Current and Future Molecular Targets for Acute Myeloid Leukemia Therapy

The CD33xCD123xCD70 Multispecific CD3-Engaging DARPin MP0533 Induces Selective T Cell-Mediated Killing of AML Leukemic Stem Cells

The prognosis of patients with acute myeloid leukemia (AML) is limited, especially for elderly or unfit patients not eligible for hematopoietic stem cell (HSC) transplantation. The disease is driven by leukemic stem cells (LSCs), which are characterized by clonal heterogeneity and resistance to conventional therapy. These cells are therefore believed to be a major cause of progression and relapse. We designed MP0533, a multispecific CD3-engaging designed ankyrin repeat protein (DARPin) that can simultaneously bind to three antigens on AML cells (CD33, CD123, and CD70), aiming to enable avidity-driven T cell-mediated killing of AML cells coexpressing at least two of the antigens. In vitro, MP0533 induced selective T cell-mediated killing of AML cell lines, as well as patient-derived AML blasts and LSCs, expressing two or more target antigens, while sparing healthy HSCs, blood, and endothelial cells. The higher selectivity also resulted in markedly lower levels of cytokine release in normal human blood compared to single antigen-targeting T-cell engagers. In xenograft AML mice models, MP0533 induced tumor-localized T-cell activation and cytokine release, leading to complete eradication of the tumors while having no systemic adverse effects. These studies show that the multispecific-targeting strategy used with MP0533 holds promise for improved selectivity toward LSCs and efficacy against clonal heterogeneity, potentially bringing a new therapeutic option to this group of patients with a high unmet need. MP0533 is currently being evaluated in a dose-escalation phase 1 study in patients with relapsed or refractory AML (NCT05673057).

Targeting integrins in drug-resistant acute myeloid leukaemia

Acute myeloid leukaemia (AML) continues to have a poor prognosis, warranting new therapeutic strategies. The bone marrow (BM) microenvironment consists of niches that interact with not only normal haematopoietic stem cells (HSC) but also leukaemia cells like AML. There are many adhesion molecules in the BM microenvironment; therein, integrins have been of central interest. AML cells express integrins that bind to ligands in the microenvironment, enabling adhesion of leukaemia cells in the microenvironment, thereby initiating intracellular signalling pathways that are associated with cell migration, cell proliferation, survival, and drug resistance that has been described to mediate cell adhesion-mediated drug resistance (CAM-DR). Identifying and targeting integrins in AML to interrupt interactions with the microenvironment have been pursued as a strategy to overcome CAM-DR. Here, we focus on the BM microenvironment and review the role of integrins in CAM-DR of AML and discuss integrin-targeting strategies. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

SLED1 Promoting Cell Proliferation and Inhibiting Apoptosis in Acute Myeloid Leukemia: a Study

In this study, we aimed to explore long non-coding RNA (lncRNA) sustained low-efficiency dialysis (SLED1) correlated with Bcl-2 apoptosis pathway in acute myeloid leukemia (AML). This study further aimed to determine its role in the regulation of AML progression and its action as a potential biomarker for better prognosis. AML microarray profiles GSE97485 and probe annotation from the Gene Expression Omnibus (GEO) database from the National Center for Biotechnology Information (NCBI) were detected using the GEO2R tool ( http://www.ncbi.nlm.nih.gov/geo/geo2r/ ). The expression of AML was downloaded from the TCGA database ( http://cancergenome.nih.gov/ ). The statistical analysis of the database was processed with R software. Bioinformatic analysis found that lncRNA SLED1 is highly expressed in AML patients and is associated with poor prognosis. We found that the increased SLED1 expression levels in AML were significantly correlated with FAB classification, human race, and age. Our study has shown that upregulation of SLED1 promoted AML cell proliferation and inhibited cell apoptosis in vitro; RNA sequencing showed increased expression of BCL-2 and indicated that SLED1 might promote the development of AML by regulating BCL-2. Our results showed that SLED1 could promote the proliferation and inhibit the apoptosis of AML cells. SLED1 might promote the development of AML by regulating BCL-2, but the mechanism involved in the progression of AML is unclear. SLED1 plays an important role in AML progression, may be applied as a rapid and economical AML prognostic indicator to predict the survival of AML patients, and help guide experiments for potential clinical drag targets.

