Zagon et al. tested 31 cases of human tumor cell lines and found that 90% of the tumor cells had a high expression of the OGFR, and 42% of cell proliferation was decreased after OGF was added into the culture dish, but 44% was accelerated after naltrexone (opioid receptor antagonist) was added (73), which indicates that application of morphine in the treatment of pains for patients with tumors is safe. This evidence concerns the gene OGFR and neoplasm.