Project description:The genome-wide miRNA expression analysis was performed in clinical samples, comprising 15 BRAF-mutant and 15 non-KRAS/BRAF-mutant colorectal cancers by using a SurePrint G3 Human miRNA microarray. clinical samples, comprising 15 BRAF-mutant and 15 non-KRAS/BRAF-mutant colorectal cancers by using a SurePrint G3 Human miRNA microarray.
Project description:Despite advances in the detection and management of colorectal cancers, resistance to anti-cancer therapies remains a significant challenge. Activating mutations in KRAS and BRAF are frequently observed in colorectal cancers and have been associated with aggressive tumors and poor survival after chemotherapy. In the present study, we demonstrate that mutations in KRAS/BRAF alter the enhancer landscape of tumor cells, which leads to the resistance of the cornerstone colorectal cancer chemotherapeutic agent 5-fluorouracil (5-FU) through activation of transcription factor GATA1. Targeted inhibition of GATA1 reverses epigenetic changes in KRAS mutant cells and restores sensitivity to 5-FU. These results indicate a novel therapeutic opportunity for tailoring individualized therapy in human colorectal cancer.
Project description:Resistance to PI3K/mTOR inhibitor PF-04691502 in KRAS mutant colorectal cancer models reveals a sensitivity to combination with EGFR inhibition
Project description:Background: The Ras pathway genes KRAS, BRAF or ERBBs have somatic mutations in ~60% of human colorectal carcinomas. At present, it is unknown whether the remaining cases lack mutations activating the Ras pathway, or whether they have acquired mutations in genes hitherto not known to belong to the pathway. Methods: To address the second possibility, and extend the compendium of Ras pathway genes, we used genome-wide transposon mutagenesis of two human colorectal cancer cell systems deprived of their activating KRAS or BRAF allele to identify genes enabling growth in low glucose, a Ras pathway phenotype, when targeted. Results: Of the 163 recurrently targeted genes in the two different genetic backgrounds, one third were known cancer genes and one-fifth had links to the EGFR/Ras/MAPK pathway. When compared to cancer genome sequencing datasets, 9 genes also mutated in human colorectal cancers were identified. Among these, stable knock-down of FOXO3, NCOA3, and TCF7L2 restored growth in low glucose but reduced MEK/MAPK phosphorylation, reduced anchorage-independent growth, and modulated expressions of GLUT1 and Ras pathway related proteins. Knock-down of NCOA3 and FOXO3 significantly decreased the sensitivity to cetuximab of KRAS mutant but not wild-type cells. Conclusions: This work establishes a proof-of-concept that human cell based genome-wide forward genetic screens can assign genes to pathways with clinical importance in human colorectal cancer.
Project description:The genome-wide miRNA expression analysis was performed in clinical samples, comprising 15 BRAF-mutant and 15 non-KRAS/BRAF-mutant colorectal cancers by using a SurePrint G3 Human miRNA microarray.
Project description:BRAF mutant colorectal cancer has a poor prognosis and gets resistant to BRAF inhibitors quickly. This study aims to clarify the mechanism of resistance to BRAFi. We found MCU1-C is overexpressed in BRAF mutant colorectal cancer and targeting MUC1-C genetically and pharmacologically sensitized Colorectal cancer cells to BRAF inhibitor. This finding suggests that MUC1-C could be a new therapeutic target for BRAF mutant colorectal cancer.
Project description:A collection of genetically engineered mouse models (GEMM) of colorectal cancer (CRC) were created, and primary tumors from these GEMMs were analyzed. Primary CRC tumors from these GEMMs were genotyped to confirm that they contain the core genetic lesions of interest, including APC, P53, KRAS, and BRAF. Primary tumors from GEMMs with combinations of lesions of interest were analyzed by whole genome expression, and their expression profiles were compared to determine how they segregate. Signatures were then generated from GEMM tumors of interest and compared to human clinical datasets with expression and outcome data. Primary tumors from CRC GEMMs with different combinations of mutant alleles of interested were generated and analyzed. Alleles include mutant forms of APC (A), P53 (P), KRAS (K) and BRAF (B).
Project description:Tumor cells carrying KRAS mutations activate the NF-?B pathway by different mechanisms, which contribute to the acquisition of essential cancer properties. The BRAF kinase, a downstream mediator of KRAS, is also mutated in a subset of colorectal cancers (CRC), which predicts bad prognosis and therapy resistance. However, nothing is known on whether NF-?B participates of BRAF-mediated tumorigenesis. We here found that in CRC cells, mutant BRAF does not trigger canonical or alternative NF-?B signaling but induces p45-IKK? activation. Moreover, IKK? activity is required for BRAF-induced transformation and to support BRAF-dependent transcription in CRC cells. Activation of p45-IKK? downstream of BRAF requires the TAK1 kinase, and is associated to the endosomal compartment. Inhibition of endosomal V-ATPase abolished p45-IKK? phosphorylation, and induced apoptosis of BRAF mutated CRC cells. Pharmacologic inhibition of endosome acidification reduced the in vivo growth of tumors carrying mutant BRAF, and abrogated the metastatic capacity of a primary human CRC tumor with acquired resistance to standard chemotherapy in an orthotopic xenograft model. 18 samples were analyzed: HT29 controls (n=3); HT28 BRAF inhibited (n=3), WiDr controls (n=3); WiDr BRAF inhibited (n=3); WiDr transduced with control shRNA (n=3) and WiDr transduced with shRNA against IKKalpha (n=3)