A novel selective estrogen receptor degrader induces cell cycle arrest in breast cancer via ERα degradation and the autophagy-lysosome pathway.

Breast cancer (BC), a well-known estrogen-dependent cancer, is the most common cancer among women and the leading cause of cancer deaths. One of the most important therapeutic approaches for BC is endocrine therapy targeting estrogen receptor alpha (ERα) and thus blocking the estrogen receptor signaling pathway. Drugs, such as tamoxifen or fulvestrant, are developed based on this theory and have benefited numerous patients with BC for many years. However, many patients with advanced BC, such as tamoxifen-resistant BC, cannot benefit from these developed drugs anymore. Therefore, new drugs targeting ERα are urgently needed by patients with BC. Recently, elacestrant, a novel selective estrogen receptor degrader (SERD), was approved by the United States Food and Drug Administration (FDA), highlighting the importance of ERα degradation in endocrine therapy. Proteolysis targeting chimera (PROTAC) has been considered a powerful technique for targeting protein degradation (TPD). In this regard, we developed and studied a novel ERα degrader, which is a PROTAC-like SERD named 17e. We found that compound 17e can inhibit the growth of BC both in vitro and in vivo and induce the cell cycle arrest of BC. Importantly, 17e displayed no apparent toxicity toward healthy kidney and liver cells. Moreover, we observed that the presence of 17e led to a dramatic increase in the autophagy-lysosome pathway in an ERα-independent manner. Finally, we revealed that a decrease in MYC, a frequent deregulation oncogene in human cancers, was mediated by both ERα degradation and autophagy activation in the presence of 17e. Collectively, we discovered that compound 17e induced ERα degradation and exerts significant anti-cancer effects on BC mainly through promoting the autophagy-lysosome pathway and decreasing MYC level.

Discovery of aminothiazole derivatives as novel human enterovirus A71 capsid protein inhibitors.

Enterovirus A71 (EV-A71), one of the major pathogens that causes hand, foot and mouth disease (HFMD), has seriously threatened the health and safety of young children. In this study, aminothiazole derivatives were synthesized and screened against EV-A71 in Rhabdomyosarcoma (RD) cells. The best compound (12s), with a biphenyl group, showed activity against EV-A71 (EC50: 0.27 µM) but also against a series of different human enteroviruses without significant cytotoxicity (CC50 > 56.2 µM). Mechanistic studies including time-of-drug-addition assays, viral entry assays and microscale thermophoresis (MST) experiments, showed that 12s binds to EV-A71 capsid and blocks the binding between the viral protein VP1 and the relevant human scavenger receptor class B member 2 (hSCARB2).

OBHS impairs the viability of breast cancer via decreasing ERα and Atg13.

Breast cancer (BRCA) is one of the most threatening cancer types, especially among the female population. 70% of breast cancer are estrogen receptor α (ERα) positive and endocrine therapy is effective to decrease breast cancer risk. Autophagy, a highly conserved cellular recycling process, has been regarded to serve a protective role in BRCA. Autophagy-related gene 13 (Atg13) is participated in autophagy and is critical to autophagy initiation. Briefly, we observed that ERα, a well-known transcription factor that can promote breast cancer cell proliferation, expressed higher in breast cancer tissues. Moreover, ERα had a significant positive correlation with Atg13 and may be able to regulate the transcription of Atg13 via binding the promoter region of Atg13. Surprisingly, Oxabicycloheptene sulfonate (OBHS), the drug that we reported as a selective estrogen receptor modulator (SERM) before, may have the ability to decrease the expression of ERα and suppress the autophagy. In conclusion. We found that ERα could be involved in autophagy by binding the promoter of Atg13, and compound OBHS may be able to affect the viability of breast cancer cells by decreasing the expression of ERα and Atg13.

Novel hybrid conjugates with dual estrogen receptor α degradation and histone deacetylase inhibitory activities for breast cancer therapy.

