A Comprehensive Overview of Small-Molecule Androgen Receptor Degraders: Recent Progress and Future Perspectives

Prostate cancer (PC), the second most prevalent malignancy in men worldwide, has been proven to depend on the aberrant activation of androgen receptor (AR) signaling. Long-term androgen deprivation for the treatment of PC inevitably leads to castration-resistant prostate cancer (CRPC) in which AR remains a crucial oncogenic driver. Thus, there is an urgent need to develop new strategies to address this unmet medical need. Targeting AR for degradation has recently been in a vigorous development stage, and accumulating clinical studies have highlighted the benefits of AR degraders in CRPC patients. Herein, we provide a comprehensive summary of small-molecule AR degraders with diverse mechanisms of action including proteolysis-targeting chimeras (PROTACs), selective AR degraders (SARDs), hydrophobic tags (HyT), and other AR degraders with distinct mechanisms. Accordingly, their structure–activity relationships, biomedical applications, and therapeutic values are also dissected to provide insights into the future development of promising AR degradation-based therapeutics for CRPC

Biosynthesis, Characterization, and Hemostasis Potential of Tailor-Made Poly(3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate) Produced by Haloferax mediterranei

We report the biosynthesis of poly­(3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate) random copolymers (R-PHBV) or higher-order copolymers (O-PHBV) in Haloferax mediterranei, with adjustable 3-hydroxyvalerate (3HV) incorporation by cofeeding valerate with glucose. Their microchemical structure, molecular weight and its distribution, and thermal and mechanical properties were characterized by NMR, GPC, DSC, TGA, and universal testing machine, respectively. ¹³C NMR studies showed that O-PHBV copolymers consisted of short segments of PHB and PHV covalently linked together with random PHBV segments. Consistently, two <i>T</i>_g were observed in the DSC curves of O-PHBV. The “blocky” feature of O-PHBV enhanced crystallinity percentages and improved Young’s modulus. Notably, the film of one O-PHBV copolymer, O-PHBV-1, showed unique foveolar cluster-like surface morphology with high hydrophobicity and roughness, as characterized using static contact angle and SEM and AFM analyses. It also exhibited increased platelet adhesion and accelerated blood clotting. The excellent hemostatic properties endow this copolymer with great potential in wound healing

The interaction between Tt-RpoE1 and different promoter DNA structures.

<p>The structure of parental probe is provided at the top. EMSA results of 5 µM Tt-RpoE1 protein binding with single-stranded (ssTop, ssBot.) or fork-junction structure promoter DNA(T+1/B−10); the vertical line indicates the terminal base-pair on the strands used in fork-junction probe. Free probe (T+1/B−10) was loaded as a negative control. The arrows indicate complexes formed by Tt-RpoE1 and the different probes.</p

The binding activities of the oligomerization-deficient mutants of TtDnaA at low (37°C) or high (60°C) temperature with full-length fragment

<p><b>Copyright information:</b></p><p>Taken from "Mechanism for the TtDnaA– cooperative interaction at high temperature and duplex opening at an unusual AT-rich region in "</p><p></p><p>Nucleic Acids Research 2007;35(9):3087-3099.</p><p>Published online 22 Apr 2007</p><p>PMCID:PMC1888806.</p><p>© 2007 The Author(s)</p> () Yeast two-hybrid assay for the protein self-interactions of TtDnaA and its mutants, the double-site-mutated TtDnaA (W9A/L20S, DM) and the Domain IV only (IV). The yeast strains harboring the following plasmids were streaked on the SD/−Leu/−Trp medium (left panel) and the SD/−Leu/−Trp/−His medium (right panel), respectively. (1) pGBKT7-53/pGADT7-T (positive control); (2) pGBKT7-TtDnaA/pGADT7-TtDnaA; (3) pGBKT7-DM/pGADT7-DM; (4) pGBKT7-IV/pGADT7-IV; (5) pGADT7/pGBKT7 (negative control). ( and ) Investigation of the interactions of the double-site mutant (W9A/L20S) of TtDnaA (B) and the Domain-IV only of TtDnaA (C) with the full-length fragment (472 bp, ∼20 fmol) at low (37°C) or high (60°C) temperature by EMSA. The amount of proteins (0–1800 nM) in each lane is indicated

Identification and Characterization of the Cognate Anti-Sigma Factor and Specific Promoter Elements of a <em>T. tengcongensis</em> ECF Sigma Factor

