Heterogeneous cell-cycle behavior in response to UVB irradiation by a population of single cancer cells visualized by time-lapse FUCCI imaging

The present study analyzed the heterogeneous cell-cycle dependence and fate of single cancer cells in a population treated with UVB using a fluorescence ubiquitination-based cell-cycle (FUCCI) imaging system. HeLa cells expressing FUCCI were irradiated by 100 or 200 J/m(2) UVB. Modulation of the cell-cycle and apoptosis were observed by time-lapse confocal microscopy imaging every 30min for 72h. Correlation between cell survival and factors including cell-cycle phase at the time of the irradiation of UVB, mitosis and the G(1)/S transition were analyzed using the Kaplan-Meier method along with the log rank test. Time-lapse FUCCI imaging of HeLa cells demonstrated that UVB irradiation induced cell-cycle arrest in S/G(2)/M phase in the majority of the cells. The cells irradiated by 100 or 200 J/m(2) UVB during G(0)/G(1) phase had a higher survival rate than the cells irradiated during S/G(2)/M phase. A minority of cells could escape S/G(2)/M arrest and undergo mitosis which significantly correlated with decreased survival of the cells. In contrast, G(1)/S transition significantly correlated with increased survival of the cells after UVB irradiation. UVB at 200 J/m(2) resulted in a greater number of apoptotic cells.