The zebrafish has become an important model for cancer research. Several cancer models have
been established by transgenic expression of human or mouse oncogenes in zebrafish. Since it is
amenable to efficient transgenesis, zebrafish have immense potential to be used for studying
interaction of oncogenes and pathways at the organismal level. Using the Gal4VP16-UAS binary
transgenic expression approach, we established stable transgenic lines expressing an EGFP fusion
protein of an activated zebrafish Smoothened (Smoa1-EGFP). Expression of the zebrafish Smoa1-EGFP itself did not lead to tumor formation either in founder fish or subsequent generations,
however, co-expressing a constitutively active human AKT1 resulted in several tumor types,
including spindle cell sarcoma, rhabdomyoma, ocular melanoma, astrocytoma, and myoxma. All
tumor types showed GFP expression and increased Patched 1 levels, suggesting involvement of
zebrafish Smoa1 in tumorigenesis. Immunofluorescence studies showed that tumors also expressed
elevated levels of phosphorylated AKT, indicating activation of the PI3K-AKT pathway. These
results suggest that co-activation of the hedgehog and AKT pathways promote tumorigenesis, and
that the binary transgenic approach is a useful tool for studying interaction of oncogenes and
oncogenic pathways in zebrafish
