The Role of Opioid Receptors in Cancer

Opioids are one of the most potent drugs for treating moderate to severe pain. Despite irrefutable clinical application in chronic pain management, the long-term use of opioids has been increasingly questioned due to undesired side effects that demand attention. Opioids such as morphine mediate clinically relevant effects primarily through the mu-opioid receptor that go beyond their classical role as analgesics, causing potentially fatal side effects such as tolerance, dependence, and addiction. Furthermore, there is growing evidence that opioids affect immune system function, cancer progression, metastasis, and recurrence. Though a biological plausibility, the clinical evidence for the action of opioids on cancer is mixed, revealing a more complex picture as researchers struggle to establish a vital link between opioid receptor agonists, cancer progression, and suppression, or both. Thus, in light of the uncertainty of opioid effects on cancer, in this review, a focused overview of the role of opioid receptors in modulating cancer progression, their underlying signaling mechanisms, and the biological activity of opioid receptor agonists and antagonists is provided.

Automated summary

Opioids are powerful drugs used for moderate to severe pain, but their long-term use can lead to unwanted side effects. There is evidence to suggest that opioids may affect immune system function, cancer progression, metastasis, and recurrence. This review provides an overview of the role of opioid receptors in modulating cancer progression, their signaling mechanisms, and the biological activity of opioid receptor agonists and antagonists.