Repression of Activated Aryl Hydrocarbon Receptor–Induced Transcriptional Activation by 5α-Dihydrotestosterone in Human Prostate Cancer LNCaP and Human Breast Cancer T47D Cells

Impact of benzo[a]pyrene, PCB153 and sex hormones on human ESC-Derived thyroid follicles using single cell transcriptomics

INTRODUCTION

Endocrine disruptors are compounds of manmade origin able to interfere with the endocrine system and constitute an important environmental concern. Indeed, detrimental effects on thyroid physiology and functioning have been described. Differences exist in the susceptibility of human sexes to the incidence of thyroid disorders, like autoimmune diseases or cancer.

METHODS

To study how different hormonal environments impact the thyroid response to endocrine disruptors, we exposed human embryonic stem cell-derived thyroid organoids to physiological concentrations of sex hormones resembling the serum levels of human females post-ovulation or males of reproductive age for three days. Afterwards, we added 10 µM benzo[a]pyrene or PCB153 for 24 h and analyzed the transcriptome changes via single-cell RNA sequencing with differential gene expression and gene ontology analysis.

RESULTS

The sex hormones receptors genes AR, ESR1, ESR2 and PGR were expressed at low levels. Among the thyroid markers, only TG resulted downregulated by benzo[a]pyrene or benzo[a]pyrene with the "male" hormones mix. Both hormone mixtures and benzo[a]pyrene alone upregulated ribosomal genes and genes involved in oxidative phosphorylation, while their combination decreased the expression compared to benzo[a]pyrene alone. The "male" mix and benzo[a]pyrene, alone or in combination, upregulated genes involved in lipid transport and metabolism (APOA1, APOC3, APOA4, FABP1, FABP2, FABP6). The combination of "male" hormones and benzo[a]pyrene induced also genes involved in inflammation and NFkB targets. Benzo[a]pyrene upregulated CYP1A1, CYP1B1 and NQO1 irrespective of the hormonal context. The induction was stronger in the "female" mix. Benzo[a]pyrene alone upregulated genes involved in cell cycle regulation, response to reactive oxygen species and apoptosis. PCB153 had a modest effect in presence of "male" hormones, while we did not observe any changes with the "female" mix.

CONCLUSION

This work shows how single cell transcriptomics can be applied to selectively study the in vitro effects of endocrine disrupters and their interaction with different hormonal contexts.

FDI-6, a FOXM1 inhibitor, activates the aryl hydrocarbon receptor and suppresses tumorsphere formation

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is activated by environmental contaminants such as dioxins and polycyclic aromatic hydrocarbons. Following ligand binding, AhR binds to xenobiotic responsive elements and modulates the transcription of AhR target genes. Multiple studies have shown that AhR plays important roles in a range of cancer cells and is attracting attention as a therapeutic target for cancer treatment. We have previously reported that AhR agonists inhibit tumorsphere formation in an AhR-dependent manner in the MCF-7 breast cancer cell line. In the present study, we found that FDI-6, an inhibitor of the transcription factor Forkhead Box M1 (FOXM1) induced the mRNA expression of AhR target genes, nuclear translocation of AhR, and transcriptional activity of AhR. In addition, FDI-6 dose-dependently reduced the mRNA expression of FOXM1-regulated genes in AhR-expressing MCF-7 cells, although not in AhR-deficient MCF-7 cells. Furthermore, FDI-6 was found to suppress tumorsphere formation via the AhR in MCF-7 cells and HepG2 human liver cancer cell line. On the basis of the findings of this study, we show that FDI-6, a FOXM1 inhibitor, functions as an AhR agonist, and suppresses tumorsphere formation via the AhR.

The Impact of Indoles Activating the Aryl Hydrocarbon Receptor on Androgen Receptor Activity in the 22Rv1 Prostate Cancer Cell Line

The activation of the aryl hydrocarbon receptor (AhR) by xenobiotic compounds was demonstrated to result in the degradation of the androgen receptor (AR). Since prostate cancer is often dependent on AR, it has become a significant therapeutic target. As a result of the emerging concept of bacterial mimicry, we tested whether compounds with indole scaffolds capable of AhR activation have the potential to restrict AR activity in prostate cancer cells. Altogether, 22 indolic compounds were tested, and all of them activated AhR. However, only eight decreased DHT-induced AR luciferase activity. All indoles, which met the AhR-activating and AR-suppressing criteria, decreased the expression of DHT-inducible AR target genes, specifically KLK3 and FKBP5 mRNAs. The reduced AR binding to the KLK3 promoter was confirmed by a chromatin immunoprecipitation (ChIP) assay. In addition, some indoles significantly decreased AR protein and mRNA level. By using CRISPR/Cas9 AhR knockout technology, no relationship between AhR and AR, measured as target gene expression, was observed. In conclusion, some indoles that activate AhR possess AR-inhibiting activity, which seems to be related to the downregulation of AR expression rather than to AR degradation alone. Moreover, there does not seem to be a clear relationship that would connect AhR activation with AR activity suppression in 22Rv1 cells.

Antiandrogenic and Estrogenic Activity Evaluation of Oxygenated and Nitrated Polycyclic Aromatic Hydrocarbons Using Chemically Activated Luciferase Expression Assays

To establish the risk of the endocrine disrupting activity of polycyclic aromatic compounds, especially oxygenated and nitrated polycyclic aromatic hydrocarbons (oxy-PAHs and nitro-PAHs, respectively), antiandrogenic and estrogenic activities were determined using chemically activated luciferase expression (CALUX) assays with human osteoblast sarcoma cells. A total of 27 compounds including 9 oxy-PAHs (polycyclic aromatic ketones and quinones) and 8 nitro-PAHs was studied. The oxy-PAHs of 7H-benz[de]anthracen-7-one (BAO), 11H-benzo[a]fluoren-11-one (B[a]FO), 11H-benzo[b]fluoren-11-one (B[b]FO), and phenanthrenequinone (PhQ) exhibited significantly the potent inhibition of AR activation. All nitro-PAHs exhibited high antiandrogenic activities (especially high for 3-nitrofluoranthene (3-NFA) and 3-nitro-7H-benz[de]anthracen-7-one (3-NBAO)), and the AR inhibition was confirmed as noncompetitive for 3-NFA, 3-NBAO, and 1,3-dinitropyrene (1,3-DNPy). Antiandrogenic activity of 3-NFA demonstrated characteristically a U-shaped dose-response curve; however, the absence of fluorescence effect on the activity was confirmed. The prominent estrogenic activity dependent on dose-response curve was confirmed for 2 oxy-PAHs (i.e., B[a]FO and B[b]FO). Elucidating the role of AR and ER on the effects of polycyclic aromatic compounds (e.g., oxy- and nitro-PAHs) to endocrine dysfunctions in mammals and aquatic organisms remains a challenge.

Aryl Hydrocarbon Receptor Directly Regulates VTCN1 Gene Expression in MCF-7 Cells

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates the toxicity of dioxins and polycyclic aromatic hydrocarbons. Recent studies have suggested that AhR is involved in cancer immunity. In the present study, we examined whether AhR regulates the expression of immune checkpoint genes in breast cancer cells. We discovered that the mRNA expression of V-set domain containing T cell activation inhibitor 1 (VTCN1) that negatively regulates T cell immunity was upregulated by AhR agonists in breast cancer cell lines, MCF-7 and T47D. Furthermore, AhR knockout or knockdown experiments clearly demonstrated that upregulation of VTCN1 gene expression by 3-methylcholanthrene was AhR dependent. Luciferase reporter and chromatin immunoprecipitation assays revealed that this upregulation of VTCN1 gene expression was induced by the recruitment of AhR to the AhR responsive element in the VTCN1 gene promoter in MCF-7 cells. Taken together, AhR directly regulates VTCN1 gene expression in MCF-7 cells.

Camalexin, an indole phytoalexin, inhibits cell proliferation, migration, and mammosphere formation in breast cancer cells via the aryl hydrocarbon receptor

Breast cancer is the most commonly diagnosed cancer among women worldwide. Despite a variety of drugs available for the treatment of patients with breast cancer, drug resistance remains a significant clinical problem. Therefore, there is an urgent need to develop drugs with new mechanisms of action. Camalexin is the main indole phytoalexin in Arabidopsis thaliana and other crucifers. Camalexin inhibits the proliferation of various cancer cells. However, the mechanism by which camalexin inhibits cell proliferation remains unclear. In this study, we found that camalexin inhibited cell proliferation and migration of breast cancer cell lines. Furthermore, camalexin also suppressed breast cancer stem cell-derived mammosphere formation. We previously reported that the ligand-activated transcription factor aryl hydrocarbon receptor (AhR) agonist suppresses mammosphere formation. Several compounds with indole structures are known to act as AhR agonists. Therefore, we hypothesized that the inhibition of mammosphere formation by camalexin may involve AhR activation. We found that camalexin increased the nuclear translocation of AhR, AhR-mediated transcriptional activation, and expression of AhR target genes. In addition, camalexin suppressed mammosphere formation in AhR-expressing breast cancer cells more than in the breast cancer cells that lacked AhR expression. Taken together, the data demonstrate that camalexin is a novel AhR agonist and that the inhibition of cell proliferation, migration, and mammosphere formation by camalexin involves the activation of AhR. Our findings suggest that camalexin, an AhR agonist, may be a novel therapeutic agent for breast cancer.

