Acute Myeloid Leukemia Cells Research Articles

Increased local DNA methylation disorder in AMLs with DNMT3A-destabilizing variants and its clinical implication

The mechanistic link between the complex mutational landscape of de novo methyltransferase DNMT3A and the pathology of acute myeloid leukemia (AML) has not been clearly elucidated so far. Motivated by a recent discovery of the significance of DNMT3A-destabilizing mutations (DNMT3AINS) in AML, we here investigate the common characteristics of DNMT3AINS AML methylomes through computational analyses. We present that methylomes of DNMT3AINS AMLs are considerably different from those of DNMT3AR882 AMLs in that they exhibit increased intratumor DNA methylation heterogeneity in bivalent chromatin domains. This epigenetic heterogeneity was associated with the transcriptional variability of developmental and membrane-associated factors shaping stem cell niche, and also was a predictor of the response of AML cells to hypomethylating agents, implying that the survival of AML cells depends on stochastic DNA methylations at bivalent domains. Altogether, our work provides a novel mechanistic model suggesting the genomic origin of the aberrant epigenomic heterogeneity in disease conditions.

Comprehensive analysis of DNA methylation and gene expression to identify tumor suppressor genes reactivated by MLN4924 in acute myeloid leukemia.

This study investigated whether the neddylation inhibitor MLN4924 induces aberrant DNA methylation patterns in acute myeloid leukemia and contributes to the reactivation of tumor suppressor genes. DNA methylation profiles of Kasumi-1 and KU812 acute myeloid leukemia cell lines before and after MLN4924 treatment were generated using the 850K Methylation BeadChip. RNA sequencing was used to obtain transcriptomic profiles of Kasumi-1 cells. Target genes were identified through a combined analysis of methylation and transcriptome data. Methylation-specific PCR and quantitative PCR validated the changes in methylation and expression. Prognostic analysis of target genes was performed using databases, and Pearson correlation was used to examine the relationship between methylation and expression levels. In Kasumi-1 and KU812 cells, 301 and 469 differentially methylated sites, respectively, were identified. A total of 4310 differential expression genes were detected in Kasumi-1. Combined analysis revealed that TRIM58 exhibited significant demethylation and upregulation after MLN4924 treatment, as confirmed by quantitative and methylation-specific PCR. Furthermore, database analysis revealed that both down-expression and promoter hypermethylation of TRIM58 were correlated with poor prognosis in acute myeloid leukemia. A negative correlation was observed between TRIM58 methylation and expression levels. This study suggests that MLN4924 alters DNA methylation patterns in acute myeloid leukemia and reactivates TRIM58, a potential tumor suppressor gene, through demethylation.

Recipient sex and donor leukemic cell characteristics determine leukemogenesis in patient-derived models.

In acute myeloid leukemia (AML), leukemogenesis depends on cell-intrinsic genetic aberrations and thus, studies on AML require investigations in an in vivo setting as provided by patient derived xenografts (PDX) models. Here we report that, next to leukemic cell characteristics, recipient sex highly influences the outgrowth of AML cells in PDX models, with females being much better repopulated than males in primary as well as secondary transplantation assays. Testosterone may be the more important player since, strikingly, better engraftment was seen in castrated versus control male recipients, while ovariectomy did not significantly impair engraftment in females. Shorter time-to-engraftment and mouse survival were observed with adverse molecular risk, and respectively with high FLT3-ITD ratio mutated AML cells. Adverse risk AML furthermore showed higher percentages of phenotypic leukemic stem cells (LSCs), suggesting impaired differentiation capacity in these AML subtypes. Overall, we achieved successful repopulation with 14/23 (61%) favorable, 18/30 (60%) intermediate and 4/8 (50%) adverse risk AML cases in female recipient PDX models. Our data identify recipient sex as an important experimental confounder in leukemia PDX models, and the contribution of the sex hormones to leukemogenesis as an intriguing, underexplored research area.

IRE1α-XBP1 safeguards hematopoietic stem and progenitor cells by restricting pro-leukemogenic gene programs.

