PRDX1 depletion predisposes to ferroptosis through inhibiting the cAMP pathway in B-cell acute lymphoblastic leukemia.

Obesity Attenuates T-Cell Function Which Impacts the Efficacy of T-Cell Based Immunotherapies in Acute Lymphoblastic Leukemia

Tumor Associated Macrophages Express High-Levels of FLT3 Ligand, Which Induces Activation of FLT3 Signaling That Promotes Survival of Neoplastic Cells in B-Cell Acute Lymphoblastic Leukemia

Mitochondrial dsRNA from B-Precursor Acute Lymphoblastic Leukemia Cells Induce Formation of Cancer Associated Fibroblast in the Bone Marrow Leading to Formation of a Chemoprotective Bone Marrow Niche

Breakpoint cluster region-Abelson (BCR::ABL1) gene fusion is an essential oncogene in both chronic myeloid leukemia (CML) and Philadelphia-positive (Ph+) B-cell acute lymphoblastic leukemia (B-ALL). While tyrosine kinase inhibitors (TKIs) are effective in up to 95% of CML patients, 50% of Ph+ B-ALL cases do not respond to treatment or relapse. This calls for new therapeutic approaches for Ph+ B-ALL. Previous studies have shown that inhibitors of the thioredoxin (TXN) system exert antileukemic activity against B-ALL cells, particularly in combination with other drugs. Here, we present that peroxiredoxin-1 (PRDX1), one of the enzymes of the TXN system, is upregulated in Ph+ lymphoid as compared to Ph+ myeloid cells. PRDX1 knockout negatively affects the viability of Ph+ B-ALL cells and sensitizes them to TKIs. Analysis of global gene expression changes in imatinib-treated, PRDX1-deficient cells revealed that the nonhomologous end-joining (NHEJ) DNA repair is a novel vulnerability of Ph+ B-ALL cells. Accordingly, PRDX1-deficient Ph+ B-ALL cells were susceptible to NHEJ inhibitors. Finally, we demonstrated the potent efficacy of a novel combination of TKIs, TXN inhibitors, and NHEJ inhibitors against Ph+ B-ALL cell lines and primary cells, which can be further investigated as a potential therapeutic approach for the treatment of Ph+ B-ALL.

Identification of BCL6 As Synthetic Lethality in RAS-Driven B-Cell Transformation

The Role of Mitochondrial RNA from B-Precursor Acute Lymphoblastic Leukaemia Cells in Generating a Chemoprotective Bone Marrow Niche

STAT5-Feedback Controls Distinct Metabolic States for Dynamic Transitions between Cellular Activation and Quiescence in Acute Lymphoblastic Leukemia

CXCR4 inhibitors Plerixafor (small molecule) and BKT140 (peptide) interfere with CXCR4 activation, signaling and bone marrow homing of leukemia cells. Adhesion of B-ALL cells to bone marrow stromal cells (BMSC) through CXCR4/CXCL12 protects leukemia cells from cytotoxic drugs, and causes cell adhesion-mediated drug resistance (CAM-DR). Due to the critical role of the CXCR4/CXCL12 axis in B-ALL cell adhesion to bone marrow stromal cells (BMSC), we hypothesize that targeting CXCR4 will attenuate CAM-DR in B-ALL. All tested B-ALL cell lines and xenografts were found to be positive for surface expression of CXCR4, using 12G5 mAbs. Pre-treatment with Plerixafor (10μg/ml) or BKT140 (10μg/ml) significantly inhibited the spontaneous migration of B-ALL cells beneath BMSCs in vitro (Pseudoemperipolesis/PEP) to levels that were 61.4 ± 3.3% or 53.2 ± 5.6%, of respective controls (mean ± SEM, p<0.05). B-ALL cell line and xenograft B-ALL cell chemotaxis towards CXCL12 (100ng/ml) was also abrogated by pre-incubation with 10μg/ml Plerixafor (mean ± SEM, 26.7 ± 4.9% of control, p<0.05) and 10μg/ml BKT140 (mean ± SEM, 18.3 ± 4.7% of control, p<0.05). In order to better dissect CXCR4 function in B-ALL, we established two CXCR4 knock out cell lines, TANOUE-CXCR4-KO and NALM6-CXCR4-KO, using Zinc Finger Nuclease and CRISPR Cas9 technologies respectively. Chemotaxis to 100ng/ml CXCL12 and PEP beneath BMSCs for TANOUE-CXCR4-KO was 10.3 ± 0.48%, n=3 (p<0.05) and 50.06 ± 2.5%, n=4 (p<0.05) respectively, in comparison to TANOUE wild type control without any drug treatment. For NALM6-CXCR4-KO chemotaxis and PEP was 43.1%, n=1 and 41.8 ± 1.9%, n=4 (p<0.05) respectively in comparison to NALM6 wild type control without any drug treatment. CAM-DR experiments with ICN12 xenograft-BMSC co-culture showed significantly enhanced cytotoxicity when cells were treated with a combination of 100nM Dexamethasone (DEX) and 10μg/ml Plerixafor (66.1 ± 5.6% viability, n=3, p<0.05) or 10μg/ml BKT140 (59.7 ± 6.07% viability, n=3, p<0.05) as compared to DEX alone (87.3 ± 2.6% viability) at 48 hours. Similarly, pre-incubation of NALM6 cells with 10μg/ml Plerixafor/BKT140 showed significantly enhanced cytotoxicity (57.93±3.26%, n=3, p<0.05 and 54.2±3.26%, n=3, p<0.05 respectively) in comparison to DEX alone (72.38±0.25%, n=3). BMSCs rescued NALM6 cells from DEX induced cytotoxicity but failed to rescue NALM6-CXCR4-KO cells indicating that CXCR4 is the central mechanism used by stromal cells to provide drug resistance to ALL cells. Collectively, these findings provide a rationale for clinical targeting of CXCR4 in patients with B-ALL. Citation Format: Shubhchintan Randhawa, Dipanjan Ghosh, Amnon Peled, Richard E. Davis, Jan A. Burger. Targeting the CXCR4 chemokine receptor thwarts stromal cell mediated drug resistance in B-cell acute lymphoblastic leukemia (B-ALL). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4881. doi:10.1158/1538-7445.AM2014-4881

