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 October 1, 2018; First published September 10, 2018
Citation Information: J Clin Invest. 2018;128(10):4682-4696. https://doi.org/10.1172/JCI70712.
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Categories: 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

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Figure 1

AHR controls ODC1 and AZIN1 transcription.

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AHR controls ODC1 and AZIN1 transcription. (A) Predicted transcription f...
(A) Predicted transcription factors binding AZIN1 and ODC1 promoters. (B) Extracts from WI-38 cells expressing empty vector control (Ctrl) or CA-AHR probed by immunoblotting for AZIN1 and ODC1. (C) RNA from cells as in B probed in qRT-PCR with the indicated primers and probes. Data represent the average ± SEM of 3 independent experiments performed in triplicate. (D) Schematic of conserved (black circles) or partially conserved (shaded circle) AHR binding sites in the indicated promoters. Hs, Homo sapiens; Mm, Mus musculus. (E) WI-38 DNA was immunoprecipitated with control (IgG) or AHR-specific antibodies and probed in qRT-PCR with primers for the CYP1a1 promoter (positive control), regions in AZIN1 and ODC1 promoters described in D, or GMPR (negative control). Luciferase activity for the AZIN1 and ODC1 promoter regions described in D with increasing amounts of CA-AHR (F) or BaP (G). The XRE-luc plasmid was used as a control. Data represent the average ± SEM of 2 independent experiments performed in duplicate. (H) Cell extracts of WI-38 cells expressing control shRNA (Ctrl-sh) or 2 independent shRNAs against AHR (sh1 and sh2) probed by immunoblotting with the indicated antibodies. (I) RNA from cells as in H probed in qRT-PCR with the indicated primers and probes. Data represent the average ± SEM of 4 independent experiments performed in triplicate. (J) Polyamine content in cells as in H. Data represent the average ± SEM of 4 independent experiments. (K) Extracts of WI-38 cells treated for 2 hours with DMSO or 20 μM CH223191 probed by immunoblotting for AZIN1 and ODC1. (L) RNA from cells as in K probed in qRT-PCR with the indicated primers and probes. Data represent the average ± SEM of 3 independent experiments performed in triplicate. (M) Polyamine content in WI-38 cells treated with CH223191 for 48 hours. Data represent the average ± SEM of 3 independent experiments. *P < 0.05 and **P < 0.001, by 2-tailed Student’s t test. AZI, AZIN1 ; CYP, CYP1a1; ODC, ODC1; TiP, TiPARP; Spd, spermidine; Put, putrescine; Spm, spermine.