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Single-cell transcriptomic survey of adenomatous polyposis patients with germline APC mutations

ABSTRACT: Patients with germline APC mutations are recognized by hundreds of adenoma polyps in colon, which will give rise to adenocarcinoma inevitably. Over 700 germline APC mutations have been reported to be the leading cause of adenomatous polyposis. However, the underlying mechanism of APC mutation triggered colonic cancer remains mysterious. Here, using a modified STRT-seq protocol, we analyzed over 4000 single cells from the four matching adenomatous polyposis, adenocarcinoma, adjacent normal colon tissue and one lymphatic metastasis from four adenomatous polyposis patients with APC mutations. We identified the main cell types existed in human intestine such as B cells, mast cells, T cells, macrophage cells, endothelial cells, stromal cells and epithelial cells. And the proportional changes of various cell types during the development of adenoma were showed. The transcriptomic similarities and differences between adenoma, adenocarcinoma and adjacent normal tissue were comprehensively investigated. For better understanding the tumor progression process, we also take advantage of other genomic signatures, such as SNV and CNV. We found that the gene expression signatures of adenoma and adenocarcinoma were largely similar when compared with adjacent normal tissue. But the mutation accumulation was indeed observed during the progression from adenoma to adenocarcinoma. To summarized, our work will help us accurately investigate the pathogenic mechanism and heterogeneity of APC inactive mutation triggered colonic cancer, which will also help us better understand the non-familial colorectal cancers

ORGANISM(S): Homo sapiens

PROVIDER: GSE109308 | GEO | 2019/10/25

REPOSITORIES: GEO

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Project description:Expression profiling is a well established tool for the genome-wide analysis of the transcriptional activity of human neoplasia. However, the high sensitivity of this approach combined with the well-known cellular and molecular heterogeneity of cancer often result in extremely complex and extended expression signatures of difficult functional interpretation. The majority of sporadic colorectal cancer cases are triggered by mutations in the APC tumor suppressor gene leading to constitutive activation of the Wnt/b-catenin signaling pathway and adenoma formation. Notwithstanding this common genetic basis, colorectal cancers are very heterogeneous in their degree of differentiation, growth rate and malignant potential. Here, we applied cross-species comparison of expression profiles of intestinal polyps derived from hereditary colorectal cancer patients carrying APC germline mutations, and from a mouse model carrying a targeted inactivating mutation in the mouse homologue Apc. This comparative approach resulted in the establishment of a conserved signature encompassing 166 genes differentially expressed between adenomas and normal intestinal mucosa in both species. Functional analysis of the conserved genes revealed a general increase in cell proliferation and the activation of the Wnt/b-catenin signal transduction pathway, as expected from the selection of APC/Apc-mutant intestinal adenomas. Moreover, the conserved signature is able to resolve expression profiles from hereditary polyposis patients carrying APC germline mutations from those with bi-allelic incativation of the MYH gene. Keywords: normal versus tumor comparison; compare expression profiles from microdissected samples with distinct germline mutations (FAP vs. MAP). Here, we report the expression profiles from normal and intestinal adenomatous tissue from FAP (familial adenomatous polyposis) and MAP (MUTY-associated polyposis) patients with established APC and MUTY germline mutations. Total RNA samples were obtianed by laser capture microdissection.

Project description:Mutation of the adenomatous polyposis coli (APC gene), an early event in the adenoma-carcinoma sequence, is present in 70-80% of sporadic human colorectal adenomas and carcinomas. To test the hypothesis that mutation of the APC gene alters microbial interactions with host intestinal mucosa prior to the development of polyposis, culture-independent methods (targeted qPCR assays and Illumina sequencing of the 16S rRNA gene V1V2 hypervariable region) were used to compare the intestinal microbial composition of 30 six-week old C57BL/6 APCMin/+ and 30 congenic wild type (WT) mice. The results demonstrate that similar to 12-14 week old APCMin/+ mice with intestinal neoplasia, 6 week old APCMin/+ mice with no detectable neoplasia, exhibit an increased relative abundance of Bacteroidetes spp in the colon. Parallel mouse RNA sequence analysis, conducted on a subset of proximal colonic RNA samples (6 APCMin/+, 6 WT) revealed 130 differentially expressed genes (DEGs, fold change ? 2, FDR <0.05). Hierarchical clustering of the DEGs was carried out by using 1-r dissimilarity measurement, where r stands for the Pearson correlation, and Ward minimum variance linkage, in order to reduce the number of input variables. When the cluster centroids (medians) were included along with APC genotype as input variables, analysis of variance and covariance (ANCOVA) with stepwise variable selection, selected two of seven mouse gene clusters, in addition to APC genotype, as significantly associated (p = 0.011 and p = 0.004) with the increased relative abundance of Bacteroidetes spp. One of the two clusters includes several downregulated genes encoding immunoglobulin variable regions and non-protein coding RNAs. These results support the concept that mutation of the APC gene alters colonic-microbial interactions prior to polyposis. It remains to be determined whether interventions directed at ameliorating dysbiosis in APCMin/+mice, such as through probiotics, prebiotics or antibiotics, could reduce tumor formation. Comparing the differential gene expressions in proximal colonic mucosal samples from 6 six-week-old female Apc Min/+ and 6 six-week-old female WT mice

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Single-cell transcriptomic survey of adenomatous polyposis patients with germline APC mutations

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