Heat shock protein 90 inhibitors suppress aryl hydrocarbon receptor-mediated activation of CYP1A1 and CYP1B1 transcription and DNA adduct formation

Association between organophosphate pesticide exposure and atopic dermatitis: a cross-sectional study based on NHANES 1999-2007

Background

Organophosphate pesticides (OPPs) are widely used environmental chemicals with potential health impacts, but their relationship with atopic dermatitis (AD) remains unclear.

Methods

Using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2007, we investigated associations between urinary OPP metabolites and AD in 4,258 adults. Six dialkyl phosphate (DAP) metabolites were measured, and weighted quantile sum (WQS) regression was used to assess mixture effects.

Results

Both DMP (odds ratio [OR] = 1.17, 95% confidence interval [CI]: 1.05-1.31) and DMDTP (OR = 2.23, 95%CI: 1.08-4.60) showed significant positive associations with AD in fully adjusted models. WQS regression revealed significant associations between mixed OPP exposure and AD (OR = 1.25, 95%CI: 1.04-1.50), with DMP contributing most (45.8%) to the mixture effect. Stratified analyses indicated stronger associations in males, younger adults (<60 years), and smokers.

Conclusion

Our findings suggest that OPP exposure, particularly DMP, may be associated with increased AD risk in adults. These results provide new insights into environmental risk factors for AD.

Benzo(a)pyrene regulates chaperone-mediated autophagy via heat shock protein 90

AIMS

Some studies have shown that the Benzo(a)pyrene (BaP) exposure induced oxidative damage, DNA damage and autophagy, but the molecular mechanism is not clear. Heat shock protein 90 (HSP90) is regarded as an important target in cancer therapy and a key factor in autophagy. Therefore, this study aims to clarify the new mechanism of BaP regulating CMA through HSP90.

MAIN METHODS

C57BL mice were fed with BaP at a dose of 25.3mg/kg. A549 cells were treated with different concerntrations of BaP, and MTT assay was used to observe the effect of BaP on the proliferation of A549 cells. DNA damage was detected by alkaline comet assay. Focus experiment for detection of γ-H2AX by immunofluorescence. The mRNA expression of HSP90, HSC70 and Lamp-2a was detected by qPCR. The protein expressions of HSP90, HSC70 and Lamp-2a were detected by Western blot. Next, we knocked down HSP90 expression by the HSP90 Inhibitor, NVP-AUY 922, exposed or HSP90α shRNA lentivirus transduction in A549 cells.

KEY FINDINGS

In these studies, we first found that heat shock protein 90 (HSP90), heat shock cognate 70 (HSC70) and lysosomal-associated membrane protein type 2 receptor (Lamp-2a) expressions of C57BL mice lung tissue and A549 cells exposed to BaP were significant increase, as well as BaP induced DNA double-strand breaks (DSBs) and activated DNA damage responses, as evidenced by comet assay and γ-H2AX foci analysis in A549 cells. Our results demonstrated BaP induced CMA and caused DNA damage. Next, we knocked down HSP90 expression by the HSP90 Inhibitor, NVP-AUY 922, exposed or HSP90α shRNA lentivirus transduction in A549 cells. HSC70 and Lamp-2a expressions of these cells exposed to BaP were not significant increase, which showed that BaP inducted CMA was mediated by HSP90. Further, HSP90α shRNA prevented BaP induced of BaP which suggested BaP regulated CMA and caused DNA damage by HSP90. Our results elucidated a new mechanism of BaP regulated CMA through HSP90.

SIGNIFICANCE

BaP regulated CMA through HSP90. HSP90 is involved in the regulation of gene instability induced by DNA damage by BaP, which promotes CMA. Our study also revealed that BaP regulates CMA through HSP90. This study fills the gap of the effect of BaP on autophagy and its mechanism, which will lead to a more comprehensive understanding of the action mechanism of BaP.

Changes in the gut microbiota of NOD mice in response to an oral Salmonella-based vaccine against type 1 diabetes

We developed an oral Salmonella-based vaccine that prevents and reverses diabetes in non-obese diabetic (NOD) mice. Related to this, the gastrointestinal tract harbors a complex dynamic population of microorganisms, the gut microbiome, that influences host homeostasis and metabolism. Changes in the gut microbiome are associated with insulin dysfunction and type 1 diabetes (T1D). Oral administration of diabetic autoantigens as a vaccine can restore immune balance. However, it was not known if a Salmonella-based vaccine would impact the gut microbiome. We administered a Salmonella-based vaccine to prediabetic NOD mice. Changes in the gut microbiota and associated metabolome were assessed using next-generation sequencing and gas chromatography-mass spectrometry (GC-MS). The Salmonella-based vaccine did not cause significant changes in the gut microbiota composition immediately after vaccination although at 30 days post-vaccination changes were seen. Additionally, no changes were noted in the fecal mycobiome between vaccine- and control/vehicle-treated mice. Significant changes in metabolic pathways related to inflammation and proliferation were found after vaccine administration. The results from this study suggest that an oral Salmonella-based vaccine alters the gut microbiome and metabolome towards a more tolerant composition. These results support the use of orally administered Salmonella-based vaccines that induced tolerance after administration.

Aryl hydrocarbon receptor is regulated via multiple mechanisms in human keratinocytes

Aryl hydrocarbon receptor (AhR) is a basic helix-loop-helix transcription factor activated by polycyclic aromatic hydrocarbons of synthetic and natural origin. While a number of novel AhR ligands have been recently identified, little is known about their possible influence on AhR levels and stability. We used western blot, qRT-PCR and immunocytochemistry to determine the effects of AhR ligands on AhR expression in N-TERT (N-TERT1) immortalized human keratinocytes, and immunohistochemistry to assess patterns of AhR expression in human and mouse skin and skin appendages. While AhR was highly expressed in cultured keratinocytes and in the skin, it was found primarily in the cytoplasm, but not in the nucleus, suggesting its inactivity. At the same time, treatment of N-TERT cells with proteasomal inhibitor MG132 and eventual inhibition of AhR degradation resulted in nuclear AhR accumulation. Treatment of keratinocytes with AhR ligands such as TCDD, FICZ, caused near-complete disappearance of AhR, and treatment with I3C resulted in substantially diminished level of AhR possibly due to ligand-induced AhR degradation. The AhR decay was blocked by proteasome inhibition, indicating degradation-based mechanism of regulation. Additionally, AhR decay was blocked by ligand-selective AhR antagonist CH223191, implying substrate-induced mechanism of degradation. Furthermore, degradation of AhR was blocked in N-TERT cells with knockdown of AhR dimerization partner ARNT (HIF1β), suggesting that ARNT is required for AhR proteolysis. However, addition of hypoxia mimetics (HIF1 pathway activators) CoCl₂ and DMOG had only minor effects on degradation of AhR. Additionally, inhibition of HDACs with Trichostatin A resulted in enhanced expression of AhR in both untreated and ligand-treated cells. These results demonstrate that in immortalized epidermal keratinocytes AhR is primarily regulated post-translationally via proteasome-mediated degradation, and suggest potential means to manipulate AhR levels and signaling in the skin. Overall, the AhR is regulated via multiple mechanisms, including proteasomal ligand- and ARNT-dependent degradation, and transcriptional regulation by HDACs, implying complex system of balancing its expression and protein stability.

