Redox cycling compounds (RCCs) generate µM concentrations of hydrogen peroxide (H2O2) in the presence of strong reducing agents, common buffer components used to maintain the catalytic activity and/or folding of target proteins for high throughput screening (HTS) assays. H2O2 generated by RCCs can indirectly inhibit the catalytic activity of proteins by oxidizing accessible cysteine, tryptophan, methionine, histidine or selenocysteine residues, and indeed several important classes of protein targets are susceptible to H2O2-mediated inactivation; protein tyrosine phosphatases, cysteine proteases, and metalloenzymes. The main sources of H2O2 in cells are the Nox enzyme/SOD systems, peroxisome metabolism, and the autoxidation of reactive chemicals by enzyme mediated redox cycling at both the microsomal and mitochondrial sites of electron transport. Given the role of H2O2 as a second messenger involved in the regulation of many signaling pathways it is hardly surprising that compounds which can generate intracellular H2O2 by enzyme mediated redox cycling would have pleiotropic effects. RCCs can therefore have serious negative consequences for the probe and/or lead generation process: primary HTS assay hit rates may be inflated by RCC false positives; critical resources will be diverted to develop and implement follow up assays to distinguish RCCs from real hits; and screening databases will become annotated with the promiscuous activity of RCCs. In an attempt to mitigate the serious impact of RCCs on probe and lead generation, two groups have independently developed assays to indentify RCCs.
Quinones are widely distributed compounds in nature. Of these, ortho-quinones are found to be involved in the pathogenic mechanism of Parkinson’s disease, in oxidative deaminations to free-radical redox reactions, and as intermediates in the pathways implicated in the carcinogenicity of 2,3- and 3,4-catechol estrogens. Addition of MgCl2 to solutions of the hydrophobic ortho-quinones, 1,10-phenanthroquinone (PHQ) and beta-lapachone (LQ) enhances ascorbate oxidation in the absence or presence of large unilamellar vesicles (LUVs) of the neutral lipid dimyristoylphos-phatidylcholine (DMPC), although initial rates of ascorbate oxidation are smaller in the presence of lipid as compared to its absence. Addition of this salt to solutions of the para-quinone 1,4-naphthoquinone (NQ) did not affect the ascorbate rate of oxidation in the absence or presence of DMPC. Addition of MgCl2 to semiquinone solutions of PHQ or LQ in the presence or absence of DMPC increases semiquinone stability, as detected from the semiquinone disproportionation equilibrium displacement to semiquinone formation. Furthermore, MgCl2 increases the partition of the ortho-semiquinones into the aqueous phase, although no such effect is observed for the semiquinone of NQ. For all the quinones under study, smaller rates of ascorbate oxidation and of semiquinone equilibrium concentration occur in the presence of negatively charged LUVs composed of an equimolar mixture of DMPC and dimyristoylphosphatidic acid DMPA. Ascorbate oxidation rate enhancements correlate with an increase in semiquinone concentration with addition of MgCl2, in the absence or presence of neutral lipid. This observation favors the proposition that ascorbate oxidation rate increases are caused by semiquinone thermodynamic stabilization. Thus, the ascorbate oxidation rate enhancement by MgCl2 in solutions containing hydrophobic ortho-quinones is still possible in systems with hydrophobic environments analogous to that of DMPC.
Ortho-quinone; semiquinone; magnesium; DMPC; membrane; ascorbate; DMPA; beta-lapachone; phenanthroquinone; naphthoquinone
We report here the development and optimization of a simple 384-well colorimetric assay to measure H2O2 generated by the redox cycling of compounds incubated with reducing agents in high-throughput screening (HTS) assay buffers. The phenol red-horseradish peroxidase (HRP) assay readily detected H2O2 either added exogenously or generated by the redox cycling of compounds in dithiothreitol (DTT). The generation of H2O2 was dependent on the concentration of both the compound and DTT and was abolished by catalase. Although both DTT and tris(2-carboxyethyl)-phosphine sustain the redox cycling generation of H2O2 by a model quinolinedione, 6-chloro-7-(2-morpholin-4-yl-ethylamino)-quinoline-5,8-dione (NSC 663284; DA3003-1), other reducing agents such as β-mercaptoethanol, glutathione, and cysteine do not. The assay is compatible with HTS. Once terminated, the assay signal was stable for at least 5 h, allowing for a reasonable throughput. The assay tolerated up to 20% dimethyl sulfoxide, allowing a wide range of compound concentrations to be tested. The assay signal window was robust and reproducible with average Z-factors of ≥0.8, and the redox cycling generation of H2O2 by DA3003-1 in DTT exhibited an average 50% effective concentration of 0.830 ± 0.068 μM. Five of the mitogen-activated protein kinase phosphatase (MKP) 1 inhibitors identified in an HTS were shown to generate H2O2 in the presence of DTT, and their inhibition of MKP-1 activity was shown to be time dependent and was abolished or significantly reduced by either 100 U of catalase or by higher DTT levels. A cross-target query of the PubChem database with three structurally related pyrimidotriazinediones revealed active flags in 36–39% of the primary screening assays. Activity was confirmed against a number of targets containing active site cysteines, including protein tyrosine phosphatases, cathepsins, and caspases, as well as a number of cellular cytotoxicity assays. Rather than utilize resources to conduct a hit characterization effort involving several secondary assays, the phenol red-HRP assay provides a simple, rapid, sensitive, and inexpensive method to identify compounds that redox cycle in DTT or tris(2-carboxyethyl)phosphine to produce H2O2 that may indirectly modulate target activity and represent promiscuous false-positives from a primary screen.