Association Between Polycystic Ovary Syndrome and the Polymorphisms of Aryl Hydrocarbon Receptor Repressor, Glutathione-S-transferase T1, and Glutathione-S-transferase M1 Genes

OBJECTIVE

To investigate the association between the aryl hydrocarbon receptor repressor (AhRR) C/G polymorphisms and glutathione-S-transferase M1 (GSTM1) and GSTT1 null mutation and the risk of polycystic ovary syndrome (PCOS) in Korean women.

METHODS

This was a case-control study of 478 women with PCOS and 376 aged-matched healthy controls. Genotyping of the AhRR C/G polymorphism and GSTM1 and GSTT1 were performed using real-time PCR analysis and multiplex PCR, respectively.

RESULTS

The genotype distribution of the AhRR C/G polymorphisms and GSTM1/GSTT1 null mutations did not differ between women with PCOS and controls. Using the wild-type combined AhRR CC and GSTT1 present genotype as a reference, the odds that a woman had PCOS were 1.54 (95% CIs 1.04-2.29) times higher if she had a combined AhRR CG or GG and GSTT1 null genotype. The odds that a woman had PCOS was 1.48 (95% CIs 1.08-2.04) times higher if she had a combined GSTM1/GSTT1 null genotype compared with the wild-type combined GSTM1/GSTT1 present genotype. However, there were no significant associations between the risk of PCOS and any combined AhRR and GSTM1.

CONCLUSIONS

Our data suggest that a combined AhRR CG or GG and GSTT1 null genotype or a combined GSTT1/GSTM1 null genotype might be associated with an increased risk of PCOS.

Anti-androgenic effect of astaxanthin in LNCaP cells is mediated through the aryl hydrocarbon-androgen receptors cross talk

The aim of this study was to investigate the anti-androgenic effects of astaxanthin (AST) on human prostatic cancer cell growth, and its impact on androgen receptor (AR) signaling using prostate cancer (PCa) cell line LNCaP. LNCaP cells were treated with AST alone and in combination with CH223191 and flutamide (Flu) in the presence and absence of testosterone. MTT assay, cellular prostate-specific antigen (PSA) and dihydrotestosterone (DHT) production, mRNA levels of CYP1A1, PSA, Kallikrein-Related Peptidase 2 (KLK2), Transmembrane Serine Protease 2 (TMPRSS2), and AR genes were measured as endpoints. The expression of CYP1A1, PSA, KLK2, TMPRSS2, and AR mRNA levels was decreased which results in reducing the production of PSA and DHT in the presence of testosterone. Our data clearly demonstrate that AST has a potential ability to suppress the human prostate LNCaP cells growth at high concentrations. AST was able to repress the testosterone-induced transcription of AR-target genes. PRACTICAL APPLICATIONS: Astaxanthin is a natural compound with the most potent antioxidant activity among other antioxidants. In the current study, ASX suppressed the LNCaP cells at high concentrations. Furthermore, AST inhibited testosterone-induced transcriptional activation of androgen-related genes. AST induced the expression of CYP1A1, which is able to metabolize the steroid hormones. It seems that AST can act as AhR exogenous ligand by induction of CYP1A1, which results in testosterone metabolism and consequent suppression of AR genes. So that, AST could prevent the growth of testosterone-dependent PCa cells, downregulate downstream genes in testosterone pathways, and enhance the metabolism of testosterone via AhR pathway. Collectively, AST could be considered as a potential candidate for the treatment of PCa.

The Activation of Procarcinogens by CYP1A1/1B1 and Related Chemo-Preventive Agents: A Review

CYP1A1 and CYP1B1 are extrahepatic P450 family members involved in the metabolism of procarcinogens, such as PAHs, heterocyclic amines and halogen-containing organic compounds. CYP1A1/1B1 also participate in the metabolism of endogenous 17-β-estradiol, producing estradiol hydroquinones, which are the intermediates of carcinogenic semiquinones and quinones. CYP1A1 and CYP1B1 proteins share approximately half amino acid sequence identity but differ in crystal structures. As a result, CYP1A1 and CYP1B1 have different substrate specificity to chemical procarcinogens. This review will introduce the general molecular biology knowledge of CYP1A1/1B1 and the metabolic processes of procarcinogens regulated by these two enzymes. Over the last four decades, a variety of natural products and synthetic compounds which interact with CYP1A1/1B1 have been identified as effective chemo-preventive agents against chemical carcinogenesis. These compounds are mainly classified as indirect or direct CYP1A1/1B1 inhibitors based on their distinct mechanisms. Indirect CYP1A1/1B1 inhibitors generally impede the transcription and translation of CYP1A1/1B1 genes or interfere with the translocation of aryl hydrocarbon receptor (AHR) from the cytosolic domain to the nucleus. On the other hand, direct inhibitors inhibit the catalytic activities of CYP1A1/1B1. Based on the structural features, the indirect inhibitors can be categorized into the following groups: flavonoids, alkaloids and synthetic aromatics, whereas the direct inhibitors can be categorized into flavonoids, coumarins, stilbenes, sulfur containing isothiocyanates and synthetic aromatics. This review will summarize the in vitro and in vivo activities of these chemo-preventive agents, their working mechanisms, and related SARs. This will provide a better understanding of the molecular mechanism of CYP1 mediated carcinogenesis and will also give great implications for the discovery of novel chemo-preventive agents in the near future.