Hematopoietic stem cells must mitigate myriad stressors throughout their lifetime to ensure normal blood cell generation. Here, we uncover unfolded protein response stress sensor inositol-requiring enzyme-1α (IRE1α) signaling in hematopoietic stem and progenitor cells (HSPCs) as a safeguard against myeloid leukemogenesis. Activated in part by an NADPH oxidase-2 mechanism, IRE1α-induced X-box binding protein-1 (XBP1) mediated repression of pro-leukemogenic programs exemplified by the Wnt-β-catenin pathway. Transcriptome analysis and genome-wide mapping of XBP1 targets in HSPCs identified an '18-gene signature' of XBP1-repressed β-catenin targets that were highly expressed in acute myeloid leukemia (AML) cases with worse prognosis. Accordingly, IRE1α deficiency cooperated with a myeloproliferative oncogene in HSPCs to cause a lethal AML in mice, while genetic induction of XBP1 suppressed the leukemia stem cell program and activity of patient-derived AML cells. Thus, IRE1α-XBP1 signaling safeguards the integrity of the blood system by restricting pro-leukemogenic programs in HSPCs.

Valproic Acid Enhances Venetoclax Efficacy in Targeting Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a common and aggressive form of leukemia, yet current treatment strategies remain insufficient. Venetoclax, a BH3-mimetic approved for AML treatment, induces Bcl-2-dependent apoptosis, though its therapeutic efficacy is still limited. Therefore, new strategies to enhance the effect of venetoclax are highly sought. Valproic acid (VPA), commonly used for epilepsy, has also been studied for potential applications in AML treatment. AML cells were treated with venetoclax, with or without VPA. Cell viability was assessed using the trypan blue dye exclusion assay, while cell cycle progression was analyzed by flow cytometry. The expression of pro-apoptotic proteins Bax and Bak was measured by RT-qPCR. Venetoclax and VPA individually had only mild effects on AML cell proliferation. However, their combination significantly inhibited cell growth and triggered pronounced cell death. This combination also led to the cleavage of poly (ADP-ribose) polymerase (PARP), a substrate of caspases, indicating activation of apoptosis. VPA treatment upregulated the expression of Bax and Bak, further supporting apoptosis induction. The cell death induced by the venetoclax-VPA combination was predominantly apoptotic, as confirmed by the near-complete blockade of cell death by a pan-caspase inhibitor. Our study demonstrates that VPA enhances venetoclax-induced apoptosis in AML cell lines, providing a novel role for VPA and suggesting a promising combinatory strategy for AML treatment. These findings offer valuable insights into potential clinical applications of venetoclax and VPA in AML management.

NACC1 accelerates the progression of AML by regulating the ADAM9/PI3K/AKT axis.

Nucleus accumbens-associated protein 1 (NACC1) regulates various types of biological processes. It is a transcription factor associated with cancer. NACC1 is overexpressed in many human malignancies and can regulate the progression, metastasis, and drug resistance of cancer cells. However, its precise role in acute myeloid leukemia (AML) remains unknown. This study aimed to unravel the basic mechanism of NACC1 in AML. Our findings demonstrated that NACC1 is immensely expressed in AML cells. Lentiviral vector-mediated knockdown of NACC1 inhibited the PI3K/AKT signaling pathway. Simultaneously, NACC1 knockdown promoted apoptosis, suppressed the proliferative capacity of AML cells, and resulted in cell cycle arrest during the G0/G1 phase. Additionally, A disintegrin and metalloproteinase 9 (ADAM9) was markedly expressed in AML cells. NACC1 regulated ADAM9 expression. ADAM9 expression was also downregulated after NACC1 knockdown. Concurrently, ADAM9 knockdown affected the activity of AML cells by decelerating the growth rate, promoting apoptosis, and blocking cell cycle progression. In addition, the AKT activator SC79 restored the inhibited cell proliferation after NACC1 knockdown and ADAM9 knockdown. In conclusion, our study suggested that the NACC1/ADAM9/PI3K/AKT axis is crucial for sustaining the survival of AML cells, indicating that NACC1 may be a viable target for treating AML.

