Upregulation of HLA-E Drives Defective Natural Killer Cell Targeting in Venetoclax-Resistant Acute Myeloid Leukemia
Transplantation and Cellular Therapy(2024)
摘要
Acute myeloid leukemia (AML) is the most common leukemia in adults and is primarily diagnosed in older patients. The combination of the BCL2 inhibitor, venetoclax, with a hypomethylating agent has recently become standard of care front-line therapy for patients who are not able to tolerate high intensity induction chemotherapy and allogeneic stem cell transplantation. However, a significant number of patients experience disease refractoriness/relapse and second line treatment options are limited in efficacy. Natural killer (NK) cells have been shown to have potent anti-tumor effects in hematologic malignancies and may represent a potential therapeutic option for AML patients with progression after venetoclax-based therapy. Our group recently showed, however, that venetoclax-resistant (VR) AML blasts are less susceptible to NK cell-mediated killing (Figure 1), and the mechanisms underlying this phenomenon are not yet defined. HLA-E is a non-classical class I MHC molecule known to inhibit NK cell function through binding NKG2A/CD94 on the surface of NK cells. We hypothesized that defective NK cell killing in venetoclax-resistant AML could be mediated by upregulation of HLA-E on AML blasts.We investigated the sensitivity of AML blasts to NK cell cytotoxicity through in vitro co-culture assays with two different human AML cell lines and NK cells derived from a healthy human donor. We found that the venetoclax-resistant version of the OCI-AML-2 cell line was less susceptible to NK cell killing compared to the wild-type (WT) counterpart (Figure 1). In order to understand why VR AML blasts are resistant to NK cell-mediated killing, we investigated differences in NK cell ligands between WT and VR OCI-AML-2 cells and found that VR cells upregulated HLA-E (Figure 2). Given prior evidence showing that HLA-E upregulation in relapsed AML is mediated by interferon-γ, we stimulated WT AML blasts with interferon-γ and found that not only did this lead to upregulation of HLA-E, but it also led to decreased NK cell mediated lysis (Figure 3). We plan to conduct future studies examining the impact of inhibiting the JAK/STAT pathway in AML blasts and utilizing a blocking antibody against NKG2A and HLA-E to verify the role of HLA-E as a primary driver of defective NK cell killing. Overall, our findings suggest that the HLA-E and interferon-γ axis is a potential therapeutic target for enhancing NK cell responses in venetoclax-resistant AML.
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