The cooked meat-derived mammary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) elicits estrogenic-like microRNA responses in breast cancer cells

MicroRNA in cardiometabolic health and disease: The perspectives of sex, gender and personalised medicine

BACKGROUND

Personalized medicine represents a novel and integrative approach that focuses on an individual's genetics and epigenetics, precision medicine, lifestyle and exposures as key players of health status and disease phenotypes.

METHODS

In this narrative review, we aim to carefully discuss the current knowledge on gender disparities in cardiometabolic diseases, and we consider the sex- specific expression of miRNAs and their role as promising tool in precision medicine.

RESULTS

Personalised medicine overcomes the restricted care of patient based on a binomial sex approach, by enriching itself with a holistic and dynamic gender integration. Recognized as a major worldwide health emergency, cardiometabolic disorders continue to rise, impacting on health systems and requiring more effective and targeted strategies. Several sex and gender drivers might affect the onset and progression of cardiometabolic disorders in males and females at multiple levels. In this respect, distinct contribution of genetic and epigenetic mechanisms, molecular and physiological pathways, sex hormones, visceral fat and subcutaneous fat and lifestyle lead to differences in disease burden and outcomes in males and females.

CONCLUSIONS

Sex and gender play a pivotal role in precision medicine because the influence the physiology of each individual and the way they interact with environment from intrauterine life.

Tumour Necrosis Factor-Alpha (TNF-α)-Induced Metastatic Phenotype in Colorectal Cancer Epithelial Cells: Mechanistic Support for the Role of MicroRNA-21

Colorectal cancer is driven by genetic and epigenetic changes in cells to confer phenotypes that promote metastatic transformation and development. Tumour necrosis factor-alpha (TNF-α), a pro-inflammatory mediator, regulates cellular communication within the tumour microenvironment and is associated with the progression of the metastatic phenotype. Oncogenic miR-21 has been shown to be overexpressed in most solid tumours, including colorectal cancer, and is known to target proteins involved in metastatic transformation. In this study, we investigated the relationship between TNF-α and miR-21 regulation in colorectal cancer epithelial cells (SW480 and HCT116). We observed that TNF-α, at concentrations reported to be present in serum and tumour tissue from colorectal cancer patients, upregulated miR-21 expression in both cell lines. TNF-α treatment also promoted cell migration, downregulation of the expression of E-cadherin, a marker of epithelial to mesenchymal transition, and anti-apoptotic BCL-2 (a validated target for miR-21). Knockdown of miR-21 had the opposite effect on each of these TNF-a induced phenotypic changes. Additionally, in the SW480 cell line, although TNF-α treatment selectively induced expression of a marker of metastatic progression VEGF-A, it failed to affect MMP2 expression or invasion activity. Our data indicate that exposing colorectal cancer epithelial cells to TNF-α, at concentrations occurring in the serum and tumour microenvironment of colorectal cancer patients, upregulated miR-21 expression and promoted the metastatic phenotype.

The association between meat and fish intake by preparation methods and breast cancer in the Carolina Breast Cancer Study (CBCS)

PURPOSE

We examined the associations between intake of meat and fish by preparation methods and breast cancer in the Carolina Breast Cancer Study, a racially diverse population-based case-control study.

METHODS

African American (AA) and European American (EA) women aged 20-74 years with a first diagnosis of invasive or in situ breast cancers were frequency matched by race and age group to controls identified through the North Carolina Division of Motor Vehicles and Medicare lists [AA: 548 cases, 452 controls; EA: 858 cases, 748 controls]. Participants self-reported meat preparation methods and intake frequencies. Adjusted odds ratios (OR) and 95% confidence intervals (CIs) were calculated using multivariable logistic regression adjusted for age, race, alcohol intake, body mass index, family income, lactation, marital status, use of oral contraceptives, postmenopausal hormone use, smoking status, and offsets.

RESULTS

Positive associations with breast cancer were observed for intakes of grilled/barbecued hamburger (≥ once/week, OR: 1.28; 95% CI 1.01, 1.63), and pan-fried/oven-broiled beef steak (≥ once/week, OR: 1.36; 95% CI 1.08, 1.72). Inverse associations were observed for pan-fried fish (≥ once/week, OR: 0.77; 95% CI 0.60, 0.98), and for grilled/ barbecued pork chops (> 0 time/week OR: 0.81, 95% CI 0.68, 0.97). Associations tended to be stronger among EA women than among AA women.

CONCLUSION

More frequent consumption of beef prepared with high temperature methods was associated with higher odds of breast cancer while more frequent consumption of pan-fried fish or grilled/barbecued pork chops was associated with lower odds of breast cancer.

Oncogenic Potential of Bisphenol A and Common Environmental Contaminants in Human Mammary Epithelial Cells

There is an ample epidemiological evidence to support the role of environmental contaminants such as bisphenol A (BPA) in breast cancer development but the molecular mechanisms of their action are still not fully understood. Therefore, we sought to analyze the effects of three common contaminants (BPA; 4-tert-octylphenol, OP; hexabromocyclododecane, HBCD) on mammary epithelial cell (HME1) and MCF7 breast cancer cell line. We also supplied some data on methoxychlor, MXC; 4-nonylphenol, NP; and 2-amino-1-methyl-6-phenylimidazo [4–b] pyridine, PhIP. We focused on testing the prolonged (two months) exposure to low nano-molar concentrations (0.0015–0.0048 nM) presumed to be oncogenic and found that they induced DNA damage (evidenced by upregulation of pH2A.X, pCHK1, pCHK2, p-P53) and disrupted the cell cycle. Some agents induced epigenetic (methylation) changes of tumor suppressor genes TIMP3, CHFR, ESR1, IGSF4, CDH13, and GSTP1. Obviously, the accumulation of these molecular alterations is an essential base for cancer development. Consistent with this, we observed that these agents increased cellular invasiveness through collagen. Cellular abilities to form colonies in soft agar were increased for MCF7. Toxic agents induced phosphorylation of protein kinase such as EGFR, CREB, STAT6, c-Jun, STAT3, HSP6, HSP27, AMPKα1, FAK, p53, GSK-3α/β, and P70S6 in HME1. Most of these proteins are involved in potential oncogenic pathways. Overall, these data clarify the molecular alterations that can be induced by some common environmental contaminants in mammary epithelial cells which could be a foundation to understand environmental carcinogenesis.

Dietary phytochemicals as the potential protectors against carcinogenesis and their role in cancer chemoprevention

Health-threatening consequences of carcinogen exposure are mediated via occurrence of electrophiles or reactive oxygen species. As a result, the accumulation of biomolecular damage leads to the cancer initiation, promotion or progression. Accordingly, there is an association between lifestyle factors including inappropriate diet or carcinogen formation during food processing, mainstream, second or third-hand tobacco smoke and other environmental or occupational carcinogens and malignant transformation. Nevertheless, increasing evidence supports the protective effects of naturally occurring phytochemicals against carcinogen exposure as well as carcinogenesis in general. Isolated phytochemicals or their mixtures present in the whole plant food demonstrate efficacy against malignancy induced by carcinogens widely spread in our environment. Phytochemicals also minimize the generation of carcinogenic substances during the processing of meat and meat products. Based on numerous data, selected phytochemicals or plant foods should be highly recommended to become a stable and regular part of the diet as the protectors against carcinogenesis.

HNRNPA2/B1 is upregulated in endocrine-resistant LCC9 breast cancer cells and alters the miRNA transcriptome when overexpressed in MCF-7 cells

MicroRNAs are dysregulated in breast cancer. Heterogeneous Nuclear Ribonucleoprotein A2/B1 (HNRNPA2/B1) is a reader of the N(6)-methyladenosine (m6A) mark in primary-miRNAs (pri-miRNAs) and promotes DROSHA processing to precursor-miRNAs (pre-miRNAs). We examined the expression of writers, readers, and erasers of m6A and report that HNRNPA2/B1 expression is higher in tamoxifen-resistant LCC9 breast cancer cells as compared to parental, tamoxifen-sensitive MCF-7 cells. To examine how increased expression of HNRNPA2/B1 affects miRNA expression, HNRNPA2/B1 was transiently overexpressed (~5.4-fold) in MCF-7 cells for whole genome miRNA profiling (miRNA-seq). 148 and 88 miRNAs were up- and down-regulated, respectively, 48 h after transfection and 177 and 172 up- and down-regulated, respectively, 72 h after transfection. MetaCore Enrichment analysis identified progesterone receptor action and transforming growth factor β (TGFβ) signaling via miRNA in breast cancer as pathways downstream of the upregulated miRNAs and TGFβ signaling via SMADs and Notch signaling as pathways of the downregulated miRNAs. GO biological processes for mRNA targets of HNRNPA2/B1-regulated miRNAs included response to estradiol and cell-substrate adhesion. qPCR confirmed HNRNPA2B1 downregulation of miR-29a-3p, miR-29b-3p, and miR-222 and upregulation of miR-1266-5p, miR-1268a, miR-671-3p. Transient overexpression of HNRNPA2/B1 reduced MCF-7 sensitivity to 4-hydroxytamoxifen and fulvestrant, suggesting a role for HNRNPA2/B1 in endocrine-resistance.

