Determination of late apoptosis and caspase activity of HeLa, SiHa and HaCaT cells after in vitro treatment with pentoxifylline or cisplatin either alone or in combinations. 24 hours later the cells were harvested and late apoptosis was determined by UV light microscopy using ethidium bromide and acridine orange stains, the results represent late apoptosis index (Figure 1A). Caspases-3, -6, - 7, -9 and -8 activation was determined by flow cytometry, the results represent the percentage of caspase activity (Figure 1B and 1C respectively). The results represent the mean ± SD of three independent experiments carried out in triplicate. Statistical analysis, Student's t test. (*) P < 0.001 vs CTL. (♦) P < 0.001 vs CIS.