RB1 and retinoblastoma: Principal Component Analysis (PCA) revealed clear transcriptional distinctions between MYCN-overexpressing samples (MYCNO/E-RBOs and MYCNO/E-cells) and controls (nROs and Y79 cells), indicating that MYCN overexpression drives a unique transcriptional program distinct from both normal retinal development and RB1-deficient retinoblastoma (Figure 3A).