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Generation 2.5 Antisense Oligonucleotides Targeting the Androgen Receptor and its Splice Variants Suppress Enzalutamide-Resistant Prostate Cancer Cell Growth

ABSTRACT: Enzalutamide (ENZ) is a potent androgen receptor (AR) antagonist with activity in castration-resistant prostate cancer (CRPC); however, progression to ENZ-resistant (ENZ-R) CRPC frequently occurs with rising serum PSA levels, implicating AR full length (ARFL) or variants (AR-Vs) in disease progression. To define functional roles of ARFL and AR-Vs in ENZ-R CRPC, we designed 3 antisense oligonucleotides (ASO) targeting exon 1, intron 1, and exon 8 in AR pre-mRNA to knockdown either ARFL alone, or ARFL plus AR-Vs, and examined their respective effects in LNCaP-derived ENZ-R, as well as M12 and 22Rv1, cells. ENZ-R LNCaP xenografts express high levels of both ARFL and AR-V7 compared to CRPC LNCaP xenografts. In particular, ARFL levels were ~20-fold higher than AR-V7. ENZ-R LNCaP sub-lines, derived by selection from the ENZ xenografts, also expressed uniformly high levels of ARFL and AR-V7 compared to CRPC LNCaP cells. In addition, both ARFL and AR-V7 are highly expressed in the nuclear fractions of ENZ-R-LNCaP. In ENZ-R LNCaP cells, knockdown of ARFL alone, or ARFL plus AR-Vs, similarly induced apoptosis, suppressed cell growth and AR-regulated gene expression in vitro, and delayed tumour growth in vivo. In 22Rv1 cells that are inherently resistant to ENZ, knockdown of both ARFL and AR-Vs more potently suppressed cell growth, AR transcriptional activity and AR-regulated gene expression than knockdown of ARFL alone. These data indicate the AR is an important driver of ENZ resistance, and while the contributions of ARFL and AR-Vs can vary across cell systems, ARFL is the key driver in the ENZ-R LNCaP model. AR targeting strategies against both ARFL and AR-Vs is a rational approach for AR-dependent CRPC. CRPC and ENZ-R LNCaP xenografts were generated as described in: Gleave, M.E., et al., Serum prostate specific antigen levels in mice bearing human prostate LNCaP tumors are determined by tumor volume and endocrine and growth factors. Cancer Res, 1992. 52(6): p. 1598-605.

ORGANISM(S): Homo sapiens

PROVIDER: GSE55345 | GEO | 2015/01/01

SECONDARY ACCESSION(S): PRJNA239365

REPOSITORIES: GEO

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Project description:Continued androgen receptor (AR) signaling is an established mechanism underlying castration-resistant prostate cancer (CRPC), and suppression of AR signaling remains a therapeutic goal of CRPC therapy. Constitutively active androgen receptor splicing variants (AR-Vs) lack the AR ligand-binding domain (AR-LBD), the intended target of androgen deprivation therapies (ADT) including new CRPC therapies such as abiraterone and MDV3100. While the canonical full-length AR (AR-FL) and AR-Vs are both increased in CRPC, their expression regulation, associated transcriptional programs, functional relationships, and respective roles in mediating responses to endocrine therapies have not been dissected. In this study, we show that suppression of canonical AR-FL signaling by targeting AR-LBD leads to increased AR-V expression in two cell line models of CRPC. Importantly, treatment-induced AR-Vs activate a distinct expression signature enriched for cell cycle genes without requiring the presence of AR-FL. Conversely, activation of AR-FL signaling suppresses the AR-V signature but activates expression programs mainly associated with macromolecular synthesis, metabolism, and differentiation. In prostate cancer cells and CRPC xenografts treated with MDV3100 and abiraterone, increased expression of two constitutively active AR-Vs, AR-V7 and ARV567ES, but not AR-FL, parallels increased expression of the AR-driven cell cycle gene UBE2C. In addition, protein expression of AR-V7, but not AR-FL, is positively correlated with UBE2C in clinical CRPC specimens. The cumulative in vitro and in vivo evidence support an adaptive shift toward AR-V-mediated signaling in at least a subset of CRPC tumors as the AR-LBD is rendered inactive, suggesting an important mechanism contributing to drug resistance to CRPC therapies. LNCaP cells lacking AR-V were transfected with AR-V7 with or without androgen stimulation of AR-FL (4 conditions); LNCaP95 cells expressing AR-Vs were treated with control siRNA or siRNA trageting AR-LBD or AR-DBD, with or without androgen stimulation of AR-FL (6 conditions); VCaP cells expressing AR-Vs in the presence of androgen were treated with control siRNA, siRNA trageting AR-LBD, DMSO or MDV3100 to inhibit AR-FL (4 conditions). Total 14 arrays with no replicates.

Project description:The development and progression of castrate resistant prostate cancer (CRPC), a lethal disease, is thought to be driven by multiple events. A hallmark of CRPC is the ability to evade the cytotoxic effects of anti-androgen therapy. Importantly, persistent androgen receptor (AR) signalling is thought to play a principal role in maintaining CRPC. The precise molecular alterations driving this condition, however, are not clearly understood. Our previous studies identified specific metabolic alterations associated with localized prostate cancer (PCa) and CRPC, implicating metabolic re-programming in disease progression. Building on these findings, using a novel network-based integromics approach, here we show distinct alterations in the Hexosamine Biosynthetic Pathway (HBP) to be critical for sustaining the castrate resistant state. We found expression of the HBP enzyme glucosamine-phosphate N-acetyltransferase 1 (GNPNAT1) was regulated by androgens and elevated in androgen dependent (AD) PCa while relatively diminished in CRPC possessing either full length AR (AR-FL) or the spliced V7 variant (AR-V7). Genetic loss of function experiments for GNPNAT1 in CRPC-like cells led to increased proliferation and aggressiveness, both, in vitro and in vivo. This was mediated by specific cell cycle genes regulated by the PI3K-AKT pathway activating either AR in cells with AR-FL or SP1-ChREBP (carbohydrate response element binding protein) in cells containing AR-V7. Strikingly, addition of HBP metabolite UDP-N-acetylglucosamine (UDP) to CRPC-like cells reduced the expression of cell cycle genes and attenuated tumor cell proliferation, both in vitro and in vivo. Furthermore, addition of UDP sensitized CRPC-like cells, inclusive of those possessing AR-V7, to enzalutamide, demonstrating the therapeutic value of targeting altered metabolic pathways in lethal PCa. We anticipate that our findings will motivate the development of novel metabolic therapeutic strategies that complement existing treatments for men with lethal prostate cancer We used microarray analysis to determine key molecular alterations associated with inhibition of HBP pathway in CRPC by knocking down GNPNAT1 transcript level using lentiviral particle bearing shRNA in 22Rv1 and LNCaP-ABL cells GNPNAT1 expression was knockdown in two independent prostate cancer cells, 22Rv1 and LNCaP-ABL

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Generation 2.5 Antisense Oligonucleotides Targeting the Androgen Receptor and its Splice Variants Suppress Enzalutamide-Resistant Prostate Cancer Cell Growth

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