K562 Erythroleukemia Cells Research Articles

GPS2 promotes erythroid differentiation in K562 erythroleukemia cells primarily via NCOR1.

G protein pathway suppressor 2 (GPS2) has been shown to play a pivotal role in human and mouse definitive erythropoiesis in an EKLF-dependent manner. However, whether GPS2 affects human primitive erythropoiesis is still unknown. This study demonstrated that GPS2 positively regulates erythroid differentiation in K562 cells, which have a primitive erythroid phenotype. Overexpression of GPS2 promoted hemin-induced hemoglobin synthesis in K562 cells as assessed by the increased percentage of benzidine-positive cells and the deeper red coloration of the cell pellets. In contrast, knockdown of GPS2 inhibited hemin-induced erythroid differentiation of K562 cells. GPS2 overexpression also enhanced erythroid differentiation of K562 cells induced by cytosine arabinoside (Ara-C). GPS2 induced hemoglobin synthesis by increasing the expression of globin and ALAS2 genes, either under steady state or upon hemin treatment. Promotion of erythroid differentiation of K562 cells by GPS2 mainly relies on NCOR1, as knockdown of NCOR1 or lack of the NCOR1-binding domain of GPS2 potently diminished the promotive effect. Thus, our study revealed a previously unknown role of GPS2 in regulating human primitive erythropoiesis in K562 cells.

Liver X receptor activation in chronic myelogenous leukemia cells yields distinct mass fingerprints by whole cell MALDI-TOF MS, which correspond to changes in cell viability, gene expression, and differentiation markers

Liver X receptor (LXR) agonists, including synthetic ligands or naturally-occurring oxysterols, exert promising lipid-modulating, anti-inflammatory, and anti-tumor effects. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) whole cell mass spectrometry (MS) shows promise in chronic disease and food science research, clinical diagnostics of cancer cells and bacterial pathogens, and drug/nutraceutical discovery due to its relatively low-cost, rapid, reliable, and high-throughput ability to identify unique cell phenotypes and differentiation states of immune cells that play essential roles in chronic metabolic and inflammatory disease pathophysiology. However, optimization of whole cell MALDI-TOF MS-based methods to assess cellular changes in response to pharmaceutical and/or nutraceutical treatment warrants further study. Thus, we investigated whether whole cell MALDI-TOF MS could detect cellular phenotype changes of human stem-like erythroleukemia K562 cells – a model for chronic myelogenous leukemia (CML) – induced by the LXR agonist TO-901317, a synthetic ligand that mimics effects of naturally-occurring oxysterols, which are oxidized cholesterol derivatives formed under conditions of high cellular cholesterol concentrations and in food products. TO-901317 dose- and time-dependently altered mRNA expression of cholesterol flux genes, including ATP-binding cassette transporter A1 (ABCA1), LDL-receptor (LDLR), HMG-CoA reductase (HMGCR), and reduced cellular cholesterol content by 22.9% at 24 h. TO-901317 additionally dose- and time-dependently impacted K562 cell viability, number, size, and reduced mRNA expression of the anti-apoptotic gene BCL2L1 by 43.3%. These effects corresponded to induced gene expression of erythroid markers and hemoglobin content, suggesting that LXR activation may promote erythroid lineage differentiation. Whole cell MALDI-TOF MS mass fingerprinting revealed distinct proteomic phenotypes between TO-901317 vs. untreated cells, and identified histone 2 A and histone H4 as uniquely expressed proteins. These findings not only elucidate a novel role for LXR agonists in a model of CML, but demonstrate that mass fingerprints obtained by whole cell MALDI-TOF mass spectrometry effectively distinguish between treatment-induced cell phenotypes.

Lysophosphatidic Acid Receptor 3 Activation Is Involved in the Regulation of Erythrocyte Differentiation Through Ferroptosis

Ferroptosis, a unique form of programmed cell death trigged by lipid peroxidation and iron accumulation, has been implicated in embryonic erythropoiesis and aging. Our previous research demonstrated that lysophosphatidic acid receptor 3 (LPA3) activation mitigated oxidative stress in progeria cells and accelerate the recovery of acute-anemia in mice. Given that both processes involve iron metabolism, we hypothesized that LPA3 activation might mediate cellular ferroptosis. In this study, we used LPA3 agonists 1‐Oleoyl‐2‐O‐methyl‐rac‐glycerophosphothionate (OMPT) to activate LPA3 and examine its effects on the ferroptosis process. OMPT treatment elevated anti-ferroptosis genes protein expression, including solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1), and ferritin heavy chain (FTH1) in erastin-induced cells. Furthermore, OMPT reduced lipid peroxidation and intracellular ferrous iron accumulation, as evidenced by C11 BODIPYTM 581/591 Lipid Peroxidation Sensor and FerroOrange staining. These observations were validated by applying LPAR3 siRNA in the experiments mentioned above. In addition, the protein expression level of nuclear factor erythroid 2-related factor (NRF2), a key regulator of oxidative stress regulator, was also enhanced in OMPT treated cells. Lastly, we verified that LPA3 plays a critical role in erastin-induced ferroptotic human 25 erythroleukemia K562 cells. OMPT rescued the erythropoiesis defect caused by erastin in K562 cells through using Gly A promoter luciferase assay. Taken together, our findings suggest that LPA3 activation inhibits cell ferroptosis by suppressing lipid oxidation and iron accumulation, indicating that ferroptosis could potentially serve as a link between LPA3, aging and erythropoiesis. MOST 110-2311-B-002-026 MOST 111-2311-B-002-007. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 5630: Targeting the LSD1/ADNP axis as an effective pro-differentiating strategy against acute myeloid leukemia AML

