An endogenous pentapeptide with potential antineoplastic and antiangiogenic activities. Opioid growth factor (OGF) binds to and activates the opioid growth factor receptor (OGFr), present on some tumor cells and vascular cells, thereby inhibiting tumor cell proliferation and angiogenesis. or An abbreviation for a chemotherapy combination that is often used with radiation therapy to treat a certain type of childhood Hodgkin lymphoma in females. It includes the drugs vincristine sulfate (Oncovin), prednisone, procarbazine hydrochloride, and doxorubicin hydrochloride (Adriamycin). Also called OPPA.