Circulating Levels of miR-574-5p Are Associated with Neurological Outcome after Cardiac Arrest in Women: A Target Temperature Management (TTM) Trial Substudy

Purpose

Postresuscitation neuroprognostication is guided by neurophysiological tests, biomarker measurement, and clinical examination. Recent investigations suggest that circulating microRNAs (miRNA) may help in outcome prediction after cardiac arrest. We assessed the ability of miR-574-5p to predict neurological outcome after cardiac arrest, in a sex-specific manner.

Methods

In this substudy of the Target Temperature Management (TTM) Trial, we enrolled 590 cardiac arrest patients for which blood samples were available. Expression levels of miR-574-5p were measured by quantitative PCR in plasma samples collected 48 h after cardiac arrest. The endpoint of the study was poor neurological outcome at 6 months (cerebral performance category scores 3 to 5).

Results

Eighty-one percent of patients were men, and 49% had a poor neurological outcome. Circulating levels of miR-574-5p at 48 h were higher in patients with a poor neurological outcome at 6 months (p < 0.001), both in women and in men. Circulating levels of miR-574-5p were univariate predictors of neurological outcome (odds ratio (OR) [95% confidence interval (CI)]: 1.5 [1.26-1.78]). After adjustment with clinical variables and NSE, circulating levels of miR-574-5p predicted neurological outcome in women (OR [95% CI]: 1.9 [1.09-3.45]), but not in men (OR [95% CI]: 1.0 [0.74-1.28]).

Conclusion

miR-574-5p is associated with neurological outcome after cardiac arrest in women.

Mechanistic evidence that benzo[a]pyrene promotes an inflammatory microenvironment that drives the metastatic potential of human mammary cells

Benzo[a]pyrene (B(a)P) is a major cancer-causing contaminant present in food such as cooked meats and cereals, and is ubiquitous in the environment in smoke derived from the combustion of organic material. Exposure to B(a)P is epidemiologically linked with the incidence of breast cancer. Although B(a)P is recognized as a complete genotoxic carcinogen, thought to act primarily via CYP-mediated metabolic activation to DNA-damaging species, there is also evidence that B(a)P exposure elicits other biological responses that promote development of the cancer phenotype. Here in mechanistic studies using human mammary cells MCF-7 and MDA-MB-231, we have explored mechanisms whereby B(a)P (10^- 8 to 10^- 5M) promotes inflammation pathways via TNF-α and NFκB leading to IL-6 upregulation, microRNA (Let7a, miR21 and miR29b) dysregulation and activation of VEGF. The miRNA dysregulation is associated with altered expression of inflammation mediators and increased migration and invasive potential of human mammary cancer cells. Our data suggest that mammary cell exposure to B(a)P results in perturbation of inflammation mediators and dysregulation of tumorigenic miRNAs, leading to an inflammation microenvironment that facilitates migration and invasion of mammary epithelial cells. These properties of B(a)P, together with its well-established metabolic activation to DNA-damaging species, offer mechanistic insights into its carcinogenic mode of action.

Ethanol potentiates the genotoxicity of the food-derived mammary carcinogen PhIP in human estrogen receptor-positive mammary cells: mechanistic support for lifestyle factors (cooked red meat and ethanol) associated with mammary cancer