Abstract Acute Myeloid Leukemia (AML) represents a diverse category of blood cancers marked by the clonal proliferation of atypical myeloid precursor cells within the bone marrow. Lysine Specific Demethylase 1 (LSD1), an epigenetic regulator, exhibits elevated expression in AML. Consequently, inhibiting LSD1 has emerged as a promising therapeutic approach for addressing blood and bone marrow cancers. While initial emphasis centered on LSD1's enzymatic inhibition, compelling evidence highlights its pivotal role as a scaffolding protein, orchestrating transcriptional and chromatin remodeling complexes that control cellular differentiation and proliferation. However, our understanding of the precise mechanisms governing these complexes remains limited, necessitating further investigation. The K562 erythroleukemia cell line has served as a prominent model for investigating the molecular factors influencing cell fate determination. In response to specific cues, these cells exhibit a bi-potential capacity, mirroring the behavior of normal hematopoietic megakaryocyte/erythrocyte progenitors (MEP). Notably, when LSD1 is either depleted or inhibited, the erythroid differentiation of K562 cells is hindered, even when exposed to various pro-differentiating triggers, including the BCR-ABL inhibitor Imatinib. In order to gain deeper insights and identify potential new protein partners involved in the K562 differentiation process that interact with LSD1, we employed the erythroleukemic K562 cell model. Using unbiased, proteome-wide proximity labeling we discovered that LSD1 serves as a scaffold for recruitment of the ChAHP complex, comprised of ADNP, CBX3, and CHD4. The ChAHP complex serves fundamental roles in chromatin remodeling, RNA splicing, and transcriptional control. We confirmed these proximity relationships by immunoblotting biotinylated proteins generated in situ by the promiscuous biotin ligase, (BirA*) when anchored to LSD1. We show that depleting ADNP induces spontaneous erythroid differentiation in K562 erythroleukemia cells, which is augmented by BCR-ABL inhibitor Imatinib treatment. ADNP-deficient K562 cells exhibited accelerated erythroid differentiation, as evidenced by a four-fold increase in the surface expression of erythroid markers (CD71, CD235a) and a significant upregulation of beta-globin gene cluster markers. These findings collectively suggest an antagonistic functional relationship between ADNP and LSD1, potentially counterbalancing LSD1's role in lineage allocation. Furthermore, we demonstrate that the loss of the key ChAHP component, ADNP, substantially hampers proliferation and increases apoptosis in K562 cells. These results underscore the potential of ADNP/ChAHP as an appealing target to modulate the choice between erythroid and megakaryocytic fates and offer promise as a target for pro-differentiation therapies in AML Citation Format: Mehraju Din Lone, Mohd Sayeed, Alaa Habieb, Praveen Kumar, Michael E. Engel. Targeting the LSD1/ADNP axis as an effective pro-differentiating strategy against acute myeloid leukemia AML [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 5630.

Lysophosphatidic Acid Receptor 3 Activation Is Involved in the Regulation of Ferroptosis.

Ferroptosis, a unique form of programmed cell death trigged by lipid peroxidation and iron accumulation, has been implicated in embryonic erythropoiesis and aging. Our previous research demonstrated that lysophosphatidic acid receptor 3 (LPA3) activation mitigated oxidative stress in progeria cells and accelerated the recovery of acute anemia in mice. Given that both processes involve iron metabolism, we hypothesized that LPA3 activation might mediate cellular ferroptosis. In this study, we used an LPA3 agonist, 1-Oleoyl-2-O-methyl-rac-glycerophosphothionate (OMPT), to activate LPA3 and examine its effects on the ferroptosis process. OMPT treatment elevated anti-ferroptosis gene protein expression, including solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1), and ferritin heavy chain (FTH1), in erastin-induced cells. Furthermore, OMPT reduced lipid peroxidation and intracellular ferrous iron accumulation, as evidenced by C11 BODIPY™ 581/591 Lipid Peroxidation Sensor and FerroOrange staining. These observations were validated by applying LPAR3 siRNA in the experiments mentioned above. In addition, the protein expression level of nuclear factor erythroid 2-related factor (NRF2), a key regulator of oxidative stress, was also enhanced in OMPT-treated cells. Lastly, we verified that LPA3 plays a critical role in erastin-induced ferroptotic human erythroleukemia K562 cells. OMPT rescued the erythropoiesis defect caused by erastin in K562 cells based on a Gly A promoter luciferase assay. Taken together, our findings suggest that LPA3 activation inhibits cell ferroptosis by suppressing lipid oxidation and iron accumulation, indicating that ferroptosis could potentially serve as a link among LPA3, erythropoiesis, and aging.

