KDR and neoplasm: Acquired resistance is classified as the progression of tumor after initial tumor regression during the therapy, which is often driven by the development of other pathways stimulating angiogenesis, such as AXL, MET, and PDGF/PDGFR, and thus the escape of cancer cells from VEGF/VEGFR blockade (Crawford et al., 2009; Zhou et al., 2016).