Pain associated with oral cancer is debilitating. Opioids are the gold standard for cancer pain management, but tolerance and side effects limit their use. Epidermal growth factor receptor (EGFR) signaling is commonly amplified in oral tumors. Here, we found that EGFR activation contributed to both oral cancer pain and opioid tolerance by sensitizing trigeminal ganglion (TG) cells, the main sensory neurons innervating the face and mouth. EGFR ligands were secreted by oral squamous cell carcinoma (OSCC) cells and by peripheral glial cells cocultured with OSCC cells. In human OSCC and an orthotopic mouse model, EGFR was abundant in tumor-innervating TG nerves. Oral cancer pain and opioid tolerance in the mice were increased by EGFR ligands and reduced by EGFR inhibitors. In mice, the abundance of glutamate-type NMDA receptors (NMDARs) was also increased in both the TG and the brainstem. Upon activation by ligands or OSCC cell supernatant, EGFR phosphorylated the NMDAR subunit GluN2B, which increased electrical currents and sensitized pre- and postsynaptic NMDARs in the brainstem. This sensitization was also seen in the brainstems of mice receiving chronic morphine treatment and was mitigated by EGFR blockade. These findings suggest that EGFR-targeted cancer therapeutics may be repurposed to manage cancer pain and reduce opioid tolerance in patients with OSCC.
Liu et al. (Tue,) studied this question.