Impact of Selinexor on AML Cell Lines and Healthy Donor T Cell Function: Enhanced Treg Cell Proportion
Authors: Tong Xiwen , Zhu Xiaojian , Shuai Su , Zhu Yi , Xu Bin , Peng Yizhou , Zhang Shiyuan , Jie Jin , Mao Xia , Wei Jia , Zhang Donghua 
Published: December 2024

Introduction:

Selinexor is an oral, first-in-class selective inhibitor of nuclear export (SINE), specifically blocking XPO1. Selinexor has shown promising results in maintenance therapy for post-transplant AML and MDS . However, its specific impact on T cell function in post-transplant patients remains unclear. Therefore, this study conducted a series of investigations into the effects of selinexor on T cell function.

Methods:

Effects of selinexor on proliferation and apoptosis of four types of AML cells and FLT3-mutant AML cells detected by CCK-8 assay and flow cytometry. The cytotoxicity, exhaustion, degranulation, cytokine secretion, and phenotype of T cells pretreated with selinexor were detected by flow cytometry. The effects of selinexor on the gene expression profile of T cells were analyzed by RNA-seq.

Results:

Selinexor has different IC50 on four kinds of AML cell lines. The IC50 of selinexor was 32.0 nM in SKM-1, 26.0 nM in THP-1, 16.0 nM in Kasumi-1, and 33.0 nM in MV4-11 after 48 hours. As the selinexor concentration increased, the cell survival rate decreased, and proliferation was inhibited. As the duration of selinexor prolonged, the cell survival rate decreased. At the same drug concentration, the proportion of cell apoptosis significantly increases with longer treatment times. After 72 hours of drug treatment, the proportion of cell apoptosis significantly increases with higher drug concentrations.

The IC50 of selinexor was 522.7 nM in FLT3-mutant SKM-1 after 48 hours. Selinexor inhibits FLT3-mutant SKM-1 cell line proliferation with a pronounced concentration gradient effect. As for the apoptosis of FLT3-mutant SKM-1, at the same drug concentration, the apoptosis proportion increases with longer treatment times. At the same treatment duration (72 hours), apoptosis proportion increases with higher drug concentrations. At the same treatment duration (72 hours), selinexor exhibits a significantly stronger pro-apoptotic effect on FLT3-mutant SKM-1 cells compared to wild-type SKM-1 cells at different drug concentrations.

The IC50 of selinexor was 179.0 nM in human T cells after 48 hours. As the selinexor concentration increased, proliferation was inhibited. Selinexor affects apoptosis in T cells, with increasing drug concentration resulting in a higher proportion of T cells apoptosis. Similarly, at constant drug concentrations, prolonging the duration of selinexor also leads to a gradual increase in T cell apoptosis.

After treatment with high concentrations of selinexor (250 nM, 1 μM), for 72 hours, there was a significant increase in the proportion of Treg cells compared to untreated T cells (P＜0.05).

At the same drug concentration, as the effector-to-target (E: T) ratio increases, the cytotoxicity of T cells against target cells gradually increases, but without statistical significance (P＞0.05). At the same E: T ratio (10:1), T cells treated with high concentrations of the drug (2.5 μM, 5 μM, 10 μM) exhibited a significant decrease in their ability to induce apoptosis in target cells compared to the control group and there was no significant difference observed in cytotoxicity(P＜0.05).

At the same drug concentration, increasing the duration of selinexor treatment resulted in a slight increase in T cell degranulation (CD107a) levels, although the difference was not statistically significant (P＞0.05).

There were no significant differences in exhaustion markers (PD-1, Tim3, Lag-3) among T cells treated with different concentrations of selinexor for varying durations. Furthermore, when co-cultured with SKM-1 target cells, T cells treated with selinexor did not show significant differences in secretion of cytokines such as IL-2, TNF-α, IFN-γ, IL-4, IL-6, and IL-10 compared to the control group (P &gt; 0.05).

GO database enrichment analysis revealed that upregulated differentially expressed genes are predominantly enriched in categories such as negative regulation of lymphocyte activation, negative regulation of T cell activation, and negative regulation of the immune system process. This provides a mechanistic basis for the observed phenomenon of selinexor promoting an increase in Treg cell proportion in T cells.

Conclusion:

Selinexor inhibits proliferation and promotes apoptosis in AML cell lines. It also partially inhibits T cell proliferation, promotes apoptosis, and significantly increases the proportion of Treg cells.