CHARACTERIZATION OF METHADONE RECEPTOR SUBTYPES PRESENT IN HUMAN BRAIN AND LUNG TISSUES

In addition to their use in pain control, opioids can function as regu lators of tumor cell growth. We have found that the therapeutic opioid , methadone, significantly inhibits the in vitro and in vivo growth of human lung cancer cells, and this effect appears to be mediated by sp ecific, high affinity, non-conventional opioid binding sites. The pres ent study indicates the existence of multiple subtypes of binding site s mediating the peripheral and central nervous system actions of this drug. Pharmacological and biochemical characterizations of the methado ne binding sites expressed in human brain and normal lung tissues indi cate that these sites are distinct from each other and from other opio id receptor types present on human and rat brain membranes, as well as those expressed in human lung cancer cells. The identification of dis tinct methadone receptor types in the different tissues could lead to the development of more selective and less toxic drugs targeted toward the tumor cells. (C) 1997 Elsevier Science Inc.