Human Acute Lymphoblastic Leukemia Cells Research Articles

Enzymatic reaction and competitive prereduction enable label-free and separation-free inductively coupled plasma mass spectrometry detection of leukemia cells

The enzyme terminal deoxynucleotidyl transferase (TdT) exhibits significant activity in various leukemia cells, including human acute lymphoblastic leukemia cells (CCRF). It demonstrates substantial potential as a diagnostic biomarker for acute lymphoblastic leukemia (ALL). Herein, a highly sensitive method for the homogeneous quantification of TdT and CCRF cells, without the need for labeling or separation, was established based on inductively coupled plasma mass spectrometry (ICP-MS). The simple sensor relied on the TdT-induced polymerization process, lengthening the DNA strand and producing large amounts of the by-product phosphates of pyrophosphate (PPi). The PPi formed complexes with Cu²⁺, altering its morphology in homogeneous systems. The remaining Cu²⁺ competed with Hg²⁺ in consuming ascorbic acid (AA) through the pre-reduction of Hg²⁺, affecting the ICP-MS signal of Hg²⁺. Under optimal conditions, this approach exhibited excellent specificity and ultrahigh sensitivity, with limits of detection (LODs) as low as 0.05 U/L for TdT and 5 cells/mL for CCRF cells, respectively. The proposed method offers significant advantages, including high sensitivity and precision, operation at room temperature without the involvement of proteases, and the ability to accurately quantify in complex biological matrices. Consequently, the proposed method shows great promise as a valuable tool for TdT-related biological research and leukemia diagnosis.

Inhibitory effects of progesterone on the human acute lymphoblastic leukemia cell line

IntroductionAcute lymphoblastic leukemia (ALL) is a rare form of blood cancer that can quickly advance if left untreated. Research has suggested that progesterone (P4) may be effective in treating certain types of tumors. Specifically, the membrane progesterone receptors may play a role in either enhancing or inhibiting cell growth in various tumors. This study aimed to investigate the impact of P4 on inhibition of NALM6 cells. MethodsNALM6 cells were exposed to different concentrations of P4 (ranging from 10 to 50 μM) at 24,48 and 72 h intervals. The cell survival rate was then evaluated using an MTT assay. Additionally, the study assessed the rate of mPR expression in the cells using flow cytometry at 48 and 72 h after P4 administration (at concentrations of 20 and 10 μM, respectively). Furthermore, the level of ROS was evaluated using the dichlorofluorescein diacetate (DCFDA) flow cytometry technique. ResultsThe study found that mPR-β was expressed in NALM6 cells and that P4 had a significant inhibitory effect on the growth of tumor cells in a time and concentration-dependent manner. Furthermore, P4 was found to reduce mPR-β expression at 48 and 72 h. The treatment also resulted in a decrease in ROS levels compared to untreated cells (P ≤ 0.05). ConclusionThe study suggests that p4 may be effective in growth-inhibiting NALM6 cells by decreasing cell viability and reducing ROS levels. However, further research is needed to understand the mechanism of action and interactions with various receptors and to confirm its effectiveness in treating NALM6 leukemia.

Acquired copy number amplification at the MYC enhancer in human B-precursor acute lymphoblastic leukemia cell lines.

Our study highlights the discovery of recurrent copy number alterations in noncoding regions, specifically blood enhancer cluster (BENC-CNA), in B-precursor acute lymphoblastic leukemia (BCP-ALL) cell lines. We demonstrate that BENC-CNA acts as a super-enhancer, driving MYC expression and possibly contributing to the immortalization and proliferative advantage of BCP-ALL cells invitro.

Comparable efficacy of oral bendamustine versus intravenous administration in treating hematologic malignancies.

