Related Experiment Videos
Transforming growth factor beta production and responsiveness in normal human melanocytes and melanoma cells
U Rodeck1, A Bossler, U Graeven
1Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104.
Abstract:
Previous studies have shown that some human melanoma cells express transforming growth factor beta (TGF-beta) mRNA and are growth inhibited by exogenous TGF-beta, suggesting a possible negative autocrine role for this melanoma-derived growth factor. To better understand the role of endogenous TGF-beta in the development of melanoma, we investigated patterns of TGF-beta protein production and responsiveness of human melanoma cells as compared to normal melanocytes. Both cultured melanoma cells and normal melanocytes secreted biologically inactive, latent TGF-beta protein which, upon acid treatment, became biologically active. In melanoma cells, TGF-beta production occurred constitutively, i.e., in the absence of exogenous polypeptide growth factors. By contrast, in melanocytes, TGF-beta production depended on stimulation by exogenous growth factors such as insulin-like growth factor I. Exogenous, bioactive TGF-beta 1 at picomolar concentrations inhibited tritiated thymidine uptake of normal melanocytes, whereas melanoma cells demonstrated various degrees of resistance to TGF-beta-induced inhibition of DNA synthesis. Five of six cell lines were less sensitive than any of the melanocyte lines tested, and one cell line was completely resistant to inhibitory effects of TGF-beta on DNA synthesis. In vivo selection of melanoma cells for metastatic ability in athymic mice produced a variant cell line that was resistant to TGF-beta 1-induced inhibition of DNA synthesis and proliferation. Development of TGF-beta resistance in the variant cell line was not associated with changes in TGF-beta cell surface binding. Stable transfection of melanocytes with a plasmid expressing the Simian Virus 40 large T-antigen rendered these cells resistant to growth inhibition by TGF-beta, suggesting that TGF-beta inhibits melanoma/melanocyte growth via interaction with Simian Virus 40 large T-antigen-responsive transcription elements.
Insights
Human melanoma cells can become resistant to transforming growth factor beta (TGF-beta), a key regulator of cell growth. This resistance may contribute to melanoma development and progression.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Human melanoma cells express TGF-beta mRNA and can be inhibited by exogenous TGF-beta, suggesting a negative autocrine role.
- Understanding endogenous TGF-beta's role in melanoma development requires comparing its production and responsiveness in melanoma cells versus normal melanocytes.
Purpose of the Study:
- To investigate TGF-beta protein production and responsiveness in human melanoma cells compared to normal melanocytes.
- To elucidate the role of endogenous TGF-beta in melanoma development.
Main Methods:
- Cultured melanoma cells and normal melanocytes were analyzed for TGF-beta protein secretion and biological activity.
- Cells were treated with acid to activate latent TGF-beta.
- DNA synthesis inhibition assays were performed using bioactive TGF-beta 1.
- Melanoma cells were selected in vivo for metastatic ability in athymic mice.
- Melanocytes were transfected with Simian Virus 40 large T-antigen.
Main Results:
- Both melanoma cells and melanocytes secreted latent TGF-beta, which became active upon acid treatment.
- Melanoma cells produced TGF-beta constitutively, while melanocytes required exogenous growth factors like IGF-I.
- Melanoma cells showed varying degrees of resistance to TGF-beta's inhibitory effects on DNA synthesis, with one cell line being completely resistant.
- A metastatic melanoma variant cell line developed resistance to TGF-beta 1 without changes in cell surface binding.
- Simian Virus 40 large T-antigen expression in melanocytes conferred resistance to TGF-beta growth inhibition.
Conclusions:
- Melanoma cells can develop resistance to TGF-beta, potentially impacting tumor progression.
- TGF-beta may inhibit melanoma/melanocyte growth through Simian Virus 40 large T-antigen-responsive transcription elements.