New Synthetic Isoxazole Derivatives Acting as Potent Inducers of Fetal Hemoglobin in Erythroid Precursor Cells Isolated from β-Thalassemic Patients.

Induction of fetal hemoglobin (HbF) is highly beneficial for patients carrying β-thalassemia, and novel HbF inducers are highly needed. Here, we describe a new class of promising HbF inducers characterized by an isoxazole chemical skeleton and obtained through modification of two natural molecules, geldanamycin and radicicol. After preliminary biological assays based on benzidine staining and RT-qPCR conducted on human erythroleukemic K562 cells, we employed erythroid precursors cells (ErPCs) isolated from β-thalassemic patients. ErPCs weretreated with appropriate concentrations of isoxazole derivatives. The accumulation of globin mRNAs was studied by RT-qPCR, and hemoglobin production by HPLC. We demonstrated the high efficacy of isozaxoles in inducing HbF. Most of these derivatives displayed an activity similar to that observed using known HbF inducers, such as hydroxyurea (HU) or rapamycin; some of the analyzed compounds were able to induce HbF with more efficiency than HU. All the compounds were active in reducing the excess of free α-globin in treated ErPCs. All the compounds displayed a lack of genotoxicity. These novel isoxazoles deserve further pre-clinical study aimed at verifying whether they are suitable for the development of therapeutic protocols for β-thalassemia.

Ncrna-a3 Epigenetically Regulates TAL1 and Its Target Genes to Drive Erythroid Differentiation

Erythropoiesis is the development of enucleated red blood cells from multipotent hematopoietic stem cells. This complex process is tightly regulated by the dynamic changes in occupancy of tissue specific transcription factors (TFs) that activate and repress genes appropriately. TAL1, a critical regulator is expressed throughout the development of mature erythroblasts from multi-progenitors. Loss of TAL1 leads to defective erythropoiesis. As opposed to TAL1's role in erythropoiesis, itis an extraneous factor in developing lymphoid cells and aberrant expression of TAL1 in T-cells is associated with T-ALL. The differential regulation during normal and malignant hematopoiesis remains largely unclear. We found that a distil RNA - ncRNA-a3, is transcribed from erythroid specific enhancer, 50kbp downstream of the TAL1 TSS. We hypothesized that ncRNA-a3 plays an important role in regulating TAL1 and its target gene transcription in an erythroid specific manner. To test this hypothesis, we examine the regulatory potential of ncRNA-a3 towards the activation of TAL1 expression in the context of hematopoiesis and leukemogenesis. We used RNA interference to deplete ncRNA-a3 expression across several hematopoietic and leukemic cells. The decrease in ncRNA-a3 resulted in significant reduction of TAL1 transcript and protein levels in hematopoietic cells while TAL1 transcripts showed little or no reduction in leukemic cells. Subsequently, transcriptomic profile changes in erythroleukemic K562 cells showed downregulation of erythroid specific targets of TAL1. To ascertain the role of ncRNA-a3 in erythropoiesis, we used siRNA against ncRNA-a3 in primary CD34+ cells and subjected cells to differentiation. Quantification of early and late erythroblasts by colony forming assay and flow cytometry indicated impaired erythroid differentiation and maturation in orthochromatic and polychromatic stages. Further, RNA-seq analysis of ncRNA-a3 knockdown cells revealed defects in globin gene function, heme biosynthesis and nucleosome condensation compared to control CD34+ cells during time course EPO induced erythroid differentiation. Mechanistically, we observed ncRNA-a3s occupancy at TAL1 regulatory regions from ChIRP-qPCR across TAL1 locus. NG Capture-C data depicting changes in interaction frequencies indicated that ncRNA-a3 maintains canonical interactions at the TAL1 locus. Knockdown of ncRNA-a3 negatively impacted the chromatin accessibility in TAL1 and TAL1 target loci. Perturbation of chromatin landscape affected TAL1 and TAL1 binding partner - P300 and BRG1 occupancy at TAL1 target sites. To distinguish reduced TAL1 binding as a consequence of lower levels of TAL1, from RNA dependent binding of TAL1, we examined TAL1, P300 and BRG1 chromatin occupancy through Cut&Run in conjunction with RNase treatment. Effective depletion of global RNAs resulted in reduced enrichment of TAL1, P300 and BRG1 bound fragments indicating possible RNA dependent binding of TAL1 and its cofactors. TAL1 coimmunoprecipitation using RNase treatment (1) and ncRNA-a3 KD (2), demonstrated that TAL1s interaction with P300 and BRG1 is RNA dependent, but ncRNA-a3 independent. RNA-IP results further confirmed that ncRNA-a3 is associated with TAL1 through its interacting epigenetic cofactors P300 and BRG1. Together, our data indicate that although RNA dependent binding of TAL1 and its epigenetic cofactors is cell type or target locus specific, ncRNA-a3 modulates the occupancy of TAL1, P300 and BRG1 at the TAL1 locus during erythroid specific TAL1 transcription.

