Extracellular HSP90 promotes differentiation of lens epithelial cells to fiber cells by activating LRP1-YAP-PROX1 axis.

Capsular residual lens epithelial cells (CRLEC) undergo differentiation to fiber cells for lens regeneration or tansdifferentiation to myofibroblasts leading to posterior capsular opacification (PCO) after cataract surgery. The underlying regulatory mechanism remains unclear. Using human lens epithelial cell lines and the ex vivo cultured rat lens capsular bag model, we found that the lens epithelial cells secrete HSP90α extracellularly (eHSP90) through an autophagy-associated pathway. Administration of recombinant GST-HSP90α protein or its M-domain induces the elongation of rat CRLEC cells with concomitant upregulation of the crucial fiber cell transcriptional factor PROX1and its downstream targets, ß- and γ-crystallins and structure proteins. This regulation is abolished by PROX1 siRNA. GST-HSP90α upregulates PROX1 by binding to LRP1 and activating LRP1-AKT mediated YAP degradation. The upregulation of GST-HSP90α on PROX1 expression and CRLEC cell elongation is inhibited by LRP1 and AKT inhibitors, but activated by YAP-1 inhibitor (VP). These data demonstrated that the capsular residue epithelial cells upregulate and secrete eHSP90α, which in turn drive the differentiation of lens epithelial cell to fiber cells. The recombinant HSP90α protein is a potential novel differentiation regulator during lens regeneration.

Crosstalk between heat shock factor 1 and signal transducer and activator of transcription 3 mediated by interleukin-8 autocrine signaling maintains the cancer stem cell phenotype in liver cancer.

BACKGROUND AND AIM: Liver cancer stem cells (LCSCs) cause therapeutic refractoriness and relapse in hepatocellular carcinoma. Heat shock factor 1 (HSF1) plays versatile roles in multiple cancers. However, the role of HSF1 in LCSCs is not well understood. This study investigated the function and signal mechanisms of HSF1 in maintaining LCSC phenotypes. METHODS: We established two LCSC lines, HepG2-R and HuH-7-R. Constitutive activation of HSF1 was observed in these LCSCs. Specific short hairpin RNAs (shRNAs) and chemical inhibitors were used to identify the relationship between HSF1 expression and LCSCs phenotypes. RESULTS: We revealed a concomitant activation modality involving HSF1 and STAT3 in LCSCs and liver cancer tissues. We also found that liver cancer patients whose HSF1 and STAT3 mRNA expression levels were high presented with unfavorable clinicopathological characteristics. Moreover, the secretion of interleukin-8 (IL-8) was elevated in the LCSC medium and was directly regulated by HSF1 at the transcriptional level. In turn, IL-8 activated HSF1 and STAT3 signaling, and a neutralizing IL-8 antibody inhibited HSF1 and STAT3 activity, reduced cancer stem cell marker expression, and decreased LCSC microsphere formation. Simultaneous intervention with HSF1 and STAT3 led to synergistically suppressed stemness acquisition and growth suppression in the LCSCs in vivo and in vitro. CONCLUSIONS: Our study indicates that IL-8 mediates the crosstalk between the HSF1 and Stat3 signaling pathways in LCSCs and that the combined targeting of HSF1 and STAT3 is a promising treatment strategy for patients with advanced liver cancer.

Targeting key proteins involved in transcriptional regulation for cancer therapy: Current strategies and future prospective.

The key proteins involved in transcriptional regulation play convergent roles in cellular homeostasis, and their dysfunction mediates aberrant gene expressions that underline the hallmarks of tumorigenesis. As tumor progression is dependent on such abnormal regulation of transcription, it is important to discover novel chemical entities as antitumor drugs that target key tumor-associated proteins involved in transcriptional regulation. Despite most key proteins (especially transcription factors) involved in transcriptional regulation are historically recognized as undruggable targets, multiple targeting approaches at diverse levels of transcriptional regulation, such as epigenetic intervention, inhibition of DNA-binding of transcriptional factors, and inhibition of the protein-protein interactions (PPIs), have been established in preclinically or clinically studies. In addition, several new approaches have recently been described, such as targeting proteasomal degradation and eliciting synthetic lethality. This review will emphasize on accentuating these developing therapeutic approaches and provide a thorough conspectus of the drug development to target key proteins involved in transcriptional regulation and their impact on future oncotherapy.