A Novel In Vitro Model of the Bone Marrow Microenvironment in Acute Myeloid Leukemia Identifies CD44 and Focal Adhesion Kinase as Therapeutic Targets to Reverse Cell Adhesion-Mediated Drug Resistance.

Acute myeloid leukemia (AML) is an aggressive neoplasm. Although most patients respond to induction therapy, they commonly relapse due to recurrent disease in the bone marrow microenvironment (BMME). So, the disruption of the BMME, releasing tumor cells into the peripheral circulation, has therapeutic potential. Using both primary donor AML cells and cell lines, we developed an in vitro co-culture model of the AML BMME. We used this model to identify the most effective agent(s) to block AML cell adherence and reverse adhesion-mediated treatment resistance. We identified that anti-CD44 treatment significantly increased the efficacy of cytarabine. However, some AML cells remained adhered, and transcriptional analysis identified focal adhesion kinase (FAK) signaling as a contributing factor; the adhered cells showed elevated FAK phosphorylation that was reduced by the FAK inhibitor, defactinib. Importantly, we demonstrated that anti-CD44 and defactinib were highly synergistic at diminishing the adhesion of the most primitive CD34high AML cells in primary autologous co-cultures. Taken together, we identified anti-CD44 and defactinib as a promising therapeutic combination to release AML cells from the chemoprotective AML BMME. As anti-CD44 is already available as a recombinant humanized monoclonal antibody, the combination of this agent with defactinib could be rapidly tested in AML clinical trials.

FLT3 inhibitors induce p53 instability, driven by STAT5/MDM2/p53 competitive interactions in acute myeloid leukemia.

FLT3 mutations are present in one third of patients with Acute myeloid leukemia (AML) and stand as an attractive therapeutic target. Although FLT3 inhibitors demonstrate clinical efficacy, the drug resistance remains challenging attributed to multiple mechanisms. In this study, we found that tyrosine kinase inhibitors (TKIs) targeting FLT3 prompt p53 degradation in AML cells with FLT3-ITD through ubiquitination. STAT5 phosphorylation facilitates its nuclear localization, leading to competitive interactions among STAT5, MDM2, and p53. TKIs blocked STAT5 nuclear entry, amplifying MDM2/p53 binding and subsequent p53 degradation. Additionally, STAT5 overexpression inhibited MDM2-mediated p53 ubiquitination, whereas knock-down of STAT5 destabilizes p53. Co-administration of MDM2 inhibitors stabilizes p53 ubiquitination induced by TKIs, enhancing pro-apoptotic effects on AML cells. Moreover, in mice engrafted with AML cells, gilteritinib treatment results in decreased p53 protein levels and the transcriptional repression of downstream genes in leukemia cells, which are mitigated by the co-administration of MDM2 inhibitors. In conclusion, our study shows that FLT3 TKIs impede STAT5 nuclear translocation, strengthening p53/MDM2 interaction and consequent p53 degradation. This finding reveals a novel mechanism of TKIs resistance and indicates a combination of MDM2 inhibitors with TKIs for AML therapy, offering new insights into effective treatment strategies.

FT538, iPSC-derived NK cells, enhance AML cell killing when combined with chemotherapy.

Induced pluripotent stem cell (iPSC)-derived natural killer (NK) cells offer an opportunity for a standardized, off-the-shelf treatment with the potential to treat a wider population of acute myeloid leukaemia (AML) patients than the current standard of care. FT538 iPSC-NKs express a high-affinity, noncleavable CD16 to maximize antibody dependent cellular cytotoxicity, a CD38 knockout to improve metabolic fitness, and an IL-15/IL-15 receptor fusion preventing the need for cytokine administration, the main source of adverse effects in NK cell-based therapies. Here, we sought to evaluate the potential of FT538 iPSC-NKs as a therapy for AML through their effect on AML cell lines and primary AML cells. We observed that FT538 iPSC-NKs induce effector-to-target cell ratio dependent apoptosis in cell lines and primary AML cells, including cells from high-risk patients. Flow cytometric analysis revealed that FT538 iPSC-NKs induce AML cell death when combined with the AML therapies: cytarabine, venetoclax and gilteritinib. Moreover, cytarabine did not affect FT538 iPSC-NK viability, suggesting that iPSC-derived NK therapies and chemotherapy may be a promising treatment combination. This study provides the basis for further study of iPSC-derived NK cell therapies as a treatment option for high-risk AML patients, particularly those with disease resistant to standard therapies.

