APEX1 Polymorphisms Affect Acute Myeloid Leukemia Risk, and Its Expression Is Involved in Cell Proliferation and Differentiation

Abstract

Introduction: The link between DNA repair gene polymorphisms and cancer susceptibility has gained significant attention. Thus, we investigated the impact of base excision repair (BER) gene polymorphisms on acute myeloid leukemia (AML) risk and pathogenesis.

Methods: In total, 106 patients with AML and 191 healthy controls were included in the study, wherein polymorphisms in four BER genes (APEX1, MUTYH, OGG1, and XRCC1) were examined.

Results: Notably, the APEX1-656 T>G polymorphism exhibited a significant association with AML risk in the recessive (TT vs. TG + GG) (p = 0.046) and co-dominant models (TT vs. GG) (p = 0.02). Assessing APEX1 expression levels, APEX1 expression was elevated in the bone marrow of patients with AML compared with that in controls (p = 0.02). Subsequently, we compared the percentages of CD34+ cells between the APEX1 high or low expression groups, revealing a significant difference (high vs. low = 29.9% vs. 11.5%, p = 0.01). Additionally, we observed reduced APEX1 expression in HL60 cells differentiated with all-trans retinoic acid (p < 0.001). We hypothesized that APEX1 expression could correlate with stemness and analyzed its expression in stem and differentiated cells.

Conclusions: In the GSE48558 dataset, AML cells and normal CD34+ cells expressed APEX1 at higher levels than did granulocytes (p < 0.01). Functional experiments revealed that APEX1 knockdown led to a reduction in AML cell proliferation. These findings indicated that APEX1 polymorphisms were a potential risk factor for AML and highlighted the important role of APEX1 in regulating AML cell differentiation and proliferation.

Keywords: acute myeloid leukemia; base excision repair; differentiation; expression; polymorphism.

FIGURE 1

Relative APEX1 mRNA expression levels in cell lines and patients. Relative APEX1 mRNA expression levels. in AML cell line (gray) and bone marrow mononuclear cells from non‐AML patients (white). *p < 0.05, **p < 0.01 (a). Relative APEX1 mRNA expression levels in bone marrow mononuclear cells. Comparison of APEX1 mRNA expression levels between AML and normal bone marrow. Asterisks indicate outliers (b). Comparison of percentage of CD34+ cells in APEX1 high and low patients (c).

FIGURE 2

Morphological changes and alteration in APEX1 expression level in differentiated HL60 cells. HL60 cells treated with 1 μM ATRA for 7 days and stained with Wright‐Giemsa stain to assess granulocytic differentiation on day 0 (a) and on day 7 in nontreated cells (b) and ATRA‐treated cells (c). The scale bar is 100 μm, with a magnification of ×200. Magnified view of the area enclosed by the square in Figure 2c (d). Time course of APEX1 mRNA expression level in differentiated HL60 (e) **p < 0.01.

FIGURE 3

Induction of APEX1 knockdown effect by Tet‐on system on HL60 Tet‐on shAPEX1#1 (a) and time‐dependent effects of knockdown of APEX1 on HL60 Tet‐on shAPEX1#1 cell proliferation (b). *p < 0.05.