Genome-Wide Screening Reveals an EMT Molecular Network Mediated by Sonic Hedgehog-Gli1 Signaling in Pancreatic Cancer Cells

Aims

The role of sonic hedgehog (SHH) in epithelial mesenchymal transition (EMT) of pancreatic cancer (PC) is known, however, its mechanism is unclear. Because SHH promotes tumor development predominantly through Gli1, we sought to understand its mechanism by identifying Gli1 targets in pancreatic cancer cells.

Methods

First, we investigated invasion, migration, and EMT in PC cells transfected with lentiviral Gli1 interference vectors or SHH over-expression vectors in vitro and in vivo. Next, we determined the target gene profiles of Gli1 in PC cells using cDNA microarray assays. Finally, the primary regulatory networks downstream of SHH-Gli1 signaling in PC cells were studied through functional analyses of these targets.

Results

Our results indicate there is decreased E-cadherin expression upon increased expression of SHH/Gli1. Migration of PC cells increased significantly in a dose-dependent manner within 24 hours of Gli1 expression (P<0.05). The ratio of liver metastasis and intrasplenic miniature metastasis increased markedly upon activation of SHH-Gli1 signals in nude mice. Using cDNA microarray, we identified 278 upregulated and 59 downregulated genes upon Gli1 expression in AsPC-1 cells. The data indicate that SHH-Gli1 signals promote EMT by mediating a complex signaling network including TGFβ, Ras, Wnt, growth factors, PI3K/AKT, integrins, transmembrane 4 superfamily (TM4SF), and S100A4.

Conclusion

Our results suggest that targeting the molecular connections established between SHH-Gli1 signaling and EMT could provide effective therapies for PC.     

Glycogene expression alterations associated with pancreatic cancer epithelial-mesenchymal transition in complementary model systems

Background

The ability to selectively detect and target cancer cells that have undergone an epithelial-mesenchymal transition (EMT) may lead to improved methods to treat cancers such as pancreatic cancer. The remodeling of cellular glycosylation previously has been associated with cell differentiation and may represent a valuable class of molecular targets for EMT.

Methodology/Principal Findings

As a first step toward investigating the nature of glycosylation alterations in EMT, we characterized the expression of glycan-related genes in three in-vitro model systems that each represented a complementary aspect of pancreatic cancer EMT. These models included: 1) TGFβ-induced EMT, which provided a look at the active transition between states; 2) a panel of 22 pancreatic cancer cell lines, which represented terminal differentiation states of either epithelial-like or mesenchymal-like; and 3) actively-migrating and stationary cells, which provided a look at the mechanism of migration. We analyzed expression data from a list of 587 genes involved in glycosylation (biosynthesis, sugar transport, glycan-binding, etc.) or EMT. Glycogenes were altered at a higher prevalence than all other genes in the first two models (p<0.05 and <0.005, respectively) but not in the migration model. Several functional themes were shared between the induced-EMT model and the cell line panel, including alterations to matrix components and proteoglycans, the sulfation of glycosaminoglycans; mannose receptor family members; initiation of O-glycosylation; and certain forms of sialylation. Protein-level changes were confirmed by Western blot for the mannose receptor MRC2 and the O-glycosylation enzyme GALNT3, and cell-surface sulfation changes were confirmed using Alcian Blue staining.

Conclusions/Significance

Alterations to glycogenes are a major component of cancer EMT and are characterized by changes to matrix components, the sulfation of GAGs, mannose receptors, O-glycosylation, and specific sialylated structures. These results provide leads for targeting aggressive and drug resistant forms of pancreatic cancer cells.     

Nuclear factor-κB-dependent epithelial to mesenchymal transition induced by HIF-1α activation in pancreatic cancer cells under hypoxic conditions

Background

Epithelial to mesenchymal transition (EMT) induced by hypoxia is one of the critical causes of treatment failure in different types of human cancers. NF-κB is closely involved in the progression of EMT. Compared with HIF-1α, the correlation between NF-κB and EMT during hypoxia has been less studied, and although the phenomenon was observed in the past, the molecular mechanisms involved remained unclear.

