Interestingly, a study on a murine model of cancer pain assessed synthetic CB1R and CB2R agonists individually and in combination and concluded that binding of any CB receptor is associated with pain alleviation comparable to that of morphine and the co-administration of the two agonists has synergistical effects (Khasabova et al., 2011), which is why several different natural and synthetic CB1R and CB2R agonists have been investigated in this setting. This evidence concerns the gene CNR1 and cancer.