Structural basis for dimerization of a paramyxovirus polymerase complex.

The transcription and replication processes of non-segmented, negative-strand RNA viruses (nsNSVs) are catalyzed by a multi-functional polymerase complex composed of the large protein (L) and a cofactor protein, such as phosphoprotein (P). Previous studies have shown that the nsNSV polymerase can adopt a dimeric form, however, the structure of the dimer and its function are poorly understood. Here we determine a 2.7 Å cryo-EM structure of human parainfluenza virus type 3 (hPIV3) L-P complex with the connector domain (CD') of a second L built, while reconstruction of the rest of the second L-P obtains a low-resolution map of the ring-like L core region. This study reveals detailed atomic features of nsNSV polymerase active site and distinct conformation of hPIV3 L with a unique ß-strand latch. Furthermore, we report the structural basis of L-L dimerization, with CD' located at the putative template entry of the adjoining L. Disruption of the L-L interface causes a defect in RNA replication that can be overcome by complementation, demonstrating that L dimerization is necessary for hPIV3 genome replication. These findings provide further insight into how nsNSV polymerases perform their functions, and suggest a new avenue for rational drug design.

Simvastatin functions as a heat shock protein 90 inhibitor against triple-negative breast cancer.

Acetylation plays an important role in regulating the chaperone activity of heat shock protein 90 (Hsp90) during malignant transformation through the stabilization and conformational maturation of oncogenic proteins. However, the functional acetylation sites, potential anticancer drug targets, are still emerging. We found that acetylation at K292 in Hsp90α is critical for the development and treatment of breast cancer. Acetylation at K292 not only augments the affinity of Hsp90 to ATP, cochaperones, and client proteins but it also promotes cancer cell colony formation, migration, and invasion in vitro as well as tumor growth in vivo. Importantly, K292-acetylated Hsp90 has been validated as an exciting anticancer drug target by interfering with the complex formation between K292-acetylated Hsp90 and cochaperone Cdc37, leading to diminishment of kinase client maturation and proteasome-dependent degradation of kinase substrates. Furthermore, we showed that simvastatin prevented, whereas LBH589 promoted, the progression of Hsp90 chaperone cycling and client maturation, resulting in an increment of cell apoptosis by the combination of simvastatin and LBH589 in a mouse xenograft model. These data suggest that simvastatin is a novel Hsp90 inhibitor to disrupt the formation of the K292-acetylated Hsp90/Cdc37 complex in triple-negative breast cancer cells. The combination of simvastatin with LBH589 could be used as a novel therapeutic strategy for triple-negative breast cancer.

Vorinostat and Simvastatin have synergistic effects on triple-negative breast cancer cells via abrogating Rab7 prenylation.

Since the lack of targeted treatment, triple-negative breast cancer (TNBC) has poor outcomes. Histone deacetylase inhibitors (HDACi) blocking the activity of specific HDACs have emerged as cancer therapeutic agents. However, the therapeutic efficiency is still not satisfactory for patients with solid tumor. We thus performed screening for the synergistic agents of Vorinostat (SAHA). The resulting candidate Simvastatin was obtained. The efficacy and mechanism of combination have been studied in TNBC cells. The synergism of SAHA and Simvastatin was evaluated by IC50 of proliferation and combination index (CI). The antitumor activities of combination were further evaluated in TNBC cells. The pro-apoptotic effects were determined by flow cytometry and Western blot. Autophagosome-lysosome fusion was monitored using confocal microscope. The underlying mechanism was further studied by over-expressing of wild-type or inactive (C205S/C207S) Rab7 in compounds treated cells. The in vivo efficacy was also evaluated in mice. The combination of SAHA and Simvastatin had potent synergism in apoptosis of TNBC cells. It exerted pro-apoptosis effect by compromising the fusion between autophagosome and lysosome. Over-expressing of wild-type, but not inactive Rab7 rescued cells from apoptosis induced by the combinatory treatments. Mevalonate supplementation also decreased the combinatory treatment-induced apoptosis. These results indicate that the combinatory treatment enhances the apoptosis of TNBC cells by interrupting Rab7 prenylation and obstructing autophagosome-lysosome fusion. Combination between SAHA and Simvastatin could also significantly decrease the tumor growth in xenografted mice by inducing apoptosis and inhibiting Rab7 prenylation. Rab7 is a potential target for the combined effects of Simvastatin and SAHA.

The flavonoid TL-2-8 induces cell death and immature mitophagy in breast cancer cells via abrogating the function of the AHA1/Hsp90 complex.