Aryl Hydrocarbon Receptor Activation Produces Heat Shock Protein 90 and 70 Overexpression, Prostaglandin E2/Wnt/β-Catenin Signaling Disruption, and Cell Proliferation in MCF-7 and MDA-MB-231 Cells after 24 h and 14 Days of Chlorpyrifos Treatment

The biocide chlorpyrifos (CPF) was described to increase breast cancer risk in humans, to produce breast cancer in animals, and to induce cell proliferation in MCF-7 and MDA-MB-231 cells after 1 and 14 days of treatment. The entire mechanisms related to these CPF actions remain unknown. CPF induced cell proliferation in MCF-7 and MDA-MB-231 cells after 1 and 14 days of treatment by AhR activation through the PGE2/Wnt/β-catenin pathway and HSP90 and HSP70 overexpression. Our results reveal new information on CPF toxic mechanisms induced in human breast cancer cell lines, which could assist in elucidating its involvement in breast cancer.

Evaluation of aryl hydrocarbon receptor expression in oral squamous cell carcinoma and normal oral mucosa using western blot

Background

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that acts as a binding site for toxic chemicals, particularly the dioxin group of chemicals. Elevated levels of AHR have been observed in various human cancers, including lung carcinomas, hepatic carcinomas and in mammary tumors. However, the expression of AHR in oral squamous cell carcinoma (OSCC) patients who are tobacco users are less explored.

Aims and Objectives

The aim of the present study is to evaluate and compare AHR levels in OSSC patients and in normals using Western blot technique in an attempt to explore the possible role of AHR in oral carcinogenesis.

Materials and Methods

The study sample consisted of ten oral squamous cell carcinoma cases which were diagnosed clinically and confirmed histopathologically as OSCC and four samples of the normal oral mucosa. AHR protein expression was evaluated using Western blot technique and chemiluminescence detection kit. The densitometry was performed on a Microtek scan maker MSP flatbed scanner and quantified using Image J software. Mean AHR protein levels were calculated and compared between OSCC and normal oral mucosa using Student's t-test.

Results

The mean AHR protein level in OSCC samples (n = 10) was 2878.90 ± 1231.27 and 975.75 ± 227.27 in the normal oral mucosa (n = 4). The OSCC samples showed significantly higher levels of AHR protein compared to the normal oral mucosa (P = 0.008).

Conclusion

The study showed a significantly higher expression of AHR in oral squamous cell carcinoma samples when compared to the normal oral mucosa, suggesting a possible role of AHR in the initiation, promotion and progression of oral squamous cell carcinoma.

SARS-CoV-2 infection remodels the host protein thermal stability landscape

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global threat to human health and has compromised economic stability. In addition to the development of an effective vaccine, it is imperative to understand how SARS-CoV-2 hijacks host cellular machineries on a system-wide scale so that potential host-directed therapies can be developed. In situ proteome-wide abundance and thermal stability measurements using thermal proteome profiling (TPP) can inform on global changes in protein activity. Here we adapted TPP to high biosafety conditions amenable to SARS-CoV-2 handling. We discovered pronounced temporal alterations in host protein thermostability during infection, which converged on cellular processes including cell cycle, microtubule and RNA splicing regulation. Pharmacological inhibition of host proteins displaying altered thermal stability or abundance during infection suppressed SARS-CoV-2 replication. Overall, this work serves as a framework for expanding TPP workflows to globally important human pathogens that require high biosafety containment and provides deeper resolution into the molecular changes induced by SARS-CoV-2 infection.

Benzo[a]pyrene and 2,3-benzofuran induce divergent temporal patterns of AhR-regulated responses in zebrafish embryos (Danio rerio)

Biotests like the fish embryo toxicity test have become increasingly popular in risk assessment and evaluation of chemicals found in the environment. The large range of possible endpoints is a big advantage when researching on the mode of action of a certain substance. Here, we utilized the frequently used model organism zebrafish (Danio rerio) to examine regulative mechanisms in the pathway of the aryl-hydrocarbon receptor (AHR) in early development. We exposed embryos to representatives of two chemical classes known to elicit dioxin-like activity: benzo[a]pyrene for polycyclic aromatic hydrocarbons (PAHs) and 2,3-benzofuran for polar O-substituted heterocycles as a member of heterocyclic compounds in general (N-, S-, O-heterocycles; NSO-hets). We measured gene transcription of the induced P450 cytochromes (cyp1), their formation of protein and biotransformation activity throughout the whole embryonic development until 5 days after fertilization. The results show a very specific time course of transcription depending on the chemical properties (e.g. halogenation, planarity, K_ow), the physical decay and the biodegradability of the tested compound. However, although this temporal pattern was not precisely transferable onto the protein level, significant regulation in enzymatic activity over time could be detected. We conclude, that a careful choice of time and end point as well as consideration of the chemical properties of a substance are fairly important when planning, conducting and especially evaluating biotests.

AHR and GPER mediate the stimulatory effects induced by 3-methylcholanthrene in breast cancer cells and cancer-associated fibroblasts (CAFs)

BACKGROUND

The chemical carcinogen 3-methylcholanthrene (3MC) binds to the aryl hydrocarbon receptor (AHR) that regulates the expression of cytochrome P450 (CYP) enzymes as CYP1B1, which is involved in the oncogenic activation of environmental pollutants as well as in the estrogen biosynthesis and metabolism. 3MC was shown to induce estrogenic responses binding to the estrogen receptor (ER) α and stimulating a functional interaction between AHR and ERα. Recently, the G protein estrogen receptor (GPER) has been reported to mediate certain biological responses induced by endogenous estrogens and environmental compounds eliciting an estrogen-like activity.

METHODS

Molecular dynamics and docking simulations were performed to evaluate the potential of 3MC to interact with GPER. SkBr3 breast cancer cells and cancer-associated fibroblasts (CAFs) derived from breast tumor patients were used as model system. Real-time PCR and western blotting analysis were performed in order to evaluate the activation of transduction mediators as well as the mRNA and protein levels of CYP1B1 and cyclin D1. Co-immunoprecipitation studies were performed in order to explore the potential of 3MC to trigger the association of GPER with AHR and EGFR. Luciferase assays were carried out to determine the activity of CYP1B1 promoter deletion constructs upon 3MC exposure, while the nuclear shuttle of AHR induced by 3MC was assessed through confocal microscopy. Cell proliferation stimulated by 3MC was determined as biological counterpart of the aforementioned experimental assays. The statistical analysis was performed by ANOVA.