Expression analysis, clinical significance and potential function of PLXNB2 in acute myeloid leukaemia

BACKGROUND

The overall survival (OS) rate of adult patients suffering from acute myeloid leukaemia (AML) remains unsatisfactory at less than 40%. Current risk stratification systems fail to provide accurate guidelines for precise treatment. Novel biomarkers for predicting prognosis are urgently needed. Plexin B2 (PLXNB2), a functional receptor of angiogenin (ANG), has been found to be aberrantly expressed in multitudinous tumours. We detected overexpression of PLXNB2 mRNA in AML via transcriptome microarray analysis. This study aims to explore the potential role of PLXNB2 as a biomarker of prognosis and a prospective target of AML.

METHODS

qRT‒PCR was conducted to verify the expression of PLXNB2 mRNA in bone marrow mononuclear cells from AML patients. Immunohistochemical and immunofluorescence staining were performed and confirmed increased expression of PLXNB2 protein in AML bone marrow tissues. Data on PLXNB2 expression, prognosis and clinical features were accessed from multiple bioinformatic databases, including The Cancer Genome Atlas (TCGA). Genes coexpressed and correlated with PLXNB2 were identified and analysed in the TCGA AML cohort. Metascape was applied for functional and pathway enrichment analysis of genes related to PLXNB2. Small molecular agents and traditional Chinese medicines potentially targeting genes related to PLXNB2 were screened via the Connectivity Map, TCMSP and HIT databases.

RESULTS

PLXNB2 mRNA and protein levels are higher in AML samples than in normal controls. Overexpression of PLXNB2 is associated with worse OS in AML. Patients with high PLXNB2 expression might benefit more from haematopoietic stem cell transplantation (HSCT) (indicated by prolonged OS) than those with only chemotherapy treatment. Differentially expressed genes between the high and low PLXNB2 expression groups were overlapped with PLXNB2-coexpressed genes, and genes that overlapped were enriched in immune functions, endothelial cell regulation and cell interaction gene sets, indicating the potential function of PLXNB2 in AML. A total of 36 hub genes were identified from the differentially expressed genes, and MRC1, IL10, CD163 and CCL22 had significant prognostic value for AML. Analysis of the connectivity map and traditional agents revealed that honokiol, morphines, triptolide and paeoniflorin could be potential treatment regimens.

CONCLUSIONS

The overexpression of PLXNB2 is an adverse prognostic factor in adult AML patients and could be used as a potential biomarker. PLXNB2 might exert an oncogenic role by modulating immune functions, endothelial cell functions and cell interactions. AML patients with high PLXNB2 expression could benefit more from HSCT.

Optimized multiplex immunofluorescence for the characterization of tumor immune microenvironment in neoplastic paraffin-preserved tissues

The study of neoplastic cells enabled the discovery of important tumor-related biomarkers which resulted in new forms of early diagnosis, therapeutic options, and prognostic markers. Thus, immunofluorescence (IF), a high throughput imaging technology, represents a valuable method that enables the virtual characterization and localization of diverse cell types and targets, preserving tissue architecture and spatial surroundings. IF staining and analysis of formalin-fixed paraffin-embedded (FFPE) tissues are considered a challenge due to several difficulties, such as tissue autofluorescence, non-specific antibody binding, and image acquisition and quality. This study aimed to develop a multiplex-fluorescence staining technique with high-contrast and high-quality multiple-color images to enrich the investigation of important biomarkers. We present a robust optimized multiple-immunofluorescence procedure that reduced sample autofluorescence, enabled the use of simultaneous antibodies on the same sample, and showed super-resolution imaging through precise antigen localization. We illustrated the utility of this powerful method in FFPE neoplastic appendix, lymph node and bone marrow biopsies, and a 3D-coculture system, in which cells are enabled to grow and interact with their surroundings in all 3D dimensions. Our optimized multiple-immunofluorescence method represents a powerful tool for better understanding the complexity of tumor cells, characterizing cell populations and spatial localization, revealing predictive and prognostic biomarkers, and identifying immunologic phenotypes in a single and limited sample. This valuable IF protocol successfully enables tumor microenvironment profiling that could contribute to the study of cellular crosstalk and the niche, and to the identification of predictive biomarkers for neoplasms.

