title: Importance of dose-schedule of 5-aza-2'-deoxycytidine for epigenetic therapy of cancer.
abstract: BACKGROUND
  The inactivation of tumor suppressor genes (TSGs) by aberrant DNA methylation plays an important role in the development of malignancy. Since this epigenetic change is reversible, it is a potential target for chemotherapeutic intervention using an inhibitor of DNA methylation, such as 5-aza-2'-deoxycytidine (DAC). Although clinical studies show that DAC has activity against hematological malignancies, the optimal dose-schedule of this epigenetic agent still needs to be established.
  
  
  METHODS
  Clonogenic assays were performed on leukemic and tumor cell lines to evaluate the in vitro antineoplastic activity of DAC. The reactivation of TSGs and inhibition of DNA methylation by DAC were investigated by reverse transcriptase-PCR and Line-1 assays. The in vivo antineoplastic activity of DAC administered as an i.v. infusion was evaluated in mice with murine L1210 leukemia by measurement of survival time, and in mice bearing murine EMT6 mammary tumor by excision of tumor after chemotherapy for an in vitro clonogenic assay.
  
  
  RESULTS
  Increasing the DAC concentration and duration of exposure produced a greater loss of clonogenicity for both human leukemic and tumor cell lines. The reactivation of the TSGs (p57KIP2 in HL-60 leukemic cells and p16CDKN2A in Calu-6 lung carcinoma cells) and the inhibition of global DNA methylation in HL-60 leukemic cells increased with DAC concentration. In mice with L1210 leukemia and in mice bearing EMT6 tumors, the antineoplastic action of DAC also increased with the dose. The plasma level of DAC that produced a very potent antineoplastic effect in mice with leukemia or solid tumors was > 200 ng/ml (> 1 microM).
  
  
  CONCLUSIONS
  We have shown that intensification of the DAC dose markedly increased its antineoplastic activity in mouse models of cancer. Our data also show that there is a good correlation between the concentrations of DAC that reduce in vitro clonogenicity, reactivate TSGs and inhibit DNA methylation. These results suggest that the antineoplastic action of DAC is related to its epigenetic action. Our observations provide a strong rationale to perform clinical trials using dose intensification of DAC to maximize the chemotherapeutic potential of this epigenetic agent in patients with cancer.
authors.affiliation: Département de pharmacologie, Université de Montréal, Centre de recherche pédiatrique, Service d'Hématologie-Oncologie, Hôpital Sainte-Justine, 3175 Côte Sainte-Catherine, Montréal, Québec H3T 1C5, Canada. maryse_lemaire@yahoo.fr
authors.forename: Maryse
authors.initials: M
authors.lastname: Lemaire
authors.forename: Guy G
authors.initials: GG
authors.lastname: Chabot
authors.forename: Noël Jm
authors.initials: NJ
authors.lastname: Raynal
authors.forename: Louise F
authors.initials: LF
authors.lastname: Momparler
authors.forename: Annie
authors.initials: A
authors.lastname: Hurtubise
authors.forename: Mark L
authors.initials: ML
authors.lastname: Bernstein
authors.forename: Richard L
authors.initials: RL
authors.lastname: Momparler
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D001374:Azacitidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D045744:Cell Line, Tumor; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D044127:Epigenesis, Genetic / Q000187:drug effects*; D018392:Genomic Imprinting / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D051379:Mice; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000473:pathology; D014410:Tumor Stem Cell Assay
chemical_list: D000970:Antineoplastic Agents; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D000077209:Decitabine; D001374:Azacitidine