Consumption of cooked/processed meat and ethanol are lifestyle risk factors in the aetiology of breast cancer. Cooking meat generates heterocyclic amines such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Epidemiology, mechanistic and animal studies indicate that PhIP is a mammary carcinogen that could be causally linked to breast cancer incidence; PhIP is DNA damaging, mutagenic and oestrogenic. PhIP toxicity involves cytochrome P450 (CYP1 family)-mediated metabolic activation to DNA-damaging species, and transcriptional responses through Aryl hydrocarbon receptor (AhR) and estrogen-receptor-α (ER-α). Ethanol consumption is a modifiable lifestyle factor strongly associated with breast cancer risk. Ethanol toxicity involves alcohol dehydrogenase metabolism to reactive acetaldehyde, and is also a substrate for CYP2E1, which when uncoupled generates reactive oxygen species (ROS) and DNA damage. Here, using human mammary cells that differ in estrogen-receptor status, we explore genotoxicity of PhIP and ethanol and mechanisms behind this toxicity. Treatment with PhIP (10^-7-10^-4 M) significantly induced genotoxicity (micronuclei formation) preferentially in ER-α positive human mammary cell lines (MCF-7, ER-α+) compared to MDA-MB-231 (ER-α-) cells. PhIP-induced CYP1A2 in both cell lines but CYP1B1 was selectively induced in ER-α(+) cells. ER-α inhibition in MCF-7 cells attenuated PhIP-mediated micronuclei formation and CYP1B1 induction. PhIP-induced CYP2E1 and ROS via ER-α-STAT-3 pathway, but only in ER-α (+) MCF-7 cells. Importantly, simultaneous treatments of physiological concentrations ethanol (10^-3-10^-1 M) with PhIP (10^-7-10^-4 M) increased oxidative stress and genotoxicity in MCF-7 cells, compared to the individual chemicals. Collectively, these data offer a mechanistic basis for the increased risk of breast cancer associated with dietary cooked meat and ethanol lifestyle choices.

A miRNA signature for an environmental heterocyclic amine defined by a multi-organ carcinogenicity bioassay in the rat

Heterocyclic amines (HCAs) produced during high-temperature cooking have been studied extensively in terms of their genotoxic/genetic effects, but recent work has implicated epigenetic mechanisms involving non-coding RNAs. Colon tumors induced in the rat by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) have altered microRNA (miRNA) signatures linked to dysregulated pluripotency factors, such as c-Myc and Krüppel-like factor 4 (KLF4). We tested the hypothesis that dysregulated miRNAs from PhIP-induced colon tumors would provide a "PhIP signature" for use in other target organs obtained from a 1-year carcinogenicity bioassay in the rat. Downstream targets that were corroborated in the rat were then investigated in human cancer datasets. The results confirmed that multiple let-7 family members were downregulated in PhIP-induced skin, colon, lung, small intestine, and Zymbal's gland tumors, and were associated with c-myc and Hmga2 upregulation. PhIP signature miRNAs with the profile mir-21high/mir-126low/mir-29clow/mir-215low/mir-145low were linked to reduced Klf4 levels in rat tumors, and in human pan-cancer and colorectal cancer. It remains to be determined whether this PhIP signature has predictive value, given that more than 20 different genotoxic HCAs are present in the human diet, plus other agents that likely induce or repress many of the same miRNAs. Future studies should define more precisely the miRNA signatures of other HCAs, and their possible value for human risk assessment.

Healthy lifestyle impact on breast cancer-specific and all-cause mortality

PURPOSE

While several studies have evaluated the association of combined lifestyle factors on breast cancer-specific mortality, few have included Hispanic women. We constructed a "healthy behavior index" (HBI) and evaluated its associations with mortality in non-Hispanic White (NHW) and Hispanic women diagnosed with breast cancer from the southwestern U.S.

METHODS

Diet and lifestyle questionnaires were analyzed for 837 women diagnosed with invasive breast cancer (1999-2004) in New Mexico as part of the 4-Corners Women's Health Study. An HBI score ranging from 0 to 12 was based on dietary pattern, physical activity, smoking, alcohol consumption, and body size and shape, with increasing scores representing less healthy characteristics. Hazard ratios for mortality over 14 years of follow-up were estimated for HBI quartiles using Cox proportional hazards models adjusting for education and stratified by ethnicity and stage at diagnosis.

RESULTS

A significant increasing trend was observed across HBI quartiles among all women, NHW women, and those diagnosed with localized or regional/distant stage of disease for all-cause (AC) mortality (p-trend = 0.006, 0.002, 0.03, respectively). AC mortality was increased >2-fold for all women and NHW women in HBI Q4 versus Q1 (HR = 2.18, 2.65, respectively). The association was stronger in women with regional/distant than localized stage of disease (HR = 2.62, 1.94, respectively). Associations for Hispanics or breast cancer-specific mortality were not significant.

CONCLUSIONS

These findings indicate the associations between the HBI and AC mortality, which appear to differ by ethnicity and stage at diagnosis. Interventions for breast cancer survivors should address the combination of lifestyle factors on prognosis.