The flavonoid quercetin exhibits significant anticancer activities with few side effects. In the current study, we characterized TL-2-8, a quercetin derivative, as a novel anticancer agent in vitro and in vivo. Cell proliferation and viability were assessed using Cell Counting Kit-8 and CellTiter-Blue assay, respectively. Cell death was examined using PI staining or a TUNEL assay. Mitophagy was determined by measuring autophagic flux and by confocal imaging. Protein expression was examined by Western blotting. We found that TL-2-8 selectively inhibited the proliferation and decreased the viability of various cancer cells (the anti-proliferation IC50 values in MDA-MB-231, MDA-MB-468 and MCF-7 breast cancer cells at 72 h were 8.28, 8.56, and 9.58 µmol/L, respectively), and it displayed only slight cytotoxicity against normal MCF-10A and HEK-293 cells. In MDA-MB-231 and MDA-MB-468 breast cancer cells, TL-2-8 treatment induced the degradation of multiple Hsp90 client proteins without inducing Hsp70. TL-2-8 (3, 6, 12 µmol/L) dose-dependently inhibited the expression of AHA1, an activator of Hsp90 ATPase, and decreased Hsp90-AHA1 complex formation, leading to decreased Hsp90 chaperone function and reduced polo-like kinase 1 (PLK1) signaling. Consequently, impaired mitophagy was induced via the downregulation of lysosomal-associated membrane protein 2 (LAMP2). The in vivo anticancer effects of TL-2-8 were evaluated in an MDA-MB-231 breast cancer xenograft model, which was treated with TL-2-8 (25, 50, 100 mg·kg-1·d-1, po). Administration of TL-2-8 resulted in tumor growth inhibition rates of 37.9%, 58.9% and 70.9%, respectively, whereas quercetin treatment (100 mg·kg-1·d-1, po) produced only a lower tumor growth inhibition rate (49.5%). Furthermore, TL-2-8 treatment significantly extended the lifespan of mice bearing MDA-MB-231 breast cancer cell xenografts. Our results demonstrate that TL-2-8 induces significant cell death and immature mitophagy in breast cancer cells in vitro and in vivo via AHA1 abrogation.

Mevastatin blockade of autolysosome maturation stimulates LBH589-induced cell death in triple-negative breast cancer cells.

Histone deacetylase inhibitors (HDACi) are promising anti-cancer agents, and combining a HDACi with other agents is an attractive therapeutic strategy in solid tumors. We report here that mevastatin increases HDACi LBH589-induced cell death in triple-negative breast cancer (TNBC) cells. Combination treatment inhibited autophagic flux by preventing Vps34/Beclin 1 complex formation and downregulating prenylated Rab7, an active form of the small GTPase necessary for autophagosome-lysosome fusion. This means that co-treatment with mevastatin and LBH589 activated LKB1/AMPK signaling and subsequently inhibited mTOR. Co-treatment also led to cell cycle arrest in G2/M phase and induced corresponding expression changes of proteins regulating the cell cycle. Co-treatment also increased apoptosis both in vitro and in vivo, and reduced tumor volumes in xenografted mice. Our results indicate that disruption of autophagosome-lysosome fusion likely underlies mevastatin-LBH589 synergistic anticancer effects. This study confirms the synergistic efficacy of, and demonstrates a potential therapeutic role for mevastatin plus LBH589 in targeting aggressive TNBC, and presents a novel therapeutic strategy for further clinical study. Further screening for novel autophagy modulators could be an efficient approach to enhance HDACi-induced cell death in solid tumors.

Targeting Hippo pathway by specific interruption of YAP-TEAD interaction using cyclic YAP-like peptides.

Hippo signaling pathway is emerging as a novel target for anticancer therapy because it plays key roles in organ size control and tumorigenesis. As the downstream effectors, Yes-associated protein (YAP)-transcriptional enhancer activation domain family member (TEAD) association is essential for YAP-driven oncogenic activity, while TEAD is largely dispensable for normal tissue growth. We present the design of YAP-like peptides (17mer) to occupy the interface 3 on TEAD. Introducing cysteines at YAP sites 87 and 96 can induce disulfide formation, as confirmed by crystallography. The engineered peptide significantly improves the potency in disrupting YAP-TEAD interaction in vitro. To confirm that blocking YAP-TEAD complex formation by directly targeting on TEAD is a valid approach, we report a significant reduction in tumor growth rate in a hepatocellular carcinoma xenograft model after introducing the dominant-negative mutation (Y406H) of TEAD1 to abolish YAP-TEAD interaction. Our results suggest that targeting TEAD is a promising strategy against YAP-induced oncogenesis.