The purpose of this study was to analyze potential differences in antitumor efficacy and pharmacokinetics between intravenous (IV) bendamustine and a novel orally administered (PO) bendamustine agent that is utilizing the beneficial properties of superstaturated solid dispersions formulated in nanoparticles. Pharmacokinetics of IV versus PO bendamustine were determined by analysis of plasma samples collected from NSG mice treated with either IV or PO bendamustine. Plasma samples were analyzed using liquid chromatography-mass spectrometry following a liquid-liquid extraction to determine peak bendamustine concentration, area under the concentration-time curve, and the half-life in-vivo. In-vitro cytotoxicity of bendamustine against human non-Hodgkin Burkitt's Lymphoma (Raji), multiple myeloma (MM.1s), and B-cell acute lymphoblastic leukemia (RS4;11) cell lines was determined over time using MTS assays. Luciferase-tagged versions of the aforementioned cell lines were used to determine in-vivo bendamustine cytotoxicity of IV versus PO bendamustine at two different doses. Bendamustine at a high dose in-vitro causes cell death. There was no significant difference in antitumor activity between IV and novel PO bendamustine at a physiologically relevant concentration in all three xenograft models. In-vivo pharmacokinetics showed the oral bioavailability of bendamustine in mice to be 51.4%. The novel oral bendamustine agent tested exhibits good oral bioavailability and systemic exposure for in-vivo antitumor efficacy comparable to IV bendamustine. An oral bendamustine formulation offers exciting clinical potential as an additional method of administration for bendamustine and warrants further evaluation in clinical studies.

A Capillary-Force-Driven, Single-Cell Transfer Method for Studying Rare Cells.

The characterization of individual cells within heterogeneous populations (e.g., rare tumor cells in healthy blood cells) has a great impact on biomedical research. To investigate the properties of these specific cells, such as genetic biomarkers and/or phenotypic characteristics, methods are often developed for isolating rare cells among a large number of background cells before studying their genetic makeup and others. Prior to using real-world samples, these methods are often evaluated and validated by spiking cells of interest (e.g., tumor cells) into a sample matrix (e.g., healthy blood) as model samples. However, spiking tumor cells at extremely low concentrations is challenging in a standard laboratory setting. People often circumvent the problem by diluting a solution of high-concentration cells, but the concentration becomes inaccurate after series dilution due to the fact that a cell suspension solution can be inhomogeneous, especially when the cell concentration is very low. We report on an alternative method for low-cost, accurate, and reproducible low-concentration cell spiking without the use of external pumping systems. By inducing a capillary force from sudden pressure drops, a small portion of the cellular membrane was aspirated into the reservoir tip, allowing for non-destructive single-cell transfer. We investigated the surface membrane tensions induced by cellular aspiration and studied a range of tip/tumor cell diameter combinations, ensuring that our method does not affect cell viability. In addition, we performed single-cell capture and transfer control experiments using human acute lymphoblastic leukemia cells (CCRF-CEM) to develop calibrated data for the general production of low-concentration samples. Finally, we performed affinity-based tumor cell isolation using this method to generate accurate concentrations ranging from 1 to 15 cells/mL.

A novel type IIb L-asparaginase from Latilactobacillus sakei LK-145: characterization and application.

We succeeded in homogeneously expressing and purifying L-asparaginase from Latilactobacillus sakei LK-145 (Ls-Asn1) and its mutated enzymes C196S, C264S, C290S, C196S/C264S, C196S/C290S, C264S/C290S, and C196S/C264S/C290S-Ls-Asn1. Enzymological studies using purified enzymes revealed that all cysteine residues of Ls-Asn1 were found to affect the catalytic activity of Ls-Asn1 to varying degrees. The mutation of Cys196 did not affect the specific activity, but the mutation of Cys264, even a single mutation, significantly decreased the specific activity. Furthermore, C264S/C290S- and C196S/C264S/C290S-Ls-Asn1 almost completely lost their activity, suggesting that C290 cooperates with C264 to influence the catalytic activity of Ls-Asn1. The detailed enzymatic properties of three single-mutated enzymes (C196S, C264S, and C290S-Ls-Asn1) were investigated for comparison with Ls-Asn1. We found that only C196S-Ls-Asn1 has almost the same enzymatic properties as that of Ls-Asn1 except for its increased stability for thermal, pH, and the metals NaCl, KCl, CaCl2, and FeCl2. We measured the growth inhibitory effect of Ls-Asn1 and C196S-Ls-Asn1 on Jurkat cells, a human T-cell acute lymphoblastic leukemia cell line, using L-asparaginase from Escherichia coli K-12 as a reference. Only C196S-Ls-Asn1 effectively and selectively inhibited the growth of Jurkat T-cell leukemia, which suggested that it exhibited antileukemic activity. Furthermore, based on alignment, phylogenetic tree analysis, and structural modeling, we also proposed that Ls-Asn1 is a so-called "Type IIb" novel type of asparaginase that is distinct from previously reported type I or type II asparaginases. Based on the above results, Ls-Asn1 is expected to be useful as a new leukemia therapeutic agent.

