title: FOXM1 confers acquired cisplatin resistance in breast cancer cells.
abstract: The transcription factor Forkhead box M1 (FOXM1) is a key regulator of cell proliferation and is overexpressed in many forms of primary cancers, leading to uncontrolled cell division and genomic instability. To address the role of FOXM1 in chemoresistance, we generated a cisplatin-resistant breast cancer cell line (MCF-7-CIS(R)), which had an elevated level of FOXM1 protein and mRNA expression relative to the parental MCF-7 cells. A close correlation was observed between FOXM1 and the expression of its proposed downstream targets that are involved in DNA repair; breast cancer-associated gene 2 (BRCA2) and X-ray cross-complementing group 1 (XRCC1) were expressed at higher levels in the resistant cell lines compared with the sensitive MCF-7 cells. Moreover, cisplatin treatment induced DNA damage repair in MCF-7-CIS(R) and not in MCF-7 cells. Furthermore, the expression of a constitutively active FOXM1 (DeltaN-FOXM1) in MCF-7 cells alone was sufficient to confer cisplatin resistance. Crucially, the impairment of DNA damage repair pathways through the small interfering RNA knockdown inhibition of either FOXM1 or BRCA2/XRCC1 showed that only the silencing of FOXM1 could significantly reduce the rate of proliferation in response to cisplatin treatment in the resistant cells. This suggests that the targeting of FOXM1 is a viable strategy in circumventing acquired cisplatin resistance. Consistently, the FOXM1 inhibitor thiostrepton also showed efficacy in causing cell death and proliferative arrest in the cisplatin-resistant cells through the downregulation of FOXM1 expression. Taken together, we have identified a novel mechanism of acquired cisplatin resistance in breast cancer cells through the induction of FOXM1.
authors.affiliation: Cancer Research-UK Laboratories, Department of Oncology, Medical Research Council Cyclotron Building, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, United Kingdom.
authors.forename: Jimmy M-M
authors.initials: JM
authors.lastname: Kwok
authors.forename: Barrie
authors.initials: B
authors.lastname: Peck
authors.forename: Lara J
authors.initials: LJ
authors.lastname: Monteiro
authors.forename: Helma D C
authors.initials: HD
authors.lastname: Schwenen
authors.forename: Julie
authors.initials: J
authors.lastname: Millour
authors.forename: R Charles
authors.initials: RC
authors.lastname: Coombes
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Myatt
authors.forename: Eric W-F
authors.initials: EW
authors.lastname: Lam
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins; D024682:BRCA2 Protein / Q000502:physiology; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D002478:Cells, Cultured; D002945:Cisplatin / Q000627:therapeutic use*; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D005260:Female; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D050505:Mutant Proteins / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D013883:Thiostrepton / Q000494:pharmacology; D015854:Up-Regulation; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D051017:Apoptosis Regulatory Proteins; C118024:BLID protein, human; D024682:BRCA2 Protein; C551750:BRCA2 protein, human; D004268:DNA-Binding Proteins; C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; D050505:Mutant Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D013883:Thiostrepton; D002945:Cisplatin