Discovery of Unique Bis-Substituted Aromatic Amide Derivatives as Novel Highly Potent Antibiotics for Combating Methicillin-Resistant Staphylococcus aureus (MRSA).

Due to the increasing antibiotic resistance, developing novel antimicrobials to fight infections caused by resistant bacteria is imperative. Herein, a series of novel bis-substituted aromatic amides were designed and synthesized through modifying the hit compound 1, and their antimicrobial activities were evaluated. Among them, compound 4t, as the most potent lead, exhibited excellent antimicrobial activities against Gram-positive bacteria, including clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates, while keeping weak hemolytic and mammalian cytotoxic activities. Furthermore, compound 4t displayed rapid bactericidal capabilities, low tendency to produce resistance, and favorable capacities to destroy bacterial biofilms. Further explorations indicated that compound 4t induces bacterial death by binding to cardiolipin (CL) on the bacterial membrane, disrupting the cell membrane, and facilitating the accumulation of reactive oxygen species (ROS). Additionally, compound 4t showed remarkable anti-MRSA activity in vivo, demonstrating compound 4t could be developed as a potential candidate to combat MRSA infections.

Selectively targeting BCL6 using a small molecule inhibitor is a potential therapeutic strategy for ovarian cancer.

Ovarian cancer is one of the tumors with the highest fatality rate among gynecological tumors. The current 5-year survival rate of ovarian cancer is <35%. Therefore, more novel alternative strategies and drugs are needed to treat ovarian cancer. The transcription factor B-cell lymphoma 6 (BCL6) is critically associated with poor prognosis and cisplatin resistance in ovarian cancer treatment. Therefore, BCL6 may be an attractive therapeutic target for ovarian cancer. However, the role of targeting BCL6 in ovarian cancer remains elusive. Here, we developed a novel BCL6 small molecule inhibitor, WK369, which exhibits excellent anti-ovarian cancer bioactivity, induces cell cycle arrest and causes apoptosis. WK369 effectively inhibits the growth and metastasis of ovarian cancer without obvious toxicity in vitro and in vivo. meanwhile, WK369 can prolong the survival of ovarian cancer-bearing mice. It is worth noting that WK369 also has significant anti-tumor effects on cisplatin-resistant ovarian cancer cell lines. Mechanistic studies have shown that WK369 can directly bind to the BCL6-BTB domain and block the interaction between BCL6 and SMRT, leading to the reactivation of p53, ATR and CDKN1A. BCL6-AKT, BCL6-MEK/ERK crosstalk is suppressed. As a first attempt, our study demonstrates that targeting BCL6 may be an effective approach to treat ovarian cancer and that WK369 has the potential to be used as a candidate therapeutic agent for ovarian cancer.

Recent advances in small molecule and peptide inhibitors of glucose-regulated protein 78 for cancer therapy.

Glucose-regulated protein 78 (GRP78) is one of key endoplasmic reticulum (ER) chaperone proteins that regulates the unfolded protein response (UPR) to maintain ER homeostasis. As a core factor in the regulation of the UPR, GRP78 takes a critical part in the cellular processes required for tumorigenesis, such as proliferation, metastasis, anti-apoptosis, immune escape and chemoresistance. Overexpression of GRP78 is closely correlated with tumorigenesis and poor prognosis in various malignant tumors. Targeting GRP78 is regarded as a potentially promising therapeutic strategy for cancer therapy. Although none of the GRP78 inhibitors have been approved to date, there have been several studies of GRP78 inhibitors. Herein, we comprehensively review the structure, physiological functions of GRP78 and the recent progress of GRP78 inhibitors, and discuss the structures, in vitro and in vivo efficacies, and merits and demerits of these inhibitors to inspire further research. Additionally, the feasibility of GRP78-targeting proteolysis-targeting chimeras (PROTACs), disrupting GRP78 cochaperone interactions, or covalent inhibition are also discussed as novel strategies for drugs discovery targeting GRP78, with the hope that these strategies can provide new opportunities for targeted GRP78 antitumor therapy.

