MMP9 and breast cancer: This notion prompted Libreros et al. to hypothesize that the beneficial effects of chitin treatment in tumor models could originate from its interaction with CHI3L1.114 It was found that the intraperitoneal application of chitin microparticles to mammary tumor-bearing mice resulted in a downregulation of the pro-inflammatory mediators C-chemokine ligand 2 (CCL2), CXC motif chemokine ligand 2 (CXCL2) and matrix metalloproteinase 9 (MMP-9), whereas the production of interferon γ was markedly increased.