Gene expression analysis of a retinoblastoma tumor suppressor/E2F signature in breast cancer. (Left) The intrinsic subtypes of breast cancer were defined based on conventional gene expression properties. Luminal (Lum)B and basal cancers are characterized by elevated expression of retinoblastoma tumor suppressor (RB)/E2F-regulated genes (highlighted with bracket). The tumors exhibit deregulation of RB/E2F-regulated genes as shown by specific analysis of an RB signature. (Right) The relative level of the RB signature was evaluated across five breast cancer subtypes. Data demonstrate the high levels of pathway deregulation in luminal B, basal, and Her2-positive cancers that have intrinsic poor prognosis.