SPOP promotes CDCA5 degradation to regulate prostate cancer progression via the AKT pathway

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Speckle-type POZ protein (SPOP) is a tumor suppressor in prostate cancer (PCa), with mutations found in up to 15% of cases.
• The precise mechanisms by which SPOP mutations contribute to prostate tumorigenesis are not fully understood.

Purpose of the Study:

• To identify and characterize novel substrates of SPOP involved in prostate cancer.
• To elucidate the role of SPOP-mediated regulation of its substrates in prostate cancer development and progression.

Main Methods:

• Protein-protein interaction assays to identify SPOP substrates.
• Ubiquitination assays to assess SPOP's effect on substrate degradation.
• Cell proliferation assays, cell cycle analysis, and apoptosis assays following gene silencing or overexpression.
• Western blotting to analyze protein expression levels and pathway activation.

Main Results:

• Cell division cycle associated 5 (CDCA5) was identified as a novel SPOP substrate, with SPOP promoting its degradation.
• Prostate cancer-associated SPOP mutations significantly impaired CDCA5 degradation.
• CDCA5 is essential for PCa cell survival and proliferation, and its depletion induces cell cycle arrest and apoptosis.
• CDCA5 overexpression or SPOP deficiency promotes PCa cell proliferation, while combined SPOP and CDCA5 depletion or overexpression represses growth.
• Elevated CDCA5 expression in PCa tissues correlates with advanced disease, lymph node metastasis, higher Gleason score, and poorer prognosis.

Conclusions:

• SPOP acts as a crucial inhibitor of prostate tumorigenesis by promoting the degradation of the oncoprotein CDCA5.
• Dysregulation of the SPOP-CDCA5 axis contributes to prostate cancer progression and suggests CDCA5 as a potential therapeutic target.