RESULTS

We first ascertained by docking simulations the ability of 3MC to interact with GPER. Thereafter, we established that 3MC activates the EGFR/ERK/c-Fos transduction signaling through both AHR and GPER in SkBr3 cells and CAFs. Then, we found that these receptors are involved in the up-regulation of CYP1B1 and cyclin D1 as well as in the stimulation of growth responses induced by 3MC.

CONCLUSIONS

In the present study we have provided novel insights regarding the molecular mechanisms by which 3MC may trigger a physical and functional interaction between AHR and GPER, leading to the stimulation of both SkBr3 breast cancer cells and CAFs. Altogether, our results indicate that 3MC may engage both GPER and AHR transduction pathways toward breast cancer progression.

E-cigarette Aerosol Condensate Enhances Metabolism of Benzo(a)pyrene to Genotoxic Products, and Induces CYP1A1 and CYP1B1, Likely by Activation of the Aryl Hydrocarbon Receptor

E-cigarette aerosol contains lower levels of most known carcinogens than tobacco smoke, but many users of e-cigarettes are also smokers, and these individuals may be vulnerable to possible promoting and/or cocarcinogenic effects of e-cigarettes. We investigated the possibility that a condensate of e-cigarette aerosol (EAC) enhances the metabolism of the tobacco carcinogen, benzo(a)pyrene (BaP), to genotoxic products in a human oral keratinocyte cell line. Cells were pretreated with EAC from two popular e-cigs and then with BaP. Metabolism to its ultimate carcinogenic metabolite, anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydro B[a]P (BPDE), was assayed by measuring isomers of its spontaneous hydrolysis products, BaP tetrols. The pretreatment of cells with EAC enhanced the rate of BaP tetrol formation several fold. Pretreatment with the e-liquid resulted in a smaller enhancement. The treatment of cells with EAC induced CYP1A1/1B1 mRNA and protein. The enhancement of BaP tetrol formation was inhibited by the aryl hydrocarbon receptor (AhR) inhibitor, α-napthoflavone, indicating EAC likely induces CYP1A1/1B1 and enhances BaP metabolism by activating the AhR. To our knowledge, this is first report demonstrating that e-cigarettes can potentiate the genotoxic effects of a tobacco smoke carcinogen.

Celastrol and Its Role in Controlling Chronic Diseases

Celastrol, a triterpenoid derived from traditional Chinese medicinal plants, has anti-inflammatory, antioxidant, and anticancer activities. Celastrol has shown preventive/therapeutic effects in experimental models of several chronic diseases. These include, chronic inflammatory and autoimmune diseases (e.g., rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, inflammatory bowel disease, and psoriasis), neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis), atherosclerosis, obesity, Type 2 diabetes, and cancer. Celastrol modulates intricate cellular pathways and networks associated with disease pathology, and it interrupts or redirects the aberrant cellular and molecular events so as to limit disease progression and facilitate recovery, where feasible. The major cell signaling pathways modulated by celastrol include the NF-kB pathway, MAPK pathway, JAK/STAT pathway, PI3K/Akt/mTOR pathway, and antioxidant defense mechanisms. Furthermore, celastrol modulates cell proliferation, apoptosis, proteasome activity, heat-shock protein response, innate and adaptive immune responses, angiogenesis, and bone remodeling. Current understanding of the mechanisms of action of celastrol and information about its disease-modulating activities in experimental models have set the stage for testing celastrol in clinical studies as a therapeutic agent for several chronic human diseases.

Comparative Toxicogenomic Responses to the Flame Retardant mITP in Developing Zebrafish

Monosubstituted isopropylated triaryl phosphate (mITP) is a major component of Firemaster 550, an additive flame retardant mixture commonly used in polyurethane foams. Developmental toxicity studies in zebrafish established mITP as the most toxic component of FM 550, which causes pericardial edema and heart looping failure. Mechanistic studies showed that mITP is an aryl hydrocarbon receptor (AhR) ligand; however, the cardiotoxic effects of mITP were independent of the AhR. We performed comparative whole genome transcriptomics in wild-type and ahr2^hu3335 zebrafish, which lack functional ahr2, to identify transcriptional signatures causally involved in the mechanism of mITP-induced cardiotoxicity. Regardless of ahr2 status, mITP exposure resulted in decreased expression of transcripts related to the synthesis of all-trans-retinoic acid and a host of Hox genes. Clustered gene ontology enrichment analysis showed unique enrichment in biological processes related to xenobiotic metabolism and response to external stimuli in wild-type samples. Transcript enrichments overlapping both genotypes involved the retinoid metabolic process and sensory/visual perception biological processes. Examination of the gene-gene interaction network of the differentially expressed transcripts in both genetic backgrounds demonstrated a strong AhR interaction network specific to wild-type samples, with overlapping genes regulated by retinoic acid receptors (RARs). A transcriptome analysis of control ahr2-null zebrafish identified potential cross-talk among AhR, Nrf2, and Hif1α. Collectively, we confirmed that mITP is an AhR ligand and present evidence in support of our hypothesis that mITP's developmental cardiotoxic effects are mediated by inhibition at the RAR level.

Role for the Aryl Hydrocarbon Receptor and Diverse Ligands in Oral Squamous Cell Carcinoma Migration and Tumorigenesis

Over 45,000 new cases of oral and pharyngeal cancers are diagnosed and account for over 8,000 deaths a year in the United States. An environmental chemical receptor, the aryl hydrocarbon receptor (AhR), has previously been implicated in oral squamous cell carcinoma (OSCC) initiation as well as in normal tissue-specific stem cell self-renewal. These previous studies inspired the hypothesis that the AhR plays a role in both the acquisition and progression of OSCC, as well as in the formation and maintenance of cancer stem-like cells. To test this hypothesis, AhR activity in two oral squamous cell lines was modulated with AhR prototypic, environmental and bacterial AhR ligands, AhR-specific inhibitors, and phenotypic, genomic and functional characteristics were evaluated. The data demonstrate that: (i) primary OSCC tissue expresses elevated levels of nuclear AhR as compared with normal tissue, (ii) AhR mRNA expression is upregulated in 320 primary OSCCs, (iii) AhR hyperactivation with several ligands, including environmental and bacterial ligands, significantly increases AhR activity, ALDH1 activity, and accelerates cell migration, (iv) AhR inhibition blocks the rapid migration of OSCC cells and reduces cell chemoresistance, (v) AhR knockdown inhibits tumorsphere formation in low adherence conditions, and (vi) AhR knockdown inhibits tumor growth and increases overall survival in vivo These data demonstrate that the AhR plays an important role in development and progression of OSCC, and specifically cancer stem-like cells. Prototypic, environmental, and bacterial AhR ligands may exacerbate OSCC by enhancing expression of these properties.

IMPLICATIONS

This study, for the first time, demonstrates the ability of diverse AhR ligands to regulate AhR activity in oral squamous cell carcinoma cells, as well as regulate several important characteristics of oral cancer stem cells, in vivo and in vitro Mol Cancer Res; 14(8); 696-706. ©2016 AACR.

