Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Feb 28, 2015; 21(8): 2336-2342
Published online Feb 28, 2015. doi: 10.3748/wjg.v21.i8.2336
Biological effects of low-dose-rate irradiation of pancreatic carcinoma cells in vitro using 125I seeds
Zhong-Min Wang, Jian Lu, Li-Yun Zhang, Xiao-Zhu Lin, Ke-Min Chen, Zhi-Jin Chen, Fen-Ju Liu, Fu-Hua Yan, Gao-Jun Teng, Ai-Wu Mao
Zhong-Min Wang, Jian Lu, Li-Yun Zhang, Zhi-Jin Chen, Department of Radiology, Ruijin Hospital Luwan Branch, Shanghai Jiao Tong University School of Medicine, Shanghai 200020, China
Zhong-Min Wang, Institution of Molecular Imaging, Southeast University, Nanjing 210009, China; Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
Jian Lu, Li-Yun Zhang, Soochow University School of Medicine, Soochow 215123, Jiangsu Province, China
Xiao-Zhu Lin, Ke-Min Chen, Fu-Hua Yan, Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
Fen-Ju Liu, Department of Radiobiology, School of Radiological Medicine and Protection, Soochow University, Soochow 215123, Jiangsu Province, China
Gao-Jun Teng, Institution of Molecular Imaging, Southeast University, Nanjing 210009, Jiangsu Province, China
Ai-Wu Mao, Department of Interventional Radiology, Shanghai St. Luke’s Hospital, Shanghai 200050, China
Author contributions: Wang ZM and Lu J contributed equally to this work. Wang ZM, Lu J, Lin XZ, Chen KM, Liu FJ, Teng GJ, and Mao AW designed the research; Lu J, Lin XZ, Zhang LY, Chen ZJ, and Liu FJ performed the research; Wang ZM, Lu J, Lin XZ, Zhang LY, Chen ZJ, and Liu FJ analyzed the data; and Lu J, Lin XZ, and Liyun Zhang wrote the paper. All authors read and approved the final manuscript.
Supported by Natural Science Foundation of China, No. 81271682 (partly); and grants from Science and Technology Commission of Shanghai Municipality, No. 11JC1407400 (partly); the project of Luwan District Science and Technology Commission of Shanghai, No. LKW1104 (partly); the project of Medical Key Specialty of Shanghai Municipality, No. ZK2012A20 (partly).
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: Ai-Wu Mao, MD, Professor, Department of Interventional Radiology, Shanghai St. Luke’s Hospital, No. 786 Yu Yuan Road, Shanghai 200050, China. james0722@163.com
Telephone: +86-21-62524259 Fax: +86-21-62113884
Received: August 17, 2014
Peer-review started: August 17, 2014
First decision: September 15, 2014
Revised: September 30, 2014
Accepted: December 8, 2014
Article in press: December 8, 2014
Published online: February 28, 2015
Abstract

AIM: To determine the mechanism of the radiation-induced biological effects of 125I seeds on pancreatic carcinoma cells in vitro.

METHODS: SW1990 and PANC-1 pancreatic cancer cell lines were cultured in DMEM in a suitable environment. Gray’s model of iodine-125 (125I) seed irradiation was used. In vitro, exponential phase SW1990, and PANC-1 cells were exposed to 0, 2, 4, 6, and 8 Gy using 125I radioactive seeds, with an initial dose rate of 12.13 cGy/h. A clonogenic survival experiment was performed to observe the ability of the cells to maintain their clonogenic capacity and to form colonies. Cell-cycle and apoptosis analyses were conducted to detect the apoptosis percentage in the SW1990 and PANC-1 cells. DNA synthesis was measured via a tritiated thymidine (3H-TdR) incorporation experiment. After continuous low-dose-rate irradiation with 125I radioactive seeds, the survival fractions at 2 Gy (SF2), percentage apoptosis, and cell cycle phases of the SW1990 and PANC-1 pancreatic cancer cell lines were calculated and compared.

RESULTS: The survival fractions of the PANC-1 and SW1990 cells irradiated with 125I seeds decreased exponentially as the dose increased. No significant difference in SF2 was observed between SW1990 and PANC-1 cells (0.766 ± 0.063 vs 0.729 ± 0.045, P < 0.05). The 125I seeds induced a higher percentage of apoptosis than that observed in the control in both the SW1990 and PANC-1 cells. The rate of apoptosis increased with increasing radiation dosage. The percentage of apoptosis was slightly higher in the SW1990 cells than in the PANC-1 cells. Dose-dependent G2/M cell-cycle arrest was observed after 125I seed irradiation, with a peak value at 6 Gy. As the dose increased, the percentage of G2/M cell cycle arrest increased in both cell lines, whereas the rate of DNA incorporation decreased. In the 3H-TdR incorporation experiment, the dosimetry results of both the SW1990 and PANC-1 cells decreased as the radiation dose increased, with a minimum at 6 Gy. There were no significant differences in the dosimetry results of the two cell lines when they were exposed to the same dose of radiation.

CONCLUSION: The pancreatic cancer cell-killing effects induced by 125I radioactive seeds mainly occurred via apoptosis and G2/M cell cycle arrest.

Keywords: 125I radioactive seeds, Biological effects, Pancreatic cancer, SW1990, PANC-1

Core tip: We compared the radiobiological effects observed in SW1990 and PANC-1 pancreatic cancer cell lines after irradiation with 125I seeds through a clonogenic cell survival assay and 3H-TdR incorporation experiment. Continuous low-dose-rate irradiation with 125I seeds was found to induce apoptosis and G2/M cell cycle arrest.