However, as zTGF-β1 is highly homologous to higher vertebrates (Additional file 1: Figure S1A) [29], the ligands may act cross species; host-derived zTGF-β may signal on human tumour cells, and tumour-cell-derived TGF-β may bind and activate TGF-β receptors on host zebrafish cells (Additional file 1: Figure S1B-D). This evidence concerns the gene TGFB1 and neoplasm.