Marijuana's effect on Cancer and Lung Disease
Scientists are studying marijuana and THC in the treatment of various forms of cancer. They are also working to discover whether smoked marijuana causes cancer or obstructive pulmonary disease.
Brain cancer
A study by Complutense University of Madrid found the chemicals in marijuana promote death of brain cancer cells by helping them 'feed on themselves' in a process called autophagy. The research team discovered that cannabinoids such as THC had anticancer effects in mice with human brain cancer cells and in people with brain tumors. When mice implanted with the human brain cancer cells received THC the tumor shrank. Using electron microscopes to analyze brain tissue taken both before and after a 1 month THC course of treatment, the researchers found that THC eliminated cancer cells while leaving healthy cells intact. The patients did not have any toxic effects from the treatment; previous studies of THC for the treatment of cancer have also found the therapy to be well tolerated. The mechanisms of THC's tumor cell–killing action are unknown.
Lung cancer and chronic obstructive pulmonary disease
THC has been found to reduce tumor growth in common lung cancer by 50 percent. It also significantly reduced the ability of the cancer to spread, according to researchers at Harvard University, who tested the chemical in both lab and mouse studies. The researchers suggest that THC might be used in a targeted fashion to treat lung cancer.
A 2006 UCLA study found that smoking marijuana does not appear to increase the risk of lung cancer or head-and-neck malignancies, even among heavy users. The more tobacco a person smoked, the greater their risk of developing lung cancer and other cancers of the head and neck. But people who smoked more marijuana were not at increased risk compared with people who smoked less and people who didn’t smoke at all. Marijuana use was associated with cancer risk ratios below 1.0, indicating that a history of marijuana smoking had no effect on the risk for respiratory cancers. In contrast, tobacco smoking had a 21-fold risk for cancer. Donald Tashkin, the author, concluded, "It's possible that tetrahydrocannabinol (THC) in marijuana smoke may encourage apoptosis, or programmed cell death, causing cells to die off before they have a chance to undergo malignant transformation".
Wan Tan presented a study at the American Thoracic Society 2007 International Conference showing that smoking marijuana and tobacco together more than tripled the risk of developing Chronic obstructive pulmonary disease (COPD) over just smoking tobacco alone.
Similar findings were released in April 2009 by the Vancouver Burden of Obstructive Lung Disease Research Group. The study presents that smoking both tobacco and marijuana synergistically increased the risk of respiratory symptoms and COPD. Smoking only marijuana, however, was not associated with an increased risk of respiratory symptoms of COPD. In a related commentary, Tashkin writes, "…we can be close to concluding that marijuana smoking by itself does not lead to COPD".
Breast cancer
A 2007 study at the California Pacific Medical Center Research Institute found that cannabidiol (CBD) may stop breast cancer from spreading throughout the body. These researchers believe their discovery may provide a non-toxic alternative to chemotherapy while achieving the same results minus the painful and unpleasant side effects. The research team says that CBD works by blocking the activity of a gene called Id-1, which is believed to be responsible for a process called metastasis, which is the aggressive spread of cancer cells away from the original tumor site.
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