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Expression of transforming growth factor-beta (TGF-beta) receptors, TGF-beta 1 and TGF-beta 2 production and
P Kloen1, C L Jennings, M C Gebhardt
1Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
Abstract:
Transforming growth factor-beta (TGF-beta) is a polypeptide with multiple physiological functions. Isoforms of this growth factor have important roles in control of the cell cycle, in regulation of cell-cell interactions and in growth and development. Malignant transformation has been shown to be associated with increased expression of TGF-beta. Since bone is the largest storage site and producer of TGF-beta, we speculated on the existence of an autocrine mechanism in osteosarcoma, a malignant bone tumor. Expression of TGF-beta cell surface receptors, effects on growth of TGF-beta and TGF-beta antibodies and production of 2 TGF-beta isoforms were studied in a panel of 7 osteosarcoma cell lines. In contrast to most previous reports on the effects of TGF-beta on osteosarcoma cell growth, we found a mitogenic effect of TGF-beta 1 in 4 of 7 osteosarcoma cell lines. Receptor profiles for TGF-beta were aberrant in 5 of the 7 cell lines tested, and production of TGF-beta 1 and TGF-beta 2 varied among cell lines. Addition of anti-TGF-beta antagonized the effects of endogenous TGF-beta. Our results suggest a potential role of TGF-beta in autocrine growth control of osteosarcoma cells.
Insights
Transforming growth factor-beta (TGF-beta) promotes osteosarcoma cell growth in some cases, suggesting a potential autocrine mechanism. This finding highlights TGF-beta
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Transforming growth factor-beta (TGF-beta) is a crucial polypeptide regulating cell functions.
- Increased TGF-beta expression is linked to malignant transformation.
- Bone is a major reservoir and producer of TGF-beta.
Purpose of the Study:
- To investigate the autocrine mechanism of TGF-beta in osteosarcoma.
- To analyze TGF-beta receptor expression and its isoforms in osteosarcoma cell lines.
- To determine the effect of TGF-beta on osteosarcoma cell proliferation.
Main Methods:
- Studied TGF-beta receptor expression, cell growth effects, and TGF-beta isoform production in 7 osteosarcoma cell lines.
- Utilized TGF-beta and TGF-beta antibodies in experiments.
- Analyzed aberrant receptor profiles and variable TGF-beta production.
Main Results:
- TGF-beta 1 exhibited a mitogenic effect on 4 out of 7 osteosarcoma cell lines, contrary to previous reports.
- Aberrant TGF-beta receptor profiles were observed in 5 of the 7 cell lines.
- Production of TGF-beta 1 and TGF-beta 2 varied across the tested cell lines.
Conclusions:
- TGF-beta may play a role in the autocrine growth control of osteosarcoma cells.
- The study identified a mitogenic role for TGF-beta 1 in a subset of osteosarcoma cell lines.
- Aberrant receptor expression and variable TGF-beta production suggest complex autocrine signaling in osteosarcoma.