Targeting DDX11 promotes PARP inhibitor sensitivity in hepatocellular carcinoma by attenuating BRCA2-RAD51 mediated homologous recombination.

Homologous recombination (HR) is a major DNA double-strand break (DSB) repair pathway of clinical interest because of treatment with poly(ADP-ribose) polymerase inhibitors (PARPi). Cooperation between RAD51 and BRCA2 is pivotal for DNA DSB repair, and its dysfunction induces HR deficiency and sensitizes cancer cells to PARPi. The depletion of the DEAD-box protein DDX11 was found to suppress HR in hepatocellular carcinoma (HCC) cells. The HR ability of HCC cells is not always dependent on the DDX11 level because of natural DDX11 mutations. In Huh7 cells, natural DDX11 mutations were detected, increasing the susceptibility of Huh7 cells to olaparib in vitro and in vivo. The HR deficiency of Huh7 cells was restored when CRISPR/Cas9-mediated knock-in genomic editing was used to revert the DDX11 Q238H mutation to wild type. The DDX11 Q238H mutation impeded the phosphorylation of DDX11 by ATM at serine 237, preventing the recruitment of RAD51 to damaged DNA sites by disrupting the interaction between RAD51 and BRCA2. Clinically, a high level of DDX11 correlated with advanced clinical characteristics and a poor prognosis and served as an independent risk factor for overall and disease-free survival in patients with HCC. We propose that HCC with a high level of wild-type DDX11 tends to be more resistant to PARPi because of enhanced recombination repair, and the key mutation of DDX11 (Q238H) is potentially exploitable.

HNF1A-Induced lncRNA HCG18 Facilitates Gastric Cancer Progression by Upregulating DNAJB12 via miR-152-3p.

BACKGROUND: The aberrant expression of long non-coding RNAs (lncRNAs) plays a pivotal role in the development and progression of multiple cancers, including gastric cancer (GC). However, the underlying molecular mechanisms of lncRNA HCG18 in GC remain unknown. MATERIALS AND METHODS: The expression levels of HCG18, HNF1A, microRNA-152-3p (miR-152-3p), and DNAJB12 were determined by RT-qPCR. Cell viability, migration, and invasion were assessed by CCK-8, wound healing, and transwell assays, respectively. The interaction between miR-152-3p and HCG18 or DNAJB12 was predicted by bioinformatics analysis and verified by dual-luciferase reporter assay. The correlation between the gene expression levels was analyzed using Pearson's correlation coefficient. Western blot was used to measure the levels of HNF1A, DNAJB12, epithelial-mesenchymal transition (EMT) proteins (E-cadherin and Vimentin), and proliferation-related protein (PCNA). RESULTS: It was found that HCG18 was upregulated in GC tissues and cell lines, and knockdown of HCG18 inhibited the proliferation, migration, and invasion of GC cells. Patients with high HCG18 expression had a shorter overall survival time compared with those with low HCG18 expression. In addition, transcription factor HNF1A could bind to the HCG18 promoter to facilitate its transcription. The upregulation of HCG18 could abolish the inhibitory effect of miR-152-3p overexpression on GC cell progression. Furthermore, DNAJB12 was demonstrated to be a target gene of miR-152-3p in GC cells, and HCG18 enhanced DNAJB12 expression by competitively binding with miR-152-3p. Finally, rescue assays proved that overexpression of DNAJB12 partially restored HCG18 knockdown-attenuated progression of GC cells. CONCLUSION: Our results demonstrated that HNF1A-induced HCG18 overexpression promoted GC progression by competitively binding with miR-152-3p and upregulating DNAJB12 expression. These findings might provide potential treatment strategies for patients with GC.

Derivatives of mesoxalic acid block translocation of HIV-1 reverse transcriptase.

