RB1 and cancer: Interestingly, in both SCLC and neuroblastoma, cyclin-dependent kinase–interacting protein/kinase inhibitory protein (CIP/KIP) p21 is upregulated in the low-NE-score lines whereas another CIP/KIP p27 is downregulated, suggesting that the NE state–specific cell-cycle regulators are still consistent in these two cancer types despite differences in the upstream Rb loss.