Abstract 4710: The polymeric AMD3100 based drug PAMD-Ch17 induces its anti-leukemic effects in a CXCR4 independent mechanism

Abstract Background: Acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) are devastating blood cancers associated with 5-year survival rates of ~50% each in adults. We recently developed a new class of polymeric drugs called PAMDs based on the CXCR4 inhibitor AMD3100 (plerixafor). PAMDs have the potential to be more effective and less toxic therapeutics than the standard of care high-dose chemotherapy. We tested one variant (PAMD-Ch17), and found that unlike AMD3100, PAMD-Ch17 has several novel anti-leukemic effects. To understand the potential mechanism(s) for these new activities, we performed the following study. Methods: To test the role of CXCR4 in PAMD-Ch17’s activities, we generated CXCR4 knockout cells via Crispr/Cas9. We used PrestoBlue, 7-AAD, and Annexin V staining to assay viability and apoptosis. To identify pathways deregulated by PAMD-Ch17, we performed whole transcriptomic sequencing (RNA-Seq). To investigate if PAMD-Ch17 mediates its activities by inducing oxidative stress, we performed SeaHorse assays, and dihydroethidium (DHE), Mitosox, and Bodipy C11 staining. To investigate whether PAMD induces programmed cell death pathways, we used ferrostatin and deferoxamine to inhibit ferroptosis, necrostatin-1 against necroptosis, and Z-VAD-FMK against apoptosis. Results: We found that PAMD-Ch17 induces cell death in a dose dependent manner in human AML and ALL cell lines and, mouse primary leukemia cells, but not healthy mouse bone marrow cells. Surprisingly, PAMD-Ch17 induces equivalent levels of cell death in both wild type and CXCR4 knockout Jurkat cells, indicating that the only known target of the polymer is not required for its anti-leukemic effects. By RNA-Seq, we found altered expression of genes related to mitochondrial function, suggesting that PAMD-Ch17 could be targeting the mitochondria. To test this, we performed SeaHorse assays and found that PAMD-Ch17 induces a significant decrease in mitochondrial respiration. Consistent with this, we found that PAMD-Ch17 induces a significant increase in superoxide production, as well as lipid peroxidation. Using inhibitors of programmed cell death pathways, we found that preventing necroptosis, apoptosis, or ferroptosis caused only subtle effects on PAMD-Ch17 induced cell death, implying that the polymer’s anti-leukemic activity is likely not entirely dependent on these pathways. Conclusions: These results indicate that PAMD-Ch17 induces cell death in leukemia cells but not healthy bone marrow via a CXCR4 independent mechanism. We also found that PAMD-Ch17 induces reactive oxygen species, potentially explaining its selectivity for leukemia cells compared to healthy blood cells. Continued investigation of PAMD-Ch17 will not only further development of this new class of drugs, but also provide much needed insight into leukemia biology. Citation Format: Calvin Lam, Jogdeo Chinmay, Ekta Kapoor, Siyuan Tang, Svetlana Romanova, David Oupicky, Katherine Hyde. The polymeric AMD3100 based drug PAMD-Ch17 induces its anti-leukemic effects in a CXCR4 independent mechanism [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 4710.

Targeting TNF/IL-17/MAPK pathway in hE2A-PBX1 leukemia: effects of OUL35, KJ-Pyr-9, and CID44216842.

t(1;19)(q23;p13) is one of the most common translocation genes in childhood acute lymphoblastic leukemia (ALL) and is also present in acute myeloid leukemia (AML) and mixed-phenotype acute leukemia (MPAL). This translocation results in the formation of the oncogenic E2A-PBX1 fusion protein, which contains a trans-activating domain from E2A and a DNA-binding homologous domain from PBX1. Despite its clear oncogenic potential, the pathogenesis of E2A-PBX1 fusion protein is not fully understood (especially in leukemias other than ALL), and effective targeted clinical therapies have not been developed. To address this, we established a stable and heritable zebrafish line expressing human E2A-PBX1 (hE2A-PBX1) for high-throughput drug screening. Blood phenotype analysis showed that hE2A-PBX1 expression induced myeloid hyperplasia by increasing myeloid differentiation propensity of hematopoietic stem cells (HSPC) and myeloid proliferation in larvae, and progressed to AML in adults. Mechanistic studies revealed that hE2A-PBX1 activated the TNF/IL-17/MAPK signaling pathway in blood cells and induced myeloid hyperplasia by upregulating the expression of runx1. Interestingly, through high-throughput drug screening, three small molecules targeting the TNF/IL-17/MAPK signaling pathway were identified, including OUL35, KJ-Pyr-9, and CID44216842, which not only alleviated the hE2A-PBX1-induced myeloid hyperplasia in zebrafish but also inhibited the growth and oncogenicity of human pre-B ALL cells with E2A-PBX1. Overall, this study provides a novel hE2APBX1 transgenic zebrafish leukemia model and identifies potential targeted therapeutic drugs, which may offer new insights into the treatment of E2A-PBX1 leukemia.