The pyrophosphate mimic and broad spectrum antiviral phosphonoformic acid (PFA, foscarnet) was shown to freeze the pre-translocational state of the reverse transcriptase (RT) complex of the human immunodeficiency virus type 1 (HIV-1). However, PFA lacks a specificity domain, which is seen as a major reason for toxic side effects associated with the clinical use of this drug. Here, we studied the mechanism of inhibition of HIV-1 RT by the 4-chlorophenylhydrazone of mesoxalic acid (CPHM) and demonstrate that this compound also blocks RT translocation. Hot spots for inhibition with PFA or CPHM occur at template positions with a bias toward pre-translocation. Mutations at active site residue Asp-185 compromise binding of both compounds. Moreover, divalent metal ions are required for the formation of ternary complexes with either of the two compounds. However, CPHM contains both an anchor domain that likely interacts with the catalytic metal ions and a specificity domain. Thus, although the inhibitor binding sites may partly overlap, they are not identical. The K65R mutation in HIV-1 RT, which reduces affinity to PFA, increases affinity to CPHM. Details with respect to the binding sites of the two inhibitors are provided on the basis of mutagenesis studies, structure-activity relationship analyses with newly designed CPHM derivatives, and in silico docking experiments. Together, these findings validate the pre-translocated complex of HIV-1 RT as a specific target for the development of novel classes of RT inhibitors.

The identification of 4,7-disubstituted naphthoic acid derivatives as UDP-competitive antagonists of P2Y14.

A weak, UDP-competitive antagonist of the pyrimidinergic receptor P2RY(14) with a naphthoic acid core was identified through high-throughput screening. Optimization provided compounds with improved potency but poor pharmacokinetics. Acylglucuronidation was determined to be the major route of metabolism. Increasing the electron-withdrawing nature of the substituents markedly reduced glucuronidation and improved the pharmacokinetic profile. Additional optimization led to the identification of compound 38 which is an 8 nM UDP-competitive antagonist of P2Y(14) with a good pharmacokinetic profile.

Synthesis and SAR of pyrimidine-based, non-nucleotide P2Y14 receptor antagonists.

A weak antagonist of the pyrimidinergic receptor P2Y(14) containing a dihydropyridopyrimidine core was identified through high-throughput screening. Subsequent optimization led to potent, non-UTP competitive antagonists and represent the first reported non-nucleotide antagonists of this receptor. Compound 18q was identified as a 10 nM P2Y(14) antagonist with good oral bioavailability and provided sufficient exposure in mice to be used as a tool for future in vivo studies.

An activity-based probe for high-throughput measurements of triacylglycerol lipases.

Modulating the activity of lipases involved in the metabolism of plasma lipoproteins is an attractive approach for developing lipid raising/lowering therapies to treat cardiovascular disease. Identifying small molecule inhibitors for these membrane-active enzymes, however, is complicated by difficulties associated with measuring lipase activity and inhibition at the water-membrane interface; substrate and compound dynamics at the particle interface have the potential to confound data interpretation. Here, we describe a novel ELISA-based lipase activity assay that employs as "bait" a biotinylated active-site probe that irreversibly binds to the catalytic active-site serine of members of the triacylglycerol lipase family (hepatic lipase, lipoprotein lipase, and endothelial lipase) in solution with high affinity. Detection of "captured" (probe-enzyme) complexes on streptavidin-coated plates using labeled secondary antibodies to specific primary antibodies offers several advantages over conventional assays, including the ability to eliminate enzyme-particle and compound-particle effects; specifically measure lipase activity in complex mixtures in vitro; preferentially identify active-site-directed inhibitors; and distinguish between reversible and irreversible inhibitors through a simple assay modification. Using EL as an exemplar, we demonstrate the versatility of this assay both for high-throughput screening and for compound mechanism-of-action studies.

The identification of substituted benzothiophene derivatives as PGE(2) subtype 4 receptor antagonists: From acid to non-acid.

We disclose herein our preliminary SAR study on the identification of substituted benzothiophene derivatives as PGE(2) subtype 4 receptor antagonists. A potent EP(4) antagonist 6a (K(i)=1.4nM with 10% HSA) was identified. Furthermore, we found that an acidic group was not essential for the EP(4) antagonizing activity in the series and neutral replacements were identified. This opens a new direction for future EP(4) antagonist design.

Potent and selective 5-LO inhibitor bearing benzothiophene pharmacophore: discovery of MK-5286.

The strategy and SAR studies that led to the discovery of a novel potent and orally available 5-lipoxygenase (5-LO) inhibitor 3-(4-fluorophenyl)-6-({4-[(1S)-1-hydroxy-1-(trifluoromethyl)propyl]-1H-1,2,3-triazol-1-yl}methyl)-1-benzothiophene-2-carboxamide ((S)-2l or MK-5286) were described.

