Project description:Almost all colorectal cancers (CRC) present with mutations in the Apc gene, leading to unrestrained Wnt activation and the initiation of tumour development. We previously reported the competitive benefit of Apc-mutant intestinal stem cells (ISCs) within the crypt, however, the mechanism by which they outcompete their wild type (WT) neighbours remained elusive. Here, we studied the effect of Apc-mutants using an in vitro culture system of WT (Lgr5-CreErt2) and Apc-/- (Lgr5-CreErt2;Apcfl/fl) organoids . The expression patterns of WT and Apc-/- organoids revealed significant upregulation in specific secreted Wnt antagonists Notum, Wif1 and Dkk2. Furthermore, we studied the effect of the secreted antagonist by treating WT organoids with either WT or Apc-/- conditioned medium (CM) for 48 hours and observed a significant decrease in stem cell markers and an increase in goblet cell markers. We report that Apc-mutants act as bona fide supercompetitors by secreting Wnt antagonists that result in active differentiation of WT ISCs.
Project description:We have generated a mouse model for tumor initiation carrying a mutation in APC and lacking IKKα in intestinal epithelial cells. IKKα-deficient intestinal cells primarily failed to generate adenomas, and the few adenomas arising in this background displayed a significant reduction in cell proliferation. Using an in vitro model for intestinal tumoroids (derived from adenoma initiating cells), we have performed RNA sequencing of wild type and IKKα-deficient intestinal tumoroids. This has demonstrated that epithelial IKKα controls transcription of stem cell-related genes and genes associated with proliferation and apoptosis.
Project description:Loss-of-function mutations in the tumour suppressor APC are an initial step in intestinal tumorigenesis. APC-mutant intestinal stem cells (ISCs) outcompete their wild type neighbours through the secretion of Wnt antagonists, accelerating the fixation and subsequent rapid clonal expansion of mutants. Reports of polyclonal intestinal tumours in patients and mouse models appear at odds with this process. Here we combine multicolour lineage tracing with chemical mutagenesis in mice to show that a large proportion of intestinal tumours have a multiancestral origin. Polyclonal tumours retain a structure comprising subclones with distinct Apc mutations and transcriptional states, driven predominantly by differences in KRAS and MYC signalling. These pathway level changes are accompanied by profound cancer stem cell phenotypic differences. Importantly, these findings are confirmed by introducing an oncogenic Kras mutation that results in predominantly monoclonal tumour formation. Further, polyclonal tumours have accelerated growth dynamics suggesting a link between polyclonality and tumour progression. Together, these findings demonstrate the role of interclonal interactions in promoting tumorigenesis through non-cell autonomous pathways dependent on the differential activation of oncogenic pathways between clones.
Project description:EphB receptors regulate the proliferation and positioning of intestinal stem and progenitor cells. In addition, they can act as tumor promoters for adenoma development, but suppress progression to invasive carcinoma. Here we used imatinib to abrogate Abl kinase activity in ApcMin/+ mice and in mice with LGR5+ stem cells genetically targeted for APC. This treatment inhibited the tumor-promoting effects of EphB signaling without attenuating EphB-mediated tumor suppression, demonstrating the role of EphB signaling in intestinal tumor initiation. The investigated treatment regimen extended the lifespan of ApcMin/+ mice, and reduced cell proliferation in cultured slices of adenomas from FAP patients. These findings connect the EphB signaling pathway to the regulation of intestinal adenoma initiation via Abl kinase. Our findings may have clinical implications for pharmacological therapy against adenoma formation and cancer progression in patients predisposed to develop colon cancer. We used microarray to assess the short term (3h and 12h) effects on gene expression in colon stem and progenitor cells after administration of Imatinib.
Project description:The APC (Adenomatous Polyposis Coli) gene encodes a large multidomain protein that plays an integral role in the Wnt/beta-catenin signaling pathway. The loss-of-function mutation in APC is considered the earliest genetic alteration in the course of adenoma-carcinoma sequence of colorectal cancer progression, and the resulting constitutive activation of Wnt/beta-catenin signaling is required for the maintenance of advanced colorectal cancer. In order to identify genes affected by loss of Apc function, we performed transcription profiling of mouse small intestinal tissues comparing polyps with normal mucosa of Apc+/Delta716 mice. We isolated total RNA from intestinal polyps and normal intestinal mucosa from 3 individual Apc+/Delta716 mice. Total RNA samples were then employed to perform microarray analysis (Agilent Whole Mouse Genome Microarray Ver. 2.0, 4x44K).
Project description:Amoung their pleiotropic functions, a role was recently assigned for b-arrestin scaffold proteins in tumor growth, angiogenesis and invasion. In order to elucidate the roles of b-arrestins in tumour developement in intestinal epithelium initiated by Apc mutation, we determined the effects of b-arrestin gene deletion on intestinal polypolis using ApcD14/+ mice, a relevant mouse model of human intestinal tumorigenesis.Here we show that unlike b-arrestin1, absence of b-arrestin2 dramatically decreased the number of spontaneously developping intestinal tumors in ApcD14/+ mice.The size of residual tumors was similarto that of controls, suggesting that their growth is b-arrestin2-independent. This result demonstrated a role for b-arrestin2 in the early development of a tumor subset. Gene expression profils analysis of ApcD14/+:Arrb2+/+ and ApcD14/+:Arrb2-/- tumors showed two distinct clusters among ApcD14/+:Arrb2+/+ tumors and one of them was statistically more correlated to ApcD14/+:Arrb2-/- tumors than to the other ApcD14/+:Arrb2+/+ cluster, eventhough a number of genes saw their expression affected in ApcD14/+:Arrb2-/- tumors only. Altogether, our data unravel an unexpected early diversity among intestinal tumors and a crucial role for b-arrestin2 in early tumor development in Apc-mutated mice. 16 tumors from ApcD14/+:Arrb2+/+ mice and 13 tumors from ApcD14/+:Arrb2-/- mice
Project description:Vil-CreERT2 was used to drive loss of APC (Adenomatous polyposis coli) in the murine intestinal epithelium. 4 days post induction, mice were sampled and 1cm of tissue from the proximal intestine was collected into RNA later. This was compared to control (wild-type) intestine. This analysis allows investigation of transcriptional changes following APC loss (and therefore activation of the WNT signalling pathway).