The Expression of BTG1 in De Novo AML Patients Regulated By Demethylation of Decitabine and Its Evaluation in the Deep Remission of Patients

Background As an important hypomethylating agent, decitabine has shown promising efficacy in treating acute myeloid leukemia (AML), including de novo AML patients. However, as AML is a heterogeneous disease, not all de novo patients can benefit from decitabine. At present, there is a lack of large-scale clinical randomized controlled trials (RCTs) of AML treated with decitabine, and valuable molecular markers which are associated with decitabine-mediated hypomethylation and can predict the response to the drug in the treatment of AML have not been reported. This study aimed to identify molecular markers for predicting the response to decitabine.

BTG1 gene is a tumor suppressor gene and recently studies on BTG1 were mainly focused on lymphoma, lymphoblastic leukemia and solid tumor. But there are very limited researches on the role and clinical significance of BTG1 in AML. Therefore, we conducted innovative research on the relationship between BTG1 and demethylation mechanism in AML, and revealed the pathway and clinical significance of BTG1 in AML.

Methods An intersection of in vitro experiments and bioinformatics was performed using a combination of epigenetic and transcriptomic analysis. A tumor-suppressor gene associated with methylation, the response to decitabine, and mechanism of the gene were explored in vitro. The sensitivity and specificity of this gene in predicting the response to decitabine was confirmed in 60 samples from de novo AML patients treated with decitabine-containing regimen in our hospital from September 2020 to April 2024. In this study, patients with newly diagnosed AML (not APL) were eligible if they met the following inclusion criteria: (i) patients aged 14–60 years, or aged 14–65 if the Eastern Cooperative Oncology Group (ECOG) score was ≤ 2 points; (ii) patients with AML (not APL) who clearly met the WHO 2022 diagnostic criteria for AML; (iii) patients had not received chemotherapy. The exclusion criteria were as follows: (i) previous AML diagnosis; (ii) transformation of myelodysplastic syndrome (MDS) or other hematological diseases; (iii) central nervous system invasion; (iv) allergy to decitabine; (v) heart dysfunction (ejection fraction < 50%), liver dysfunction (total bilirubin > 34μmol/L), renal dysfunction (serum creatinine > 130μmol/L), history of severe infection.

Results In vitro experiments showed that BTG1 could be hypomethylated and regulated by decitabine, which was closely associated with the hypermethylation of the 3’UTR of BTG1 rather than the promoter. After decitabine treatment, a decrease in BTG1 3’UTR methylation and an increase in BTG1 gene expression were found, indicating that hypermethylation of BTG1 3’UTR may regulate the BTG1 gene expression. In addition to 3’UTR hypomethylation, BTG1 can also be upregulated by the pathway of DNMT1-FOXO3a-BTG1. Besides, Wnt/β-catenin signal pathway might be the downstream mechanism of BTG1, which could regulate BTG1 to affect cell proliferation and apoptosis.

In de novo AML patients who received decitabine-containing regimen, the BTG1 expression before treatment in patients with CR was lower than that with non-CR, and BTG1 expression before treatment in patients with MRD negativity was lower than that in patients with MRD positivity. Among 60 AML patients treated with decitabine-containing regimen, the sensitivity and specificity of newly treated BTG1 expression to predict the outcome after the first course of treatment were analyzed by ROC curve. The predictive value of BTG1 to predict complete remission (CR) was assigned with a sensitivity of 84.0% and a specificity of 80.0% when BTG1 expression was<0.64 (determined using real-time quantitative PCR), with area under the curve (AUC)=0.833, P<0.01. The predictive value of BTG1 to predict measurable residual disease (MRD) negativity was assigned with a sensitivity of 92.9% and a specificity of 60.9% when BTG1 expression was<0.5276 (AUC=0.756, P<0.01).

Conclusion The expression of BTG1 was found to be closely related to changes in DNA methylation density, which was regulated by demethylation of decitabine. The mRNA expression level of BTG1 in peripheral blood of de novo AML patients could predict the deep remission after treatment with decitabine. All of the above indicated that BTG1 might be a promising molecular marker for optimization of individualized treatment in AML.