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Original Article

Oxidative stress and breast cancer biomarkers: the case of the
cytochrome P450 2E1

Subir Singh , Ramkumar Rajendran , Kengo Kuroda , Emiko Isogai , Marija Krstic-Demonacos ,
3
4
2
3
1
Constantinos Demonacos 1
1 Manchester Pharmacy School, University of Manchester, Manchester M13 9PT, UK.
2 School of Pharmacy, International Medical University, Bukit Jalil, 57000 Kuala Lumpur, Malaysia.
3 Laboratory of Animal Microbiology, Tohoku University Graduate School of Agricultural Science, Sendai, Miyagi, 981-8555, Japan.
4 School of Environment and Life Sciences, University of Salford, Peel Building, Salford, M5 4WT, UK.
Correspondence to: Dr. Constantinos Demonacos, Manchester Pharmacy School, University of Manchester, Stopford building, Oxford Road,
Manchester M13 9PT, UK. E-mail: cdemonacos@manchester.ac.uk

Dr. Demonacos joined the University of Manchester, Manchester Pharmacy School in 2003 where he is involved in the
investigation of the role of ROS in cellular energy metabolism and breast carcinogenesis. In addition, Dr. Demonacos’
laboratory explores the signaling events that facilitate cancer cells to evade immunosurveillance.

A B S T R AC T
Aim: The aim of the study is to investigate the impact of the cytochrome P450 2E1, which is the most efficient CYP450 family
member in generating reactive oxygen species (ROS), on cellular energy metabolism of breast cancer cells and therefore the
effects of CYP2E1 on breast carcinogenesis. Methods: The estrogen receptor positive MCF-7 and the triple negative MDA-
MB-231 breast cancer cells were used as experimental system to estimate ROS generation in these cells overexpressing CYP2E1
and treated with the glycolytic inhibitors 3-bromopyruvate or 2-deoxyglucose in the presence or absence of the CYP2E1 inhibitor
chlormethiazole. Adenosine triphosphate (ATP) assay was used to measure ATP production and lactate assay to quantify the efflux
of lactic acid in breast cancer cells treated with the CYP2E1 inhibitor chlormethiazole, the mitochondrial membrane potential
and cell viability assays were employed to assess the pathway of cellular energy production and cellular death respectively after
treatment of MCF-7 and MDA-MB-231 with the CYP2E1 activator acetaminophen or the CYP2E1 inhibitor chlormethiazole.
Results: The results indicated increased ROS generation in breast cancer cells overexpressing CYP2E1. ROS generation was
differentially regulated in breast cancer cells upon treatment with the CYP2E1 inhibitor chlormethiazole. Chlormethiazole
treated MCF-7 cells exhibited reduced lactate efflux implying that CYP2E1 directly or indirectly regulates the glycolytic rate
in these cells. Furthermore the mitochondrial membrane potential of both MCF-7 and MDA-MB-231 cells was differentially
affected by the CYP2E1 activator acetaminophen versus the CYP2E1 inhibitor chlormethiazole providing additional support for
the involvement of CYP2E1 in energy metabolic pathways in breast cancer. Conclusion: Results presented in this study provide
evidence to suggest that CYP2E1 regulates cellular energy metabolism of breast cancer cells in a manner dependent on cell type
and potentially on the clinical staging of the disease therefore CYP2E1 is a possible breast cancer biomarker.

Key words: Reactive oxygen species; cytochrome P450 2E1; glycolysis; breast cancer

INTRODUCTION detrimental for the cells as it can lead to DNA damage and
oxidation of proteins and lipids changing their functions.
[2]
Reactive oxygen species (ROS) such as superoxide, hydroxyl Accumulating evidence indicates that apart from their
radical, and hydrogen peroxide are metabolic by-products
leaking from the complexes I and III of the mitochondrial This is an open access article distributed under the terms of the Creative
respiratory chain. Generation of high ROS levels is Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows
[1]
others to remix, tweak, and build upon the work non-commercially, as long as
the author is credited and the new creations are licensed under the identical
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How to cite this article: Singh S, Rajendran R, Kuroda K, Isogai E,
Krstic-Demonacos M, Demonacos C. Oxidative stress and breast
cancer biomarkers: the case of the cytochrome P450 2E1. J Cancer
DOI: Metasta Treat 2016;2:268-76.
10.20517/2394-4722.2016.42
Received: 24-06-2016; Accepted: 23-07-2016.
268
©2016 Journal of Cancer Metastasis and Treatment ¦ Published by OAE Publishing Inc.