P-glycoprotein antagonists confer synergistic sensitivity to short-chain ceramide in human multidrug-resistant cancer cells

Exp Cell Res. 2011 Jul 15;317(12):1736-45. doi: 10.1016/j.yexcr.2011.03.004. Epub 2011 Mar 21.

Abstract

P-glycoprotein (P-gp) antagonists inhibit ceramide metabolism at the juncture of glycosylation. The purpose of this study was to test whether targeting P-gp would be a viable alternative to targeting glucosylceramide synthase (GCS) for enhancing ceramide cytotoxicity. A2780 wild-type, and multidrug-resistant 2780AD and NCI/ADR-RES human ovarian cancer cell lines and the cell-permeable ceramide analog, C6-ceramide (C6-cer), were employed. Compared to P-gp-poor A2780 cells, P-gp-rich 2780AD cells converted 3.7-fold more C6-cer to nontoxic C6-glucosylceramide (C6-GC), whereas cell-free GCS activities were equal. 2780AD cells displayed resistance to C6-cer (10 μM) that was reversed by inclusion of the P-gp antagonist tamoxifen (5 μM) but not by inclusion of a GCS inhibitor. Co-administration of C6-cer and P-gp antagonists was also effective in NCI/ADR-RES cells. For example, C6-cer, VX-710 (Biricodar), and cyclosporin A (cyc A) exposure resulted in viabilities of ~90% of control; however, C6-cer/VX-710 and C6-cer/cyc A additions were synergistic and resulted in viabilities of 22% and 17%, respectively. Further, whereas C6-ceramide and cyc A imparted 1.5- and 0-fold increases in caspase 3/7 activity, the combination produced a 3.5-fold increase. Although the upstream elements of cell death have not been elucidated, the novel C6-ceramide/P-gp antagonist combination merits further study and assessment of clinical translational potential.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / antagonists & inhibitors*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Antineoplastic Agents, Hormonal / pharmacology
  • Antineoplastic Combined Chemotherapy Protocols
  • Blotting, Western
  • Ceramides / pharmacology*
  • Drug Resistance, Multiple / drug effects*
  • Drug Resistance, Neoplasm / drug effects*
  • Drug Synergism
  • Female
  • Glucosyltransferases / antagonists & inhibitors
  • Glucosyltransferases / metabolism
  • Humans
  • Ovarian Neoplasms / drug therapy*
  • Ovarian Neoplasms / metabolism
  • Ovarian Neoplasms / pathology
  • Tamoxifen / pharmacology*
  • Tumor Cells, Cultured

Substances

  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents, Hormonal
  • Ceramides
  • N-caproylsphingosine
  • Tamoxifen
  • Glucosyltransferases
  • ceramide glucosyltransferase