For example, one study investigated tumor initiation by optically activating caged Cyc to induce both transient and constitutive expression of a human oncogene kRASG12V in zebrafish, relying on the Gal4-ERT2/UAS and Cre-ERT2/loxP systems, respectively [214] (Figure 4C,D). This evidence concerns the gene MAPK3 and neoplasm.