Expression analysis of aryl hydrocarbon receptor repressor (AHRR) gene in gallbladder cancer

BACKGROUND

The aryl hydrocarbon receptor repressor (AHRR), a member of the growing superfamily, is a basic helix-loop-helix/PerAHR nuclear translocator (ARNT)-Sim (bHLH-PAS) protein. AHRR has been proposed to function as a putative new tumor suppressor gene based on studies in multiple types of human cancers. This current study aims to investigate AHHR expression and its prognostic significance in gallbladder cancer.

METHODS

The study includes 48 gallbladder cancer and 34 chronic cholecystitis cases as controls. The expression level of AHRR was analyzed by using semi-quantitative PCR and immunohistochemical staining. The results were correlated with different clinical parameters.

RESULTS

We demonstrate that the expression of AHRR is significantly down-regulated in gallbladder cancer tissue samples as compared to that in chronic cholecystitis tissue samples by reverse transcriptase PCR (RT-PCR) (P = 0.017) and immunohistochemistry analysis (P = 0.002). Interestingly, our RT-PCR data revealed that AHRR mRNA expression is frequently down-regulated (45.8%; 22/48) in cases as compared to 14.7% (5/34) in controls. Similarly, immunohistochemical analysis data show significant down-regulation of AHRR expression in 77.1% (37/48) of gallbladder cancer cases than 44.1% (15/34) in controls (P < 0.017). Reduced mRNA and protein expression is significantly associated with advanced T-stage (P = 0.001), histological differentiation (P = 0.001), and tumors with nodal metastasis (P = 0.001). Decreased expression of AHRR is significantly associated with poor prognosis in gallbladder cancer patients.

CONCLUSION

In conclusion, the present study suggests that low AHRR expression may be critical in gallbladder cancer development. Our data suggests that AHRR may act as a tumor suppressor gene and its expression profile may be useful as a diagnostic marker in gallbladder cancer.

An androgen-independent mechanism underlying the androgenic effects of 3-methylcholanthrene, a potent aryl hydrocarbon receptor agonist

Aryl hydrocarbon receptor (AhR) and androgen receptor (AR) are ligand-activated transcription factors with profound cross-talk between their signal transduction pathways. Previous studies have shown that AhR agonists activate the transcription of AR-regulated genes in an androgen-independent manner; however, the underlying mechanism remains unclear. To decipher this mechanism, we evaluated the effects of 3-methylcholanthrene (3MC), a potent AhR agonist, on the transcription of AR-regulated genes in three AR-expressing cell lines. 3MC induced the expression of not only three representative AR-regulated chromosomal genes but also the exogenous AR-responsive luciferase reporter gene. No significant difference in the 3MC-induced luciferase activity was detected in the presence of SKF-525A, a non-specific inhibitor of CYP enzymes. The androgenic effects of 3MC were diminished by AhR and AR knockdown. Following 3MC treatment, the amount of nuclear AhR and AR increased synchronously. Co-immunoprecipitation revealed that AhR and AR formed a complex in the nucleus of cells treated with 3MC. AR was recruited to the proximal promoter and distal enhancer regions of the PSA gene upon the addition of 3MC. We propose that AhR activated by 3MC forms a complex with unliganded AR which translocates from the cytoplasm to the nucleus. Nuclear AR now binds the transcriptional regulatory region of AR-regulated genes and activates the transcription.

