FLI1 and neoplasm: Because the vessels of the Tg (fli1: EGFP) zebrafish could glow with a green fluorescence, we found that the number of new formed twisty tumour vessels in the zebrafish injected with 231-lenti-ACE2 cells was less than that found in the zebrafish injected with 231-lenti-Vec cells (Fig. 4c).