Disulfiram’s Antineoplastic Effects on Ovarian Cancer

Abstract

Objective: Aldehyde dehydrogenase (ALDH) enzymatic activity identifies ovarian cancer stem-like cells. We investigated the antineoplastic activity of the ALDH inhibitor Disulfiram on bulk ovarian cancer cells and CD133 + /ALDH + cancer stem-like cells. Study Design: Ovarian cancer cell lines, human ovarian surface epithelial cells, and mesenchymal stem cells were treated with increasing concentrations of Disulfiram and/or Cisplatin in vitro . Treated cells were assessed for viability or FACS-analyzed for either percentage of ovarian cancer stem-like cells or induction of apoptosis. Disulfiram’s impact on cancer stem-like cells was tested in vitro using tumor sphere formation assays and in vivo using tumor initiation assays with in vitro -treated A2780 cells in NSG mice. Finally, Disulfiram’s in vivo activity was assessed versus CD133 + /ALDH + cell-initiated tumor xenografts. Results: Disulfiram demonstrated antineoplastic activity against multiple ovarian cancer cell lines. While Disulfiram had limited in vitro toxicity against human ovarian surface epithelial cells or mesenchymal stem cells (IC50 of ~15 μM and >30 μM, respectively), its antineoplastic activity against cell lines was comparable to Cisplatin (IC 50 ~1.5 μM). Disulfiram-mediated cell death was due, at least in part, to induction of apoptosis. Disulfiram activity was additive with chemotherapy. Disulfiram demonstrated selective depletion of CD44 + cells but not the CD133 + cancer stem-like cells. Disulfiram had no therapeutic impact on tumor initiation studies or in vivo therapy of whole cell line or stem cell-initiated tumor xenografts. Conclusions: In biologically relevant concentrations, Disulfiram has clear antineoplastic activity against ovarian cancer cells in vitro . Disulfiram selectively depleted CD44 + but not CD133 + ovarian cancer stem-like cells in vitro . However, Disulfiram had no significant activity in vivo . Thus, improved and more selective ALDH inhibitors may be required to target ovarian cancer stem cells.