Hormone therapy targeting estrogen receptors is widely used clinically for the treatment of breast cancer, such as tamoxifen, but most of them are partial agonists, which can cause serious side effects after long-term use. The use of selective estrogen receptor down-regulators (SERDs) may be an effective alternative to breast cancer therapy by directly degrading ERα protein to shut down ERα signaling. However, the solely clinically used SERD fulvestrant, is low orally bioavailable and requires intravenous injection, which severely limits its clinical application. On the other hand, double- or multi-target conjugates, which are able to synergize antitumor activity by different pathways, thus may enhance therapeutic effect in comparison with single targeted therapy. In this study, we designed and synthesized a series of novel dual-functional conjugates targeting both ERα degradation and histone deacetylase inhibiton by combining a privileged SERD skeleton 7-oxabicyclo[2.2.1]heptane sulfonamide (OBHSA) with a histone deacetylase inhibitor side chain. We found that substituents on both the sulfonamide nitrogen and phenyl group of OBHSA unit had significant effect on biological activities. Among them, conjugate 16i with N-methyl and naphthyl groups exhibited potent antiproliferative activity against MCF-7 cells, and excellent ERα degradation activity and HDACs inhibitory ability. A further molecular docking study indicated the interaction patterns of these conjugates with ERα, which may provide guidance to design novel SERDs or PROTAC-like SERDs for breast cancer therapy.

Curcumin inhibits BACE1 expression through the interaction between ERß and NFκB signaling pathway in SH-SY5Y cells.

Alzheimer's disease (AD) is the leading cause of dementia, which characterized by toxic senile plaques is composed of amyloid-ß (Aß). ß-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is the rate-limiting protease in Aß generation. Therefore, pharmacology BACE1 inhibition is one of the prime targets for potential treatment of AD. Curcumin, a yellow polyphenol derived from the rhizomes of the plant Curcuma longa Linn, has been reported to cross the blood-brain barrier and prevent Aß aggregation in AD models. However, its neuroprotective mechanism is still unclear. In the present study, we find that curcumin markedly reduces Aß levels in HEK293-APPswe cells. Our results show that curcumin inhibits BACE1 gene expression in SH-SY5Y cells at transcriptional and translational levels. Furthermore, we reveal that nuclear factor kappa B (NFκB) signaling is involved in the regulation of curcumin on BACE1. Interestingly, the estrogenicity of curcumin is found to partially contribute to its protective action. Our data show that curcumin activates estrogen receptor ß (ERß) selectively and the activation of ERß directly effects on the upstream factors of the NFκB signaling pathway. The above results indicate that curcumin reduces BACE1 expression through ERß and NFκB pathway, providing a novel mechanism for curcumin as a candidate for AD therapy.

Establishment of evaluation criteria for the development of high quality ERα-targeted fluorescent probes.

ERα-targeted fluorescent probes are important tools for ERα study. In order to develop high quality ERα-targeted probes, a sound and complete evaluation system is essential but has not been established yet. Herein, we set up a series of evaluation criteria for ERα-targeted fluorescent probes including ERα binding affinity, fluorescence quantum yield, cytotoxicity, ERα tracking capacity, ERα selectivity and ERα labeling ability. To verify the practicability of the evaluation criteria, we designed and synthesized two ERα-targeted fluorescent probes and fully characterized their properties based on the proposed evaluation criteria. It showed that the probes exhibited better performance. Moreover, we applied the probes in MCF-7 cells to study the ERα motion characteristics for the first time. We hope that our evaluation criteria could be helpful for the establishment of a complete evaluation system for ERα-targeted fluorescent probes.

Full antagonism of the estrogen receptor without a prototypical ligand side chain.

Resistance to endocrine therapies remains a major clinical problem for the treatment of estrogen receptor-α (ERα)-positive breast cancer. On-target side effects limit therapeutic compliance and use for chemoprevention, highlighting an unmet need for new therapies. Here we present a full-antagonist ligand series lacking the prototypical ligand side chain that has been universally used to engender antagonism of ERα through poorly understood structural mechanisms. A series of crystal structures and phenotypic assays reveal a structure-based design strategy with separate design elements for antagonism and degradation of the receptor, and access to a structurally distinct space for further improvements in ligand design. Understanding structural rules that guide ligands to produce diverse ERα-mediated phenotypes has broad implications for the treatment of breast cancer and other estrogen-sensitive aspects of human health including bone homeostasis, energy metabolism, and autoimmunity.