Biochips to measure ultraviolet light absorption by leukemia cells

During the treatment of leukemia, side effects create a great burden for patients. Therefore, new therapies to replace conventional chemotherapy and hematopoietic stem cell transplantation are highly desirable. In a previous study, I found that UV irradiation at 365 nm induced apoptosis in 98% of leukemia (Jurkat T) cells. To determine the most suitable wavelength for such treatments, it is necessary to measure the UV light absorption of cancer cells. In this study, a biochip was fabricated and evaluated for this purpose. Three types of leukemic cells (human acute myelogenous leukemia cells, human acute lymphoblastic leukemia cells, and human chronic myelogenous leukemia cells) were injected into the biochip, and light absorption was measured, revealing that individual leukemic cells have different light absorption characteristics. This variation is important in order to develop an implant care device to treat leukemia more effectively.

Regulating TKT activity inhibits proliferation of human acute lymphoblastic leukemia cells

Regulating TKT activity inhibits proliferation of human acute lymphoblastic leukemia cells

Enhancement of the Sensitivity of the Acute Lymphoblastic Leukemia Cells to ABT-737 by Formononetin.

Overexpression of (myeloid leukemia cell differentiation protein 1) Mcl-1 is associated with the reduction of ABT-737 toxicity and secondary resistance. In this study, the effect of formononetin (biochanin B) on Mcl-1 expression, cell growth, apoptosis, and ABT-737 sensitivity of the acute lymphoblastic leukemia (ALL) cells was investigated. In this experimental study, the cell proliferation and MTT assays were used to investigate the effect of formononetin on cell growth and survival. qRT-PCR was performed for the measurement of gene expression. Hoechst 33342 staining and caspase-3 activity assay were used for the determination of apoptosis. Our data showed that formononetin and ABT-737 both led to a significant reduction in the IC50 value and synergistically reduced the cell growth and survival relative to single treatment. Overexpression of Mcl-1 was found after the treatment with ABT-737. Formononetin decreased the expression of B-cell lymphoma 2 (Bcl-2) and Mcl-1 and increased the Bcl-2-associated protein x (Bax) and P21 expression. Moreover, formononetin enhanced the apoptotic effect of ABT-737 in ALL cells. In summary, formononetin showed anti-carcinogenic activities in human ALL cells via suppression of cell growth and survival. Formononetin enhanced the apoptotic effect of ABT-737, with contribution by inhibition of the Mcl-1 expression.

Thiophene derivative inflicts cytotoxicity via an intrinsic apoptotic pathway on human acute lymphoblastic leukemia cells.

In an effort to identify novel anti-cancer agents, we employed a well-established High Throughput Screening (HTS) assay to assess the cytotoxic effect of compounds within the ChemBridge DIVERSet Library on a lymphoma cell line. This screen revealed a novel thiophene, F8 (methyl 5-[(dimethylamino)carbonyl]-4-methyl-2-[(3-phenyl-2-propynoyl) amino]-3-thiophenecarboxylate), that displays anti-cancer activity on lymphoma, leukemia, and other cancer cell lines. Thiophenes and thiophene derivatives have emerged as an important class of heterocyclic compounds that have displayed favorable drug characteristics. They have been previously reported to exhibit a broad spectrum of properties and varied uses in the field of medicine. In addition, they have proven to be effective drugs in various disease scenarios. They contain anti-inflammatory, anti-anxiety, anti-psychotic, anti-microbial, anti-fungal, estrogen receptor modulating, anti-mitotic, kinase inhibiting and anti-cancer activities, rendering compounds with a thiophene a subject of significant interest in the scientific community. Compound F8 consistently induced cell death at a low micromolar range on a small panel of cancer cell lines after a 48 h period. Further investigation revealed that F8 induced phosphatidylserine externalization, reactive oxygen species generation, mitochondrial depolarization, kinase inhibition, and induces apoptosis. These findings demonstrate that F8 has promising anti-cancer activity.