Mesenchymal Stem Cell-Derived Exosomal miRNA-222-3p Increases Th1/Th2 Ratio and Promotes Apoptosis of Acute Myeloid Leukemia Cells

Interferon regulatory factor 2 (IRF2) participates in the differentiation of immune T cells. Bone marrow mesenchymal stem cell (BM-MSC)-derived exosomes can secret mRNA, miRNAs, and proteins to regulate tumor microenvironment. The present study focused on the miRNA/IRF2 axis in regulating Th1/Th2 ratio and cell apoptosis in acute myeloid leukemia (AML). The flow cytometry analysis was performed to examine the Th1/Th2 ratio and AML apoptosis in vivo and in vitro. The contents of Interferon γ (IFN-γ) and Interleukin-4 (IL-4) were measured using enzyme-linked immunosorbent assay. StarBase was used to predict the potential binding site between miR-222-3p and the 3' untranslated region of IRF2. Luciferase reporter assay was applied for validating the combination of miR-222-3p and IRF2. BM-MSC exosomes were successfully isolated. BM-MSC exosomes increased Th1/Th2 ratio and promoted apoptosis of AML cells. Further analysis showed that IRF2 was targeted by miR-222-3p. Overexpression of miR-222-3p promoted Th1/Th2 ratio and AML cell apoptosis. IRF2 partially reversed the effect that is exerted by miR-222-3p on Th1/Th2 ratio and AML cell apoptosis. Overexpression of miR-222-3p promoted Th1/Th2 ratio and caspase 3 expression in vivo. To sum up, miR-222-3p promotes Th1/Th2 ratio and AML cell apoptosis by regulating IRF2 expression, which provided crucial targets for the treatment of AML.

Metastasis Related Epithelial-Mesenchymal Transition Signature Predicts Prognosis and Response to Chemotherapy in Acute Myeloid Leukemia

Background

Acute myeloid leukemia (AML) is a highly heterogenous disease with varying clinical outcomes among patients. Epithelial-mesenchymal transition (EMT) is an important mechanism underlying cancer metastasis and chemotherapy resistance. However, few EMT-based signatures have been established to predict AML prognosis and treatment efficacy.

Methods

By conducting comparative RNA-seq analysis, we discovered the differential expression of EMT genes between AML patients with relapse and those without relapse. Based on the prognostic analysis of the differentially expressed EMT genes, a metastasis-related EMT signature (MEMTs) was constructed. An analysis was conducted on both TARGET and TCGA cohorts to explore the possible association between MEMTs and prognosis in AML. Three separate chemotherapy treatment cohorts were utilized to assess the predictive efficacy of MEMTs for chemotherapy response. In addition, the potential correlation between MEMTs and the tumor microenvironment was also investigated. Finally, random forest analysis and functional experiments were conducted to verify the key MEMTs gene associated with AML metastasis.

Results

Based on expression and prognostic analysis, we constructed MEMTs that include three EMT genes (CDH2, LOX, and COL3A1). Our findings suggested that the MEMTs could act as a prognostic factor for AML patients, and furthermore, it proved to be a predictor of their response to chemotherapy. Specifically, high MEMTs was associated with worse prognosis and poor response to chemotherapy, while low MEMTs was linked to better prognosis and higher response rates. Random forest and functional experiments demonstrate that CDH2 is a key gene promoting leukemia cell metastasis among the three MEMTs genes.

Conclusion

The identification of MEMTs could potentially act as a predictor for the prognosis and the response to chemotherapy in AML patients. Individual tumor evaluation based on MEMTs could provide personalized treatment options for AML patients in the future.

Dual inhibition of CHK1/FLT3 enhances cytotoxicity and overcomes adaptive and acquired resistance in FLT3-ITD acute myeloid leukemia

FLT3 inhibitors (FLT3i) are widely used for the treatment of acute myeloid leukemia (AML), but adaptive and acquired resistance remains a primary challenge. Inhibitors simultaneously blocking adaptive and acquired resistance are highly demanded. Here, we observed the potential of CHK1 inhibitors to synergistically improve the therapeutic effect of FLT3i in FLT3-mutated AML cells. Notably, the combination overcame adaptive resistance. The simultaneous targeting of FLT3 and CHK1 kinases may overcome acquired and adaptive resistance. A dual FLT3/CHK1 inhibitor 30 with a good oral PK profile was identified. Mechanistic studies indicated that 30 inhibited FLT3 and CHK1, downregulated the c-Myc pathway and further activated the p53 pathway. Functional studies showed that 30 was more selective against cells with various FLT3 mutants, overcame adaptive resistance in vitro, and effectively inhibited resistant FLT3-ITD AML in vivo. Moreover, 30 showed favorable druggability without significant blood toxicity or myelosuppression and exhibited a good oral PK profile with a T_1/2 over 12 h in beagles. These findings support the targeting of FLT3 and CHK1 as a novel strategy for overcoming adaptive and acquired resistance to FLT3i therapy in AML and suggest 30 as a potential clinical candidate.