RepID represses megakaryocytic differentiation by recruiting CRL4A-JARID1A at DAB2 promoter

BackgroundMegakaryocytes (MKs) are platelet precursors, which arise from hematopoietic stem cells (HSCs). While MK lineage commitment and differentiation are accompanied by changes in gene expression, many factors that modulate megakaryopoiesis remain to be uncovered. Replication initiation determinant protein (RepID) which has multiple histone-code reader including bromodomain, cryptic Tudor domain and WD40 domains and Cullin 4-RING E3 ubiquitin ligase complex (CRL4) recruited to chromatin mediated by RepID have potential roles in gene expression changes via epigenetic regulations. We aimed to investigate whether RepID-CRL4 participates in transcriptional changes required for MK differentiation.MethodsThe PCR array was performed using cDNAs derived from RepID-proficient or RepID-deficient K562 erythroleukemia cell lines. Correlation between RepID and DAB2 expression was examined in the Cancer Cell Line Encyclopedia (CCLE) through the CellMinerCDB portal. The acceleration of MK differentiation in RepID-deficient K562 cells was determined by estimating cell sizes as well as counting multinucleated cells known as MK phenotypes, and by qRT-PCR analysis to validate transcripts of MK markers using phorbol 12-myristate 13-acetate (PMA)-mediated MK differentiation condition. Interaction between CRL4 and histone methylation modifying enzymes were investigated using BioGRID database, immunoprecipitation and proximity ligation assay. Alterations of expression and chromatin binding affinities of RepID, CRL4 and histone methylation modifying enzymes were investigated using subcellular fractionation followed by immunoblotting. RepID-CRL4-JARID1A-based epigenetic changes on DAB2 promoter were analyzed by chromatin-immunoprecipitation and qPCR analysis.ResultsRepID-deficient K562 cells highly expressing MK markers showed accelerated MKs differentiation exhibiting increases in cell size, lobulated nuclei together with reaching maximum levels of MK marker expression earlier than RepID-proficient K562 cells. Recovery of WD40 domain-containing RepID constructs in RepID-deficient background repressed DAB2 expression. CRL4A formed complex with histone H3K4 demethylase JARID1A in soluble nucleus and loaded to the DAB2 promoter in a RepID-dependent manner during proliferation condition. RepID, CRL4A, and JARID1A were dissociated from the chromatin during MK differentiation, leading to euchromatinization of the DAB2 promoter.ConclusionThis study uncovered a role for the RepID-CRL4A-JARID1A pathway in the regulation of gene expression for MK differentiation, which can form the basis for the new therapeutic approaches to induce platelet production.EhctJ7T1-GG5oU5fji2odBVideo

Characterization of K562 cells: uncovering novel chromosomes, assessing transferrin receptor expression, and probing pharmacological therapies.

Human erythroleukemic K562 cells represent the prototypical cell culture model of chronic myeloid leukemia (CML). The cells are pseudo-triploid and positive for the Philadelphia chromosome. Therefore, K562 cells have been widely used for investigating the BCR/ABL1 oncogene and the tyrosine kinase inhibitor, imatinib-mesylate. Further, K562 cells overexpress transferrin receptors (TfR) and have been used as a model for targeting cytotoxic therapies, via receptor-mediated endocytosis. Here, we have characterized K562 cells focusing on the karyotype of cells in prolonged culture, regulation of expression of TfR in wildtype (WT) and doxorubicin-resistant cells, and responses to histone deacetylase inhibition (HDACi). Karyotype analysis indicates novel chromosomes and gene expression analysis suggests a shift of cultured K562 cells away from patient-derived leukemic cells. We confirm the high expression of TfR on K562 cells using immunofluorescence and cell-surface receptor binding radioassays. Importantly, high TfR expression is observed in patient-derived cells, and we highlight the persistent expression of TfR following doxorubicin acquired resistance. Epigenetic analysis indicates that permissive histone acetylation and methylation at the promoter region regulates the transcription of TfR in K562 cells. Finally, we show relatively high expression of HDAC enzymes in K562 cells and demonstrate the chemotoxic effects of HDACi, using the FDA-approved hydroxamic acid, vorinostat. Together with a description of morphology, infrared spectral analysis, and examination of metabolic properties, we provide a comprehensive characterization of K562 cells. Overall, K562 cell culture systems remain widely used for the investigation of novel therapeutics for CML, which is particularly important in cases of imatinib-mesylate resistance.

Acetylation-Mimic Mutation of TRIM28-Lys304 to Gln Attenuates the Interaction with KRAB-Zinc-Finger Proteins and Affects Gene Expression in Leukemic K562 Cells.

