title: Low MAD2 expression levels associate with reduced progression-free survival in patients with high-grade serous epithelial ovarian cancer.
abstract: Epithelial ovarian cancer (EOC) has an innate susceptibility to become chemoresistant. Up to 30% of patients do not respond to conventional chemotherapy [paclitaxel (Taxol®) in combination with carboplatin] and, of those who have an initial response, many patients relapse. Therefore, an understanding of the molecular mechanisms that regulate cellular chemotherapeutic responses in EOC cells has the potential to impact significantly on patient outcome. The mitotic arrest deficiency protein 2 (MAD2), is a centrally important mediator of the cellular response to paclitaxel. MAD2 immunohistochemical analysis was performed on 82 high-grade serous EOC samples. A multivariate Cox regression analysis of nuclear MAD2 IHC intensity adjusting for stage, tumour grade and optimum surgical debulking revealed that low MAD2 IHC staining intensity was significantly associated with reduced progression-free survival (PFS) (p = 0.0003), with a hazard ratio of 4.689. The in vitro analyses of five ovarian cancer cell lines demonstrated that cells with low MAD2 expression were less sensitive to paclitaxel. Furthermore, paclitaxel-induced activation of the spindle assembly checkpoint (SAC) and apoptotic cell death was abrogated in cells transfected with MAD2 siRNA. In silico analysis identified a miR-433 binding domain in the MAD2 3' UTR, which was verified in a series of experiments. Firstly, MAD2 protein expression levels were down-regulated in pre-miR-433 transfected A2780 cells. Secondly, pre-miR-433 suppressed the activity of a reporter construct containing the 3'-UTR of MAD2. Thirdly, blocking miR-433 binding to the MAD2 3' UTR protected MAD2 from miR-433 induced protein down-regulation. Importantly, reduced MAD2 protein expression in pre-miR-433-transfected A2780 cells rendered these cells less sensitive to paclitaxel. In conclusion, loss of MAD2 protein expression results in increased resistance to paclitaxel in EOC cells. Measuring MAD2 IHC staining intensity may predict paclitaxel responses in women presenting with high-grade serous EOC.
authors: UCD School of Medicine and Medical Science, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland. fiona.furlong@ucd.ie
authors: Fiona
authors: F
authors: Furlong
authors: Patricia
authors: P
authors: Fitzpatrick
authors: Sharon
authors: S
authors: O'Toole
authors: Sine
authors: S
authors: Phelan
authors: Barbara
authors: B
authors: McGrogan
authors: Aoife
authors: A
authors: Maguire
authors: Anthony
authors: A
authors: O'Grady
authors: Michael
authors: M
authors: Gallagher
authors: Maria
authors: M
authors: Prencipe
authors: Aloysius
authors: A
authors: McGoldrick
authors: Paul
authors: P
authors: McGettigan
authors: Donal
authors: D
authors: Brennan
authors: Orla
authors: O
authors: Sheils
authors: Cara
authors: C
authors: Martin
authors: Elaine
authors: E
authors: W Kay
authors: John
authors: J
authors: O'Leary
authors: Amanda
authors: A
authors: McCann
mesh_terms: D020413:3' Untranslated Regions; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016190:Carboplatin / Q000008:administration & dosage; D000077216:Carcinoma, Ovarian Epithelial; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D017024:Chemotherapy, Adjuvant; D018572:Disease-Free Survival; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D064246:Mad2 Proteins; D035683:MicroRNAs / Q000378:metabolism; D015999:Multivariate Analysis; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D018297:Neoplasms, Cystic, Mucinous, and Serous / Q000235:genetics / Q000378:metabolism* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D009375:Neoplasms, Glandular and Epithelial / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D017239:Paclitaxel / Q000008:administration & dosage; D016612:Paraffin Embedding; D016016:Proportional Hazards Models; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014162:Transfection; D016896:Treatment Outcome
chemical_list: D020413:3' Untranslated Regions; D014408:Biomarkers, Tumor; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; C577697:MAD2L1 protein, human; C548883:MIRN433 microRNA, human; D064246:Mad2 Proteins; D035683:MicroRNAs; D012097:Repressor Proteins; D016190:Carboplatin; D017239:Paclitaxel