CXCL9 and neoplasm: Since the NH2-terminal amino acid sequences of the human IFN-induced chemokines CXCL9, CXCL10, and CXCL11 all contain this DPP4 cleavage-sensitive sequence (Figure 4B), it is possible that DPP4 expressed in the tumor microenvironment has a significant impact on the differential anti-tumor effects of IFN-induced chemokines, as reported in previous studies [26,27,28,29,30,31,32].