We report here the development and optimization of a simple 384-well colorimetric assay to measure H2O2 generated by the redox cycling of compounds incubated with reducing agents in high-throughput screening (HTS) assay buffers. The phenol red-horseradish peroxidase (HRP) assay readily detected H2O2 either added exogenously or generated by the redox cycling of compounds in dithiothreitol (DTT). The generation of H2O2 was dependent on the concentration of both the compound and DTT and was abolished by catalase. Although both DTT and tris(2-carboxyethyl)-phosphine sustain the redox cycling generation of H2O2 by a model quinolinedione, 6-chloro-7-(2-morpholin-4-yl-ethylamino)-quinoline-5,8-dione (NSC 663284; DA3003-1), other reducing agents such as β-mercaptoethanol, glutathione, and cysteine do not. The assay is compatible with HTS. Once terminated, the assay signal was stable for at least 5 h, allowing for a reasonable throughput. The assay tolerated up to 20% dimethyl sulfoxide, allowing a wide range of compound concentrations to be tested. The assay signal window was robust and reproducible with average Z-factors of ≥0.8, and the redox cycling generation of H2O2 by DA3003-1 in DTT exhibited an average 50% effective concentration of 0.830 μ 0.068 μM. Five of the mitogen-activated protein kinase phosphatase (MKP) 1 inhibitors identified in an HTS were shown to generate H2O2 in the presence of DTT, and their inhibition of MKP-1 activity was shown to be time dependent and was abolished or significantly reduced by either 100 U of catalase or by higher DTT levels. A cross-target query of the PubChem database with three structurally related pyrimidotriazinediones revealed active flags in 36–39% of the primary screening assays. Activity was confirmed against a number of targets containing active site cysteines, including protein tyrosine phosphatases, cathepsins, and caspases, as well as a number of cellular cytotoxicity assays. Rather than utilize resources to conduct a hit characterization effort involving several secondary assays, the phenol red-HRP assay provides a simple, rapid, sensitive, and inexpensive method to identify compounds that redox cycle in DTT or tris(2-carboxyethyl)phosphine to produce H2O2 that may indirectly modulate target activity and represent promiscuous false-positives from a primary screen.
With the advent of second-generation sequencing, the expression of gene transcripts can be digitally measured with high accuracy. The purpose of this study was to systematically profile the expression of both mRNA and miRNA genes in clear cell renal cell carcinoma (ccRCC) using massively parallel sequencing technology.
The expression of mRNAs and miRNAs were analyzed in tumor tissues and matched normal adjacent tissues obtained from 10 ccRCC patients without distant metastases. In a prevalence screen, some of the most interesting results were validated in a large cohort of ccRCC patients.
A total of 404 miRNAs and 9,799 mRNAs were detected to be differentially expressed in the 10 ccRCC patients. We also identified 56 novel miRNA candidates in at least two samples. In addition to confirming that canonical cancer genes and miRNAs (including VEGFA, DUSP9 and ERBB4; miR-210, miR-184 and miR-206) play pivotal roles in ccRCC development, promising novel candidates (such as PNCK and miR-122) without previous annotation in ccRCC carcinogenesis were also discovered in this study. Pathways controlling cell fates (e.g., cell cycle and apoptosis pathways) and cell communication (e.g., focal adhesion and ECM-receptor interaction) were found to be significantly more likely to be disrupted in ccRCC. Additionally, the results of the prevalence screen revealed that the expression of a miRNA gene cluster located on Xq27.3 was consistently downregulated in at least 76.7% of ∼50 ccRCC patients.
Our study provided a two-dimensional map of the mRNA and miRNA expression profiles of ccRCC using deep sequencing technology. Our results indicate that the phenotypic status of ccRCC is characterized by a loss of normal renal function, downregulation of metabolic genes, and upregulation of many signal transduction genes in key pathways. Furthermore, it can be concluded that downregulation of miRNA genes clustered on Xq27.3 is associated with ccRCC.
