Comparative epigenomics of human and mouse mammary tumors.
Gene silencing by aberrant epigenetic chromatin alteration is a well-recognized event contributing to tumorigenesis. Although genetically engineered tumor-prone mouse models have proven a powerful tool in understanding many aspects of carcinogenesis, to date few studies have focused on epigenetic alterations in mouse tumors. To uncover epigenetically silenced tumor suppressor genes (TSGs) in mouse mammary tumor cells, we conducted initial genome-wide screening by combining the treatment of cultured cells with the DNA demethylating drug 5-aza-2'-deoxycytidine (5-azadC) and the histone deacetylase inhibitor trichostatin A (TSA) with expression microarray. By conducting this initial screen on EMT6 cells and applying protein function and genomic structure criteria to genes identified as upregulated in response to 5-azadC/TSA, we were able to identify two characterized breast cancer TSGs (Timp3 and Rprm) and four putative TSGs (Atp1B2, Dusp2, FoxJ1 and Smpd3) silenced in this line. By testing a panel of 10 mouse mammary tumor lines, we determined that each of these genes is commonly hypermethylated, albeit with varying frequency. Furthermore, by examining a panel of human breast tumor lines and primary tumors we observed that the human orthologs of ATP1B2, FOXJ1 and SMPD3 are aberrantly hypermethylated in the human disease whereas DUSP2 was not hypermethylated in primary breast tumors. Finally, we examined hypermethylation of several genes targeted for epigenetic silencing in human breast tumors in our panel of 10 mouse mammary tumor lines. We observed that the orthologs of Cdh1, RarB, Gstp1, RassF1 genes were hypermethylated, whereas neither Dapk1 nor Wif1 were aberrantly methylated in this panel of mouse tumor lines. From this study, we conclude that there is significant, but not absolute, overlap in the epigenome of human and mouse mammary tumors.
Department of Biochemistry and Molecular Biology, UF-Shands Cancer Center, University of Florida College of Medicine, Gainesville, FL 32610, USA.
Berna
B
Demircan
Lisa M
LM
Dyer
Mallory
M
Gerace
Edward K
EK
Lobenhofer
Keith D
KD
Robertson
Kevin D
KD
Brown
D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D030541:Databases, Genetic; D000077209:Decitabine; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006023:Glycoproteins / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D015674:Mammary Neoplasms, Animal / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D013329:Structure-Activity Relationship; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000378:metabolism
D018797:Cell Cycle Proteins; D006023:Glycoproteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C412566:RPRM protein, human; D019717:Tissue Inhibitor of Metalloproteinase-3; C012589:trichostatin A; D000077209:Decitabine; D015254:DNA Modification Methylases; D006655:Histone Deacetylases; D001374:Azacitidine