Figure 1

Apoptotic response of HCT116 parental and treatment-derivatives to transient 5-FU challenge for 24 hours. 5-FU was continuously present in the media of exponentially-growing cells for 24 hours. Apoptotic fractions were measured using the TUNEL assay as outlined in Materials and Methods. % apoptosis refers to the number of TdT-positive cells, i.e., cells that have been end-labeled with a biotin-labeled nucleotide and counterstained with a streptavidin-conjugated FITC fluorochrome.