SFXN3 is Associated with Poor Clinical Outcomes and Sensitivity to the Hypomethylating Therapy in Non-M3 Acute Myeloid Leukemia Patients

BACKGROUND

DNA hypermethylation plays a critical role in the occurrence and progression of acute myeloid leukemia (AML). The mitochondrial serine transporter, SFXN3, is vital for onecarbon metabolism and DNA methylation. However, the impact of SFXN3 on the occurrence and progression of AML has not been reported yet.

OBJECTIVE

In this study, we hypothesized that SFXN3 indicates a poor prognosis and suggested tailored treatment for AML patients.

METHODS

We used GEPIA and TCGA repository data to analyze the expression of SFXN3 and its correlation with survival in AML patients. RT-qPCR was used to detect the SFXN3 level in our enrolled AML patients and volunteers. Additionally, Whole Genome Bisulfite Sequencing (WGBS) was used to detect the genomic methylation level in individuals.

RESULTS

Through the TCGA and GEPIA databases, we found that SFXN3 was enriched in AML patients, predicting shorter survival. Furthermore, we confirmed that SFXN3 was primarily overexpressed in AML patients, especially non-M3 patients, and that high SFXN3 in non-M3 AML patients was found to be associated with poor outcomes and frequent blast cells. Interestingly, non-M3 AML patients with high SFXN3 levels who received hypomethylating therapy showed a higher CR ratio. Finally, we found that SFXN3 could promote DNA methylation at transcription start sites (TSS) in non-M3 AML patients. These sites were found to be clustered in multiple vital cell functions and frequently accompanied by mutations in DNMT3A and NPM1.

CONCLUSION

In conclusion, SXFN3 plays an important role in the progression and hypermethylation in non-M3 AML patients and could be a potential biomarker for indicating a high CR rate for hypomethylating therapy.

Raman spectroscopy differ leukemic cells from their healthy counterparts and screen biomarkers in acute leukemia

Precision medicine is important in the treatment of acute leukemia (AL). The target therapies of AL provide an opportunity to reduce the mortality of AL. How AL cells differ from their healthy counterparts is the basis for the development of therapies and the outcome of AL patients. Therefore, a label-free and noninvasive single-cell Raman platform was used to characterize cell molecular profiles and found potential biomarkers from three healthy people and twelve AL patients with more than 90% accuracy. We analyzed myeloblasts, abnormal promyelocytes, monoblasts and B-ALL cells respectively, compared with their healthy counterparts, which could be distinguished by their intrinsic phenotypic Raman spectra using orthogonal partial least squares discriminate analysis (OPLS-DA). Most importantly, we selected statistically significant markers of the four leukemia models. Further analysis of leukemic granulocytes, we found that a combination of the 1003, 1341 and 1579 cm^-1 Raman peaks could discriminate myeloblasts and abnormal promyelocytes from normal granulocytes. The assignments of 1579 cm^-1 gave us a clue to find potential important variables myeloperoxidase related with AL diagnosis. Our study demonstrates the capability of the Raman platform to characterize leukemia cells with non-invasively probing metabolites. The biomarker we identified could be extensible to other blood cells and potentially have a high impact on leukemia therapy.

Preclinical Evaluation of the Multiple Tyrosine Kinases Inhibitor Anlotinib in Leukemia Stem Cells

Leukemia stem cells (LSCs) constitute the critical barrier to the cure of acute myeloid leukemia (AML) due to their chemoresistance and immune evasion property. Herein, the role of anlotinib, a multiple tyrosine kinase inhibitor, in killing LSCs and regulating chemoresistance and immune evasion was explored. Anlotinib treatment induced apoptosis of LSC-like cells as well as primary AML LSCs, while sparing the normal mononuclear cells in vitro. Moreover, anlotinib could impair the regeneration capacity of LSCs in the patient-derived leukemia xenograft mouse model. Mechanistically, anlotinib inhibited phosphorylation of c-kit, JAK2/STAT3, and STAT5, and downregulated STAT3 and STAT5 expression. In addition, anlotinib downregulated the anti-apoptotic proteins Bcl-2 and Bcl-xL, and upregulated Bax, thereby enhancing the sensitivity of LSCs to idarubicin in vitro. Intriguingly, anlotinib could also partially rescue the interferon-g production of T cells cocultured with LSCs by downregulating PD-L1 expression. In conclusion, anlotinib showed anti-LSC activity and the potential to enhance the sensitivity to idarubicin and inhibit the immunosuppressive feature of LSCs via JAK2/STAT signaling pathway downregulation in the preclinical study. Our results provided a rational basis for combinatory strategies involving anlotinib and chemotherapy or immunotherapy.

