Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 28, 2016; 22(44): 9765-9774
Published online Nov 28, 2016. doi: 10.3748/wjg.v22.i44.9765
Anticancer effect of linalool via cancer-specific hydroxyl radical generation in human colon cancer
Kenichi Iwasaki, Yun-Wen Zheng, Soichiro Murata, Hiromu Ito, Ken Nakayama, Tomohiro Kurokawa, Naoki Sano, Takeshi Nowatari, Myra O Villareal, Yumiko N Nagano, Hiroko Isoda, Hirofumi Matsui, Nobuhiro Ohkohchi
Kenichi Iwasaki, Yun-Wen Zheng, Soichiro Murata, Ken Nakayama, Tomohiro Kurokawa, Naoki Sano, Takeshi Nowatari, Nobuhiro Ohkohchi, Department of Surgery and Organ Transplantation, Faculty of Medicine, University of Tsukuba, Tsukuba-shi, Ibaraki 305-8575, Japan
Yun-Wen Zheng, Regenerative Medicine Research Center, Jiangsu University Hospital, Zhenjiang 212001, Jiangsu Province, China
Yun-Wen Zheng, Department of Regenerative Medicine, Graduate School of Medicine, Yokohama City University, Yokohama-shi, Kanagawa 236-0004, Japan
Hiromu Ito, Yumiko N Nagano, Hirofumi Matsui, Department of Gastroenterology, Faculty of Medicine, University of Tsukuba, Tsukuba-shi, Ibaraki 305-8575, Japan
Myra O Villareal, Hiroko Isoda, Faculty of Life and Environmental Sciences, Alliance of Research on North Africa, University of Tsukuba, Tsukuba-shi, Ibaraki 305-8572, Japan
Author contributions: Iwasaki K, Murata S, Nagano YN, and Matsui H designed the procedure; Iwasaki K, Ito H, and Orlina VM conducted the in vitro experiments; Iwasaki K, Nakayama K, Kurokawa T, Sano N, and Nowatari T conducted the in vivo experiments; Isoda H, Matsui H, Zheng YW, and Ohkohchi N reviewed the data; Iwasaki K wrote the manuscript.
Supported by (in part) Ministry of Education, Culture, Sports, Science, and Technology of Japan, KAKENHI, No. 25462069 and No. 16K15604; The Jiangsu innovative and entrepreneurial project for the introduction of high-level talent; The Jiangsu science and technology planning project, No. BE2015669; Novartis Pharma Research Foundation (to Zheng YW); and Japan Science and Technology Research Partnership for Sustainable Development (SATREPS) project FY2015 (to Isoda H).
Institutional review board statement: Animal experiments were performed in accordance with the university’s Regulations for Animal Experiments and Fundamental Guidelines for Proper Conduct of Animal Experiment and Related Activities in Academic Research Institutions, under the jurisdiction of the Japanese Ministry of Education, Culture, Sports, Science, and Technology.
Institutional animal care and use committee statement: Animal experiments were performed in a humane manner after receiving approval from the Institutional University Experiment Committee of the University of Tsukuba (protocol number: 15-254).
Conflict-of-interest statement: The authors report no relevant conflicts of interest.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (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/
Correspondence to: Yun-Wen Zheng, PhD, Associate Professor, Department of Surgery and Organ Transplantation, Faculty of Medicine, University of Tsukuba, Tsukuba-shi, Ibaraki 305-8575, Japan. ywzheng@md.tsukuba.ac.jp
Telephone: +81-29-8533221 Fax: +81-29-8533222
Received: July 21, 2016
Peer-review started: July 22, 2016
First decision: September 20, 2016
Revised: October 5, 2016
Accepted: October 27, 2016
Article in press: October 27, 2016
Published online: November 28, 2016
Processing time: 128 Days and 9.2 Hours
Abstract
AIM

To investigate the anticancer mechanisms of the monoterpenoid alcohol linalool in human colon cancer cells.

METHODS

The cytotoxic effect of linalool on the human colon cancer cell lines and a human fibroblast cell line was examined using the WST-8 assay. The apoptosis-inducing effect of linalool was measured using the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and flow cytometry with Annexin V. Oxidative stress was investigated by staining for diphenyl-1-pyrenylphosphine, which is a cellular lipid peroxidation marker, and electron spin resonance spectroscopy. Sixteen SCID mice xenografted with human cancer cells were randomized into 3 groups for in vivo analysis: control and low-dose and high-dose linalool groups. The control group was administered tap water orally every 3 d. The linalool treatment groups were administered 100 or 200 μg/kg linalool solution orally for the same period. All mice were sacrificed under anesthesia 21 d after tumor inoculation, and tumors and organs were collected for immunohistochemistry using an anti-4-hydroxynonenal antibody. Tumor weights were measured and compared between groups.

RESULTS

Linalool induced apoptosis of cancer cells in vitro, following the cancer-specific induction of oxidative stress, which was measured based on spontaneous hydroxyl radical production and delayed lipid peroxidation. Mice in the high-dose linalool group exhibited a 55% reduction in mean xenograft tumor weight compared with mice in the control group (P < 0.05). In addition, tumor-specific lipid peroxidation was observed in the in vivo model.

CONCLUSION

Linalool exhibited an anticancer effect via cancer-specific oxidative stress, and this agent has potential for application in colon cancer therapy.

Keywords: Colorectal cancer; Linalool; Oxidative stress; Electron spin resonance; Lipid peroxidation

Core tip: We elucidated the anticancer mechanism of the monoterpenoid alcohol, linalool, which induces apoptosis specifically in cancer cells via lipid peroxidation. Electron spin resonance (ESR) spectroscopy, which enables the real-time visualization of free radicals in live cells, revealed that oxidative stress developed immediately after treatment only in cancer cells. This study demonstrated that the natural compound linalool exerted an anticancer effect without causing serious side effects, and that the further utilization of ESR may support the application of linalool as a new and cost-effective cancer therapy.