Characterisation of transcriptional responses to dioxins and dioxin-like contaminants in roach (Rutilus rutilus) using whole transcriptome analysis

There is significant concern regarding the contamination of riverine sediments with dioxins and dioxin-like compounds (DLCs), including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and some polycyclic aromatic hydrocarbons (PAHs). The majority of studies investigating the ecotoxicology of DLCs in fish have focused on a few standard model species. However, there is significant uncertainty as to whether these model species are representative of native river fish, particularly in Europe. In this study, the transcriptional responses following exposure to equipotent concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), PCB 156 or the dioxin-like PAH, benzo[k]fluoranthene (BkF), were investigated in juvenile roach (Rutilus rutilus), a fish species that constitutes a large proportion of the fish biomass in freshwater bodies throughout Europe. To this end, RNA sequencing analysis was used to comprehensively characterise the molecular mechanisms and pathways of toxicity of these DLCs. Whole transcriptome analyses using ClueGO software revealed that DLCs have the potential to disrupt a number of important processes, including energy metabolism, oogenesis, the immune system, apoptosis and the response to oxidative stress. However, despite using equipotent concentrations, there was very little conservation of the transcriptional responses observed in fish exposed to different DLCs. TCDD provoked significant specific changes in the levels of transcripts related to immunotoxicity and carbohydrate metabolism, while PCB 156 caused virtually no specific effects. Exposure to BkF affected the most diverse suite of molecular functions and biological processes, including blood coagulation, oxidative stress responses, unspecific responses to organic or inorganic substances/stimuli, cellular redox homeostasis and specific receptor pathways. To our knowledge, this is the first study of the transcriptome-wide effects of different classes of DLCs in fish. These findings represent an important step towards describing complete toxicity pathways of DLCs, which will be important in the context of informing risk assessments of DLC toxicity in native fish species.

Time-dependent expression and activity of cytochrome P450 1s in early life-stages of the zebrafish (Danio rerio)

Zebrafish embryos are being increasingly used as model organisms for the assessment of single substances and complex environmental samples for regulatory purposes. Thus, it is essential to fully understand the xenobiotic metabolism during the different life-stages of early development. The aim of the present study was to determine arylhydrocarbon receptor (AhR)-mediated activity during selected times of early development using qPCR, enzymatic activity through measurement of 7-ethoxyresorufin-O-deethylase (EROD) activity, and protein expression analysis. In the present study, gene expression of cyp1a, cyp1b1, cyp1c1, cyp1c2, and ahr2 as well as EROD activity were investigated up to 120 h postfertilization (hpf) after exposure to either β-naphthoflavone (BNF) or a polycyclic aromatic hydrocarbons (PAH)-contaminated sediment extract from Vering Kanal in Hamburg (VK). Protein expression was measured at 72 hpf after exposure to 20 μg/L BNF. Altered proteins were identified by matrix assisted laser desorption ionization time-of-flight (MALDI-TOF) peptide mass fingerprinting. Distinct patterns of basal messenger RNA (mRNA) expression were found for each of the cyp1 genes, suggesting specific roles during embryonic development. All transcripts were induced by BNF and VK. ahr2 mRNA expression was significantly upregulated after exposure to VK. All cyp1 genes investigated showed a temporal decline in expression at 72 hpf. The significant decline of Hsp 90β protein at 72 hpf after exposure to BNF may suggest an explanation for the decline of cyp1 genes at this time point as Hsp 90β is of major importance for the functioning of the Ah-receptor. EROD activity measured in embryos was significantly induced after 96 hpf of exposure to BNF or VK. Together, these results demonstrate distinct temporal patterns of cyp1 genes and protein activities in zebrafish embryos as well as show a need to investigate further the xenobiotic biotransformation system during early development of zebrafish.

α-Naphthoflavone Increases Lipid Accumulation in Mature Adipocytes and Enhances Adipocyte-Stimulated Endothelial Tube Formation

The aryl hydrocarbon receptor (AhR) is a ligand-activated factor that regulates biological effects associated with obesity. The AhR agonists, such as environmental contaminants 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and β-naphthoflavone (BNF), inhibit preadipocyte differentiation and interfere with the functions of adipose tissue, whereas the antagonist may have opposite or protective effects in obesity. This study investigated the effects of α-naphthoflavone (α-NF), an AhR antagonist, on adipogenesis- and angiogenesis-associated factors in mature adipocytes and on cross-talk of mature adipocytes with endothelial cells (ECs). Besides, the roles of the AhR on lipid accumulation and on secretion of vascular endothelial growth factor were also determined by introducing siRNA of AhR. Differentiated 3T3-L1 cells were treated with α-naphthoflavone (α-NF) (1-5 μM) for 16 h. Lipid accumulation and the expressions of AhR-associated factors in the cells were determined. The interaction between adipocytes and ECs was investigated by cultivating ECs with conditioned medium (CM) from α-NF-treated mature adipocytes, followed by the determination of endothelial tube formation. The results showed that α-NF significantly increased triglyceride (TG) accumulation in mature adipocytes, which was associated with increased expression of hormone-sensitive lipase (HSL), estrogen receptor (ER), as well as decreased expression of AhR, AhR nuclear translocator (ARNT), cytochrome P4501B1 (CYP1B1), and nuclear factor erythroid-2-related factor (NRF-2) proteins. In addition, CM stimulated formation of tube-like structures in ECs, and α-NF further enhanced such stimulation in association with modulated the secretions of various angiogenic mediators by mature adipocytes. Similarly, increased TG accumulation and vascular endothelial growth factor (VEGF) secretion were observed in AhR-knockout cells. In conclusion, α-NF increased TG accumulation in mature adipocytes and enhanced mature adipocyte-stimulated tube formation in ECs, suggesting that the AhR may suppress obesity-induced adverse effects, and α-NF abolished the protective effects of the AhR.

The quinone methide aurin is a heat shock response inducer that causes proteotoxic stress and Noxa-dependent apoptosis in malignant melanoma cells

Pharmacological induction of proteotoxic stress is rapidly emerging as a promising strategy for cancer cell-directed chemotherapeutic intervention. Here, we describe the identification of a novel drug-like heat shock response inducer for the therapeutic induction of proteotoxic stress targeting malignant human melanoma cells. Screening a focused library of compounds containing redox-directed electrophilic pharmacophores employing the Stress & Toxicity PathwayFinder(TM) PCR Array technology as a discovery tool, a drug-like triphenylmethane-derivative (aurin; 4-[bis(p-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one) was identified as an experimental cell stress modulator that causes (i) heat shock factor transcriptional activation, (ii) up-regulation of heat shock response gene expression (HSPA6, HSPA1A, DNAJB4, HMOX1), (iii) early unfolded protein response signaling (phospho-PERK, phospho-eIF2α, CHOP (CCAAT/enhancer-binding protein homologous protein)), (iv) proteasome impairment with increased protein-ubiquitination, and (v) oxidative stress with glutathione depletion. Fluorescence polarization-based experiments revealed that aurin displays activity as a geldanamycin-competitive Hsp90α-antagonist, a finding further substantiated by molecular docking and ATPase inhibition analysis. Aurin exposure caused caspase-dependent cell death in a panel of human malignant melanoma cells (A375, G361, LOX-IMVI) but not in non-malignant human skin cells (Hs27 fibroblasts, HaCaT keratinocytes, primary melanocytes) undergoing the aurin-induced heat shock response without impairment of viability. Aurin-induced melanoma cell apoptosis depends on Noxa up-regulation as confirmed by siRNA rescue experiments demonstrating that siPMAIP1-based target down-regulation suppresses aurin-induced cell death. Taken together, our data suggest feasibility of apoptotic elimination of malignant melanoma cells using the quinone methide-derived heat shock response inducer aurin.

