Fig 3. SF767 and U87-MG cytotoxicity.

Average percentage survival of cells with increasing concentrations of chlorambucil (0.01 to 500 μM) against in vitro SF767 (gray dotted lines) and U87-MG (black solid lines) after 4 hours (A), 24 hours (B), and 48 hours (C) of exposure using Annexin V and 7-AAD and FACS analysis. Using the sum of the percentage of early apoptotic cells and late apoptotic cells as determined using FACS analysis, the LD₅₀ after 48 hours was 270 μM and 390 μM for SF767 and U87-MG glioma cell lines, respectively. Note that where the % survival relative to control is greater than 100%, this is explained by insignificant cytotoxicity and natural variation of non-drug dependent cell death at early time points and low drug dilutions, in which the fraction of surviving cells in the experimental wells at lower concentrations and earlier time points was greater than that in the control wells, resulting in an initial survival greater than 100%. As incubation time and drug concentration increase, cell death becomes greater than the control and the data are more informative.