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.

Background: 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.

Methods: 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.