Zebrafish drug screening identifies Erlotinib as an inhibitor of Wnt/β-catenin signaling and self-renewal in T-cell acute lymphoblastic leukemia

The Wnt/β-catenin pathway’s significance in cancer initiation, progression, and stem cell biology underscores its therapeutic potential. However, the clinical application of Wnt inhibitors remains limited due to challenges posed by off-target effects and complex cross-talk of Wnt signaling with other pathways. In this study, we leveraged a zebrafish model to perform a robust and rapid drug screening of 773 FDA-approved compounds to identify Wnt/β-catenin inhibitors with minimal toxicity. Utilizing zebrafish expressing a Wnt reporter, we identified several drugs that suppressed Wnt signaling without compromising zebrafish development. The efficacy of the top hit, Erlotinib, extended to human cells, where it blocked Wnt/β-catenin signaling downstream of the destruction complex. Notably, Erlotinib treatment reduced self-renewal in human T-cell Acute Lymphoblastic Leukemia cells, which rely on active β-catenin signaling for maintenance of leukemia-initiating cells. Erlotinib also reduced leukemia-initiating cell frequency and delayed disease formation in zebrafish models. This study underscores zebrafish’s translational potential in drug discovery and repurposing and highlights a new use for Erlotinib as a Wnt inhibitor for cancers driven by aberrant Wnt/β-catenin signaling.

Novel wild edible mushroom Astraeus hygrometricus (Pers.) Morgan induces robust apoptosis on human acute lymphoblastic leukemia cells through a RONS-subsisted mitochondria-dependent pathway

ObjectiveTo explore the therapeutic effects of the novel wild edible mushroom Astraeus hygrometricus (Pers.) Morgan (A. hygrometricus) on human acute lymphoblastic leukemia cells. MethodsExtensive screening of the antiproliferative and chemopreventive potential of different extracts from 5 wild mushrooms, A. hygrometricus, Phallus sp., Lentinus sp., Tricholoma sp., and Serpula sp. was performed against a panel of 6 cancer cell lines and normal cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis determination, cell cycle profiling, intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS), and mitochondrial membrane potential were analyzed by flow cytometry. The activity of caspases was measured colorimetrically, and the expression pattern of mitochondrial proteins was analyzed. ResultsThe methanol extract of A. hygrometricus and MOLT-4 cells were identified as the most potent extract exhibiting antiproliferative activity and most sensitive cell line, respectively. The mushroom extract induced robust selective apoptosis in MOLT-4 cells and arrested cell cycle progression at the G0/G1 stage. The extract disrupted the mitochondrial membrane potential and enhanced ROS production in MOLT-4 cells. The methanol extract induced apoptosis by downregulating the expression of Bcl-2, increasing the expression of Bax, and activating the caspase cascade. ConclusionThe novel wild edible mushroom is a potential repository of biomolecules for the development of antileukemic drugs.

Ubiquitin-Mediated Degradation of MORF4L1 By FBXO11 Suppresses Cholesterol Biosynthesis in T Cell Acute Lymphoblastic Leukemia

