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The biological effect of 125I seed continuous low dose rate irradiation in CL187 cells.

Zhuang HQ, Wang JJ, Liao AY, Wang JD, Zhao Y - J. Exp. Clin. Cancer Res. (2009)

Bottom Line: The relative biological effect (RBE) for 125I seeds compared with 60Co gamma ray was 1.41.After low dose rate irradiation, EGFR and Raf expression increased, but when EGFR was blocked by a monoclonal antibody, EGFR and Raf expression did not change. 125I seeds resulted in more effective inhibition than 60Co gamma ray high dose rate irradiation in CL187 cells.CLDR could influence the proliferation of cells via MAPK signal transduction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, PR China. hongqingzh@163.com

ABSTRACT

Background: To investigate the effectiveness and mechanism of 125I seed continuous low-dose-rate irradiation on colonic cell line CL187 in vitro.

Methods: The CL187 cell line was exposed to radiation of 60Cogamma ray at high dose rate of 2 Gy/min and 125I seed at low dose rate of 2.77 cGy/h. Radiation responses to different doses and dose rates were evaluated by colony-forming assay. Under 125I seed low dose rate irradiation, a total of 12 culture dishes were randomly divided into 4 groups: Control group, and 2, 5, and 10 Gy irradiation groups. At 48 h after irradiation, apoptosis was detected by Annexin and Propidium iodide (PI) staining. Cell cycle arrests were detected by PI staining. In order to investigate the influence of low dose rate irradiation on the MAPK signal transduction, the expression changes of epidermal growth factor receptor (EGFR) and Raf under continuous low dose rate irradiation (CLDR) and/or EGFR monoclonal antibodies were determined by indirect immunofluorescence.

Results: The relative biological effect (RBE) for 125I seeds compared with 60Co gamma ray was 1.41. Apoptosis rates of CL187 cancer cells were 13.74% +/- 1.63%, 32.58% +/- 3.61%, and 46.27% +/- 3.82% after 2 Gy, 5 Gy, and 10 Gy irradiation, respectively; however, the control group apoptosis rate was 1.67% +/- 0.19%. G2/M cell cycle arrests of CL187 cancer cells were 42.59% +/- 3.21%, 59.84% +/- 4.96%, and 34.61% +/- 2.79% after 2 Gy, 5 Gy, and 10 Gy irradiation, respectively; however, the control group apoptosis rate was 26.44% +/- 2.53%. P < 0.05 vs. control groups by Student's t-test were found in every treated group both in apoptosis and in G2/M cell cycle arrest. After low dose rate irradiation, EGFR and Raf expression increased, but when EGFR was blocked by a monoclonal antibody, EGFR and Raf expression did not change.

Conclusion: 125I seeds resulted in more effective inhibition than 60Co gamma ray high dose rate irradiation in CL187 cells. Apoptosis following G2/M cell cycle arrest was the main mechanism of cell-killing effects under low dose rate irradiation. CLDR could influence the proliferation of cells via MAPK signal transduction.

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Effect of 125I low dose rate irradiation on the cell cycle in CL187 cells. Flow cytometry analysis revealed that the G2/M phase increased by 2 Gy (B)125I irradiation dose as compared with untreated control cells (A). After 5 Gy irradiation (C), a sharp increase in the fraction of cells in the G2/M phase was observed. The result in 10 Gy irradiation groups (D) was lower than that in group C, but sustained at a relatively high level. Compared with untreated control cells, P < 0.05 were found in all of the treated groups.
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Figure 4: Effect of 125I low dose rate irradiation on the cell cycle in CL187 cells. Flow cytometry analysis revealed that the G2/M phase increased by 2 Gy (B)125I irradiation dose as compared with untreated control cells (A). After 5 Gy irradiation (C), a sharp increase in the fraction of cells in the G2/M phase was observed. The result in 10 Gy irradiation groups (D) was lower than that in group C, but sustained at a relatively high level. Compared with untreated control cells, P < 0.05 were found in all of the treated groups.

Mentions: Cells were stained by acridine orange and observed under fluorescence microscopy; typical morphological features of apoptotic cells appeared after 5 Gy low dose rate irradiation (Fig. 3). FCM analysis showed that under low dose rate irradiation, apoptosis and G2/M cell cycle arrest increased slightly at 2 Gy, the peak appeared at 5 Gy, and the ratio was also high at 10 Gy (Table 2) but lower than that at 5 Gy. Furthermore, G2/M cell cycle arrest and apoptosis walked together along with the dose change (r = 0.918, P < 0.01, Fig. 4). Quantitative measurements of apoptotic cell death by FCM in CL187 cells sufficiently indicated that apoptosis is an important mechanism of low dose rate irradiation inhibition of CL187 cell proliferation.


