Pharmacologic mechanisms of resistance to DAC. (A) DNMT1 protein expression was cell replication–dependent. We measured RKO cell growth curve, and DNMT1 protein expression on days 1, 3, and 5 by Western blot analysis. β-Actin was used as a control. (B) DNMT1, 3a, and 3b protein expression was independent of sensitivity to DAC and LINE methylation in different cancer cell lines. We collected exponentially growing cancer cells, extracted protein, and performed Western blot analysis of DNMT1, 3a, and 3b. β-Actin was used as a control. (C) dCK protein expression in several cell lines. dCK protein expression was measured by Western blot analysis. (D) Correlation of different nucleoside metabolic gene expression with the IC₅₀ of DAC. DCK, CDA, hENT1, and hENT2 expressions were measured by real-time PCR using glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as a control. R and P values reflect Spearman correlation analysis of the IC₅₀ of DAC with the relative gene expression.