Renal cell carcinoma (RCC) is the most common cancer arising from the kidney in adults, with clear cell carcinoma (ccRCC) representing the majority of all RCCs. Expression of a human HIF1a triple mutant (P402A, P564A and N803A) construct in the proximal tubule cells of C57BL/6 mice (TRAnsgenic model of Cancer of the Kidney (TRACK) (1)) mimics the histological changes found in early stage human ccRCC. To better understand the genomic landscape, a high throughput sequence analysis was performed with cDNA libraries (RNAseq) derived from TRACK transgenic positive (TG+) kidney cortex along with human ccRCC transcripts from the Oncomine and TCGA databases. Importantly, the expression profiles of TRACK TG+ kidneys show significant similarities with those observed in human ccRCC, including increased expression of genes involved in glycolysis and the tricarboxylic acid cycle (TCA cycle). Some of the transcripts overexpressed in both the TRACK mouse model and human ccRCC include: ANKRD37, CA9, EGLN3, HK2, NDUFA4L2, and SLC16A3. These data suggest that constitutive activation of HIF1a in kidney proximal tubule cells transcriptionally re-programs the regulation of metabolic pathways in the kidney and that HIF1a is a major contributor to the altered metabolism observed in human ccRCC.
TRACK (GGT-HIF1αM3) kidney mRNA profiles show similarities to human ccRCC transcriptome and phenotypes associated with the Warburg effect.
clear cell renal cell carcinoma; kidney cancer; RNAseq; HIF1α
Ortho-quinones formed from catechol estrogens are considered prooxidants due to the production of superoxide radical anions through redox cycling via semiquinones. Para-quinols have been identified as novel metabolites of and as the major products of hydroxyl-radical scavenging by estrogens. Cycling of these compounds has also been discovered, because they are converted back to the parent estrogen via reductive aromatization in vitro and in vivo. We hypothesized that, unlike ortho-quinones, para-quinols do not induce oxidative stress due to this cycling. Like the estrogen itself, the 17β-estradiol-derived para-quinol (10β,17β-dihydroxyestra-1,4-diene-3-one) did not induce oxidative stress, as the rate of hydrogen peroxide production during the incubations of the compounds in various tissue homogenates was not significantly different from that of the control experiments performed without the addition of a test compound. We also confirmed that the estrogen metabolite estra-1,5(10)-dien-3,4,17-trione (estrone 3,4-quinone) was a profound prooxidant due to redox cycling, especially in uterine tissue. Therefore, we concluded that para-quinols do not induce oxidative stress.
Renal cell carcinoma (RCC) is the sixth leading cause of cancer death and is responsible for 11,000 deaths per year in the US. Approximately one-third of patients present with disease which is already metastatic and for which there is currently no adequate treatment, and no biofluid screening tests exist for RCC. In this study, we have undertaken a comprehensive proteomic analysis and subsequently a pathway and network approach to identify biological processes involved in clear cell RCC (ccRCC). We have used these data to investigate urinary markers of RCC which could be applied to high-risk patients, or to those being followed for recurrence, for early diagnosis and treatment, thereby substantially reducing mortality of this disease.
Using 2-dimensional electrophoresis and mass spectrometric analysis, we identified 31 proteins which were differentially expressed with a high degree of significance in ccRCC as compared to adjacent non-malignant tissue, and we confirmed some of these by immunoblotting, immunohistochemistry, and comparison to published transcriptomic data. When evaluated by several pathway and biological process analysis programs, these proteins are demonstrated to be involved with a high degree of confidence (p values < 2.0 E-05) in glycolysis, propanoate metabolism, pyruvate metabolism, urea cycle and arginine/proline metabolism, as well as in the non-metabolic p53 and FAS pathways. In a pilot study using random urine samples from both ccRCC and control patients, we performed metabolic profiling and found that only sorbitol, a component of an alternative glycolysis pathway, is significantly elevated at 5.4-fold in RCC patients as compared to controls.
Extensive pathway and network analysis allowed for the discovery of highly significant pathways from a set of clear cell RCC samples. Knowledge of activation of these processes will lead to novel assays identifying their proteomic and/or metabolomic signatures in biofluids of patient at high risk for this disease; we provide pilot data for such a urinary bioassay. Furthermore, we demonstrate how the knowledge of networks, processes, and pathways altered in kidney cancer may be used to influence the choice of optimal therapy.
Activation of the Kelch-like ECH-associated protein 1/nuclear factor (erythroid-derived 2)-like 2 and heat-shock protein 90/heat-shock factor-1 signal-transduction pathways plays a central role in combatting cellular oxidative damage and related endoplasmic reticulum stress. Electrophilic compounds have been shown to be activators of these transcription-mediated responses through S-alkylation of specific regulatory proteins. Previously, we reported that a prototype compound (D1, a small molecule representing a proelectrophilic, para-hydroquinone species) exhibited neuroprotective action by activating both of these pathways. We hypothesized that the para-hydroquinone moiety was critical for this activation because it enhanced transcription of these neuroprotective pathways to a greater degree than that of the corresponding ortho-hydroquinone isomer. This notion was based on the differential oxidation potentials of the isomers for the transformation of the hydroquinone to the active, electrophilic quinone species. Here, to further test this hypothesis, we synthesized a pair of para- and ortho-hydroquinone-based proelectrophilic compounds and measured their redox potentials using analytical cyclic voltammetry. The redox potential was then compared with functional biological activity, and the para-hydroquinones demonstrated a superior neuroprotective profile.
