Previous studies have suggested that cannabinoids, of which tetrahydrocannabinol (THC) is one, have anti-cancer properties. In 2009, researchers at Complutense University in Spain found that THC induced the death of brain cancer cells in a process known as "autophagy."
When human tumors in mice were targeted with doses of THC, the researchers found that two cell receptors were particularly associated with an anti-tumor response.
The researchers found that administering THC to mice with human tumors initiated autophagy and caused the growth of the tumors to decrease. Two human patients with highly aggressive brain tumors who received intracranial administration of THC also showed similar signs of autophagy, upon analysis.
The team behind the new study - co-led by Complutense University and the University of Anglia (UEA) in the UK - claims to have discovered previously unknown "signaling platforms" that allow THC to shrink tumors.
The researchers induced tumors in mice using samples of human breast cancer cells. When the tumors were targeted with doses of THC, the researchers found that two cell receptors were particularly associated with an anti-tumor response.
"THC, the major active component of marijuana, has anti-cancer properties. This compound is known to act through a specific family of cell receptors called cannabinoid receptors," says Dr. Peter McCormick, from UEA's School of Pharmacy.
"We show that these effects are mediated via the joint interaction of CB2 and GPR55 - two members of the cannabinoid receptor family. Our findings help explain some of the well-known but still poorly understood effects of THC at low and high doses on tumor growth."
However, the team is unsure which receptor is the most responsible for the anti-tumor effects.
Dr. McCormick says that there has been a "great deal of interest" in understanding the molecular mechanisms behind how marijuana influences cancer pathology. This has been accompanied by a drive in the pharmaceutical industry to synthesize a medical version of the drug that retains the anti-cancer properties.
"By identifying the receptors involved we have provided an important step towards the future development of therapeutics that can take advantage of the interactions we have discovered to reduce tumor growth," says Dr. McCormick.
Why patients should not 'self-medicate' with marijuana
Cancer patients should not be tempted to self-medicate, Dr. McCormick warns:
"Our research uses an isolated chemical compound and using the correct concentration is vital. Cancer patients should not use cannabis to self-medicate, but I hope that our research will lead to a safe synthetic equivalent being available in the future."
Medical marijuana has been in the news a lot over the past week, with Governor Andrew Cuomo signing the Compassionate Care Act, which makes New York the 23rd state to legalize the medical use of this drug.
Medical News Today also recently reported on how the city of Berkeley in California - which was the first state in the US to allow the medical use of marijuana, back in 1996 - has passed a law that requires the four marijuana dispensaries in the city to provide free medical marijuana to low-income patients who are prescribed this medication.
Meanwhile, Arizona have broadened the range of conditions for which medical marijuana can be prescribed as a treatment. As well as conditions such as cancer, chronic pain and muscle spasms, marijuana can now be prescribed as a form of palliative care for post-traumatic stress disorder.