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

## TL;DR

This study explores how the INSM1 gene contributes to aggressive neuroblastoma cancer and suggests that targeting INSM1 and its metabolic regulation could help treat the disease.

## Contribution

The study reveals that INSM1 sustains tumor cell immaturity through the methionine cycle and epigenetic regulation, offering new therapeutic strategies for neuroblastoma.

## Key findings

- INSM1 maintains an immature, stem-like state in neuroblastoma cells and is regulated by the methionine cycle and epigenetic changes.
- Retinoic acid reduces INSM1 and N-Myc, promoting cell differentiation and suggesting a potential treatment approach.
- INSM1 overexpression affects gene expression related to neuroendocrine differentiation and suppresses cell cycle and oncogenic genes.

## Abstract

Neuroblastoma (NB) is a childhood cancer that arises when certain nerve-related cells fail to mature properly and become malignant. Our study focuses on a gene called INSM1, which is normally active during early cell development but is abnormally elevated in NB tumors. We aimed to understand how INSM1 contributes to cancer’s aggressiveness and poor differentiation. We discovered that INSM1 keeps tumor cells in an immature, stem-like state and is closely linked to a chemical pathway called the methionine cycle, which affects gene regulation through epigenetic changes. Disrupting this cycle alters INSM1 activity and may help push cancer cells toward normal development. We also found that retinoic acid, a compound known to promote cell differentiation, reduces INSM1 and another cancer-driving gene, N-Myc. These findings suggest that targeting INSM1 and its metabolic regulation could be a promising strategy to treat NB by encouraging tumor cells to mature and lose their malignant properties. This research provides new insights into the biology of NB and may lead to more effective therapies for children affected by this disease.

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.