Nrf2; HSF-1; heat-shock proteins; phase 2 antioxidant enzymes
Objective: The anti-neoplastic effects of decitabine, an inhibitor of DNA promoter methylation, are beneficial for the treatment of renal cell carcinoma (RCC); however, the mechanism of action of decitabine is unclear. We analyzed gene expression profiling and identified specific pathways altered by decitabine in RCC cells. Methods: Four human RCC cell lines (ACHN, Caki-1, Caki-1, and A498) were used in this study; growth suppression of RCC cells by decitabine was analyzed using the WST-1 assay. Apoptosis and cell cycle arrest were examined using flow cytometric analysis. Gene expression of RCC cells induced by decitabine was evaluated with cDNA microarray, and potential biological pathways were selected using Ingenuity Pathway Analysis. The activity of the p38-NF-κB pathway regulated by decitabine was confirmed by Western blotting. Results: Decitabine suppresses the proliferation of RCC cells in vitro. Although decitabine did not significantly induce apoptosis, decitabine caused cell cycle arrest at G2/M in a dose-dependent manner. Gene expression regulated by decitabine in RCC cells was investigated using microarray analysis. Ubiquitin carboxyl terminal hydrolase 1 (UCHL1), interferon inducible protein 27 (IFI27), and cell division cycle-associated 2 (CDCA2) may be involved in growth suppression of RCC cells by decitabine. The phosphorylation of p38-NF-κB pathway was suppressed by decitabine in RCC cells. Conclusions: We investigated gene expression profiling and pathways modulated by decitabine in RCC cells. Decitabine was shown to suppress the growth of RCC cells via G2/M cell cycle arrest and the p38-NF-κB signaling pathway may play a role in the anti-neoplastic effect of decitabine in RCC cells.
Renal cell carcinoma; decitabine; apoptosis; cell cycle arrest; gene expression; p38-NF-κB pathway
Recent evidence suggests that metabolic changes play a pivotal role in the biology of cancer and in particular renal cell carcinoma (RCC). Here, a global metabolite profiling approach was applied to characterize the metabolite pool of RCC and normal renal tissue. Advanced decision tree models were applied to characterize the metabolic signature of RCC and to explore features of metastasized tumours. The findings were validated in a second independent dataset. Vitamin E derivates and metabolites of glucose, fatty acid, and inositol phosphate metabolism determined the metabolic profile of RCC. α-tocopherol, hippuric acid, myoinositol, fructose-1-phosphate and glucose-1-phosphate contributed most to the tumour/normal discrimination and all showed pronounced concentration changes in RCC. The identified metabolic profile was characterized by a low recognition error of only 5% for tumour versus normal samples. Data on metastasized tumours suggested a key role for metabolic pathways involving arachidonic acid, free fatty acids, proline, uracil and the tricarboxylic acid cycle. These results illustrate the potential of mass spectroscopy based metabolomics in conjunction with sophisticated data analysis methods to uncover the metabolic phenotype of cancer. Differentially regulated metabolites, such as vitamin E compounds, hippuric acid and myoinositol, provide leads for the characterization of novel pathways in RCC.
kidney cancer; metabolism; metabolomics; metastasis
Malaria is a global health problem that causes significant mortality and morbidity, with more than 1 million deaths per year caused by Plasmodium falciparum. Most antimalarial drugs face decreased efficacy due to the emergence of resistant parasites, which necessitates the discovery of new drugs. To identify new antimalarials, we developed an automated 384-well plate screening assay using P. falciparum parasites that stably express cytoplasmic firefly luciferase. After initial optimization, we tested two different types of compound libraries: known bioactive collections (Library of Pharmacologically Active Compounds [LOPAC] and the library from the National Institute of Neurological Disorders and Stroke [NINDS]) and a library of uncharacterized compounds (ChemBridge). A total of 12,320 compounds were screened at 5.5 μM. Selecting only compounds that reduced parasite growth by 85% resulted in 33 hits from the combined bioactive collection and 130 hits from the ChemBridge library. Fifteen novel drug-like compounds from the bioactive collection were found to be active against P. falciparum. Twelve new chemical scaffolds were found from the ChemBridge hits, the most potent of which was a series based on the 1,4-naphthoquinone scaffold, which is structurally similar to the FDA-approved antimalarial atovaquone. However, in contrast to atovaquone, which acts to inhibit the bc1 complex and block the electron transport chain in parasite mitochondria, we have determined that our new 1,4-napthoquinones act in a novel, non-bc1-dependent mechanism and remain potent against atovaquone- and chloroquine-resistant parasites. Ultimately, this study may provide new probes to understand the molecular details of the malaria life cycle and to identify new antimalarials.
