The synergistic effect of 5-aza-2'-deoxycytidine and 5-fluorouracil on drug-resistant tumors

Oncology. 2006;71(5-6):437-45. doi: 10.1159/000107110. Epub 2007 Aug 9.


Purpose: We investigated whether a 5-fluorouracil (5-FU)-resistant tumor could regain chemosensitivity after the administration of 5-aza-2'-deoxycytidine (DAC) as a demethylating agent.

Methods: Human colorectal cancer cells (SW48) are characterized by the hypermethylation of proapoptotic genes. They were transplanted into 20 athymic BALB/c nu/nu mice which were randomly placed into 4 groups (1 = control; 2 = 5-FU alone; 3 = DAC alone; 4 = DAC followed by 5-FU). We evaluated the synergistic effect of DAC and 5-FU on the growth of these xenografts. Reactivation of proapoptotic genes in these cells was analyzed by methylation-specific PCR. Gene expression was determined by a quantitative reverse-transcription PCR assay.

Results: Compared with the control group, relative tumor volumes were statistically significantly decreased only in group 4 mice (p = 0.006). In groups 3 and 4, p14, p16 and death-associated protein kinase (DAPK) promoter regions were demethylated and p14 gene expression was gradually increased after DAC administration.

Conclusion: DAC could be a useful medicine that breaks the silencing of various genes and recovers some expressions. By pretreating with DAC at a nontoxic level, we confirmed the restoration of 5-FU chemosensitivity and apoptosis induction. The combination of demethylating agents and several cytotoxic drugs has potential in clinical practice.

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis Regulatory Proteins / biosynthesis
  • Apoptosis Regulatory Proteins / genetics
  • Azacitidine / analogs & derivatives*
  • Azacitidine / pharmacology
  • Calcium-Calmodulin-Dependent Protein Kinases / biosynthesis
  • Calcium-Calmodulin-Dependent Protein Kinases / genetics
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / pathology
  • Cyclin-Dependent Kinase Inhibitor p16 / biosynthesis
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics
  • DNA Methylation / drug effects
  • Death-Associated Protein Kinases
  • Decitabine
  • Drug Resistance, Neoplasm* / drug effects
  • Drug Resistance, Neoplasm* / genetics
  • Drug Synergism
  • Fluorouracil / pharmacology*
  • Humans
  • Mice
  • Mice, Nude
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Suppressor Protein p14ARF / biosynthesis
  • Tumor Suppressor Protein p14ARF / genetics
  • Up-Regulation* / drug effects
  • Xenograft Model Antitumor Assays


  • Apoptosis Regulatory Proteins
  • Cyclin-Dependent Kinase Inhibitor p16
  • Tumor Suppressor Protein p14ARF
  • Decitabine
  • Death-Associated Protein Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Azacitidine
  • Fluorouracil