Anti-androgenic effect of 6-formylindolo[3,2-b]carbazole (FICZ) in LNCaP cells is mediated by the aryl hydrocarbon-androgen receptors cross-talk

The factual impact of endogenously activated AHR by 6-formylindolo[3,2-b]carbazole (FICZ), an endogenous ligand of AHR on androgen receptor (AR) was aim of this study. In this study, LNCaP cells were exposed to FICZ, CH223191 and flutamide (Flu) alone or in combination in the presence and absence of testosterone. CYP1A1 enzyme activity, cell viability, cellular prostate-specific antigen (PSA) and dihydrotestosterone (DHT) production, mRNA levels of PSA, KLK2, TMPRSS2, and AR genes were measured as endpoints. A declining in the expression of androgen- responsive target genes was seen by either Flu or FICZ in the presence of testosterone. Furthermore, the forced decrease in the expression of AR target genes resulted in 41% and 31% decline in the DHT and PSA concentrations respectively. Taken together, endogenously activated AHR plays a regulatory role on AR. Therefore, FICZ might be an effective chemical in treating prostate cancer.

Identification of a Radiosensitivity Molecular Signature Induced by Enzalutamide in Hormone-sensitive and Hormone-resistant Prostate Cancer Cells

Prostate cancer (PCa) is the most common cancer amongst men. A novel androgen receptor (AR) antagonist, enzalutamide (ENZA) has recently been demonstrated to enhance the effect of radiation (XRT) by impairing the DNA damage repair process. This study aimed to identify a radiosensitive gene signature induced by ENZA in the PCa cells and to elucidate the biological pathways which influence this radiosensitivity. We treated LNCaP (AR-positive, hormone-sensitive PCa cells) and C4-2 (AR-positive, hormone-resistant PCa cells) cells with ENZA alone and in combination with androgen deprivation therapy (ADT) and XRT. Using one-way ANOVA on the gene expression profiling, we observed significantly differentially expressed (DE) genes in inflammation-and metabolism-related genes in hormone-sensitive and hormone-resistant PCa cell lines respectively. Survival analysis in both the TCGA PRAD and GSE25136 datasets suggested an association between the expression of these genes and time to recurrence. These results indicated that ENZA alone or in combination with ADT enhanced the effect of XRT through immune and inflammation-related pathways in LNCaP cells and metabolic-related pathways in C4-2 cells. Kaplan–Meier analysis and Cox proportional hazard models showed that low expression of all the candidate genes except for PTPRN2 were associated with tumor progression and recurrence in a PCa cohort.

Short androgen receptor poly-glutamine-promoted endometrial cancer is associated with benzo[a]pyrene-mediated aryl hydrocarbon receptor activation

The androgen receptor (AR) poly‐glutamine polymorphism (AR‐Q) was reported to play role in endometrial cancer (EMCA) development, yet controversial. Environmental factors interact with genetic variation have been reported in EMCA. Aerosol toxins, polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP), are EMCA facilitators. This report examined the interplay between AR‐Qs and BaP in EMCA. During analysing patient AR‐Q polymorphism and Aryl hydrocarbon Receptor (AhR) expressions, we found overall survival (OS) benefit is ascending with AR‐Q lengths (5‐year OS of 61.3% in Q length <20 and 88% in Q length >23). And AhR is higher expressed in short AR‐Q tumour compared to that in long AR‐Q patient. In vitro study found androgen‐response element (ARE) activity descends with AR‐Qs length (Q13 > Q25 > Q35), whereas BaP suppresses ARE activities in EMCA cells. Furthermore, AR‐Q13 (but not AR‐Q25, or ‐35) enhances BaP‐induced dioxin‐responsive element (DRE) activity. Lastly, AR‐Q13 exerts higher colony‐forming capacity than other AR‐Qs, and knock‐down AhR abolished AR‐Q13‐mediated colony numbers. This study demonstrated a possible interaction of gene (AR‐Q polymorphism) and environmental toxins (e.g. BaP) to affect cancer progression. A large‐scale epidemiology and public health survey on the interaction of environmental toxin and AR poly‐Q in EMCA is suggested.

Downregulation of ARNT2 promotes tumor growth and predicts poor prognosis in human hepatocellular carcinoma

BACKGROUND AND AIM

Aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) is a transcriptional regulator and member of the basic helix-loop-helix/Per-ARNT-SIM (bHLH/PAS) superfamily. Recently, evidence of that ARNT is involved in carcinogenesis and cancer progression has emerged. The aim of current study was to investigate the role of ARNT2, a homolog of ARNT, in tumor growth, invasion, and prognosis of hepatocellular carcinoma (HCC).

METHODS

Tissue microarray and immunohistochemical staining were used to examine the expression of ARNT2 in 195 HCC tissues. Factors associated with ARNT2 levels were assessed by univariate and multivariate Cox regression analyses. Cell proliferation, migration, and invasion assays were performed by using ARNT2 silencing and overexpressing HCCLM6 cell line. Orthotopic xenograft HCC model was used to elucidate the effects of ARNT2 on HCC progression in vivo.

