ATP5IF1 and neoplasm: However, HeLa (CTR, expressing IF1) cell injection in zebrafish embryos at 2 days post-fertilization (dpf) caused a tumor mass development in the following days (6 dpf), which was not observed in the IF1 knock out (KO) HeLa-injected embryos, Fig. 1C, confirming an important role of IF1 expression in cancer development in vivo.