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Biological effects and binding properties of transforming growth factor-beta on human oral squamous cell carcinoma
H Ichijo1, F Momose, K Miyazono
1First Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Tokyo Medical and Dental University, Japan.
Abstract:
The effects of transforming growth factor-beta (TGF-beta) on three human oral squamous cell carcinoma cell lines, HSC-2, HSC-3, and HSC-4, were investigated. Although these cell lines were equally sensitive to epidermal growth factor, responses to TGF-beta were variable. Dose-dependent inhibition of cell growth and [3H]thymidine incorporation of HSC-4 were observed by the addition of TGF-beta, whereas growth inhibitory effects on HSC-2 and HSC-3 were marginal. Moreover, treatment of HSC-4 with TGF-beta led to a more than 300-fold increase in fibronectin secretion into the medium. In contrast, TGF-beta did not increase the secretion of fibronectin on HSC-2 and HSC-3. Scatchard analysis of the binding of TGF-beta suggested that all squamous cell carcinoma cell lines have similar binding properties, with two classes of binding sites for TGF-beta. Affinity labeling of 125I-TGF-beta to cell surface receptors revealed the two major affinity crosslinked bands with Mr values of 65 kDa (type I) and 280 kDa (type III). A concomitant loss of 85 kDa band (type II) was observed in all squamous carcinoma cell lines examined. Although the proportions of type I and type III receptors were variable, the type I receptor, which is reported to be the main functional receptor in mediating the TGF-beta action, was commonly observed in these squamous cell carcinoma cell lines. These results indicate that the heterogeneity in response to TGF-beta between cell lines may be due to the difference in the signal transduction pathway of TGF-beta.
Insights
Transforming growth factor-beta (TGF-beta) shows variable effects on oral cancer cells. Differences in TGF-beta signal transduction pathways may explain the heterogeneous responses observed in these cell lines.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Oral squamous cell carcinoma (OSCC) is a significant global health concern.
- Transforming growth factor-beta (TGF-beta) is a key regulator of cell growth, differentiation, and extracellular matrix production.
- Understanding the differential effects of TGF-beta on OSCC cell lines is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the differential effects of TGF-beta on human oral squamous cell carcinoma cell lines (HSC-2, HSC-3, HSC-4).
- To analyze the expression and binding characteristics of TGF-beta receptors on these cell lines.
- To explore the potential mechanisms underlying the heterogeneous responses to TGF-beta.
Main Methods:
- Cell culture of three human OSCC cell lines (HSC-2, HSC-3, HSC-4).
- Treatment with varying doses of TGF-beta to assess cell growth and [3H]thymidine incorporation.
- Measurement of fibronectin secretion using ELISA.
- Scatchard analysis for TGF-beta binding site characterization.
- Affinity labeling to identify cell surface TGF-beta receptors.
Main Results:
- TGF-beta dose-dependently inhibited the growth and proliferation of HSC-4 cells, with marginal effects on HSC-2 and HSC-3.
- TGF-beta significantly increased fibronectin secretion in HSC-4 cells but not in HSC-2 and HSC-3.
- All cell lines exhibited similar TGF-beta binding properties with two classes of binding sites.
- Type I (65 kDa) and Type III (280 kDa) TGF-beta receptors were detected, with a loss of Type II (85 kDa) receptor.
- Type I receptor, crucial for TGF-beta signaling, was present in all cell lines, though proportions varied.
Conclusions:
- Oral squamous cell carcinoma cell lines exhibit heterogeneous responses to TGF-beta.
- Variability in TGF-beta-induced growth inhibition and fibronectin secretion suggests differential signaling.
- The presence of Type I and Type III receptors, along with the absence of Type II, indicates complex TGF-beta receptor dynamics.
- Differences in TGF-beta signal transduction pathways are likely responsible for the observed heterogeneity in cellular responses.