Human Acute Myeloid Leukemic Cells Research Articles

Abstract 264: Differentiation therapy: Esculetin as a potent agent to alter cellular plasticity of leukemic & solid tumor stem cells

Abstract Background The “Differentiation therapy” has been emerging as a promising and more effective strategy against acute leukemia relapses. Objective In extension to the revolutionising therapeutic outcomes of All Trans Retinoic Acid (ATRA) to induce terminal differentiation of Acute Promyelocytic Leukemic (APL) blast cells, we decipher the potential effect of a natural compound “Esculetin” to serve as a differentiating agent in Acute Myeloid Leukemia (AML) as well as solid tumour cells. Underlaying role of Wnt signaling pathways in esculetin mediated blast cell differentiation was also evaluated. Methods Human acute myeloid leukemic cells (Kasumi-1) with t(8;21/AML-ETO) translocation were used as a model system. Growth inhibitory and cytotoxic activity of esculetin were analysed using growth kinetics and MTT assay. Morphological alterations, cell scatter characteristics, NBT reduction assay and cell surface marker expression pat- terns were analysed to detect terminally differentiated phenotypes. We employed RT2profiler PCR array system for the analysis of transcriptome profile of Wnt signaling components. Calcium inhibitors (TMB8 and Amlodipine) and Transforming growth factor beta (TGF-β) were used to modulate the Wnt signaling axes. To investigate whether esculetin exerts the similar effects on the invasive solid tumour cancer stem cells subset, we used a cellular model system of colon carcinoma HCT116 cells reflecting EMT phenotype. Results We illustrate cytotoxic as well as blast cell differentiation potential of esculetin on Kasumi-1 cells. Morphological alterations akin to neutrophilic differentiation as well as the corresponding acquisition of myeloid lineage markers indicate terminal differentiation potential of esculetin in leukemic blast cells. Exposure to esculetin also resulted in downregulation of canonical Wnt axis while upto ~ 21 fold upregulation of non-canonical axis associated genes. Esculetin also showed potential to revert the CSC marker expressions and concurrent EMT consistent with reduced functional aggressiveness in colon cancer cells. Conclusions Our study highlights the importance of selective use of calcium pools as well as “axis shift” of the canonical to non-canonical Wnt signaling upon esculetin treatment which might abrogate the inherent proliferation to release maturation arrest and induce the differentiation in leukemic blast cells as well as CSC stem cells. The current findings provide further therapeutic interventions to consider esculetin as a potent differentiating agent to counteract relapses. Citation Format: Ankit Mathur, Daman Saluja. Differentiation therapy: Esculetin as a potent agent to alter cellular plasticity of leukemic & solid tumor stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 264.

Ceefourin-1, a MRP4/ABCC4 inhibitor, induces apoptosis in AML cells enhanced by histamine

BackgroundCeefourin-1 is a specific MRP4/ABCC4 inhibitor with potential antileukemic activity. In this study, we evaluate the ability of ceefourin-1 alone or in combination with histamine, an approved antileukemic agent, to induce cell differentiation or apoptosis in human acute myeloid leukemic cells. We also examine ceefourin-1 toxicity in mice. MethodsU937, HL-60, and KG1a cells were used as models for human acute myeloid leukemia. Cyclic AMP efflux was estimated by measuring intracellular and extracellular cAMP levels. Cell differentiation was assessed by levels of CD14 and CD11b by FACS, and CD88 by western blot, and by cell morphology. Apoptosis was evaluated by cleavage of caspase-3 and PARP by western blot, and by annexin V binding assay. Subacute toxicity study of ceefourin-1 was carried out in BALB/c mice. ResultsCeefourin-1 inhibits cAMP exclusion in AML cells and promotes intracellular signaling via CREB. Ceefourin-1 leads AML cells to apoptosis and histamine potentiates this effect, without evidence of cell differentiation. Intraperitoneal administration of ceefourin-1 shows no important alterations in mice blood parameters, hepatic, and renal functions, nor signs of histologic damage. ConclusionsThese results show that ceefourin-1 promotes apoptosis in AML cells that is enhanced by histamine.General significance:This work indicates that ceefourin-1 represents a promising molecule that could be used alone or in combination with histamine for in vivo evaluation in acute myeloid leukemia malignancies.

Disrupting Mitochondrial Electron Transfer Chain Complex I Decreases Immune Checkpoints in Murine and Human Acute Myeloid Leukemic Cells.

