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: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.
Project description:During canonical Wnt signalling the activity of nuclear beta-catenin is largely mediated by the TCF/LEF family of transcription factors. To challenge this view we used the CRISPR/Cas9 genome editing approach to generate HEK 293T cell clones simultaneously carrying loss-of-function alleles of all four TCF/LEF genes. Exploiting unbiased whole transcriptome sequencing studies, we found that a subset of beta-catenin transcriptional targets did not require TCF/LEF factors for their regulation. Consistent with this finding, we observed in a genome-wide analysis that beta-catenin occupied specific genomic regions in the absence of TCF/LEF. Finally, we revealed the existence of a transcriptional activity of beta-catenin that specifically appears when TCF/LEF factors are absent, and refer to this as beta-catenin-GHOST response. Collectively, this study uncovers a previously neglected modus operandi of beta-catenin that bypasses the TCF/LEF transcription factors.