CXCL17 and cancer: Because PDGF-BB has been implicated as being an oncogenic factor for metastasis in various cancers [26, 27], and CXCL17 provokes CD11b+Gr-1+ MDSCs to express high levels of PDGF-BB, we investigated the impact of CD11b+Gr-1+ MDSC-derived PDGF-BB in cancer extravasation, as determined by transendothelial migration analysis.