Inhibition of autophagy as a treatment strategy for p53 wild-type acute myeloid leukemia

Interplay between LncRNAs and autophagy-related pathways in leukemia: mechanisms and clinical implications

Autophagy is a conserved catabolic process that removes protein clumps and defective organelles, thereby promoting cell equilibrium. Growing data suggest that dysregulation of the autophagic pathway is linked to several cancer hallmarks. Long non-coding RNAs (lncRNAs), which are key parts of gene transcription, are increasingly recognized for their significant roles in various biological processes. Recent studies have uncovered a strong connection between the mutational landscape and altered expression of lncRNAs in the tumor formation and development, including leukemia. Research over the past few years has emphasized the role of lncRNAs as important regulators of autophagy-related gene expression. These RNAs can influence key leukemia characteristics, such as apoptosis, proliferation, epithelial-mesenchymal transition (EMT), migration, and angiogenesis, by modulating autophagy-associated signaling pathways. With altered lncRNA expression observed in leukemia cells and tissues, they hold promise as diagnostic biomarkers and therapeutic targets. The current review focuses on the regulatory function of lncRNAs in autophagy and their involvement in leukemia, potentially uncovering valuable therapeutic targets for leukemia treatment.

Lysosomal cation channel TRPML1 suppression sensitizes acute myeloid leukemia cells to chemotherapeutics by inhibiting autophagy

Despite the implementation of novel therapeutic regimens and extensive research efforts, chemoresistance remains a formidable challenge in the treatment of acute myeloid leukemia (AML). Notably, the involvement of lysosomes in chemoresistance has sparked interest in developing lysosome-targeted therapies to sensitize tumor cells to currently approved chemotherapy or as innovative pharmacological approaches. Moreover, as ion channels on the lysosomal membrane are critical regulators of lysosomal function, they present potential as novel targets for enhancing chemosensitivity. Here, we discovered that the expression of a lysosomal cation channel, namely transient receptor potential mucolipin 1 (TRPML1), was elevated in AML cells. Inhibiting TRPML1 individually does not impact the proliferation and apoptosis of AML cells. Importantly, inhibition of TRPML1 demonstrated the potential to modulate the sensitivity of AML cells to chemotherapeutic agents. Exploration of the underlying mechanisms revealed that suppression of TRPML1 impaired autophagy while concurrently increasing the production of reactive oxygen species (ROS) and ROS-mediated lipid peroxidation (Lipid-ROS) in AML cells. Finally, the knockdown of TRPML1 significantly reduced OCI-AML3 tumor growth following chemotherapy in a mouse model of human leukemia. In summary, targeting TRPML1 represents a promising approach for combination therapy aimed at enhancing chemosensitivity in treating AML.

Current Understanding of the Role of Autophagy in the Treatment of Myeloid Leukemia

The most important issues in acute myeloid leukemia are preventing relapse and treating relapse. Although the remission rate has improved to approximately 80%, the 5-year survival rate is only around 30%. The main reasons for this are the high relapse rate and the limited treatment options. In chronic myeloid leukemia patients, when a deep molecular response is achieved for a certain period of time through tyrosine kinase inhibitor treatment, about half of them will reach treatment-free remission, but relapse is still a problem. Therefore, potential therapeutic targets for myeloid leukemias are eagerly awaited. Autophagy suppresses the development of cancer by maintaining cellular homeostasis; however, it also promotes cancer progression by helping cancer cells survive under various metabolic stresses. In addition, autophagy is promoted or suppressed in cancer cells by various genetic mutations. Therefore, the development of therapies that target autophagy is also being actively researched in the field of leukemia. In this review, studies of the role of autophagy in hematopoiesis, leukemogenesis, and myeloid leukemias are presented, and the impact of autophagy regulation on leukemia treatment and the clinical trials of autophagy-related drugs to date is discussed.