TRIM28/KAP1/TIF1β is a crucial epigenetic modifier. Genetic ablation of trim28 is embryonic lethal, although RNAi-mediated knockdown in somatic cells yields viable cells. Reduction in TRIM28 abundance at the cellular or organismal level results in polyphenism. Posttranslational modifications such as phosphorylation and sumoylation have been shown to regulate TRIM28 activity. Moreover, several lysine residues of TRIM28 are subject to acetylation, but how acetylation of TRIM28 affects its functions remains poorly understood. Here, we report that, compared with wild-type TRIM28, the acetylation-mimic mutant TRIM28-K304Q has an altered interaction with Krüppel-associated box zinc-finger proteins (KRAB-ZNFs). The TRIM28-K304Q knock-in cells were created in K562 erythroleukemia cells by CRISPR-Cas9 (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein nuclease 9) gene editing method. Transcriptome analysis revealed that TRIM28-K304Q and TRIM28 knockout K562 cells had similar global gene expression profiles, yet the profiles differed considerably from wild-type K562 cells. The expression levels of embryonic-related globin gene and a platelet cell marker integrin-beta 3 were increased in TRIM28-K304Q mutant cells, indicating the induction of differentiation. In addition to the differentiation-related genes, many zinc-finger-proteins genes and imprinting genes were activated in TRIM28-K304Q cells; they were inhibited by wild-type TRIM28 via binding with KRAB-ZNFs. These results suggest that acetylation/deacetylation of K304 in TRIM28 constitutes a switch for regulating its interaction with KRAB-ZNFs and alters the gene regulation as demonstrated by the acetylation mimic TRIM28-K304Q.

Loss of the mitochondrial protein Abcb10 results in altered arginine metabolism in MEL and K562 cells and nutrient stress signaling through ATF4

Abcb10 is a mitochondrial membrane protein involved in hemoglobinization of red cells. Abcb10 topology and ATPase domain localization suggest it exports a substrate, likely biliverdin, out of mitochondria that is necessary for hemoglobinization. In this study, we generated Abcb10 deletion cell lines in both mouse murine erythroleukemia and human erythroid precursor human myelogenous leukemia (K562) cells to better understand the consequences of Abcb10 loss. Loss of Abcb10 resulted in an inability to hemoglobinize upon differentiation in both K562 and mouse murine erythroleukemia cells with reduced heme and intermediate porphyrins and decreased levels of aminolevulinic acid synthase 2 activity. Metabolomic and transcriptional analyses revealed that Abcb10 loss gave rise to decreased cellular arginine levels, increased transcripts for cationic and neutral amino acid transporters with reduced levels of the citrulline to arginine converting enzymes argininosuccinate synthetase and argininosuccinate lyase. The reduced arginine levels in Abcb10-null cells gave rise to decreased proliferative capacity. Arginine supplementation improved both Abcb10-null proliferation and hemoglobinization upon differentiation. Abcb10-null cells showed increased phosphorylation of eukaryotic translation initiation factor 2 subunit alpha, increased expression of nutrient sensing transcription factor ATF4 and downstream targets DNA damage inducible transcript 3 (Chop), ChaC glutathione specific gamma-glutamylcyclotransferase 1 (Chac1), and arginyl-tRNA synthetase 1 (Rars). These results suggest that when the Abcb10 substrate is trapped in the mitochondria, the nutrient sensing machinery is turned on remodeling transcription to block protein synthesis necessary for proliferation and hemoglobin biosynthesis in erythroid models.

Broad histone H4 monomethylation marks expressed genes involved in translation.

H4K20me1 (histone H4 monomethylated at lysine 20) generally has a broad distribution along genes and has been reported to be associated with expressed and repressed genes. In contrast, H3K4me3 (histone H3 trimethylated at lysine 4) is positioned as a narrow peak at the 5' end of most expressed genes in vertebrate cells. A small population of genes involved in cell identity has H3K4me3 distributed throughout the gene body. In this report, we show that H4K20me1 is associated with expressed genes in estrogen receptor-positive breast cancer MCF7 cells and erythroleukemic K562 cells. Further, we identified the genes with the broadest H4K20me1 domains in these two cell types. The broad H4K20me1 domain marked gene bodies of expressed genes, but not the promoter or enhancer regions. The most significant GO term (biological processes) of these genes was cytoplasmic translation. There was little overlap between the genes marked with the broad H4K20me1 domain and those marked with H3K4me3. H4K20me1 and H3K79me2 distributions along expressed gene bodies were similar, suggesting a relationship between the enzymes catalyzing these histone modifications.

