To Örebro University

Background: Better prognostic measures for ulcerative colitis (UC) could significantly advance patient care. While the prognostic capacity of circulating proteins in UC has been explored, the role of mucosal proteins remains largely unknown. We examined mucosal protein markers in patients with incident ulcerative colitis and evaluated their prognostic value.

Methods: Biopsies from macroscopically inflamed colonic/rectal mucosa of adult patients in the Swedish inception cohort of IBD (SIC IBD) were obtained at diagnosis of UC. Patients were followed prospectively, and clinical data were recorded after 3 and 12 months. Disease course was categorised as indolent or aggressive at 12 months, based on a composite outcome of colectomy, hospital admission for active disease, treatment refractoriness towards ≥2 biological agents; the use of >2 courses of corticosteroids, or a cumulative dose of >2.5 g. Relative estimates of 162 protein markers were assessed in homogenised tissue supernatants, using proximity extension assay technology (Olink Proteomics, Uppsala, Inflammation and Oncology II panel). Mann-Whitney U test, with Benjamini-Hochberg correction was used to identify differentially regulated mucosal proteins in aggressive vs indolent disease course, with a 5% false discovery rate (FDR). Smoothly clipped absolute deviation regularised logistic regression models were used to identify prognostic signatures distinguishing aggressive from indolent disease course. Performance was estimated in a leave-one-out cross-validation and reported as the area under the receiver operating characteristic (ROC) curve (AUC).

Results: 117 patients provided a macroscopically inflamed colonic/rectal biopsy at diagnosis of UC. Basic demographics and clinical characteristics are presented in Table 1. Relative protein levels of WFdc2 and CCL20 were significantly lower in lysates from patients developing an aggressive course vs patients developing an indolent course, while estimates of MMP1, CCL11, WISP-1, OPG, RSPO3 and VEGFR2 were higher (Figure 1A). Regularized logistic regression identified signatures restricted to 28 proteins, distinguishing aggressive from indolent UC courses, yielding an AUC of 0.68 (95% confidence interval (CI): 0.56-0.80) for left-out samples (Figure 1B). Incorporating extent of inflammation at diagnosis in the model improved the AUC to 0.71 (95% CI: 0.60-0.83).

Conclusion: We identified prognostic mucosal protein signatures associated with future course of ulcerative colitis by analysing inflamed mucosal biopsies that were obtained at diagnosis. These protein markers may highlight pathways of relevance for ulcerative colitis outcomes.