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Transforming growth factor-beta expression in mouse lung carcinogenesis
S B Jakowlew1, T W Moody, L You
1National Cancer Institute, Medicine Branch, Rockville, Maryland, USA.
Abstract:
Transforming growth factor-beta (TGF-beta) is a multifunctional growth modulator that inhibits the proliferation of many epithelial cells while stimulating the proliferation of most fibroblasts. To examine the role of TGF-beta in mouse lung chemically induced tumorigenesis, expression of the TGF-beta 1, -beta 2, and -beta 3 proteins was examined in A/J mice treated with the carcinogen urethane to induce lung adenomas using immunohistochemical staining analysis. Immunostaining for the TGF-beta ligands was detected in the epithelium of the bronchioles of untreated A/J mice with immunostaining being more intense for TGF-beta 1 than for TGF-beta 2 and TGF-beta 3; immunostaining for each TGF-beta ligand was also detected in the bronchiolar epithelium of urethane-treated A/J mice at levels similar to untreated mice. Immunostaining for the TGF-beta ligands was also detected in adenomas by 2 months; staining for TGF-beta 1, -beta 2, and -beta 3 in adenomas was detected at levels comparable with bronchioles. Following treatment with urethane for 8 months, immunostaining for TGF-beta s 1, 2, and 3 in bronchioles persisted at levels comparable to that in normal bronchioles and also persisted in adenomas, with staining for the TGF-beta ligands being very prominent on the edge of the tumor. Expression of TGF-beta 1 mRNA was examined in urethane-treated mouse lung tissue using Northern blot hybridization; here, expression of TGF-beta 1 mRNA increased 2-fold in 3-month urethane-treated lung tissue and an additional 2.5-fold by 8 months following urethane administration. Expression of TGF-beta 1 mRNA was also examined in nontumorigenic and tumorigenic mouse lung cells; in these cells, expression of TGF-beta 1 mRNA was higher in the tumorigenic cells than in the nontumorigenic cell line. These data show that there is an increase in expression of TGF-beta 1 during tumorigenesis and suggest that TGF-beta may play an important role in mouse lung carcinogenesis induced by urethane.
Insights
Transforming growth factor-beta (TGF-beta) expression increased during urethane-induced lung tumorigenesis in mice. This suggests TGF-beta plays a key role in the development of lung cancer.
Area of Science:
- Oncology
- Molecular Biology
- Carcinogenesis
Background:
- Transforming growth factor-beta (TGF-beta) is a key regulator of cell proliferation and tissue remodeling.
- TGF-beta exhibits diverse effects, inhibiting epithelial cell proliferation while stimulating fibroblast proliferation.
Purpose of the Study:
- To investigate the role of TGF-beta 1, -beta 2, and -beta 3 in chemically induced lung tumorigenesis in A/J mice.
- To analyze TGF-beta expression patterns during urethane-induced lung adenoma development.
Main Methods:
- Immunohistochemical staining was used to detect TGF-beta protein expression in lung tissues of A/J mice.
- Northern blot hybridization was employed to examine TGF-beta 1 mRNA levels in lung tissue and cell lines.
Main Results:
- TGF-beta ligands were detected in the bronchiolar epithelium of both untreated and urethane-treated mice.
- TGF-beta protein expression was present in developing lung adenomas, particularly at tumor edges.
- TGF-beta 1 mRNA expression significantly increased in lung tissue over time after urethane administration and was higher in tumorigenic lung cells.
Conclusions:
- TGF-beta expression is altered during urethane-induced lung tumorigenesis.
- The findings suggest a significant role for TGF-beta in the progression of mouse lung cancer.