Structure-Based Design and Synthesis of Potent Cyclic Peptides Inhibiting the YAP-TEAD Protein-Protein Interaction.

The YAP-TEAD protein-protein interaction (PPI) mediates the oncogenic function of YAP, and inhibitors of this PPI have potential usage in treatment of YAP-involved cancers. Here we report the design and synthesis of potent cyclic peptide inhibitors of the YAP-TEAD interaction. A truncation study of YAP interface 3 peptide identified YAP(84-100) as a weak peptide inhibitor (IC50 = 37 µM), and an alanine scan revealed a beneficial mutation, D94A. Subsequent replacement of a native cation-π interaction with an optimized disulfide bridge for conformational constraint and synergistic effect between macrocyclization and modification at positions 91 and 93 greatly boosted inhibitory activity. Peptide 17 was identified with an IC50 of 25 nM, and the binding affinity (K d = 15 nM) of this 17mer peptide to TEAD1 proved to be stronger than YAP(50-171) (K d = 40 nM).

Targeting cadherin-17 inactivates Ras/Raf/MEK/ERK signaling and inhibits cell proliferation in gastric cancer.

Cadherin-17 (CDH17), one member of 7D-cadherin superfamily, was overexpressed in gastric cancer (GC) and was associated with poor survival, tumor recurrence, metastasis, and advanced tumor stage. So far the cellular function and signaling mechanism of CDH17 in GC remains unclear. In this study, we showed that over 66% of GC cell lines (20/30) were CDH17 positive. Tissue microarray (TMA) assay showed that 73.6% Chinese GC tissues (159/216) were CDH17 positive, while 37% respective adjacent normal tissues were CDH17 positive. Knockdown of CDH17 inhibited cell proliferation, migration, adhesion and colony formation, and also induced a cell cycle arrest and apoptosis in AGS human GC cells. On the other side, overexpression of CDH17 facilitated MGC-803 GC tumor growth in nude mice. Antibody array and Western blotting assay demonstrated that knockdown of CDH17 in AGS cells down-regulated integrin ß series proteins, further inactivated the Ras/Raf/MEK/ERK pathway and led to p53 and p21 accumulation, which resulted in proliferation inhibition, cell-cycle arrest and apoptosis induction. Collectively, our data firstly demonstrate the capacity of CDH17 to regulate the activity of Ras/Raf/MEK/ERK pathway for cell proliferation in GC, and suggest that CDH17 can serve as an attractive therapeutic target for future research.

Four-membered heterocycles-containing 4-anilino-quinazoline derivatives as epidermal growth factor receptor (EGFR) kinase inhibitors.

We report herein the design and synthesis of novel azaspirocycle or azetidine substituted 4-anilinoquinazoline derivatives. The EGFR inhibitory activities and in vitro antitumor potency of these newly synthesized compounds against two lung cancer cell lines HCC827 and A549 were evaluated. Most of the target compounds possess good inhibitory potency. In particular, compounds 21g with 2-oxa-6-azaspiro[3.4]octane substituent was found to possess higher EGFR inhibitory activities and similar antitumor potency comparing to the lead compound gefitinib with improved water solubility.

Small molecule R1498 as a well-tolerated and orally active kinase inhibitor for hepatocellular carcinoma and gastric cancer treatment via targeting angiogenesis and mitosis pathways.

Protein kinases play important roles in tumor development and progression. Lots of kinase inhibitors have entered into market and show promising clinical benefits. Here we report the discovery of a novel small molecule, well-tolerated, orally active kinase inhibitor, R1498, majorly targeting both angiogenic and mitotic pathways for the treatment of hepatocellular carcinoma (HCC) and gastric cancer (GC). A series of biochemical and cell-based assays indicated that the target kinase cluster of R1498 included Aurora kinases and VEGFR2 et al. R1498 showed moderate in vitro growth inhibition on a panel of tumor cells with IC50 of micromole range. The in vivo anti-tumor efficacy of R1498 was evaluated on a panel of GC and HCC xenografts in a parallel comparison with another multikinase inhibitor sorafenib. R1498 demonstrated superior efficacy and toxicity profile over sorafenib in all test models with >80% tumor growth inhibition and tumor regression in some xenogratfts. The therapeutic potential of R1498 was also highlighted by its efficacy on three human GC primary tumor derived xenograft models with 10-30% tumor regression rate. R1498 was shown to actively inhibit the Aurora A activity in vivo, and decrease the vascularization in tumors. Furthermore, R1498 presented good in vivo exposure and therapeutic window in the pharmacokinetic and dose range finding studies. Theses evidences indicate that R1498 is a potent, well-tolerated, orally active multitarget kinase inhibitor with a unique antiangiogenic and antiproliferative profile, and provide strong confidence for further development for HCC and GC therapy.