Deficiency of mitochondrial complex I is encountered in both rare and common diseases, but we have limited therapeutic options to treat this lesion to the oxidative phosphorylation system (OXPHOS). Idebenone and menadione are redox-active molecules capable of rescuing OXPHOS activity by engaging complex I-independent pathways of entry, often referred to as “complex I bypass.” In the present study, we created a cellular model of complex I deficiency by using CRISPR genome editing to knock out Ndufa9 in mouse myoblasts, and utilized this cell line to develop a high-throughput screening platform for novel complex I bypass factors. We screened a library of ~40,000 natural product extracts and performed bioassay-guided fractionation on a subset of the top scoring hits. We isolated four plant-derived 1,4-naphthoquinone complex I bypass factors with structural similarity to menadione: chimaphilin and 3-chloro-chimaphilin from Chimaphila umbellata and dehydro-α-lapachone and dehydroiso-α-lapachone from Stereospermum euphoroides. We also tested a small number of structurally related naphthoquinones from commercial sources and identified two additional compounds with complex I bypass activity: 2-methoxy-1,4-naphthoquinone and 2-methoxy-3-methyl-1,4,-naphthoquinone. The six novel complex I bypass factors reported here expand this class of molecules and will be useful as tool compounds for investigating complex I disease biology.
Carboxyl-terminal binding protein (CtBP) is a transcriptional co-repressor that suppresses multiple pro-apoptotic and epithelial genes. CtBP is overexpressed in many human cancers and its overexpression increases stem cell-like features, epithelial-mesenchymal transition, and cancer cell survival. Knockdown of CtBP increases apoptosis independent of p53 and dramatically inhibits tumorigenesis in mouse models. Therefore, targeting CtBP with small molecules that disrupt its interaction with transcription factor partners may be an effective cancer therapy. To elicit its co-repressing effect, CtBP binds to a conserved peptide motif in each transcription factor partner. We developed an AlphaScreen high throughput screening assay to monitor the interaction between CtBP and E1A (which mimics the interaction between CtBP and its transcriptional partners). We screened the LOPAC library of 1280 bioactive compounds and identified NSC95397, which inhibits the CtBP-E1A interaction (IC50 = 2.9 μM). The inhibitory activity of NSC95397 was confirmed using two secondary assays and a counterscreen. NSC95397 also behaved as a weak substrate of CtBP dehydrogenase activity and did not inhibit another dehydrogenase, LDH. Finally, NSC95397 was able to disrupt CtBP-mediated transcriptional repression of a target gene. These studies present a new possibility for the development of a therapeutic agent targeting tumors through disrupting the CtBP transcriptional complex.
CtBP1; NSC95397; E1A; AlphaScreen; Protein-Protein Interaction
Since renal cell carcinoma (RCC) often presents asymptomatically, patients are commonly diagnosed at the metastatic stage when treatment options are limited and survival is poor. Given that progression-free survival with current therapies for metastatic RCC is only one to two years and existing drugs are associated with a high rate of resistance, new pharmacological targets are desperately needed. We identified and evaluated the nuclear exporter protein, chromosome region maintenance protein 1 (CRM1), as a novel potential therapeutic for RCC.
To evaluate novel, selective inhibitors of nuclear export as potential RCC therapeutics.
Materials and Methods
Efficacy of the CRM1 inhibitors, KPT-185 and -251, was tested in several RCC cell lines and in a RCC xenograft model. Apoptosis and cell cycle arrest were quantified, and localization of p53 family proteins was assessed using standard techniques.
KPT-185 attenuated CRM1 and showed increased cytotoxicity in RCC cells in vitro, with evidence of increased apoptosis as well as cell cycle arrest. KPT-185 caused both p53 and p21 to remain primarily in the nucleus in all RCC cell lines, suggesting a mechanism of action of these compounds dependent upon tumor-suppressor protein localization. Furthermore, when administered orally in a high-grade RCC xenograft model, the bioavailable CRM1 inhibitor KPT-251 significantly inhibited tumor growth in vivo with the expected on-target effects and with no obvious toxicity.
The CRM1 inhibitor family of proteins are novel therapeutic targets RCC and deserve further intensive investigation in this and other urologic malignancies.
kidney cancer; nuclear transport; p53; p21; tumor suppressor
Living cells maintain a balance between oxidation and reduction, and
perturbations of this redox balance are thought to contribute to various
diseases. Recent attempts to regulate redox state have focused on electrophiles
(EPs), which activate potent cellular defense systems against oxidative stress.
One example of this approach is exemplified by carnosic acid (CA) and carnosol
(CS), compounds that are found in the herb rosemary (Rosmarinus officinalis).
