Since there is no forced overexpression of YKL-40 due to genetic manipulation of the tumor cells in the present study and immunohistochemical staining for human YKL-40 showed no visible difference in expression between the tumors of the anti-YKL-40 treated and the control group, the observed boost of tumor volume is probably due to a drastic increase in the effect of YKL-40. The gene discussed is CHI3L1; the disease is neoplasm.