One-step pathway to selenoisobenzofuran-1(3H)-imine derivatives through highly selective selenocyclization of olefinic amides with benzeneselenyl chloride.

A 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyzed selenocyclization of olefinic amides was achieved under mild reaction conditions. The reaction formed various benzeneselenyl substituted isobenzofuran-1(3H)-imine derivatives in good yields. The product was determined using single-crystal X-ray analysis. For compound 2u, the relative stereochemistry was established on the basis of NOESY NMR studies.

Enantioselective synthesis of novel pyrano[3,2-c]chromene derivatives as AChE inhibitors via an organocatalytic domino reaction.

A series of optically active pyrano[3,2-c]chromenes have been synthesized through an asymmetric domino reaction of 4-hydroxy-2H-chromen-2-ones with malononitriles. The targeted molecules were obtained in excellent yields and enantioselectivities (up to 94% yield, 99% ee). The AChE inhibitory activity studies revealed that compounds 4n (IC50 = 21.3 µM) and 4p (IC50 = 19.2 µM) displayed potent acetylcholinesterase inhibition. In most cases, the S-enantiomers were superior to the corresponding R-enantiomers. Moreover, molecular modelling provides a practical method for understanding the enantioselective discrimination of AChE with these kinds of compounds.

Predictive features of ligand-specific signaling through the estrogen receptor.

Some estrogen receptor-α (ERα)-targeted breast cancer therapies such as tamoxifen have tissue-selective or cell-specific activities, while others have similar activities in different cell types. To identify biophysical determinants of cell-specific signaling and breast cancer cell proliferation, we synthesized 241 ERα ligands based on 19 chemical scaffolds, and compared ligand response using quantitative bioassays for canonical ERα activities and X-ray crystallography. Ligands that regulate the dynamics and stability of the coactivator-binding site in the C-terminal ligand-binding domain, called activation function-2 (AF-2), showed similar activity profiles in different cell types. Such ligands induced breast cancer cell proliferation in a manner that was predicted by the canonical recruitment of the coactivators NCOA1/2/3 and induction of the GREB1 proliferative gene. For some ligand series, a single inter-atomic distance in the ligand-binding domain predicted their proliferative effects. In contrast, the N-terminal coactivator-binding site, activation function-1 (AF-1), determined cell-specific signaling induced by ligands that used alternate mechanisms to control cell proliferation. Thus, incorporating systems structural analyses with quantitative chemical biology reveals how ligands can achieve distinct allosteric signaling outcomes through ERα.

Oxabicycloheptene Sulfonate Protects Against ß-Amyloid-induced Toxicity by Activation of PI3K/Akt and ERK Signaling Pathways Via GPER1 in C6 Cells.

Oxabicycloheptene sulfonate (OBHS) is a novel bicyclic core selective estrogen receptor modulator (SERM) with estrogen receptor (ER) antagonistic-activity and anti-inflammatory activity. However, little is known about protective action of OBHS on neurodegenerative disorders. In the present study, OBHS demonstrated a remarkably protective effect against amyloid beta (Aß) induced cytotoxicity via G-protein-coupled estrogen receptor 1 (GPER1) in rat astroglial cell line (C6). The C6 cell death induced by Aß was decreased by OBHS (1 µM) treatment for 45 min. This rapid protective action was blocked by GPER1 specific antagonist or siRNA knockdown. Inhibitors of phosphatidylinositol 3-kinase (PI3k)/Akt and extracellular signal-regulated kinase (ERK) activation also exhibited similar effects as GPER1 antagonist in blocking the protective effects of OBHS. Moreover, the expression of anti-apoptotic protein Bcl-2 was also increased by OBHS as a consequence of the activation of GPER1-PI3K/Akt and ERK pathways. Additionally, the phenyl sulfonate moiety of OBHS played a vital role in producing GPER1's agonist property according to the molecular docking analysis. These findings suggest that OBHS provide protection directed at enhancing glial cell survival through the activation of GPER1, which, in turn, offers a novel insight into the molecular mechanisms behind the potential application of OBHS in treating Alzheimer's disease (AD).

