br Ningning Liua Zhiqiang Guob
Ningning Liua,1, Zhiqiang Guob,c,1, Xiaohong Xiab, Yuning Liaob, Fangcheng Zhanga, Chuyi Huangb, Yuan Liub, Xiumei Dengd, Lili Jiangb, Xuejun Wange, Jinbao Liub, , Hongbiao Huangb,
a Guangzhou Institute of Cardiovascular Disease, Guangdong Key Laboratory of Vascular Diseases, State Key Laboratory of Respiratory Disease, the Second Aﬃliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510260, China
b Key Laboratory of Protein Modification and Degradation, State Key Laboratory of Respiratory Disease, School of Basic Medical Sciences; Aﬃliated Cancer Hospital and institute of Guangzhou Medical University, Guangzhou, Guangdong 511436, China
c The Sixth Aﬃliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital, Qingyuan, Guangdong 511500, China
d Nanshan School of Guangzhou Medical University, Grade 2015, Guangzhou, Guangdong 510260, China
e Division of Basic Biomedical Sciences, University of South Dakota Sanford School of Medicine, Vermillion, SD 57069, USA
Auranofin (Aur) inhibits thioredoxin reductases and is also an inhibitor of 19S proteasome associated deubi-quitinases, targeting USP14 and UCHL5. Androgen receptor is often over-expressed in prostate cancer (PCa) and is strongly linked to PCa growth and progression. Consequently, androgen deprivation therapy (ADT) that re-duces androgen has been applied to treat androgen receptor-mediated PCa for decades. Nevertheless, most ADT treated patients experience relapse due to the development of the castration-resistant PCa. Numerous studies have shown that down-regulation of cellular androgen receptor level, including inhibiting its transcription and promoting its protein degradation, is lethal to PCa cells. Here we report that Aur arrested GW9662 progression and induced apoptosis of PCa cells. Co-inhibition of USP14 and UCHL5 with Aur facilitated the ubiquitination and degradation of androgen receptors in LNcap and 22RV1 PCa cells. Our results also show that Aur decreases the mRNA level of androgen receptors. In conclusion, our findings suggest that Aur is a promising agent for clinical translation to treat PCa.
In 2018, approximately 164,690 men were aﬀected by prostate cancer (PCa) in the United States (Siegel et al., 2018). The incidence of PCa is approximately 1 in 6 males (Prensner et al., 2012). Recent epi-demiological data rank PCa as the second leading cause of cancer-re-lated mortality among American men despite the five-year survival rate approaching 100% (Hoang et al., 2017; Van Neste et al., 2012). An-drogen deprivation therapy (ADT) which reduces androgens has been considered as a standard therapeutic modality for patients with ad-vanced PCa since 1941 (Huggins and Hodges, 2002). Nevertheless, ADT-treated patients eventually develop castration-resistant PCa (CRPC) (Joensuu et al., 2016; Suzuki et al., 2010). Surprisingly, new researches claim that the survival rates for patients receiving flutamide
and goserelin are 78% and for those receiving LTAD are 84% (Gravis et al., 2016; Lawton et al., 2017; Van Hemelryk et al., 2016). Flutamide and goserelin inhibit hormone eﬀect or production by competitively binding to receptors. Molecular targeting has become the main therapy approach for cancer due to advancement in the molecular biology of cancer. Studies have shown that androgen receptor signaling is closely-linked to PCa (Heinlein and Chang, 2004) and that targeting androgen receptors confers a remarkable therapeutic avenue. Androgen receptor is critical to survival and growth of PCa cells; thus, down-regulating the androgen receptor level is crucial for PCa treatment.
Protein degradation in the cell is mainly performed by the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway. In the UPS, proteins labeled by a chain of ubiquitin are recognized and then degraded by the 26 S proteasome consisting of a 19S regulatory particle
Corresponding authors at: Key Laboratory of Protein Modification and Degradation, State Key Laboratory of Respiratory Disease, School of Basic Medical Sciences; Aﬃliated Cancer Hospital and institute of Guangzhou Medical University, Guangzhou, Guangdong 511436, China.
E-mail addresses: [email protected] (J. Liu), [email protected] (H. Huang).
1 Equal contribution.
and a 20S proteasome. Nevertheless, deubiquitinating enzymes (DUBs) can reverse target protein degradation by removing ubiquitin/ubi-quitin-like chains. DUBs function to regulate multiple cellular pro-cesses, including DNA damage responses, cell cycle control, and many signaling pathways (Aressy et al., 2010; Song and Rape, 2008). Ap-proximately 100 putative DUBs are encoded in human genome and classified into six families based on their catalytic and structural fea-tures (Hussain et al., 2009). Among these enzymes, three diﬀerent DUBs (i.e., USP14, UCHL5 and Rpn11) are present in the 19S regulatory particle in mammalian cells. Rpn11 is a metalloprotease and an ob-ligatory subunit of the 19 S proteasome complexes (Brnjic et al., 2014; D'Arcy and Linder, 2012; Wang et al., 2015; Weissman et al., 2011). USP14 and UCHL5 are cysteine proteases involved in deubiquitination at the proteasome, and belonging to the USP and the UCH families, respectively. USP14 and UCHL5 are overexpressed in various carci-noma cells, providing a potential therapeutic target (Mialki et al., 2013). Several small molecule inhibitors have been developed to target USP14 and UCHL5; some of them have been used in preclinical tests (D'Arcy and Linder, 2014).