The substrate receptor of SKP1-Cullin1-FBOX complex, FBXO11, is frequently mutated in both diffuse large B cell lymphoma and acute myeloid leukemia, and typically functions as a tumor suppressor by targeting substrates for ubiquitin-mediated degradation. Although FBXO11 is also mutated in human T-cell acute lymphoblastic leukemia (T-ALL) cell lines, the underlying mechanism in T-ALL development remains to be established. Here, we identified that both endogenous activation and exogenous overexpression of FBXO11 could suppress the growth of T-ALL cell in vitro and in vivo. While conversely, loss of FBXO11 accelerates the T-ALL cell proliferation. Transcriptomic and total quantitative proteomic analyses in FBXO11-depleted T-ALL cells reveal activation of the cholesterol biosynthesis pathway with accumulation of intracellular cholesterol levels. Importantly, we identified a chromatin regulator MORF4L1, mortality factor 4 like protein 1, as a functional substrate of FBXO11 in T-ALL cells. We first observed that FBXO11 exhibited frequent copy number alterations in T-ALL cell lines and in patient cohorts from public datasets. Moreover, by CRISPR SAM (Synergistic Activation Mediator) endogenous activation and lentiviral mediated gene overexpression, we validated that FBXO11 played a role in inhibiting tumor cell proliferation in T-ALL cells both in vitro and in vivo. Conversely, loss of FBXO11 accelerated T-ALL cell proliferation. Taken together, our results suggest that FBXO11 functions as a tumor suppressor in T-ALL. Mechanistically, we uncovered that the absence of FBXO11 could activate the cholesterol synthesis signaling pathway from both the RNA-seq and the TMT proteomic analysis in FBXO11-depleted MOLT4 cells compared to control cells. Concordantly, loss of FBO11 resulted in the accumulation of intracellular cholesterol level, suggesting that FBXO11 may suppress cholesterol biosynthesis in T-ALL cells. To understand how FBXO11 controls cholesterol biosynthesis, we further identified the potential substrates from the combined quantitative transcriptome and proteome analysis. MORF4L1, a chromatin modifier involved in histone acetylation, was identified as a key substrate of FBXO11 based on its upregulation at the protein level in FBXO11-depleted cells. Moreover, our data suggest MORF4L1 is a regulator of cholesterol biosynthesis in T-ALL. The inhibition of MORF4L1 suppressed the cellular growth of T-ALL cell lines, and led to the downregulation of the expression of cholesterol-related genes, such as gene HMGCR and HMGCS1. Of note, suppression of MORF4L1 and its cholesterol biosynthesis target genes such as HMGCR, HMGCS1 could rescue the accelerated growth effect after loss of FBXO11, indicating a functional role for MORF4L1 in T-ALL development. In summary, our data support a model wherein the degradation of MORF4L1 by FBXO11 suppresses leukemia cell growth by controlling cholesterol biosynthesis. The identification of this regulatory mechanism is required for T-ALL and provides valuable insights into the metabolic vulnerabilities of leukemia.

Targeting IGF2BP3 Enhances Anti-Leukemic Effects of Menin-MLL Inhibition in MLL-AF4 Leukemia

Background: MLL-rearranged leukemias are a clinically challenging and biologically unique subtype of leukemias associated with poor prognosis. While novel therapeutic strategies have been primarily directed at epigenetic dysregulation, post-transcriptional gene regulatory mechanisms have emerged as important mediators in leukemogenesis and have the unexplored potential to be potent combinatorial therapeutic targets. Previously, we found that the RNA-binding protein IGF2BP3 is a critical regulator of MLL-AF4 leukemogenesis and represents a promising therapeutic target. Methods: We studied the combined effects of targeting IGF2BP3 and the Menin-MLL interaction in MLL-AF4 driven leukemia in vitro and in vivo, using genetic inhibition through CRISPR-Cas9 mediated deletion of Igf2bp3 and pharmacologic inhibition of the Menin-MLL interaction with commercially available inhibitors MI-503, MI-463, and MI-538. In vitro, we tested the human B-cell acute lymphoblastic leukemia cell lines, SEM, RS4;11 and NALM6, and MLL-Af4-transformed murine hematopoietic stem and progenitor cells (herein referred to as MLL-Af4 Lin-), derived from bone marrow of Cas9 mice. Results: Depletion of Igf2bp3 sensitized MLL-AF4 leukemia to the negative effects of Menin-MLL inhibition on leukemic cell growth, colony formation and leukemic initiating cells in vitro. Mechanistically, we found that both Igf2bp3 depletion and Menin-MLL inhibition led to increased differentiation in vitro and in vivo in functional readouts and by gene expression analyses. Both MI-503 treatment and IGF2BP3 knockdown in MLL-Af4 Lin- cells showed a shift towards more differentiated colony morphologies in colony formation assays, decreased expression of c-Kit and increased expression of maturation markers by flow cytometry, and morphologic changes consistent with increased differentiation. To gain insight into these phenotypic findings, we examined gene expression from MLL-Af4 Lin- cells with IGF2BP3 knockdown and treated with MI-503. Metascape analysis revealed significant enrichment in pathways involved in cell differentiation and activation, particularly in leukocytes. This was observed in both I3KO and MI-503 treated cells, with significant overlap in shared differentially expressed genes in both conditions. Next, we looked at the overlap between differentially expressed genes with MI-503 treatment and IGF2BP3 knockdown with targets identified from MLL-AF4 ChIP and IGF2BP3 CLIP in CD11b+ and MLL-Af4 Lin- cells. We found significant overlap between differentially expressed genes with MI-503 treatment and IGF2BP3 CLIP targets, suggesting that IGF2BP3 directly regulates genes that are affected by Menin-MLL inhibition. Furthermore, we saw overlap between differentially expressed genes with IGF2BP3 knockdown and MLL-AF4 ChIP targets identified in SEM and RS4;11 cells. These patterns highlight the interaction between the MLL-AF4 and IGF2BP3 transcriptomes and suggest a mechanism for the synergistic inhibition of leukemia by targeting both MLL-AF4 and IGF2BP3. To examine the combined effects of IGF2BP3 knockdown and Menin-MLL inhibition on leukemic engraftment and survival in vivo, we transplanted MLL-Af4 Lin- cells, depleted (or non-depleted) for IGF2BP3 and treated with MI-503 at 0.5 μM for 5 days, to initiate leukemia. We observed a significant decrease in peripheral blood leukemic engraftment with MI-503 treatment and IGF2BP3 knockdown. IGF2BP3 knockdown had a greater effect on survival and attenuating disease than MI-503 alone and showed enhanced anti-leukemic effects in combination. Conclusions: Our work shows that IGF2BP3 is an oncogenic amplifier of MLL-AF4 mediated leukemogenesis and is a potent therapeutic target and suggests a novel combinatorial approach to targeting leukemia at both the transcriptional and post-transcriptional level.