Dual functional small molecule fluorescent probes for image-guided estrogen receptor-specific targeting coupled potent antiproliferative potency for breast cancer therapy.

A strategy by integrating biological imaging into early stages of the drug discovery process can improve our understanding of drug activity during preclinical and clinical study. In this article, we designed and synthesized coumarin-based nonsteroidal type fluorescence ligands for drug-target binding imaging. Among these synthesized compounds, 3e, 3f and 3h showed potent ER binding affinity and 3e (IC50=0.012µM) exhibited excellent ERα antagonistic activity, its antiproliferative potency in breast cancer MCF-7 cells is equipotent to the approved drug tamoxifen. The fluorescence of compounds 3e and 3f depended on the solvent properties and showed significant changes when mixed with ERα or ERß in vitro. Furthermore, target molecule 3e could cross the cell membrane, localize and image drug-target interaction in real time without cell washing. Thus, the coumarin-based platform represents a promising new ER-targeted delivery vehicle with potential imaging and therapeutic properties.

Applications of Chiral Squaramides: From Asymmetric Organocatalysis to Biologically Active Compounds.

This review seeks to provide coverage on the recent advances in chiral squaramide-catalyzed asymmetric transformations and their applications in the synthesis of a variety of chiral biologically active compounds. It aims to give an overview highlighting the new reaction types and enantioenriched medicinal scaffolds developed in the last few years.

Synthesis and structure-activity relationships of novel hybrid ferrocenyl compounds based on a bicyclic core skeleton for breast cancer therapy.

Breast cancer is the most frequent cancer in women worldwide, and incidence is increasing year by year. Although current selective estrogen receptor modulators (SERMs) have clear advantages in the treatment of hormone-responsive breast cancer, they are ineffective for ER(-). In this study, we describe the design and synthesis of a series of dual-acting estrogen receptor (ER) and histone deacetylase (HDAC) inhibitors with incorporation of the ferrocenyl moiety, leading to novel hybrid ferrocenyl complexes (FcOBHS-HDACis) for breast cancer therapy. It is worth to note that these ferrocenyl conjugates could not only potently inhibit HDACs and the proliferation of ERα positive (ER(+)) breast cancer cells (MCF-7), but also show significant antiproliferative effect on ER(-) breast cancer cells (MDA-MB-231). Thus, the FcOBHS-HDACi conjugates represent a novel approach to the development of efficiently dual-acting agents for treatment of breast cancer.

Synthesis and SARs of indole-based α-amino acids as potent HIV-1 non-nucleoside reverse transcriptase inhibitors.

A series of non-nucleoside reverse transcriptase inhibitors derived from indole-based α-amino acids were designed and synthesized. Their inhibitory activities were detected by a TZM-bl cell assay on HIV virus type HIV-1IIIB. The comprehensive understanding of the SAR was obtained by utilizing the variation of the substituents of the indole-based α-amino acids. From the screened compounds, the novel inhibitors 19 and 29 were identified to be highly potent candidates with EC50 values of 0.060 µM and 0.045 µM respectively (CC50 values of 109.545 µM and 49.295 µM and SI values of 1825.8 and 1095.4). In most cases, the variation of substituents at different positions had a significant effect on the potency of activities. The results also indicate that the indole-based α-amino acids as efficient NNRTIs displayed comparable anti-HIV-1 activities to the reference drug NVP. We hope the identification of these indole-based amino acids as efficient NNRTIs of RT could stimulate researchers to develop more diversified anti-HIV drugs.

OBHSA, a novel selective estrogen receptor degrader, overcomes tamoxifen resistance through cell cycle arrest and unfolded protein response-mediated apoptosis in breast cancer.

