Low mitochondrial DNA copy number induces chemotherapy resistance via epithelial-mesenchymal transition by DNA methylation in esophageal squamous cancer cells

Yuto Kubo; Koji Tanaka; Yasunori Masuike; Tsuyoshi Takahashi; Kotaro Yamashita; Tomoki Makino; Takuro Saito; Kazuyoshi Yamamoto; Tomoyuki Tsujimoto; Takashi Harino; Yukinori Kurokawa; Makoto Yamasaki; Kiyokazu Nakajima; Hidetoshi Eguchi; Yuichiro Doki

doi:10.1186/s12967-022-03594-2

Low mitochondrial DNA copy number induces chemotherapy resistance via epithelial-mesenchymal transition by DNA methylation in esophageal squamous cancer cells

J Transl Med. 2022 Aug 29;20(1):383. doi: 10.1186/s12967-022-03594-2.

Authors

Affiliations

¹ Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, 2-2 E2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
² Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, 2-2 E2 Yamadaoka, Suita, Osaka, 565-0871, Japan. ktanaka@gesurg.med.osaka-u.ac.jp.

Abstract

Background: Esophageal squamous cell carcinoma (ESCC) is one of the most severe cancers and is characterized by chemotherapy resistance and poor prognosis associated with epithelial-mesenchymal transition (EMT). In a previous study, a low mitochondrial DNA (mtDNA) copy number was associated with poorer prognosis and induced EMT in ESCC. However, the detailed mechanism related to mtDNA copy number and EMT is unclear. The aim of this study was to clarify the mechanism by which a change in mtDNA copy number contributes to EMT and to examine treatment of chemotherapy resistance in ESCC.

Methods: The association between low mtDNA copy number and chemotherapy resistance was investigated using specimens from 88 patients who underwent surgery after neoadjuvant chemotherapy. Then, the mtDNA content of human ESCC cell lines, TE8 and TE11, was depleted by knockdown of mitochondrial transcription factor A expression. The present study focused on modulation of mitochondrial membrane potential (MMP) and DNA methylation as the mechanisms by which mtDNA copy number affects EMT. mRNA and protein expression, chemotherapy sensitivity, proliferation, MMP and DNA methylation were evaluated, and in vitro and in vivo assays were conducted to clarify these mechanisms.

Results: ESCC patients with decreased mtDNA copy number who underwent R0 resection after neoadjuvant chemotherapy had significantly worse pathological response and recurrence-free survival. Additionally, low mtDNA copy number was associated with resistance to chemotherapy in vitro and in vivo. mtDNA controlled MMP, and MMP depolarization induced EMT. Depletion of mtDNA and low MMP induced DNA methylation via a DNA methylation transcription factor (DNMT), and a DNMT inhibitor suppressed EMT and improved chemotherapy sensitivity in mtDNA-depleted ESCC cells, as shown by in vitro and in vivo assays.

Conclusion: This study showed that decreased mtDNA copy number induced EMT via modulation of MMP and DNA methylation in ESCC. Therapeutic strategies increasing mtDNA copy number and DNMT inhibitors may be effective in preventing EMT and chemosensitivity resistance.

Keywords: Chemotherapy; DNA methylation; Epithelial-mesenchymal transition; Esophageal cancer; Mitochondrial DNA; Mitochondrial membrane potential.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Carcinoma, Squamous Cell* / drug therapy
Carcinoma, Squamous Cell* / genetics
Carcinoma, Squamous Cell* / metabolism
Cell Line, Tumor
Cell Proliferation / genetics
DNA Copy Number Variations / genetics
DNA Methylation / genetics
DNA, Mitochondrial / genetics
DNA, Mitochondrial / metabolism
Epithelial-Mesenchymal Transition / genetics
Esophageal Neoplasms* / drug therapy
Esophageal Neoplasms* / genetics
Esophageal Neoplasms* / metabolism
Esophageal Squamous Cell Carcinoma* / drug therapy
Esophageal Squamous Cell Carcinoma* / genetics
Gene Expression Regulation, Neoplastic
Humans

Substances

DNA, Mitochondrial