Abstract 4040: Asciminib activates erythroid differentiation in K562 cell line

Abstract Background: Asciminib an allosteric tyrosine kinase inhibitor (TKI) was recently approved by the FDA for managing Philadelphia positive chronic myeloid leukemia (CML) patients in chronic phase who had failed to respond to previous TKIs. In this study, we used human erythroleukemic K562 cell line to investigate the role of asciminib as an inducer of erythroid differentiation. Additionally, imatinib, which has previously been reported as a potential inducer of erythroid differentiation, was also tested on these cells, both independently as well as in combination, in order to investigate the degree of erythroid differentiation in a K562 cell line. Methodology: In this study, we investigated the effect of asciminib (5-20nM) with and without imatinib (50-200nM) in differentiating the erythroleukemic cell line K562 towards erythroid lineage. K562 cells were cultured over a 12-day period in basic (IMDM) media and an EPO-based differentiation media to select optimal medium conditions. In addition, an in-vitro drug cytotoxicity experiment (XTT) was used to determine the preliminary toxicity of asciminib with IMDM media and EPO-based differentiation media CD235a and CD71 surface marker expressions were analyzed by flow cytometry at all time-points to determine the degree of differentiation achieved by each of the conditions Moreover, to analyze and identify hemoglobin producing cells ensuing differentiation, benzidine staining was performed at indicated time points. Results: Our results suggest that asciminib, imatinib or a combination of both drugs in EPO-based differentiation media results in efficient erythroid differentiation with high levels of GPA expression (approx. 90%) and significant upregulation of globin genes (p value = 0.0001). These results were further confirmed by benzidine staining, where drug addition and dose escalation significantly increased benzidine-positive cells. Our results also demonstrated that asciminib was able to achieve maximum differentiation at a much earlier time point as compared to imatinib. Moreover, asciminib, when combined with another TKI such as imatinib, can also aid in lowering the drug concentrations being used, hence resulting in lessening the toxicity of the drug when used alone required at high doses. Conclusion: The results from this study highlighted the novel role of asciminib in erythroid differentiation using an in-vitro K562 model that can give high-levels of surface markers and globin expression. Potential clinical application of asciminib in hematological diseases that are associated specifically with a failure in the expression of globin genes should be evaluated. Keywords:K562, erythroid differentiation, asciminib, imatinib, glycophorin A, transferrin receptor, hemoglobin Citation Format: Hammad Hassan, Sarah Yousuf, Syed Muhammad Ahmed, Karim Ruknuddin, Hadiqa Raees, Sadia Habib, Fizza Iftikhar, Afsar Ali Mian, Elnasir Lalani. Asciminib activates erythroid differentiation in K562 cell line. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4040.

Influence of Melatonin Treatment on Cellular Mechanisms of Redox Adaptation in K562 Erythroleukemic Cells

Melatonin (MEL) presents well-documented pleiotropic actions against oxidative stress (OS), acting indirectly through activation of transcription factors, e.g., FoxO3 and Nrf2. Thus, this study aimed to investigate the possible modulating effects of MEL on the redox signaling pathways PI3K/AKT/FoxO3 and Keap1/Nrf2/ARE in K562 erythroleukemic cells subjected to OS induction. For this, the viability, and transcript levels of genes involved in redox adaptation were evaluated in K562 cells in different periods of erythroid differentiation: under OS induction by hydrogen peroxide (100 µM H2O2); treated with 1 nM (C1) and 1 mM (C2) MEL; and associated or not with stress induction. We observed a restoration of physiological levels of Nrf2 in both MEL concentrations under OS. The C1 was related to enhanced expression of antioxidant and proteasome genes through the Nrf2-ARE pathway, while C2 to the induction of FOXO3 expression, suggesting an involvement with apoptotic pathway, according to BIM transcript levels. The effects of MEL administration in these cells showed a period and dose-dependent pattern against induced-OS, with direct and indirect actions through different pathways of cellular adaptation, reinforcing the importance of this indolamine in the regulation of cellular homeostasis, being a promising therapeutic alternative for diseases that present an exacerbated OS.

Loss of Cyb5R3 Function Silences Fetal Hemoglobin and Hematocrit Responses to Hydroxyurea in Patients with Sickle Cell Anemia

BACKGROUND: Hydroxyurea (HU) is the first FDA-approved and most widely prescribed drug for sickle cell (SS) patients due to its beneficial effects (decreased Hb polymerization, pain crises and hospitalization) and relative safety profile. While the clinical benefits of HU have been found to associate with increased nitric oxide (NO) and fetal hemoglobin (HbF) in most SS patients, there has been considerable interpatient variability in HbF response to the drug. From this standpoint, HU is imperfectly understood mechanistically. Cytochrome b5 reductase 3 (Cyb5R3), also known as methemoglobin reductase, is an enzyme known to modulate redox signaling in erythrocytes and vascular cells by catalyzing one electron transfer reactions using reduced nicotinamide adenine dinucleotide (NADH) as an electron donor. Functionally, membrane-associated CYB5R3 exerts antioxidant properties by modulating heme iron reduction, plasma membrane coenzyme Q reduction, elongation and unsaturation of fatty acids, cholesterol biosynthesis and drug metabolism, while the soluble form of CYB5R3 reduces red blood cell methemoglobin. Unremitting oxidation of the soluble guanylate cyclase (sGC) heme iron in the absence of sufficient Cyb5R3 activity in vascular smooth muscle has been shown to explain some NO resistance that characterizes pulmonary arterial hypertension and other vasculopathy associated with SCD. More than 40 variants of Cyb5R3 have been identified. Of particular interest is a Cyb5R3 variant (T117S) that contains a threonine to serine substitution in the flavoprotein, which lessens the reductase's activity by roughly 50% compared to wild-type. This variant occurs with high frequency (0.23 minor allele) in persons of African ancestry but is rare (<1%) in all other races. Nothing is known about the role of Cyb5R3 in the anemia of sickle cell disease. We hypothesized that Cyb5R3 may act as a modifier of HbF induction by HU in sickle cell anemia. METHODS: Male and female SS patients (n=633, 12-70 years of age) from the Treatment of Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (walk-PHaSST) trial were recruited for genetic analysis (University of Pittsburgh IRB Protocol Study 19060255). Genotyping of rs1800457 (T117S SNP) was performed using Taqman genotyping assay. One-way ANOVA and Holms Sidak were used for multiple comparisons of HbF levels by Cyb5R3 genotype and HU treatment status. Intrapatient correlation analyses of HbF and hematocrit (HCT) were conducted using Pearsons r. RESULTS: Comparisons of HbF levels by Cyb5R3 genotype (CC, wild-type; CG, heterozygous wild-type and T117S; GG, homozygous T117S) and HU treatment status (treated vs. untreated) at time of study enrollment (baseline) show that HU is a less potent HbF inducer in the GG group (4.32 mean diff, P=0.344) versus the CC and CG patient groups (CC: 6.027 mean diff, P<0.0001 and CG: 6.914 mean diff, P<0.0001). Correlation analyses showed that as HbF levels increased among HU-untreated patients, the trend was for HCT to decrease. This was true for all SS patients, irrespective of Cyb5R3 genotype (CC: r = -0.336, P<0.0001, n=320; CG: r = -0.437 P<0.0001, n=120; GG: r = -0.253, P=0.136, n=36). However, with HU therapy, the inverse relationship between HbF and HCT was less negative in SS patients carrying at least one copy of the wild-type Cyb5R3 gene (CC or CG). In these individuals, increasing levels of HbF (up to 10%) correlated with positive gains in HCT at HbF greater than 5-6% (CC: r = -0.161, P=0.097, n=107) and 6-7% (CG: r = -0.186, P=0.25, n=40). In patients homozygous for T117S, HCT continued trending downward as HbF increased (GG: r = -0.419, P=0.228, n=10). These data indicate that the positive relationship between HbF and HCT is subject to uncoupling by loss of Cyb5R3 function. In vitro studies with human erythroleukemic K562 cells reveal loss of gamma globin induction by HU treatment when wild-type Cyb5R3 is knocked down by siRNA, indicating a requirement for Cyb5R3 in HU-stimulated HbF induction. SUMMARY andCONCLUSION: Loss of Cyb5R3 activity negatively impacts HbF and HCT in HU treated SS patients. We conclude that the T117S variant may be a useful marker for predicting which SS patients will incur beneficial HbF and HCT responses to HU, thereby improving clinical decision-making about best drug choices for preventing HbS polymerization and treating anemia in SS patients.

