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Unusual prolongation of radiation-induced G2 arrest in tumor xenografts derived from HeLa cells.

Kaida A, Miura M - Cancer Sci. (2015)

Bottom Line: The effect of ionizing radiation on cell cycle kinetics in solid tumors remains largely unknown because of technical limitations and these tumors' complicated structures.We found that G2 arrest was remarkably prolonged, up to 5 days after 10-Gy irradiation, in contrast to monolayer cultures where G2 arrest returned within 24 h.Cells isolated from tumors 5 days after irradiation exhibited a higher surviving fraction than those isolated immediately or one day after irradiation.

View Article: PubMed Central - PubMed

Affiliation: Section of Oral Radiation Oncology, Department of Oral Health Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.

No MeSH data available.


Related in: MedlinePlus

Effect on cell survival of prolonged G2 arrest observed in vivo following irradiation (a) Fluorescence kinetics of HeLa-Fucci cells isolated from a tumor xenograft following irradiation. The tumor xenograft was excised one day after 10-Gy irradiation and a single cell suspension was prepared for time-lapse imaging. (b) Schematic presentation of experimental design to assess survival of tumor cells isolated from tumor xenografts following irradiation. Tumor xenografts were irradiated at a dose of 10 Gy and single cell suspensions were prepared for clonogenic assay. Red and green represent Fucci fluorescence, reflecting G2 arrest kinetics following irradiation. (c) Surviving fractions of tumor cells isolated from tumor xenografts at the indicated times after 10-Gy irradiation. Data are means ± SD from three independent experiments. *P <0.05.
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fig04: Effect on cell survival of prolonged G2 arrest observed in vivo following irradiation (a) Fluorescence kinetics of HeLa-Fucci cells isolated from a tumor xenograft following irradiation. The tumor xenograft was excised one day after 10-Gy irradiation and a single cell suspension was prepared for time-lapse imaging. (b) Schematic presentation of experimental design to assess survival of tumor cells isolated from tumor xenografts following irradiation. Tumor xenografts were irradiated at a dose of 10 Gy and single cell suspensions were prepared for clonogenic assay. Red and green represent Fucci fluorescence, reflecting G2 arrest kinetics following irradiation. (c) Surviving fractions of tumor cells isolated from tumor xenografts at the indicated times after 10-Gy irradiation. Data are means ± SD from three independent experiments. *P <0.05.

Mentions: We previously reported that the release from radiation-induced G2 arrest was accelerated by attaching spheroids to the bottom of the culture dish.14 G2-arrested cells isolated from a tumor xenograft one day or 5 days after irradiation were more rapidly released from G2 arrest when attached to a culture dish (Fig.4a, Suppl. Fig. S4) than cells in an in vivo condition (Fig.2). This rapid release from prolonged G2 arrest prompted us to consider the possibility of induction of radiosensitization. We therefore examined cell survival in tumor cells isolated from tumor xenografts at various times after irradiation (Fig.4b). The surviving fraction significantly increased in isolated tumor cells 5 days after irradiation, compared to those isolated immediately or one day after irradiation (Fig.4c). The trypan blue exclusion test showed that cell viability of isolated tumor cells was similar between non-irradiated tumors and tumors one day or five days after irradiation, and there were no significant changes (Control: 63.67% ± 12.4%; Day 1: 52.9% ± 5.4%; Day 5: 55.1% ± 15.7%). Also, the mean tumor volume on Day 6 decreased to 90.5% ± 10.5% of that before irradiation, but this difference was not significant. Thus, we speculate that the increase in the surviving fraction on Day 5 was not an artifact of cell loss at the early time. Taken together, we reasoned that the prolonged G2 arrest served in vivo after irradiation is likely to contribute to a potential radioresistance mechanism.


Unusual prolongation of radiation-induced G2 arrest in tumor xenografts derived from HeLa cells.

Kaida A, Miura M - Cancer Sci. (2015)

Effect on cell survival of prolonged G2 arrest observed in vivo following irradiation (a) Fluorescence kinetics of HeLa-Fucci cells isolated from a tumor xenograft following irradiation. The tumor xenograft was excised one day after 10-Gy irradiation and a single cell suspension was prepared for time-lapse imaging. (b) Schematic presentation of experimental design to assess survival of tumor cells isolated from tumor xenografts following irradiation. Tumor xenografts were irradiated at a dose of 10 Gy and single cell suspensions were prepared for clonogenic assay. Red and green represent Fucci fluorescence, reflecting G2 arrest kinetics following irradiation. (c) Surviving fractions of tumor cells isolated from tumor xenografts at the indicated times after 10-Gy irradiation. Data are means ± SD from three independent experiments. *P <0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4638018&req=5

fig04: Effect on cell survival of prolonged G2 arrest observed in vivo following irradiation (a) Fluorescence kinetics of HeLa-Fucci cells isolated from a tumor xenograft following irradiation. The tumor xenograft was excised one day after 10-Gy irradiation and a single cell suspension was prepared for time-lapse imaging. (b) Schematic presentation of experimental design to assess survival of tumor cells isolated from tumor xenografts following irradiation. Tumor xenografts were irradiated at a dose of 10 Gy and single cell suspensions were prepared for clonogenic assay. Red and green represent Fucci fluorescence, reflecting G2 arrest kinetics following irradiation. (c) Surviving fractions of tumor cells isolated from tumor xenografts at the indicated times after 10-Gy irradiation. Data are means ± SD from three independent experiments. *P <0.05.
Mentions: We previously reported that the release from radiation-induced G2 arrest was accelerated by attaching spheroids to the bottom of the culture dish.14 G2-arrested cells isolated from a tumor xenograft one day or 5 days after irradiation were more rapidly released from G2 arrest when attached to a culture dish (Fig.4a, Suppl. Fig. S4) than cells in an in vivo condition (Fig.2). This rapid release from prolonged G2 arrest prompted us to consider the possibility of induction of radiosensitization. We therefore examined cell survival in tumor cells isolated from tumor xenografts at various times after irradiation (Fig.4b). The surviving fraction significantly increased in isolated tumor cells 5 days after irradiation, compared to those isolated immediately or one day after irradiation (Fig.4c). The trypan blue exclusion test showed that cell viability of isolated tumor cells was similar between non-irradiated tumors and tumors one day or five days after irradiation, and there were no significant changes (Control: 63.67% ± 12.4%; Day 1: 52.9% ± 5.4%; Day 5: 55.1% ± 15.7%). Also, the mean tumor volume on Day 6 decreased to 90.5% ± 10.5% of that before irradiation, but this difference was not significant. Thus, we speculate that the increase in the surviving fraction on Day 5 was not an artifact of cell loss at the early time. Taken together, we reasoned that the prolonged G2 arrest served in vivo after irradiation is likely to contribute to a potential radioresistance mechanism.

Bottom Line: The effect of ionizing radiation on cell cycle kinetics in solid tumors remains largely unknown because of technical limitations and these tumors' complicated structures.We found that G2 arrest was remarkably prolonged, up to 5 days after 10-Gy irradiation, in contrast to monolayer cultures where G2 arrest returned within 24 h.Cells isolated from tumors 5 days after irradiation exhibited a higher surviving fraction than those isolated immediately or one day after irradiation.

View Article: PubMed Central - PubMed

Affiliation: Section of Oral Radiation Oncology, Department of Oral Health Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.

No MeSH data available.


Related in: MedlinePlus