Figure 1.

Functional activities of YKL‐40/CHI3L1 in the tumor microenvironment. YKL‐40/CHI3L1, secreted by immune and nonimmune cells in the tumor microenvironment, promotes tumor progression through its downstream effects on multiple cell types, resulting in: neoplastic changes, mitogenesis, antiapoptosis, angiogenesis, proinflammatory molecule production, immunosuppression, leukocyte recruitment, invasion, and metastasis. MDSC, Myeloid‐derived suppressor cell; TIL, tumor‐infiltrating lymphocyte.