<div><p>Extracytoplasmic function (ECF) σ factors, the largest group of alternative σ factors, play important roles in response to environmental stresses. Tt-RpoE1 is annotated as an ECF σ factor in <em>Thermoanaerobacter tengcongensis</em>. In this study, we revealed that the <em>Tt-tolB</em> gene located downstream of the <em>Tt-rpoE1</em> gene encoded the cognate anti-σ factor, which could inhibit the transcription activity of Tt-RpoE1 by direct interaction with Tt-RpoE1 via its N-terminal domain. By <em>in vitro</em> transcription assay, the auto-regulation ability of Tt-RpoE1 was determined, and band shift assay showed that Tt-RpoE1 preferred to bind a fork-junction promoter DNA. With truncation or base-specific scanning mutations, the contribution of the nucleotides in −35 and −10 regions to interaction between Tt-RpoE1 and promoter DNA was explored. The promoter recognition pattern of Tt-RpoE1 was determined as 5′ tGTTACN₁₆CGTC 3′, which was further confirmed by <em>in vitro</em> transcription assays. This result showed that the Tt-RpoE1-recognized promoter possessed a distinct −10 motif (−13CGTC−10) as the recognition determinant, which is distinguished from the −10 element recognized by σ⁷⁰. Site-directed mutagenesis in Region 2.4 of Tt-RpoE1 indicated that the “D” residue of DXXR motif was responsible for recognizing the −12G nucleotide. Our results suggested that distinct −10 motif may be an efficient and general strategy used by ECF σ factors in adaptive response regulation of the related genes.</p> </div

Investigation of the interactions of the TtDnaA protein () and the Tt/EcDnaA protein () with the full-length fragment (472 bp, ∼20 fmol) at low (37°C) or high (60°C) temperature by EMSA (same as in )

<p><b>Copyright information:</b></p><p>Taken from "Mechanism for the TtDnaA– cooperative interaction at high temperature and duplex opening at an unusual AT-rich region in "</p><p></p><p>Nucleic Acids Research 2007;35(9):3087-3099.</p><p>Published online 22 Apr 2007</p><p>PMCID:PMC1888806.</p><p>© 2007 The Author(s)</p> In Tt/EcDnaA, the Domain-IV of TtDnaA was replaced with the counterpart of DnaA. The amount of proteins (0–1800 nM) in each lane is indicated

ER1626 inductive effect on cell apoptosis of MCF-7 and Ishikawa.

<p>Cells were grown in 6-well plates and apoptosis assay were performed following incubation with ER1626 (10⁻⁷, 10⁻⁶ and10⁻⁵M) for 24 h. Treated cells were processed with annexin V-FITC Apoptosis kit and analyzed in flow cytometery. <b>A</b> Typical pictures of the apoptotic cells in MCF-7; <b>B</b> Typical apoptosis pictures of Ishikawa cells; <b>C</b> Apoptosis ratios (the number of apoptotic cells in treatment groups to that of control group).</p

Reduction of VEGF secreted by MCF-7 and Ishikawa cells.

<p><b>A</b> MCF-7 and Ishikawa cells were planted respectively in 6-well dishes overnight and incubated with ER1626 (10⁻⁹, 10⁻⁸, 10⁻⁷, 10⁻⁶ or 10⁻⁵M) or control for 24 h. Elisa kit was employed to detect the VEGF production in the cultured medium. Inhibition ratio was expressed as the percentage of VEGF product in treated cells to those of the control cells (100%). <b>B</b> The relative VEGF level in ER1626-treated cultured system versus the relative ERα level in ER1626-treated MCF-7 and Ishikawa cells. *<i>p</i><0.05, **<i>p</i><0.01 compared with the control.</p

The expression of ERα and ERβ protein in ER1626-treated MCF-7 and Ishikawa cells.

<p><b>A</b>. Cells were respectively in 6-well plates and maintained in specific medium supplemented with 5% FBS for 24 h prior to incubation with ER1626 (10⁻⁷, 10⁻⁶ and 10⁻⁵M) or vehicle for another 24 h. Treated cells were lysed in RIPA buffer and cell lysate was electrophoresed. Immunoblotting was performed for ERα, ERβ and the loading control β-actin. <b>B</b> The intensity of the band of ERs protein was normalized and expressed as relative fold change in MCF-7 cells. <b>C</b> The intensity of ERs protein was expressed in Ishikawa cells.*<i>p</i><0.05,^#<i>p</i><0.05 compared with their corresponding control.</p

The effects of truncation in the −35 and −10 regions on the interaction between Tt-RpoE1 and promoter DNA.

<p>(<b>A</b>). EMSA results of truncation in the −35 region. The structure of parental probe is provided at the top, and vertical lines indicate truncated positions in the double-stranded region. Both the top and bottom strands were truncated from −40 to different positions indicated at the left of the fork-junction probe. The 3′ terminus of top strand was kept at +1, and the 5′ terminus of the bottom strand was kept at −10. (<b>B</b>). EMSA results of truncations in the −10 region. The structure of parental probe is provided at the top. The T+1 was the top strand for all the probes, and the bottom strand was truncated from B+1 to different positions as indicated on the right of the bottom strand. The dots denote the terminal bases in the bottom strands in fork-junction probes. The protein concentration was 5 µM in all of the following experiments.</p