LncRNA SNHG5 induces CAFs-like phenotype and autophagy of AML-MSCs via PTBP1/ATG5 axis to confer chemoresistance of AML cells.

Acute myeloid leukemia (AML) is still a threaten to human health due to its high occurrence and poor prognosis. Mesenchymal stem cells (MSCs) in bone marrow microenvironment (BMM) play a critical role in the development of AML. This study elucidated the interaction between MSCs and AML cells and its underlying mechanism. MSCs were isolated, identified, and co-cultured with AML cells. qRT-PCR, Western blotting and immunofluorescence were used to determine molecule expression. Cell viability and apoptosis were determined by CCK-8 and flow cytometry. Exosomes were isolated and characterized, and PKH26 was used for monitoring exosome internalization. RNA-FISH was used to determine the localization of SNHG5. RIP, RNA-pull down and ChIP assays were used to evaluate the molecular interaction. SNHG5 expression was up-regulated and positively correlated with cancer-associated fibroblasts (CAFs)-related biomarkers in MSCs. AML cells-derived exosomes delivered SNHG5 to enhance its expression in MSCs. SNHG5 overexpression induced CAFs-like phenotype and autophagy in MSCs that led to daunorubicin resistance of AML cells. Mechanistically, SNHG5 stabilized autophagy related 5 (ATG5) mRNA by interaction with polypyrimidine tract-binding protein 1 (PTBP1). AML cells-derived exosomal lncRNA SNHG5 triggered CAFs-like phenotype and autophagy of AML-MSCs via interaction with PTBP1 to increase ATG5 mRNA stability, thereby leading to chemoresistance of AML cells.

Unveiling the link between NADPH oxidase 2 activation and mitochondrial superoxide formation in leukemic cell killing induced by arsenic trioxide.

This study focused on the interplay between NADPH oxidase 2 (NOX 2) activation and mitochondrial superoxide (mitoO2.-) formation induced by clinically relevant concentrations of arsenic trioxide (ATO; As2O3) in acute promyelocytic leukemia (APL) cells. Carefully controlled inhibitor studies and small interfering RNA mediated downregulation of p47phox (a component of the NOX 2 complex) expression demonstrated that, in an APL cell line, ATO promotes upstream NOX 2 activation critically connected with the formation of mitoO2.- and with the ensuing mitochondrial permeability transition (MPT)-dependent apoptosis. Instead, acute myeloid leukemia (AML) cell lines respond to ATO with low NOX 2 activation, resulting in a state that is non-permissive for mitoO2.- formation. Consistently, through rescue experiments, we demonstrate that pharmacological stimulation of NOX 2 overcomes resistance in these cells, thereby initiating the same cascade of downstream events observed in APL cells. As a final note, several lines of evidence, including measurement of glutathione, catalase and glutathione peroxidase levels, indicated that the antioxidant machinery was similar in APL and AML cells. The results regarding nuclear factor erythroid 2 p45-related factor 2-dependent antioxidant responses were instead of more complex interpretation as NB4 cells appeared particularly responsive to ATO. Our findings allow a novel interpretation of the interplay between NOX 2 activation and mitoO2.- formation induced by ATO, ultimately steering leukemic cells towards MPT-dependent apoptosis. These mechanistic insights provide a rationale for the disparate responses of APL and AML cells to ATO, offering potential avenues for the development of therapeutic intervention tailored to specific leukemia subtypes.

