A new study on cancer research in zebrafish was published in September 2013. Rian Hanan et al looked into the ERK2 pathway and concluded that constitutive activation of this pathway leads to enhanced proliferation. Zebrafish models are commonly used to study developmental biology. As pathology and molecular mechanisms of tumor formation between humans and zebrafish are similar, zebrafish cancer models are very valuable for a better understanding of pathogenesis.
In human and zebrafish tumors the ERK signalling pathway, which is essential for vertebrate development, is frequently deregulated. Previously, the researchers demonstrated that ERK2 is crucial for cell migration and early zebrafish embryogenesis. In this new study they looked further into the ERK2 function. The researchers generated constitutively active mutant forms of the ERK proteins by introducing conserved point mutations. They validated the enhanced protein activity in vitro by transfection of constructs into zebrafish fibroblast (zf4) cells and established elevated phosphorylation levels of downstream targets P90RSK and CREB. Using the PamGene platform for kinase activity profiling new targets were identified in embryos injected with FGF8 or ERK2 mRNAs. The researchers detected both FGF8 specific and common signalling targets. Interestingly, with both mRNAs they found increased phosphorylation levels of CDK1, which is critical for proper G2/M phase transition and mitotic entry in proliferation control. These results point out that constitutive activation of the ERK2 pathway leads to enhanced, possibly oncogenic, proliferation.