Journal of Experimental & Clinical Cancer Research (May 2017)

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 Donzelli,
  • Alessandro D. Santin,
  • Sergio Pecorelli,
  • Enrico Sartori,
  • Eliana Bignotti,
  • Franco Odicino,
  • Antonella Ravaggi

DOI
https://doi.org/10.1186/s13046-017-0536-y
Journal volume & issue
Vol. 36, no. 1
pp. 1 – 18

Abstract

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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.

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