ESTROGEN INDUCES ID4 SILENCING THROUGH PROMOTER METHYLATION IN ER+ BREAST TUMORS

NASIF DANIELA; REAL, SEBASTIAN; LAURITO S; ROQUE MORENO MARIA; BRANHAM, MARÍA TERESITA

Congreso; REUNION SAIC 2022; 2022

Background: Inhibitor of differentiation protein 4 (ID4) is a dominant negative regulator of the basic helix-loop-helix (bHLH) family of transcription factors. Our group has previously shown that, in breast cancer, ID4 behaves as a tumor suppressor only in estrogen receptor positive (ER+) tumors and that ID4 expression is downregulated through methylation. Taking these observations into consideration, we decided to explore into the study of the molecular mechanisms that lead to the silencing of ID4 through methylation. Given that ID4 is methylated only in ER+ tumors, we hypothesize here that estrogen via estrogen receptor α induces ID4 methylation. Methods: In vitro experiments involved cell culture of MCF7 and T47D ER+ breast cancer cell lines, cells were treated with estradiol, 5-Azacitidine or Tamoxifen. Gene and protein expression were analyzed by RT-qPCR and western blot and methylation by ddMSP. In-silico analyses involved the evaluation of ID4 expression and methylation status on human breast tumors of public datasets according to breast cancer molecular classification and estrogen receptor status. Results: Estradiol treatment induced a reduction in ID4 expression through increased methylation on ID4 promoter (p