Atinuke S Ajiboye1, David Esopi2, Srinivasan Yegnasubramanian1,2, Samuel R Denmeade1,2. 1. Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland. 2. Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, Maryland.
Abstract
BACKGROUND: Androgen receptor (AR) splice variants have been clinically associated with progressive cancer, castration-resistance, and resistance to AR antagonists and androgen synthesis inhibitors. AR variants can be generated by genomic alterations and alternative splicing, and their expression is androgen-regulated. There has been a suggestion that AR variants bearing premature termination codons and coding for truncated proteins should be regulated by the nonsense-mediated decay (NMD) mRNA surveillance pathway, suggesting that either the NMD pathway is dysfunctional in variant-expressing cell lines or that variants are somehow able to evade degradation by NMD. METHODS: We first used siRNA knockdown of the NMD regulator, UPF1, in an NMD reporter assay to determine if this surveillance pathway is functioning normally in AR variant-expressing cell lines. We then used UPF1 knockdown to determine if expression of the AR variants ARV3 and ARV7 is affected by inhibition of NMD. Next, we analyzed androgen regulation of UPF1 and used transcript expression analysis to determine if there is any association between UPF1 expression, resistance, and ARV3 or ARV7 expression. RESULTS: We found that the NMD pathway functions normally in the AR variant-expressing cell line 22Rv1 and that inhibition of NMD does not increase expression of ARV3 or ARV7. Furthermore, we found that expression of UPF1 is not androgen-regulated. We also found that UFP1 expression levels do not differentiate castration-sensitive from resistant cell line and that UPF1 expression does not correlate with expression of ARV3 or ARV7 in cells in which these variants are highly expressed. CONCLUSION: This study eliminates a possible mechanism of regulation of certain AR variants. Future research into the regulation of AR variants should focus on other mechanisms to better understand the origin of these variants and to possibly inhibit their expression for the resensitization of resistant cancers. Prostate 77:829-837, 2017.
BACKGROUND:Androgen receptor (AR) splice variants have been clinically associated with progressive cancer, castration-resistance, and resistance to AR antagonists and androgen synthesis inhibitors. AR variants can be generated by genomic alterations and alternative splicing, and their expression is androgen-regulated. There has been a suggestion that AR variants bearing premature termination codons and coding for truncated proteins should be regulated by the nonsense-mediated decay (NMD) mRNA surveillance pathway, suggesting that either the NMD pathway is dysfunctional in variant-expressing cell lines or that variants are somehow able to evade degradation by NMD. METHODS: We first used siRNA knockdown of the NMD regulator, UPF1, in an NMD reporter assay to determine if this surveillance pathway is functioning normally in AR variant-expressing cell lines. We then used UPF1 knockdown to determine if expression of the AR variants ARV3 and ARV7 is affected by inhibition of NMD. Next, we analyzed androgen regulation of UPF1 and used transcript expression analysis to determine if there is any association between UPF1 expression, resistance, and ARV3 or ARV7 expression. RESULTS: We found that the NMD pathway functions normally in the AR variant-expressing cell line 22Rv1 and that inhibition of NMD does not increase expression of ARV3 or ARV7. Furthermore, we found that expression of UPF1 is not androgen-regulated. We also found that UFP1 expression levels do not differentiate castration-sensitive from resistant cell line and that UPF1 expression does not correlate with expression of ARV3 or ARV7 in cells in which these variants are highly expressed. CONCLUSION: This study eliminates a possible mechanism of regulation of certain AR variants. Future research into the regulation of AR variants should focus on other mechanisms to better understand the origin of these variants and to possibly inhibit their expression for the resensitization of resistant cancers. Prostate 77:829-837, 2017.
Authors: R Thermann; G Neu-Yilik; A Deters; U Frede; K Wehr; C Hagemeier; M W Hentze; A E Kulozik Journal: EMBO J Date: 1998-06-15 Impact factor: 11.598
Authors: Ana Luísa Silva; Francisco J C Pereira; Ana Morgado; Jian Kong; Rute Martins; Paula Faustino; Stephen A Liebhaber; Luísa Romão Journal: RNA Date: 2006-10-31 Impact factor: 4.942
Authors: Tomasz M Beer; Andrew J Armstrong; Dana E Rathkopf; Yohann Loriot; Cora N Sternberg; Celestia S Higano; Peter Iversen; Suman Bhattacharya; Joan Carles; Simon Chowdhury; Ian D Davis; Johann S de Bono; Christopher P Evans; Karim Fizazi; Anthony M Joshua; Choung-Soo Kim; Go Kimura; Paul Mainwaring; Harry Mansbach; Kurt Miller; Sarah B Noonberg; Frank Perabo; De Phung; Fred Saad; Howard I Scher; Mary-Ellen Taplin; Peter M Venner; Bertrand Tombal Journal: N Engl J Med Date: 2014-06-01 Impact factor: 91.245
Authors: Emma Hörnberg; Erik Bovinder Ylitalo; Sead Crnalic; Henrik Antti; Pär Stattin; Anders Widmark; Anders Bergh; Pernilla Wikström Journal: PLoS One Date: 2011-04-28 Impact factor: 3.240
Authors: Kasper Daniel Hansen; Liana F Lareau; Marco Blanchette; Richard E Green; Qi Meng; Jan Rehwinkel; Fabian L Gallusser; Elisa Izaurralde; Donald C Rio; Sandrine Dudoit; Steven E Brenner Journal: PLoS Genet Date: 2009-06-19 Impact factor: 5.917
Authors: Yezi Zhu; Susan L Dalrymple; Ilsa Coleman; S Lilly Zheng; Jianfeng Xu; Jody E Hooper; Emmanuel S Antonarakis; Angelo M De Marzo; Alan K Meeker; Peter S Nelson; William B Isaacs; Samuel R Denmeade; Jun Luo; W Nathaniel Brennen; John T Isaacs Journal: Oncogene Date: 2020-09-28 Impact factor: 9.867