Research Papers:

Differential effects of histone deacetylase inhibitors on cellular drug transporters and their implications for using epigenetic modifiers in combination chemotherapy

Benigno C. Valdez, Yang Li, David Murray, Jonathan E. Brammer, Yan Liu, Chitra Hosing, Yago Nieto, Richard E. Champlin and Borje S. Andersson _

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Oncotarget. 2016; 7:63829-63838. https://doi.org/10.18632/oncotarget.11561

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Benigno C. Valdez1, Yang Li1, David Murray2, Jonathan E. Brammer1, Yan Liu1, Chitra Hosing1, Yago Nieto1, Richard E. Champlin1, Borje S. Andersson1

1Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA

2Department of Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada

Correspondence to:

Benigno C. Valdez, email: [email protected]

Keywords: HDAC inhibitors, drug transporter, combination therapy, lymphoma, pre-transplant regimen

Received: May 05, 2016     Accepted: August 11, 2016     Published: August 24, 2016


HDAC inhibitors, DNA alkylators and nucleoside analogs are effective components of combination chemotherapy. To determine a possible mechanism of their synergism, we analyzed the effects of HDAC inhibitors on the expression of drug transporters which export DNA alkylators. Exposure of PEER lymphoma T-cells to 15 nM romidepsin (Rom) resulted in 40%-50% reduction in mRNA for the drug transporter MRP1 and up to ~500-fold increase in the MDR1 mRNA within 32-48 hrs. MRP1 protein levels concomitantly decreased while MDR1 increased. Other HDAC inhibitors − panobinostat, belinostat and suberoylanilide hydroxamic acid (SAHA) − had similar effects on these transporters. The protein level of MRP1 correlated with cellular resistance to busulfan and chlorambucil, and Rom exposure sensitized cells to these DNA alkylators. The decrease in MRP1 correlated with decreased cellular drug export activity, and increased level of MDR1 correlated with increased export of daunorubicin. A similar decrease in the level of MRP1 protein, and increase in MDR1, were observed when mononuclear cells derived from patients with T-cell malignancies were exposed to Rom. Decreased MRP1 and increased MDR1 expressions were also observed in blood mononuclear cells from lymphoma patients who received SAHA-containing chemotherapy in a clinical trial. This inhibitory effect of HDAC inhibitors on the expression of MRP1 suggests that their synergism with DNA alkylating agents is partly due to decreased efflux of these alkylators. Our results further imply the possibility of antagonistic effects when HDAC inhibitors are combined with anthracyclines and other MDR1 drug ligands in chemotherapy.

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