Effect of 5-dAzaC in conversion of E1 to E2 in HT29 (A) and SW707 (B) colorectal cancer cells. Cells were cultured in phenol red-free DMEM for 36 h either in the absence or in the presence of 5-dAzaC at a concentration of 1.00 μM for HT29 and SW707 cells. These cells were then further cultured either in the absence or the presence of E1 at a concentration of 10-2 mM. After 2, 4, 6, 8, 10 and 12 h, 0.5 ml of the medium was collected and the concentration of E2 was determined by electrochemiluminescence method. The results were expressed as E2 concentration in culture medium as nM per μg cell proteins. Each sample was determined in triplicate and results are presented as the mean ± SE from three experiments. The slope values were calculated according to nonlinear regression data fit from the log of Y axis values.