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Expression and autoregulation of transforming growth factor beta receptor mRNA in small-cell lung cancer cell lines
P Nørgaard1, M Spang-Thomsen, H S Poulsen
1Section for Radiation Biology, Finsen Center, Rigshospitalet, Copenhagen, Denmark.
Abstract:
In small-cell lung cancer cell lines resistance to growth inhibition by transforming growth factor (TGF)-beta 1, was previously shown to correlate with lack of TGF-beta receptor I (RI) and II (RII) proteins. To further investigate the role of these receptors, the expression of mRNA for RI, RII and beta-glycan (RIII) was examined. The results showed that loss of RII mRNA correlated with TGF-beta 1 resistance. In contrast, RI-and beta-glycan mRNA was expressed by all cell lines, including those lacking expression of these proteins. According to Southern blot analysis, the loss of type II mRNA was not due to gross structural changes in the gene. The effect of TGF-beta 1 on expression of TGF-beta receptor mRNA (receptor autoregulation) was examined by quantitative Northern blotting in four cell lines with different expression of TGF-beta receptor proteins. In two cell lines expressing all three TGF-beta receptor proteins beta-glycan mRNA was rapidly down-regulated and this effect was sustained throughout the 24 h observation period. RI and RII mRNAs were slightly increased 24 h after treatment. In one cell line sensitive to growth inhibition by TGF-beta, 1 but lacking beta-glycan expression, and one cell line expressing only beta-glycan and thus TGF-beta 1 -resistant, no autoregulation of mRNA of either TGF-beta receptor was demonstrated. The results suggest that TGF-beta 1 regulates the expression of its receptors, in particular beta-glycan, and that this effect is dependent on co-expression of beta-glycan, RI and RII.
Insights
Transforming growth factor-beta 1 (TGF-β1) resistance in lung cancer cells links to TGF-β receptor II (RII) mRNA loss. TGF-β1 regulates its own receptor expression, particularly beta-glycan, dependent on co-expressed receptors.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Signaling
Background:
- Resistance to transforming growth factor-beta 1 (TGF-β1) growth inhibition in small-cell lung cancer (SCLC) correlates with absent TGF-β receptor I (RI) and II (RII) proteins.
- Understanding the role of TGF-β receptors is crucial for SCLC treatment strategies.
Purpose of the Study:
- To investigate the expression of messenger RNA (mRNA) for TGF-β receptors (RI, RII, and beta-glycan/RIII) in SCLC cell lines.
- To examine the autoregulation of TGF-β receptor mRNA expression by TGF-β1.
Main Methods:
- Quantitative Northern blotting was used to analyze mRNA expression levels.
- Southern blot analysis was performed to assess gene structure.
- SCLC cell lines with varying TGF-β receptor expression were utilized.
Main Results:
- Loss of TGF-β receptor II (RII) mRNA correlated with resistance to TGF-β1.
- RI and beta-glycan mRNA were expressed in all cell lines, irrespective of protein expression.
- TGF-β1 treatment down-regulated beta-glycan mRNA in cell lines expressing all three receptors, while RI and RII mRNA showed a slight increase.
- Autoregulation of TGF-β receptor mRNA was not observed in cell lines lacking beta-glycan or expressing only beta-glycan.
Conclusions:
- TGF-β1 actively regulates its receptor expression, with beta-glycan being particularly sensitive.
- This TGF-β1-mediated receptor regulation is contingent upon the co-expression of beta-glycan, RI, and RII.