The members of the RBL subgroup show more similarity in sequence with RB ancestral sequences than the members of the RB1 subgroup and represent more ancient functions of pRb signaling found to be associated with the control of quiescence and cell fate choice; additionally, pRb can also contribute to the development of tumor suppression via controlling all the aspects of cell cycle and coupling it with the processes of differentiation, cell senescence, and apoptosis [9]. This evidence concerns the gene RB1 and neoplasm.