TGF-β signaling regulates SPOP expression and promotes prostate cancer cell stemness

Area of Science:

• Oncology
• Molecular Biology
• Cancer Stem Cells

Background:

• SPOP (Speckle-type POZ protein) acts as a substrate adaptor for the E3 ubiquitin ligase Cullin3.
• SPOP mutations are common in prostate cancer (PCa).
• Transcriptional regulation of SPOP in PCa remains poorly understood.

Purpose of the Study:

• To investigate the transcriptional regulation of SPOP in PCa.
• To determine the role of TGF-β/SMAD signaling in SPOP expression in PCa stem-like cells (CSCs).
• To correlate SPOP expression levels with clinical outcomes in PCa patients.

Main Methods:

• Analysis of SPOP expression in PCa CSCs and tissues.
• Investigation of TGF-β/SMAD signaling pathway involvement using inhibitors (e.g., SB431542).
• Luciferase reporter assays to assess SMAD binding to the SPOP promoter.

Main Results:

• SPOP expression is significantly downregulated in PCa CSCs and tissues.
• TGF-β/SMAD signaling pathway represses SPOP expression in PCa CSCs.
• SMAD3 binds to SMAD-binding elements (SBEs) in the SPOP promoter.
• Inhibition of TGF-β signaling increases SPOP expression and reduces PCa stemness.
• Low SPOP expression in patients correlates with poor prognosis and reduced survival.

Conclusions:

• SPOP expression in PCa CSCs is transcriptionally repressed by the TGF-β/SMAD3 signaling axis.
• This repression contributes to PCa progression and poor clinical outcomes.
• Targeting the TGF-β/SMAD3 pathway may offer therapeutic strategies for PCa.