Past Issue

Volume 20, Number 3, Autumn 2018, Serial Number: 79, Pages: 312-317

Identification of An mtDNA Setpoint Associated with Highest Levels of CD44 Positivity and Chemoresistance in HGC-27 and MKN-45 Gastric Cancer Cell Lines


Gökhan Terzioğlu, Ph.D, 1, #, Özlem Türksoy, Ph.D, 1, #, *, Ömer Faruk Bayrak, Ph.D, 2,
Department of Biotechnology, Yeditepe University, Inönü Mahallesi, Kayışdağı Cad. 326A 26 Ağustos Yerleşimi, 34755 Ataşehir-İstanbul, Turkey
Department of Medical Genetics, Faculty of Medicine, Yeditepe University, Inönü Mahallesi, Kayışdağı Cad. 326A 26 Ağustos Yerleşimi, 34755 Ataşehir-İstanbul, Turkey
*Corresponding Address: Department of Biotechnology Yeditepe University Inönü Mahallesi Kayışdağı Cad. 326A 26 Ağustos Yerleşimi 34755 Ataşehir-İstanbul Turkey Email:ozlemturksoy@gmail.com

The first two authors equally contributed to this article.

Abstract

Objective

Cancer stem cells (CSCs) have important roles in survival and chemoresistance. These cells are commonly recognized with CD44 and CD24 markers. In this study, we aimed to analyze the effects of mtDNA content on cell surface positivity for anti-CD24 and anti-CD44 antibodies and chemoresistance level in AGS, HGC-27 and MKN-45 gastric cancer (GC) cell lines and to determine a setpoint for mtDNA copy for each cell line.

Materials and Methods

In this experimental study, we initially decreased mtDNA levels in AGS, HGC-27 and MKN-45 by EtBr treatment. This depletion was confirmed with quantitative polymerase chain reaction (qPCR). Changes in cell surface positivity for anti-CD24 and anti-CD44 antibodies in control and mtDNA-depleted AGS, HGC-27 and MKN-45 were then analyzed with flow cytometry. Changes in chemoresistance (5-FU and cisplatin) were analyzed for all cell lines. The relationship between mtDNA content and cell surface positivity for CD24 and CD44 markers was examined.

Results

The highest CD44 positivity was found in HGC-27 and MKN-45 ρlow cells which had 33-40% mtDNA content of control cells, however, CD24 positivity decreased with mtDNA depletion in all cell lines. The highest chemoresistance levels were found in all ρlow cells. mtDNA-recovered (i.e. reverted) HGC-27 and MKN-45 cells partially maintained their increased chemoresistance while reverted AGS cells did not maintain an increased level of chemoresistance.

Conclusion

mtDNA depletion triggers chemoresistance in cancer cell lines and is correlated with increase and decrease of CD44 and CD24 positivity respectively in HGC-27 and MKN-45 GC cell lines. A mtDNA content above or below the identified setpoint (33-40% of that in control cells), results in the decrease of CD44 positivity and chemoresistance levels.