CBD Alters Gene Regulation in Prostate Cancer Cells

Cannabidiol is frequently discussed as though its biological effects can be reduced to interactions with cannabinoid receptors. A new laboratory study published in Biomedicine & Pharmacotherapy¹ suggests that the picture may be considerably more complex.

Researchers at University College Dublin and University College Cork found that CBD altered DNA methylation, gene expression, and important growth pathways in prostate cancer cells. It also enhanced the effects of several targeted and hormonal drugs under laboratory conditions.

The results do not show that CBD treats prostate cancer in people. The experiments were performed in isolated cell lines, without the metabolism, immune system, tumour environment, and safety constraints that influence treatment in a living patient. However, the findings identify several mechanisms that could help researchers determine whether CBD has a legitimate future as an adjunct to established cancer therapies.

Why Prostate Cancer May Be Sensitive to Epigenetic Changes

Prostate cancer is strongly influenced by androgen signalling. Androgens, including testosterone, activate the androgen receptor and help regulate prostate cell growth. This dependence is why androgen deprivation and androgen receptor inhibitors are central components of treatment for many patients.

These therapies can initially be effective, but tumours frequently adapt. Some eventually progress to castration-resistant prostate cancer, in which the disease continues growing despite efforts to suppress androgen signalling.

Genetic mutations are only one part of this adaptation. Prostate cancer is also characterized by widespread epigenetic changes. Epigenetics refers to chemical and structural modifications that affect whether genes are active without changing the underlying DNA sequence.

One important mechanism is DNA methylation, in which methyl groups are attached to DNA. Depending on their location, these marks can reduce or otherwise modify gene activity. Cancer cells can exploit abnormal methylation patterns to silence protective genes, support uncontrolled growth, and adapt to treatment.

This makes the epigenome an important target for prostate cancer research. If CBD can alter these regulatory patterns, its relevance may extend beyond the conventional explanation that cannabinoids work primarily through CB1 and CB2 receptors.

How Researchers Tested CBD

The researchers studied three prostate cancer cell lines. LNCaP cells represented hormone-dependent disease, while PC3 and DU145 cells represented hormone-independent forms. The cells were exposed to synthetic CBD at concentrations selected according to the amount required to reduce cell viability by approximately half.

The team then used several analytical methods to examine the results. DNA methylation arrays measured changes across hundreds of thousands of sites. RNA sequencing tracked gene expression, while protein and enzyme assays examined regulators including EZH2, an epigenetic protein associated with aggressive prostate cancer.

The study also tested CBD in combination with three drugs:

• Enzalutamide, an established androgen receptor inhibitor
• Talazoparib, a PARP inhibitor used in selected prostate cancers
• GSK126, an experimental inhibitor of EZH2 activity

This design allowed the researchers to move beyond asking whether CBD reduced cell viability. They could investigate how its effects differed by cancer subtype and whether it complemented therapies acting on related molecular pathways.

CBD Produced Different Epigenetic Effects by Cell Type

The clearest DNA methylation response occurred in hormone-dependent LNCaP cells. CBD exposure produced 372,837 statistically significant differentially methylated probes. When the researchers applied a threshold for the magnitude of these changes, substantially more sites became hypermethylated than hypomethylated.

The team also identified 26,342 differentially methylated regions associated with 3,927 genes. Many of those genes were connected to neural processes or the regulation of gene expression.

Independent testing reinforced this finding. Total levels of 5-methylcytosine, a common measure of DNA methylation, increased by 84.44% at the CBD concentration that reduced viability by half. At half that concentration, the increase reached 101.80%.

PC3 and DU145 cells did not show comparable changes in total DNA methylation. This difference is important because it suggests that CBD does not produce a single, uniform epigenetic response across prostate cancer. Hormone dependence and other features of the tumour may determine which molecular effects occur.

Cell-Cycle Suppression May Be the Shared Mechanism

Although the methylation response varied sharply among the cell lines, CBD changed gene expression in all three. The magnitude ranged from 353 affected genes in DU145 cells to 5,468 in LNCaP cells.

Pathway analysis showed that many of the most consistently suppressed processes involved DNA replication, cell division, and the cell cycle. CBD reduced the expression of CDK1, CDK2, and CCND3 across all three models. It also reduced CDK4 and CCNE1 expression in LNCaP cells.

These genes help cells move through the checkpoints that control division. Suppressing them could slow proliferation or prevent damaged cells from continuing to reproduce. This provides a plausible explanation for CBD’s effects on cell viability, even in cell lines that did not exhibit extensive DNA methylation changes.

The distinction is useful. It suggests that epigenetic remodelling may be especially important in hormone-sensitive cancer, while disruption of cell-cycle activity could be a more broadly shared response.

The Effects Did Not Depend on CB1 or CB2

None of the three prostate cancer cell lines expressed detectable CNR1 or CNR2, the genes encoding the canonical CB1 and CB2 cannabinoid receptors. CBD also did not cause cells to begin expressing receptors that were previously absent.