Atypical phosphatase DUSP11 inhibition promotes nc886 expression and potentiates gemcitabine-mediated cell death through NF-kB modulation

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest cancers among all solid tumors. First-line treatment relies on gemcitabine (Gem) and despite treatment improvements, refractoriness remains a universal challenge. Attempts to decipher how feedback-loops control signaling pathways towards drug resistance have gained attention in recent years, particularly focused on the role of phosphatases. In this study, a CRISPR/Cas9-based phenotypic screen was performed to identify members from the dual-specificity phosphatases (DUSP) family potentially acting on Gem response in PDAC cells. The approach revealed the atypical RNA phosphatase DUSP11 as a potential target, whose inhibition creates vulnerability of PDAC cells to Gem. DUSP11 genetic inhibition impaired cell survival and promoted apoptosis, synergistically enhancing Gem cytotoxicity. In silico transcriptome analysis of RNA-seq data from PDAC human samples identified NF-ĸB signaling pathway highly correlated with DUSP11 upregulation. Consistently, Gem-induced NF-ĸB phosphorylation was blocked upon DUSP11 inhibition in vitro. Mechanistically, we found that DUSP11 directly impacts nc886 expression and modulates PKR-NF-ĸB signaling cascade after Gem exposure in PDAC cells resulting in resistance to Gem-induced cell death. In conclusion, this study provides new insights on DUSP11 role in RNA biology and Gem response in PDAC cells.

Mechanism of salidroside regulating autophagy based on network pharmacology and molecular docking

Salidroside is a natural product of phenols with a wide range of pharmacological functions, but whether it plays a role in regulating autophagy is unclear. We systematically investigated the regulatory effect and molecular mechanism of salidroside on autophagy through network pharmacology, which provided a theoretical basis for subsequent experimental research. First, the target genes of salidroside were obtained using the Chinese Medicine System Pharmacology Database and Analysis Platform, and the target genes were converted into standardized gene names using the Uniprot website. At the same time, autophagy-related genes were collected from GeneCards, and preliminary handling of data to obtain intersecting genes. Then, the String website was used to construct a protein-protein interaction network, and to perform the Gene Ontology functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway analysis. To observe the specific molecular mechanism by which salidroside regulates autophagy, we constructed a drug component-target genes-autophagy network. Finally, we performed molecular docking to verify the possible binding conformation between salidroside and the candidate target. By searching the database and analyzing the data, we found that 113 target genes in salidroside interact with autophagy. Salidroside regulate autophagy in relation to a number of important oncogenes and signaling pathways. Molecular docking confirmed that salidroside has high affinity with mTOR, SIRT1, and AKT1. Through network pharmacology combined with molecular docking-validated research methods, we revealed the underlying mechanism of salidroside regulation of autophagy. This study not only provides new systematic insights into the underlying mechanism of salidroside in autophagy, but also provides new ideas for network approaches for autophagy-related research.

Potential role of p53 deregulation in modulating immune responses in human malignancies: A paradigm to develop immunotherapy

The crucial role played by the oncogenic expression of TP53, stemming from mutation or amyloid formation, in various human malignancies has been extensively studied over the past two decades. Interestingly, the potential role of TP53 as a crucial player in modulating immune responses has provided new insight into the field of cancer biology. The loss of p53's transcriptional functions and/or the acquisition of tumorigenic properties can efficiently modulate the recruitment and functions of myeloid and lymphoid cells, ultimately leading to the evasion of immune responses in human tumors. Consequently, the oncogenic nature of the tumor suppressor p53 can dynamically alter the function of immune cells, providing support for tumor progression and metastasis. This review comprehensively explores the dual role of p53 as both the guardian of the genome and an oncogenic driver, especially in the context of regulation of autophagy, apoptosis, the tumor microenvironment, immune cells, innate immunity, and adaptive immune responses. Additionally, the focus of this review centers on how p53 status in the immune response can be harnessed for the development of tailored therapeutic strategies and their potential application in immunotherapy against human malignancies.

