TRAF4 Inhibits Bladder Cancer Progression by Promoting BMP/SMAD Signaling
Prasanna Vasudevan Iyengar1,2, Dieuwke Louise Marvin1,2, Dilraj Lama3,4
1Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands.
Abstract:
Patients with bladder cancer often have a poor prognosis due to the highly invasive and metastatic characteristics of bladder cancer cells. Epithelial-to-mesenchymal transition (EMT) has been causally linked to bladder cancer invasion. The E3 ubiquitin ligase, tumor necrosis factor receptor-associated factor 4 (TRAF4) has been implicated as a tumor promoter in a wide range of cancers. In contrast, here we show that low TRAF4 expression is associated with poor overall survival in patients with bladder cancer. We show that the TRAF4 gene is epigenetically silenced and that ERK mediates TRAF4 phosphorylation, resulting in lower TRAF4 protein levels in bladder cancer cells. In addition, we demonstrate that TRAF4 is inversely correlated with an EMT gene signature/protein marker expression. Functionally, by manipulating TRAF4 expression, we show that TRAF4 regulates EMT genes and epithelial and invasive properties in bladder cancer cells. Transcriptomic analysis of dysregulated TRAF4 expression in bladder cancer cell lines revealed that high TRAF4 expression enhances the bone morphogenetic protein (BMP)/SMAD and inhibits the NF-κB signaling pathway. Mechanistically, we show that TRAF4 targets the E3 ubiquitin ligase SMURF1, a negative regulator of BMP/SMAD signaling, for proteasomal degradation in bladder cancer cells. This was corroborated in patient samples where TRAF4 positively correlates with phospho-SMAD1/5, and negatively correlates with phospho-NFκb-p65. Lastly, we show that genetic and pharmacologic inhibition of SMURF1 inhibits the migration of aggressive mesenchymal bladder cancer cells.
Implications:
Our findings identify E3 ubiquitin ligase TRAF4 as a potential therapeutic target or biomarker for bladder cancer progression.
Insights
Low expression of tumor necrosis factor receptor-associated factor 4 (TRAF4) correlates with poor bladder cancer survival. TRAF4 regulates cell invasion by modulating epithelial-to-mesenchymal transition (EMT) and signaling pathways, offering a potential therapeutic target.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Genetics
Background:
- Bladder cancer is characterized by high invasiveness and metastatic potential, often leading to poor patient prognosis.
- Epithelial-to-mesenchymal transition (EMT) is a key driver of bladder cancer invasion and metastasis.
- The E3 ubiquitin ligase tumor necrosis factor receptor-associated factor 4 (TRAF4) is implicated as a tumor promoter in various cancers.
Purpose of the Study:
- To investigate the role of TRAF4 in bladder cancer progression and its association with patient survival.
- To elucidate the mechanisms by which TRAF4 influences bladder cancer cell invasion and metastasis.
Main Methods:
- Analysis of TRAF4 expression in bladder cancer patients and cell lines.
- Investigation of TRAF4 epigenetic regulation and post-translational modification (e.g., phosphorylation by ERK).
- Functional studies manipulating TRAF4 expression to assess its impact on EMT markers, cell invasion, and signaling pathways (BMP/SMAD, NF-κB).
- Assessment of TRAF4's interaction with SMURF1 and its effect on proteasomal degradation.
Main Results:
- Low TRAF4 expression is significantly associated with poor overall survival in bladder cancer patients.
- TRAF4 expression is epigenetically silenced and reduced by ERK-mediated phosphorylation in bladder cancer cells.
- TRAF4 expression is inversely correlated with EMT markers and invasiveness; TRAF4 suppresses EMT and invasion.
- High TRAF4 expression enhances BMP/SMAD signaling and inhibits NF-κB signaling, partly via targeting SMURF1 for degradation.
- TRAF4 positively correlates with phospho-SMAD1/5 and negatively with phospho-NFκb-p65 in patient samples.
Conclusions:
- TRAF4 acts as a tumor suppressor in bladder cancer, contrary to its role in other cancers.
- TRAF4 regulates bladder cancer cell invasion and metastasis by modulating EMT and key signaling pathways.
- TRAF4 is identified as a potential therapeutic target or predictive biomarker for bladder cancer progression.
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