An “orphan receptor” is the term for a receptor in the body whose natural activator is not known. GPR55 is a G-protein coupled orphan receptor that interacts with the other cannabinoid system. CBD appears to inhibit GPR55, while endocannabinoids may activate it. Researchers in the UK and Italy collaborated on a study of GPR55 in pancreatic cancer. Activating GPR55 increased the proliferation and metastasis of cancer cells, while inhibiting GPR55 with CBD or another molecule slowed tumor progression. Mice treated with CBD and the chemo gemcitabine survived nearly three times longer than the mice that didn’t receive CBD. Since CBD affects many different proteins, it’s hard to be sure that GPR55 is the main reason for CBD’s protective activity. The scientists emphasize that CBD and gemcitabine — which are both approved for use in humans — should be tested in clinical trials. Previous research has shown that activating GPR55 stimulates the immune system, opposing the anti-inflammatory immuno-modulating effect of the CB2 cannabinoid receptor.