DZNep is a global histone methylation inhibitor that reactivates developmental genes not silenced by DNA methylation.
DNA methylation, histone modifications, and nucleosomal occupancy collaborate to cause silencing of tumor-related genes in cancer. The development of drugs that target these processes is therefore important for cancer therapy. Inhibitors of DNA methylation and histone deacetylation have been approved by the Food and Drug Administration for treatment of hematologic malignancies. However, drugs that target other mechanisms still need to be developed. Recently, 3-deazaneplanocin A (DZNep) was reported to selectively inhibit trimethylation of lysine 27 on histone H3 (H3K27me3) and lysine 20 on histone H4 (H4K20me3) as well as reactivate silenced genes in cancer cells. This finding opens the door to the pharmacologic inhibition of histone methylation. We therefore wanted to further study the mechanism of action of DZNep in cancer cells. Western blot analysis shows that DZNep globally inhibits histone methylation and is not selective. Two other drugs, sinefungin and adenosine dialdehyde, have similar effects as DZNep on H3K27me3. Intriguingly, chromatin immunoprecipitation of various histone modifications and microarray analysis show that DZNep acts through a different pathway than 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor. These observations give us interesting insight into how chromatin structure affects gene expression. We also determined the kinetics of gene activation to understand if the induced changes were somatically heritable. We found that upon removal of DZNep, gene expression is reduced to its original state. This suggests that there is a homeostatic mechanism that returns the histone modifications to their "ground state" after DZNep treatment. Our data show the strong need for further development of histone methylation inhibitors.
Miranda
Tina Branscombe
TB
Department of Urology, USC Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA.
Cortez
Connie C
CC
Yoo
Christine B
CB
Liang
Gangning
G
Abe
Masanobu
M
Kelly
Theresa K
TK
Marquez
Victor E
VE
Jones
Peter A
PA
D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000077209:Decitabine; D000071221:Enhancer of Zeste Homolog 2 Protein; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D053552:Keratin-7 / Q000235:genetics / Q000378:metabolism; D008745:Methylation / Q000187:drug effects; D015394:Molecular Structure; D020411:Oligonucleotide Array Sequence Analysis; D063151:Polycomb Repressive Complex 2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006657:Histones; C507497:KRT7 protein, human; D053552:Keratin-7; D014157:Transcription Factors; C048460:3-deazaneplanocin; D000077209:Decitabine; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2; D000241:Adenosine; D001374:Azacitidine; C006235:sinefungin