Interestingly, the gene expression analysis of tumor cells isolated from zebrafish (ZF-single and ZF-cluster) shows a differential profile between both tumor cell populations, and points towards an upregulation in CTC-clusters of genes involved in cell survival (PLAU), cell cycle regulation (CDK4 and E2F4), and in stemness (ITGA6 and CD44). The gene discussed is CDK4; the disease is neoplasm.