Dataset Information

Mlh1 deficiency in normal mouse colon mucosa associates with chromosomally unstable colon cancer.

ABSTRACT: Colorectal cancer (CRC) genome is unstable and different types of instabilities, such as chromosomal instability (CIN) and microsatellite instability (MSI) are thought to reflect distinct cancer initiating mechanisms. Although 85% of sporadic CRC reveal CIN, 15% reveal mismatch repair (MMR) malfunction and MSI, the hallmarks of Lynch syndrome with inherited heterozygous germline mutations in MMR genes. Our study was designed to comprehensively follow genome-wide expression changes and their implications during colon tumorigenesis. We conducted a long-term feeding experiment in the mouse to address expression changes arising in histologically normal colonic mucosa as putative cancer preceding events, and the effect of inherited predisposition (Mlh1+/-) and Western-style diet (WD) on those. During the 21-month experiment, carcinomas developed mainly in WD-fed mice and were evenly distributed between genotypes. Unexpectedly, the heterozygote (B6.129-Mlh1tm1Rak) mice did not show MSI in their CRCs. Instead, both wildtype and heterozygote CRC mice showed a distinct mRNA expression profile and shortage of several chromosomal segregation gene-specific transcripts (Mlh1, Bub1, Mis18a, Tpx2, Rad9a, Pms2, Cenpe, Ncapd3, Odf2 and Dclre1b) in their colon mucosa, as well as an increased mitotic activity and abundant numbers of unbalanced/atypical mitoses in tumours. Our genome-wide expression profiling experiment demonstrates that cancer preceding changes are already seen in histologically normal colon mucosa and that decreased expressions of Mlh1 and other chromosomal segregation genes may form a field-defect in mucosa, which trigger MMR-proficient, chromosomally unstable CRC.

SUBMITTER: Pussila M

PROVIDER: S-EPMC5973430 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Mlh1 deficiency in normal mouse colon mucosa associates with chromosomally unstable colon cancer.

Pussila Marjaana M Törönen Petri P Einarsdottir Elisabet E Katayama Shintaro S Krjutškov Kaarel K Holm Liisa L Kere Juha J Peltomäki Päivi P Mäkinen Markus J MJ Linden Jere J Nyström Minna M

Carcinogenesis 20180501 6

Colorectal cancer (CRC) genome is unstable and different types of instabilities, such as chromosomal instability (CIN) and microsatellite instability (MSI) are thought to reflect distinct cancer initiating mechanisms. Although 85% of sporadic CRC reveal CIN, 15% reveal mismatch repair (MMR) malfunction and MSI, the hallmarks of Lynch syndrome with inherited heterozygous germline mutations in MMR genes. Our study was designed to comprehensively follow genome-wide expression changes and their impl ...[more]

PMID: 29701748

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Project description:Colorectal cancer is a common cancer with a poor prognosis in both males and females. The influence of bisphenol A (BPA), a widely used environmental contaminant, in colon cancer development and progression is not well identified, in spite of the fact that the most common mode of exposure to BPA is ingestion. The aim of this work is to elucidate the carcinogenic effects of BPA in the colon in vitro. We analyzed BPA's effects on human colon epithelial (HCoEpiC) and colon cancer (HCT116) cells. BPA exerted cytotoxic effects and augmented the 5FU cytotoxicity on both cell lines at high doses, while it did not show this effect at low doses. Therefore, we focused on studying the effects of low-dose (0.0043 nM) exposure on normal colonic epithelial cells for a long period of time (two months), which is more consistent with environmental exposure levels and patterns. BPA increased cellular invasiveness through collagen and the ability to anchorage-independent cell growth, as measured by colony formation in soft agar, which could support oncogenicity. To gain insights into the mechanism of these actions, we performed transcriptomic analysis using next-generation sequencing, which revealed 340 differentially expressed transcripts by BPA in HCT116 and 75 in HCoEpiC. These transcripts belong in many cancer-related pathways such as apoptosis, cell proliferation, signal transduction, and angiogenesis. Some of the significant genes (FAM83H, CXCL12, PITPNA, HMOX1, DGKZ, NR5A2, VMP1, and ID1) were confirmed by quantitative RT-PCR. Furthermore, BPA induced the phosphorylation of protein kinases such as JNK1/2/3, GSK-3α/β, AMPKα1, AKT1/2/3, AMPKα2, HSP27, β-catenin, STAT2, Hck, Chk2, FAK, and PRAS40 in HCoEpiC, as well as GSK-3α/β, p53, AKT1/2/3, p70 S6 kinase, and WNK1 in HCT116. The majority of these proteins are involved in potential carcinogenic pathways. Taken together, these data suggest that BPA plays a role in colon carcinogenesis, and they provide insights into the molecular mechanisms of colon epithelial cell transformation by BPA. Increasing exposure to environmental toxins such as BPA can explain the increasing incidence of colorectal cancer.

Dataset Information

Mlh1 deficiency in normal mouse colon mucosa associates with chromosomally unstable colon cancer.

Publications

Mlh1 deficiency in normal mouse colon mucosa associates with chromosomally unstable colon cancer.

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