2-amino-1-methyl-6-phenylimidazo(4,5-b) pyridine (PhIP) induces gene expression changes in JAK/STAT and MAPK pathways related to inflammation, diabetes and cancer

Background

2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), a heterocyclic aromatic amine (HCA) formed in meat that is cooked at high temperatures and then ingested, can potentially be retained in human adipose tissues.

Methods

To determine if PhIP is bioactive in the adipocyte, we exposed a human adipocyte cell line,HepG2 and Caco-2 cells to low dose PhIP. Uptake and retention of PhIP was determined and cytotoxicity was assessed by the TUNEL assay. Relative expression of PhIP-activating genes (CYP1A1, CYP1A2, SULT1A1 and UGT1A1) was determined by RT-PCR and global expression changes were also examined.

Results

The percent retention of 0.1 μCi [¹⁴C]-PhIP over a 24 h period was significantly higher in the adipocyte than the HepG2 (p = 0.0001) and Caco-2 (p = 0.0007) cell lines. Cytotoxicity rates were 14.4 and 2.6 % higher compared to controls in Caco-2 and HepG2 cells (p < 0.001 and 0.054, respectively); no significant differences were detected in adipocyte cells (p = 0.18). Caco-2 and HepG2 cells, respectively, had significantly higher basal expression of CYP1A1 (p = 0.001, p = 0.003), SULT1A1 (p = 0.04, p < 0.001) and UGT1A1 (p < 0.001, p = 0.01) compared to the adipocyte. Exposure to 5nM PhIP did not significantly induce expression of these genes in any of the cell lines. Global gene expression analysis of mature adipocytes exposed to 5nM PhIP for 72 h resulted in statistically significant changes in 8 genes (ANGPTL2, CD14, CIDEA, EGR1, FOS, IGFBP5, PALM and PSAT1). Gene-gene interaction and pathway analysis indicates that PhIP modulates genes controlled by the STAT3 transcriptional factor and initiates leptin signaling via the JAK/STAT and MAPK pathway cascades. Early growth response 1 (EGR1) and prostaglandin synthase 2 (COX-2) were down-regulated via c-Fos, while insulin binding protein 5 (IBP5) was up regulated. Expression of transcription factors (ANGPTL2, HP, LEP, SAA1, SAA2), genes related to inflammation (SAA1, LEP), diabetes (IGFBP5) and cancer risk (SAA2) were also elevated upon exposure to 5 nM PhIP..

Conclusions

PhIP mediates gene expression changes within the adipocyte, and the pathways most affected are related to cancer and other chronic diseases. Further studies are needed on the relationship between dietary carcinogens such as PhIP with cancer, obesity and diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0111-0) contains supplementary material, which is available to authorized users.

miRNAs regulated by estrogens, tamoxifen, and endocrine disruptors and their downstream gene targets

MicroRNAs (miRNAs) are short (22 nucleotides), single-stranded, non-coding RNAs that form complimentary base-pairs with the 3' untranslated region of target mRNAs within the RNA-induced silencing complex (RISC) and block translation and/or stimulate mRNA transcript degradation. The non-coding miRBase (release 21, June 2014) reports that human genome contains ∼ 2588 mature miRNAs which regulate ∼ 60% of human protein-coding mRNAs. Dysregulation of miRNA expression has been implicated in estrogen-related diseases including breast cancer and endometrial cancer. The mechanism for estrogen regulation of miRNA expression and the role of estrogen-regulated miRNAs in normal homeostasis, reproduction, lactation, and in cancer is an area of great research and clinical interest. Estrogens regulate miRNA transcription through estrogen receptors α and β in a tissue-specific and cell-dependent manner. This review focuses primarily on the regulation of miRNA expression by ligand-activated ERs and their bona fide gene targets and includes miRNA regulation by tamoxifen and endocrine disrupting chemicals (EDCs) in breast cancer and cell lines.

Health effects of carbon-containing particulate matter: focus on sources and recent research program results

Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue.