Breast cancer (BC) is a highly heterogeneous tumor that has surpassed lung cancer as the most frequently diagnosed cancer in women. In clinical practice,the primary approach for treating estrogen receptor alpha (ERα)-positive BC is through endocrine therapy, which involves targeting the ERα using medications like tamoxifen and fulvestrant. However, the problem of de novo or acquired resistance poses a significant clinical challenge, emphasizing the critical need for the development of novel therapeutic strategies. In this regard, we have successfully designed and developed a novel selective estrogen receptor degrader (SERD) called OBHSA, which specifically targets and degrades ERα, demonstrating remarkable efficacy. Our findings revealed the effectiveness of OBHSA in inhibiting the proliferation of various BC cells, including both tamoxifen-sensitive and tamoxifen-resistant BC cells, indicating its great potential to overcome endocrine resistance. In terms of mechanism, we discovered that OBHSA overcame tamoxifen resistance through two distinct pathways. Firstly, OBHSA degraded cyclin D1 in an ERα-dependent manner, thereby blocking the cell cycle. Secondly, OBHSA induced an elevation in intracellular reactive oxygen species, triggering an excessive activation of the unfolded protein response (UPR) and ultimately leading to apoptotic cell death. In summary, our finding demonstrated that OBHSA exerts anti-tumor effects by inducing cell cycle arrest and UPR-mediated apoptosis. These findings hold promise for the development of novel therapeutic drugs targeting endocrine-resistant BC.

Novel estrogen receptor ß/histone deacetylase dual-targeted near-infrared fluorescent probes as theranostic agents for imaging and treatment of prostate cancer.

Estrogen receptor (ER) ß and histone deacetylases (HDACs), when overexpressed, are associated closely with the occurrence and development of prostate cancer and are, therefore, considered important targets and biomarkers used in the clinical treatment of prostate cancer. The present study involved the design and synthesis of the first ERß and HDAC dual-target near-infrared fluorescent probe with both imaging capacity and antitumor activity for prostate cancer. Both P1 and P2 probes exhibited excellent ERß selectivity, with P1 being almost exclusively selective for ERß compared to ERα. In addition, P1 exhibited good optical properties, such as strong near-infrared emission, large Stokes shift, and better anti-interference ability, along with excellent imaging ability for living cells. P1 also exhibited potent inhibitory activity against HDAC6 and DU-145 cells, with IC50 values of 52 nM and 0.96 µM, respectively. Further, P1 was applied successfully for the in vivo imaging of prostate cancer in a mouse model, and significant in vivo antitumor efficacy was achieved. The developed dual-target NIR fluorescent probe is expected to serve as an effective tool in the research on prostate cancer, leading to novel insights for the theranostic study of diseases related to ERß and HDACs.

Fluorescence theranostic PROTACs for real-time visualization of ERα degradation.

Proteolysis targeting chimera (PROTAC) technology, a groundbreaking strategy for degradation of pathogenic proteins by hijacking of the ubiquitin-proteasome-system has become a promising strategy in drug design. However, the real-time monitoring and visualization of protein degradation processes have been long-standing challenges in the realm of drug development. In this research, we sought to amalgamate the highly efficient protein-degrading capabilities of PROTAC technology with the visualization attributes of fluorescent probes, with the potential to pave the path for the design and development of a novel class of visual PROTACs. These novel PROTACs uniquely possess both fluorescence imaging and therapeutic characteristics, all with the goal of enabling real-time observations of protein degradation processes. Our approach involved the utilization of a high ER-targeting fluorescent probe, previously reported in our laboratory, which served as a warhead that specifically binds to the protein of interest (POI). Additionally, a VHL ligand for recruiting E3 ligase and linkers of various lengths were incorporated to synthesize a series of novel ER-inherent fluorescence PROTACs. Among them, compound A3 demonstrated remarkable efficiency in degrading ERα proteins (DC50 = 0.12 µM) and displaying exceptional anti-proliferative activity against MCF-7 cells (IC50 = 0.051 µM). Furthermore, it exhibited impressive fluorescence imaging performance, boasting an emission wavelength of up to 582 nm, a Stokes shift of 116 nm, and consistent optical properties. These attributes make it especially suitable for the real-time, in situ tracking of ERα protein degradation processes, thus may serve as a privileged visual theranostic PROTAC for ERα+ breast cancer. This study not only broadens the application spectrum of PROTAC technology but also introduces a novel approach for real-time visualization of protein degradation processes, ultimately enhancing the diagnostic and treatment efficacy of PROTACs.