VEGFA and cancer: Angiogenesis is a critical process for cancer metastasis [32–34], and M2 macrophages have been reported to facilitate cancer angiogenesis [35, 36], which were verified by our results that M2-CM promoted tube formation abilities in HUVECs, which were abrogated by both silencing VEGF in the M2-CM and deletion of VEGFR in HUVECs (Supplementary Figure S4A, B), suggesting that M2 macrophages secreted VEGF, which interacted with VEGFR to activate its downstream signals and eventually facilitate tumor angiogenesis.