The synergistic effect of IDH mutation and NDRG-2 dysregulation in the progression of WHO-grade 4 astrocytomas.

BACKGROUND

NDRG2 is a tumour suppressor gene involved in tumor growth inhibition. Its effect on tumour recurrence remains controversial. The aim of this study is to explore the dual effect of IDH mutation and NDRG2 dysregulation in WHO-Grade 4 astrocytoma recurrence.

METHODS

A group of 36 patients with WHO-Grade 4 astrocytoma were examined for NDRG2 expression using protein and gene expression assays. The relationship between IDH, NDRG2 protein and gene expressions, and recurrence-free interval [RFI] was explored.

RESULTS

The mean patients age in this study was 45-years with 21 males and 15 females. IDH was mutant in 22 tumors. NDRG2 protein expression was low in 23 tumors, and high in 13 tumors. NDRG2 gene expression was upregulated in 4 tumors and 32 tumors showed NDRG2 gene downregulation. The consistency between two tasting methods of NDRG2 expression was 52.8%. There was a significant statistical difference in RFI among tumors with varying NDRG2 gene expression and IDH mutation [p-value= 0.021]. IDH-mutant tumours with downregulated NDRG2 expression showed late recurrence compared to IDH-wildtype glioblastoma.

CONCLUSIONS

IDH-mutant WHO Grade-4 astrocytoma with downregulated NDRG2 gene are associated with late tumor recurrence. IDH mutations cause excessive accumulation of D-2-hydroxyglutarate, that may inhibit the activity of TET proteins, potentially leading to DNA hypermethylation and gene silencing.