C-JUN interacts with HDAC1 as a potential combinatorial therapeutic target in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a biologically heterogeneous disease originating from the clonal expansion of hematopoietic stem cells (HSCs). Clonal expansion of hematopoietic stem cell progenitors (HSC-Prog), along with a block in differentiation, are hallmark features of AML. The disease is characterized by poor clinical outcomes, highlighting the urgent need for effective therapeutic strategies and suitable drug targets. We conducted multi-omics analyses, including single-cell RNA sequencing (scRNA-seq), Mendelian randomization (MR), and bulk RNA-seq, to investigate HDAC1's oncogenic role in AML. We identified specific gene signatures at the single-cell level. MR with eQTL data established causal links, and TCGA-LAML RNA-seq provided prognostic insights. Analysis of cellular communication and transcription factors revealed high c-JUN activity in HSC-Prog. We confirmed the association of c-JUN with HDAC1 through Western blotting and Co-immunoprecipitation (Co-IP). Functional validation of c-JUN in AML cells was performed via flow cytometry in vitro. The effectiveness of drugs targeting c-JUN and HDAC1 was assessed in mouse models using live imaging methods like in vivo imaging system (IVIS) and iSMAART. We identified the activity of c-JUN is specifically enhanced in HSC-Prog in AML patients. We suggest a potential regulatory relationship between c-JUN and HDAC1 in AML tumor cells. Inhibition of c-JUN can suppress cell proliferation and CD33 expression in AML, enhancing susceptibility to natural killer (NK) cell-mediated cytotoxicity. The combination of agents targeting c-JUN (Ailanthone) and HDAC1 (Panobinostat) showed robust efficacy in treating AML in xenograft mouse models, outperforming monotherapy. We also observed that the combination of Ailanthone and Panobinostat therapy displayed a safe pharmacological profile without dose-dependent toxicity, suggesting its potential as a therapeutic strategy.

Genetically reprogrammed exosomes for immunotherapy of acute myeloid leukemia.

Current treatments for acute myeloid leukemia (AML) remain challenging and are characterized by poor clinical outcomes. Exosomes, cell-derived membranous vesicles, have been emerging as a new modality of therapy. Here, we designed and generated genetically reprogrammed exosomes with surface-displayed antibodies and immunoregulatory proteins, namely programmed immune-engaging exosomes (PRIME Exos). By simultaneously targeting Tcells and AML cells expressing C-type lectin-like molecule-1 (CLL-1), PRIME Exos can elicit tumor-specific immune responses and sustain cellular immunity against AML by modulating programmed death 1 (PD-1)- and CD27-mediated immune checkpoint pathways. In preclinical models of AML, PRIME Exos have shown promising efficacy and safety for suppressing leukemia expansion. This study developed a new exosome-based approach for AML immunotherapy.

Overcoming CD226-related immune evasion in acute myeloid leukemia with CD38 CAR-engineered NK cells.

CD226 plays a vital role in natural killer (NK) cell cytotoxicity, interacting with its ligands CD112 and CD155 to initiate immune synapse formation, primarily through leukocyte function-associated-1 (LFA-1). Our study examined the role of CD226 in NK cell surveillance of acute myeloid leukemia (AML). NK cells in patients with AML had lower expression of CD226. CRISPR-Cas9 deletion of CD226 led to reduced LFA-1 recruitment, poor synapse formation, and decreased NK cell anti-leukemic activity. Engineering NK cells to express a chimeric antigen receptor targeting the AML antigen CD38 (CAR38) could overcome the need for CD226 to establish strong immune synapses. LFA-1 blockade reduced CAR38 NK cell activity, and this depended on the CD38 expression levels of AML cells. This suggests parallel but potentially cooperative roles for LFA-1 and CAR38 in synapse formation. Our findings suggest that CAR38 NK cells could be an effective therapeutic strategy to overcome CD226-mediated immune evasion in AML.

Targeting FMS-like tyrosine kinase 3 (FLT3) in acute myeloid leukemia: Novel molecular approaches and therapeutic challenges.

