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Demonstration of receptors for a PDGF-like mitogen on human osteosarcoma cells
Abstract:
U-2 OS human osteosarcoma cells synthesize, process and secrete a platelet-derived growth factor (PDGF)-like mitogen. Incubation of these cells with 1 mM suramin unmasks PDGF receptor sites which are normally occupied or down regulated by the secreted endogenous PDGF-like mitogen. Partially purified preparations of metabolically labelled U-2 OS conditioned medium binds to U-2 OS cells and binding is inhibited by excess PDGF. These findings suggest that U-2 OS cells are capable of autocrine stimulation.
Insights
Human osteosarcoma cells (U-2 OS) secrete a platelet-derived growth factor (PDGF)-like molecule, suggesting autocrine stimulation. Suramin treatment unmasks PDGF receptors on these cells.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- U-2 OS human osteosarcoma cells are known to secrete growth factors.
- Platelet-derived growth factor (PDGF) plays a crucial role in cell proliferation and survival.
- Autocrine signaling, where cells respond to their own secreted factors, is a key mechanism in cancer progression.
Purpose of the Study:
- To investigate the autocrine signaling capabilities of U-2 OS cells.
- To identify and characterize the PDGF-like mitogen secreted by U-2 OS cells.
- To explore the regulation of PDGF receptors in U-2 OS cells.
Main Methods:
- Metabolic labeling of U-2 OS cells to identify secreted proteins.
- Partial purification of conditioned medium from U-2 OS cells.
- Binding assays to assess the interaction of secreted factors with PDGF receptors on U-2 OS cells.
- Treatment with suramin to unmask PDGF receptor sites.
Main Results:
- U-2 OS cells synthesize, process, and secrete a PDGF-like mitogen.
- Incubation with suramin unmasks previously occupied or downregulated PDGF receptor sites.
- Partially purified conditioned medium from U-2 OS cells binds to U-2 OS cells.
- This binding is inhibited by excess PDGF, confirming the presence of a PDGF-like substance.
Conclusions:
- U-2 OS cells exhibit autocrine stimulation through the secretion of a PDGF-like mitogen.
- Endogenous PDGF-like mitogen normally occupies or downregulates PDGF receptors on U-2 OS cells.
- These findings highlight a potential mechanism for sustained proliferation in osteosarcoma.