CXCL1 and neoplasm: CXCR2 ligands such as CXCL1, CXCL2, CXCL3, and CXCL5 are highly expressed in the tumor microenvironment of KRAS-mutant preclinical models [97–99], although their elevated secretion is often attributed to stromal or immune cells rather than direct production by KRAS-mutant tumor cells.