PCNA and neuroblastoma: Correspondingly, ATRA decreases cell viability (Figure 1E), stimulates expression of neuroblastoma differentiation markers (i.e., growth associated protein 43 (GAP43), neuron specific enolase (NSE) and β-TUBULIN III) [33-35], inhibits expression of cell proliferation markers (i.e., PCNA and Ki67), and increases expression of apoptosis markers (i.e., cleaved CASPASE 3 and PARP) (Figure 1F) in dose-dependent manners.