Interestingly, endogenously produced IGF-1Ec was found to induce cellular proliferation in human prostate cancer cells in vitro and in vivo by activating the ERK1/2 pathway, while tumors and cells overexpressing the Ec peptide of the IGF-1Ec isoform presented evidence of epithelial-to-mesenchymal transition [34,35]. The gene discussed is MAPK3; the disease is prostate cancer.