title: Visualizing the effect of tumor microenvironments on radiation-induced cell kinetics in multicellular spheroids consisting of HeLa cells.
abstract: 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 ∼500 μm, 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 60 μm. 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 16 h 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.
authors.affiliation: Section of Oral Radiation Oncology, Department of Oral Health Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kaida
authors.forename: Masahiko
authors.initials: M
authors.lastname: Miura
mesh_terms: D005456:Fluorescent Dyes; D059565:G2 Phase Cell Cycle Checkpoints / Q000528:radiation effects*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D018874:Spheroids, Cellular / Q000473:pathology / Q000528:radiation effects* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured; D059016:Tumor Microenvironment / Q000528:radiation effects*; D054875:Ubiquitination
chemical_list: D005456:Fluorescent Dyes
keywords: Fluorescent ubiquitination-based cell-cycle indicator (Fucci); G2 arrest; Radiation; Spheroid; Tumor microenvironment