Synthetic flavagline derivative 1-chloroacetylrocaglaol promotes apoptosis in K562 erythroleukemia cells through miR-17-92 cluster genes.

Chronic myeloid leukemia accounts for human deaths worldwide and could enhance sevenfold by 2050. Thus, the treatment regimen for this disorder is highly crucial at this time. Flavaglines are a natural class of cyclopentane benzofurans exhibiting various bioactivities like anticancer action. Despite the antiproliferative activity of flavaglines against diverse cancer cells, their roles and mechanism of action in chronic myeloid leukemia (CML) remain poorly understood. Thus, this study examines the antiproliferative effect of a newly synthesized flavagline derivative, 1-chloracetylrocaglaol (A2074), on erythroleukemia K562 cells and the zebrafish xenograft model. The study revealed that A2074 could inhibit proliferation, promote apoptosis, and boost megakaryocyte differentiation of K562 cells. This flavagline downregulated c-MYC and miR-17-92 cluster genes, targeting upregulation of the apoptotic protein Bcl-2-likeprotein11(BIM). The work uncovered a critical role of the c-MYC-miR-17-92-BIM axis in the growth and survival of CML cells.

Enhancing the biological properties of zinc complexes with bis(indolyl)methane groups: Synthesis, characterization, DNA interaction, and biocide activity

The unprecedented mononucleated ligand (6,6-di(1H-indol-3-yl)-N,N-bis(pyridin-2-ylmethyl)hexan-1-amine (LC5) with an N3-donor set and its complexes [Zn(LC5)Cl2] • 2CH3OH (1) and [Zn(LC5)2](ClO4)2 (2), were successfully prepared. All compounds were fully characterized by a suite of physicochemical methods. Fluid 1H and 13C NMR spectroscopy, as well as DFT and TD-DFT calculations, were carried out to propose a viable structural arrangement for both complexes. The interaction between these compounds and DNA was monitored in the UV region where binding constants (Kb) were estimated (2 > 1 > LC5). These data were corroborated by DNA cleavage assays using groove binders, circular dichroism, and docking studies. Both complexes confirmed their biocide activity against selected microorganisms: Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, the filamentous fungi A. fumigatus and S. cerevisiae. Finally, the cytotoxic activities of 1 and 2 were tested against the erythroleukemia K562 cell line. For all biological studies, it was probed that the presence of the indole moieties and the zinc atoms in the chemical composition of the complexes studied could increase the magnitude of the activity following the order: 2 > 1 > LC5, where a linear relationship between the biological activity upon K562 cells (IC50) and DNA binding studies (Kb) was found.

Biological Role of the Intercellular Transfer of Glycosylphosphatidylinositol-Anchored Proteins: Stimulation of Lipid and Glycogen Synthesis.

