CHI3L2 and osteoarthritis: When superimposed with other eukaryotic CLPs, such as IDGF-2 (a growth factor that promotes cell proliferation in imaginal discs in Drosophila melanogaster) and human CHI3L2 (overexpressed in osteoarthritis, in glioblastoma, and in tumor-associated macrophages in breast cancer) (19, 20), AgBR1 showed a highly conserved core structure, while the most significant differences are found in the loops.