Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.37 (DNA methyltransferase)
 4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resistance to the cytotoxic actions of antineoplastic drugs, whether intrinsic or acquired, remains a barrier to the establishment of curative chemotherapy regimens for advanced breast cancer. Over-expression of P-glycoprotein (P-gp), encoded by the MDR1 gene and known to mediate resistance to many antineoplastic drugs, may contribute to poor breast cancer treatment outcome. Nonetheless, the precise molecular mechanisms responsible for high or low level P-gp expression in breast cancer cells have not been established. We assessed the role of DNA hypermethylation near the MDR1 transcriptional regulatory region in MDR1 expression in MCF-7 breast cancer cells, which fail to express MDR1 mRNA, and MCF-7/ADR cells, known to express high MDR1 mRNA levels. When compared to MCF-7/ADR cells, MCF-7 cells manifested markedly diminished MDR1 transcription rates by nuclear run-off assay, but equivalent MDR1 promoter trans-activation activity in transient transfection experiments, indicating that cis factors were most likely responsible for the differences in MDR1 transcription between MCF-7/ADR cells and MCF-7 cells. Bisulfite genomic sequencing analyses revealed substantially less extensive MDR1 promoter methylation in MCF-7/ADR cells than in MCF-7 cells, suggesting that CpG dinucleotide methylation might contribute to the observed MDR1 transcription differences. Chromatin immunoprecipitation analyses indicated an inactive MDR1 chromatin conformation in MCF-7 cells, with a paucity of acetylated histones and the presence of 5-mC-binding proteins MeCP2 and MBD2, and an active MDR1 chromatin conformation in MCF-7/ADR cells, with an abundance of acetylated histones and the presence of the transcriptional trans-activator YB-1. Stable MCF-7 sublines which had been treated with the DNA methyltransferase inhibitor 5-azacytidine, exhibited a reduction in MDR1 promoter methylation and a complex MDR1 chromatin configuration, characterized by the simultaneous presence of transcriptional activators and repressors. In this state, MDR1 expression was markedly sensitive to treatment with the histone deacetylase inhibitor trichostatin A.
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PMID:MDR1 promoter hypermethylation in MCF-7 human breast cancer cells: changes in chromatin structure induced by treatment with 5-Aza-cytidine. 1525 26

Persistent infections with certain high-risk human papillomavirus (HPV) types such as 16 and 18 can result in the development of cervical cancer. Neither of the two prophylactic vaccines against HPV16 and 18 that are in current use have any therapeutic efficacy for prevalent HPV infections. Ablative therapy is widely used for the treatment of HPV cervical dysplasia however disease recurrence is a widely recognized problem. Thus there is a continuing need for therapeutic approaches for the treatment of HPV infections. The HPV16 E6 viral oncoprotein represses surface expression of the cellular adhesion molecule, E-cadherin. Reduced E-cadherin expression on HPV-infected keratinocytes is associated with lowered numbers of antigen-presenting Langerhans cells in the infected epidermis, potentially reducing immune surveillance for HPV. Four chemicals reported to up-regulate E-cadherin were screened for their ability to counteract E6 repression of surface E-cadherin. 5-Aza-2'-deoxycytidine (AzaDC), a DNA methyltransferase inhibitor, and Indole-3-carbinol (I3C), reported to increase E-cadherin through a p21(Waf1/Cip1)-dependent mechanism, had low cytotoxicity and increased or restored E-cadherin expression and adhesive function in HPV16 E6 expressing HCT116 cells. Doxorubicin, also known to induce p21(Waf1/Cip1), increased E-cadherin in E6 expressing cells but had some associated cytotoxicity. Tamoxifen, which can restore adhesive function of surface E-cadherin, was ineffective in counteracting E6 repression of E-cadherin. AzaDC and I3C both show potential to restore antigen-presenting cells to HPV infected skin by antagonizing E6 repression of E-cadherin, thereby counteracting an important immune evasion mechanism of HPV16 and reinstating immune function at the infected site.
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PMID:Screening of drugs to counteract human papillomavirus 16 E6 repression of E-cadherin expression. 2235 17