MicroRNA-1306-5p Regulates the METTL14-Guided m6A Methylation to Repress Acute Myeloid Leukemia

miRNA and m6A methylation are two key regulators in cancers. However, in acute myeloid leukemia (AML), the relationship of miRNA and m6A methylation remains unclear. The present work is aimed at determining the effect of m6A methylation induced by miRNAs on AML and its underlying mechanism. The expression of METTL14 was detected by qRT-PCR and western blot. The growth of HL-60 cells was analyzed by CCK-8, Transwell assay, and flow cytometry. Tumor-bearing mice were established, and Ki-67 staining assay was used to detect the proliferation in vivo. Dual luciferase reporter system detected the effect of miR-1306-5p on METTL14 luciferase activity. Dot blot analysis detected m6A methylation. We found that METTL14 was upregulated in AML patients and overexpressed METTL14 promoted AML development. Further analysis indicated that METTL14 was directly targeted by miR-1306-5p and overexpressed miR-1306-5p alleviated AML progression. In addition, m6A methylation level regulated by METTL14 could be affected by miR-1306-5p. In conclusion, we found that suppressed miR-1306-5p enhanced AML progression by elevating m6A methylation level via upregulating METTL14. These findings provided basis for the development of new strategies for treating AML.

LINC00998 functions as a novel tumor suppressor in acute myeloid leukemia via regulating the ZFP36 ring finger protein/mammalian target of rapamycin complex 2 axis

Acute myeloid leukemia (AML) is a severe hematologic malignancy that threatens human health. Long non-coding RNA (lncRNA) is emerged as a key player in human cancer. Herein, we explored the role of LINC00998 in human AML. LINC00998 was significantly decreased in human AML, which was linked to relapse and poor prognosis. Stable overexpression of LINC00998 inhibited AML cell viability, colony ability, DNA synthesis rate and increased apoptosis. LINC00998 was mainly located in the cytoplasm, in which interacted with ZFP36 ring finger protein (ZFP36), a mRNA destabilizing factor, resulting in increased decay of mammalian target of rapamycin complex 2 (mTORC2), a well-known proto-oncogene in AML. Overexpression of mTORC2 partly blocked the tumor suppressive effects of LINC00998. Importantly, LINC00998 shortened in vivo AML cell survival in xenograft tumor model. Taken together, we found that LINC00998 is a novel tumor-inhibiting lncRNA in human AML. The dysregulation of LINC00998/ZFP36/mTORC2 axis is linked to leukemogenesis and progression.

Evaluation of Poly(ADP-ribose) Polymerase Inhibitor, Pamiparib (BGB-290) in Treating Acute Myeloid Leukemia and the Characterization of Its Nanocarrier

Despite the continuous improvement of leukemia treatment in the clinic, the overall 5-year disease-free survival of acute myeloid leukemia (AML) is only approximately 30%-60% due to relapse and the refractoriness of AML after traditional chemotherapy. Inhibition of poly(ADP-ribose) polymerase (PARP), a member of the DNA damage repair complex, has a strong antitumor effect in solid tumors. However, the role of PARP in AML remains unclear. We found that high levels of PARP1 and PARP2 were positively related to chemotherapy resistance and poor prognosis in patients with AML. Doxorubicin (DOX)-resistant AML cells highly expressed PAPR1 and PARP2. Knockdown of PARP1 and PARP2, or pharmaceutical inhibition of PARP by the PARP inhibitor (PARPi) BGB-290, significantly enhanced the cytotoxicity of DOX in AML cells due to increased DNA damage. PLGA-loading BGB-290 was properly self-assembled into stable BGB-290@PLGA nanoparticles (NPs), which is uniform particle size and good stability. BGB-290@PLGA is easily uptake by AML cell lines and stays for a long time. Combined with DOX, BGB-290@PLGA can significantly improve the chemosensitivity of AML cell lines. Furthermore, BGB-290 and DOX combination treatment dramatically repressed the onset of leukemia and prolonged the survival of THP-1 xenografted mice. Overall, this study demonstrated that PARPi with traditional chemotherapy could be an efficient therapeutic strategy for AML.