Extended exposure to low doses of azacitidine induces differentiation of leukemic stem cells through activation of myeloperoxidase

Oral azacitidine (oral-Aza) treatment results in longer median overall survival (OS) (24.7 vs. 14.8 months in placebo) in patients with acute myeloid leukemia (AML) in remission after intensive chemotherapy. The dosing schedule of oral-Aza (14 days/28-day cycle) allows for low exposure of Aza for an extended duration thereby facilitating a sustained therapeutic effect. However, the underlying mechanisms supporting the clinical impact of oral-Aza in maintenance therapy remain to be fully understood. In this preclinical work, we explore the mechanistic basis of oral-Aza/extended exposure to Aza through in vitro and in vivo modeling. In cell lines, extended exposure to Aza results in sustained DNMT1 loss, leading to durable hypomethylation, and gene expression changes. In mouse models, extended exposure to Aza, preferentially targets immature leukemic cells. In leukemic stem cell (LSC) models, the extended dose of Aza induces differentiation and depletes CD34+CD38- LSC. Mechanistically, LSC differentiation is driven in part by increased myeloperoxidase (MPO) expression. Inhibition of MPO activity either by using an MPO-specific inhibitor or blocking oxidative stress, a known mechanism of MPO, partly reverses the differentiation of LSC. Overall, our preclinical work reveals novel mechanistic insights into oral-Aza and its ability to target LSC.

ULK2 Is a Key Pro-Autophagy Protein That Contributes to the High Chemoresistance and Disease Relapse in FLT3-Mutated Acute Myeloid Leukemia

We recently demonstrated that a small subset of cells in FLT3-mutated acute myeloid leukemia (AML) cell lines exhibit SORE6 reporter activity and cancer stem-like features including chemoresistance. To study why SORE6+ cells are more chemoresistant than SORE6- cells, we hypothesized that these cells carry higher autophagy, a mechanism linked to chemoresistance. We found that cytarabine (Ara-C) induced a substantially higher protein level of LC3B-II in SORE6+ compared to SORE6- cells. Similar observations were made using a fluorescence signal-based autophagy assay. Furthermore, chloroquine (an autophagy inhibitor) sensitized SORE6+ but not SORE6- cells to Ara-C. To decipher the molecular mechanisms underlying the high autophagic flux in SORE6+ cells, we employed an autophagy oligonucleotide array comparing gene expression between SORE6+ and SORE6- cells before and after Ara-C treatment. ULK2 was the most differentially expressed gene between the two cell subsets. To demonstrate the role of ULK2 in conferring higher chemoresistance in SORE6+ cells, we treated the two cell subsets with a ULK1/2 inhibitor, MRT68921. MRT68921 significantly sensitized SORE6+ but not SORE6- cells to Ara-C. Using our in vitro model for AML relapse, we found that regenerated AML cells contained higher ULK2 expression compared to pretreated cells. Importantly, inhibition of ULK2 using MRT68921 prevented in vitro AML relapse. Lastly, using pretreatment and relapsed AML patient bone marrow samples, we found that ULK2 expression was higher in relapsed AML. To conclude, our results supported the importance of autophagy in the relapse of FLT3-mutated AML and highlighted ULK2 in this context.

OGG1 as an Epigenetic Reader Affects NFκB: What This Means for Cancer

8-oxoguanine glycosylase 1 (OGG1), which was initially identified as the enzyme that catalyzes the first step in the DNA base excision repair pathway, is now also recognized as a modulator of gene expression. What is important for cancer is that OGG1 acts as a modulator of NFκB-driven gene expression. Specifically, oxidant stress in the cell transiently halts enzymatic activity of substrate-bound OGG1. The stalled OGG1 facilitates DNA binding of transactivators, such as NFκB to their cognate sites, enabling the expression of cytokines and chemokines, with ensuing recruitment of inflammatory cells. Recently, we highlighted chief aspects of OGG1 involvement in regulation of gene expression, which hold significance in lung cancer development. However, OGG1 has also been implicated in the molecular underpinning of acute myeloid leukemia. This review analyzes and discusses how these cells adapt through redox-modulated intricate connections, via interaction of OGG1 with NFκB, which provides malignant cells with alternative molecular pathways to transform their microenvironment, enabling adjustment, promoting cell proliferation, metastasis, and evading killing by therapeutic agents.

