RB1 and glioblastoma: In addition, as a result of genomic profiling and the Cancer Genome Atlas Project [6], more than 600 genes were sequenced from more than 200 human tumor samples, which revealed the extremely complex genetic profile of GBM and established a set of three main signaling pathways that are commonly altered: the p53 pathway, the receptor tyrosine kinase/Ras/phosphoinositide 3-kinase signaling pathway and the retinoblastoma (Rb) pathway.