Aberrant methylation and silencing of the SPINT2 gene in high‐grade gliomas

Abstract

Hepatocyte growth factor activator inhibitor type 2 (HAI‐2), encoded by the SPINT2 gene, is a membrane‐anchored protein that inhibits proteases involved in the activation of hepatocyte growth factor (HGF), a ligand of MET receptor. Epigenetic silencing of the SPINT2 gene has been reported in a human glioblastoma cell line (U87) and glioblastoma‐derived cancer stem cells. However, the incidence of SPINT2 methylation in tumor tissues obtained from glioma patients is unknown. In this study, we analyzed the methylation status of the SPINT2 gene of eight human glioblastoma cell lines and surgically resected glioma tissues of different grades (II, III, and IV) by bisulfite sequence analysis and methylation‐specific PCR. Most glioblastoma lines (7/8) showed methylation of the SPINT2 gene with a significantly reduced level of SPINT2 mRNA compared to cultured astrocytes and normal brain tissues. However, all glioblastoma lines expressed mRNA for HGF activator (HGFAC), a target protease of HAI‐2/SPINT2. Forced expression of SPINT2 reduced MET phosphorylation of U87 glioblastoma cells both in vitro and in intracranial xenografts in nude mice. Methylation‐specific PCR analysis of the resected glioma tissues indicated notable methylation of the SPINT2 gene in 33.3% (2/6), 71.4% (10/14), and 74.3% (26/35) of grade II, III, and IV gliomas, respectively. Analysis of RNA sequencing data in a public database indicated an increased HGFAC/SPINT2 expression ratio in high‐grade compared to low‐grade gliomas (P = .01). In summary, aberrant methylation of the SPINT2 gene is frequently observed in high‐grade gliomas and might confer MET signaling in the glioma cells.

MET in glioma: signaling pathways and targeted therapies

“…Regarding dysregulation of the HGF/MET signaling pathway, the SPINT2 gene has been extensively studied in gliomas. It encodes hepatocyte growth factor activator inhibitor type 2 (HAI-2), which is a membrane-anchored protein and a serine proteinase inhibitor that hinders proteases involved in the activation of HGF [48]. In human gliomas, HAI-2 expression levels are inversely correlated with histological grade, and reduced expression was found to be associated with progression [49].…”

“…In human gliomas, HAI-2 expression levels are inversely correlated with histological grade, and reduced expression was found to be associated with progression [49]. Moreover, in high-grade glioma, higher SPINT2 expression was determined to be associated with better OS [48]. Basic experimental research also showed that MET phosphorylation levels and glioblastoma tumor growth are reduced by the expression of HAI-2 both in vitro and in intracranial xenografts in nude mice, and that HAI-2 suppresses fibrinolytic activities and inhibits the Matrigel invasion of glioblastoma cell lines [48, 49].…”

“…Moreover, in high-grade glioma, higher SPINT2 expression was determined to be associated with better OS [48]. Basic experimental research also showed that MET phosphorylation levels and glioblastoma tumor growth are reduced by the expression of HAI-2 both in vitro and in intracranial xenografts in nude mice, and that HAI-2 suppresses fibrinolytic activities and inhibits the Matrigel invasion of glioblastoma cell lines [48, 49]. Therefore, these results implied that the downregulation of HAI-2 expression contributes to the progression of glioblastoma through activation of the MET signaling pathway.…”

Hepatocyte Growth Factor Activator: A Proteinase Linking Tissue Injury with Repair

“…Thus, HAI-2/SPINT2 may not be a physiological inhibitor of serum HGFAC. On the other hand, HAI-2/SPINT2 may function as an HGFAC inhibitor to suppress HGF-MET signaling in cancer tissues [ 44 ]. Further studies are required to define the roles of HAI-2/SPINT2 in HGF-MET signaling in vivo.…”

SPINT2 is hypermethylated in both IDH1 mutated and wild-type glioblastomas, and exerts tumor suppression via reduction of c-Met activation

“…Lee and colleagues [31] examined SPINT2 promoter hypermethylation in GBMs and GSC lines and observed associated reductions in SPINT2 mRNA expression in GSC lines; they similarly demonstrated reduced cell growth and migration following forced SPINT2 expression in U87 cells. A study published as this manuscript was being prepared also identified hypermethylation of the SPINT2 gene in human glioma-derived cell lines and high-grade glioma tissue samples [38].…”