Modulation of the opioid growth factor ([Met(5)]-enkephalin)-opioid growth factor receptor axis: novel therapies for squamous cell carcinoma of the head and neck.

Abstract

The opioid growth factor (OGF)-OGF receptor (OGFr) axis is a constitutively expressed biologic pathway regulating cell proliferation of squamous cell carcinoma of the head and neck (SCCHN). This study investigated modulation of the OGF-OGFr system by (1) exogenous OGF, (2) upregulation of OGFr using imiquimod, or (3) intermittent opioid receptor blockade with a low dose of naltrexone on progression of established SCCHN. Nude mice with visible human SCCHN SCC-1 tumors received (1) OGF or low-dose naltrexone either 1, 3, or 7 times/week or (2) imiquimod 1 or 3 times/week. Tumor growth and DNA synthesis were monitored. OGF and low-dose naltrexone increased the latency from visible to measurable tumors up to 1.6-fold. OGF, low-dose naltrexone, and imiquimod treatment markedly reduced tumor volume and weight, and decreased DNA synthesis in tumors. Modulation of the native OGF-OGFr regulatory network in SCCHN represents a novel nontoxic and highly efficacious approach for treatment of SCCHN.