A small molecule BCL6 inhibitor as chemosensitizers in acute myeloid leukemia.

BCL6 is a transcriptional repressor that regulates multiple genes involved in immune cell differentiation, DNA damage repair, cell cycle, and apoptosis, and is a carcinogenic factor in acute myeloid leukemia (AML). AML is one of the four major types of leukemia with the 5-year survival rate of patients is less than 20% and chemotherapy resistance remains the major obstacle to the treatment failure of AML. We identified WK499, a small molecule compound that can bind to BCL6BTB structure. Treatment with WK499 hinders the interactions between BCL6 with its corepressor proteins, resulting in a remarkable change of BCL6 downstream genes and anti-proliferative effects in AML cells, and inducing cell cycle arrest and apoptosis. We verified that AraC and DOXo could induce BCL6 expression in AML cells, and found that WK499 had a synergistic effect when combined with chemotherapeutic drugs. We further proved that WK499 and AraC could achieve a better result of inhibiting the growth of AML in vivo. These findings indicate that WK499, a small molecule inhibitor of BCL6, not only inhibits the proliferation of AML, but also provides an effective therapeutic strategy for increasing AML sensitivity to chemotherapy.

B-cell Lymphoma 6 Inhibitors: Current Advances and Prospects of Drug Development for Diffuse Large B-cell Lymphomas.

B-cell lymphoma 6 (BCL6) is a transcriptional repressor that regulates the differentiation of B lymphocytes and mediates the formation of germinal centers (GCs) by recruiting corepressors through the BTB domain of BCL6. Physiological processes regulated by BCL6 involve cell activation, differentiation, DNA damage, and apoptosis. BCL6 is highly expressed when the gene is mutated, leading to the malignant proliferation of cells and drives tumorigenesis. BCL6 overexpression is closely correlated with tumorigenesis in diffuse large B-cell lymphoma (DLBCL) and other lymphomas, and BCL6 inhibitors can effectively inhibit some lymphomas and overcome resistance. Therefore, targeting BCL6 might be a promising therapeutic strategy for treating lymphomas. Herein, we comprehensively review the latest development of BCL6 inhibitors in diffuse large B-cell lymphoma and discuss the overview of the pharmacophores of BCL6 inhibitors and their efficacies in vitro and in vivo. Additionally, the current advances in BCL6 degraders are provided.

An orally available small molecule BCL6 inhibitor effectively suppresses diffuse large B cell lymphoma cells growth in vitro and in vivo.

The transcription factor B cell lymphoma 6 (BCL6) is an oncogenic driver of diffuse large B cell lymphoma (DLBCL) and mediates lymphomagenesis through transcriptional repression of its target genes by recruiting corepressors to its N-terminal broad-complex/tramtrack/bric-a-brac (BTB) domain. Blocking the protein-protein interactions of BCL6 and its corepressors has been proposed as an effective approach for the treatment of DLBCL. However, BCL6 inhibitors with excellent drug-like properties are rare. Hence, the development of BCL6 inhibitors is worth pursuing. We screened our internal chemical library by luciferase reporter assay and Homogenous Time Resolved Fluorescence (HTRF) assay and a small molecule compound named WK500B was identified. WK500B engaged BCL6 inside cells, blocked BCL6 repression complexes, reactivated BCL6 target genes, killed DLBCL cells and caused apoptosis as well as cell cycle arrest. In animal models, WK500B inhibited germinal center (GC) formation and DLBCL tumour growth without toxic and side effects. Moreover, WK500B displayed strong efficacy and favourable pharmacokinetics and presented superior druggability. Therefore, WK500B is a promising candidate that could be developed as an effective orally available therapeutic agent for DLBCL.

Biotin attenuates heat shock factor 4b transcriptional activity by lysine 444 biotinylation.

