HIF1A and neoplasm: Moreover, in vivo reconstitution of MC38 tumours in HIF-1α KO mice with sVEGFR1 rescued the vascular phenotype and tumour growth (Fig. 4), whereas NK cell depletion of established tumours reduced sVEGFR1 levels, which led to non-productive angiogenesis and a decrease in tumour size (Fig. 5).