As in vitro analyses revealed lack of endogenous YKL-40 expression in other cancer cell lines, this notion provided reason to use them as the null background against which biological activities of YKL-40 have been examined, among them MDA-MB-231 and HCT-116 cells engineered to ectopically express YKL-40 [18]. The gene discussed is CHI3L1; the disease is cancer.