Mammalian models of chemically induced primary malignancies exploitable for imaging-based preclinical theragnostic research

Compared with transplanted tumor models or genetically engineered cancer models, chemically induced primary malignancies in experimental animals can mimic the clinical cancer progress from the early stage on. Cancer caused by chemical carcinogens generally develops through three phases namely initiation, promotion and progression. Based on different mechanisms, chemical carcinogens can be divided into genotoxic and non-genotoxic ones, or complete and incomplete ones, usually with an organ-specific property. Chemical carcinogens can be classified upon their origins such as environmental pollutants, cooked meat derived carcinogens, N-nitroso compounds, food additives, antineoplastic agents, naturally occurring substances and synthetic carcinogens, etc. Carcinogen-induced models of primary cancers can be used to evaluate the diagnostic/therapeutic effects of candidate drugs, investigate the biological influential factors, explore preventive measures for carcinogenicity, and better understand molecular mechanisms involved in tumor initiation, promotion and progression. Among commonly adopted cancer models, chemically induced primary malignancies in mammals have several advantages including the easy procedures, fruitful tumor generation and high analogy to clinical human primary cancers. However, in addition to the time-consuming process, the major drawback of chemical carcinogenesis for translational research is the difficulty in noninvasive tumor burden assessment in small animals. Like human cancers, tumors occur unpredictably also among animals in terms of timing, location and the number of lesions. Thanks to the availability of magnetic resonance imaging (MRI) with various advantages such as ionizing-free scanning, superb soft tissue contrast, multi-parametric information, and utility of diverse contrast agents, now a workable solution to this bottleneck problem is to apply MRI for noninvasive detection, diagnosis and therapeutic monitoring on those otherwise uncontrollable animal models with primary cancers. Moreover, it is foreseeable that the combined use of chemically induced primary cancer models and molecular imaging techniques may help to develop new anticancer diagnostics and therapeutics.

Effects of treatment with androgen receptor ligands on microRNA expression of prostate cancer cells

Post-transcriptional regulation by microRNA (miRNA) is an important aspect of androgen receptor (AR) signalling in prostate cancer cells. However, the global profiling of miRNA expression in prostate cancer cells following treatment with AR ligands has not been reported so far. In this study we examined the effect of treatment with two AR agonists (mibolerone (MIB) and dihydrotestosterone (DHT)) and an AR antagonist (bicalutamide (BIC)) on miRNA expression in the human androgen-dependent LNCaP prostate cancer cell line using microarray technology and verification of selected miRNA using quantitative real-time PCR (qRT-PCR). No miRNA was identified as differentially expressed following treatment with the AR antagonist BIC. In contrast, a number of common and compound-specific alterations in miRNA expression were observed following treatment with AR agonists. Unexpectedly it was found that treatment with the AR agonists resulted in the repression of miR-221, a miRNA previously established to be involved with prostate cancer development. This observation indicates that this miRNA may have a more complex role in prostate cancer development than considered previously. Treatment with MIB led to an induction of miR-210 expression, a hypoxia-related miRNA. This miRNA is reported to be involved in cell adaptation to hypoxia and thus induction in conditions of normoxia may be important in driving metabolic changes observed in prostate cancer. Thus examining the effect of AR agonists and antagonists on miRNA expression can provide novel insights into the response of cells to AR ligands and subsequent downstream events.

Noncoding RNA response to xenobiotic exposure: an indicator of toxicity and carcinogenicity

INTRODUCTION

Human exposure to certain environmental and occupational chemicals is one of the major risk factors for noncommunicable diseases, including cancer. Therefore, it is desirable to take advantage of subtle exposure-related adverse cellular events for early disease detection and to identify potential dangers caused by new and currently under-evaluated drugs and chemicals. Nongenotoxic events due to carcinogen/toxicant exposure are a general hallmark of sustained cellular stress leading to tumorigenesis. These processes are globally regulated via noncoding RNAs (ncRNAs). Tumorigenesis-associated genotoxic and nongenotoxic events lead to the altered expression of ncRNAs and may provide a mechanistic link between chemical exposure and tumorigenesis. Current advances in toxicogenomics are beginning to provide valuable insight into gene-chemical interactions at the transcriptome level.

AREAS COVERED

In this review, we summarize recent information about the impact of xenobiotics on ncRNAs. Evidence highlighted in this review suggests a critical role of ncRNAs in response to carcinogen/toxicant exposure.

EXPERT OPINION

Benefits for the use of ncRNAs in carcinogenicity assessment include remarkable tissue specificity, early appearance, low baseline variability, and their presence and stability in biological fluids, which suggests that the incorporation of ncRNAs in the evaluation of cancer risk assessment may enhance substantially the efficiency of toxicity and carcinogenicity testing.