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Transforming growth factor-beta inhibits surfactant protein A expression in vitro
J A Whitsett1, A Budden, W M Hull
1Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, OH.
Abstract:
Effects of members of the transforming growth factor-beta (TGF-beta) family on expression of surfactant protein A (SP-A) were determined in human pulmonary adenocarcinoma cells. TGF-beta decreased SP-A content in two distinct pulmonary adenocarcinoma cell lines with bronchiolar (NCI-H441-4) and alveolar (NCI-H820) cell characteristics. TGF-beta 1, beta 2 and beta 3 were equally effective in decreasing SP-A. Effects of the TGF-beta's on SP-A content were dose dependent, EC50 approximately 20-30 pg/ml for each form of TGF-beta. TGF-beta decreased cellular SP-A content in association with decreased levels of SP-A mRNA. Inhibitory effects of TGF-beta 1 on SP-A mRNA was time dependent, reaching maximal effects within 12-24 h, after which SP-A mRNA was approximately 10% of that present in untreated cells. Maximal inhibition of SP-A mRNA was observed at 250 pg/ml TGF-beta 1. TGF-beta-dependent inhibition of SP-A expression was not associated with altered cell morphology, growth, or viability. TGF-beta family members act directly on pulmonary adenocarcinoma cells to inhibit SP-A expression by mechanisms which are mediated, at least in part, at a pretranslational level.
Insights
Transforming growth factor-beta (TGF-beta) inhibits surfactant protein A (SP-A) production in lung cancer cells. This inhibition occurs at the pretranslational level, affecting SP-A mRNA without altering cell viability.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Molecular Biology
Background:
- Surfactant protein A (SP-A) is crucial for lung function.
- Pulmonary adenocarcinomas are a common type of lung cancer.
- The role of TGF-beta in lung adenocarcinoma SP-A expression is not fully understood.
Purpose of the Study:
- To investigate the effects of transforming growth factor-beta (TGF-beta) family members on surfactant protein A (SP-A) expression in human pulmonary adenocarcinoma cells.
- To determine the mechanism of TGF-beta's influence on SP-A production.
Main Methods:
- Treatment of human pulmonary adenocarcinoma cell lines (NCI-H441-4 and NCI-H820) with varying concentrations of TGF-beta 1, beta 2, and beta 3.
- Quantification of SP-A content and SP-A mRNA levels.
- Assessment of cell morphology, growth, and viability.
Main Results:
- All TGF-beta isoforms (1, 2, 3) significantly decreased SP-A content in a dose-dependent manner (EC50 ~20-30 pg/ml).
- TGF-beta reduced SP-A mRNA levels, with maximal inhibition (~90%) observed after 12-24 hours at 250 pg/ml TGF-beta 1.
- Inhibition of SP-A expression was not linked to changes in cell morphology, growth, or viability.
Conclusions:
- Members of the TGF-beta family directly inhibit SP-A expression in pulmonary adenocarcinoma cells.
- The inhibitory mechanism is mediated, at least in part, at the pretranslational level, affecting SP-A mRNA.
- TGF-beta's effects on SP-A expression are independent of significant alterations in cell growth or viability.