Fasting-Mimicking Diet Inhibits Autophagy and Synergizes with Chemotherapy to Promote T-Cell-Dependent Leukemia-Free Survival

Fasting mimicking diets (FMDs) are effective in the treatment of many solid tumors in mouse models, but their effect on hematologic malignancies is poorly understood, particularly in combination with standard therapies. Here we show that cycles of a 3-day FMD given to high-fat-diet-fed mice once a week increased the efficacy of vincristine to improve survival from BCR-ABL B acute lymphoblastic leukemia (ALL). In mice fed a standard diet, FMD cycles in combination with vincristine promoted cancer-free survival. RNA seq and protein assays revealed a vincristine-dependent decrease in the expression of multiple autophagy markers, which was exacerbated by the fasting/FMD conditions. The autophagy inhibitor chloroquine could substitute for fasting/FMD to promote cancer-free survival in combination with vincristine. In vitro, targeted inhibition of autophagy genes ULK1 and ATG9a strongly potentiated vincristine's toxicity. Moreover, anti-CD8 antibodies reversed the effects of vincristine plus fasting/FMD in promoting leukemia-free survival in mice, indicating a central role of the immune system in this response. Thus, the inhibition of autophagy and enhancement of immune responses appear to be mediators of the fasting/FMD-dependent cancer-free survival in ALL mice.

Hydroxychloroquine: Key therapeutic advances and emerging nanotechnological landscape for cancer mitigation

Hydroxychloroquine (HCQ) is a unique class of medications that has been widely utilized for the treatment of cancer. HCQ plays a dichotomous role by inhibiting autophagy induced by the tumor microenvironment (TME). Preclinical studies support the use of HCQ for anti-cancer therapy, especially in combination with conventional anti-cancer treatments since they sensitize tumor cells to drugs, potentiating the therapeutic activity. However, clinical evidence has suggested poor outcomes for HCQ due to various obstacles, including non-specific distribution, low aqueous solubility and low bioavailability at target sites, transport across tissue barriers, and retinal toxicity. These issues are addressable via the integration of HCQ with nanotechnology to produce HCQ-conjugated nanomedicines. This review aims to discuss the pharmacodynamic, pharmacokinetic and antitumor properties of HCQ. Furthermore, the antitumor performance of the nanoformulated HCQ is also reviewed thoroughly, aiming to serve as a guide for the HCQ-based enhanced treatment of cancers. The nanoencapsulation or nanoconjugation of HCQ with nanoassemblies appears to be a promising method for reducing the toxicity and improving the antitumor efficacy of HCQ.

Deciphering the mitophagy receptor network identifies a crucial role for OPTN (optineurin) in acute myeloid leukemia

The selective autophagic degradation of mitochondria via mitophagy is essential for preserving mitochondrial homeostasis and, thereby, disease maintenance and progression in acute myeloid leukemia (AML). Mitophagy is orchestrated by a variety of mitophagy receptors whose interplay is not well understood. Here, we established a pairwise multiplexed CRISPR screen targeting mitophagy receptors to elucidate redundancies and gain a deeper understanding of the functional interactome governing mitophagy in AML. We identified OPTN (optineurin) as sole non-redundant mitophagy receptor and characterized its unique role in AML. Knockdown and overexpression experiments demonstrated that OPTN expression is rate-limiting for AML cell proliferation. In a MN1-driven murine transplantation model, loss of OPTN prolonged overall median survival by 7 days (+21%). Mechanistically, we found broadly impaired mitochondrial respiration and function with increased mitochondrial ROS, that most likely caused the proliferation defect. Our results decipher the intertwined network of mitophagy receptors in AML for both ubiquitin-dependent and receptor-mediated mitophagy, identify OPTN as a non-redundant tool to study mitophagy in the context of leukemia and suggest OPTN inhibition as an attractive therapeutic strategy.Abbreviations: AML: acute myeloid leukemia; CRISPR: Clustered Regularly Interspaced Short Palindromic Repeats; CTRL: control; DFP: deferiprone; GI: genetic interaction; KD: knockdown; KO: knockout; ldMBM, lineage-depleted murine bone marrow; LFC: log2 fold change; LIR: LC3-interacting region; LSC: leukemic stem cell; MAGeCK: Model-based Analysis of Genome-wide CRISPR-Cas9 Knockout; MDIVI-1: mitochondrial division inhibitor 1; MOI: multiplicity of infection; MOM: mitochondrial outer membrane; NAC: N-acetyl-L-cysteine; OA: oligomycin-antimycin A; OCR: oxygen consumption rate; OE: overexpression; OPTN: optineurin; PINK1: PTEN induced putative kinase 1; ROS: reactive oxygen species; SEM: standard error of the mean; TCGA: The Cancer Genome Atlas; TEM: transmission electron microscopy; UBD: ubiquitin-binding domain; WT: wild type.