Novel Polyethylene Glycol-Conjugated Triazole Derivative with High Thyrointegrin αvβ3 Affinity in Acute Myeloid Leukemia Management

(1) Background: Acute myeloid leukemia (AML) accounts for up to one-third of more than 60,000 leukemia cases diagnosed annually in the U.S. Primary AML cells express membrane αvβ3 integrin, which is associated with adverse prognosis and resistance to chemotherapies. A novel anticancer compound Polyethylene glycol-conjugated bi-TriAzole Tetraiodothyroacetic acid (P-bi-TAT) interacts with high affinity (Ki 0.3 nM) and specificity with the thyrointegrin αvβ3. We evaluated P-bi-TAT activities in two different AML models representing monocytic and myelocytic forms of acute leukemia. (2) Methods and Results: The in vivo AML models were established prior to initiation of treatment protocols by grafting human leukemia cells in immunocompromised mice. IVIS imaging scans revealed that leukemic colonies were extensively established throughout the bone marrow, liver, and lung of the untreated animals. In animals treated with P-bi-TAT at daily doses ranging from 1-10 mg/kg, subcutaneously for 2-3 weeks, IVIS imaging scans revealed 95% reduction in bone marrow colonies and leukemic colonies in liver and lung. Also, the leukemic cells were not detected in bone marrow samples of P-bi-TAT-treated animals. The anti-neoplastic effect of P-bi-TAT administration on leukemic cells was associated with marked inhibition of NF-κB activity. We conclude that experimental P-bi-TAT therapy in vivo appears extraordinarily effective against the two forms of human AML models in mice. Because the P-bi-TAT molecular target, thyrointegrin αvβ3, is consistently expressed in many, if not all, clinical AML samples, P-bi-TAT-based therapy seems to have significant clinical potential in treating most AML sub-types. Hence, P-bi-TAT represents a promising targeted therapeutic agent for AML patients.

A novel epigenetic drug conjugating flavonoid and HDAC inhibitor confers to suppression of acute myeloid leukemogenesis

Epigenetic dysregulation has long been identified as a key driver of leukemogenesis in acute myeloid leukemia (AML). However, epigenetic drugs such as histone deacetylase inhibitors (HDACi) targeting epigenetic alterations in AML have obtained only limited clinical efficiency without clear mechanism. Fortunately, we screened out a novel epigenetic agent named Apigenin-Vorinostat-Conjugate (AVC), which provides us a possibility to handle the heterogenous malignancy. Its inhibition on HDACs was presented by HDACs expression, enzyme activity, and histone acetylation level. Its efficacy against AML was detected by cell viability assay and tumor progression of AML mouse model. Apoptosis is the major way causing cell death. We found AVC efficiently suppresses leukemogenesis whereas sparing the normal human cells. Kasumi-1 cells are at least twenty-fold higher sensitive to AVC (IC50=0.024μM) than vorinostat (IC50=0.513μM) and Ara-C (IC50=0.4366μM). Furthermore, it can efficiently regress the tumorigenesis in AML mouse model while keeping the pivotal organs safe, demonstrating a feasibility and favorable safety profile in treatment of AML. Collectively, these pre-clinical data suggest a promising potential utilizing flavonoid-HDACi-conjugate as a next-generation epigenetic drug for clinical therapy against AML.

Acute Myeloid Leukemia Mutations and Future Mechanistic Target to Overcome Resistance

OPINION STATEMENT

Cytogenetics and mutation identification in acute myeloid leukemia have allowed for more targeted therapy. Many therapies have been approved by the FDA in the last 3 years including gilteritinib and azacitidine but the overall survival has remained stagnant at 25%. The inability to achieve complete remission was related to the residual leukemic stem cells (LSCs). Thus, the relationship between bone marrow niche and LSCs must be further explored to prevent treatment relapse/resistance. The development of immunotherapy and nanotechnology may play a role in future therapy to achieve the complete remission. Nano-encapsulation of drugs can improve drugs' bioavailability, help drugs evade resistance, and provide combination therapy directly to the cancer cells. Studies indicate targeting surface antigens such as CLL1 and CD123 using chimeric antibody receptor T cells can improve survival outcomes. Finally, new discoveries indicate that inhibiting integrin αvβ3 and acid ceramidase may prove to be efficacious.