Acute myeloid leukemia (AML), a heterogeneous hematologic malignancy, has generally a poor prognosis despite the recent advancements in diagnostics and treatment. Genetic instability, particularly mutations in the FMS-like tyrosine kinase 3 (FLT3) gene, is associated with severe outcomes. Approximately 30 % of AML patients harbor FLT3 mutations, which have been linked to higher relapse and reduced survival rates. Traditional AML treatments employ cytarabine and anthracyclines drugs. Furthermore, the development of FLT3 inhibitors has significantly improved therapy for FLT3-mutated AML patients. For example, the introduction of midostaurin, the first FLT3 inhibitor, improved patient outcomes. However, resistant AML cell clones continue to pose a challenge to the success of AML treatment.This review discusses FLT3 kinase, mutations, and role in AML pathogenesis. It explores the molecular mechanisms of FLT3 activation, signaling pathways, and the structure and function of the FLT3 receptor. Current and emerging therapeutic approaches are presented, while highlighting the latest FLT3 inhibitors in clinical use, and strategies to overcome drug resistance. Future directions, including personalized therapies and novel drug designs, are examined to provide updated insights into FLT3-targeted treatments. This comprehensive review aims to guide clinicians and researchers in the development of innovative therapies to improve AML patient outcomes.

Functionalized regioisomers of the natural product phenazines myxin and iodinin as potent inhibitors of Mycobacterium tuberculosis and human acute myeloid leukemia cells.

The natural bioactive products myxin and iodinin are phenazine 5,10-dioxides possessing potent anti-bacterial and anti-cancer activity in vitro. This work describes the synthesis and derivatization of new myxin and iodinin regioisomers, developed from 1,3-dihydroxyphenazine 5,10-dioxide. Compounds were evaluated for activity towards M. tuberculosis (Mtb) strains, a human AML cell line (MOLM-13), and two non-cancerous mammalian cell lines (NRK and H9c2). Highly potent analogs were developed having IC50 values against MTB down to 20nM and 1.4μM for human AML cells. 1-OH-3-O-alkyl substituted derivatives demonstrated high efficacy against Mtb and low toxicity in normal cells. 2,3-substituted regioisomers of myxin and iodinin were shown to be inactive, highlighting the importance of oxygen substituent in position 1 of the scaffold. A strong positive correlation between anti-MTB and anti-AML activity was revealed, suggesting a common mechanism of action in bacteria and cancer cells. These findings demonstrate the therapeutic potential of 1,3-O-functionalized phenazine 5,10-dioxides in chemotherapy for Mtb and AML and contribute to the structure-activity understanding of phenazine 5,10-dioxides with respect to their biological activity.

Downregulation of immune checkpoints in acute myeloid leukemia cell lines by Akt inhibitors

Downregulation of immune checkpoints in acute myeloid leukemia cell lines by Akt inhibitors

GANT61 surmounts drug resistance of ADR by upregulating lysosome activities and reducing BCL2 expression in HL-60/ADR cells

BackgroundDrug resistance remains a significant obstacle to Acute myeloid leukemia (AML) successful treatment, often leading to therapeutic failure. Our previous studies demonstrated that Glioma-associated oncogene-1 (GLI1) reduces chemotherapy sensitivity and promotes cell proliferation in AML cells. GANT61, an inhibitor of GLI1, emerges as a promising candidate in AML treatment. This study aims to explore the effects of the combination of GANT61 and Adriamycin (ADR) on AML cells resistance and elucidate the mechanisms through which GANT61 may potentiate the sensitivity of AML cells to ADR.MethodsAML cell lines and AML primary cells were studied to evaluate effects and mechanisms of GANT61. Flow cytometry assays were used to verify apoptosis. Cell Counting Kit-8 (CCK-8) and EDU+ staining were used to observe changes in cell viability and the cytotoxic effect to different drugs. The transcriptomic profiles of HL-60/ADR cells with or without GANT61 treatment were compared via RNA-Seq analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses and Gene Set Enrichment Analysis (GSEA) were performed for differentially expressed genes (DEGs) to reveal the underlying mechanisms of GANT61 in AML cells. GLI1, BCL2, Bax protein and mRNA expression levels were assessed by Western blot and Real-time polymerase chain reaction (RT-PCR).ResultsOur studies found that the combination of GANT61 and ADR synergistically inhibits proliferation while enhancing apoptosis in HL-60/ADR cells, and does not significantly exacerbate myelosuppression. Mechanistically, GSEA revealed enrichment of the gene set associated with the KEGG term “Apoptosis” and “Lysosome” in GANT61 treated cells. Meanwhile, “Apoptosis” was identified as the third most relevant pathway enriched by lysosomal DEGs, and BCL2 expression showed a negative correlation with these lysosomal DEGs in AML patients. RT-PCR and Western blot analysis disclosed that GANT61 significantly restrained BCL2 expression in AML cells. Lastly, we proved that venetoclax, a BCL2 inhibitor, co-treatment with GANT61 improved ADR sensitivity in HL-60/ADR cells.ConclusionsGANT61 effectively reversed ADR resistance in HL-60/ADR cells by upregulating lysosome activities and downgrading BCL2 expression, providing a new treatment strategy with acceptable toxicity for AML-resistant patients.

