Do Elevated YKL-40 Levels Drive the Immunosuppressive Tumor Microenvironment in Colorectal Cancer? Assessment of the Association of the Expression of YKL-40, MMP-8, IL17A, and PD-L1 with Coexisting Type 2 Diabetes, Obesity, and Active Smoking

The influence of chitinase-3-like protein 1 (YKL-40 or CHI3L1) expression on the immunological properties of the tumor microenvironment, which may affect the effectiveness of immunotherapy, is currently not sufficiently understood in colorectal cancer (CRC). The aim of this study was to investigate the relationship between YKL-40 expression and the immunological properties of the tumor microenvironment in CRC. We performed in silico analysis, including analysis of immune cell infiltration scores and the immune landscape depending on YKL-40 expression, gene set enrichment analysis (GSEA), and analysis of three Gene Expression Omnibus (GEO) datasets. In 48 CRC tissue homogenates and the surgical margin, we analyzed the expression of YKL-40, MMP8, IL17A, and PD-L1. Moreover, we analyzed the expression of YKL-40 in tissue homogenates retrieved from patients with coexisting diabetes, obesity, and smoking. The expression of YKL-40 was significantly higher in CRC tumor tissue compared to healthy tissue and correlated with MMP-8, IL17A, and PD-L1 expression. In silico analysis revealed an association of YKL-40 with disease recurrence, and GSEA revealed a potential link between elevated YKL-40 expression and immunosuppressive properties of the tumor microenvironment in CRC.