MMP9 and neoplasm: Specifically, using heterozygous zygotic knockout of Zeb1 (i.e. retaining one functional allele), it was shown that ZEB1 levels increase in peritoneal macrophages upon i.p. injection of ID8 cells, alongside myeloid-related genes including Ccr2. In ID8-linked TAMs, lowering ZEB1 levels proportionally decreased expression of these genes, of which MMP9 induced de-differentiation, proliferation and chemoresistance in tumor cells.