Demethylation restores SN38 sensitivity in cells with acquired resistance to SN38 derived from human cervical squamous cancer cells

Oncol Rep. 2012 Apr;27(4):1292-8. doi: 10.3892/or.2012.1628. Epub 2012 Jan 11.


Using seven monoclonal SN38-resistant subclones established from ME180 human cervical squamous cell carcinoma cells, we examined the demethylation effects of 5-aza-2'-deoxycytidine (5-aza-CdR) on the SN38-sensitivity of the cells as well as the expression of death-associated protein kinase (DAPK) in the SN38-resistant cells. The DAPK expression levels were evaluated among parent ME180 cells, SN38-resistant ME180 cells and cisplatin-resistant ME180 cells by methylation-specific DAPK-PCR, quantitative RT-PCR and western blot analysis. The SN38-resistant cells co-treated with SN38 and 5-aza-CdR strongly exhibited enhanced SN38-sensitivities resembling those found in the parent cells. In the SN38-resistant subclones, no relationships were found between the restored SN38 sensitivity and hypermethylation of the DAPK promoter, DAPK mRNA expression, DAPK protein expression and induction of DAPK protein after 5-aza-CdR treatment, unlike the strong suppression of 5-aza-CdR-induced DAPK protein expression in the cisplatin-resistant subclones. These findings indicate that reversibly methylated molecules, but not DAPK, may regulate SN38 resistance, and that demethylating agents can be strong sensitizing anticancer chemotherapeutic drugs for SN38-resistant cancers.

MeSH terms

  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Azacitidine / analogs & derivatives*
  • Azacitidine / pharmacology
  • Calcium-Calmodulin-Dependent Protein Kinases / genetics
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology
  • Carcinoma, Squamous Cell / enzymology*
  • Carcinoma, Squamous Cell / genetics
  • Carcinoma, Squamous Cell / pathology
  • Cell Line, Tumor
  • Cisplatin / pharmacology
  • DNA Modification Methylases / antagonists & inhibitors*
  • DNA Modification Methylases / metabolism
  • Dealkylation
  • Death-Associated Protein Kinases
  • Decitabine
  • Dose-Response Relationship, Drug
  • Drug Resistance, Neoplasm / drug effects*
  • Enzyme Inhibitors / pharmacology*
  • Female
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Irinotecan
  • Promoter Regions, Genetic
  • RNA, Messenger / metabolism
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription, Genetic / drug effects
  • Uterine Cervical Neoplasms / enzymology*
  • Uterine Cervical Neoplasms / genetics
  • Uterine Cervical Neoplasms / pathology


  • Antineoplastic Agents, Phytogenic
  • Apoptosis Regulatory Proteins
  • Enzyme Inhibitors
  • RNA, Messenger
  • Irinotecan
  • Decitabine
  • DNA Modification Methylases
  • Death-Associated Protein Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Azacitidine
  • Cisplatin
  • Camptothecin