Inhibition of the aryl hydrocarbon receptor/polyamine biosynthesis axis suppresses multiple myeloma
Anna Bianchi-Smiraglia, … , Dominic J. Smiraglia, Mikhail A. Nikiforov
Anna Bianchi-Smiraglia, … , Dominic J. Smiraglia, Mikhail A. Nikiforov
Published September 10, 2018
Citation Information: J Clin Invest. 2018;128(10):4682-4696. https://doi.org/10.1172/JCI70712.
View: Text | PDF
Research Article Cell biology Oncology

Inhibition of the aryl hydrocarbon receptor/polyamine biosynthesis axis suppresses multiple myeloma

Abstract

Polyamine inhibition for cancer therapy is, conceptually, an attractive approach but has yet to meet success in the clinical setting. The aryl hydrocarbon receptor (AHR) is the central transcriptional regulator of the xenobiotic response. Our study revealed that AHR also positively regulates intracellular polyamine production via direct transcriptional activation of 2 genes, ODC1 and AZIN1, which are involved in polyamine biosynthesis and control, respectively. In patients with multiple myeloma (MM), AHR levels were inversely correlated with survival, suggesting that AHR inhibition may be beneficial for the treatment of this disease. We identified clofazimine (CLF), an FDA-approved anti-leprosy drug, as a potent AHR antagonist and a suppressor of polyamine biosynthesis. Experiments in a transgenic model of MM (Vk*Myc mice) and in immunocompromised mice bearing MM cell xenografts revealed high efficacy of CLF comparable to that of bortezomib, a first-in-class proteasome inhibitor used for the treatment of MM. This study identifies a previously unrecognized regulatory axis between AHR and polyamine metabolism and reveals CLF as an inhibitor of AHR and a potentially clinically relevant anti-MM agent.

Authors

Anna Bianchi-Smiraglia, Archis Bagati, Emily E. Fink, Hayley C. Affronti, Brittany C. Lipchick, Sudha Moparthy, Mark D. Long, Spencer R. Rosario, Shivana M. Lightman, Kalyana Moparthy, David W. Wolff, Dong Hyun Yun, Zhannan Han, Anthony Polechetti, Matthew V. Roll, Ilya I. Gitlin, Katerina I. Leonova, Aryn M. Rowsam, Eugene S. Kandel, Andrei V. Gudkov, P. Leif Bergsagel, Kelvin P. Lee, Dominic J. Smiraglia, Mikhail A. Nikiforov

×

Figure 2

CLF is an AHR antagonist.

Options: View larger image (or click on image) Download as PowerPoint
CLF is an AHR antagonist. (A) Extracts of WI38 cells treated for 2 hours...
(A) Extracts of WI38 cells treated for 2 hours with increasing concentrations of CLF, Har, or FF probed in the immunoblot for AZIN1 and ODC1. (B) Cytoplasmic and nuclear fractions of WI38 cells treated for 2 hours with DMSO, 4 μM CLF, or 20 μM CH223191 resolved in the immunoblot and probed for AHR. Tubulin and TBP were used as positive controls. Quantification of band intensity was performed with ImageJ (NIH). (C) WI38 cells treated as in B and immunostained for AHR (red), DNA (Hoechst-33342, blue), and actin (phalloidin, green). Images are representative of 2 independent experiments. Scale bars: 20 μm. (D) Luciferase activity assay of HEK293FT cells transduced with XRE-luc, with increasing concentrations of BaP and DMSO, 4 μM CLF, or 20 μM CH223191. Data represent the average ± SEM of 2 independent experiments performed in duplicate. (E) Cytosolic fractions of Hepa 1c1c7 cells preincubated with vehicle or 16 nM TCDD and increasing concentrations of CLF or CH223191, and then incubated with XRE-containing biotinylated oligonucleotides and resolved on native gels. Protein-DNA complexes were visualized with a chemiluminescence system. (F) RNA from WI-38 cells treated for 2 hours with DMSO or 4 μM CLF probed in qRT-PCR with the indicated primers and probes. Data represent the average ± SEM of 3 independent experiments performed in triplicate. (G) Polyamine content in WI38 cells treated with 4 μM CLF for 48 hours. Data represent the average ± SEM of 5 independent experiments. *P < 0.05 and **P < 0.001, by 2-tailed Student’s t test. (H) Proliferation of WI38 cells expressing empty vector (Ctrl) or CA-AHR, with increasing concentrations of CLF over time. Control cells were supplemented with 10 μM spermidine and 1 mM aminoguanidine. IC50 values were determined using GraphPad Prism. Data represent the average of 2 experiments performed in quadruplicate. **P < 0.001, by extra sum-of-squares F test using GraphPad Prism.