Project description:Our goal was to assess gene expression changes that occur when Lymphoid Enhancer Factor-1 (LEF-1) promotes epithelial-mesenchymal transition (EMT), the primary mechanism of tumor metastasis. To observe this phenomenon without interference from other signaling pathways, we selected DLD1 colon carcinoma cells (ATCC) which contain a mutation in APC. APC is a necessary component of a ubiquitin protein complex (including GSK-3beta, Axin, etc.) that is responsible for degrading cytoplasmic beta-catenin. Therefore, sufficient levels of LEF-1 can be easily activated by forming complexes with the abundant beta-catenin located in the cytoplasm of DLD1 cells. These complexes can then promote transcription of genes that stimulate EMT. We treated DLD1 cells with an adenoviral LEF-1 expression construct, which induced EMT within 48 hours. RNA was then extracted from these cells along with untreated DLD1 cells, then subjected to microarray analysis. From this analysis, we acquired several gene expression profiles by which epithelial colon carcinoma cells transform to an invasive, mesenchymal phenotype to initiate metastasis. Keywords: epithelial-mesenchymal transition, tumor metastasis, cancer progression, epithelial cell plasticity
Project description:Our goal was to assess gene expression changes that occur when Lymphoid Enhancer Factor-1 (LEF-1) promotes epithelial-mesenchymal transition (EMT), the primary mechanism of tumor metastasis. To observe this phenomenon without interference from other signaling pathways, we selected DLD1 colon carcinoma cells (ATCC) which contain a mutation in APC. APC is a necessary component of a ubiquitin protein complex (including GSK-3beta, Axin, etc.) that is responsible for degrading cytoplasmic beta-catenin. Therefore, sufficient levels of LEF-1 can be easily activated by forming complexes with the abundant beta-catenin located in the cytoplasm of DLD1 cells. These complexes can then promote transcription of genes that stimulate EMT. We treated DLD1 cells with an adenoviral LEF-1 expression construct, which induced EMT within 48 hours. RNA was then extracted from these cells along with untreated DLD1 cells, then subjected to microarray analysis. From this analysis, we acquired several gene expression profiles by which epithelial colon carcinoma cells transform to an invasive, mesenchymal phenotype to initiate metastasis. Experiment Overall Design: DLD1 cells were treated with an adenoviral LEF-1 expression construct as described by Kim et al. (2002). Total RNA was extracted from both untreated and treated DLD1 cells using the RNeasy mini extraction kit (Qaigen). RNA amplification, biotin labeling, microarray hybridization, and fluidics were performed following the eukaryotic sample and array processing protocol (Affymetrix). Chips were scanned using an Affymetrix Gene Array Scanner (Hewlett-Packard). Raw data was compiled using Microarray Suite 5.0 software (Affymetrix).
Project description:To validate the suitability of two commonly used colorectal cancer cell lines, DLD1 and SW480, as model systems to study colorectal carcinogenesis, we treated these cell lines with beta-catenin siRNA and identified beta-catenin target genes using DNA microarrays. The list of identified target genes was compared to previously published beta-catenin target genes found in the PubMed and the GEO databases. Based on the large number of beta-catenin target genes found to be similarly regulated in DLD1, SW480 and LS174T as well as the large overlap with confirmed β-catenin target genes, we conclude that DLD1 and SW480 colon carcinoma cell lines are suitable model systems to study beta-catenin regulated genes and signaling pathways 12 arrays (2 cell lines, 2 treatments, 3 biological replicates)
Project description:To validate the suitability of two commonly used colorectal cancer cell lines, DLD1 and SW480, as model systems to study colorectal carcinogenesis, we treated these cell lines with β-catenin siRNA and identified β-catenin target genes using DNA microarrays. The list of identified target genes was compared to previously published β-catenin target genes found in the PubMed and the GEO databases. Based on the large number of β-catenin target genes found to be similarly regulated in DLD1, SW480 and LS174T as well as the large overlap with confirmed β-catenin target genes, we conclude that DLD1 and SW480 colon carcinoma cell lines are suitable model systems to study β-catenin regulated genes and signaling pathways
Project description:Deregulation of canonical Wnt/beta-catenin pathway is one of the earliest events in the pathogenesis of colon cancer. Mutations in APC or CTNNB1 (beta-catenin gene) are highly frequent in colon cancer and cause aberrant stabilization of b-catenin, which activates the transcription of Wnt target genes by binding to chromatin via the TCF/LEF transcription factors. Here we report an integrative analysis of genome-wide chromatin occupancy of b-catenin by chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) and gene expression profiling by microarray analysis upon RNAi-mediated knockdown of beta-catenin in colon cancer cells (GSE53656). Immunoprecipitated samples from human colon cancer SW480 cells with antibodies against beta-catenin and control IgG respectively were used for ChIP-seq experiments.
