CpG methylation in the TGFB1 and IL-6 gene promoters serve as surrogate biomarkers for diagnosis of IBD in children

Abstract

Abstract Crohn’s disease (CD) and ulcerative colitis (UC) are recurrent, chronic forms of inflammatory bowel diseases (IBD), the diagnosis of which can entail long delays. The delays can lead to disease presentation with complications and high morbidity. Therefore, better diagnostic markers for IBD are required. We investigated whether methylation marks in the TGFB1 and IL-6 gene promoters could be of diagnostic utility in IBD. To this end, we conducted a case-control study using peripheral blood DNA samples from 67 CD and 37 UC pediatric patients, and from 43 age-matched healthy controls. The patients were recruited from three pediatric gastroenterology clinics across Canada. The DNA samples were processed to identify methylation sites (CpG) across the promoter regions of the TGFB1 and IL-6 genes using the Sequenom technology. After implementing quality control measures, and initial non-parametric univariate (Man-Whitney U test) analyses, multivariate logistic regression analyses was carried out to identify models with the best fit (Akaike Information Criteria) and the greatest discriminatory capabilities (Area Under the Receiver Operating Curve). Logistic regression analysis showed that a model comprising 14 TGFB1 CpG sites had high discriminatory ability to separate CD from controls (AUC=0.94). Similarly, a logistic model comprising 9 CpG sites in the TGFB1 gene had near perfect ability to discriminate between UC and controls (AUC=0.99). A logistic model comprising three CpG sites in the TGFB1 gene had moderate ability (AUC=0.81) to discriminate between CD and UC. In conclusion, CpG methylation in the TGFB1 gene promoter has high discriminative power for identifying CD and UC, and could serve as an important diagnostic markers.