Canonical BAF complex regulates the oncogenic program in human T-cell acute lymphoblastic leukemia

AbstractAcute leukemia cells require bone marrow microenvironments, known as niches, which provide leukemic cells with niche factors that are essential for leukemic cell survival and/or proliferation. However, it remains unclear how the dynamics of the leukemic cell–niche interaction are regulated. Using a genome-wide CRISPR screen, we discovered that canonical BRG1/BRM-associated factor (cBAF), a variant of the switch/sucrose nonfermenting chromatin remodeling complex, regulates the migratory response of human T-cell acute lymphoblastic leukemia (T-ALL) cells to a niche factor CXCL12. Mechanistically, cBAF maintains chromatin accessibility and allows RUNX1 to bind to CXCR4 enhancer regions. cBAF inhibition evicts RUNX1 from the genome, resulting in CXCR4 downregulation and impaired migration activity. In addition, cBAF maintains chromatin accessibility preferentially at RUNX1 binding sites, ensuring RUNX1 binding at these sites, and is required for expression of RUNX1-regulated genes, such as CDK6; therefore, cBAF inhibition negatively impacts cell proliferation and profoundly induces apoptosis. This anticancer effect was also confirmed using T-ALL xenograft models, suggesting cBAF as a promising therapeutic target. Thus, we provide novel evidence that cBAF regulates the RUNX1-driven leukemic program and governs migration activity toward CXCL12 and cell-autonomous growth in human T-ALL.

Effect of LncRNA GATA3-AS1 Targeting MiR-515-5p on Cell Proliferation and Apoptosis in Childhood Acute Lymphoblastic Leukemia Cells

To investigate the effects of long non-coding RNA (lncRNA) GATA3 antisense RNA 1 (GATA3-AS1) targeting miR-515-5p on the proliferation and apoptosis of childhood acute lymphoblastic leukemia (ALL) cells. RT-qPCR was used to determine the expression of GATA3-AS1 and miR-515-5p in the plasma of controls and ALL children. Human ALL cells Jurkat were divided into si-GATA3-AS1, si-NC, miR-NC, miR-515-5p, si-GATA3-AS1+anti-miR-NC and si-GATA3-AS1+anti-miR-515-5p groups. CCK-8 assay was used to detect the cell proliferation, and flow cytometry was used to detect the cell apoptosis. The targeting relationship between GATA3-AS1 and miR-515-5p was determined by dual-luciferase reporter assay. The expression level of GATA3-AS1 in the plasma of ALL children was significantly higher than that of controls (P <0.001), while the expression level of miR-515-5p was significantly lower than that of controls (P <0.001). Compared with the si-NC group, the cell inhibition rate, apoptosis rate, and miR-515-5p expression level in si-GATA3-AS1 group were significantly increased (P <0.001). Compared with the miR-NC group, the cell inhibition rate and apoptosis rate in miR-515-5p group were significantly increased (P <0.001). GATA3-AS1 could directly and specifically bind to miR-515-5p. Compared with the si-GATA3-AS1+anti-miR-NC group, the cell inhibition rate and apoptosis rate in si-GATA3-AS1+anti-miR-515-5p group were significantly decreased (P <0.001). Down-regulation of GATA3-AS1 can inhibit proliferation and induce apoptosis of childhood ALL cells by targeting up-regulation of miR-515-5p expression.

