CHI3L1 and cancer: On the other hand, M2 macrophages contribute to immune evasion through the secretion of chitinase-3-like protein 1 (YKL-40) [92], a chitinase-like glycoprotein, widely reported to promote tumor angiogenesis, immune suppression, and malignancy across various cancers and associated with increased PD-L1 expression on tumor cells [93,94].