Blood Serum Zonulin in Colorectal Cancer, Autoimmune Bowel Diseases, and Irritable Bowel Syndrome

Zonulin content in blood serum of patients with colorectal cancer (CRC; n=152; 30-84 years) and patients with large bowel adenomas (n=32; 39-82 years) was measured by standardized kit IDK Zonulin ELISA (Immundiagnostik AG). The healthy control group (n=50) comprised volunteers (27 women, 23 men; 25-68 years); pathological control group (n=84) - patients (55 women, 29 men;18-84 years) with irritable bowel syndrome (n=29), Crohn's disease (n=5), and ulcero-necrotic colitis (n=50). In comparison to healthy control group, the level of zonulin was significantly increased in CRC patients (p<0.0000001) and in patients with benign large bowel tumors (p<0.004), as well as in patients with inflammatory intestine diseases and with irritable bowel syndrome (p<0.0002). Zonulin level in blood serum of CRC patients was slightly, but significantly higher (p<0.05) than in the group of pathological control. ROC curve construction revealed that at optimal zonulin cut-off level (52.2 ng/ml), the diagnostic sensitivity of CRC detection was 66.7% and specificity relative to healthy control was 81.8%. The specificity relative to the combined control group (healthy control+non-tumor bowel diseases) was only 68.9%. Thus, no acceptable cut-off levels for differentiation between malignant and benign tumors, as well as between tumor and non-tumor large bowel pathologies were found. Analysis of the associations between serum zonulin level and the main clinical and pathological characteristics of CRC demonstrated that the level of this marker increased with disease progression (p<0.01; Kruskal-Wallis test), but was not associated with individual criteria of the TNM system, tumor localization, histological structure, and malignancy grade.