RESULTS

High intratumoral of ARNT2 level was well correlated with longer overall survival (OS) and lower tumor to recurrence (TTR) of HCC patients after resection. Multivariate analysis revealed that intratumoral ARNT2 overexpression was an independent prognostic factor for both OS and TTR. Knockdown of ARNT2 in HCCLM6 cells was significantly enhanced while overexpression of ARNT2 significantly inhibited the ability of cell proliferation, invasion, and migration. In animal studies, downregulation of ARNT2 in HCCLM6 cells promoted, whereas upregulation of ARNT2 in HCCLM6 cells reduced HCCLM6 growth in vivo.

CONCLUSIONS

Our data demonstrate that ARNT2 plays an inhibitory role in HCC progression and suggest that ARNT2 may be a potential prognostic predictor and therapeutic target for HCC.

Gene-environment interactions in male reproductive health: special reference to the aryl hydrocarbon receptor signaling pathway

Over the last few decades, there have been numerous reports of adverse effects on the reproductive health of wildlife and laboratory animals caused by exposure to endocrine disrupting chemicals (EDCs). The increasing trends in human male reproductive disorders and the mounting evidence for causative environmental factors have therefore sparked growing interest in the health threat posed to humans by EDCs, which are substances in our food, environment and consumer items that interfere with hormone action, biosynthesis or metabolism, resulting in disrupted tissue homeostasis or reproductive function. The mechanisms of EDCs involve a wide array of actions and pathways. Examples include the estrogenic, androgenic, thyroid and retinoid pathways, in which the EDCs may act directly as agonists or antagonists, or indirectly via other nuclear receptors. Dioxins and dioxin-like EDCs exert their biological and toxicological actions through activation of the aryl hydrocarbon-receptor, which besides inducing transcription of detoxifying enzymes also regulates transcriptional activity of other nuclear receptors. There is increasing evidence that genetic predispositions may modify the susceptibility to adverse effects of toxic chemicals. In this review, potential consequences of hereditary predisposition and EDCs are discussed, with a special focus on the currently available publications on interactions between dioxin and androgen signaling.

Bioactive components of Glycyrrhiza uralensis mediate drug functions and properties through regulation of CYP450 enzymes

Glycyrrhiza uralensis (G. uralensis) is a common medicinal plant that has mainly been used to modulate the pharmaceutical activity of herbal medicines. Although G. uralensis has been shown to affect the expression and activity of the key metabolic enzyme cytochrome P450 (CYP450), the detailed mechanism of this process has yet to be elucidated. The present study aimed to elucidate the effects of bioactive components of G. uralensis on different isoforms of CYP450 and determine the ability of these components to modulate drug properties. In the present study, mRNA levels of CYP1A2, CYP2D6, CYP2E1, and CYP3A4 were investigated by quantitative polymerase chain reaction (qPCR) in HepG2 cells following treatment with the major bioactive compounds of G. uralensis. The activity of CYP450 enzymes was investigated in human liver microsomes using the cocktail probe drug method, and the metabolites of specific probes were detected by UPLC‑MS/MS. The effects of G. uralensis on CYP450 were assessed using bioinformatics network analysis. Several compounds from G. uralensis had various effects on the expression and activity of multiple CYP450 isoforms. The majority of the compounds analysed the inhibited expression of CYP2D6 and CYP3A4. Several CYP isoforms were differentially modulated depending on the specific compound and dose tested. In conclusion, the present study suggested that G. uralensis influenced the expression and activity of CYP450 enzymes. Therefore, caution should be taken when G. uralensis is co‑administered with drugs that are known to be metabolized by CYP450. This study contributed to the knowledge of the mechanisms by which this medicinal plant, commonly known as licorice, modulates drug efficacy.

The aryl hydrocarbon receptor is constitutively active in advanced prostate cancer cells

Background

Distant prostate cancers are commonly hormone refractory and exhibit increased growth no longer inhibited by androgen deprivation therapy. Understanding all molecular mechanisms contributing to uncontrolled growth is important to obtain effective treatment strategies for hormone refractory prostate cancers (HRPC). The aryl hydrocarbon receptor (AhR) affects a number of biological processes including cell growth and differentiation. Several studies have revealed that exogenous AhR ligands inhibit cellular proliferation but recent evidence suggests AhR may possess intrinsic functions that promote cellular proliferation in the absence of exogenous ligands.

