PMID: 8955708Dec 1, 1996Paper

Development of apoptosis and polyploidy in human lymphoblast cells as a function of position in the cell cycle at the time of irradiation

Radiation Research
P L OliveR E Durand

Abstract

The TK6 and WI-L2-NS human lymphoblast cell lines are derived from the same donor, but WI-L2-NS cells are more resistant to killing by ionizing radiation and also contain a mutation in the coding region of the p53 gene which delays the appearance of apoptosis. To determine whether the difference in radiosensitivity is a result of the slower rate of appearance of apoptosis (referred to as the rate of apoptosis) or to other factors related to the function of p53 such as the G1-phase checkpoint, we have examined the clonogenicity and rates of apoptosis in synchronous populations of these two cell lines as a function of time after exposure to x-rays. The greater radiosensitivity of G1-phase TK6 cells compared to G1-phase WI-L2-NS cells appeared adequate to explain the difference in radiosensitivity of asynchronous cultures. However, TK6 cells irradiated in G1 phase underwent apoptosis about three times more slowly than cells irradiated in other phases of the cycle, cautioning against equating more rapid apoptosis with greater radiosensitivity. The slower rate of apoptosis of G1-phase TK6 cells could not be explained by a radiation-induced block in G1 phase since there was only a short delay in exit of cells from G1 phase. Giant cel...Continue Reading

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