Castration-recurrent prostate cancer (CRPC) is suspected to depend on androgen receptor (AR). The AF-1 region in the amino-terminal domain (NTD) of AR contains most, if not all, of the transcriptional activity. Here we identify EPI-001, a small molecule that blocked transactivation of the NTD and was specific for inhibition of AR without attenuating transcriptional activities of related steroid receptors. EPI-001 interacted with the AF-1 region, inhibited protein-protein interactions with AR, and reduced AR interaction with androgen-response elements on target genes. Importantly, EPI-001 blocked androgen-induced proliferation and caused cytoreduction of CRPC in xenografts dependent on AR for growth and survival without causing toxicity.

Hormone therapies for advanced prostate cancer target the androgen receptor (AR) ligand-binding domain (LBD), but these ultimately fail and the disease progresses to lethal castration-resistant prostate cancer (CRPC). The mechanisms that drive CRPC are incompletely understood, but may involve constitutively active AR splice variants that lack the LBD. The AR N-terminal domain (NTD) is essential for AR activity, but targeting this domain with small-molecule inhibitors is complicated by its intrinsic disorder. Here we investigated EPI-001, a small-molecule antagonist of AR NTD that inhibits protein-protein interactions necessary for AR transcriptional activity. We found that EPI analogs covalently bound the NTD to block transcriptional activity of AR and its splice variants and reduced the growth of CRPC xenografts. These findings suggest that the development of small-molecule inhibitors that bind covalently to intrinsically disordered proteins is a promising strategy for development of specific and effective anticancer agents.

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The genome of the kinetoplastid parasite Trypanosoma brucei encodes four homologs of the Saccharomyces cerevisiae 59/39 exoribonucleases Xrn1p and Xrn2p/Rat1p, XRNA, XRNB, XRNC, and XRND. In S. cerevisiae, Xrn1p is a cytosolic enzyme involved in degradation of mRNA, whereas Xrn2p is involved in RNA processing in the nucleus. Trypanosome XRND was found in the nucleus, XRNB and XRNC were found in the cytoplasm, and XRNA appeared to be in both compartments. XRND and XRNA were essential for parasite growth. Depletion of XRNA increased the abundances of highly unstable developmentally regulated mRNAs, perhaps by delaying a deadenylation-independent decay pathway. Degradation of more stable or unregulated mRNAs was not affected by XRNA depletion although a slight decrease in average poly(A) tail length was observed. We conclude that in trypanosomes 59/39 exonuclease activity is important in degradation of highly unstable, regulated mRNAs, but that for other mRNAs another step is more important in determining the decay rate.

The Toxoplasma gondii SRS gene superfamily is structurally related to SRS29B (formerly SAG1), a surface adhesin that binds host cells and stimulates host immunity. Comparative genomic analyses of three Toxoplasma strains identified 182 SRS genes distributed across 14 chromosomes at 57 genomic loci. Eight distinct SRS subfamilies were resolved. A core 69 functional gene orthologs were identified, and strain-specific expansions and pseudogenization were common. Gene expression profiling demonstrated differential expression of SRS genes in a developmental-stage- and strain-specific fashion and identified nine SRS genes as priority targets for gene deletion among the tissue-encysting coccidia. A Δsag1 ∆sag2A mutant was significantly attenuated in murine acute virulence and showed upregulated SRS29C (formerly SRS2) expression. Transgenic overexpression of SRS29C in the virulent RH parent was similarly attenuated. Together, these findings reveal SRS29C to be an important regulator of acute virulence in mice and demonstrate the power of integrated genomic analysis to guide experimental investigations.

Levels of 27 transcripts were investigated as potential novel markers for prostate cancer, including genes encoding plasma membrane proteins (ADAM2, ELOVL5, MARCKSL1, RAMP1, TMEM30A, and TMEM66); secreted proteins (SPON2, TMEM30A, TMEM66, and truncated TMEFF2 (called POP4)); intracellular proteins (CAMK2N1, DHCR24, GLO1, NGFRAP1, PGK1, PSMA7, SBDS, and YWHAQ); and noncoding transcripts (POP1 (100 kb) from mRNA AK000023), POP2 (4 kb from mRNA AL832227), POP3 (50 kb from EST CFI40309), POP5 (intron of NCAM2, accession DO668384), POP6 (intron of FHIT), POP7 (intron of TNFAIP8), POP8 (intron of EFNA5), POP9 (intron of DSTN), POP10 (intron of ADAM2, accession DO668396), POP11 (87kb from EST BG194644), and POP12 (intron of EST BQ226050)). Expression of POP3 was prostate specific, whereas ADAM2, POP1, POP4, POP10, ELOVL5, RAMP1, and SPON2 had limited tissue expression. ELOVL5, MARCKSL1, NGFRAP1, PGK1, POP2, POP5, POP8, PSMA7, RAMP1, and SPON2 were significantly differentially expressed between laser microdissected malignant versus benign clinical samples of prostate tissue. PGK1, POP2, and POP12 correlated to clinical parameters. Levels of CAMK2N1, GLO1, SDBS, and TMEM30A transcripts tended to be increased in primary prostate cancer from patients who later had biochemical failure. Expression of GLO1, DHCR24, NGFRAP1, KLK3, and RAMP1 were significantly decreased in metastatic castration-recurrent disease compared with androgen-dependent primary prostate cancer. These novel potential biomarkers may therefore be useful in the diagnosis/prognosis of prostate cancer.

Androgen receptor (AR) is a transcription factor that becomes active upon binding to androgens via its ligand-binding domain (LBD) or in response to signaling cascades initiated by growth factors and cytokines. The activity of AR requires regions within the N-terminal domain (NTD) in a manner that is distinct from the activation of related steroid hormone receptors. Unequivocal evidence has been amassed to consider that the AR axis is the most critical pathway for the progression of prostate cancer. Qualitatively distinct insight into AR pathobiology has been garnered that include AR-regulated gene expression is stage-specifically modulated during disease progression and that ligand requirement for AR activity could be rendered dispensable due to expression of constitutively active AR splice variants that are devoid of LBD. The recent appreciation of the clinical challenge that stems from non-gonadal androgens that are not inhibited by traditional hormonal therapies has been tangibly translated into the development of more potent drugs that can potentially lead towards achieving an androgen-free environment. The pre-clinical evidence that proves the AR NTD is a druggable target also forecasts further paradigm shift in the management of advanced prostate cancer. These advancements together with the identification of more robust AR antagonists and their promising clinical outcome has renewed the hope that targeting the AR pathway remains a sound strategy in the clinical management of prostate cancer. Here, we address these developments with a greater emphasis to the rapidly growing literature on AR splice variants.