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Regulation by IGF-I and TGF-beta1 of Swarm-rat chondrosarcoma chondrocytes
T Matsumura1, M C Whelan, X Q Li
1Department of Orthopaedic Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, USA.
Abstract:
The growth factors transforming growth factor-beta 1 and insulin-like growth factor-I influence a wide range of cellular actions, including the growth of several neoplastic cell types. Their role in the regulation of neoplastic chondrocytes remains unclear. We tested the hypotheses that transforming growth factor-beta 1 and insulin-like growth factor-I differentially regulate neoplastic chondrocytes and interact to modulate the mitotic and matrix synthetic activities of neoplastic chondrocytes. We used Swarm-rat chondrosarcoma chondrocytes to investigate the effect of each factor individually and of both factors in combination on [(3)H]thymidine incorporation into DNA and on [(35)S]sulfate incorporation into glycosaminoglycans. Each factor increased [(3)H]thymidine incorporation 2.7-fold: transforming growth factor-beta 1 achieved this effect at a 20-fold lower concentration than insulin-like growth factor-I. In contrast, insulin-like growth factor-I stimulated [(35)S]sulfate incorporation 3.5-fold; this was twice the maximal effect of transforming growth factor-beta 1. Transforming growth factor-beta 1 and insulin-like growth factor-I each decreased the proportion of newly synthesized glycosaminoglycans that were retained in the cells and pericellular matrix, indicating that the anabolic effect of these factors is only partly directed toward cell-associated matrix production. The mitogenic and matrix synthetic actions of insulin-like growth factor-I and transforming growth factor-beta 1 were synergistic. In concert, they increased [(3)H]thymidine incorporation approximately 12-fold, an effect three times greater than the sum of the maximal stimulation achieved by each factor individually. Similarly, transforming growth factor-beta 1 and insulin-like growth factor-I together increased glycosaminoglycan synthesis approximately two times more than the sum of their maximal individual effects. Taken together, these data indicate that these chondrosarcoma chondrocytes are positively regulated by insulin-like growth factor-I and transforming growth factor-beta 1 and that these growth factors interact to augment the mitotic and matrix synthetic actions of the chondrocytes. If supported in human models, the sensitivity to growth factors of these cells suggests that interventions directed toward growth factor inhibition may be of therapeutic value.
Insights
Transforming growth factor-beta 1 and insulin-like growth factor-I promote neoplastic chondrocyte growth and matrix production. These growth factors synergistically enhance cell proliferation and glycosaminoglycan synthesis, suggesting potential therapeutic targets.
Area of Science:
- Cell Biology
- Biochemistry
- Oncology
Background:
- Growth factors, specifically transforming growth factor-beta 1 (TGF-β1) and insulin-like growth factor-I (IGF-I), are known to influence various cellular processes, including the proliferation of neoplastic cells.
- However, their specific roles in regulating neoplastic chondrocytes and their potential interactions remain largely uncharacterized.
Purpose of the Study:
- To investigate the differential effects of TGF-β1 and IGF-I on neoplastic chondrocytes.
- To determine if TGF-β1 and IGF-I interact to modulate the mitotic and matrix synthetic activities of these cells.
Main Methods:
- Utilized Swarm-rat chondrosarcoma chondrocytes to assess the impact of individual and combined TGF-β1 and IGF-I.
- Measured [(3)H]thymidine incorporation to evaluate DNA synthesis (mitotic activity).
- Measured [(35)S]sulfate incorporation to assess glycosaminoglycan synthesis (matrix production).
Main Results:
- Both TGF-β1 and IGF-I individually stimulated DNA synthesis, with TGF-β1 being effective at a lower concentration.
- IGF-I demonstrated a greater stimulation of glycosaminoglycan synthesis compared to TGF-β1.
- The combination of TGF-β1 and IGF-I exhibited synergistic effects, significantly amplifying both DNA and glycosaminoglycan synthesis beyond the additive effects of each factor alone.
- Both factors reduced the retention of newly synthesized glycosaminoglycans, indicating partial direction towards cell-associated matrix production.
Conclusions:
- Neoplastic chondrocytes are positively regulated by both TGF-β1 and IGF-I.
- These growth factors interact synergistically to enhance chondrocyte proliferation and matrix synthesis.
- The sensitivity of these cells to growth factors suggests that targeting growth factor pathways could be a potential therapeutic strategy for chondrosarcoma.