Characterization of the [125I]endomorphin-2 binding sites in the MCF7 breast cancer cell line.
In the present study, the expression of the micro-opioid receptor on protein level has been demonstrated in MCF7 breast cancer cells. Binding of the [125I]-labeled micro-opioid receptor selective ligand endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) was examined in vitro using a cross-linking assay followed by a Western blot technique. The radioactive complex had a molecular weight of about 65 kDa and was detectable by anti-micro-opioid receptor antibody, indicating the presence of micro-opioid receptors in MCF7 cell membranes. Characterization of endomorphin-2 binding to the membranes obtained from MCF7 cells was performed. Cold saturation experiments with [125I]endomorphin-2 showed biphasic binding curves in Scatchard coordinates. One component represents a high affinity and low capacity, and the other low affinity and higher capacity binding sites. The obtained Bmax values for [125I]endomorphin-2 binding to MCF7 membranes were much higher than those obtained for mouse brain. Pharmacological characterization of the [125I]endomorphin-2 binding sites was made using endomorphin-2 and two other micro selective ligands, morphiceptin, and [D-1-Nal3]morphiceptin on MCF7 cell membrane preparations and whole MCF7 cells. In both cases, the rank order of potency was [D-1-Nal3]morphiceptin>endomorphin-2>morphiceptin, but in case of whole MCF7 cells the IC50 values were about 40 times higher.
Fichna
Jakub
J
Department of Medicinal Chemistry, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland.
Krajewska
Urszula
U
Rozalski
Marek
M
Mirowski
Marek
M
Janecka
Anna
A
D000701:Analgesics, Opioid / Q000378:metabolism*; D001345:Autoradiography; D001665:Binding Sites; D001667:Binding, Competitive; D015153:Blotting, Western; D002277:Carcinoma / Q000378:metabolism; D045744:Cell Line, Tumor; D004723:Endorphins / Q000378:metabolism*; D005260:Female; D006801:Humans; D020128:Inhibitory Concentration 50; D007457:Iodine Radioisotopes; D007700:Kinetics; D008024:Ligands; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism*; D011485:Protein Binding; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000378:metabolism*
D000701:Analgesics, Opioid; D004723:Endorphins; D007457:Iodine Radioisotopes; D008024:Ligands; D009842:Oligopeptides; D017450:Receptors, Opioid, mu; C105294:endomorphin 2