Inhibitors of Chemoresistance Pathways in Combination with Ara-C to Overcome Multidrug Resistance in AML. A Mini Review

Acute myeloid leukemia (AML), the most common type of leukemia in older adults, is a heterogeneous disease that originates from the clonal expansion of undifferentiated hematopoietic progenitor cells. These cells present a remarkable variety of genes and proteins with altered expression and function. Despite significant advances in understanding the molecular panorama of AML and the development of therapies that target mutations, survival has not improved significantly, and the therapy standard is still based on highly toxic chemotherapy, which includes cytarabine (Ara-C) and allogeneic hematopoietic cell transplantation. Approximately 60% of AML patients respond favorably to these treatments and go into complete remission; however, most eventually relapse, develop refractory disease or chemoresistance, and do not survive for more than five years. Therefore, drug resistance that initially occurs in leukemic cells (primary resistance) or that develops during or after treatment (acquired resistance) has become the main obstacle to AML treatment. In this work, the main molecules responsible for generating chemoresistance to Ara-C in AML are discussed, as well as some of the newer strategies to overcome it, such as the inclusion of molecules that can induce synergistic cytotoxicity with Ara-C (MNKI-8e, emodin, metformin and niclosamide), subtoxic concentrations of chemotherapy (PD0332991), and potently antineoplastic treatments that do not damage nonmalignant cells (heteronemin or hydroxyurea + azidothymidine).

A mitophagy inhibitor targeting p62 attenuates the leukemia-initiation potential of acute myeloid leukemia cells

There has been an increasing focus on the tumorigenic potential of leukemia initiating cells (LICs) in acute myeloid leukemia (AML). Despite the important role of selective autophagy in the life-long maintenance of hematopoietic stem cells (HSCs), cancer progression, and chemoresistance, the relationship between LICs and selective autophagy remains to be fully elucidated. Sequestosome 1 (SQSTM1), also known as p62, is a selective autophagy receptor for the degradation of ubiquitinated substrates, and its loss impairs leukemia progression in AML mouse models. In this study, we evaluated the underlying mechanisms of mitophagy in the survival of LICs with XRK3F2, a p62-ZZ inhibitor. We demonstrated that XRK3F2 selectively impaired LICs but spared normal HSCs in both mouse and patient-derived tumor xenograft (PDX) AML models. Mechanistically, we observed that XRK3F2 blocked mitophagy by inhibiting the binding of p62 with defective mitochondria. Our study not only evaluated the effectiveness and safety of XRK3F2 in LICs, but also demonstrated that mitophagy plays an indispensable role in the survival of LICs during AML development and progression, which can be impaired by blocking p62.

Penicillium genus as a source for anti-leukemia compounds: an overview from 1984 to 2020

Penicillium is a widely explored genus due to its chemical diversity and associated biological properties; in addition, it represents an important source for cytotoxic compounds with good application perspectives. Based on these aspects, in this review, Penicillium compounds that presented activity against human leukemia cell lines are being listed and discussed. For this, a careful bibliographic survey was carried out in the main electronic databases, i.e. Scopus, SciFinder, Web of Science and Pubmed. Between 1984 and 2020, thirty seven original papers were selected, when using the search terms Penicillium and leukemia. The occurrence of l-asparaginase produced by some Penicillium spp. was also highlighted since this enzyme is being employed for acute lymphoblastic leukemia and lymphosarcoma therapies. Therefore, this overview aims to demonstrate the potential of metabolites biosynthesized by Penicillium fungi which can be applied in human leukemia therapies and opportunities for designing new lead compounds.

Curcumin promotes cell cycle arrest and apoptosis of acute myeloid leukemia cells by inactivating AKT

Curcumin, a phytochemical from rhizomes of the plant Curcuma longa, has been reported to exert potential anticancer properties in various cancer types, including acute myeloid leukemia (AML). However, the underlying mechanism remains poorly understood. The present study demonstrated that curcumin had a stronger cytotoxic activity against AML cells compared with three other types of phytochemicals (epigallocatechin gallate, genistein and resveratrol). Protein phosphorylation profiling using an antibody array identified that curcumin treatment increased the phosphorylation levels of 14 proteins and decreased those of four proteins. A protein‑protein interaction network was constructed using the STRING database, in which AKT was identified as a hub protein with the highest connectivity (PRAS40, 4E‑BP1, P70S6K, RAF‑1 and p27). Western blotting results indicated that curcumin dose‑dependently suppressed the phosphorylation of AKT, PRAS40, 4E‑BP1, P70S6K, RAF‑1 and p27 in AML cell lines (ML‑2 and OCI‑AML5). It was also demonstrated that curcumin regulated the cell cycle‑ and apoptosis‑related proteins (cyclin D1, p21, Bcl2, cleaved‑caspase‑3 and cleaved‑PARP), leading to cell cycle arrest and apoptosis in both ML‑2 and OCI‑AML5 cells. These effects of curcumin were enhanced by the AKT inhibitor afuresertib but were suppressed by the AKT activator SC‑79, indicating that curcumin functions via AKT. In the AML xenograft mouse model, curcumin and afuresertib synergistically suppressed the engraftment, proliferation and survival of AML cells. Collectively, the present study demonstrated that curcumin exerted anti‑AML roles by inactivating AKT and these findings may aid in the treatment of AML.

