FOS and neoplasm: Expression of SS-induced genes, such as Early growth response 1 (Egr1) [32], Activator protein 1 (Ap1) [33], Epithelial cell adhesion molecule (Epcam) [34], and Kruppel-like factor 8 (Klf8) [35], were the highest in the circulating GFP+ tumor cells (Fig. 1e and f).