Importantly, CA and CS themselves are not electrophilic, but in response to
oxidation, become electrophilic, and then activate the Keap1/Nrf2/ARE
(antioxidant response element) transcription pathway to synthesize endogenous
anti-oxidant ‘phase 2’ enzymes. As a result of our efforts to
develop these compounds as therapeutics for brain health, we have formulated two
innovative criteria for drug development: the first concept is the use of
Pro-Electrophilic Drugs (PEDs) that are innocuous in and of themselves; and the
second concept involves the use of compounds that are Pathologically-Activated
Therapeutics (PATs), i.e., these small molecules are chemically converted to
their active form by the very oxidative stress that they are designed to then
combat. The chemical basis for PED and PAT drugs is embodied in the
ortho- and para-hydroquinone electrophilic
cores of the molecules, which are oxidized by the Cu2+/Cu+
cycling system (or potentially by other transition metals). Importantly, this
cycling pathway is under stringent regulation by the cell redox state. We
propose that redox-dependent quinone-formation is the predominant mechanism for
formation of PED and PAT drugs from their precursor compounds. In fact,
redox-dependent generation of the active form of drug from the
“pro-form” distinguishes this therapeutic approach from
traditional EPs such as curcumin, and results in a decrease in clinical side
effects at therapeutic concentrations, e.g., lack of reaction with other thiols
such as glutathione (GSH), which can result in lowering GSH and inducing
oxidative stress in normal cells. We consider this pro-drug quality of PED/PAT
compounds to be a key factor for generating drugs to be used to combat
neurodegenerative diseases that will be clinically tolerated. Given the
contribution of oxidative stress to the pathology of multiple neurodegenerative
diseases, the Keap1/Nrf2/ARE pathway represents a promising drug target for
these PED/PAT agents.
Glutathione; Electrophile; Keap1; Pathologically-Activated Therapeutic; Electrophilic Counterattack
Clear cell renal cell carcinoma (ccRCC) is the most common pathological subtype of kidney cancer. Here, we integrated an unbiased genome-wide RNA interference screen for ccRCC survival regulators with an analysis of recurrently overexpressed genes in ccRCC to identify new therapeutic targets in this disease. One of the most potent survival regulators, the monocarboxylate transporter MCT4 (SLC16A3), impaired ccRCC viability in all eight ccRCC lines tested and was the seventh most overexpressed gene in a meta-analysis of five ccRCC expression datasets. MCT4 silencing impaired secretion of lactate generated through glycolysis and induced cell cycle arrest and apoptosis. Silencing MCT4 resulted in intracellular acidosis, and reduction in intracellular ATP production together with partial reversion of the Warburg effect in ccRCC cell lines. Intra-tumoural heterogeneity in the intensity of MCT4 protein expression was observed in primary ccRCCs. MCT4 protein expression analysis based on the highest intensity of expression in primary ccRCCs was associated with poorer relapse-free survival, whereas modal intensity correlated with Fuhrman nuclear grade. Consistent with the potential selection of subclones enriched for MCT4 expression during disease progression, MCT4 expression was greater at sites of metastatic disease. These data suggest that MCT4 may serve as a novel metabolic target to reverse the Warburg effect and limit disease progression in ccRCC.
Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
renal cell carcinoma; lactate transport; MCT4; SLC16A3; cancer metabolism; Warburg effect; survival regulator; therapeutic target
Accumulating evidence demonstrates that lncRNAs play important roles in regulating gene expression and are involved in various pathological processes. In the present study, we screened the lncRNAs profile in clear cell renal cell carcinoma (ccRCC) from The Cancer Genome Atlas (TCGA) database, and got linc00152, a differentially expressed lncRNA that haven’t been reported in ccRCC. To further explore its role in ccRCC, the level of Linc00152 was detected in 77 paired ccRCC tissues and renal cancer cell lines by qRT-PCR, and its association with overall survival was assessed by statistical analysis. Linc00152 expression was significantly up-regulated in cancerous tissues and cell lines compared with normal counterparts, and high Linc00152 expression was closely associated with advanced TNM stage. Moreover, Linc00152 was found to be able to serve as an independent predictor of overall survival. Further experiments demonstrated that overexpression of Linc00152 can significantly promote cell proliferation and invasion, inhibit cell cycle arrest in G1 phase and dramatically decrease apoptosis in both 786O and Caki-2 cell lines, whereas the opposite results were observed with attenuated Linc00152 expression. Our data suggest that Linc00152 is a novel molecule involved in ccRCC progression as well as a potential prognostic biomarker and therapeutic target.
Linc00152; clear cell renal cell carcinoma; long non-coding RNA; renal cell carcinoma
Para-quinones such as 1,4-benzoquinone (BQ) and menadione (MD) and ortho-quinones including the oxidation products of catecholamines, are derived from xenobiotics as well as endogenous molecules. The effects of quinones on major protein handling systems in cells; the 20/26S proteasome, the ER stress response, autophagy, chaperone proteins and aggresome formation, have not been investigated in a systematic manner. Both BQ and aminochrome (AC) inhibited proteasomal activity and activated the ER stress response and autophagy in rat dopaminergic N27 cells. AC also induced aggresome formation while MD had little effect on any protein handling systems in N27 cells. The effect of NQO1 on quinone induced protein handling changes and toxicity was examined using N27 cells stably transfected with NQO1 to generate an isogenic NQO1-overexpressing line. NQO1 protected against BQ–induced apoptosis but led to a potentiation of AC- and MD-induced apoptosis. Modulation of quinone-induced apoptosis in N27 and NQO1-overexpressing cells correlated only with changes in the ER stress response and not with changes in other protein handling systems. These data suggested that NQO1 modulated the ER stress response to potentiate toxicity of AC and MD, but protected against BQ toxicity. We further demonstrated that NQO1 mediated reduction to unstable hydroquinones and subsequent redox cycling was important for the activation of the ER stress response and toxicity for both AC and MD. In summary, our data demonstrate that quinone-specific changes in protein handling are evident in N27 cells and the induction of the ER stress response is associated with quinone-mediated toxicity.
