Opioid growth factor (OGF) inhibits the progression of human squamous cell carcinoma of the head and neck transplanted into nude mice

Opioid growth factor (OGF) interacts with the OGF receptor (OGFr) and serves as a native inhibitory growth factor. OGF and OGFr are present in squamous cell carcinoma of the head and neck (SCCHN), and OGF represses the replication of SCCHN in tissue culture. In this study, OGF-treated nude mice with xenografts of SCCHN displayed delays in tumor appearance and had reduced tumor size compared to controls. OGF activity was receptor-mediated. Opioid-receptor blockade by the potent opioid antagonist, naltrexone, stimulated tumorigenic processes. Both OGF and OGFr were detected in the tumors by immunohistochemistry, and OGFr was characterized by receptor binding analysis. These results indicate that the OGF–OGFr axis functions in vivo, OGF is a constitutively active molecule, and OGF modulation of SCCHN may have clinical application.