Related Experiment Videos
Phenotypic modification of human osteosarcoma cells with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate
T Ringbom-Anderson1, M Sandberg, G Andersson
1Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Abstract:
Treatment of the U-2 OS human osteosarcoma cell line with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) dramatically decreased the rate of DNA synthesis. This decrease in proliferation as well as the change in morphology of the TPA-treated cells can be blocked by the protein kinase C inhibitor GF 109203X. The U-2 OS cells are known to express the c-sis oncogene [platelet-derived growth factor (PDGF) B-chain], PDGF-A, and receptors for PDGF, thus providing a potential autocrine loop of growth stimulation. TPA was found to induce the expression of both the PDGF-A and the PDGF-B chains. However, the levels of the PDGF receptor beta subunits and of the PDGF-BB inducable tyrosine phosphorylation of the PDGF receptor were markedly reduced. The TPA treatment of the U-2 OS cells also induced changes typical for maturing bone cells, such as increased expression levels of alkaline phosphatase and osteopontin. The expression levels of type I collagen and bone sialoprotein were reduced. The results show a TPA-dependent down-regulation of the PDGF receptor beta subunits that correlates with an increased expression of osteoblast phenotypic markers.
Insights
Phorbol ester treatment of osteosarcoma cells inhibits DNA synthesis and alters cell morphology. This is linked to reduced platelet-derived growth factor (PDGF) receptor signaling and increased osteoblast markers.
Area of Science:
- Cell Biology
- Oncology
- Biochemistry
Background:
- U-2 OS human osteosarcoma cells express platelet-derived growth factor (PDGF) chains and receptors, suggesting autocrine growth stimulation.
- Phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is known to affect cell proliferation and differentiation.
Purpose of the Study:
- To investigate the effects of TPA on DNA synthesis, cell morphology, and gene expression in U-2 OS cells.
- To elucidate the role of protein kinase C and PDGF signaling in TPA-induced cellular changes.
Main Methods:
- Treatment of U-2 OS cells with TPA and the protein kinase C inhibitor GF 109203X.
- Assessment of DNA synthesis rates, cell morphology, and expression levels of PDGF chains, PDGF receptors, alkaline phosphatase, osteopontin, type I collagen, and bone sialoprotein.
Main Results:
- TPA significantly decreased DNA synthesis and altered cell morphology, effects blocked by GF 109203X.
- TPA induced PDGF-A and PDGF-B chain expression but markedly reduced PDGF receptor beta subunits and PDGF-BB-induced receptor phosphorylation.
- TPA treatment increased alkaline phosphatase and osteopontin expression while decreasing type I collagen and bone sialoprotein.
Conclusions:
- TPA induces osteosarcoma cell differentiation towards an osteoblast-like phenotype.
- Down-regulation of PDGF receptor beta subunits by TPA correlates with increased osteoblast markers in U-2 OS cells.