Quinones; aminochrome; proteasomal inhibition; ER stress responses; autophagy; oxidative stress
Multimeric naphthoquinones are redox-active compounds that exhibit antineoplastic, antiprotozoal, and antiviral activities. Due to their multimodal effect on perturbation of cellular oxidative state, these compounds hold great potential as therapeutic agents against highly proliferative neoplastic cells. In our previous work, we developed a series of novel dimeric naphthoquinones and showed that they were selectively cytotoxic to human acute myeloid leukemia (AML), breast and prostate cancer cell lines. We subsequently identified the oxidoreductase NAD(P)H dehydrogenase, quinone 1 (NQO1) as the major target of dimeric naphthoquinones and proposed a mechanism of action that entailed induction of a futile redox cycling.
Here, for the first time, we describe a direct physical interaction between the bromohydroxy dimeric naphthoquinone E6a and NQO1. Moreover, our studies reveal an extensive binding interface between E6a and the isoalloxazine ring of the flavin adenine dinucleotide (FAD) cofactor of NQO1 in addition to interactions with protein side chains in the active site. We also present biochemical evidence that dimeric naphthoquinones affect the redox state of the FAD cofactor of NQO1. Comparison of the mode of binding of E6a with those of other chemotherapeutics reveals unique characteristics of the interaction that can be leveraged in future drug optimization efforts.
The first structure of a dimeric naphthoquinone-NQO1 complex was reported, which can be used for design and synthesis of more potent next generation dimeric naphthoquinones to target NQO1 with higher affinity and specificity.
Electronic supplementary material
The online version of this article (doi:10.1186/s12900-016-0052-x) contains supplementary material, which is available to authorized users.
NQO1; Dimeric naphthoquinone; Oxidative stress; Anti-cancer agents
Currently, there is no adequate, sensitive, reproducible, specific and noninvasive biomarker that can reliably be used to detect renal cell carcinoma (RCC). Previous studies have elucidated the urinary non-volatile metabolic profile of RCC. However, whether urinary volatile organic compound (VOC) profiles are able to identify RCC remains to be elucidated. In the present study, urine was collected from 22 patients with RCC and 25 healthy subjects. Principal component analysis and orthogonal partial least square discriminant analysis were used to compare the data of patients and healthy subjects, and preoperative and postoperative patients undergoing radical nephrectomy. In total, 11 VOC biomarkers were elevated in the RCC patients compared to the healthy subjects, which were phenol; decanal; 1,6-dioxacyclododecane-7,12-dione; 1-bromo-1-(3-methyl-1-pentenylidene)-2,2,3,3-tetramethyl-cyclopropane; nonanal; 3-ethyl-3-methylheptane; isolongifolene-5-ol; 2,5-cyclohexadiene-1,4-dione, 2,6-bis(1,1-dimethylethyl); tetradecane; aniline; and 2,6,10,14-tetramethyl-pentadecane. Three biomarkers were decreased in RCC patients: styrene, 4-heptanone and dimethylsilanediol. In preoperative patients, 2-ethyl-1-hexanol and cyclohexanone were elevated, while 6-t-butyl-2,2,9,9-tetramethyl-3,5-decadien-7-yne were decreased when compared to postoperative patients. Compared with the healthy subjects, RCC has a unique VOC profile, suggesting that VOC profiles may be a useful diagnostic assay for RCC.
renal cell carcinoma; volatile organic compound; biomarker; diagnosis; urine
Renal-cell carcinoma (RCC) is resistant to almost all chemotherapeutics and radiation therapy. Wnt/β-catenin signaling plays an important role in RCC tumorigenesis, a drug targeting the Wnt signaling is likely to have therapeutic benefit. 15-oxospiramilactone is a new Wnt molecule inhibiter. In the present study, anti-tumor effects on RCC cells and the involved mechanisms were investigated.
Human RCC 786-0 and ACHN cells were treated with different concentrations of 15-oxospiramilactone, and cell viability, cell cycle and apoptosis were measured by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry, respectively. Protein and mRNA expression were assayed by western blotting and quantitative real-time PCR (qPCR). Protein distribution and the association between proteins were assayed by Cytosol and nucleus fractionation and co-immunoprecipitation, respectively. Xenograft assay was used to examine the effect of 15-oxospiramilactone on renal cancer cell proliferation in vivo.
15-oxospiramilactone inhibited the viability of 786-0 and ACHN cells in a dose -dependent manner and it could also significantly suppress the growth of renal carcinoma xenografts and metastasis in nude mice. It also arrested RCC cells at G2/M phase of the cell cycle and induced cell apoptosis. Further study showed that 15-oxospiramilactone inhibited Top-flash reporter activity and decreased the mRNA and/or protein expression of Wnt target genes Axin2, LEF1, NKD1, Cyclin D1 and Survivin, as well as decreased the protein levels of Cdc25c and Cdc2. 15-oxospiramilactone did not affect the cytosol-nuclear distribution, but decreased β-catenin/TCF4 association in RCC cells.