The molecular basis of ABA-independent inhibition of PP2Cs by a subclass of PYL proteins.

PYR1/PYL/RCAR proteins (PYLs) are confirmed abscisic acid (ABA) receptors, which inhibit protein phosphatase 2C (PP2C) upon binding to ABA. Arabidopsis thaliana has 14 PYLs, yet their functional distinction remains unclear. Here, we report systematic biochemical characterization of PYLs. A subclass of PYLs, represented by PYL10, inhibited PP2C in the absence of any ligand. Crystal structures of PYL10, both in the free form and in the HAB1 (PP2C)-bound state, revealed the structural basis for its constitutive activity. Structural-guided biochemical analyses revealed that ABA-independent inhibition of PP2C requires the PYLs to exist in a monomeric state. In addition, the residues guarding the entrance to the ligand-binding pocket of these PYLs should be bulky and hydrophobic. Based on these principles, we were able to generate monomeric PYL2 variants that gained constitutive inhibitory effect on PP2Cs. These findings provide an important framework for understanding the complex regulation of ABA signaling by PYL proteins.

Butyl 4-(butyryloxy)benzoate functions as a new selective estrogen receptor beta agonist and induces GLUT4 expression in CHO-K1 cells.

Estrogen receptors (ERs) belong to nuclear hormone receptor superfamily and can be activated by estrogens and regulate many target genes. Two ER isoforms, ERalpha and ERbeta have been discovered to date and ERbeta was indicated to involve in anti-inflammatory and anti-diabetogenic effects. Recently, some studies also demonstrated an association between ERbeta and GLUT4 expression. The development of selective ERbeta ligand has facilitated probing its novel biological functions and clinical benefits. In this work, a new ERbeta selective agonist, butyl 4-(butyryloxy)benzoate (DCW234), was discovered as investigated by surface plasmon resonance (SPR) technology, yeast two-hybrid and cell-based transcription-based assays. SPR results demonstrated that DCW234 has a higher binding affinity against ERbeta over ERalpha and induces a strong and selective stimulation on ERbeta/SRC1 interaction, which could be efficiently blocked by Tamoxifen. Meanwhile, the yeast two-hybrid technology-based assay indicated that DCW234 exhibits a higher agonistic activity ( approximately 13-fold) in stimulating ERbeta ligand-binding domain (LBD) interaction with SRC1 (EC(50)=2.5 microM) than ERalpha-LBD/SRC1 interaction (EC(50)=32.7 microM). The cell-based transcriptional assay further proved the potency and selectivity of DCW234. Moreover, DCW234 was found to be able to induce GLUT4 expression in CHO-K1 cell. The discovered DCW234 might be hopefully developed as a potential lead compound for further research.

Bcl-xL forms two distinct homodimers at non-ionic detergents: implications in the dimerization of Bcl-2 family proteins.

As the key regulator of apoptosis, Bcl-2 family protein controls the cell death by forming homo- or heterodimers among anti-apoptotic and pro-apoptotic members of this family. Here we have studied Bcl-x(L) homodimerization at different pH in the presence of various detergents and organic solvents. We found that both acidic and basic pHs are beneficial for Bcl-x(L) dimerization. High concentrations of non-ionic detergents and some organic solvents can significantly promote this event. In addition to non-covalently linked acidic-dimer as that formed at acidic pH, Bcl-x(L) formed disulphide-bonded detergent-dimer at neutral and basic pH when incubated with high concentrations of non-ionic detergents. The acidic-dimer retains the BH3 peptide binding activity, whereas the detergent-dimer does not. The formation of acidic-dimer and detergent-dimer implies that Bcl-x(L) may dimerize via two different pathways under certain conditions. The implications of these findings has been discussed with previous experimental results, which provides some new insight into the events and would help the experiment design and data interpretation when non-ionic detergents are used to study the dimerization and pore formation of Bcl-2 family proteins.

Aza analogues of equol: novel ligands for estrogen receptor beta.

3-Aryl-tetrahydroquinolines, aza analogues of equol, are synthesized and evaluated for their binding properties to the estrogen receptors ERalpha and ERbeta. Several of these compounds exhibited binding selectivity for ER similar to that of genistein. Compounds 8c and 8d were found to have dual actions: antagonists for ERalpha and agonists for ERbeta in a yeast two-hybrid assay. These compounds have no estrogenic effects on the uterus and bone in vivo.