Targeting GRP78-dependent AR-V7 protein degradation overcomes castration-resistance in prostate cancer therapy.

Abstract

Rationale: Androgen receptor splice variant 7 (AR-V7) is a leading cause of the development of castration-resistant prostate cancer (CRPC). However, the regulation and function of AR-V7 at levels of post-translational modifications in prostate cancer therapy remain poorly understood. Here, we conducted a library screen of natural products to identify potential small molecules responsible for AR-V7 protein degradation in human prostate cancer cell lines. Methods: A natural product library was used to screen the inhibitor of AR-V7. Co-IP and biomass spectrum assays were used to identify the AR-V7-interacting proteins, whereas western blot, confocal microscopy, RNA interfering, and gene transfection were used to validate these interactions. Cell viability, EDU staining, and colony formation assays were employed to detect cell growth and proliferation. Flowcytometry assays were used to detect the distribution of cell cycle. Mouse xenograft models were used to study the anti-CRPC effects in vivo. Results: This screen identified rutaecarpine, one of the major components of the Chinese medicine Evodia rutaecarpa, as a novel chemical that selectively induces AR-V7 protein degradation via K48-linked ubiquitination. Mechanically, this effect relies on rutaecarpine inducing the formation of a GRP78-AR-V7 protein complex, which further recruits the E3 ligase SIAH2 to directly promote the ubiquitination of AR-V7. Consequently, the genetic and pharmacological activation of the GRP78-dependent AR-V7 protein degradation restores the sensitivity of castration-resistant prostate cancer to anti-androgen therapy in cell culture and animal models. Conclusions: These findings not only provide a new approach for overcoming castration-resistance in prostate cancer therapy, but also increase our understanding about the interplay between molecular chaperones and ubiquitin ligase in shaping protein stability.

• Authors: Yuning Liao, Yuan Liu, Xiaohong Xia, Zhenlong Shao, Chuyi Huang, Jinchan He, Lili Jiang, Daolin Tang, Jinbao Liu, Hongbiao Huang
• Journal: Theranostics (Theranostics) Vol. 10 Issue 8 Pg. 3366-3381 ( 2020) ISSN: 1838-7640 [Electronic] Australia
• PMID: 32206096 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The author(s).

Chemical References

• Alkaloids
• Androgen Receptor Antagonists
• Antineoplastic Agents, Phytogenic
• Endoplasmic Reticulum Chaperone BiP
• HSPA5 protein, human
• Heat-Shock Proteins
• Hspa5 protein, mouse
• Nuclear Proteins
• Protein Isoforms
• Receptors, Androgen
• rutacarpine
• Ubiquitin-Protein Ligases
• seven in absentia proteins

Topics

• Alkaloids (therapeutic use)
• Androgen Receptor Antagonists (therapeutic use)
• Animals
• Antineoplastic Agents, Phytogenic (therapeutic use)
• Castration
• Cell Line, Tumor
• Endoplasmic Reticulum Chaperone BiP
• HEK293 Cells
• Heat-Shock Proteins (antagonists & inhibitors)
• Humans
• Male
• Mice
• Mice, Inbred BALB C
• Nuclear Proteins (metabolism)
• Prostatic Neoplasms, Castration-Resistant (drug therapy)
• Protein Isoforms (antagonists & inhibitors, genetics, metabolism)
• Proteolysis
• Receptors, Androgen (genetics, metabolism)
• Ubiquitin-Protein Ligases (metabolism)
• Ubiquitination
• Xenograft Model Antitumor Assays