ATF4 renders human T-cell acute lymphoblastic leukemia cell resistance to FGFR1 inhibitors through amino acid metabolic reprogramming.

Abnormalities of FGFR1 have been reported in multiple malignancies, suggesting FGFR1 as a potential target for precision treatment, but drug resistance remains a formidable obstacle. In this study, we explored whether FGFR1 acted a therapeutic target in human T-cell acute lymphoblastic leukemia (T-ALL) and the molecular mechanisms underlying T-ALL cell resistance to FGFR1 inhibitors. We showed that FGFR1 was significantly upregulated in human T-ALL and inversely correlated with the prognosis of patients. Knockdown of FGFR1 suppressed T-ALL growth and progression both in vitro and in vivo. However, the T-ALL cells were resistant to FGFR1 inhibitors AZD4547 and PD-166866 even though FGFR1 signaling was specifically inhibited in the early stage. Mechanistically, we found that FGFR1 inhibitors markedly increased the expression of ATF4, which was a major initiator for T-ALL resistance to FGFR1 inhibitors. We further revealed that FGFR1 inhibitors induced expression of ATF4 through enhancing chromatin accessibility combined with translational activation via the GCN2-eIF2α pathway. Subsequently, ATF4 remodeled the amino acid metabolism by stimulating the expression of multiple metabolic genes ASNS, ASS1, PHGDH and SLC1A5, maintaining the activation of mTORC1, which contributed to the drug resistance in T-ALL cells. Targeting FGFR1 and mTOR exhibited synergistically anti-leukemic efficacy. These results reveal that FGFR1 is a potential therapeutic target in human T-ALL, and ATF4-mediated amino acid metabolic reprogramming contributes to the FGFR1 inhibitor resistance. Synergistically inhibiting FGFR1 and mTOR can overcome this obstacle in T-ALL therapy.

Ruxolitinib inhibits the proliferation and induces the apoptosis of MLL-r ALL cells through inactivating JAK/STAT signaling pathway.

The childhood patients with mixed-lineage leukemia rearrangement (MLL-r) gene have worse outcome than non-MLL, and thus often treated with high-risk chemotherapy regimens, so targeted therapy is important for this type of leukemia. This purpose of study was to explore the effects of ruxolitinib on the proliferation, apoptosis, and cell cycle of Nalm-6 cells. In this study, human acute lymphoblastic leukemia (ALL) cell line Nalm-6 was used as the research object. By constructing an MLL overexpression vector to transfect Nalm-6 cells, exogenous JAK2/STAT3 signal pathway inhibitor ruxolitinib was applied to observe the proliferation, apoptosis, and cell cycle changes of the transfected Nalm-6 cells. Western blot was performed to determine the proteins (MLL-BP, JAK, STAT) involved in the mechanism of action of MLL-r leukemia. CCK8 assay and flow cytometry (FCM) were used for testing the proliferation and apoptosis among MLL-BP transfected Nalm-6 cells. Firstly, we determine the IC50 of ruxolitinib on Nalm-6 cells. Secondly, FCM and CCK8 showed that ruxolitinib dosedependentlyinhibits proliferation of Nalm-6 cells by blocking the cell cycle at G0/G1 phase. In addition, FCM showed that ruxolitinib promoted the apoptosis of MLL-BP transfected Nalm-6 cells. Mechanistically, ruxolitinib inactivated JAK/STAT signaling pathway in MLL-BP transfected Nalm-6 cells, mediating ruxolitinib's inhibition of cell proliferation, and inducing apoptosis. Finally, ruxolitinib significantly inhibited the proliferation of MLL-r ALL cells and promoted their apoptosis. These data provide compelling evidence that ruxolitinib is a promising agent against MLL-r leukemia cell line. However, it needs going through multiple more steps to confirm before it can be an option in clinical practice.