Superior Effect of the Combination of Carbon-Ion Beam Irradiation and 5-Fluorouracil on Colorectal Cancer Stem Cells in vitro and in vivo

Abstract

Woong Sub Koom,1,2 Sei Sai,3 Masao Suzuki,3 Akira Fujimori,3 Shigeru Yamada,2 Hirohiko Tsujii2 1Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University, College of Medicine, Seoul, South Korea; 2QST Hospital, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan; 3Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, JapanCorrespondence: Sei SaiDepartment of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), National Institutes for Quantum and Radiological Science and Technology (QST), 4-9-1 Anagawa Inage-Ku, Chiba 263-8555, JapanTel [phone]Fax [phone]Email [email protected]: The aim of this study was to investigate whether carbon-ion beam irradiation in combination with 5-fluorouracil (5-FU) is superior to carbon-ion beam irradiation alone in targeting colorectal cancer stem-like cells (CSCs).Materials and Methods: Human colorectal cancer (CRC) cells, HCT116 and HT29, were treated with carbon-ion beam irradiation alone or in combination with 5-FU. Cell viability assay, colony and spheroid formation assay, apoptotic assay, and quantitative real-time PCR analysis of apoptosis- and autophagy-related gene expression were performed.Results: Carbon-ion beam irradiation dose-dependently decreased CRC cell viability and showed significantly enhanced cell killing effect when combined with 5-FU. Carbon-ion beam irradiation in combination with 5-FU significantly increased the percentage of apoptotic cells. The expression of some apoptotic and autophagy-related genes such as Bax, Bcl2, Beclin1 and ATG7 was significantly induced by carbon-ion beam irradiation alone and was further enhanced when the beam was combined with 5-FU. The spheroid forming capacity of CD133+ cell subpopulations was significantly inhibited by carbon-ion beam in combination with 5-FU. Histopathologically, the combination of carbon-ion beam irradiation and 5-FU destroyed more xenograft tumor cells, and resulted in increased necrosis, cavitation, and fibrosis, compared to carbon-ion beam irradiation alone.Conclusion: In conclusion, carbon-ion beam treatment combined with 5-FU has the potential to kill CRC cells including CSCs by inducing increased apoptosis and autophagy.Keywords: colorectal cancer stem cell, heavy ion radiation, 5-FU

Keywords

• colorectal cancer stem cell
• heavy ion radiation
• 5-fu