FOXM1 expression is significantly associated with chemotherapy resistance and adverse prognosis in non-serous epithelial ovarian cancer patients

Renata A. Tassi, Paola Todeschini, Eric R. Siegel, Stefano Calza, Paolo Cappella, Laura Ardighieri, Moris Cadei, Mattia Bugatti, Chiara Romani, Elisabetta Bandiera, Laura Zanotti, Laura Tassone, Donatella Guarino, Concetta Santonocito, Ettore D. Capoluongo, Luca Beltrame, Eugenio Erba, Sergio Marchini, Maurizio D’Incalci, Carla DonzelliAlessandro D. Santin, Sergio Pecorelli, Enrico Sartori, Eliana Bignotti, Franco Odicino, Antonella Ravaggi

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Epithelial ovarian cancer (EOC) is a spectrum of different diseases, which makes their treatment a challenge. Forkhead box M1 (FOXM1) is an oncogene aberrantly expressed in many solid cancers including serous EOC, but its role in non-serous EOCs remains undefined. We examined FOXM1 expression and its correlation to prognosis across the three major EOC subtypes, and its role in tumorigenesis and chemo-resistance in vitro. Methods: Gene signatures were generated by microarray for 14 clear-cell and 26 endometrioid EOCs, and 15 normal endometrium snap-frozen biopsies. Validation of FOXM1 expression was performed by RT-qPCR and immunohistochemistry in the same samples and additionally in 50 high-grade serous EOCs and in their most adequate normal controls (10 luminal fallopian tube and 20 ovarian surface epithelial brushings). Correlations of FOXM1 expression to clinic-pathological parameters and patients’ prognosis were evaluated by Kaplan-Meier and Cox proportional-hazards analyses. OVCAR-3 and two novel deeply characterized EOC cell lines (EOC-CC1 and OSPC2, with clear-cell and serous subtype, respectively) were employed for in vitro studies. Effects of FOXM1 inhibition by transient siRNA transfection were evaluated on cell-proliferation, cell-cycle, colony formation, invasion, and response to conventional first- and second-line anticancer agents, and to the PARP-inhibitor olaparib. Gene signatures of FOXM1-silenced cell lines were generated by microarray and confirmed by RT-qPCR. Results: A significant FOXM1 mRNA up-regulation was found in EOCs compared to normal controls. FOXM1 protein overexpression significantly correlated to serous histology (p = 0.001) and advanced FIGO stage (p = 0.004). Multivariate analyses confirmed FOXM1 protein overexpression as an independent indicator of worse disease specific survival in non-serous EOCs, and of shorter time to progression in platinum-resistant cases. FOXM1 downregulation in EOC cell lines inhibited cell growth and clonogenicity, and promoted the cytotoxic effects of platinum compounds, doxorubicin hydrochloride and olaparib. Upon FOXM1 knock-down in EOC-CC1 and OSPC2 cells, microarray and RT-qPCR analyses revealed the deregulation of several common and other unique subtype-specific FOXM1 putative targets involved in cell cycle, metastasis, DNA repair and drug response. Conclusions: FOXM1 is up-regulated in all three major EOCs subtypes, and is a prognostic biomarker and a potential combinatorial therapeutic target in platinum resistant disease, irrespective of tumor histology.

Original languageEnglish
Article number63
JournalJournal of Experimental and Clinical Cancer Research
Volume36
Issue number1
DOIs
Publication statusPublished - May 8 2017

Keywords

  • Anticancer drug
  • Cell line
  • Chemoresistance
  • Epithelial ovarian cancer
  • FOXM1
  • Immunohistochemistry
  • Microarray
  • Prognosis
  • Subtype

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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