A further interesting example is Roundabout, Axon Guidance Receptor, Homolog 1 (ROBO1) whose expression is implicated in several tumors of the nervous system: a low expression of ROBO1 is related to brain metastasis indicating a poor prognosis, whereas a high expression is common in gliomas [36, 37]. This evidence concerns the gene ROBO1 and central nervous system cancer.