This reinforces an increasingly important lesson in cannabinoid research: CBD can influence cellular activity through mechanisms that do not require the best-known cannabinoid receptors.

Other possible routes include ion channels, nuclear receptors, membrane transporters, oxidative stress, and changes to gene-regulating proteins. The current study did not determine exactly how CBD entered the cells or initiated every downstream response. It did, however, find changes involving PPARG, TRPM8, and ABCA1 that could help guide future investigations.

This receptor-independent activity also helps explain why CBD findings can differ substantially among tissues and diseases. The compound may engage different molecular machinery depending on which receptors, enzymes, transporters, and regulatory pathways a particular cell expresses.

CBD Altered the EZH2 and Androgen Receptor Axis

CBD reduced gene and protein expression of EZH2 in all three cell lines. EZH2 is part of a protein complex that regulates chromatin structure and gene activity, and elevated EZH2 is associated with aggressive prostate cancer and poorer outcomes.

Surprisingly, the decline in EZH2 expression did not produce a measurable reduction in its methyltransferase activity. This indicates that CBD was not functioning like a straightforward EZH2 inhibitor.

EZH2 also has regulatory functions that are independent of its catalytic activity. In hormone-dependent LNCaP cells, CBD slightly increased androgen receptor gene expression while reducing the androgen-responsive genes KLK2, KLK3, and TMPRSS2. KLK3 encodes prostate-specific antigen, commonly known as PSA.

The researchers propose that lowering EZH2 abundance may disrupt its relationship with androgen receptor signalling even when its enzyme activity remains intact. This is a more nuanced mechanism than simply switching an epigenetic enzyme on or off.

Combination Therapy Produced the Most Clinically Relevant Signal

The most compelling result emerged when CBD was combined with enzalutamide. The androgen receptor inhibitor enzalutamide prevents androgen signalling from stimulating prostate cancer cells.

In hormone-responsive LNCaP cells, enzalutamide and CBD reduced viability to approximately 23% of the untreated control. That represented a 54% reduction relative to enzalutamide alone.

CBD also improved the activity of the other tested agents. Combining it with GSK126 produced additive effects in all three cell lines, including a further 16.35% reduction in PC3 cell viability compared with GSK126 alone. CBD and talazoparib produced an additive response in LNCaP cells and a synergistic response in BRCA1-mutant DU145 cells, where the combination reduced viability by a further 24% compared with talazoparib alone.

These results complement earlier cannabinoid research while showing why combinations cannot be assumed to work. A previous MyCannabis analysis found that CBD interacted antagonistically with cisplatin in a melanoma model under certain conditions. Another report examined how CBD altered immune activity in colorectal cancer research.

Together, these studies show that CBD may enhance, weaken, or otherwise change a treatment response depending on the cancer, drug, dose, and biological context. Synergy observed with one therapy cannot be generalized to chemotherapy or cancer treatment as a whole.

Why Laboratory Synergy Is Not a Treatment Recommendation

The study did not involve patients, animals, whole tumours, or commercially available CBD products. Cell viability assays measure metabolic activity in cultured cells, which is useful for screening but cannot establish tumour shrinkage, survival benefits, or tolerable human dosing.

The CBD concentrations used in laboratory research may also be difficult to reproduce safely in prostate tissue. Human metabolism can transform or remove CBD before it reaches a tumour, while product purity and absorption vary widely.

Drug interactions present another concern. The FDA warns that CBD can affect how other medications work, potentially changing their concentrations or side-effect profiles. That concern is especially significant during cancer treatment, where precisely controlled drug exposure can be essential.

Patients should therefore not add CBD to prostate cancer therapy based on these findings. The appropriate next steps are mechanistic studies, animal models, pharmacokinetic testing, toxicity assessment, and carefully designed clinical trials.

A Better Framework for Cannabinoid Cancer Research

The study’s broader contribution is methodological. Rather than describing CBD as universally anticancer, it demonstrates that the response depends on the biological subtype being tested. Hormone-dependent cells showed extensive methylation changes and altered androgen-related signalling, while hormone-independent cells displayed different molecular responses.

This points toward a biomarker-driven model for future cannabinoid research. Researchers may need to identify tumour characteristics that predict response, such as androgen receptor status, BRCA mutations, EZH2 expression, or particular transporter profiles. CBD would then be evaluated in defined patient groups and alongside specific drugs, rather than as a general cancer remedy.

Such precision is essential if cannabinoids are to progress from promising laboratory compounds to credible therapeutic candidates. This study does not establish CBD as a prostate cancer treatment. It does provide a detailed molecular map showing where the next investigations should begin.

References:

¹ Cosgrave, J., Magee, R., O’Reilly, E., Hughes, C., Jordan, A., Silva, R., McCabe, A., Dean, K., Prencipe, M., Gallagher, W. M., & Perry, A. S. (2026). Cannabidiol alters the epigenome of hormone-dependent prostate cancer cells. Biomedicine & Pharmacotherapy, 203, 119891. https://doi.org/10.1016/j.biopha.2026.119891