Arsenic trioxide inhibits human cancer cell growth and tumor development in mice by blocking Hedgehog/GLI pathway
Elspeth M. Beauchamp, … , Jeffrey A. Toretsky, Aykut Üren
Elspeth M. Beauchamp, … , Jeffrey A. Toretsky, Aykut Üren
Published December 22, 2010
Citation Information: J Clin Invest. 2011;121(1):148-160. https://doi.org/10.1172/JCI42874.
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Research Article

Arsenic trioxide inhibits human cancer cell growth and tumor development in mice by blocking Hedgehog/GLI pathway

Abstract

The Hedgehog (Hh) pathway is activated in some human cancers, including medulloblastoma. The glioma-associated oncogene homolog (GLI) transcription factors are critical mediators of the activated Hh pathway, and their expression may be elevated in some tumors independent of upstream Hh signaling. Thus, therapies targeting GLI transcription factors may benefit a wide spectrum of patients with mutations at different nodal points of the Hh pathway. In this study, we present evidence that arsenic trioxide (ATO) suppresses human cancer cell growth and tumor development in mice by inhibiting GLI1. Mechanistically, ATO directly bound to GLI1 protein, inhibited its transcriptional activity, and decreased expression of endogenous GLI target genes. Consistent with this, ATO inhibited the growth of human cancer cell lines that depended on upregulated GLI expression in vitro and in vivo in a xenograft model of Ewing sarcoma. Furthermore, ATO improved survival of a clinically relevant spontaneous mouse model of medulloblastoma with activated Hh pathway signaling. Our results establish ATO as a Hh pathway inhibitor acting at the level of GLI1 both in vitro and in vivo. These results warrant the clinical investigation of ATO for tumors with activated Hh/GLI signaling, in particular patients who develop resistance to current therapies targeting the Hh pathway upstream of GLI.

Authors

Elspeth M. Beauchamp, Lymor Ringer, Gülay Bulut, Kamal P. Sajwan, Michael D. Hall, Yi-Chien Lee, Daniel Peaceman, Metin Özdemirli, Olga Rodriguez, Tobey J. Macdonald, Chris Albanese, Jeffrey A. Toretsky, Aykut Üren

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Figure 1

ATO inhibits GLI1 protein activity and target gene expression.

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ATO inhibits GLI1 protein activity and target gene expression. (A and B)...
(A and B) HepG2 cells were transfected with GLI luciferase reporter construct (pGL38XGLI) and Notch luciferase reporter construct (HES-1) with or without GLI1 and Notch cDNAs, respectively (A), and COS7 cells were transfected with pGL38XGLI and GLI2 constructs (B). Renilla-TK construct was used as transfection control for signal normalization. 24 hours after transfection, cells were treated with ATO for 24 hours. Mean ± SD relative luciferase activity was calculated relative to Renilla activity. Transfection assays were performed in triplicate. Expression of GLI1 and Notch (A) and GLI2 (B) were detected by Western blot. In A, cell viability was measured at the same dose range and plotted on the same graph. (C) TC-71 cells were treated with vehicle or ATO for 12 hours. qRT-PCR was performed to quantify changes in GLI1 mRNA levels as well as PTCH1 and GAS1. Expression was normalized to GAPDH. Mean ± SD relative expression level was calculated using the comparative Ct method. ***P < 0.0001, 2-tailed Student’s t test. Each condition was performed in triplicate. (D) TC-71 total cell lysates from the experiment in C were subject to SDS-PAGE followed by IB with anti-GLI1, anti-FLI1, and anti-actin antibodies.