In vitro studies and tumor models in mice have demonstrated that YKL-40 plays a role in several biological processes such as inflammation; angiogenesis, both independently and through stimulating vascular endothelial growth factor; apoptosis; cell proliferation and differentiation; and regulation of cancer cell growth and metastatic potential [10], [13]–[15], [42], [43], all hallmarks of cancer as described by Hanahan et al [39]. The gene discussed is CHI3L1; the disease is cancer.