Presence and distribution of opioid growth factor, [Met⁵]-enkephalin and ζ-opioid receptor in head and neck squamous cell carcinoma

Approximately 45,000 new cases of squamous cell carcinoma of the upper aerodigestive tract occur each year in the U.S. Other than surgery, few advances in treatment modalities of these cancer have occurred. The endogenous opioid system, composed of the pentapeptide [Met⁵]-enkephalin termed opioid growth factor (OGF) and the ζ-opioid receptor, has been shown to be important in the growth of human and animal neoplasias. To examine the presence of OGF and the C-receptor in human head and neck squamous cell carcinomas, surgical specimens from the mouth, tonsil, larynx and neck metastasis were stained with anti-OGF or anti-ζ-opioid receptor and incubated with rhodamine-conjugated goat anti-rabbit IgG. Both anti-OGF and anti-ζ receptor stained sections demonstrated intense immunofluorescence associated with islands of squamous cell carcinoma but not with the underlying stroma. The cytoplasm of these cells was reactive, but the cell nuclei were unstained. Control specimens processed with pre-absorbed antibody did not exhibit any specific staining. These findings suggest that a potent negative growth regulator and its receptor are present in human head and neck squamous cell carcinomas.