Moreover, YKL-40 is secreted in vitro by numerous human cancer cell lines of various origins, including glioblastoma, ovarian cancer, prostate cancer, osteosarcoma, and malignant melanoma [27,28,29,30], and the elevated serum level of YKL-40 is suggested to be an indicator and reliable biomarker of poor prognosis in advanced cancer patients. It was also shown that YKL-40 expression is upregulated in colon cancer cells and has a significant correlation with macrophage infiltration and microvessel density in the tumors of colorectal cancer patients and in a xenograft mouse model [31]. This evidence concerns the gene CHI3L1 and cancer.