Genetic mutations in HSF4 cause congenital cataracts. HSF4 exhibits both positive and negative regulation on the transcription of heat shock and non-heat shock proteins during lens development, and its activity is regulated by posttranslational modifications. Biotin is an essential vitamin that regulates gene expression through protein biotinylation. In this paper, we report that HSF4b is negatively regulated by biotinylation. Administration of biotin or ectopic bacterial biotin ligase BirA increases HSF4b biotinylation at its C-terminal amino acids from 196 to 493. This attenuates the HSF4b-controlled expression of αB-crystallin in both lens epithelial cells and tested HEK293T cells. HSF4b interacts with holocarboxylase synthetase (HCS), a ubiquitous enzyme for catalyzing protein biotinylation in mammal. Ectopic HA-HCS expression downregulates HSF4b-controlled αB-crystallin expression. Lysine-mutation analyses indicate that HSF4b/K444 is a potential biotinylation site. Mutation K444R reduces the co-precipitation of HSF4b by streptavidin beads and biotin-induced reduction of αB-crystallin expression. Mutations of other lysine residues such as K207R/K209R, K225R, K288R, K294R and K355R in HSF4's C-terminal region do not affect HSF4's expression level and the interaction with streptavidin, but they exhibit distinct regulation on αB-crystallin expression through different mechanisms. HSF4/K294R leads to upregulation of αB-crystallin expression, while mutations K207R/K209R, K225R, K288R, K255R and K435R attenuate HSF4's regulation on αB-crystallin expression. K207R/K209R blocks HSF4 nuclear translocation, and K345R causes HSF4 destabilization. Taken together, the data reveal that biotin maybe a novel factor in modulating HSF4 activity through biotinylation.

Design, synthesis and evaluation of phenylthiazole and phenylthiophene pyrimidindiamine derivatives targeting the bacterial membrane.

As the continuous rise in the incidence of antibiotic resistance, it is urgent to develop novel chemical scaffolds with antibacterial activities to control the spread of resistance to conventional antibiotics. In this study, a series of phenylthiazole and phenylthiophene pyrimidindiamine derivatives were designed and synthesized by modifying the hit compound (N2-isobutyl-N4-((4-methyl-2-phenylthiazol-5-yl)methyl) pyrimidine-2,4-diamine) and their antibacterial activities were evaluated both in vitro and in vivo. Among the tested compounds, compound 14g (N4-((5-(3-bromophenyl)thiophen-2-yl)methyl)-N2-isobutylpyrimidine-2,4-diamine) displayed the best antibacterial activities, which was not only capable of inhibiting E. coli and S. aureus growth at concentrations as low as 2 and 3 µg/mL in vitro, but also efficacious in a mice model of bacteremia in vivo. Unlike conventional antibiotics, compound 14g was elucidated to mainly destroy the bacterial cell membrane, with the dissipation of membrane potential and leakage of contents, ultimately leading to cell death. The destruction of cell structure is challenging to induce bacterial resistance, which suggested that compound 14g may be a kind of promising alternatives to antibiotics against bacteria.

Targeting Pyruvate Carboxylase by a Small Molecule Suppresses Breast Cancer Progression.

Rapid metabolism differentiates cancer cells from normal cells and relies on anaplerotic pathways. However, the mechanisms of anaplerosis-associated enzymes are rarely understood. The lack of potent and selective antimetabolism drugs restrains further clinical investigations. A small molecule ZY-444 ((N 4-((5-(4-(benzyloxy)phenyl)-2-thiophenyl)methyl)-N 2-isobutyl-2,4-pyrimidinediamine) is discovered to inhibit cancer cell proliferation specifically, having potent efficacies against tumor growth, metastasis, and recurrence. ZY-444 binds to cellular pyruvate carboxylase (PC), a key anaplerotic enzyme of the tricarboxylic acid cycle, and inactivates its catalytic activity. PC inhibition suppresses breast cancer growth and metastasis through inhibiting the Wnt/ß-catenin/Snail signaling pathway. Lower PC expression in patient tumors is correlated with significant survival benefits. Comparative profiles of PC expression in cancer versus normal tissues implicate the tumor selectivity of ZY-444. Overall, ZY-444 holds promise therapeutically as an anti-cancer metabolism agent.

