Molecular Interplay between AURKA and SPOP Dictates CRPC Pathogenesis via Androgen Receptor

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• SPOP protein acts as a tumor suppressor in castration-resistant prostate cancer (CRPC) by degrading oncogenic targets like the androgen receptor (AR).
• SPOP is frequently mutated in CRPC, and its downregulation, not just mutation, is linked to poor prognosis, yet the mechanism remained unknown.
• Understanding SPOP regulation is crucial for developing targeted CRPC therapies.

Purpose of the Study:

• To elucidate the molecular mechanism regulating SPOP protein levels in CRPC.
• To identify upstream regulators of SPOP and their role in prostate cancer progression.
• To explore therapeutic strategies targeting SPOP regulation in CRPC.

Main Methods:

• Utilized innovative techniques to identify SPOP as a direct substrate of Aurora A kinase (AURKA).
• Investigated the phosphorylation and ubiquitylation of SPOP by AURKA.
• Assessed the in vivo and cellular effects of SPOP degradation on tumorigenesis, epithelial-mesenchymal transition (EMT), and drug sensitivity.

Main Results:

• AURKA directly phosphorylates SPOP at three specific sites, leading to its ubiquitylation and degradation.
• SPOP degradation stabilizes oncogenic proteins including AR, AR-V7, and c-Myc, driving aggressive phenotypes in vitro and in vivo.
• A negative feedback loop was identified where SPOP also degrades AURKA.
• Restoring SPOP function via phospho-resistant mutants abrogated tumorigenesis and EMT, sensitizing CRPC cells to enzalutamide.

Conclusions:

• AURKA-mediated phosphorylation and degradation of SPOP is a key mechanism driving CRPC progression.
• Targeting AURKA with inhibitors offers a therapeutic strategy to restore wild-type SPOP function in CRPC patients, potentially in combination with enzalutamide.
• This discovery provides a novel therapeutic avenue for a significant portion of CRPC cases by targeting SPOP regulation.