ZIP10 (SLC39A10) Is an Important Transport Protein in Acute Myeloid Leukemia

Abstract

Introduction: Acute myeloid leukemia (AML) represents a challenging hematologic malignancy characterized by a high rate of relapse after initial remission and significant mortality. Despite improvements in understanding genetic and epigenetic drivers of AML progression, the impact of micronutrients such as zinc on disease pathogenesis remains poorly understood. Transport proteins, including ZIP10 (SLC39A10), play a crucial role in cellular zinc homeostasis and are implicated in various cellular processes critical for cancer biology, including proliferation and apoptosis resistance. A recent study highlighted zinc's potential role in enhancing immune reconstitution after allogeneic stem cell transplantation (Iovino et al., Blood, 2022). Hence, we sought to further investigate the relevance of zinc in AML pathogenesis. Methods: In this study, we employed a comprehensive approach utilizing AML cell lines (MV4-11, THP-1, NB-4) and samples obtained from AML patients at diagnosis or relapse (n=43). All patients provided written informed consent. The protocol was approved by the Ethics Committee at RWTH Aachen University Hospital (Germany) (EK 206/09; project #11-2022). All experiments were conducted in accordance with the Declaration of Helsinki. Cellular zinc levels were quantified using flame atomic absorption spectrometry. Gene expression of zinc transporters (ZIP1-ZIP14 and ZnT1-ZnT10) and metallothioneins (MT1/2) were analyzed by qRT-PCR. Additionally, cellular responses to zinc deficiency were evaluated by using the zinc chelator N,N,N′,N′-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN) or zinc-deficient medium (ZDM) generated by Chelex 100-treated RPMI 1640. The efficacy of zinc depletion was verified by comparing zinc concentrations in ZDM vs. untreated medium (0.066mg/l vs. 0.199mg/l, n=5; p=0.0001). Results: Patients were between 29 and 80 years old (19 female and 24 male). Our study revealed elevated protein-adapted zinc levels in peripheral blood (AML: n=6, Control: n=3; p=0.0069) and bone marrow (AML: n=8, Control: n=6; p=0.0215) from AML patients. RNA analysis of bone marrow cells demonstrated a significant upregulation of ZIP6 (SLC39A6) (p=0.0429), ZIP9 (SLC39A9) (p=0.0070), and ZIP10 (SLC39A10) (p=0.0171) in AML (AML: n=7, Control: n=6), whereas expression of MT1/2 was notably reduced (AML: n=10, Control: n=9; p=0.0253). This was accompanied by increased staining of free intracellular zinc in CD34+ AML blasts via the zinc-specific dye Zinpyr-1 (n=6; p=0.0488). An increased amount of the ZIP10 surface protein was observed by Western Blot analyses (AML: n=10, Control: n=9; p=0.0002) and immunohistochemical staining (n=3). In addition, overexpression of ZIP10 (SLC39A10) in AML was confirmed by data from the BeatAML2.0 (n=805) and Leukemia Mile (n=542) study. Functional studies showed impaired colony formation after treatment of AML cells for 72h under zinc deficient conditions via TPEN (n=5; p=0.0016) or ZDM (n=5; p=0.0443). Experiments with MV4-11, THP-1, and NB-4 cells demonstrated that zinc deficiency caused decreased cell proliferation and increased apoptosis in myeloid cell lines. Furthermore, ZDM impaired myeloid signaling after stimulation with G-CSF and improved differentiation of NB-4 cells. ZDM induced an upregulation of ZIP10 (SLC39A10) in MV4-11 (n=7; p=0.0438) and THP-1 (n=11; p=0.0207). Blocking the ZIP10 transporter with an anti-ZIP10 antibody led to decreased intracellular zinc levels in MV4-11 cells (n=11; p=0.0081) accompanied by a dose-dependent decrease in cell growth (n=13, p<0.0001) and cell viability (n=11, p<0.0001). Conclusions: Our findings underscore a critical role of zinc homeostasis, particularly as mediated by ZIP10, in AML pathogenesis. Dysregulated zinc metabolism, characterized by elevated zinc transporter expression and altered zinc storage mechanisms, appears to be essential to AML biology. Targeting the ZIP10 transporter, thereby reducing zinc uptake, offers further evidence that zinc modulation disrupts myeloid cell proliferation and increases apoptosis. These results suggest that blocking zinc transporters deserves being further investigated as a supplementary therapeutic approach in AML management and advocates further exploration of the role of zinc and other micronutrients in the progression of myeloid malignancies.