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Morad SAF, Davis TS, MacDougall MR, Tan SF, Feith DJ, Desai DH, Amin SG, Kester M, Loughran TP, Cabot MC. Role of P-glycoprotein inhibitors in ceramide-based therapeutics for treatment of cancer. Biochem Pharmacol 2017; 130:21-33. [PMID: 28189725 DOI: 10.1016/j.bcp.2017.02.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 02/01/2017] [Indexed: 10/20/2022]
Abstract
The anticancer properties of ceramide, a sphingolipid with potent tumor-suppressor properties, can be dampened via glycosylation, notably in multidrug resistance wherein ceramide glycosylation is characteristically elevated. Earlier works using the ceramide analog, C6-ceramide, demonstrated that the antiestrogen tamoxifen, a first generation P-glycoprotein (P-gp) inhibitor, blocked C6-ceramide glycosylation and magnified apoptotic responses. The present investigation was undertaken with the goal of discovering non-anti-estrogenic alternatives to tamoxifen that could be employed as adjuvants for improving the efficacy of ceramide-centric therapeutics in treatment of cancer. Herein we demonstrate that the tamoxifen metabolites, desmethyltamoxifen and didesmethyltamoxifen, and specific, high-affinity P-gp inhibitors, tariquidar and zosuquidar, synergistically enhanced C6-ceramide cytotoxicity in multidrug resistant HL-60/VCR acute myelogenous leukemia (AML) cells, whereas the selective estrogen receptor antagonist, fulvestrant, was ineffective. Active C6-ceramide-adjuvant combinations elicited mitochondrial ROS production and cytochrome c release, and induced apoptosis. Cytotoxicity was mitigated by introduction of antioxidant. Effective adjuvants markedly inhibited C6-ceramide glycosylation as well as conversion to sphingomyelin. Active regimens were also effective in KG-1a cells, a leukemia stem cell-like line, and in LoVo human colorectal cancer cells, a solid tumor model. In summary, our work details discovery of the link between P-gp inhibitors and the regulation and potentiation of ceramide metabolism in a pro-apoptotic direction in cancer cells. Given the active properties of these adjuvants in synergizing with C6-ceramide, independent of drug resistance status, stemness, or cancer type, our results suggest that the C6-ceramide-containing regimens could provide alternative, promising therapeutic direction, in addition to finding novel, off-label applications for P-gp inhibitors.
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Affiliation(s)
- Samy A F Morad
- Department of Biochemistry and Molecular Biology, East Carolina University, Brody School of Medicine, East Carolina Diabetes and Obesity Institute, Greenville, NC, United States; Department of Pharmacology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt
| | - Traci S Davis
- Department of Biochemistry and Molecular Biology, East Carolina University, Brody School of Medicine, East Carolina Diabetes and Obesity Institute, Greenville, NC, United States
| | - Matthew R MacDougall
- Department of Biochemistry and Molecular Biology, East Carolina University, Brody School of Medicine, East Carolina Diabetes and Obesity Institute, Greenville, NC, United States
| | - Su-Fern Tan
- Department of Medicine, Hematology/Oncology, University of Virginia, Charlottesville, VA, United States
| | - David J Feith
- Department of Medicine, Hematology/Oncology, University of Virginia, Charlottesville, VA, United States; University of Virginia Cancer Center, University of Virginia, Charlottesville, VA, United States
| | - Dhimant H Desai
- Penn State University College of Medicine, Department of Pharmacology, University Drive, Hershey, PA, United States
| | - Shantu G Amin
- Penn State University College of Medicine, Department of Pharmacology, University Drive, Hershey, PA, United States
| | - Mark Kester
- University of Virginia Cancer Center, University of Virginia, Charlottesville, VA, United States
| | - Thomas P Loughran
- Department of Medicine, Hematology/Oncology, University of Virginia, Charlottesville, VA, United States; University of Virginia Cancer Center, University of Virginia, Charlottesville, VA, United States
| | - Myles C Cabot
- Department of Biochemistry and Molecular Biology, East Carolina University, Brody School of Medicine, East Carolina Diabetes and Obesity Institute, Greenville, NC, United States.
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