PTEN Counter Balances mTORC1 and PI3K Activities to Maintain Metabolic Homeostasis of B-ALL

Reprogramming Leukemia Cells into Antigen Presenting Cells As a Novel Cancer Vaccination Immunotherapy

This study aims to identify differentially upregulated ligand-receptor interactions between B-ALL cells and exhausted CD8+ T cells and to develop a multivariate Cox regression model for predicting the overall survival of pediatric B-ALL patients based on CCL3/CCL4/CCL5 expression levels. Pediatric B cell-acute lymphoblastic leukemia (B-ALL) is a hematopoietic malignancy. T cell exhaustion has an important impact on the prognosis of leukemia. The interaction between tumor cells and T cells can influence the degree of T cell exhaustion. However, the effects of B-ALL cells on exhausted T cell subpopulations and how the interaction influences the prognosis of B-ALL patients remain unclear. Single-cell RNA sequencing (scRNA-Seq) data from pediatric B-ALL patients were downloaded from GEO. Cell interaction analysis identified ligand-receptor pairs between B-ALL cells and exhausted CD8+ T cell. To confirm the function of CCL3/CCL4/CCL5/CCR5 in prognosis prediction, quantitative real-time polymerase chain reaction (qRT-PCR) was employed. We further developed an innovative stratified model that integrates CCL3, CCL4, and CCL5 through multi-Cox regression. Clustering of scRNA-Seq data revealed an increased proportion of exhausted CD8+ T cells in relapsed B-ALL, especially terminal exhausted CD8+ T cells (CD8_Ex), with increased exhaustion and decreased proliferation scores. Moreover, the CCL3/CCL4/CCL5-CCR5 axis was upregulated in interactions between B-ALL cells and terminal CD8_Ex. Transcriptome data from 221 pediatric B-ALL samples revealed that high CCL3/CCL4/CCL5/CCR5 levels correlate with low overall survival (OS). A multivariate Cox regression model incorporating CCL3/CCL4/CCL5 predicted prognoses. Finally, a model based on the adult B-ALL patients from our center also accurately predicted prognoses. We report for the first time the crucial role of the CCL3/CCL4/CCL5-CCR5 axis in the differentiation of terminal exhausted CD8+ T cells in B-ALL. High expression of CCL3, CCL4, CCL5, and CCR5 correlates with poor prognosis in B-ALL, suggesting potential biomarkers and therapeutic targets.

Notch Signaling Controls Drug Response in B-Cell Acute Lymphoblastic Leukemia (B-ALL)

Tetraarsenic tetrasulfide triggers ROS-induced apoptosis and ferroptosis in B-cell acute lymphoblastic leukaemia by targeting HK2

Identification of ZNF217 As an Essential Oncogenic Gene in B-Cell Acute Lymphoblastic Leukemia By CRISPR/Cas9-Based Library Screening

<div>Abstract<p>Notch3 and Notch4 support survival of primary B-cell acute lymphoblastic leukemia (B-ALL) cells, suggesting a role for Notch signaling in drug response. Here we used <i>in vitro, in silico</i>, and <i>in vivo</i> mouse xenograft model-based approaches to define the role of the Notch pathway in B-ALL chemosensitivity. We observed significant Notch receptor and ligand expression in B-ALL primary cells and cell lines. Primary leukemia cells from high-risk patients overexpressed Notch3, Notch4, and Jagged2 while displaying a reduction in expression levels of Notch1-4 following chemotherapy. We then analyzed <i>in vitro</i> cell survival of B-ALL cells treated with conventional chemotherapeutic agents alone or in combination with Notch signaling inhibitors. Gamma-secretase inhibitors (GSI) and anti-Notch4 were all capable of potentiating drug-induced cell death in B-ALL cells by upregulating intracellular levels of reactive oxygen species, which in turn modulated mTOR, NF-κB, and ERK expression. In NOG-mouse-based xenograft models of B-ALL, co-administration of the Notch inhibitor GSI-XII with the chemotherapeutic agent Ara-C lowered bone marrow leukemic burden compared with DMSO or Ara-C alone, thus prolonging mouse survival. Overall, our results support the potential effectiveness of Notch inhibitors in patients with B-ALL.</p><p><b>Significance:</b> Inhibition of Notch signaling enhances the chemosensitivity of B-ALL cells, suggesting Notch inhibition as a potential therapeutic strategy to improve the outcome of patients with B-ALL.</p></div>