Differentiation of acute myeloid leukemia (AML) cells with ATRA reduces 18F-FDG uptake and increases sensitivity towards ABT-737-induced apoptosis

Acute myeloid leukemia (AML) is a malignant disease of the bone marrow, comprising various subtypes. We have investigated seven different AML cell lines that showed different sensitivities toward the inducer of apoptosis ABT-737, with IC₅₀ concentrations ranging from 9.9 nM to 1.8 µM. Besides, the AML cell lines revealed distinct differences in ¹⁸F-FDG uptake ranging from 4.1 to 11.0%. Moreover, the Pearson coefficient (0.363) suggests a moderate correlation between ¹⁸F-FDG uptake and the IC₅₀ values of ABT-737. Differentiation of the AML cell lines NB-4 and AML-193 with all-trans-retinoic-acid (ATRA) induced a significant increase in sensitivity towards ABT-737 along with a reduced uptake of ¹⁸F-FDG. Therefore, ¹⁸F-FDG uptake could be predictive on sensitivity to treatment with ABT-737. Furthermore, because differentiation treatment of AML cells using ATRA reduced ¹⁸F-FDG uptake and increased sensitivity towards ABT-737, a combined treatment regimen with ATRA and ABT-737 might be a promising therapeutic option in the future.

Clusterization in acute myeloid leukemia based on prognostic alternative splicing signature to reveal the clinical characteristics in the bone marrow microenvironment

Background

Alternative splicing (AS), a crucial post-transcriptional regulatory mechanism in expanding the coding capacities of genomes and increasing the diversity of proteins, still faces various challenges in the splicing regulation mechanism of acute myeloid leukemia (AML) and microenvironmental changes.

Results

A total of 27,833 AS events were detected in 8337 genes in 178 AML patients, with exon skip being the predominant type. Approximately 11% of the AS events were significantly related to prognosis, and the prediction models based on various events demonstrated high classification efficiencies. Splicing factors correlation networks further altered the diversity of AS events through epigenetic regulation and clarified the potential mechanism of the splicing pathway. Unsupervised cluster analysis revealed significant correlations between AS and immune features, molecular mutations, immune checkpoints and clinical outcome. The results suggested that AS clusters could be used to identify patient subgroups with different survival outcomes in AML, among which C1 was both associated with good outcome in overall survival. Interestingly, C1 was associated with lower immune scores compared with C2 and C3, and favorable-risk cytogenetics was rarely distributed in C2, but much more common in C1.

Conclusions

This study revealed a comprehensive landscape of AS events, and provides new insight into molecular targeted therapy and immunotherapy strategy for AML.

An expert overview of emerging therapies for acute myeloid leukemia: novel small molecules targeting apoptosis, p53, transcriptional regulation and metabolism

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive malignancy of clonal myeloid precursor cells. Curative therapy has classically involved the use of intensive induction chemotherapy followed by consolidation with additional chemotherapy or allogeneic hematopoietic stem cell transplant. For many patients, such an approach is prohibitive because of high treatment-related toxicities. Advancements in the molecular understanding of AML have led to the introduction of new targeted therapies that are changing the treatment landscape for AML.

AREAS COVERED

We review emerging small molecule inhibitors that have shown preclinical efficacy for the treatment of AML. The compounds discussed affect apoptosis, p53-mediated interactions, transcriptional regulation, and cellular metabolism. We performed a literature search of PubMed and primarily included relevant sources published from 2000 to the present, though earlier sources are also referenced.

EXPERT OPINION

Most clinical trials for AML currently employ novel targeted therapies that demonstrate promising activity in preclinical models. We anticipate that new small molecule inhibitors will continue to enter the clinical realm and alter the treatment paradigm for AML. In a field where clinical advancement was comparatively slow for many years, it appears that we are now starting to see the rapid growth borne out of the deepening molecular understanding of AML.