FLT1 and neoplasm: Using the in vivo models described in the previous paragraph, we found that VEGFR1 inactivation by treatment with anti-mouse VEGFR1-specific neutralizing antibody (MF-1) was as effective as IGF2-knockdown in retarding the rapid growth of Id1-shCON tumour (Fig. 5g) and reducing the percentage of VEGFR1+ cells in tumour xenografts (Supplementary Fig. 7).