Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten, remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. This work demonstrates tungsten’s ability to induce carcinogenic-related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer related pathways in transformed clones as determined by RNA sequencing. Human bronchial epithelial cell line (BEAS-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten.
In order to examine the epigenetic mechanisms that mediate tungsten’s tumorigenicity, we investigated if tungsten alters the levels of global histone methylation and if these changes are due to tungsten influencing the histone demethylases. We found that cells acutely treated with tungsten displayed significantly increased numbers of H34me3 and H3K9me2 histone marks on a global scale. This increase was due to down-regulation in the protein levels of the histone demethylases JMJD1A and JARID1A. The increase in global histone methylation remained when cellular SAM levels were depleted. The decrease in histone demethylase proteins was found to be due to a reduction in their gene expression. Epigenetic alterations induced by tungsten in the histone demethylase genes caused the repression.
We also evaluated insoluble tungsten, tungsten oxide (WO3). WO3 is an occupational exposure hazard. The primary route of WO 3 exposure is inhalation and WO3 is known as a pulmonary irritant. WO3 exposure led to stochastic results, which were likely due to the random effects of the particles.
Given the carcinogenic potential of other metals, it is likely that tungsten will exert carcinogenic outcomes. This study evaluates cancer-associated endpoints induced by tungsten exposure in both in vitro and in vivo models. To evaluate the mechanisms that underlie tungsten-induced carcinogenesis, alterations to the epigenome are assessed. Arsenic, cadmium, nickel, and chromium (VI) are poor mutagens; however, they exert their carcinogenic potential via epigenetic mechanisms. The literature is currently void of investigations examining the epigenetic effects of tungsten. Given the evidence characterizing metals as epimutagens, it is likely that tungsten toxicity and carcinogenesis is mediated via epigenetic mechanisms.
|Advisor:||Costa, Max, Klein, Catherine|
|Commitee:||Cuddapah, Suresh, Sun, Hong, Zoroddu, Maria|
|School:||New York University|
|Department:||Environmental Health Medicine|
|School Location:||United States -- New York|
|Source:||DAI-B 78/01(E), Dissertation Abstracts International|
|Subjects:||Genetics, Pharmacology, Environmental science, Oncology|
|Keywords:||Epigenetic modifications, Mechanistic basis, Tungsten|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be