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


CONCLUSIONS
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.
Morita
Shinji
S
Department of Surgical Oncology, Graduate School of Medicine and Dentistry, Tokyo Medical and Dental University, Tokyo, Japan. shmorita@gmail.com
Iida
Satoru
S
Kato
Keiji
K
Takagi
Yoko
Y
Uetake
Hiroyuki
H
Sugihara
Kenichi
K
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000235:genetics; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects; D064550:Death-Associated Protein Kinases; D000077209:Decitabine; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004357:Drug Synergism; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025803:Tumor Suppressor Protein p14ARF / Q000096:biosynthesis / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
D051017:Apoptosis Regulatory Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D025803:Tumor Suppressor Protein p14ARF; D000077209:Decitabine; D064550:Death-Associated Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D001374:Azacitidine; D005472:Fluorouracil