Cell Density-Dependent Proliferative Effects of Transforming Growth Factor (TGF)-β1, β2, and β3 in Human Chondrosarcoma Cells HCS-2/8 Are Associated with Changes in the Expression of TGF-β Receptor Type I

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Abstract
In this study, the growth properties of the human chondrosarcoma cell line HCS- 2/8, its response to transforming growth factor (TGF)-β isoforms 1, 2, and 3, and its expression of TGF-β receptors I and II were examined. We demonstrated that these tumor cells are not contact-inhibited and that they can proliferate in the absence of additional serum growth factors. In sparse cultures, all TGF-β forms inhibited the growth of HCS-2/8 cells, whereas they induced a 2-fold increase of DNA synthesis in serum-fed confluent cultures. In serum-free confluent conditions only TGF-β1 stimulated the proliferation rate, whereas TGF-β2 was without effect and TGF-β3 was rather inhibitory. This bimodal effect of TGF-β forms was associated with a greater level of TGF-β receptor I mRNA in confluent HCS-2/8 than in sparse cultures, suggesting that the growth response to TGF-β forms is dependent on the receptor profile expressed.