UCSD ( University of California San Diego ) researchers have identified the molecular mechanism activated by the presence of tetrahydrocannabinol ( THC ), the ingredient that causes people to feel the euphoria or high associated with Cannabis, in the bloodstream that accelerates cancer growth in patients with human papillomavirus ( HPV )-positive head and neck squamous cell carcinoma.
HPV-related head and neck cancer is one of the fastest growing cancers in the United States. While at the same time, exposure to marijuana is accelerating.
Head and neck squamous cell carcinoma is the sixth most common cancer worldwide.
These cancers begin in the cells that line the mucous membranes inside the mouth, nose and throat.
Approximately 30% of cases of this disease are related to HPV infection, and it is these cases, in particular that are on the rise.
Researchers have suggested increased marijuana use may be a driving factor.
Previous studies have linked daily marijuana exposure to an increased prevalence of HPV-related throat cancer. However, a mechanism linking Cannabis exposure to increased growth of the cancer was unknown.
Reporting in the Clinical Cancer Research, a journal of the American Association for Cancer Research ( AACR ), researchers outline how the presence of THC in the bloodstream activates the p38 MAPK pathway, which controls programed cell death called apoptosis. When activated, p38 MAPK prevents apoptosis from occurring, thus allowing cancer cells to grow uncontrollably.
Researchers used animal and human cell lines to show that THC turns p38 MAPK on and were able to stop the growth of HPV-positive head and neck cancer by turning off the pathway.
The team then analyzed blood samples from patients with HPV-related throat cancer who had their genomes comprehensively mapped to define activated gene pathways. Similar to the cell lines, the blood samples showed p38 MAPK activation and loss of apoptosis in tumors from patients with THC in their blood.
According to Authors, studies and public opinion suggestions that THC and other Cannabis products have cancer-fighting properties need additional, more critical evaluation.
Past studies showing anticancer effects of THC and other cannabinoids often used levels of THC higher than those found with recreational use, but doses used recreationally clearly activate a cancer-causing pathway.
Researchers have now convincing scientific evidence that daily marijuana use can drive tumor growth in HPV-related head and neck cancer.
Marijuana and other Cannabis products are often considered benign, but it is important to note that all drugs that have benefits can also have drawbacks.
According to the Centers for Disease Control and Prevention ( CDC ), HPV infections are responsible for approximately 35,000 new cancer diagnoses each year in the United States.
Infection is so common that nearly all men and women will get at least one type of HPV at some point in their lives. Most clear up on their own, without the person ever knowing they’ve had it.
Several vaccines are available that can prevent the majority of HPV-related cancers. The vaccines work best when they are given before a person is exposed to the virus.
The CDC recommends vaccinating boys and girls age 11 to 12 years old but it can be administered as early as age 9.
According to the National Institute on Drug Abuse, 15% of youth 12 to 17 years old and 47% of adults age 26 and older have used or tried marijuana.
Treatment options for patients with early- or late-stage head and neck cancers include minimally invasive surgery, reconstruction and rehabilitation, proton therapy and other radiation therapy, innovative clinical trials and targeted therapy, including immunotherapy. ( Xagena )
Source: University of California San Diego, 2020