High-density array analysis of DNA methylation in Tamoxifen-resistant breast cancer cell lines.
Roughly two-thirds of all breast cancers are ERα-positive and can be treated with the antiestrogen, Tamoxifen, however resistance occurs in 33% of women who take the drug for more than 5 y. Aberrant DNA methylation, an epigenetic mechanism that alters gene expression in cancer, is thought to play a role in this resistance. To develop an understanding of Tamoxifen-resistance and identify novel pathways and targets of aberrant methylation, DNA from MCF-7 breast cancer cells and Tamoxifen-resistant derivatives, TMX2-11 and TMX2-28, were analyzed using the Illumina HumanMethylation450 BeadChip. Normalizing against MCF-7 values, ERα-positive TMX2-11 had 4000 hypermethylated sites and ERα-negative TMX2-28 had over 33 000. Analysis of CpG sites altered in both TMX2-11 and TMX2-28 revealed that the Tamoxifen-resistant cell lines share 3000 hypermethylated and 200 hypomethylated CpGs. ZNF350 and MAGED1, two genes hypermethylated in both cell lines, were examined in greater detail. Treatment with 5-aza-2ꞌdeoxycitidine caused a significant reduction in promoter methylation of both ZNF350 and MAGED1 and a corresponding increase in expression in TMX2-28. A similar relationship between methylation and expression was not detected in TMX2-11. Our findings are indicative of the variable responses to methylation-targeted breast cancer therapy and highlight the need for biomarkers that accurately predict treatment outcome.
Molecular & Cellular Biology Graduate Program; Department of Veterinary & Animal Sciences; University of Massachusetts; Amherst, MA USA.
Kristin E
KE
Williams
Department of Sociology; University of South Carolina; Columbia, SC USA.
Douglas L
DL
Anderton
Center for Cancer Research; National Institutes of Health; Bethesda, MD USA.
Maxwell P
MP
Lee
Wadsworth Center; Albany, NY USA.
Brian T
BT
Pentecost
Molecular & Cellular Biology Graduate Program; Department of Veterinary & Animal Sciences; University of Massachusetts; Amherst, MA USA.
Kathleen F
KF
Arcaro
D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001374:Azacitidine / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D019008:Drug Resistance, Neoplasm; D004965:Estrogen Antagonists / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D006801:Humans; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*
D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic; D018931:Antineoplastic Agents, Hormonal; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; C120897:MAGED1 protein, human; D009363:Neoplasm Proteins; D012097:Repressor Proteins; C422407:ZNF350 protein, human; D013629:Tamoxifen; D001374:Azacitidine
Breast Cancer; Estrogen Receptor; HumanMethylation450 BeadChip; MAGED1; Tamoxifen Resistance; ZNF350; methylation