Aryl hydrocarbon receptor-dependent regulation of miR-196a expression controls lung fibroblast apoptosis but not proliferation

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor implicated in the regulation of apoptosis and proliferation. Although activation of the AhR by xenobiotics such as dioxin inhibits the cell cycle and control apoptosis, paradoxically, AhR expression also promotes cell proliferation and survival independent of exogenous ligands. The microRNA (miRNA) miR-196a has also emerged as a regulator of proliferation and apoptosis but a relationship between the AhR and miR-196a is not known. Therefore, we hypothesized that AhR-dependent regulation of endogenous miR-196a expression would promote cell survival and proliferation. Utilizing lung fibroblasts from AhR deficient (AhR(-/-)) and wild-type (AhR(+/+)) mice, we show that there is ligand-independent regulation of miRNA, including low miR-196a in AhR(-/-) cells. Validation by qRT-PCR revealed a significant decrease in basal expression of miR-196a in AhR(-/-) compared to AhR(+/+) cells. Exposure to AhR agonists benzo[a]pyrene (B[a]P) and FICZ as well as AhR antagonist CH-223191 decreased miR-196a expression in AhR(+/+) fibroblasts concomitant with decreased AhR protein levels. There was increased proliferation only in AhR(+/+) lung fibroblasts in response to serum, corresponding to a decrease in p27(KIP1) protein, a cyclin-dependent kinase inhibitor. Increasing the cellular levels of miR-196a had no effect on proliferation or expression of p27(KIP1) in AhR(-/-) fibroblasts but attenuated cigarette smoke-induced apoptosis. This study provides the first evidence that AhR expression is essential for the physiological regulation of cellular miRNA levels- including miR-196a. Future experiments designed to elucidate the functional relationship between the AhR and miR-196a may delineate additional novel ligand-independent roles for the AhR.

p53 modulates Hsp90 ATPase activity and regulates aryl hydrocarbon receptor signaling

The aryl hydrocarbon receptor (AhR), a client protein of heat shock protein 90 (Hsp90), is a ligand-activated transcription factor that plays a role in polycyclic aromatic hydrocarbon (PAH)-induced carcinogenesis. Tobacco smoke activates AhR signaling leading to increased transcription of CYP1A1 and CYP1B1, which encode proteins that convert PAHs to mutagens. Recently, p53 was found to regulate Hsp90 ATPase activity via effects on activator of Hsp90 ATPase (Aha1). It is possible, therefore, that AhR-dependent expression of CYP1A1 and CYP1B1 might be affected by p53 status. The main objective of this study was to determine whether p53 modulated AhR-dependent gene expression and PAH metabolism. Here, we show that silencing p53 led to elevated Aha1 levels, increased Hsp90 ATPase activity, and enhanced CYP1A1 and CYP1B1 expression. Overexpression of wild-type p53 suppressed levels of CYP1A1 and CYP1B1. The significance of Aha1 in mediating these p53-dependent effects was determined. Silencing of Aha1 led to reduced Hsp90 ATPase activity and downregulation of CYP1A1 and CYP1B1. In contrast, overexpressing Aha1 was associated with increased Hsp90 ATPase activity and elevated levels of CYP1A1 and CYP1B1. Using p53 heterozygous mutant epithelial cells from patients with Li-Fraumeni syndrome, we show that monoallelic mutation of p53 was associated with elevated levels of CYP1A1 and CYP1B1 under both basal conditions and following treatment with benzo[a]pyrene. Treatment with CP-31398, a p53 rescue compound, suppressed benzo[a]pyrene-mediated induction of CYP1A1 and CYP1B1 and the formation of DNA adducts. Collectively, our results suggest that p53 affects AhR-dependent gene expression, PAH metabolism, and possibly carcinogenesis.

The cigarette smoke constituent benzo[a]pyrene disrupts metabolic enzyme, and apoptosis pathway member gene expression in ovarian follicles

Benzo[a]pyrene (B[a]P) is a prototypical polycyclic aromatic hydrocarbon (PAH) present in cigarette smoke. We previously showed that B[a]P adversely affects follicular development and survival. The objective of this study was to identify the key molecular pathways underlying B[a]P-induced abnormal follicular development. Isolated follicles (100-130 μm) from ovaries of F1 hybrid (C57BL/6j×CBA/Ca) mice were cultured for 8 (preantral/antral follicles) and 12 (preovulatory follicles) days in increasing concentrations of B[a]P (0 ng/mL [control] to 45 ng/mL). Expression of aryl hydrocarbon receptor (AhR), aryl hydroxylase steroidogenic enzyme, cell-cycle, and apoptotic genes were quantified. B[a]P exposure significantly (P<0.05) increased mRNA expression of Cyp1a1 in preantral/antral follicles and Cyp1b1, Bax and Hsp90ab1 in preovulatory follicles. No significant effect on mRNA expression of StAR, Cyp11a1, aromatase, Cdk4, Cdk2, Ccnd2, cIAP2, and survivin was observed. In conclusion, this study suggests that B[a]P exposure significantly affects the phase I enzymes and cell death genes during preantral/antral and preovulatory growth, and thus highlight the AhR signaling and apoptotis pathways in delayed follicle growth and decreased viability.

