Hypermethylation of SOCS3 Affects the Prognosis of Children with Acute Lymphoblastic Leukemia and is Reversed by 5-aza-2′-deoxycytidine Through Inhibiting Cell Proliferation and Increasing Cell Apoptosis

Abstract

Background: Hypermethylation of the suppressor of cytokine signaling 3 (SOCS3) promoter has been found in most malignant tumors, but the correlation between acute lymphoblastic leukemia (ALL) and SOCS3 methylation has rarely been explored. Here, we mainly explored the role of SOCS3 methylation in ALL disease progression. Methods: Children with ALL were divided into low-level and high-level groups according to the methylation level of the SOCS3 gene. The logistic regression model was used to analyze the relationship between SOCS3 gene methylation level and the prognosis of ALL. Kaplan-Meier analysis was employed to assess overall survival (OS) and cumulative incidence of relapse (CIR). Bisulfite sequencing polymerase chain reaction (PCR) and flow cytometry were used to detect the changes in methylation level of the SOCS3 gene, and analyze the cell cycle and apoptosis in ALL cell lines before and after treatment with a methylase inhibitor. The Cell Counting Kit-8 assay and western blotting were used to detect the changes in cell proliferation and the protein expression levels of SOCS3, cleaved caspase-3, and p53 upregulated modulator of apoptosis (PUMA). Results: The methylation rate of the SOCS3 gene was 20.7% in the newly diagnosed group, 31.0% in the relapse group, 15.0% in the complete remission group, and almost nonexistent in the control group. Univariate Cox regression analysis showed that the high level of SOCS3 gene methylation was significantly associated with OS. The CIR in the high level group was significantly higher than that in the low-level group. After demethylation treatment, SOCS3 gene expression was significantly upregulated in ALL cells. Demethylation significantly inhibited the proliferation and arrested the cell cycle in the gap (G)0/G1 phase of ALL cells. SOCS3 demethylation may promote cell apoptosis by inducing the expression of apoptosis-related proteins such as cleaved caspase 3 and PUMA. Conclusions: The results of our study indicate that the level of SOCS3 methylation differs in patients with different stages of ALL, and is related to the relapse rate. SOCS3 methylation can be used as one of the early diagnostic and prognostic indicators of ALL. In ALL cells, SOCS3 demethylation significantly inhibited cell proliferation and viability. Thus, regulating the methylation status of SOCS3 gene may provide a new approach for the treatment of ALL. Clinical Trial Registration: This trial is registered with the Chinese Clinical Trial Registry, ChiCTR-IPR-14005706.