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