Further support for the concept that Poly(I:C) inhibits melanoma metastasis, at least in part, by its ability to inhibit the production of Chi3l1 comes from studies comparing the inhibitory effects of Poly(I:C) in mice in which Chi3l1 is regulated normally and mice in which Chi3l1/YKL-40 is expressed solely in the lung (Chi3l1 Tg) using a Poly(I:C)-insensitive promoter (data not shown)25, 26, 27. This evidence concerns the gene CHI3L1 and melanoma.