Methods/Results

qRT-PCR and western blot analysis was used to determine AhR mRNA and protein expression in hormone sensitive LNCaP cells as well as hormone refractory DU145, PC3 and PC3M prostate cancer cell lines. LNCaP cells express AhR mRNA and protein at a much lower level than the hormone refractory cell models. Cellular fractionation and immunocytochemistry revealed nuclear localization of AhR in the established hormone refractory cell lines while LNCaP cells are devoid of nuclear AhR protein. qRT-PCR analysis used to assess basal CYP1B1 levels and a xenobiotic responsive element binding assay confirmed ligand independent transcriptional activity of AhR in DU145, PC3 and PC3M cells. Basal CYP1B1 levels were decreased by treatment with specific AhR inhibitor, CH223191. An in vitro growth assay revealed that CH223191 inhibited growth of DU145, PC3 and PC3M cells in an androgen depleted environment. Immunohistochemical staining of prostate cancer tissues revealed increased nuclear localization of AhR in grade 2 and grade 3 cancers compared to the well differentiated grade 1 cancers.

Conclusions

Together, these results show that AhR is constitutively active in advanced prostate cancer cell lines that model hormone refractory prostate cancer. Chemical ablation of AhR signaling can reduce the growth of advanced prostate cancer cells, an effect not achieved with androgen receptor inhibitors or growth in androgen depleted media.

Biomarkers of sensitivity to potent and selective antitumor 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F203) in ovarian cancer

2-(4-Amino-3-methylphenyl)-5-fluorobenzothiazole (5F203, NSC 703786) lysylamide belongs to a novel mechanistic class of antitumor agents. It elicits activity against ovarian, breast, kidney and colorectal cancer models. In sensitive breast cancer cells, 5F203 activates aryl hydrocarbon receptor (AhR) signaling. Herein, we evaluate the role of AhR in 5F203 activity in two ovarian cancer cell lines: IGROV-1 (sensitive to 5F203), SKOV-3 (resistant to this agent). In addition, cancer cells have been isolated from ascites fluid of ovarian cancer patients; sensitivity to 5F203 and concurrent AhR signal transduction has been examined in ascites-isolated ovarian cancer patients' cells. 5F203 induced enhanced CYP1A1 expression, AhR translocation and ROS formation in IGROV-1 cells and ascites-isolated ovarian cancer cells that were sensitive to 5F203. In IGROV-1 cells 5F203-induced ROS formation was accompanied by JNK, ERK and P38MAPK phosphorylation, DNA damage and cell cycle arrest prior to apoptosis. In contrast, 5F203 failed to induce CYP1A1 expression, AhR translocation or oxidative stress in 5F203-resistant SKOV-3 cells, or in ovarian cancer ascites cells inherently resistant to this agent. We propose that AhR may represent a new molecular target in the treatment of ovarian tumors and 5F203 may exemplify a potential novel treatment. Furthermore, putative biomarkers of sensitivity to this agent have been identified.

Poor prognosis of gastric adenocarcinoma with decreased expression of AHRR

Background

The aryl hydrocarbon receptor (AHR) repressor (AHRR), a member of growing superfamily, is a basic-helix-loop-helix/Per-AHR nuclear translocator (ARNT)-Sim (bHLH-PAS) protein. Recently, AHRR has been proposed to function as a putative new tumor suppressor gene based on some relevant studies in multiple types of human cancers. This current study aims to investigate AHHR expression and its prognostic significance in primary gastric adenocarcinoma.

Methodology/Principal Findings

The expression level of AHRR was analyzed using real-time quantitative PCR (RT-qPCR), western blotting, and immunohistochemical staining. It was clearly showed that the expression status of AHRR was reduced in tumor tissue samples compared with that in matched adjacent non-tumor tissue samples by RT-qPCR (P = 0.0423) and western blotting analysis (P = 0.004). Moreover, data revealed that AHRR without exon 8 (the active isoform) was the predominant form either in tumor tissues (66.7%, 8/12) or in matched adjacent non-tumor tissues (100.0%, 12/12), and the mRNA level of this isoform was significantly reduced in tumor tissues (P = 0.006). Immunohistochemistry analysis indicated that AHRR expression was significantly decreased in 175 of 410 (42.7%) gastric adenocarcinoma cases. Kaplan-Meier survival curves and Multivariate Cox analysis revealed that decreased expression of AHRR was significantly associated with poor prognosis in gastric adenocarcinoma patients.

Conclusions/Significance

Our data suggests that, in primary gastric adenocarcinoma, AHRR may play as a suppressor gene and its expression status has the potential to be an independent prognostic factor.

