The reconstructed network (Figure 3) includes more than 20% (36 out of 168) of the identified cancer stem cell-specific genes that, inter alia, provide a sufficient positive feedback to keep the system active (Supplementary Table S2): Nt5e, Acpp, Pde4d, Pde7b, Igf1, Igf2, Pf4, Gpha2, Prok2, Nts, Wnt5a, Nppa, Adrb3, Fgfr1, Gpr97, Gpr128, Cacna1d, Cp, Pdk4, Riiad1, Trpv4, Abca1, Cd200, Gata6, Amy1, Nfatc2. This evidence concerns the gene PDE4D and cancer.