Synthesis and Biological Evaluation of B-Cell Lymphoma 6 Inhibitors of N-Phenyl-4-pyrimidinamine Derivatives Bearing Potent Activities against Tumor Growth.

The transcriptional repressor B-cell lymphoma 6 (BCL6) is frequently misregulated in diffuse large B-cell lymphoma (DLBCL) and has emerged as an attractive drug target for the treatments of lymphoma. In this article, a series of N-phenyl-4-pyrimidinamine derivatives were designed and synthesized as potent BCL6 inhibitors by optimizing hit compound N4-(3-chloro-4-methoxyphenyl)-N2-isobutyl-5-fluoro-2,4-pyrimidinediamine on the basis of the structure-activity relationship. Among them, compound 14j displayed the most potent activities, which significantly blocked the interaction of BCL6 with its corepressors, reactivated BCL6 target genes in a dose-dependent manner, and had better effects compared with the two positive controls. Further studies indicated that a low dose of 14j could effectively inhibit germinal center formation. More importantly, 14j not only showed potent inhibition of DLBCL cell proliferation in vitro but also strongly suppressed the growth of DLBCL in vivo.

Modification and Biological Evaluation of a Series of 1,5-Diaryl-1,2,4-triazole Compounds as Novel Agents against Pancreatic Cancer Metastasis through Targeting Myoferlin.

Pancreatic cancer is one of the most common cancers with an extremely low survival rate. Metastasis, as one of the key reasons of cancer-related death, is found in more than 50% pancreatic cancer patients at diagnosis. Novel therapeutic targets and drugs blocking cancer metastasis are urgently needed. Herein, we report a series of 1,5-diaryl-1,2,4-triazole derivatives as potent antimetastatic agents. Lead compound 6y displayed effective antimetastatic activities in pancreatic cancer in vitro and in vivo. Concomitant studies indicated that 6y probably binds with myoferlin (MYOF), a novel potential antitumor metastasis target, which regulates vesicle trafficking and metastasis-related proteins. Subsequent biophysical and biochemical methods verified that 6y bound to MYOF. Mechanism studies revealed that 6y inhibited pancreatic cancer metastasis through reversing the epithelial mesenchymal transition, inhibiting the secretions of matrix metalloproteinase and blocking the receptor tyrosine kinases. Our findings suggest that targeting MYOF with 6y may be a promising therapeutic strategy to prevent pancreatic cancer metastasis.

Design, synthesis and evaluation of hybrid of tetrahydrocarbazole with 2,4-diaminopyrimidine scaffold as antibacterial agents.

Several 6-substituted tetrahydrocarbazole derivatives were designed, synthesized and evaluated for the antibacterial activities against Staphylococcus aureus Newman strain. Subsequently, 2,4-diaminopyrimidine scaffold was merged with the tetrahydrocarbazole unit to generate a series of novel hybrid derivatives and the antibacterial activities were also investigated. Among these novel hybrids, compound 12c showed the most potent activity with a MIC of 0.39-0.78 µg/mL against S. aureus Newman and Escherichia coli AB1157 strain. In addition, compound 12c exhibited low MIC values against a panel of multidrug-resistant strains of S. aureus.

Design and optimization of hybrid of 2,4-diaminopyrimidine and arylthiazole scaffold as anticancer cell proliferation and migration agents.

Therapeutics of metastatic or triple-negative breast cancer are still challenging in clinical. Herein we demonstrated the design and optimization of a series of hybrid of 2,4-diaminopyrimidine and arylthiazole derivatives for their anti-proliferative properties against two breast cancer cell lines (MCF-7 as human breast cancer and MDA-MB-231 as triple-negative breast cancer). More importantly, some of those compounds with potent antiproliferative activities also indicated excellent inhibitory activities against MDA-MB-231 cell migration. These results suggested that the new series of hybridation of aryl-thiazoles and aminopyrimidines could be identified and developed as novel highly potential anticancer agents against the triple-negative breast cancer as well as metastatic one in the future.