Apoptosis of cMycCHO compared to CHO-K1 cultures in exponential growth (a) and spent medium (b). Cells were analysed by staining with Annexin V-FITC and PI for counting viable (none stained), early apoptotic (Annexin V-FITC staining), late apoptotic (both Annexin V-FITC and PI staining) and necrotic cells (PI staining only) at 0, 25, 44, and 118 hours. Under t-Test criteria, p < 0.05 for viable and apoptotic cells with n = 3. Spent medium was obtained from the end of the death phase of batch culture. Cells from both cell lines were incubated in spent medium for up to 118 hrs.