The biological effect of 125I seed continuous low dose rate irradiation in CL187 cells.

Zhuang HQ, Wang JJ, Liao AY, Wang JD, Zhao Y - J. Exp. Clin. Cancer Res. (2009)

Effect of 125I low dose rate irradiation on the cell cycle in CL187 cells. Flow cytometry analysis revealed that the G2/M phase increased by 2 Gy (B)125I irradiation dose as compared with untreated control cells (A). After 5 Gy irradiation (C), a sharp increase in the fraction of cells in the G2/M phase was observed. The result in 10 Gy irradiation groups (D) was lower than that in group C, but sustained at a relatively high level. Compared with untreated control cells, P < 0.05 were found in all of the treated groups.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2655271&req=5

Figure 4: Effect of 125I low dose rate irradiation on the cell cycle in CL187 cells. Flow cytometry analysis revealed that the G2/M phase increased by 2 Gy (B)125I irradiation dose as compared with untreated control cells (A). After 5 Gy irradiation (C), a sharp increase in the fraction of cells in the G2/M phase was observed. The result in 10 Gy irradiation groups (D) was lower than that in group C, but sustained at a relatively high level. Compared with untreated control cells, P < 0.05 were found in all of the treated groups.
Mentions: Cells were stained by acridine orange and observed under fluorescence microscopy; typical morphological features of apoptotic cells appeared after 5 Gy low dose rate irradiation (Fig. 3). FCM analysis showed that under low dose rate irradiation, apoptosis and G2/M cell cycle arrest increased slightly at 2 Gy, the peak appeared at 5 Gy, and the ratio was also high at 10 Gy (Table 2) but lower than that at 5 Gy. Furthermore, G2/M cell cycle arrest and apoptosis walked together along with the dose change (r = 0.918, P < 0.01, Fig. 4). Quantitative measurements of apoptotic cell death by FCM in CL187 cells sufficiently indicated that apoptosis is an important mechanism of low dose rate irradiation inhibition of CL187 cell proliferation.

Bottom Line: The relative biological effect (RBE) for 125I seeds compared with 60Co gamma ray was 1.41.After low dose rate irradiation, EGFR and Raf expression increased, but when EGFR was blocked by a monoclonal antibody, EGFR and Raf expression did not change. 125I seeds resulted in more effective inhibition than 60Co gamma ray high dose rate irradiation in CL187 cells.CLDR could influence the proliferation of cells via MAPK signal transduction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, PR China. hongqingzh@163.com

ABSTRACT

Background: To investigate the effectiveness and mechanism of 125I seed continuous low-dose-rate irradiation on colonic cell line CL187 in vitro.

Methods: The CL187 cell line was exposed to radiation of 60Cogamma ray at high dose rate of 2 Gy/min and 125I seed at low dose rate of 2.77 cGy/h. Radiation responses to different doses and dose rates were evaluated by colony-forming assay. Under 125I seed low dose rate irradiation, a total of 12 culture dishes were randomly divided into 4 groups: Control group, and 2, 5, and 10 Gy irradiation groups. At 48 h after irradiation, apoptosis was detected by Annexin and Propidium iodide (PI) staining. Cell cycle arrests were detected by PI staining. In order to investigate the influence of low dose rate irradiation on the MAPK signal transduction, the expression changes of epidermal growth factor receptor (EGFR) and Raf under continuous low dose rate irradiation (CLDR) and/or EGFR monoclonal antibodies were determined by indirect immunofluorescence.

Results: The relative biological effect (RBE) for 125I seeds compared with 60Co gamma ray was 1.41. Apoptosis rates of CL187 cancer cells were 13.74% +/- 1.63%, 32.58% +/- 3.61%, and 46.27% +/- 3.82% after 2 Gy, 5 Gy, and 10 Gy irradiation, respectively; however, the control group apoptosis rate was 1.67% +/- 0.19%. G2/M cell cycle arrests of CL187 cancer cells were 42.59% +/- 3.21%, 59.84% +/- 4.96%, and 34.61% +/- 2.79% after 2 Gy, 5 Gy, and 10 Gy irradiation, respectively; however, the control group apoptosis rate was 26.44% +/- 2.53%. P < 0.05 vs. control groups by Student's t-test were found in every treated group both in apoptosis and in G2/M cell cycle arrest. After low dose rate irradiation, EGFR and Raf expression increased, but when EGFR was blocked by a monoclonal antibody, EGFR and Raf expression did not change.

Conclusion: 125I seeds resulted in more effective inhibition than 60Co gamma ray high dose rate irradiation in CL187 cells. Apoptosis following G2/M cell cycle arrest was the main mechanism of cell-killing effects under low dose rate irradiation. CLDR could influence the proliferation of cells via MAPK signal transduction.

Show MeSH
Related in: MedlinePlus