In contrast to the above studies, it was shown that differentiated Rb−/−; p107+/−; p130−/− horizontal interneurons re-entered the cell cycle, clonally expanded, and formed metastatic retinoblastoma in mice45, indicating that the role of Rb in cell cycle control and survival is context-dependent and region-dependent, and there is functional crosstalk among the three pocket proteins. This evidence concerns the gene RB1 and retinoblastoma.