Methodology/Principal Findings

Here, we report that hypoxia or overexpression of hypoxia-inducible factor-1α (HIF-1α) promotes EMT in pancreatic cancer cells. On molecular or pharmacologic inhibition of NF-κB, hypoxic cells regained expression of E-cadherin, lost expression of N-cadherin, and attenuated their highly invasive and drug-resistant phenotype. Introducing a pcDNA3.0/HIF-1α into pancreatic cancer cells under normoxic conditions heightened NF-κB activity, phenocopying EMT effects produced by hypoxia. Conversely, inhibiting the heightened NF-κB activity in this setting attenuated the EMT phenotype.

Conclusions/Significance

These results suggest that hypoxia or overexpression of HIF-1α induces the EMT that is largely dependent on NF-κB in pancreatic cancer cells.     

Evaluation of epithelial mesenchymal transition in patients with chronic obstructive pulmonary disease

Background

The reticular basement membrane (Rbm) in smokers and especially smokers with COPD is fragmented with "clefts" containing cells staining for the collagenase matrix-metalloproteinase-9 (MMP-9) and fibroblast protein, S100A4. These cells are also present in the basal epithelium. Such changes are likely hallmarks of epithelial mesenchymal transition (EMT). We aimed to confirm the epithelial origin of these Rbm cells, and to exclude potential confounding by infiltrating inflammatory cells.

Methods

Endobronchial biopsy sections from 17 COPD current smokers, with documented Rbm splitting and cellularity were stained for neutrophil elastase (neutrophil marker), CD68 (macrophage/mature fibroblasts), CD4+/CD8+ T lymphocytes, CD19 (B-cells), CD11c (dendritic cells/inflammatory cells), and S100 (Langerhans cells). The number of cells in the Rbm and epithelium staining for these "inflammatory" cell markers were then compared to numbers staining for S100A4, "a documented EMT epitope". Slides were double stained for S100A4 and cytokeratin(s).

Results

In the basal epithelium significantly more cells stained for S100A4 compared to infiltrating macrophages, fibroblasts or immune cells: median, 26 (21.3 - 37.3) versus 0 (0 - 9.6) per mm, p < 0.003. Markedly more S100A4 staining cells were also observed in the Rbm compared to infiltrating macrophages, neutrophils, fibroblasts or immune cells or any sub-type: 58 (37.3 - 92.6) versus 0 (0 - 4.8) cells/mm Rbm, p < 0.003. Cells in the basal epithelium 26 (21.3 - 37.3) per mm) and Rbm (5.9 (2.3 - 13.8) per mm) frequently double stained for both cytokeratin and S100A4.

Conclusions

These data provide additional support for active EMT in COPD airways.     

Pancreatic cancer cells enhance the ability of collagen internalization during epithelial-mesenchymal transition

Background

Extracellular matrix (ECM) remodeling is predominantly mediated by fibroblasts using intracellular and extracellular pathways. Although it is well known that extracellular degradation of the ECM by proteases derived from cancer cells facilitates cellular invasion, the intracellular degradation of ECM components by cancer cells has not been clarified. The aim of this study was to characterize collagen internalization, which is the initial step of the intracellular degradation pathway in pancreatic cancer cells, in light of epithelial–mesenchymal transition (EMT).

