Improved method for computing potential doubling time from flow cytometric data

Relative movement methods use the timed progression of the mean fluorescence of cells which have been labeled with monoclonal antibodies against bromodeoxyuridine and displayed with bivariate flow cytometry according to DNA and label content to compute duration of DNA synthesis, TS. The relative movement is the difference of the mean DNA fluorescence of the labeled undivided cells from the G1 channel relative to the difference between the G1 and G2M channels. In this communication, we show how to extend this method to compute the potential doubling time, Tpot, the time required for a population of cells to double, given quiescent cells but no cell loss. A quantity v is introduced that is a function of the fraction of labeled divided cells and the fraction of labeled undivided cells. We show that v is independent of time and is equal to ln(2)Ts/Tpot so that Tpot (equal to ln(2)Ts/v) can be directly found from the information available in computing the relative movement. The method is applied to Chinese hamster ovary cells to demonstrate its utility.