mutated in breast, colorectal, pancreatic cancers and glioblastoma (6–8). Furthermore, the pilot experiment from the Tumor Sequencing Project identified 26 genes (TSP-genes) mutated in lung adenocarcinoma (9). Altogether, these studies revealed that the number of cancer genes is surprisingly high and they are functionally more heterogeneous than previously thought. Despite this functional heterogeneity, cancer genes tend to share ‘systems-level properties’ (10), such as higher connectivity and lower duplicability when compared to the rest of human genes (11–13). The presence of shared properties, which are not strictly dependent on the gene function, indicates that cancer genes are fragile components of the human gene repertoire.
