C. L et al. confirmed that knockdown of VEGFR1 blocks macrophage recruitment into tumour tissue in a clear cell renal cell carcinoma xenograft model, indicating that VEGFR1, which is known to be expressed on monocytes and macrophages, induces macrophage recruitment by the VEGFR1/VEGF-A axis (Li et al., 2011). Here, FLT1 is linked to clear cell renal carcinoma.