Cell type-specific upregulation of NKG2D ligand MICA in response to APTO253.

One of the most important targets for natural killer (NK) cell-mediated therapy is the induction of natural killer group 2D ligand (NKG2D-L) expression. APTO253 is a small molecule that selectively kills acute myeloid leukemia (AML) cells, and it has been reported that APTO253 can induce Krüppel-like factor 4 (KLF4) expression and downregulate c-MYC expression. Recently, we discovered a novel role of APTO253 in modulating the NK cell response by inducing surface expression of NKG2D-Ls, especially MHC class I polypeptide-related sequence A (MICA), in AML cells. In this study, we extended the research to validate the effect of APTO253 in other cancer cell lines and found that the enhanced expression of NKG2D-Ls in response to APTO253 is limited in a tumor cell-specific manner. Here, we show that MICA induction upon treatment with APTO253 not only varies between ovarian and pancreatic cancer cell lines but also differs in two ovarian cancer cell lines for an unknown reason. Additionally, our data suggest a link between the induced expression of MICA and the regulation of both, KLF4 and c-MYC, which might represent a mechanism underlying the induction of NKG2D-L expression upon treatment with APTO253. These results may contribute to the potential use of APTO253 as a treatment to improve tumor cell-mediated NK cell cytotoxicity in various cancers.

Rapamycin and Niacin combination induces apoptosis and cell cycle arrest through autophagy activation on acute myeloid leukemia cells.

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy caused by disorders in stem cell differentiation and excessive proliferation resulting in clonal expansion of dysfunctional cells called myeloid blasts. The combination of chemotherapeutic agents with natural product-based molecules is promising in the treatment of AML. In this study, we aim to investigate the anti-cancer effect of Rapamycin and Niacin combination on THP-1 and NB4 AML cell lines. The anti-proliferative effects of Rapamycin and Niacin were determined by MTT cell viability assay in a dose- and time-dependent manner. The combination indexes were calculated by isobologram analysis. Furthermore, apoptosis was investigated by Annexin-V/Propidium Iodide(PI) double staining and cell cycle distribution was measured by PI staining. The expression levels of autophagy-related proteins were detected by western blotting. The combination of Rapamycin and Niacin synergistically decreased cell viability of AML cell lines. The combination treatment induced the apoptotic cell population of THP-1 and NB4 by 4.9-fold and 7.3-fold, respectively. In THP-1 cells, the cell cycle was arrested at the G2/M phase by 10% whereas the NB4 cells were accumulated at the G0/G1 phase. The combination treatment decreased Akt and p-Akt expression. Besides, the ATG7 expression was reduced by combination treatment on THP-1 cells. Similarly, the ATG5 level was downregulated in NB4 cells. The level of LC3B-II/LC3B-I, which is an indicator of autophagy flux, was upregulated in THP-1 and NB4 cells. Although further studies are required, the combination of Rapamycin and Niacin combats cell proliferation by inducing cellular apoptosis, cell cycle arrest and autophagy activation.