Loss of the tumor suppressor Snf5 leads to aberrant activation of the Hedgehog-Gli pathway

Aberrant activation of the Hedgehog (Hh) pathway can drive tumorigenesis. To investigate the mechanism by which glioma-associated oncogene family zinc finger-1 (GLI1), a crucial effector of Hh signaling, regulates Hh pathway activation, we searched for GLI1-interacting proteins. We report that the chromatin remodeling protein SNF5 (encoded by SMARCB1, hereafter called SNF5), which is inactivated in human malignant rhabdoid tumors (MRTs), interacts with GLI1. We show that Snf5 localizes to Gli1-regulated promoters and that loss of Snf5 leads to activation of the Hh-Gli pathway. Conversely, re-expression of SNF5 in MRT cells represses GLI1. Consistent with this, we show the presence of a Hh-Gli-activated gene expression profile in primary MRTs and show that GLI1 drives the growth of SNF5-deficient MRT cells in vitro and in vivo. Therefore, our studies reveal that SNF5 is a key mediator of Hh signaling and that aberrant activation of GLI1 is a previously undescribed targetable mechanism contributing to the growth of MRT cells.     

MiR‐520b promotes the progression of non‐small cell lung cancer through activating Hedgehog pathway

Although the non‐small cell lung cancer (NSCLC) is one of the most malignant tumours worldwide, the mechanisms controlling NSCLC tumourigenesis remain unclear. Here, we find that the expression of miR‐520b is up‐regulated in NSCLC samples. Further studies have revealed that miR‐520b promotes the proliferation and metastasis of NSCLC cells. In addition, miR‐520b activates Hedgehog (Hh) pathway. Inhibitor of Hh pathway could relieve the oncogenic effect of miR‐520b upon NSCLC cells. Mechanistically, we demonstrate that miR‐520b directly targets SPOP 3′‐UTR and decreases SPOP expression, culminating in GLI2/3 stabilization and Hh pathway hyperactivation. Collectively, our findings unveil that miR‐520b promotes NSCLC tumourigenesis through SPOP‐GLI2/3 axis and provide miR‐520b as a potential diagnostic biomarker and therapeutic target for NSCLC.     

Hedgehog/GLI-mediated transcriptional inhibitors from Zizyphus cambodiana

The aberrant hedgehog (Hh)/GLI signaling pathway causes the formation and progression of a variety of tumors. By screening tropical plant extracts by using our screening system, Zizyphus cambodiana was found to include Hh/GLI signaling inhibitors. Bioassay-guided fractionation of this plant extract led to the isolation of three active pentacyclic triterpenes, colubrinic acid (1), betulinic acid (2) and alphitolic acid (3), as potent inhibitors. The inhibition of GLI-related protein expression with 1 or 2 was observed in HaCaT cells with exogenous GLI1, or human pancreatic cancer cells (PANC1), which express Hh/GLI components aberrantly. The expressions of GLI-related proteins PTCH and BCL2 were clearly inhibited by 1 or 2. We also examined the cytotoxicity of these active compounds against PANC1, human prostate cancer cells (DU145) and mouse embryo fibroblast cells (C3H10T1/2). The cytotoxicity against cancer cells (PANC1 and DU145) by 1 or 2 would be caused by inhibition of the expression of the anti-apoptosis protein BCL2. These pentacyclic triterpene inhibitors showed an important relationship between Hh/GLI signaling inhibition, the decrease of BCL2, and cytotoxicity against cancer cells.     

Hedgehog signaling and osteoblast gene expression are regulated by purmorphamine in human mesenchymal stem cells

Several biological events are controlled by Hedgehog (Hh) signaling, including osteoblast phenotype development. This study aimed at evaluating the gene expression profile of human mesenchymal stem cells (hMSCs) treated with the Hh agonist, purmorphamine, focusing on Hh signaling and osteoblast differentiation. hMSCs from bone marrow were cultured in non‐osteogenic medium with or without purmorphamine (2 µM) for periods of up to 14 days. Purmorphamine up‐regulated gene expression of the mediators of Hh pathway, SMO, PTCH1, GLI1, and GLI2. The activation of Hh pathway by purmorphamine increased the expression of several genes (e.g., RUNX2 and BMPs) related to osteogenesis. Our results indicated that purmorphamine triggers Hh signaling pathway in hMSCs, inducing an increase in the expression of a set of genes involved in the osteoblast differentiation program. Thus, we conclude that Hh is a crucial pathway in the commitment of undifferentiated cells to the osteoblast lineage. J. Cell. Biochem. 113: 204–208, 2012. © 2011 Wiley Periodicals, Inc.     

The role of GLI2-ABCG2 signaling axis for 5Fu resistance in gastric cancer

Gastric cancer is a leading cause of cancer-related mortality worldwide, and options to treat gastric cancer are limited. Fluorouracil(5Fu)-based chemotherapy is frequently used as a neoadjuvant or an adjuvant agent for gastric cancer therapy. Most patients with advanced gastric cancer eventually succumb to the disease despite the fact that some patients respond initially to chemotherapy. Thus, identifying molecular mechanisms responsible for chemotherapy resistance will help design novel strategies to treat gastric cancer. In this study, we discovered that residual cancer cells following 5Fu treatment have elevated expression of hedgehog(Hg) target genes GLI1 and GLI2, suggestive of Hh signaling activation. Hh signaling, a pathway essential for embryonic development, is an important regulator for putative cancer stem cells/residual cancer cells. We found that high GLI1/GLI2 expression is associated with some features of putative cancer stem cells, such as increased side population. We demonstrated that GLI2 knockdown sensitized gastric cancer cells to 5Fu treatment, decreased ABCG2 expression, and reduced side population. Elevated GLI2 expression is also associated with an increase in tumor sphere size, another marker for putative cancer stem cells. We believe that GLI2 regulates putative cancer stem cells through direct regulation of ABCG2. ABCG2 can rescue the GL12 shRNA effects in 5Fu response, tumor sphere formation and side population changes, suggesting that ABCG2 is an important mediator for GLI2-associated 5Fu resistance. The relevance of our studies to gastric cancer patient care is reflected by our discovery that high GLI1/GLI2/ABCG2 expression is associated with a high incidence of cancer relapse in two cohorts of gastric cancer patients who underwent chemotherapy(containing 5Fu). Taken together,we have identified a molecular mechanism by which gastric cancer cells gain 5Fu resistance.     

CDO,an Hh-Coreceptor,Mediates Lung Cancer Cell Proliferation and Tumorigenicity through Hedgehog Signaling

Hedgehog (Hh) signaling plays essential roles in various developmental processes, and its aberrant regulation results in genetic disorders or malignancies in various tissues. Hyperactivation of Hh signaling is associated with lung cancer development, and there have been extensive efforts to investigate how to control Hh signaling pathway and regulate cancer cell proliferation. In this study we investigated a role of CDO, an Hh co-receptor, in non-small cell lung cancer (NSCLC). Inhibition of Hh signaling by SANT-1 or siCDO in lung cancer cells reduced proliferation and tumorigenicity, along with the decrease in the expression of the Hh components. Histological analysis with NSCLC mouse tissue demonstrated that CDO was expressed in advanced grade of the cancer, and precisely co-localized with GLI1. These data suggest that CDO is required for proliferation and survival of lung cancer cells via Hh signaling.