Cannabinoids activate a major cancer-causing pathway, p38 MAPK, in patients with human papillomavirus-positive head and neck cancers, according to a study published in Clinical Cancer Research in January. When turned on, the pathway prevents apoptosis, which allows increased growth and invasion of cancer cells, the researchers reported.
“I am cautioning patients with HPV-related head and neck cancers to not use cannabis products, whether smoked, ingested, or vaped, as the data show a consistent effect in laboratory, animal models, and in actual patients who use marijuana,” said senior author of the study Joseph Califano III, MD, director of the Head and Neck Cancer Center, and physician-in-chief at the Moores Cancer Center at UC San Diego Health.
Dr. Califano and colleagues used data from The Cancer Genome Atlas to analyze expression of cannabinoid receptors in patients with head and neck cancer and found that the cannabinoid receptors CNR1 and CNR2 were elevated in HPV-positive patients compared to HPV-negative patients. Using animal and human cell lines, they found that specific CNR1 and CNR2 activation promoted cell growth and migration and inhibited apoptosis through activation of the p38 MAPK pathway.
Further analysis of blood samples from a cohort of patients with HPV-related head and neck cancers in whom activated gene pathways were available through comprehensive genomic mapping showed p38 MAPK activation in tumors in patients with cannabinoids in their blood.
“We now have convincing scientific evidence that daily marijuana use can drive tumor growth in HPV-related head and neck cancer,” Dr. Califano said in a press release.
Given the dramatic increase in marijuana use, with legalization in many states, and persistent widespread HPV infection, Dr. Califano emphasized the potential escalation of HPV-related head and neck cancers, particularly among men, given the persistent low HPV vaccination rates among boys.
—Mary Beth Nierengarten