Tropical Journal of Pharmaceutical Research

Original Research Article | OPEN ACCESS

Hypoxia-induced gene expression pattern in doxorubicin-resistant MCF7 cells

Hana N Hammad¹ , Tuqa M Abu Thiab¹, Malek A Zihlif²

¹Department of Biological Sciences, School of Science; ²Department of Pharmacology, School of Medicine, The University of Jordan, Amman 11942, Jordan.

For correspondence:- Hana Hammad Email: hhammad@ju.edu.jo Tel:+962798507863

Accepted: 27 July 2019 Published: 27 August 2019

Citation: Hammad HN, Thiab TM, Zihlif MA. Hypoxia-induced gene expression pattern in doxorubicin-resistant MCF7 cells. Trop J Pharm Res 2019; 18(8):1589-1595 doi: 10.4314/tjpr.v18i8.3

© 2019 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..

Abstract

Purpose: To investigate hypoxia-induced gene expression pattern in doxorubicin-resistant human breast cancer cells (MCF7).

Methods: Human breast cancer cells (MCF7) were exposed to 60 episodes of 8 h hypoxia thrice a week for three months. Chemo-resistance to doxorubicin was assessed using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) cell proliferation assay. Real-time quantitative polymerase chain reaction (qRT-PCR) assay was performed to assess gene expression pattern in doxorubicin-resistant cells on exposure to hypoxia.

Results: Hypoxia significantly increased the resistance of MCF7 cells to doxorubicin, with a maximum of 16.42-fold enhancement after 25 episodes of 8-h hypoxia, while the resistance thereafter significantly decreased with prolonged episodes of hypoxia (p < 0.05). Gene expression analysis revealed significant changes in 42 genes. The expressions of 10 of these genes were significantly upregulated, while those of 32 genes were significantly down-regulated (p < 0.05). Cytochrome P450 family 1, subfamily A, member1 (CYP1A1) was the most conspicuous upregulated gene (13.32-fold), while breast cancer gene 1 (BRCA1) was the most down-regulated (8.23-fold). Gene expression analysis after 60 episodes of 8-h hypoxia revealed the upregulation of CYP1A1 (5.77-fold). Similarly, 27 genes were significantly down-regulated, with BRCA2 as the most down-regulated gene (8.11-fold). Topoisomerase (DNA) II alpha (TOP2A) was the most down-regulated among genes involved in drug metabolism and resistance (6.37-fold), while cyclin-dependent kinase 2 (CDK2) was the most profoundly downregulated among genes involved in cell cycle regulation (3.56-fold).

Conclusion: These results indicate that development of resistance to doxorubicin by MCF7 cells after short-term hypoxia results from the upregulation of genes responsible for the metabolism of doxorubicin and for shifting the cells to alternative pathway driven principally by EGF and ESR2. The observed down-regulation is an adaptation of the MCF7 cells to survive under long-term hypoxia.

Keywords: Breast cancer cells, Doxorubicin, Chemoresistance, Hypoxia, Gene expression