Human small cell lung cancer cells express high affinity naloxone-insensitive [125I]-endorphin binding sites.
Previous reports have demonstrated that beta-endorphin stimulates the clonal growth of human small cell lung carcinoma (SCLC) cell lines. In this study, the human SCLC lines, NCI-H69, NCI-H345, and NCI-N417, were observed to be highly-enriched in saturable, high-affinity binding sites which are labeled by [125I]beta-endorphin. In contrast to conventional opioid receptors, [125I]beta-endorphin SCLC binding was insensitive to naloxone and other mu, delta, or kappa opioid ligands. Further analysis of the NCI-H69 cells demonstrated that specific (naloxone-insensitive) binding was dependent on receptor concentration, reversible, sensitive to sodium ion, but insensitive to the GTP analogue, Gpp(NH)p. These results suggest a role for naloxone-insensitive beta-endorphin in modulating SCLC metabolism.
Biomeasure Inc., Milford, MA 01757.
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Taylor
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D018288:Carcinoma, Small Cell / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007457:Iodine Radioisotopes; D008175:Lung Neoplasms / Q000378:metabolism* / Q000648:ultrastructure; D009270:Naloxone / Q000378:metabolism / Q000494:pharmacology*; D016548:Prosencephalon / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured; D001615:beta-Endorphin / Q000378:metabolism*
D007457:Iodine Radioisotopes; D011957:Receptors, Opioid; D009270:Naloxone; D001615:beta-Endorphin