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.
Subject(s)
Antineoplastic Agents/pharmacology , Arsenicals/pharmacology , Hedgehog Proteins/antagonists & inhibitors , Medulloblastoma/drug therapy , Oncogene Proteins/antagonists & inhibitors , Oxides/pharmacology , Sarcoma, Ewing/drug therapy , Trans-Activators/antagonists & inhibitors , Animals , Arsenic Trioxide , Base Sequence , Cell Line, Tumor , DNA Primers/genetics , Gene Expression/drug effects , Hep G2 Cells , Humans , Medulloblastoma/metabolism , Medulloblastoma/pathology , Mice , Mice, SCID , Mice, Transgenic , Neoplasm Transplantation , Oncogene Proteins/genetics , Oncogene Proteins/metabolism , Receptors, G-Protein-Coupled/antagonists & inhibitors , Receptors, G-Protein-Coupled/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Sarcoma, Ewing/metabolism , Sarcoma, Ewing/pathology , Signal Transduction/drug effects , Smoothened Receptor , Trans-Activators/genetics , Trans-Activators/metabolism , Transplantation, Heterologous , Zinc Finger Protein GLI1ABSTRACT
Diet and obesity, and their associated metabolic alterations, are some of the fastest-growing causes of disease and death in America. Findings from epidemiological studies correlating obesity, the sources of dietary fat and prostate cancer (PCa) are conflicting. We have previously shown that 15% of PB-ErbB-2 x pten(+/-) mice developed PCa and exhibited increased phosphorylated 4E-BP1, but not the key PI3-kinase intermediary phospho-protein, mTOR, when maintained on unrefined mouse chow. We report herein that 100% of animals fed refined, westernized AIN-93-based diets containing corn oil developed PCa by 12 months of age. Increases in visceral fat and mTO R activation in the tumors were also observed. Furthermore, nuclear cyclin E levels were significantly induced by the AIN-93-corn oil-based diets versus chow. Replacing 50% of the corn oil with menhaden oil, with 21% of its triglycerides being n-3 PUFA's, had no effect on tumorigenesis, fat deposition, cyclin E or mTOR. Phosphorylated BAD levels were similar in the tumors of mice in all three diets. Our data demonstrated that in the context of our preclinical model, components of crude chow, but not dietary n-3 PUFAs, protect against PCa progression. In addition, these data establish phosphorylated mTOR, nuclear cyclin E and visceral fat deposits as possible biomarkers of increased dietary risk for PCa.
