Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 7, 2021; 27(41): 7134-7143
Published online Nov 7, 2021. doi: 10.3748/wjg.v27.i41.7134
Circulating tumor DNA dynamics analysis in a xenograft mouse model with esophageal squamous cell carcinoma
Hiroyuki Terasawa, Hideaki Kinugasa, Kazuhiro Nouso, Shumpei Yamamoto, Mami Hirai, Takehiro Tanaka, Akinobu Takaki, Hiroyuki Okada
Hiroyuki Terasawa, Hideaki Kinugasa, Kazuhiro Nouso, Shumpei Yamamoto, Mami Hirai, Akinobu Takaki, Hiroyuki Okada, Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 7008558, Japan
Takehiro Tanaka, Department of Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 7008558, Japan
Author contributions: Kinugasa H designed the manuscript; Terasawa H drafted the manuscript; Kinugasa H, Terasawa H, Yamamoto S, Hirai M, Tanaka T and Takaki A were responsible for experiments; Kinugasa H, Nouso K and Okada H supervised the manuscript preparation; all authors approved the final manuscript.
Supported by JSPS KAKENHI (19k17433).
Institutional review board statement: This study was reviewed approved by [the ethics committee of Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital] Institutional Review Board.
Institutional animal care and use committee statement: Xenograft mouse experimental protocols were approved by the Ethical Committee of Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences (OKU-2019276).
Conflict-of-interest statement: The authors declare that there are no conflicts of interest.
Data sharing statement: No additional data are available.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Hideaki Kinugasa, MD, PhD, Doctor, Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-Cho Kita-Ku, Okayama 7008558, Japan. gyacy14@gmail.com
Received: May 14, 2021
Peer-review started: May 14, 2021
First decision: July 14, 2021
Revised: July 21, 2021
Accepted: August 30, 2021
Article in press: August 30, 2021
Published online: November 7, 2021
Processing time: 175 Days and 20.5 Hours
Abstract
BACKGROUND

It remains unclear which factors, such as tumor volume and tumor invasion, influence circulating tumor DNA (ctDNA), and the origin of ctDNA in liquid biopsy is always problematic. To use liquid biopsies clinically, it will be very important to address these questions.

AIM

To assess the origin of ctDNA, clarify the dynamics of ctDNA levels, assess ctDNA levels by using a xenograft mouse after treatment, and to determine whether tumor volume and invasion are related to ctDNA levels.

METHODS

Tumor xenotransplants were established by inoculating BALB/c-nu/nu mice with the TE11 cell line. Groups of mice were injected with xenografts at two or four sites and sacrificed at the appropriate time point after xenotransplantation for ctDNA analysis. Analysis of ctDNA was performed by droplet digital PCR, using the human telomerase reverse transcriptase (hTERT) gene.

RESULTS

Mice given two-site xenografts were sacrificed for ctDNA at week 4 and week 8. No hTERT was detected at week 4, but it was detected at week 8. However, in four-site xenograft mice, hTERT was detected both at week 4 and week 6. These experiments revealed that both tumor invasion and tumor volume were associated with the detection of ctDNA. In resection experiments, hTERT was detected at resection, but had decreased by 6 h, and was no longer detected 1 and 3 d after resection.

CONCLUSION

We clarified the origin and dynamics of ctDNA, showing that tumor volume is an important factor. We also found that when the tumor was completely resected, ctDNA was absent after one or more days.

Keywords: Liquid biopsy; Circulating tumor DNA; Xenograft; Esophageal squamous cell carcinoma; Dynamics of circulating tumor DNA

Core Tip: We clarified the origin and dynamics of circulating tumor DNA (ctDNA), showing that not only tumor invasion but also tumor volume was an important factor. The possibility of detecting ctDNA in early-stage cancers with shallow depth was demonstrated. Also, ctDNA could be measured at 1 d after tumor resection to evaluate the residuals, and the half-life of ctDNA was estimated to be 1.8-3.2 h.