Smoking cannabis could raise cancer risk

SMOKING cannabis may suppress the immune system and increase the risk of cancer, new research has suggested.

Scientists believe the drug triggers the production of cells that weaken the body's resistance to cancer.

A US study found cannabinoids - the active compounds in cannabis - activated biological pathways to generate "massive numbers" of the cells, known as myeloid-derived suppressor cells (MDSCs). These are special immune cells that act as a safety brake on the immune system.

They suppress immune responses to prevent them getting out of control, but in so doing are thought to promote cancer growth.

Lead researcher Dr Prakash Nagarkatti, from the University of South Carolina, said: "These results raise interesting questions on whether increased susceptibility to certain types of cancers or infections caused from smoking marijuana results from induction of MDSCs.

"MDSCs seem to be unique and important cells that may be triggered by inappropriate production of certain growth factors by cancer cells or other chemical agents such as cannabinoids, which lead to a suppression of the immune system's response."

Another study, led by Dr Christian Vosshenrich, from the Pasteur Institute in Paris, showed that when cancer cells grow, they produce a signalling molecule called interleukin-1 beta. This also triggered MDSC production, reducing the body's ability to defend itself against cancer.

Dr Nagarkatti said: "Marijuana cannabinoids present us with a double-edged sword. On one hand, due to their immunosuppressive nature, they can cause increased susceptibility to cancer and infections. However, further research of these compounds could provide opportunities to treat a large number of clinical disorders where suppressing the immune response is actually beneficial."

A drug derived from cannabis has been shown to relieve symptoms of multiple sclerosis and rheumatoid arthritis, both diseases caused by an overactive immune response.