Simple SummaryDespite all of the advancements made in recent years in the treatment of acute myeloid leukemia (AML), long-term survival is achieved by only 30–40% of AML patients. Thus, new therapeutic strategies are strongly needed. This work confirms the increase in oxidative phosphorylation upon cytarabine resistance in AML murine cells, reinforcing the interest of targeting it. In addition, it identifies a new role of the first complex of the electron transport chain (ETCI) in the regulation of the immune checkpoints PD-L1 and CD39 in murine and human leukemic cells. Thus, this work opens the door to the evaluation of ETCI inhibitors in combination with immunotherapy.Oxidative metabolism is crucial for leukemic stem cell (LSC) function and drug resistance in acute myeloid leukemia (AML). Mitochondrial metabolism also affects the immune system and therefore the anti-tumor response. The modulation of oxidative phosphorylation (OxPHOS) has emerged as a promising approach to improve the therapy outcome for AML patients. However, the effect of mitochondrial inhibitors on the immune compartment in the context of AML is yet to be explored. Immune checkpoints such as ectonucleotidase CD39 and programmed dead ligand 1 (PD-L1) have been reported to be expressed in AML and linked to chemo-resistance and a poor prognosis. In the present study, we first demonstrated that a novel selective electron transfer chain complex (ETC) I inhibitor, EVT-701, decreased the OxPHOS metabolism of murine and human cytarabine (AraC)-resistant leukemic cell lines. Furthermore, we showed that while AraC induced an immune response regulation by increasing CD39 expression and by reinforcing the interferon-γ/PD-L1 axis, EVT-701 reduced CD39 and PD-L1 expression in vitro in a panel of both murine and human AML cell lines, especially upon AraC treatment. Altogether, this work uncovers a non-canonical function of ETCI in controlling CD39 and PD-L1 immune checkpoints, thereby improving the anti-tumor response in AML.

Gene therapy for acute myeloid leukemia using Sindbis vectors expressing a fusogenic membrane glycoprotein

AML has a dismal prognosis. It was previously shown that the expression of gene coding for the hyperfusogenic gibbon ape leukemia virus envelope glycoprotein (GALV.fus) can efficiently kill leukemic cells. However, target killing effect of GALV.fus on leukemia cells may be limited. Viral vectors, such as retroviruses and adenoviruses, have been developed to deliver heterologous genes into tumors in vivo, but these vectors have some limitations for gene therapy of leukemia. Another virus that has drawn interest as a gene transfer vector is the Sindbis virus. Sindbis virus efficiently infects human tumor cells through the high-affinity 67 kDa Laminin receptor. We found that Laminin-R was obviously expressed in HL-60 and primary human AML cells，but weakly expressed in K562 cells and blood samples of normal human. So we reasoned that Sindbis-virus-based vectors might be ideal for target gene transfer of GALV.fus to acute myeloid leukemic cell. It was shown that Sindbis virus efficiently transduced human acute myeloid leukemic cells with high expression of Laminin-R and exhibited potent cytopathic potential. What is more, we found that CFU-GMs were significantly reduced after Sindbis virus carrying GALV.fus transduced human primary AML cells. Sindbis virus carrying GALV.fus was active against human AML xenografts in vivo. Taken together, we concluded that Sindbis virus carrying GALV.fus may be an useful strategy for gene therapy of acute myeloid leukemia.

Inhibition of Elastase or SDF-1/CXCR4 Axis Promotes Differentiation of Human AML Cells.

Elastase, along with other azurophil granule proteins like proteinase 3 regulates normal and leukemic granulopoiesis in an un-defined mechanism. We have recently showed that human acute myeloid leukemic (AML) cells constitutively express and secrete stromal derived factor 1 (SDF-1) dependent cell surface elastase, which regulates their migration and proliferation. To elucidate the molecular events and genes regulated by elastase and SDF-1/CXCR4 axis in AML cells, we examined gene expression of U937 AML cell line treated with neutralizing anti-CXCR4 Abs or elastase inhibitor (EI) compared to untreated cells, using DNA microarray technology. Unsupervised hierarchical clustering analysis showed very similar gene expression profiles of EI and anti CXCR4 Abs treated cells as compared to control. 230 of 8400 genes interrogated were repressed, and 164 were induced after culturing AML cells in the presence of EI or anti CXCR4 Abs at different time points as compared to untreated cells. Inhibition of elastase or CXCR4 was accompanied by down regulation of the transcripts of primary granule proteins. Functional classification of elastase or SDF-1/CXCR4 axis regulated genes revealed downregulation of HOXA9, HOXA10, ETS2, as well as other transcription factors that are over expressed in AML and are important for the development of leukemia. Whereas, transcriptional factors and regulators known to be induced during myeloid differentiation like C/EBPε, ID1, RUNX3 and HHEX were up-regulated in treated cells. Expression patterns of apoptosis genes indicated decline in death control by the p53 dependent pathway and a more prominent control by mitochondrial mediated apoptotic pathway like bcl2 related genes. In addition, receptors for interleukins, growth factors (G-CSFR and GM-CSF), complement component (C1QR1) were upregulated in the treated cells. In contrast, FLT-3, a growth factor receptor stimulating growth of early progenitor cells and AML blasts, was down regulated in AML cell treated with EI or anti CXCR4 Abs. These data were confirmed by real time PCR for selected marker genes of granulocytic differentiation. Interestingly, many of the differentially expressed genes were common to the transcriptional program of normal terminal granulocytic differentiation (Theilgaard-Monch & Borregarrd 2005. Blood 105:1785) suggesting that inhibition of elastase may induce differentiation in AML cells. Thus we further analyzed the effect of elastase inhibition on AML cell differentiation and growth. Treatment of HL60 AML cell line with EI triggered a proliferative arrest, apoptosis and mimicked terminal granulocytic differentiation, including morphologic changes, increased CD11b expression, and the ability to produce oxidative bursts. In summary, our study showed that inhibition of elastase or SDF-1/CXCR4 axis in AML cells affects similar pathways related to differentiation and malignant transformation, implying a critical role for those molecules in regulating leukemic development. Repression of elastase decreases proliferation and induces differentiation of AML cells, suggesting a potential new therapeutic approach for AML.