Our data provide first evidence that 15-oxospiramilactone can inhibit cell proliferation in vitro and in vivo, arrest cell cycle at G2/M phase and induce cell apoptosis in RCC cells. The anti-tumor effect is associated with the inhibition of Wnt/β-catenin signaling in RCC cells. The new molecule may be a potential compound for treating renal cell carcinoma.
15-oxospiramilactone; renal cell carcinoma (RCC) cell; Wnt/β-catenin signaling
Dysregulated β-catenin signaling is intricately involved in renal cell carcinoma (RCC) carcinogenesis and progression. Determining potential β-catenin signaling inhibitors would be helpful in ameliorating drug resistance in advanced or metastatic RCC. Screening for β-catenin signaling inhibitors involved in silico inquiry of the PubChem Bioactivity database followed by TCF/LEF reporter assay. The biological effects of ovatodiolide were evaluated in 4 RCC cell lines in vitro and 2 RCC cell lines in a mouse xenograft model. The synergistic effects of ovatodiolide and sorafenib or sunitinib were examined in 2 TKI-resistant RCC cell lines. Ovatodiolide, a pure compound of Anisomeles indica, inhibited β-catenin signaling and reduced RCC cell viability, survival, migration/invasion, and in vitro cell or in vivo mouse tumorigenicity. Cytotoxicity was significantly reduced in a normal kidney epithelial cell line with the treatment. Ovatodiolide reduced phosphorylated β-catenin (S552) that inhibited β-catenin nuclear translocation. Moreover, ovatodiolide decreased β-catenin stability and impaired the association of β-catenin and transcription factor 4. Ovatodiolide combined with sorafenib or sunitinib overcame drug resistance in TKI-resistant RCC cells. Ovatodiolide may be a potent β-catenin signaling inhibitor, with synergistic effects with sorafenib or sunitinib, and therefore, a useful candidate for improving RCC therapy.
Bis(hydroxy)salen.Fe complexes were designed as self-activated chemical nucleases. The presence of a hy-droxyl group on the two salicylidene moieties serve to form a hydroquinone system cooperating with the iron redox system to facilitate spontaneous formation of free radicals. We compared the DNA binding and cleaving properties of the ortho -, meta- and para -(bishydroxy) salen.Fe complexes with that of the corresponding chelate lacking the hydroxyl groups. DNA melting temperature studies indicated that the para complex exhibits the highest affinity for DNA. In addition, this para compound was considerably more potent at cleaving supercoiled plasmid DNA than the regio-isomeric ortho - and meta -hydroxy-salen.Fe complexes, even in the absence of a reducing agent, such as dithiothreitol used to activate the metal complex. The DNA cleaving activity of the para isomer is both time and concentration dependent and the complexed iron atom is absolutely essential for the sequence uniform cleavage of DNA. From a mechanistic point of view, electron spin resonance measurements suggest that DNA contributes positively to the activation of the semi-quinone system and the production of ligand radical species responsible for subsequent strand scission in the absence of a reducing agent. The para -hydroxy-salen.Fe complex has been used for detecting sequence-specific drug-DNA interactions. Specific binding of Hoechst 33258 to AT sequences and chromomycin to GC sequences were shown. The para -bis(hydroxy)salen.Fe derivative complements the tool box of footprinting reagents which can be utilised to produce efficient cleavage of DNA.
Renal cell carcinoma (RCC) is histopathologically heterogeneous with clear cell and papillary the most common subtypes. The most frequent molecular abnormality in clear cell RCC is VHL inactivation but promoter methylation of tumour suppressor genes is common in both subtypes of RCC. To investigate whether RCC CpG methylation status was influenced by histopathology and VHL status we performed high-throughput epigenetic profiling using the Illumina Goldengate Methylation Array in 62 RCC (29 RCC from von Hippel-Lindau (VHL) disease patients, 20 sporadic clear cell RCC with wild type VHL and 13 sporadic papillary RCC).
43 genes were methylated in >20% of primary RCC (range 20–45%) and most (37/43) of these had not been reported previously to be methylated in RCC. The distribution of the number of methylated CpGs in individual tumours differed from the expected Poisson distribution (p < 0.00001; log-likelihood G test) suggesting that a subset of RCC displayed a CpG Island Methylator Phenotype. Comparison of RCC subtypes revealed that, on average, tumour specific CpG methylation was most prevalent in papillary RCC and least in VHL RCC. Many of the genes preferentially methylated in pRCC were linked to TGFβ or ERK/Akt signalling.
These findings demonstrate differing patterns of tumour-specific CpG methylation in VHL and non VHL clear cell RCC and papillary RCC, and identify multiple novel potential CpG methylation biomarkers for RCC.