Loss‐of‐Function Aldolase C Hypermethylation Cause Serotonin Production in Glioblastoma

Abstract

Aldolase involves the glycolysis procedure to maintain glucose homeostasis and further produce some intermediates or energy synthesis. Aldolase C (ALDOC) is specific to the brain region and is activated when the brain develops, is injured or traumatized. Recently, we investigate that ALDOC had independent prognostic role in GBM, which was suppressed in low‐grade glioma and glioblastomas (GBM) and correlated with IDH1 mutant status, MGMT methylation and survival rate. We further found that ALDOC has CpG island in promoter region and was hypermethylated in GBM cells. We collected mRNA level and methylation state of ALDOC by RNA‐sequencing and bisulfite‐specific PCR from Cancer cell line encyclopedia (CCLE) database, respectively. The scatter plots performed the inverse correlation trends between methylation with expression level in GBM cells (n=39, spearman rho=−0.774, P=7.68e‐09). We further dissected the metabolomics pattern and compared with methylation status of ALDOC. The results showed serotonin as one of significant change in GBM cells, the production rate was increased when ALDOC hypermethylation or low expression level. Several malignant GBM cells treated 5‐aza‐2′‐deoxycytidine (5‐aza‐dC) to suppress DNA methyltransferase activity. We found that ALDOC expression levels were restored and migration/invasion ability was reduced. Similarly, the serotonin concentration has attenuated, depending on the ALDOC methylation status. We further computational analyzed the mRNA level of ALDOC correlated with IC50 of temozolomide (TMZ). T98G cells have been selected for ALDOC overexpression and the IC50 of TMZ is reduced by ALDOC induction. In contrast, we transfected shRNAs to knock down ALDOC expression levels in U‐87MG cells with an increase in IC50. The combination of selective serotonin inhibitor and 5‐aza treatment has a synergistic effect on IC50 of TMZ in GBM cells.