Project description:We established a model system in human DLD1 colon cancer cells to study the transcriptional crosstalk between FOXO3A and beta-Catenin. Thereby, translocation to the nucleus of a AKT-insensitive mutant (T32A, S253A, S315A) of human FOXO3A fused to the ligand binding domain of human estrogen receptor can be induced by exposure to 4-hydroxy-tamoxifen. Furthermore, expression of a stable mutant (S33Y) of human beta-catenin is doxycycline inducible. Addition of those drugs separately or in combination allows identification of common or excusive target gene sets.
Project description:Wnt/β-catenin signaling is a highly conserved molecular pathway that plays a crucial role in stem/progenitor systems and cancer. β-catenin, the main Wnt pathway effector, has two pools within a cell: one for cell-cell adhesion at the membrane and the other for transcriptional functions in the nucleus. However, the mechanism by which β-catenin mediates both roles remain unclear. The tightly controlled, well characterized system of nephrogenesis is an ideal model to decouple the roles of β-catenin at the membrane and in the nucleus. In kidney development, a delicate balance of nephron progenitor cell self-renewal and differentiation is required for the mesenchymal to epithelial transition (MET) in nephrogenesis and is driven by Wnt/β-catenin signaling. Given an ability to isolate and manipulate large numbers of NPCs in tissue culture, we can dissect the dual nature of β-catenin as a transcriptional activator and component of a cell membrane complex in adhesion. We pioneered a method using CRISPR/Cas9 gene editing to rapidly remove β-catenin, Tcf/Lef factors and simultaneous cadherin genes in primary NPCs. We have characterized the effects of modulating β-catenin and integrated RNA-seq results from β-catenin’s removal with mouse ChIP-seq and mouse single cell RNA -seq data. Functional analysis of β-catenin removal provides strong evidence for β-catenin regulation of NPC proliferation, independent of a direct Lef/Tcf associated transcriptional program. Together these data suggest β-catenin mediates aggregation, the first step in MET, through β-catenin mediated cell adhesion complexes while simultaneous transcriptional activation within these structures initiates the nephrogenic program. The studies provide new insight into the direct transcriptional role of Lef/Tcf/β-catenin complexes associated with the initiation of a nephron forming program. Overall, this study enhances an understanding of the molecular mechanisms underlying kidney development and the dual nature of β-catenin stem/progenitor systems at large.
Project description:Inhibition of canonical Wnt/β-catenin signaling is involved in leflunomide (LEF)-mediated cytotoxic effects on renal carcinoma cells
Project description:Deregulation of canonical Wnt/beta-catenin pathway is one of the earliest events in the pathogenesis of colon cancer. Mutations in APC or CTNNB1 (beta-catenin gene) are highly frequent in colon cancer and cause aberrant stabilization of b-catenin, which activates the transcription of Wnt target genes by binding to chromatin via the TCF/LEF transcription factors. Here we report an integrative analysis of genome-wide chromatin occupancy of b-catenin by chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) and gene expression profiling by microarray analysis upon RNAi-mediated knockdown of beta-catenin in colon cancer cells (GSE53656).
Project description:The transcription factor SNAIL1 is a master regulator of epithelial-to-mesenchymal transition, a process entailing massive gene expression changes. To better understand SNAIL1-induced transcriptional reprogramming we performed time-resolved transcriptome analysis upon conditional SNAIL1 expression in colorectal cancer cells. Bioinformatic analyses indicated that SNAIL1 strongly affected Wnt/β-Catenin pathway activity. This correlated with upregulation of LEF1, a nuclear binding partner of β-Catenin. Several tumour entities, including aggressive mesenchymal colorectal cancers, exhibit positively correlated LEF1 and SNAIL1 expression, and elevated LEF1 levels parallel increased colorectal cancer patient mortality. Comparative gene expression profiling suggested that 35% of Snail1-induced transcriptional changes are attributable to LEF1. LEF1 stimulates Wnt/β-Catenin pathway feedback inhibitor expression, causes cell-cycle arrest in vitro, and retards xenograft tumour growth. Conversely, LEF1-deficiency and preventing the β-Catenin-LEF1 interaction impaired the ability of SNAIL1 to alter Wnt/β-catenin target gene expression and to induce cancer cell invasion. Although LEF1 did not autonomously induce epithelial-mesenchymal transition, LEF1 is a critical factor acting downstream of SNAIL1. Apparently, SNAIL1 employs LEF1 as alternative effector to redirect Wnt/β-catenin pathway activity towards anti-proliferative and pro-invasive gene expression.