CRM1/XPO1-FOXO1 Pathway Is Associated with Clinical Outcome and Represents a Promising Target in B-Cell Acute Lymphocytic Leukemia

Background:

Currently, a proportion of B-Cell Acute Lymphocytic Leukemia (B-ALL) patients still show no response to existing therapeutic drugs and existing therapeutic drugs cannot further improve the prognosis of refractory and relapsed B-ALL. Thus, the development of a new therapeutic target to battle this deadly disease is imperative. Exportin-1 (XPO1), also known as chromosomal region maintenance 1(CRM1), plays an important role in the progression of tumorigenesis. However, the prognostic and therapeutic values of XPO1 in B-ALL have not been reported.

Methods:

The difference in XPO1 and Foxo1 expression between normal B cells and leukemia cells was using the Human Protein Atlas (HPA) dataset and RT-qPCR results. Correlations between XPO1 expression level and clinical outcome were analyzed using the RNA-seq data of 110 newly diagnosed B−ALL patients in Nanfang Hospital. Cell proliferation assays, apoptosis assays, and cell cycle analysis were performed to analyze the anti-tumor effects of selinexor (KPT-330) in vitro. Bioinformatics analysis, western blot, and RT-qPCR were performed to explore the underlying mechanism.

Results ：

Higher XPO1 levels or Foxo1 levels were associated with poor prognosis in newly diagnosed B-ALL patients. Using bone marrow (BM)， peripheral blood (PB) cells from B-ALL and normal people as well as B-ALL cell lines, we found that XPO1 and Foxo1 expression was significantly increased in B-ALL patients and B-ALL cell lines. And notably, there was a positive correlation between the expression of Foxo1 and XPO1, which was verified by the data in the HPA database, and the results were consistent. Foxo1 is an important transcription factor in B-ALL, mainly localized in the nucleus, and is important for leukemia cell survival. KPT-330 (Selinexor), a selective Inhibitor of XPO1, mechanistically inhibited the expression of Foxo1, a leukemia transcription factor (reduced in both the nuclear and cytoplasmic compartments), and led to a strong repression of Foxo1 target genes associated with cell cycle, DNA replication, and transcriptional regulation. This induced growth inhibition, apoptosis, and cycle arrest in B-ALL cells. Moreover, in combination with Foxo1 Inhibitor (AS1842856), the proliferation inhibition and apoptosis-inducing effects of KPT-330 on B-ALL could be significantly enhanced. Furthermore, the KPT-330 strongly triggered apoptosis in leukemic but with minimal effects on normal cells implying that drugs of this class show promise for the targeted therapy of B-ALL leukemia cells.

Conclusions:

Our findings demonstrate that XPO1 is a promising prognostic indicator and a valid target for antitumor treatment with selective inhibitor KPT-330.

This research was supported by the National Natural Science Foundation of China(NFSC82170163, 81970147), Clinical Study of Nanfang Hospital(LC2016ZD009/2019CR012).