The androgen receptor independent mechanism of toxicity of the novel anti-tumor agent 11[beta]-dichloro
Author(s)Fedeleş, Bogdan I
AR independent mechanism of toxicity of the novel anti-tumor agent 11[beta]-dichloro
multifaceted toxicological puzzle : investigating the androgen receptor independent cellular responses to the novel anti-tumor agent 11[beta]-dichloro
Massachusetts Institute of Technology. Dept. of Biological Engineering.
John M. Essigmann.
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Inspired by the toxicity mechanism of cisplatin in testicular cancer, a series of bi-functional genotoxicants has been designed that supplement their DNA damaging properties with the ability to interact with tumor specific proteins. One such compound, 11[beta] -dichloro links an aniline mustard moiety to a steroid ligand for the androgen receptor (AR). In vitro and in vivo (cell cultures, mouse xenografts) studies highlighted the potent antitumor properties of the molecule, which can prevent growth of AR positive tumor xenografts in mice. However, 11 p-dichloro also proved highly effective against many cancer lines that do not express the AR, more so than other nitrogen mustards commonly used in chemotherapy. To understand better the AR independent mechanism, the toxicity of 116 -dichloro was investigated in Saccharomyces cerevisiae, by interrogating the complete yeast single-gene deletion mutant library. Surprisingly, the screen revealed that the mutants most sensitive to 11[beta] -dichloro are not the ones lacking genes involved in DNA repair, but rather mutants lacking genes involved in mitochondrial and ribosomal function. While some of the sensitive mutants are also sensitive to other DNA damaging agents, almost half of them are uniquely sensitive to 11[beta] -dichloro, suggesting a DNA-damage independent mechanism of action. Based on the yeast findings, we tested mechanistic hypotheses in HeLa cells (an AR negative human cancer cell line), and discovered that 11[beta] -dichloro induces a large amount of reactive oxygen species (ROS), accompanied by a significant depletion of the antioxidant pool and a perturbation of the mitochondrial inner membrane potential. We also discovered that cotreatment with antioxidants such as N-acetyl cysteine or vitamin E alleviates the toxicity of 11[beta]-dichloro, suggesting that ROS play an important role in the mechanism of toxicity. In terms of transcriptional responses, previous observations were confirmed that 11[beta] -dichloro upregulates expression of genes involved in the unfolded protein response (UPR) and sterol biosynthesis. Additional cellular responses consistent with these pathways were the striking increase in cytosolic calcium and significant changes in the size of the cells. Taken together, our results highlight the multifaceted toxicological profile of 11[beta] -dichloro, indicating that besides DNA damage, the generation of ROS and induction of UPR may be the additional pathways responsible for the potent anticancer effects of this agent.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2009.In title on title-page "[beta]" appears as the lower-case Greek letter. Vita. Page 284 blank. Cataloged from PDF version of thesis.Includes bibliographical references.
DepartmentMassachusetts Institute of Technology. Dept. of Biological Engineering.
Massachusetts Institute of Technology