Objective Chronic inflammation is a risk factor in colorectal cancer (CRC) and reactive oxygen species (ROS) released by the inflamed stroma elicit DNA damage in epithelial cells. We sought to identify new drivers of UC and inflammatory CRC.
Design The study uses samples from patients with UC, mouse models of colitis and CRC and mice deficient for the epithelial-to-mesenchymal transition factor ZEB1 and the DNA repair glycosylase N-methyl-purine glycosylase (MPG). Samples were analysed by immunostaining, qRT-PCR, chromatin immunoprecipitation assays, microbiota next-generation sequencing and ROS determination.
Results ZEB1 was induced in the colonic epithelium of UC and of mouse models of colitis. Compared with wild-type counterparts, Zeb1-deficient mice were partially protected from experimental colitis and, in a model of inflammatory CRC, they developed fewer tumours and exhibited lower levels of DNA damage (8-oxo-dG) and higher expression of MPG. Knockdown of ZEB1 in CRC cells inhibited 8-oxo-dG induction by oxidative stress (H2O2) and inflammatory cytokines (interleukin (IL)1β). ZEB1 bound directly to the MPG promoter whose expression inhibited. This molecular mechanism was validated at the genetic level and the crossing of Zeb1-deficient and Mpg-deficient mice reverted the reduced inflammation and tumourigenesis in the former. ZEB1 expression in CRC cells induced ROS and IL1β production by macrophages that, in turn, lowered MPG in CRC cells thus amplifying a positive loop between both cells to promote DNA damage and inhibit DNA repair.
Conclusions ZEB1 promotes colitis and inflammatory CRC through the inhibition of MPG in epithelial cells, thus offering new therapeutic strategies to modulate inflammation and inflammatory cancer.
- colorectal cancer
- inflammatory bowel disease
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OdB, LS-M and MC contributed equally as co-first authors to the work.
36 CN, NP-P, MCM-C and LS contributed equally as co-second authors to the work.
Contributors OdB, LS-M and MC performed most of the experimental work in the study. CN and LS assisted in some analyses of mRNA expression; NP-P and MCM-C carried out some immunostaining experiments. RdC performed the microbiota next-generation sequencing and its bioinformatics analysis. MJF-A assisted with the procurement of some of the human samples as well as with the pathology analyses of human and mouse tissue immunostaining. DSD, AC, JM, AS and DCD provided important materials and insights to the study. AP conceived and supervised the study, and wrote the manuscript. All authors provided critical comments to the manuscript.
Funding The different parts of this study were independently funded by grants to AP from Catalan Agency for Management of University and Research Grants (AGAUR) (2014-SGR-475 and 2017-SGR-1174), Ministry of Economy and Competitiveness (SAF2014-52874-R and SAF2017-84918-R, National Scientific and Technical Research and Innovation 2013–2016 Plan, which is co-financed by the European Regional Development Fund of the European Union Commission), Fundació La Marató de TV3 (201330.10) and Avon Foundation SAU (AFSAU). The IDIBAPS Institute is partly funded by the CERCA Programme of Generalitat de Catalunya. OdB was subsequently supported by a fellowship from the Spanish Ministry of Education, Culture and Sports (MECS) (FPU programme, AP2010-5489) and by grants 2014-SGR-475, 201330.10 and AFSAU. LS-M is recipient of a PhD scholarship from MECS (FPU Programme, FPU14/06217). MC is supported by grants 201330.10 and SAF2014-52874-R to AP. CN was recipient of a PhD scholarship from AGAUR (AGAUR-2015-FI_B-00121) and later supported by grant 2017-SGR-1174 to AP. NPP and MCMC are recipients of PhD scholarships from the Spanish Ministry of Economy and Competitiveness (FPI Programme, BES-2015-073163 and BES-2015-075757, respectively). LS was supported by grants 201330.10, AVFSAU and 2017-SGR-1174 to AP.
Competing interests None declared.
Ethics approval The use of human samples was approved by the Clinical Ethics Research Committee at the Hospital Clinic of Barcelona under reference HCB/2018/0157. The use of mouse models followed the guidelines of the Animal Experimentation Ethics Committee at the University of Barcelona (Spain) and was approved under reference UB/301/16 and UB/302/16.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Obtained.
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