Dihydrotestosterone inhibits hair growth in mice by inhibiting insulin-like growth factor-I production in dermal papillae

We demonstrated that insulin-like growth factor-I (IGF-I) production in dermal papillae was increased and hair growth was promoted after sensory neuron stimulation in mice. Although the androgen metabolite dihydrotestosterone (DHT) inhibits hair growth by negatively modulating growth-regulatory effects of dermal papillae, relationship between androgen metabolism and IGF-I production in dermal papillae is not fully understood. We examined whether DHT inhibits IGF-I production by inhibiting sensory neuron stimulation, thereby preventing hair growth in mice. Effect of DHT on sensory neuron stimulation was examined using cultured dorsal root ganglion (DRG) neurons isolated from mice. DHT inhibits calcitonin gene-related peptide (CGRP) release from cultured DRG neurons. The non-steroidal androgen-receptor antagonist flutamide reversed DHT-induced inhibition of CGRP release. Dermal levels of IGF-I and IGF-I mRNA, and the number of IGF-I-positive fibroblasts around hair follicles were increased at 6h after CGRP administration. DHT administration for 3weeks decreased dermal levels of CGRP, IGF-I, and IGF-I mRNA in mice. Immunohistochemical expression of IGF-I and the number of proliferating cells in hair follicles were decreased and hair re-growth was inhibited in animals administered DHT. Co-administration of flutamide and CGRP reversed these changes induced by DHT administration. These observations suggest that DHT may decrease IGF-I production in dermal papillae by inhibiting sensory neuron stimulation through interaction with the androgen receptor, thereby inhibiting hair growth in mice.

[Sex- and species-differences on xenobiotic-induced toxicity: differences in constitutive and xenobiotic-mediated expression of cytochrome P450 1A subfamily enzymes (CYP1As)]

Cytochrome P450 1A subfamily enzymes (CYP1As) are important molecules in the metabolic activation of carcinogens such as polycyclic aromatic hydrocarbons and heterocyclic amines and are induced by their substrate exposure. There are species, sex, and organ differences in the induction of CYP1As, and susceptibilities to carcinogens are closely related to the constitutive and carcinogen-induced levels of CYP1As in target organs of experimental rodents. In this study, we investigated the induction of CYP1As and their species or sex differences after treatment with various chemicals using experimental animals and cultured cell lines. We found that: 1) newly established reporter cell lines, HepG2-A10 and KanR2-XL8, can be used for determining of activation of the aryl hydrocarbon receptor (AhR), a key transcription factor in the expression of CYP1As; 2) monocyclic aromatic amine (2-methoxy-4-nitroaniline) induced hepatic CYP1As in rats but not in other rodents in an AhR-independent manner; 3) androgen suppressed the constitutive expression or heterocyclic aromatic amine (Trp-P-1)-dependent induction of these enzymes in pigs and mice; and 4) nicardipine, a dihydropyridine calcium channel blocker, increased hepatic CYP1A expression in rats and augmented 3-methylcholanthrene-mediated induction of CYP1As and DNA-adduct formation in HepG2 cells. These findings indicate that there are species or sex differences in the induction of hepatic CYP1As via AhR-independent and unexplained transcriptional mechanisms. The elucidation of these mechanisms will aid in finding new predictors or developing new prevention strategies for chemical-induced carcinogenesis.

Isoform distinct time-, dose-, and castration-dependent alterations in flavin-containing monooxygenase expression in mouse liver after 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment

Flavin-containing monooxygenase (FMO) expression in male mouse liver is altered after 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure or castration. Because TCDD is slowly eliminated from the body, we examined hepatic Fmo mRNA alterations for up to 32 days following 10 or 64 microg/kg TCDD exposure by oral gavage in male C57BL/6J mice. Fmo2 mRNA was significantly induced at 1, 4, and 8 days whereas Fmo3 mRNA was also induced at 32 days relative to controls. Fmo3 mRNA levels exhibited a dose-dependent increase at 4, 8, and 32 days after exposure; Fmo1, Fmo4, and Fmo5 mRNA did not exhibit clear trends. Because castration alone also increased Fmo2, Fmo3, and Fmo4 mRNA we examined the combined effects of castration and TCDD treatment on FMO expression. A greater than additive effect was observed with Fmo2 and Fmo3 mRNA expression. Fmo2 mRNA exhibited a 3-5-fold increase after castration or 10 microg/kg TCDD exposure by oral gavage, whereas an approximately 20-fold increase was observed between the sham-castrated control and castrated TCDD-treated mice. Similarly, treatment with 10 microg/kg TCDD alone increased Fmo3 mRNA 130- and 180-fold in the sham-castrated and castrated mice compared to their controls respectively, whereas, Fmo3 mRNA increased approximately 1900-fold between the sham control and castrated TCDD-treated mice. An increase in hepatic Fmo3 protein in TCDD-treated mice was observed by immunoblotting and assaying methionine S-oxidase activity. Collectively, these results provide evidence for isoform distinct time-, dose-, and castration-dependent effects of TCDD on FMO expression and suggest cross-talk between TCDD and testosterone signal transduction pathways.