Aryl hydrocarbon receptor is a target of 17-Allylamino-17-demethoxygeldanamycin and enhances its anticancer activity in lung adenocarcinoma cells

We have demonstrated that aryl hydrocarbon receptor (AhR) is overexpressed in lung adenocarcinoma (AD). AhR is usually associated with heat shock protein 90 (Hsp90) in the cytoplasm. 17-Allylamino-17-demethoxygeldanamycin (17-AAG), an Hsp90 inhibitor, is currently under evaluation for its anticancer activity in clinical trials. Here we investigated whether AhR plays a role in 17-AAG-mediated anticancer activity by functioning as a downstream target or by modulating its anticancer efficacy. AhR expression in lung AD cells was modulated by siRNA interference or overexpression. Tumor growth was determined with colony formation in vitro or in vivo. Anticancer activity of 17-AAG was determined by measuring cell viability, cell cycle distribution, and expression of cell cycle regulators. Proteins and mRNA levels were examined by immunoblotting and the real-time reverse transcription-polymerase chain reaction, respectively. In this study, AhR overexpression positively modulated growth of lung AD cells, at least partially, via RelA-dependent mechanisms. Although treatment with 17-AAG reduced AhR levels and AhR-regulated gene expression in lung AD cells, AhR expression increased anticancer activity of 17-AAG. In addition, 17-AAG treatment reduced cell viability, CDK2, CDK4, cyclin E, cyclin D1, and phosphorylated Rb levels in AhR-expressing lung AD cells. NAD(P)H:quinone oxidoreductase (NQO1), which is regulated by AhR, was shown to increase anticancer activity of 17-AAG in cells. Knockdown of NQO1 expression attenuated the reduction of cell cycle regulators by 17-AAG treatment in AhR overexpressed cells. We demonstrated that AhR protein not only functions as a downstream target of 17-AAG, but also enhances anticancer activity of 17-AAG in lung AD cells.

The citrus flavanone naringenin suppresses CYP1B1 transactivation through antagonising xenobiotic-responsive element binding

Exposure to environmental toxicants or exogenous oestrogen increases the risk of cancer. Some toxicants such as polycyclic aromatic hydrocarbons (PAH) undergo biotransformation to become genotoxic agents. Cytochrome p450 (CYP) 1B1 is an enzyme catalysing this transformation. Consumption of fruit and vegetables is considered to be protective against carcinogenesis, and naringenin can be found abundantly in citrus fruits. In the present study, the effect of naringenin on the regulation of CYP1B1 was investigated in MCF-7 cells. Enzyme inhibition assays revealed that naringenin inhibited CYP1B1 at or above 5 μm but not CYP1A1 activity. Quantitative PCR analysis also demonstrated that 1 μm-naringenin reduced CYP1B1 mRNA expression induced by 7,12-dimethylbenz(α)anthracene (DMBA). Further study illustrated that the suppression was at the transcriptional level. Since previous studies have shown that oestrogen response element (ERE) and xenobiotic-responsive element (XRE) are functional binding sequences in the promoter region of CYP1B1, interference of DNA binding on these two elements was pursued. Employing reporter gene assays as well as the electromobility shift assay, we verified that naringenin counteracted DMBA-induced XRE binding at − 1675. These results supported the notion that fruit consumption could be a protective measure against PAH biotransformation.

Should autism be considered a canary bird telling that Homo sapiens may be on its way to extinction?

There has been a dramatic enhancement of the reported incidence of autism in different parts of the world over the last 30 years. This can apparently not be explained only as a result of improved diagnosis and reporting, but may also reflect a real change. The causes of this change are unknown, but if we shall follow T.C. Chamberlin's principle of multiple working hypotheses, we need to take into consideration the possibility that it partly may reflect an enhancement of the average frequency of responsible alleles in large populations. If this hypothesis is correct, it means that the average germline mutation rate must now be much higher in the populations concerned, compared with the natural mutation rate in hominid ancestors before the agricultural and industrial revolutions. This is compatible with the high prevalence of impaired human semen quality in several countries and also with what is known about high levels of total exposure to several different unnatural chemical mutagens, plus some natural ones at unnaturally high levels. Moreover, dietary deficiency conditions that may lead to enhancement of mutation rates are also very widespread, affecting billions of people. However, the natural mutation rate in hominids has been found to be so high that there is apparently no tolerance for further enhancement of the germline mutation rate before the Eigen error threshold will be exceeded and our species will go extinct because of mutational meltdown. This threat, if real, should be considered far more serious than any disease causing the death only of individual patients. It should therefore be considered the first and highest priority of the best biomedical scientists in the world, of research-funding agencies and of all medical doctors to try to stop the express train carrying all humankind as passengers on board before it arrives at the end station of our civilization.

Cardiosulfa induces heart deformation in zebrafish through the AhR-mediated, CYP1A-independent pathway

Heart development is a complicated and elaborate biological process. To study this and similar complicated process and diseases, the discovery and use of small molecules for probing biological events is invaluable. As part of such an investigation, we have identified cardiosulfa, a small molecule that induces severely impaired heart morphology and function in zebrafish. The results of the present study show that cardiosulfa-promoted heart deformation is protected by negative regulators of the aryl hydrocarbon receptor (AhR) signaling pathway, such as the AhR antagonist CH-223191 and an AhR2-morpholino antisense oligonucleotide, zfahr2-MO. However, the toxic effect of cardiosulfa is not alleviated by zfcyp1a-MO, a morpholino antisense oligo for cytochrome P450 1A (CYP1A), which is the most well-characterized gene of the AhR pathway. Similar results were obtained for the known AhR agonist PCB126. These observations suggest that cardiosulfa causes heart deformation in zebrafish through the AhR-mediated, CYP1A-independent pathway. Our results indicate that cardiosulfa has potential as a novel type of a biological probe to investigate the AhR pathway.

Carnosol, a constituent of Zyflamend, inhibits aryl hydrocarbon receptor-mediated activation of CYP1A1 and CYP1B1 transcription and mutagenesis

The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, plays a significant role in polycyclic aromatic hydrocarbon (PAH)-induced carcinogenesis. In the upper aerodigestive tract of humans, tobacco smoke, a source of PAHs, activates the AhR leading to increased expression of CYP1A1 and CYP1B1, which encode proteins that convert PAHs to genotoxic metabolites. Inhibitors of Hsp90 ATPase cause a rapid decrease in levels of AhR, an Hsp90 client protein, and thereby block PAH-mediated induction of CYP1A1 and CYP1B1. The main objective of this study was to determine whether Zyflamend, a polyherbal preparation, suppressed PAH-mediated induction of CYP1A1 and CYP1B1 and inhibited DNA adduct formation and mutagenesis. We also investigated whether carnosol, one of multiple phenolic antioxidants in Zyflamend, had similar inhibitory effects. Treatment of cell lines derived from oral leukoplakia (MSK-Leuk1) and skin (HaCaT) with benzo[a]pyrene (B[a]P), a prototypic PAH, induced CYP1A1 and CYP1B1 transcription, resulting in enhanced levels of message and protein. Both Zyflamend and carnosol suppressed these effects of B[a]P. Notably, both Zyflamend and carnosol inhibited Hsp90 ATPase activity and caused a rapid reduction in AhR levels. The formation of B[a]P-induced DNA adducts and mutagenesis was also inhibited by Zyflamend and carnosol. Collectively, these results show that Zyflamend and carnosol inhibit Hsp90 ATPase leading to reduced levels of AhR, suppression of B[a]P-mediated induction of CYP1A1 and CYP1B1, and inhibition of mutagenesis. Carnosol-mediated inhibition of Hsp90 ATPase activity can help explain the chemopreventive activity of herbs such as Rosemary, which contain this phenolic antioxidant.

