RB1 and cancer: Given that Rb’s function is regulated by phosphorylation, and that Rb inactivation by hyper-phosphorylation is a frequent occurrence in human cancers [2,7,17–19] and in light of Rb’s role in cell adhesion, we postulated that there is a specific Rb phosphorylation signature that abrogates Rb ́s capacity to promote cell adhesion, and that such a phosphorylation signature could be a clinically informative biomarker for establishing metastatic potential based on a biopsy of a primary tumor.