title: ATM and p53 regulate FOXM1 expression via E2F in breast cancer epirubicin treatment and resistance.
abstract: In this report, we investigated the role and regulation of forkhead box M1 (FOXM1) in breast cancer and epirubicin resistance. We generated epirubicin-resistant MCF-7 breast carcinoma (MCF-7-EPI(R)) cells and found FOXM1 protein levels to be higher in MCF-7-EPI(R) than in MCF-7 cells and that FOXM1 expression is downregulated by epirubicin in MCF-7 but not in MCF-7-EPI(R) cells. We also established that there is a loss of p53 function in MCF-7-EPI(R) cells and that epirubicin represses FOXM1 expression at transcription and gene promoter levels through activation of p53 and repression of E2F activity in MCF-7 cells. Using p53(-/-) mouse embryo fibroblasts, we showed that p53 is important for epirubicin sensitivity. Moreover, transient promoter transfection assays showed that epirubicin and its cellular effectors p53 and E2F1 modulate FOXM1 transcription through an E2F-binding site located within the proximal promoter region. Chromatin immunoprecipitation analysis also revealed that epirubicin treatment increases pRB (retinoblastoma protein) and decreases E2F1 recruitment to the FOXM1 promoter region containing the E2F site. We also found ataxia-telangiectasia mutated (ATM) protein and mRNA to be overexpressed in the resistant MCF-7-EPI(R) cells compared with MCF-7 cells and that epirubicin could activate ATM to promote E2F activity and FOXM1 expression. Furthermore, inhibition of ATM in U2OS cells with caffeine or depletion of ATM in MCF-7-EPI(R) with short interfering RNAs can resensitize these resistant cells to epirubicin, resulting in downregulation of E2F1 and FOXM1 expression and cell death. In summary, our data show that ATM and p53 coordinately regulate FOXM1 via E2F to modulate epirubicin response and resistance in breast cancer.
authors.affiliation: Division of Cancer, Department of Surgery andCancer, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Julie
authors.initials: J
authors.lastname: Millour
authors.forename: Natalia
authors.initials: N
authors.lastname: de Olano
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Horimoto
authors.forename: Lara J
authors.initials: LJ
authors.lastname: Monteiro
authors.forename: Julia K
authors.initials: JK
authors.lastname: Langer
authors.forename: Rosa
authors.initials: R
authors.lastname: Aligue
authors.forename: Nabil
authors.initials: N
authors.lastname: Hajji
authors.forename: Eric W F
authors.initials: EW
authors.lastname: Lam
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D016923:Cell Death / Q000235:genetics; D045744:Cell Line, Tumor; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015251:Epirubicin / Q000494:pharmacology*; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016160:Retinoblastoma Protein / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016160:Retinoblastoma Protein; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D015251:Epirubicin; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases