Chemoprevention of Cigarette Smoke-Induced Alterations of MicroRNA Expression in Rat Lungs
ABSTRACT We previously showed that exposure to environmental cigarette smoke (ECS) for 28 days causes extensive downregulation of microRNA expression in the lungs of rats, resulting in the overexpression of multiple genes and proteins. In the present study, we evaluated by microarray the expression of 484 microRNAs in the lungs of either ECS-free or ECS-exposed rats treated with the orally administered chemopreventive agents N-acetylcysteine, oltipraz, indole-3-carbinol, 5,6-benzoflavone, and phenethyl isothiocyanate (as single agents or in combinations). This is the first study of microRNA modulation by chemopreventive agents in nonmalignant tissues. Scatterplot, hierarchical cluster, and principal component analyses of microarray and quantitative PCR data showed that none of the above chemopreventive regimens appreciably affected the baseline microRNA expression, indicating potential safety. On the other hand, all of them attenuated ECS-induced alterations but to a variable extent and with different patterns, indicating potential preventive efficacy. The main ECS-altered functions that were modulated by chemopreventive agents included cell proliferation, apoptosis, differentiation, Ras activation, P53 functions, NF-kappaB pathway, transforming growth factor-related stress response, and angiogenesis. Some microRNAs known to be polymorphic in humans were downregulated by ECS and were protected by chemopreventive agents. This study provides proof-of-concept and validation of technology that we are further refining to screen and prioritize potential agents for continued development and to help elucidate their biological effects and mechanisms. Therefore, microRNA analysis may provide a new tool for predicting at early carcinogenesis stages both the potential safety and efficacy of cancer chemopreventive agents.
- SourceAvailable from: Farrukh Aqil[Show abstract] [Hide abstract]
ABSTRACT: Dysregulated miRNA expression has been associated with the development and progression of cancers, including breast cancer. The role of estrogen (E2) in regulation of cell proliferation and breast carcinogenesis is well-known. Recent reports have associated several miRNAs with estrogen receptors in breast cancers. Investigation of the regulatory role of miRNAs is critical for understanding the effect of E2 in human breast cancer, as well as for developing strategies for cancer chemoprevention. In the present study we used the well-established ACI rat model that develops mammary tumors upon E2 exposure and identified a 'signature' of 33 significantly modulated miRNAs during the process of mammary tumorigenesis. Several of these miRNAs were altered as early as 3 weeks after initial E2 treatment and their modulation persisted throughout the mammary carcinogenesis process, suggesting that these molecular changes are early events. Furthermore, ellagic acid, which inhibited E2-induced mammary tumorigenesis in our previous study, reversed the dysregulation of miR-375, miR-206, miR-182, miR-122, miR-127 and miR-183 detected with E2 treatment and modulated their target proteins (ERα, cyclin D1, RASD1, FoxO3a, FoxO1, cyclin G1, Bcl-w and Bcl-2). This is the first systematic study examining the changes in miRNA expression associated with E2 treatment in ACI rats as early as 3 week until tumor time point. The effect of a chemopreventive agent, ellagic acid in reversing miRNAs modulated during E2-mediated mammary tumorigenesis was also established. These observations provide mechanistic insights into the new molecular events behind the chemoprevention action of ellagic acid in and treatment of breast cancer.Cancer letters 06/2013; DOI:10.1016/j.canlet.2013.06.012 · 5.02 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Dietary phytochemicals offer protection from oxidative damages and lower the risks of chronic diseases, by complementary and overlapping action mechanisms. These include antioxidant activity, regulation of gene expression and cell cycle, stimulation of the immune and hormonal systems and modulation of cell–cell communication. Gap-junction intercellular communication (GJIC) plays an important role in maintaining tissue homeostasis by allowing the intercellular exchange of ions and regulatory molecules associated with cell proliferation, differentiation and apoptosis, and by contributing to intracellular signaling. This mechanism is strictly regulated and abnormal GJIC can result in several pathological conditions. GJIC is deregulated in cancer cells and reversible GJIC inhibition is strongly related to the promotion phase of carcinogenesis, likely mediated by reactive oxygen species. Whereas, the reversible inhibition of GJIC is related to the promotion phase of carcinogenicity, enhancers of GJIC are expected to prevent cancer. Several dietary plant compounds demonstrated the ability to control GJIC at the epigenetic levels and to prevent GJIC down-regulation by tumor promoting compounds, thus preventing cancers. In this Commentary, a number of reported studies on several phytochemicals in dietary and medicinal plants, which were able to affect GJIC and their structural proteins, i.e., connexins, in different in vivo and in vitro systems, were examined. The growing evidence, on the involvement of plant-derived molecules in the modulation of GJIC and in understanding of the specific action mechanisms, might offer a new perspective of the protective and/or preventive effects of dietary phytochemicals, in addition to possible chemotherapeutic use.Phytochemistry Reviews 05/2012; 11(2-3). DOI:10.1007/s11101-012-9235-7 · 2.89 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The tumor suppressive microRNA miR-34a is transcriptionally regulated by p53 and shown to inhibit breast cancer cell proliferation as well as being a marker of increased disease free survival. Indole-3-carbinol (I3C) derived from cruciferous vegetables, artemisinin, extracted from the sweet wormwood plant, and artesunate, a semi-synthetic derivative of artemisinin, are phytochemicals with anti-tumorigenic properties however, little is known about the role of microRNAs in their mechanism of action. Human breast cancer cells expressing wild-type (MCF-7) or mutant p53 (T47D) were treated with a concentration range and time course of each phytochemical under conditions of cell cycle arrest as detected by flow cytometry to examine the potential connection between miR-34a expression and their anti-proliferative responses. Real-time PCR and western blot analysis of extracted RNA and total protein revealed artemsinin and artesunate increased miR-34a expression in a dose-dependent manner correlating with down-regulation of the miR-34a target gene, CDK4. I3C stimulation of miR-34a expression required functional p53, whereas, both artemisinin and artesunate up-regulated miR-34a expression regardless of p53 mutational status or in the presence of dominant negative p53. Phytochemical treatments inhibited the luciferase activity of a construct containing the wild-type 3'UTR of CDK4, but not those with a mutated miR-34a binding site, whereas, transfection of miR-34a inhibitors ablated the phytochemical mediated down-regulation of CDK4 and induction of cell cycle arrest. Our results suggest that miR-34a is an essential component of the anti-proliferative activities of I3C, artemisinin, and artesunate and demonstrate that both wild-type p53 dependent and independent pathways are responsible for miR-34a induction. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.Molecular Carcinogenesis 03/2015; DOI:10.1002/mc.22296 · 4.77 Impact Factor