A study published today in Medical Oncology found that cannabidiol (CBD) significantly reduced several measures of tumor growth and aggressiveness in laboratory models of chemotherapy-resistant head and neck cancer, including a 98% reduction in cancer cell colony formation.
The study, conducted by researchers at the Federal University of São João del Rei in Brazil, examined CBD’s effects on head and neck squamous cell carcinoma, particularly human papillomavirus (HPV)-negative cancer cells resistant to cisplatin, a commonly used chemotherapy drug.
Researchers tested CBD on human cancer cell lines, three-dimensional tumor models and a chick embryo membrane model. CBD reduced cancer cell viability in a concentration-dependent manner, with a stronger cytotoxic effect on the cancer cells than on the noncancerous fibroblasts and keratinocytes tested.
One of the most pronounced findings involved the cancer cells’ ability to form new colonies. Treatment with CBD at a concentration of 10 micromolar reduced colony formation by 98% compared with untreated controls, suggesting substantial interference with the cells’ capacity to survive and reproduce.
CBD also significantly inhibited cancer cell migration and invasion, two processes associated with tumor progression. After 72 hours, CBD-treated cultures retained approximately 66% of the original gap in a cell migration experiment, while untreated cells had nearly closed the gap entirely.
The researchers also documented a 77% reduction in the activity of matrix metalloproteinase-9 (MMP-9) and a 45% reduction in MMP-2. These enzymes help break down surrounding tissue and are associated with cancer cell invasion. CBD additionally suppressed growth in three-dimensional tumor spheroids.
In experiments using chick embryo membranes, CBD significantly reduced tumor size and the blood vessel area surrounding tumors without causing measurable vascular irritation.
Another finding involved CBD’s interaction with cisplatin. When researchers tested the compounds in combination, they observed synergistic cytotoxic effects, meaning the combined treatment produced greater effects than expected from their individual activity. The strongest interaction occurred with 10 micromolar CBD and 5 micromolar cisplatin.
Molecular analysis indicated that CBD influenced pathways associated with programmed cell death, autophagy and cell-cycle regulation. The treatment increased markers associated with apoptosis while reducing cyclin D1, a protein involved in cell proliferation.
The authors concluded that their findings support further investigation of CBD as a potential addition to existing treatments for chemotherapy-resistant head and neck cancer, particularly its ability to interfere with tumor-associated processes and enhance cisplatin’s cytotoxic effects.
