Drug Repurposing of the Anthelmintic Niclosamide to Treat Multidrug-Resistant Leukemia

Abstract

Multidrug resistance, a major problem that leads to failure of anticancer chemotherapy, requires the development of new drugs. Repurposing of established drugs is a promising approach for overcoming this problem. An example of such drugs is niclosamide, a known anthelmintic that is now known to be cytotoxic and cytostatic against cancer cells. In this study, niclosamide showed varying activity against different cancer cell lines. It revealed better activity against hematological cancer cell lines CCRF-CEM, CEM/ADR5000, and RPMI-8226 compared to the solid tumor cell lines MDA-MB-231, A549, and HT-29. The multidrug resistant CEM/ADR5000 cells were similar sensitive as their sensitive counterpart CCRF-CEM (resistance ration: 1.24). Furthermore, niclosamide caused elevations in reactive oxygen species and glutathione (GSH) levels in leukemia cells. GSH synthetase (GS) was predicted as a target of niclosamide. Molecular docking showed that niclosamide probably binds to the ATP-binding site of GS with a binding energy of -9.40 kcal/mol. Using microscale thermophoresis, the binding affinity between niclosamide and recombinant human GS was measured (binding constant: 5.64 μM). COMPARE analyses of the NCI microarray database for 60 cell lines showed that several genes, including those involved in lipid metabolism, correlated with cellular responsiveness to niclosamide. Hierarchical cluster analysis showed five major branches with significant differences between sensitive and resistant cell lines (p = 8.66 × 10⁵). Niclosamide significantly decreased nuclear factor of activated T-cells (NFAT) activity as predicted by promoter binding motif analysis. In conclusion, niclosamide was more active against hematological malignancies compared to solid tumors. The drug was particularly active against the multidrug-resistant CEM/ADR5000 leukemia cells. Inhibition of GSH synthesis and NFAT signaling were identified as relevant mechanisms for the anticancer activity of niclosamide. Gene expression profiling predicted the sensitivity or resistance of cancer cells to niclosamide.

Keywords: chemotherapy; drug resistance; oxidative stress; pharmacogenomics; transcription factors.

FIGURE 1

Dose–response curves from the cytotoxicity assays of (A) hematological cancer cell lines (CCRF-CEM, CEM/ADR5000, and RPMI-8226) and (B) solid tumor cell lines (HT-29, MDA-MB-231, and A549).

FIGURE 2

Effect of 24 h treatment with niclosamide (1.5 μM) on ROS levels in CCRF-CEM and CEM/ADR5000 cells. H₂O₂ (50 μM) was used as a positive control (^∗p < 0.05, ^∗∗p < 0.01, compared to DMSO-treated control cells).

FIGURE 3

Effect of niclosamide on glutathione levels in CCRF-CEM and CEM/ADR5000 cells. (A) Flow cytometric analysis of glutathione levels after treatment with niclosamide (12 μM) for 24 h. (B) Statistical quantification of glutathione levels after treatment with different concentrations of niclosamide (^∗p < 0.05, ^∗∗p < 0.01, compared to DMSO-treated control cells).

FIGURE 4

Binding of niclosamide at the ATP binding domain of glutathione synthetase (GS). Hydrogen bond forming amino acids are shown in red.

FIGURE 5

Characterization of binding affinity of niclosamide labeled GS using microscale thermophoresis.

FIGURE 6

Dendrogram of hierarchical cluster analysis (Ward’s method) obtained from microarray-based mRNA expression profiles of genes obtained from the NCI database correlating with niclosamide.

FIGURE 7

Effect of 24 h treatment with various concentrations of niclosamide on NFAT signaling activity. Results shown are the mean values ± SD of three independent experiments (^∗p < 0.01, compared to DMSO-treated control cells).