CHI3L1 Protein Differentially Expressed in Appendicitis and Appendix Carcinomas

Chitinase-3-like protein 1 (CHI3L1) is a 40-kDa heparin-and-chitin binding glycoprotein, mainly produced by some cell types, including colonic epithelial cells (CECs) chondrocytes, osteosarcoma cells, macrophages, smooth muscle cells, and neutrophils. High levels of CHI3L1 are associated with poor prognosis and accelerate the proliferation of colon cancer cells.

Clinical Laboratorians at The Affiliated Taian City Central Hospital of Qingdao University (Taian, China) collected blood and appendix samples from 46 acute appendicitis and 14 appendix carcinomas that had surgery at the hospital between May 2019 and November 2021. The patients were 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.

The patients' venous blood samples were taken before the appendectomy. Blood neutrophil to lymphocyte ratio (NLR), CHI3L1, C-reactive protein (CRP), interleukin-6 (IL-6, Shenzhen Lifotronic Biotech Co. Ltd, Shenzhen, China), and serum amyloid A (SAA, Upper Bio-TECH Pharma Co. Ltd, Shanghai, China) were measured. NLR was analyzed from a blood routine test. For immunohistochemical staining, sections were rinsed in distilled water three times, and the Quick Antigen Retrieval Solution (Beyotime Biotechnology, Haimen, China) was used for antigen retrieval. Next, 3% bovine serum albumin was used for nonspecific binding blockage, and the sections were incubated with an anti-CHI3L1 antibody at 4° C overnight. Fluorescence images were obtained using an Olympus FV3000 confocal microscope (Olympus, Center Valley, Pa, USA).

The investigators reported that 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.

The authors concluded that the patients with appendicitis had an enhanced CHI3L1 expression, associated with increased NLR, CRP, IL-6, and SAA. Moreover, CHI3L1 was crucial in patients with appendiceal neuroendocrine neoplasms. The study was published on November 29, 2022 in the Journal of Clinical Laboratory Analysis.