Visualizing the effect of tumor microenvironments on radiation-induced cell kinetics in multicellular spheroids consisting of HeLa cells

• Published in: Biochemical and biophysical research communications 2013-10, Vol.439 (4), p.453-458
• Main Authors: Kaida, Atsushi, Miura, Masahiko
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; ANIMAL TISSUES; CELL CULTURES; CELL CYCLE; FLUORESCENCE; Fluorescent Dyes; Fluorescent ubiquitination-based cell-cycle indicator (Fucci); G2 arrest; G2 Phase Cell Cycle Checkpoints - radiation effects; HELA CELLS; Humans; IRRADIATION; Kinetics; LASERS; NEOPLASMS; Radiation; Spheroid; SPHEROIDS; Spheroids, Cellular - pathology; Spheroids, Cellular - radiation effects; Spheroids, Cellular - ultrastructure; Tumor Cells, Cultured; Tumor microenvironment; Tumor Microenvironment - radiation effects; Ubiquitination
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2013.08.093

•We visualized radiation-induced cell kinetics in spheroids.•HeLa-Fucci cells were used for detection of cell-cycle changes.•Radiation-induced G2 arrest was prolonged in the spheroid.•The inner and outer cell fractions behaved differently. In this study, we visualized the effect of tumor microenvironments on radiation-induced tumor cell kinetics. For this purpose, we utilized a multicellular spheroid model, with a diameter of ∼500μm, consisting of HeLa cells expressing the fluorescent ubiquitination-based cell-cycle indicator (Fucci). In live spheroids, a confocal laser scanning microscope allowed us to clearly monitor cell kinetics at depths of up to 60μm. Surprisingly, a remarkable prolongation of G2 arrest was observed in the outer region of the spheroid relative to monolayer-cultured cells. Scale, an aqueous reagent that renders tissues optically transparent, allowed visualization deeper inside spheroids. About 16h after irradiation, a red fluorescent cell fraction, presumably a quiescent G0 cell fraction, became distinct from the outer fraction consisting of proliferating cells, most of which exhibited green fluorescence indicative of G2 arrest. Thereafter, the red cell fraction began to emit green fluorescence and remained in prolonged G2 arrest. Thus, for the first time, we visualized the prolongation of radiation-induced G2 arrest in spheroids and the differences in cell kinetics between the outer and inner fractions.