Differential expression of Chitinase 3‐Like 1 protein in appendicitis and appendix carcinomas

BACKGROUND: Chitinase 3‐Like 1 (CHI3L1) has been used as an inflammatory biomarker for a variety of diseases, but its expression in acute appendicitis and appendix carcinomas remains unclear. METHODS: Sixty cases of patients were studied, including 46 acute appendicitis and 14 appendix carcinomas. We divided the acute appendicitis group into acute uncomplicated appendicitis (AUA), suppurative appendicitis (SA), and gangrenous appendicitis (GA). The appendix carcinoma group was divided into appendiceal neuroendocrine neoplasms (ANENs) and appendiceal mucinous neoplasms (AMN). Controls were 32 healthy donors. Blood neutrophil to lymphocyte ratio (NLR), CHI3L1, C‐reactive protein (CRP), interleukin‐6 (IL‐6), and serum amyloid A (SAA) were measured in the patients. Meanwhile, immunohistochemistry and immunofluorescence were used to identify the expression level and location of CHI3L1 in different cell types in appendix tissues. RESULTS: Compared with the controls, CHI3L1 serum levels were up‐regulated in SA, GA, and AMN groups, while no significant difference was observed in the AUA and ANEN groups. Immunofluorescence revealed that CHI3L1 expression was high in macrophages and adenocarcinoma cells of appendix tissues but not in the neuroendocrine carcinoma tissues. Moreover, levels of NLR and CRP in the SA and GA groups were considerably higher than in the control group. IL‐6 and SAA in SA, GA, ANENs, and AMN groups were also increased compared with the control group. In addition, CHI3L1 displayed good performance in predicting appendicitis, with an AUC of 0.862. CONCLUSION: CHI3L1 was highly expressed in acute appendicitis and appendiceal mucinous neoplasms, which can be used as a novel biomarker predicting appendicitis.