Potent and highly selective DP1 antagonists with 2,3,4,9-tetrahydro-1H-carbazole as pharmacophore.

We discovered that the introduction of a methyl group to the benzylic position of the N-benzyl group in lead compound 1a has a dramatic effect on improving the binding selectivity of this ligand for the prostanoid receptors DP1 (receptor for prostaglandin D(2)) as compared to TP (receptor for thromboxane A(2)). Based on this discovery, we have synthesized a series of potent and highly selective DP1 antagonists. Among them, compound 1h was identified as a highly selective DP1 antagonist with excellent overall properties. It has a K(i) of 0.43 nM to DP1 in binding assay and an IC(50) of 2.5 nM in the DP1 functional assay. Its selectivity for DP1 over TP (the most potent receptor after DP1) exceeds 750-fold based on both binding and functional assays. These properties make 1h a very potent and highly selective DP1 receptor antagonist suitable for investigating the biological functions of DP1 in normal physiology and models of disease.

Metabolic activation of indole-containing prostaglandin D2 receptor 1 antagonists: impacts of glutathione trapping and glucuronide conjugation on covalent binding.

Some DP1 receptor antagonists from an indole-containing series were shown to cause in vitro covalent binding to protein in rat and human liver microsomes. Glutathione trapping experiments along with in vitro labeling assays confirmed that the presence of a strong electron withdrawing group was necessary to abrogate in vitro covalent binding, leading to the discovery of MK-0524. Hepatocyte incubations and in vivo studies showed that acyl-glucuronide formation did not translate into covalent binding.

Discovery of a potent and selective prostaglandin D2 receptor antagonist, [(3R)-4-(4-chloro-benzyl)-7-fluoro-5-(methylsulfonyl)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl]-acetic acid (MK-0524).

The discovery of the potent and selective prostaglandin D2 (PGD2) receptor (DP) antagonist [(3R)-4-(4-chlorobenzyl)-7-fluoro-5-(methylsulfonyl)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl]-acetic acid (13) is presented. Initial lead antagonists 6 and 7 were found to be potent and selective DP antagonists (DP Ki = 2.0 nM for each); however, they both suffered from poor pharmacokinetic profiles, short half-lives and high clearance rates in rats. Rat bile duct cannulation studies revealed that high concentrations of parent drug were present in the biliary fluid (Cmax = 1100 microM for 6 and 3900 microM for 7). This pharmacokinetic liability was circumvented by replacing the 7-methylsulfone substituent present in 6 and 7 with a fluorine atom resulting in antagonists with diminished propensity for biliary excretion and with superior pharmacokinetic profiles. Further optimization led to the discovery of the potent and selective DP antagonist 13.

All-carbon-substituted vinylsilane stable to TBAF: synthesis of allyldimethylvinylsilane and its Pd-catalyzed cross-coupling under mild conditions.

[reaction: see text] Allyldimethylvinylsilanes 3 are easily synthesized by the reaction of silylallylmetals, generated from 1 by n-BuLi/t-BuOK, with carbonyl compounds in the absence or presence of metal halides. They can tolerate 2 equiv of TBAF in THF at room temperature for at least 6 h but can be easily activated in the presence of a palladium catalyst and TBAF to perform the cross-coupling reaction with aryl iodides at room temperature.

Identification of an indole series of prostaglandin D2 receptor antagonists.

A novel indole series of PGD2 receptor (DP receptor) antagonists is presented. Optimization of this series led to the identification of potent and selective DP receptor antagonists. In particular, antagonists 35 and 36 were identified with Ki values of 2.6 and 1.8 nM, respectively. These two antagonists are also potent in a DP functional assay where they inhibit the PGD2 induced cAMP production in platelet rich plasma with IC50 values of 7.9 and 8.6 nM, respectively. The structure-activity relationships of this indole series of DP receptor antagonists will also be discussed.

Green tea and tea polyphenols in cancer prevention.

The cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin gallate [(-)-EGCG] are widely supported by results from epidemiological, cell culture, animal and clinical studies in the recent decade. In vitro cell culture studies show that tea polyphenols potently induce apoptotic cell death and cell cycle arrest in tumor cells but not in their normal cell counterparts. Green tea polyphenols affect several signal transduction pathways, including growth factor-mediated, the mitogen-activated protein kinase (MAPK)-dependent, and ubiquitin/proteasome degradation pathways. Epidemiological studies have suggested that the consumption of green tea lowers the risk of cancer. Various animal studies have revealed that treatment by green tea inhibits tumor incidence and multiplicity in different organ sites such as skin, lung, liver, stomach, mammary gland and colon. Phase I and II clinical trials were carried out recently to explore the anticancer effects of green tea in patients with cancer. At this time, more mechanistic research, animal studies, and clinical trials are necessary to further evaluate the role of green tea in cancer prevention.

One-pot, three-component synthesis of linearly substituted homoallylic alcohols via allyl(isopropoxy)dimethylsilane.

[reaction: see text] A two-step approach that involves the synthesis of vinylsilane from allyl(isopropoxy)dimethylsilane (6) and the subsequent Pd-catalyzed cross-coupling of the resulting vinylsilane is applied in developing a novel diversity-oriented, three-component synthesis to homoallylic alcohols of common structure 1. Upon treatment of 6 with s-BuLi, the silylallylmetal 5 is generated and reacted with carbonyl compounds to produce functionalized vinylsilanes, which can couple with aryl/vinyl halides in the presence of palladium catalyst to afford 1.

Synthetic analogs of green tea polyphenols as proteasome inhibitors.

BACKGROUND: Animal, epidemiological and clinical studies have demonstrated the anti-tumor activity of pharmacological proteasome inhibitors and the cancer-preventive effects of green tea consumption. Previously, one of our laboratories reported that natural ester bond-containing green tea polyphenols (GTPs), such as (-)-epigallocatechin-3-gallate [(-)-EGCG] and (-)-gallocatechin-3-gallate [(-)-GCG], are potent and specific proteasome inhibitors. Another of our groups, for the first time, was able to enantioselectively synthesize (-)-EGCG as well as other analogs of this natural GTP. Our interest in designing and developing novel synthetic GTPs as proteasome inhibitors and potential cancer-preventive agents prompted our current study. MATERIALS AND METHODS: GTP analogs, (+)-EGCG, (+)-GCG, and a fully benzyl-protected (+)-EGCG [Bn-(+)-EGCG], were prepared by enantioselective synthesis. Inhibition of the proteasome or calpain (as a control) activities under cell-free conditions were measured by fluorogenic substrate assay. Inhibition of intact tumor cell proteasome activity was measured by accumulation of some proteasome target proteins (p27, I kappa B-alpha and Bax) using Western blot analysis. Inhibition of tumor cell proliferation and induction of apoptosis by synthetic GTPs were determined by G(1) arrest and caspase activation, respectively. Finally, inhibition of the transforming activity of human prostate cancer cells by synthetic GTPs was measured by a colony formation assay. RESULTS: (+)-EGCG and (+)-GCG potently and specifically inhibit the chymotrypsin-like activity of purified 20S proteasome and the 26S proteasome in tumor cell lysates, while Bn-(+)-EGCG does not. Treatment of leukemic Jurkat T or prostate cancer LNCaP cells with either (+)-EGCG or (+)-GCG accumulated p27 and IkappaB-alpha proteins, associated with an increased G(1) population. (+)-EGCG treatment also accumulated the pro-apoptotic Bax protein and induced apoptosis in LNCaP cells expressing high basal levels of Bax, but not prostate cancer DU-145 cells with low Bax expression. Finally, synthetic GTPs significantly inhibited colony formation by LNCaP cancer cells. CONCLUSIONS: Enantiomeric analogs of natural GTPs, (+)-EGCG and (+)-GCG, are able to potently and specifically inhibit the proteasome both, in vitro and in vivo, while protection of the hydroxyl groups on (+)-EGCG renders the compound completely inactive.

Stereospecific synthesis of cryptophycin 1.

[reaction: see text] A brief stereospecific synthesis of cryptophycin 1 is described in which (R)-mandelic acid serves as the sole source of asymmetry for unit A. The key step is a hetero-Diels-Alder cycloaddition.