OPRM1 and head and neck cancer: In an orthotopic xenograft model of head and neck cancer using Fadu HNSCCs, trigeminal ganglion neurons cultured from mice bearing tumors expressing MOR exhibited more robust sensitization (ectopic activity, low current thresholds, and more depolarized membrane potential) compared to neurons from mice that had tumors consisting of MOR knockout Fadu cells or those without tumors [14].