Interaction of opioid growth factor (OGF) and opioid antagonist and their significance in cancer therapy.

Endogenous opioids are neuro-peptides with multifunctional properties. Historically, opioids are used to mediate pain; however, excess opiate consumption can lead to addiction. One endogenous opioid, methionine enkephalin (MENK), was reported to modulate cell growth, MENK was identified as an opioid growth factor (OGF) that interacts with the OGF receptor (OGFr) and regulates cell proliferation. Further, opioid antagonists, including naltrexone and naloxone are widely used to reverse drug and alcohol overdoses. Naltrexone (NTX) acts on all opioid receptors, blocking the interaction between OGF and OGFr, and thus influencing cell growth. During the last decades, insights have been made concerning the interaction between OGF and OGFr, confirming that both opioids and opioid antagonists have an important role in balancing host homeostasis, host immunity and mediating cancer therapy. This review provides insight into the interactions between OGF and OGFr in the treatment of cancers.