(A) Chemical structures of cytidine, AZA, and DAC, and the metabolic pathways of AZA (5-Aza-CR) and DAC (5-Aza-CdR). MP, DP, and TP, mono-, di-, and triphosphate, respectively; PPase, phosphatase; UrdK/CydK, uridine/cytidine kinase; dCydk, deoxycytidine kinase. (B) HCT116 cells were treated with different doses of AZA or DAC for 24 and 72 h. The cell viability at 72 h was analyzed by an MTT assay (upper part). Whole-cell lysates at 24 h were subjected to a Western blot analysis using antibodies against DNMT1 or GAPDH (lower part). (C) RKO, LoVo, HCT-15, DLD-1, and HT-29 cells were treated with different doses of AZA or DAC for 72 h, and the cell viability was analyzed by an MTT assay.