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Smad7 mediates apoptosis induced by transforming growth factor beta in prostatic carcinoma cells
M Landström1, N E Heldin, S Bu
1Biomedical Centre, Rudbeck Laboratory, Ludwig Institute for Cancer Research, Uppsala University, Uppsala, Sweden. Marene.Landstrom@LICR. uu.se
Abstract:
Transforming growth factor beta (TGF-beta) is an important regulator of apoptosis in some cell types, but the underlying molecular mechanisms are largely unknown. TGF-beta signals through type I and type II receptors and downstream effector proteins, termed Smads. TGF-beta induces the phosphorylation of Smad2 and Smad3 (receptor-activated Smads) which associate with Smad4 and translocate to the nucleus, where they regulate gene transcription [1]. Smad7 protein is induced by TGF-beta1 and has been classified as an inhibitory Smad. Smad7 prevents phosphorylation of receptor-activated Smads, thereby inhibiting TGF-beta-induced signaling responses [1]. Smad7 expression is increased in rat prostatic epithelial cells undergoing apoptosis as a result of castration [2]. Here we have shown that TGF-beta1 treatment or ectopic expression of Smad7 in human prostatic carcinoma cells (PC-3U) induces apoptosis. Furthermore, TGF-beta1-induced apoptosis was prevented by inhibition of Smad7 expression, by antisense mRNA in stably transfected cell lines or upon transient transfection with antisense oligonucleotides in several investigated cell lines. These findings provide evidence for a new effector function for Smad7 in TGF-beta1 signaling.
Insights
Transforming growth factor beta 1 (TGF-beta1) induces apoptosis in prostate cancer cells. Smad7 protein mediates this effect, revealing a new role for Smad7 in TGF-beta1 signaling pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Transforming growth factor beta (TGF-beta) regulates apoptosis, but its mechanisms are unclear.
- Smad proteins are key mediators of TGF-beta signaling.
- Smad7 is an inhibitory Smad, and its expression increases during apoptosis in rat prostate cells.
Purpose of the Study:
- To investigate the role of Smad7 in TGF-beta1-induced apoptosis in human prostatic carcinoma cells.
- To elucidate the molecular mechanisms underlying TGF-beta1's apoptotic effects.
Main Methods:
- Treatment of human prostatic carcinoma cells (PC-3U) with TGF-beta1.
- Ectopic expression of Smad7.
- Inhibition of Smad7 expression using antisense mRNA and oligonucleotides.
Main Results:
- TGF-beta1 treatment and Smad7 overexpression induced apoptosis in PC-3U cells.
- Inhibiting Smad7 expression blocked TGF-beta1-induced apoptosis.
- These findings were consistent across multiple cell lines.
Conclusions:
- Smad7 plays a critical role in mediating TGF-beta1-induced apoptosis.
- Smad7 has a novel effector function in TGF-beta1 signaling pathways.
- Targeting Smad7 could be a therapeutic strategy for prostate cancer.