Concentration dependent effects of tobacco particulates from different types of cigarettes on expression of drug metabolizing proteins, and benzo(a)pyrene metabolism in primary normal human oral epithelial cells

The ability of tobacco smoke (TS) to modulate phase I and II enzymes and affect metabolism of tobacco carcinogens is likely an important factor in its carcinogenicity. For the first time several types of TS particulates (TSP) were compared in different primary cultured human oral epithelial cells (NOE) for their abilities to affect metabolism of the tobacco carcinogen, (BaP) to genotoxic products, and expression of drug metabolizing enzymes. TSP from, reference filtered (2RF4), mentholated (MS), reference unfiltered, (IR3), ultra low tar (UL), and cigarettes that primarily heat tobacco (ECL) were tested. Cells pretreated with TSP concentrations of 0.2-10 μg/ml generally showed increased rates of BaP metabolism; those treated with TSP concentrations above 10 μg/ml showed decreased rates. Effects of TSPs were similar when expressed on a weight basis. Weights of TSP/cigarette varied in the order: MS≈IR3>2RF4>ECL>UL. All TSPs induced the phase I proteins, cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1), phase II proteins, NAD(P)H dehydrogenase quinone 1 (NQO1), and microsomal glutathione S-transferase 1 (MGST1), and additionally, hydroxysteroid (17-beta) dehydrogenase 2 (HSD17B2), as assessed by qRT-PCR. The pattern of gene induction at probable physiological levels favored activation over detoxification.

Estrogen and cytochrome P450 1B1 contribute to both early- and late-stage head and neck carcinogenesis

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most common type of cancer in the United States. The goal of this study was to evaluate the contribution of estrogens to the development of HNSCCs. Various cell lines derived from early- and late-stage head and neck lesions were used to characterize the expression of estrogen synthesis and metabolism genes, including cytochrome P450 (CYP) 1B1, examine the effect of estrogen on gene expression, and evaluate the role of CYP1B1 and/or estrogen in cell motility, proliferation, and apoptosis. Estrogen metabolism genes (CYP1B1, CYP1A1, catechol-o-methyltransferase, UDP-glucuronosyltransferase 1A1, and glutathione-S-transferase P1) and estrogen receptor (ER) β were expressed in cell lines derived from both premalignant (MSK-Leuk1) and malignant (HNSCC) lesions. Exposure to estrogen induced CYP1B1 2.3- to 3.6-fold relative to vehicle-treated controls (P = 0.0004) in MSK-Leuk1 cells but not in HNSCC cells. CYP1B1 knockdown by shRNA reduced the migration and proliferation of MSK-Leuk1 cells by 57% and 45%, respectively. Exposure of MSK-Leuk1 cells to estrogen inhibited apoptosis by 26%, whereas supplementation with the antiestrogen fulvestrant restored estrogen-dependent apoptosis. Representation of the estrogen pathway in human head and neck tissues from 128 patients was examined using tissue microarrays. The majority of the samples exhibited immunohistochemical staining for ERβ (91.9%), CYP1B1 (99.4%), and 17β-estradiol (88.4%). CYP1B1 and ERβ were elevated in HNSCCs relative to normal epithelium (P = 0.024 and 0.008, respectively). These data provide novel insight into the mechanisms underlying head and neck carcinogenesis and facilitate the identification of new targets for chemopreventive intervention.

Targeting apoptosis pathway with natural terpenoids: implications for treatment of breast and prostate cancer

Terpenoids represent a large and diverse class of naturally occurring compounds found in a variety of fruits, vegetables and medicinal plants. Structurally some of the terpenoids are similar to human hormones. A diet rich in terpenoids is inversely related with the risk of chronic diseases including cancers. Breast and prostate cancers are hormone-related diseases and the second leading cause of female and male cancer mortality. Diterpenoid paclitaxel, and its semi-synthetic analogue docetaxel, have entered clinical use against established breast and prostate cancers. Here we reviewed potential molecular targets and biological properties of natural terpenoids, including monoterpenoids, diterpenoids, triterpenoids and tetraterpenoids, and their applications in treatment of human breast and prostate cancers. These terpenoids are able to inhibit tumor cell proliferation and induce tumor cell death by inhibiting multiple cancer-specific targets including the proteasome, NF-kappaB, and antiapoptotic protein Bcl-2. The efficacy of these terpenoids against breast or prostate cancer cells, as demonstrated in pre-clinical studies support clinical application of these naturally occurring terpenoids in treatment of hormone-related human cancers.

Grape seed proanthocyanidin suppression of breast cell carcinogenesis induced by chronic exposure to combined 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and benzo[a]pyrene

Breast cancer is the most common type of cancer among women in northern America and northern Europe; dietary prevention is a cost-efficient strategy to reduce the risk of this disease. To identify dietary components for the prevention of human breast cancer associated with long-term exposure to environmental carcinogens, we studied the activity of grape seed proanthocyanidin extract (GSPE) in suppression of cellular carcinogenesis induced by repeated exposures to low doses of environmental carcinogens. We used combined carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), at picomolar concentrations, to repeatedly treat noncancerous, human breast epithelial MCF10A cells to induce cellular acquisition of cancer-related properties of reduced dependence on growth factors, anchorage-independent growth, and acinar-conformational disruption. Using these properties as biological target endpoints, we verified the ability of GSPE to suppress combined NNK- and B[a]P-induced precancerous cellular carcinogenesis and identified the minimal, noncytotoxic concentration of GSPE required for suppressing precancerous cellular carcinogenesis. We also identified that hydroxysteroid-11-beta-dehydrogenase 2 (HSD11B2) may play a role in NNK- and B[a]P-induced precancerous cellular carcinogenesis, and its expression may act as a molecular target endpoint in GSPE's suppression of precancerous cellular carcinogenesis. And, the ability of GSPE to reduce gene expression of cytochrome-P450 enzymes CYP1A1 and CYP1B1, which can bioactivate NNK and B[a]P, possibly contributes to the preventive mechanism for GSPE in suppression of precancerous cellular carcinogenesis. Our model system with biological and molecular target endpoints verified the value of GSPE for the prevention of human breast cell carcinogenesis induced by repeated exposures to low doses of multiple environmental carcinogens.

Effects of cigarette smoke on the human oral mucosal transcriptome

Use of tobacco is responsible for approximately 30% of all cancer-related deaths in the United States, including cancers of the upper aerodigestive tract. In the current study, 40 current and 40 age- and gender-matched never smokers underwent buccal biopsies to evaluate the effects of smoking on the transcriptome. Microarray analyses were carried out using Affymetrix HGU133 Plus 2 arrays. Smoking altered the expression of numerous genes: 32 genes showed increased expression and 9 genes showed reduced expression in the oral mucosa of smokers versus never smokers. Increases were found in genes involved in xenobiotic metabolism, oxidant stress, eicosanoid synthesis, nicotine signaling, and cell adhesion. Increased numbers of Langerhans cells were found in the oral mucosa of smokers. Interestingly, smoking caused greater induction of aldo-keto reductases, enzymes linked to polycyclic aromatic hydrocarbon-induced genotoxicity, in the oral mucosa of women than men. Striking similarities in expression changes were found in oral compared with the bronchial mucosa. The observed changes in gene expression were compared with known chemical signatures using the Connectivity Map database and suggested that geldanamycin, a heat shock protein 90 inhibitor, might be an antimimetic of tobacco smoke. Consistent with this prediction, geldanamycin caused dose-dependent suppression of tobacco smoke extract-mediated induction of CYP1A1 and CYP1B1 in vitro. Collectively, these results provide new insights into the carcinogenic effects of tobacco smoke, support the potential use of oral epithelium as a surrogate tissue in future lung cancer chemoprevention trials, and illustrate the potential of computational biology to identify chemopreventive agents.

