PGF and cancer: TAMs also enhance cancer stem cell-like properties of tumor cells (10) that promote invasive capability and metastasis of later stages cancers including formation of the pre-metastatic niche in secondary site, extravasation, and early colonization (11, 12) and favors angiogenesis by secreting proangiogenic factors including, placental growth factor (PIGF), TGF-β, CCL2, and CXCL12 (13–15).