sister chromatid templates during repair. Immunofluorescence imaging showed that RAD51 foci, the microscopic repair factories, failed to form even after ionizing radiation challenge, a classic test of homologous recombination competence. The functional defect was indistinguishable from that seen in cells harboring bona fide BRCA2 mutations.

To understand what was happening beneath the surface, the group layered on an omics‑scale lens. Transcriptomic profiling revealed that enzalutamide and its cousins not only downregulated a constellation of HR genes—including BRCA1, BRCA2, PALB2, and RAD51 itself—but also physically rewired the epigenome at their promoter regions. ATAC‑seq data confirmed that chromatin accessibility slammed shut at critical regulatory elements, effectively silencing the repair genes. Simultaneously, proteomic analysis showed a shift toward error‑prone alternative end‑joining pathways, leaving cells reliant on backup repair mechanisms that create genetic scars. This molecular signature, they argue, is the functional equivalent of a BRCA‑mutant state: a clinically actionable “BRCAness” induced on demand.

The translational implications snap into focus when PARP inhibitors enter the frame. PARP traps are exquisitely lethal to cells that cannot repair replication‑associated single‑strand breaks through homologous recombination, a concept called synthetic lethality. The team tested the two‑drug sequence in a panel of prostate cancer cell lines, including those verified to have wild‑type HRR genes. The combination index plummets into strong synergy in every model. PARP inhibitor olaparib, which shows minimal single‑agent activity against HRR‑proficient cells, suddenly slashes viability when administered after an androgen receptor pathway inhibitor lead‑in. In 3D organoid cultures derived from patient biopsies that lacked any HRR gene alterations, the same sequential treatment caused organoid disintegration within days. Mouse xenograft studies extended the narrative to living systems: tumors subjected to the combination regressed significantly, whereas either drug alone merely slowed growth.

Crucially, the team observed that the induced BRCAness is not permanent. Washout experiments demonstrated that RAD51 foci formation resumes within days after withdrawing the androgen receptor inhibitor, and the sensitivity to PARP inhibition wanes in lockstep. This pharmacodynamic reversibility is a double‑edged sword. It implies that therapeutic scheduling will be paramount; continuous dosing or carefully timed cycles may be necessary to trap tumor cells in the vulnerable window. The window appears wide enough, however, that standard intermittent regimens could be tailored to maximize synergy without irreversible toxicity to normal tissues, which retain intact repair machinery and appear to recover quickly.

The omics backbone of the study provided an additional treasure: a candidate biomarker panel that could track the depth of induced BRCAness in patients. Circulating tumor cell analysis and liquid biopsy signatures, including a decline in BRCA1 mRNA fragments and a rise in microRNAs linked to DNA damage response, correlated with the degree of HR suppression in preclinical models. The researchers are already designing a co‑clinical trial in which serial blood draws will attempt to pinpoint the moment of maximum vulnerability, allowing oncologists to time the PARP inhibitor attack with precision never before achievable in solid tumors.

If validated in humans, the strategy would overturn the current paradigm of genetic preselection. Today, men with metastatic castration‑resistant prostate cancer must undergo complex next‑generation sequencing and be allotted PARP inhibitors only if a panel of 15 or so HRR genes shows a qualifying aberration. The new concept discards the sequencing ticket entirely. By deliberately creating the very defect that the drug was designed to exploit, clinicians could deliver synthetic lethality to the entire treated population, potentially eliminating the need for expensive and time‑consuming biomarker testing.

The implications radiate beyond prostate cancer. Breast, pancreatic, and ovarian tumors that rely on hormone signaling or similar chromatin‑modifying pathways might also be coaxed into a BRCA‑like state. The study’s senior authors point out that other receptor tyrosine kinase inhibitors are already being screened for their ability to downregulate DNA repair genes, raising the possibility of a broader class of “BRCA‑inducing” agents. As the first functional and multi‑omic dissection of pharmacologically induced BRCAness, the paper delivers both a detailed mechanistic roadmap and a practical therapeutic schedule, accelerating a concept that could turn the largest fraction of patients into candidates for some of oncology’s most powerful targeted agents.

Subject of Research: Induction of BRCAness phenotype by androgen receptor pathway inhibitors to sensitize prostate cancer to PARP inhibitors irrespective of HRR gene status.

Article Title: Functional and omics-based rationale for the induction of BRCAness by androgen receptor pathway inhibitors to sensitize prostate cancer to PARP inhibition, regardless of HRR status.

Article References:

Elsesy, M.E., Moustafa, A., Oh-Hohenhorst, SJ. et al. Functional and omics-based rationale for the induction of BRCAness by androgen receptor pathway inhibitors to sensitize prostate cancer to PARP inhibition, regardless of HRR status.
Br J Cancer (2026). https://doi.org/10.1038/s41416-026-03518-7

Image Credits: AI Generated

DOI: 10.1038/s41416-026-03518-7

Keywords: Prostate cancer, PARP inhibitors, BRCAness, androgen receptor pathway inhibitors, homologous recombination repair, synthetic lethality, DNA damage response, enzalutamide, olaparib, functional genomics, epigenetic silencing, RAD51, precision oncology.