Cannabidiol and THC show synergistic anti-cancer effects in ovarian cancer cell models

Ovarian cancer remains one of the most lethal gynecologic malignancies, largely because it is often diagnosed at an advanced stage and frequently develops resistance to standard therapies. Despite advances in surgery and chemotherapy, long-term survival rates have improved only modestly, underscoring the need for new treatment strategies that are both effective and tolerable. Against this backdrop, researchers are exploring whether compounds derived from cannabis could offer a novel therapeutic approach.¹

A new laboratory study published in Frontiers in Pharmacology evaluated the anti-cancer effects of cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) in ovarian cancer cell lines, including models that are both sensitive and resistant to platinum-based chemotherapy. The findings suggest that these cannabinoids, particularly when used in combination, may inhibit tumor cell growth, survival, and migration through effects on key cellular signaling pathways.^1,2

“Ovarian cancer remains one of the deadliest gynecological malignancies, characterized by late diagnosis, high recurrence rates, and limited effective treatment options,” said Siyao Tong, PhD, of Khon Kaen University in Thailand, lead author of the study. “Our goal is to find alternative drugs that can improve efficacy and potentially reduce toxicity, ultimately bringing new hope to patients facing this challenging disease.”

Testing cannabinoids in ovarian cancer models

In the study, researchers exposed two human ovarian cancer cell lines—A2780, which is sensitive to platinum-based chemotherapy, and SKOV3, which has intrinsic platinum resistance—to CBD, THC, or a combination of the two. A noncancerous ovarian epithelial cell line was also included to assess potential toxicity to healthy cells.

Both CBD and THC alone reduced the viability of ovarian cancer cells in a dose-dependent manner. However, the most pronounced effects were observed when the compounds were administered together. Cancer cells treated with the CBD–THC combination formed fewer and smaller colonies than those treated with either compound alone, indicating impaired long-term proliferative capacity.

“Notably, the inhibitory effect was most pronounced when CBD and THC were used in a 1:1 ratio,” Tong said.

Importantly, the combination demonstrated selective activity. While cancer cell growth was significantly suppressed, healthy ovarian epithelial cells were minimally affected, suggesting a potentially favorable therapeutic index.

Effects on migration, apoptosis, and cell signaling

Beyond inhibiting cell growth, the cannabinoid combination also reduced cancer cell migration and invasion in laboratory assays. These findings are clinically relevant, as metastatic spread is a major contributor to ovarian cancer mortality.

Further analyses showed that combined CBD and THC treatment increased apoptosis and induced cell cycle arrest in ovarian cancer cells. The investigators also observed changes in mitochondrial function and increased oxidative stress, both of which are known to contribute to programmed cancer cell death.

At the molecular level, the study focused on the PI3K/AKT/mTOR pathway, a signaling cascade commonly overactivated in ovarian cancer and associated with tumor growth, survival, and treatment resistance. Treatment with CBD and THC—particularly in combination—reduced phosphorylation of key components of this pathway while restoring activity of PTEN, a tumor suppressor protein that negatively regulates PI3K/AKT/mTOR signaling.

The authors suggest that this dual effect—suppressing oncogenic signaling while reactivating tumor suppressor mechanisms—may help explain the enhanced anti-cancer activity observed with the combination treatment.

Implications and limitations

Although the results are encouraging, the authors emphasized that the findings are preliminary and limited to in vitro experiments.

“Although our study is still preliminary, it lays an important foundation for future research into the potential applications of CBD and THC in ovarian cancer treatment,” Tong said. “By confirming their anti-cancer activity and identifying key molecular mechanisms, our findings are expected to drive further preclinical research. If future studies confirm these effects, CBD-THC combination therapy may ultimately contribute to the development of new treatment strategies.”

Tong also noted several important limitations. “All experiments were conducted in vitro, so the results may not fully reflect the complexity of tumor behavior in living organisms,” he said. “We did not include in vivo models and pharmacokinetic data, which are crucial for determining whether CBD/THC can be safely and effectively used clinically. Finally, regulatory and legal issues surrounding cannabinoid therapy may also affect future translational research. While the results are encouraging, more studies are needed before these findings can be applied to patient treatment.”

Looking ahead

For clinicians, these findings do not change current standards of care, but they add to a growing body of research examining cannabinoids as potential anti-cancer agents. Further studies in animal models and, eventually, clinical trials will be needed to determine whether these laboratory effects can translate into safe and effective therapies for patients with ovarian cancer.

References

1. Frontiers. Cannabis derivatives could provide new ovarian cancer treatments. Eurekalert. December 15, 2025. Accessed December 19, 2025.https://www.eurekalert.org/news-releases/1108503
2. Tong S, Loilome W, Namwat N, et al. Selective anti-cancer effects of cannabidiol and Δ9-tetrahydrocannabinol via PI3K/AKT/mTOR inhibition and PTEN restoration in ovarian cancer cells. Frontiers in Pharmacology. 2025;16. doi:https://doi.org/10.3389/fphar.2025.1693129