Journal Article

Effects of a novel DNA methyltransferase inhibitor zebularine on human breast cancer cells

Davidson, Nancy E, Sobolewski, Michele D, Billam, Madhavi

2010

Overview

Because DNA methyltransferase (DNMT) inhibitors like azacytidine and decitabine are known to be effective in the clinic for diseases like myelodysplastic syndromes that may result in part from transcriptional dysregulation due to epigenetic changes, there is interest in developing novel DNMT inhibitors that would be more effective and less toxic. The effects of one such agent, zebularine, which inhibits DNMT and cytidine deaminase, were assessed in two human breast cancer cell lines, MDA-MB-231 and MCF-7. Zebularine treatment inhibited cell growth in a dose and time dependent manner with an IC-50 of ~100 μM and 150 μM in MDA-MB-231 and MCF-7 cells, respectively, on 96 h exposure. This was associated with increased expression of p21, decreased expression of cyclin-D, and induction of S-phase arrest. At high doses zebularine induced changes in apoptotic proteins in a cell line specific manner manifested by alteration in caspase-3, Bax, Bcl2 and PARP cleavage. Like other DNMT inhibitors, zebularine decreased expression of DNMTs post-transcriptionally as well as expression of other epigenetic regulators like methyl CpG binding proteins and global acetyl H3 and H4 protein levels. Its capacity to reexpress epigenetically silenced genes in human breast cancer cells at low doses was confirmed by its ability to induce expression of estrogen and progesterone receptor mRNA in association with changes suggestive of active chromatin at the ER promoter as evidenced by ChIP. Finally, its effect in combination with other DNMT or HDAC inhibitors like decitabine or vorinostat was explored. The combination of 50 μM zebularine with decitabine or vorinostat significantly inhibited cell proliferation and colony formation in MDA-MB-231 cells compared with either drug alone. These findings suggest that zebularine is an effective DNMT inhibitor and demethylating agent in human breast cancer cell lines and potentiates the effects of other epigenetic therapeutics like decitabine and vorinostat.

• Publisher: Boston : Springer US,Springer US,Springer,Springer Nature B.V
• Subject: Adenocarcinoma - enzymology / Adenocarcinoma - pathology / Analysis / Apoptosis Regulatory Proteins - biosynthesis / Apoptosis Regulatory Proteins - genetics / Azacitidine - analogs & derivatives / Azacitidine - pharmacology / Biological and medical sciences / Breast cancer / Breast Neoplasms - enzymology / Breast Neoplasms - pathology / Cancer / Cancer cells / Cancer research / Cancer therapies / Cell Cycle Proteins - biosynthesis / Cell Cycle Proteins - genetics / Cell Line, Tumor - drug effects / Cell Line, Tumor - enzymology / Chromatin Immunoprecipitation / Cytidine - analogs & derivatives / Cytidine - pharmacology / Cytidine Deaminase - antagonists & inhibitors / DNA / DNA (Cytosine-5-)-Methyltransferases - antagonists & inhibitors / Dose-Response Relationship, Drug / Drug Screening Assays, Antitumor / Drug Synergism / Enzyme Inhibitors - pharmacology / Epigenetics / Estrogen / Female / Gene Expression Regulation, Neoplastic - drug effects / Genetic aspects / Gynecology. Andrology. Obstetrics / Humans / Hydroxamic Acids - pharmacology / Inhibitor drugs / Mammary gland diseases / Medical sciences / Medicine / Medicine & Public Health / Neoplasm Proteins - antagonists & inhibitors / Neoplasm Proteins - biosynthesis / Neoplasm Proteins - genetics / Oncology / Preclinical Study / Progesterone / Protein binding / Receptors, Estrogen - biosynthesis / Receptors, Estrogen - genetics / RNA / S Phase - drug effects / Transferases / Tumor Stem Cell Assay / Tumors