FLT1 and neoplasm: VEGFR is expressed in various immune cells, and VEGF can reduce effector T cell activity by directly binding to VEGFR1 or VEGFR2, mediating the infiltration of TAMs and MDSCs in tumor tissues, and increasing CD8+ T cells PD-1 and PD-L1 in DCs to inhibit their antitumor activity [124,125].