1Department of Radiology, Suzhou Kowloon Hospital, Medical School of Shanghai Jiaotong University, Suzhou   215021, Jiangsu Province, China

2Department of Radiology, the First Affiliated Hospital of Soochow University, Suzhou   215006, Jiangsu Province, China

Chao Li, Attending physician, Department of Radiology, Suzhou Kowloon Hospital, Medical School of Shanghai Jiaotong University, Suzhou 215021, Jiangsu Province, China Li C, Li L, Xu CS, Zhou JY. Growth and radiosensitivity of irradiated human glioma cell progeny. Neural Regen Res 2008;3(5):542-5

Abstract

BACKGROUND: Progenitors of the immortalized human glioma cell line, SHG-44, are significantly less sensitive to irradiation. Two hypotheses regarding the mechanism of this effect exist: several studies have suggested that there is a subgroup with different radiosensitivities in identical cell group, and the progenitors of irradiate is a adaptive response subgroup, so its radiosensitivity is descend. A second hypothesis suggests that irradiated glioma progeny have a stronger ability to repair DNA damage. This would suggest that when progeny are continuously irradiated, resistance to irradiation-induced DNA increases, and radiosensitivity decreases.

OBJECTIVE: To investigate radiosensitivity and growth features after irradiation to progeny of the human glioma cell line SHG-44.

DESIGN, TIME AND SETTING: A randomized, controlled experiment, which was performed at the Department of Radiology Laboratory, the First Hospital Affiliated to Soochow University, between September 2004 and January 2006.

MATERIALS: The glioma cell line SHG-44 was provided by the Institute of Neuroscience, First Affiliated Hospital of Suzhou University. Propidium iodide reagent was provided by Coulter Corporation. A linear accelerator, KD-2 type, was provided by Siemens, Germany. The flow cytometer EPICS-XL was provided by Coulter Corporation.

METHODS: Brain glioma SHG-44 cells were divided into four groups: SHG-44, SHG-44-2, SHG-44-6, and SHG-44-10 . The SHG-44-2, SHG-44-6, and SHG-44-10 cells were vertically irradiated with varying doses of 2, 6 and 10 Gy by a linear accelerator (6 MVX). The cells were passaged for 15 generations and cultured in RPMI-1640 culture media.

MAIN OUTCOME MEASURES: Community re-double time, mean lethal dose (D₀), extrapolation number (N), fraction surviving fraction irradiated by 2 Gy dose (SF₂), quasi-threshold dose (Dq), and cell cycle.

RESULTS: The Population doubling time (PDT) of SHG-44-2, SHG-44-6, and SHG-44-10 cell groups was not significant (P = 0.052). Compared to these three groups, the PDT of the SHG-44 cell group was significantly difference (F = 7.878, P < 0.002). SHG-44 cell clone rate was 26.5%, and SHG-44-10 cell group was 15.5%. The SHG-44-10 cell group also exhibited radiosensitivity, but was less than the radiosensitivity of the SHG-44 cell group. Compared to the SHG-44 cell group, the ratio of the G₂/M phase was decreased in the SHG-44-10 cell group, and the radio of S phase was increased. The SHG-44 and SHG-44-10 cell groups were irradiated with 8 Gy. After 12 hours, the G₂/M ratio was compared to pre-irradiation times, indicating a significantly higher ratio in the pre-irradiated groups (P < 0.01). The cells between SHG-44 and SHG-44-10 groups were harvested 12 hours after irradiation: G₂ phase of SHG-44-10 cells was arrested and the G₂/M ratio was increased, which was intensified with increasing irradiation doses.

CONCLUSION: In the present study, the proliferation delay and decreased radiosensitivity were confirmed in progeny of irradiated human glioma cells, and radiosensitivity was dose-dependent.

Key Words: glioma cell line SHG-44; irradiation; progenitor cell; radiosensitivity; cell cycle

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