Glycosylphosphatidylinositol-anchored proteins (GPI-APs), which are anchored at the outer leaflet of plasma membranes (PM) only by a carboxy-terminal GPI glycolipid, are known to fulfill multiple enzymic and receptor functions at the cell surface. Previous studies revealed that full-length GPI-APs with the complete GPI anchor attached can be released from and inserted into PMs in vitro. Moreover, full-length GPI-APs were recovered from serum, dependent on the age and metabolic state of rats and humans. Here, the possibility of intercellular control of metabolism by the intercellular transfer of GPI-APs was studied. Mutant K562 erythroleukemia (EL) cells, mannosamine-treated human adipocytes and methyl-ß-cyclodextrin-treated rat adipocytes as acceptor cells for GPI-APs, based on their impaired PM expression of GPI-APs, were incubated with full-length GPI-APs, prepared from rat adipocytes and embedded in micelle-like complexes, or with EL cells and human adipocytes with normal expression of GPI-APs as donor cells in transwell co-cultures. Increases in the amounts of full-length GPI-APs at the PM of acceptor cells as a measure of their transfer was assayed by chip-based sensing. Both experimental setups supported both the transfer and upregulation of glycogen (EL cells) and lipid (adipocytes) synthesis. These were all diminished by serum, serum GPI-specific phospholipase D, albumin, active bacterial PI-specific phospholipase C or depletion of total GPI-APs from the culture medium. Serum inhibition of both transfer and glycogen/lipid synthesis was counteracted by synthetic phosphoinositolglycans (PIGs), which closely resemble the structure of the GPI glycan core and caused dissociation of GPI-APs from serum proteins. Finally, large, heavily lipid-loaded donor and small, slightly lipid-loaded acceptor adipocytes were most effective in stimulating transfer and lipid synthesis. In conclusion, full-length GPI-APs can be transferred between adipocytes or between blood cells as well as between these cell types. Transfer and the resulting stimulation of lipid and glycogen synthesis, respectively, are downregulated by serum proteins and upregulated by PIGs. These findings argue for the (patho)physiological relevance of the intercellular transfer of GPI-APs in general and its role in the paracrine vs. endocrine (dys)regulation of metabolism, in particular. Moreover, they raise the possibility of the use of full-length GPI-APs as therapeutics for metabolic diseases.

Inflammation Promotes Oxidative and Nitrosative Stress in Chronic Myelogenous Leukemia

Chronic inflammation is characterized by the production of reactive oxygen species (ROS), reactive nitrogen species, and inflammatory cytokines in myeloproliferative neoplasms (MPNs). In addition to these parameters, the aim of this study was to analyze the influence of ROS on the proliferation-related AKT/mTOR signaling pathway and the relationship with inflammatory factors in chronic myelogenous leukemia (CML). The activity of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase is reduced in erythrocytes while levels of the oxidative stress markers malondialdehyde and protein carbonyl are elevated in the plasma of patients with CML. In addition, nitrogen species (nitrotyrosine, iNOS, eNOS) and inflammation markers (IL-6, NFkB, and S100 protein) were increased in granulocytes of CML while anti-inflammatory levels of IL-10 were decreased in plasma. CML granulocytes exhibited greater resistance to cytotoxic H2O2 activity compared to healthy subjects. Moreover, phosphorylation of the apoptotic p53 protein was reduced while the activity of the AKT/mTOR signaling pathway was increased, which was further enhanced by oxidative stress (H2O2) in granulocytes and erythroleukemic K562 cells. IL-6 caused oxidative stress and DNA damage that was mitigated using antioxidant or inhibition of inflammatory NFkB transcription factor in K562 cells. We demonstrated the presence of oxidative and nitrosative stress in CML, with the former mediated by AKT/mTOR signaling and stimulated by inflammation.

GAPDH is involved in the heme‐maturation of myoglobin and hemoglobin

GAPDH, a heme chaperone, has been previously implicated in the incorporation of heme into iNOS and soluble guanylyl cyclase (sGC). Since sGC is critical for myoglobin (Mb) heme-maturation, we investigated the role of GAPDH in the maturation of this globin, as well as hemoglobins α, β, and γ. Utilizing cell culture systems, we found that overexpression of wild-type GAPDH increased, whereas GAPDH mutants H53A and K227A decreased, the heme content of Mb and Hbα and Hbβ. Overexpression of wild-type GAPDH fully recovered the heme-maturation inhibition observed with the GAPDH mutants. Partial rescue was observed by overexpression of sGCβ1 but not by overexpression of a sGCΔβ1 deletion mutant, which is unable to bind the sGCα1 subunit required to form the active sGCα1β1 complex. Wild type and mutant GAPDH was found to be associated in a complex with each of the globins and Hsp90. GAPDH at endogenous levels was found to be associated with Mb in differentiating C2C12 myoblasts, and with Hbγ or Hbα in differentiating HiDEP-1 erythroid progenitor cells. Knockdown of GAPDH in C2C12 cells suppressed Mb heme-maturation. GAPDH knockdown in K562 erythroleukemia cells suppressed Hbα and Hbγ heme-maturation as well as Hb dimerization. Globin heme incorporation was not only dependent on elevated sGCα1β1 heterodimer formation, but also influenced by iron provision and magnitude of expression of GAPDH, d-aminolevulinic acid, and FLVCR1b. Together, our data support an important role for GAPDH in the maturation of myoglobin and γ, β, and α hemoglobins.