Targeting tumor proteasome with traditional Chinese medicine

The proteasome is a multicatalytic protease complex whose activity is required for the growth of normal or tumor cells. It has been shown that human cancer cells are more sensitive to proteasome inhibition than normal cells, indicating that the proteasome could be a target of chemotherapy. Studies suggest that traditional Chinese medicine (TCM) is an effective approach for cancer treatment. Here we reviewed several TCMs for their potential in treatment of cancer. This short review focuses mainly on the TCMs that potentially target the tumor cellular proteasome and NF-kappaB pathway whose activation is dependent on the proteasome activity.

UVR exposure sensitizes keratinocytes to DNA adduct formation

UV radiation (UVR) and exposure to tobacco smoke, a source of polycyclic aromatic hydrocarbons (PAH), have been linked to skin carcinogenesis. UVR-mediated activation of the aryl hydrocarbon receptor (AhR) stimulates the transcription of CYP1A1 and CYP1B1, which encode proteins that convert PAH to genotoxic metabolites. We determined whether UVR exposure sensitized human keratinocytes to PAH-induced DNA adduct formation. UVR exposure induced CYP1A1 and CYP1B1 in HaCaT cells, an effect that was mimicked by photooxidized tryptophan (aTRP) and FICZ, a component of aTRP. UVR exposure or pretreatment with aTRP or FICZ also sensitized cells to benzo(a)pyrene (B[a]P)-induced DNA adduct formation. alphaNF, an AhR antagonist, suppressed UVR-, aTRP-, and FICZ-mediated induction of CYP1A1 and CYP1B1 and inhibited B[a]P-induced DNA adduct formation. Treatment with 17-AAG, an Hsp90 inhibitor, caused a marked decrease in levels of AhR; inhibited UVR-, aTRP-, and FICZ-mediated induction of CYP1A1 and CYP1B1; and blocked the sensitization of HaCaT cells to B[a]P-induced DNA adduct formation. FICZ has been suggested to be a physiologic ligand of the AhR that may have systemic effects. Hence, studies of FICZ were also carried out in MSK-Leuk1 cells, a model of oral leukoplakia. Pretreatment with alpha-naphthoflavone or 17-AAG blocked FICZ-mediated induction of CYP1A1 and CYP1B1, and suppressed the increased B[a]P-induced DNA adduct formation. Collectively, these results suggest that sunlight may activate AhR signaling and thereby sensitize cells to PAH-mediated DNA adduct formation. Antagonists of AhR signaling may have a role in the chemoprevention of photocarcinogenesis.

MicroRNA expression in squamous cell carcinoma and adenocarcinoma of the esophagus: associations with survival

PURPOSE

The dismal outcome of esophageal cancer patients highlights the need for novel prognostic biomarkers, such as microRNAs (miRNA). Although recent studies have established the role of miRNAs in esophageal carcinoma, a comprehensive multicenter study investigating different histologic types, including squamous cell carcinoma (SCC) and adenocarcinoma with or without Barrett's, is still lacking.

EXPERIMENTAL DESIGN

miRNA expression was measured in cancerous and adjacent noncancerous tissue pairs collected from 100 adenocarcinoma and 70 SCC patients enrolled at four clinical centers from the United States, Canada, and Japan. Microarray-based expression was measured in a subset of samples in two cohorts and was validated in all available samples.

RESULTS

In adenocarcinoma patients, miR-21, miR-223, miR-192, and miR-194 expression was elevated, whereas miR-203 expression was reduced in cancerous compared with noncancerous tissue. In SCC patients, we found elevated miR-21 and reduced miR-375 expression levels in cancerous compared with noncancerous tissue. When comparing cancerous tissue expression between adenocarcinoma and SCC patients, miR-194 and miR-375 were elevated in adenocarcinoma patients. Significantly, elevated miR-21 expression in noncancerous tissue of SCC patients and reduced levels of miR-375 in cancerous tissue of adenocarcinoma patients with Barrett's were strongly associated with worse prognosis. Associations with prognosis were independent of tumor stage or nodal status, cohort type, and chemoradiation therapy.

CONCLUSIONS

Our multicenter-based results highlight miRNAs involved in major histologic types of esophageal carcinoma and uncover significant associations with prognosis. Elucidating miRNAs relevant to esophageal carcinogenesis is potentially clinically useful for developing prognostic biomarkers and identifying novel drug targets and therapies.

HDAC6 modulates Hsp90 chaperone activity and regulates activation of aryl hydrocarbon receptor signaling

The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix family of transcription factors, binds with high affinity to polycyclic aromatic hydrocarbons (PAH) and the environmental toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin). Most of the biochemical, biological, and toxicological responses caused by exposure to PAHs and polychlorinated dioxins are mediated, at least in part, by the AhR. The AhR is a client protein of Hsp90, a molecular chaperone that can be reversibly acetylated with functional consequences. The main objective of this study was to determine whether modulating Hsp90 acetylation would affect ligand-mediated activation of AhR signaling. Trichostatin A and suberoylanilide hydroxamic acid, two broad spectrum HDAC inhibitors, blocked PAH and dioxin-mediated induction of CYP1A1 and CYP1B1 in cell lines derived from the human aerodigestive tract. Silencing HDAC6 or treatment with tubacin, a pharmacological inhibitor of HDAC6, also suppressed the induction of CYP1A1 and CYP1B1. Inhibiting HDAC6 led to hyperacetylation of Hsp90 and loss of complex formation with AhR, cochaperone p23, and XAP-2. Inactivation or silencing of HDAC6 also led to reduced binding of ligand to the AhR and decreased translocation of the AhR from cytosol to nucleus in response to ligand. Ligand-induced recruitment of the AhR to the CYP1A1 and CYP1B1 promoters was inhibited when HDAC6 was inactivated. Mutation analysis of Hsp90 Lys(294) shows that its acetylation status is a strong determinant of interactions with AhR and p23 in addition to ligand-mediated activation of AhR signaling. Collectively, these results show that HDAC6 activity regulates the acetylation of Hsp90, the ability of Hsp90 to chaperone the AhR, and the expression of AhR-dependent genes. Given the established link between activation of AhR signaling and xenobiotic metabolism, inhibitors of HDAC6 may alter drug or carcinogen metabolism.