The opioid growth factor (OGF) and low dose naltrexone (LDN) suppress human ovarian cancer progression in mice

ObjectiveThe opioid growth factor (OGF) and its receptor, OGFr, serve as a tonically active inhibitory axis regulating cell proliferation in normal cells and a variety of cancers, including human ovarian cancer. Blockade of OGF and OGFr with the nonselective opioid receptor antagonist naltrexone (NTX) upregulates expression of OGF and OGFr. Administration of a low dosage of NTX (LDN) blocks endogenous opioids from opioid receptors for a short period of time (4–6 h) each day, providing a window of 18–20 h for the upregulated opioids and receptors to interact. The present study investigated the repercussions of upregulating the OGF–OGFr axis by treatment with OGF or LDN on human ovarian tumorigenesis in vivo.MethodsFemale nude mice were transplanted intraperitoneally with SKOV-3 human ovarian cancer cells and treated on a daily basis with OGF (10 mg/kg), LDN (0.1 mg/kg), or an equivalent volume of vehicle (saline). Tumor burden, as well as DNA synthesis, apoptosis, and angiogenesis was assessed in tumor tissue following 40 days of treatment.ResultsOGF and LDN markedly reduced ovarian tumor burden (tumor nodule number and weight). The mechanism of action was targeted to an inhibition of tumor cell proliferation and angiogenesis; no changes in cell survival were noted.ConclusionsThis study shows that a native opioid pathway can suppress human ovarian cancer in a xenograft model, and provides novel non-toxic therapies for the treatment of this lethal neoplasia.

► The OGF–OGFr axis is a determinant of the progression of human ovarian cancer.
► Exogenous OGF inhibited tumorigenesis in mice with intraperitoneal xenografts.
► Low-dose naltrexone suppressed the expression of human ovarian cancer in mice.