Inhibition of Purine Metabolism Promotes the Differentiation of Neuroblastoma Driven by MYCN.

BACKGROUND: Neuroblastoma (NB), the common extracranial solid tumor in children, is associated with a poor prognosis, particularly in high-risk patients. MYCN amplification stands as the most prominent molecular hallmark within this high-risk subgroup. However, MYCN protein is considered "undruggable" due to its lack of a conventional enzymatic binding pocket and its predominant nuclear localization, which precludes targeting by standard small-molecule inhibitors or antibody-based therapeutics. Consequently, current therapeutic strategies have achieved limited efficacy against MYCN-driven NB. Notably, MYCN not only orchestrates diverse metabolic reprogramming pathways in tumors but also exerts a pivotal influence on cellular differentiation. To overcome this therapeutic barrier, we seek to elucidate the contribution of purine metabolism to stemness maintenance in MYCN-amplified NBs and to discover novel small-molecule inhibitors capable of inducing differentiation in high-risk NBs. METHODS: Metabolomic profiling via mass spectrometry was employed to delineate differential metabolite signatures between MYCN-amplified and non-amplified NB cells. Bioinformatics analysis of publicly available RNA sequencing datasets facilitated the systematic evaluation of purine metabolic enzyme expression. Cell differentiation, proliferation, colony formation, and cell migration assays were employed to assess the inhibitor's effects. Additionally, an in vivo xenograft model of NB was established to examine the therapeutic potential of lometrexol (LMX), a selective inhibitor of the purine biosynthesis enzyme phosphoribosylglycinamide formyltransferase (GART). RESULTS: Significant changes in nucleotide metabolism were identified in NB cell lines with high MYCN expression compared to those with low MYCN expression. The expression of purine metabolic enzyme genes was positively correlated with MYCN expression, prognosis, and differentiation status in NBs. Pharmacological inhibition of GART using LMX elicited a robust pro-differentiation response, concomitant with a significant suppression of tumorigenic potential. CONCLUSIONS: These findings establish purine metabolic enzyme inhibition as a viable therapeutic strategy to induce differentiation and attenuate tumor progression in high-risk MYCN-amplified NBs.