A. Dias1, E. Gomes1, M. Silva1, Â. Fernandes1, M. Garrido2, R. Marcos-Pinto2, P. Lago2, S. Pinho1
1i3S – Institute for Research and Innovation in Health, University of Porto, Immunology- Cancer and Glycomedicine Group, Porto, Portugal, 2Department of Gastroenterology, Porto Centre Hospital, Porto, Portugal
Background
Ulcerative colitis (UC) is a chronic inflammatory disorder of the gastrointestinal tract being considered a serious risk factor for the development of colitis-associated cancer (CAC). However, the molecular mechanisms underlying CAC progression are still elusive. We previously showed that decreased expression of MGAT5 glycogene on intestinal T lymphocytes from UC patients was associated with a hyperimmune response and with disease severity (Dias, AM et al. HMG,2014; Dias, AM et al. PNAS, 2018). On the other hand, we also demonstrated that the aberrant expression of MGAT5 glycogene in gastrointestinal cancer cells was associated with tumour invasiveness and progression (Carvalho S et al., Oncogene 2015). However, whether this differential expression of glycans in colitis and cancer contexts mediated by MGAT5 glycogene constitutes a new mechanism in CAC remains completely unknown.
Methods
A well-characterised cohort of paraffin samples from CAC patients at different stages of carcinogenesis (colitis; dysplasia and colon cancer) were evaluated by immunohistochemistry, using specific lectins to evaluate the N-glycosylation profile either in stroma or in epithelial cells. Furthermore, in vivo studies (using Azoxymethane (AOM)/dextran sodium sulphate (DSS) to induce CAC) were conducted in MGAT5 wild-type and null mice. The combined glycoimmune profile of colonic cells was analysed by flow cytometry. Analysis of RNAseq data from colitis-associated cancer mice model (the AOM/DSS mouse model) was performed to decipher the glyco-fingerprint in colonic cells during colitis; low- and high-grade dysplasia and adenocarcinoma.
Results
Our cross-sectional study revealed a distinct glycoprofile in stroma, characterised by a decreased expression of branched N-glycans in colitis followed by increased expression in dysplasia and colon carcinoma stages corroborated by the RNASeq analysis on the colon of AOM/DSS mouse model. Additionally, colonic T cells isolated from both AOM/DSS MGAT5 WT and KO mice presented a distinct glycoprofile along CAC development.
Conclusion
Our preliminary results both from human and mice samples demonstrate a distinct glycoimmuno profile along the colitis-associated carcinoma cascade, which potentially represents a biomarker to early identify risk UC patients.
