M YCN Amplification Drives Ferroptosis Susceptibility via Cysteine Metabolism in Retinoblastoma

Purpose: This study aimed to evaluate whether MYCN amplification enhances ferroptosis susceptibility in retinoblastoma (RB) and to elucidate the key regulatory mechanisms. Methods: MYCN-amplified Y79 and MYCN copy-number gain WERI-RB1 cells were treated with ferroptosis inducers imidazole ketone erastin (IKE) and RSL3. MYCN was silenced using short hairpin RNA (shRNA) lentiviral transduction, followed by RNA sequencing, real-time quantitative PCR, and western blot. Amino acid deprivation and propargylglycine (PAG) treatment were applied to probe cysteine metabolic pathways. Glutathione (GSH), malondialdehyde (MDA), and ferrous iron (Fe2+) levels were measured, and ultrastructural changes were examined by transmission electron microscopy. An orthotopic xenograft model was used to assess the effect of IKE, PAG, and their combination on tumor growth. Results: MYCN amplification correlated with increased ferroptosis sensitivity, which was reduced by MYCN knockdown. Transcriptome analysis identified dysregulation of cysteine/methionine metabolism, with decreased xCT subunits and cystathionine γ-lyase (CTH) expression. PAG potentiated IKE-induced ferroptosis and triggered cell death alone, while MYCN depletion attenuated lipid peroxidation, restored GSH, and reduced Fe2+ accumulation. In vivo, IKE, PAG, and IKE+PAG all significantly inhibited intraocular tumor growth. Conclusions: MYCN promotes ferroptosis in RB via xCT and transsulfuration pathways. Targeting the MYCN-xCT-transsulfuration axis may offer a novel therapeutic approach for MYCN-amplified RB.