Methodology/Principal Findings

We analyzed the function of collagen internalization in two pancreatic cancer cell lines, SUIT-2 and KP-2, and pancreatic stellate cells (PSCs) using Oregon Green 488-gelatin. PSCs had a strong ability for collagen uptake, and the pancreatic cancer cells also internalized collagen although less efficiently. The collagen internalization abilities of SUIT-2 and KP-2 cells were promoted by EMT induced by human recombinant transforming growth factor β1 (P<0.05). Expression of Endo180, a collagen uptake receptor, was high in mesenchymal pancreatic cancer cell lines, as determined by EMT marker expression (P<0.01). Quantitative RT-PCR and western blot analyses showed that Endo180 expression was also increased by EMT induction in SUIT-2 and KP-2 cells. Endo180 knockdown by RNA interference attenuated the collagen uptake (P<0.01) and invasive abilities (P<0.05) of SUIT-2 and KP-2 cells.

Conclusions/Significance

Pancreatic cancer cells are capable of collagen internalization, which is enhanced by EMT. This ECM clearance system may be a novel mechanism for cellular invasion and a potential therapeutic target in pancreatic cancer.     

Insights into Pancreatic Cancer Etiology from Pathway Analysis of Genome-Wide Association Study Data

Background

Pancreatic cancer is the fourth leading cause of cancer death in the U.S. and the etiology of this highly lethal disease has not been well defined. To identify genetic susceptibility factors for pancreatic cancer, we conducted pathway analysis of genome-wide association study (GWAS) data in 3,141 pancreatic cancer patients and 3,367 controls with European ancestry.

Methods

Using the gene set ridge regression in association studies (GRASS) method, we analyzed 197 pathways identified from the Kyoto Encyclopedia of Genes and Genomes database. We used the logistic kernel machine (LKM) test to identify major contributing genes to each pathway. We conducted functional enrichment analysis of the most significant genes (P<0.01) using the Database for Annotation, Visualization, and Integrated Discovery (DAVID).

Results

Two pathways were significantly associated with risk of pancreatic cancer after adjusting for multiple comparisons (P<0.00025) and in replication testing: neuroactive ligand-receptor interaction, (Ps<0.00002), and the olfactory transduction pathway (P = 0.0001). LKM test identified four genes that were significantly associated with risk of pancreatic cancer after Bonferroni correction (P<1×10⁻⁵): ABO, HNF1A, OR13C4, and SHH. Functional enrichment analysis using DAVID consistently found the G protein-coupled receptor signaling pathway (including both neuroactive ligand-receptor interaction and olfactory transduction pathways) to be the most significant pathway for pancreatic cancer risk in this study population.

Conclusion

These novel findings provide new perspectives on genetic susceptibility to and molecular mechanisms of pancreatic cancer.     

Reduced CTGF Expression Promotes Cell Growth,Migration, and Invasion in Nasopharyngeal Carcinoma

Background

The role of CTGF varies in different types of cancer. The purpose of this study is to investigate the involvement of CTGF in tumor progression and prognosis of human nasopharyngeal carcinoma (NPC).

Experimental design

CTGF expression levels were examined in NPC tissues and cells, nasopharynx (NP) tissues, and NP69 cells. The effects and molecular mechanisms of CTGF expression on cell proliferation, migration, invasion, and cell cycle were also explored.

Results

NPC cells exhibited decreased mRNA expression of CTGF compared to immortalized human nasopharyngeal epithelial cell line NP69. Similarly, CTGF was observed to be downregulated in NPC compared to normal tissues at mRNA and protein levels. Furthermore, reduced CTGF was negatively associated with the progression of NPC. Knocking down CTGF expression enhanced the colony formation, cell migration, invasion, and G1/S cell cycle transition. Mechanistic analysis revealed that CTGF suppression activated FAK/PI3K/AKT and its downstream signals regulating the cell cycle, epithelial-mesenchymal transition (EMT) and MMPs. Finally, DNA methylation microarray revealed a lack of hypermethylation at the CTGF promoter, suggesting other mechanisms are associated with suppression of CTGF in NPC.

Conclusion

Our study demonstrates that reduced expression of CTGF promoted cell proliferation, migration, invasion and cell cycle progression through FAK/PI3K/AKT, EMT and MMP pathways in NPC.