Impact of opioids and mu-opioid receptors on oncologic metastasis

Abstract

Opioids are the most effective and widely used treatments for acute and chronic pain in patients with cancer. This review focuses on the impact of opioids and mu-opioid receptors (MORs) on the stages of oncologic metastasis. Studies have shown that opioids can facilitate tumor progression and are related to a poor prognosis in patients with cancer. As the primary receptor for opioids, MORs play a significant role in regulating malignant tumor transformation and are involved in processes, such as proliferation, angiogenesis, epithelial-mesenchymal transition (EMT), circulating tumor cells (CTCs) and the tumor microenvironment (TME). While clinical trials have investigated the relationship between opioids and patient prognosis, further research is needed to clarify the relationship between opioids, MORs and metastasis.

Keywords: Opioids; cancer; metastasis; mu-opioid receptor.

Figure 1

Phases of metastasis. Initially, tumor cells undergo genetic mutations that enable them to detach from the primary site. Subsequently, these cells invade surrounding tissues, aided by enzymes that degrade the extracellular matrix. As they migrate, these cells may undergo epithelial to mesenchymal transition and enter blood or lymphatic vessels, as circulating tumor cells. Eventually, they exit the vessels at distant sites, adhere to new tissue, and proliferate, forming secondary tumors. This process is facilitated by interactions with the host immune system and the tumor microenvironment.