Regulation of INSM1 Gene Expression and Neuroendocrine Differentiation in High-Risk Neuroblastoma

Neuroblastoma (NB), a pediatric cancer of sympatho-adrenal (SA) lineage, is marked by disrupted differentiation and cellular heterogeneity. INSM1, a zinc-finger transcription factor, is highly expressed in NB and developing SA tissues, where it regulates neuroendocrine differentiation, especially in chromaffin cells. We investigated INSM1's role in maintaining an undifferentiated, progenitor-like state in NB and its regulation via metabolic and epigenetic mechanisms. Transcriptomic profiling, promoter assays, and metabolic flux analysis revealed that INSM1 expression correlates with methionine cycle activity, particularly the S-adenosylmethionine (SAM)/S-adenosylhomocysteine (SAH) ratio. Disruption of SAM/SAH balance altered INSM1 promoter activity and histone methylation, implicating epigenetic control in NB cell fate. Retinoic acid-induced differentiation downregulated INSM1 and N-Myc, linking INSM1 to tumor cell immaturity. INSM1 overexpression in SH-SY-5Y cells upregulated neuroendocrine and thyroid hormone-related genes (CHGA, CHGB, DDC, NCAM1, DIO3, TH), while suppressing genes involved in cell cycle (RRM, CDC25A), methionine metabolism (AHCY, MAT2A), transcriptional regulation (MYBL2, EZH2), and oncogenic signaling (ALK, LINC011667). These findings suggest that INSM1 promotes NB aggressiveness by sustaining a neuroendocrine progenitor-like phenotype through metabolic-epigenetic coupling.