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High affinity receptors for bombesin/GRP-like peptides on human small cell lung cancer
Abstract:
The binding of a radiolabeled bombesin analogue to human small cell lung cancer (SCLC) cell lines was investigated. (125I-Tyr4)bombesin bound with high affinity (Kd = 0.5 nM) to a single class of sites (2,000/cell) using SCLC line NCI-H446. Binding was reversible, saturable and specific. The pharmacology of binding was investigated using NCI-H466 and SCLC line NCI-H345. Bombesin and structurally related peptides, such as gastrin releasing peptide (GRP), but not other peptides, such as substance P or vasopressin, inhibited high affinity (125I-Tyr4)BN binding activity. Finally, the putative receptor, a 78,000 dalton polypeptide, was identified by purifying radiolabeled cell lysates on bombesin or GRP affinity resins and then displaying the bound polypeptides on sodium dodecylsulfate polyacrylamide gels. Because SCLC both produces bombesin/GRP-like peptides and contains high affinity receptors for these peptides, they may function as important autocrine regulatory factors for human SCLC.
Insights
Researchers investigated radiolabeled bombesin analogue binding to small cell lung cancer (SCLC) cells. High-affinity binding sites were identified, suggesting bombesin/GRP peptides may regulate SCLC growth.
Area of Science:
- Oncology
- Molecular Biology
- Endocrinology
Background:
- Small cell lung cancer (SCLC) is an aggressive form of lung cancer.
- Autocrine growth factors may play a role in SCLC regulation.
- Bombesin-like peptides and their receptors are implicated in various cancers.
Purpose of the Study:
- To investigate the binding characteristics of a radiolabeled bombesin analogue to human SCLC cell lines.
- To characterize the bombesin receptor on SCLC cells.
- To explore the potential role of bombesin/GRP peptides as autocrine factors in SCLC.
Main Methods:
- Radioligand binding assays using (125I-Tyr4)bombesin on SCLC cell lines (NCI-H446, NCI-H345).
- Pharmacological characterization of binding using various peptides (bombesin, GRP, substance P, vasopressin).
- Identification of the putative receptor via affinity chromatography and SDS-PAGE.
Main Results:
- High-affinity binding (Kd = 0.5 nM) of (125I-Tyr4)bombesin to a single class of sites (2,000/cell) on NCI-H446 cells.
- Binding was specific, saturable, and reversible.
- Bombesin and GRP inhibited binding, while other peptides did not.
- A 78,000 dalton polypeptide was identified as the putative bombesin receptor.
Conclusions:
- Human SCLC cells express high-affinity bombesin receptors.
- Bombesin/GRP peptides may act as autocrine growth factors for SCLC.
- These findings support the potential for targeting the bombesin receptor pathway in SCLC therapy.