Vacuolar ATPase Is a Possible Therapeutic Target in Acute Myeloid Leukemia: Focus on Patient Heterogeneity and Treatment Toxicity

Vacuolar ATPase (V-ATPase) is regarded as a possible target in cancer treatment. It is expressed in primary acute myeloid leukemia cells (AML), but the expression varies between patients and is highest for patients with a favorable prognosis after intensive chemotherapy. We therefore investigated the functional effects of two V-ATPase inhibitors (bafilomycin A1, concanamycin A) for primary AML cells derived from 80 consecutive patients. The V-ATPase inhibitors showed dose-dependent antiproliferative and proapoptotic effects that varied considerably between patients. A proteomic comparison of primary AML cells showing weak versus strong antiproliferative effects of V-ATPase inhibition showed a differential expression of proteins involved in intracellular transport/cytoskeleton functions, and an equivalent phosphoproteomic comparison showed a differential expression of proteins that regulate RNA processing/function together with increased activity of casein kinase 2. Patients with secondary AML, i.e., a heterogeneous subset with generally adverse prognosis and previous cytotoxic therapy, myeloproliferative neoplasia or myelodysplastic syndrome, were characterized by a strong antiproliferative effect of V-ATPase inhibition and also by a specific mRNA expression profile of V-ATPase interactome proteins. Furthermore, the V-ATPase inhibition altered the constitutive extracellular release of several soluble mediators (e.g., chemokines, interleukins, proteases, protease inhibitors), and increased mediator levels in the presence of AML-supporting bone marrow mesenchymal stem cells was then observed, especially for patients with secondary AML. Finally, animal studies suggested that the V-ATPase inhibitor bafilomycin had limited toxicity, even when combined with cytarabine. To conclude, V-ATPase inhibition has antileukemic effects in AML, but this effect varies between patients.

In vitro effect of hydroxychloroquine on pluripotent stem cells and their cardiomyocytes derivatives

Introduction: Hydroxychloroquine (HDQ) is an antimalarial drug that has also shown its effectiveness in autoimmune diseases. Despite having side effects such as retinopathy, neuromyopathy and controversial cardiac toxicity, HDQ has been presented and now intensively studied for the treatment and prevention of coronavirus disease 2019 (COVID-19). Recent works revealed both beneficial and toxic effects during HDQ treatment. The cardiotoxic profile of HDQ remains unclear and identifying risk factors is challenging. Methods: Here, we used well-established cell-cultured to study the cytotoxic effect of HDQ, mouse induced pluripotent stem cells (miPSC) and their cardiomyocytes (CMs) derivatives were exposed to different concentrations of HDQ. Cell colony morphology was assessed by microscopy whereas cell viability was measured by flow cytometry and impedance-based methods. The effect of HDQ on beating activity of mouse and human induced pluripotent stem cell-derived CMs (miPSC-CMs and hiPSC-CMs, respectively) and mouse embryonic stem cell-derived CMs (mESC-CMs) were captured by the xCELLigence RTCA and microelectrode array (MEA) systems. Results and discussion: Our results revealed that 20 µM of HDQ promotes proliferation of stem cells used suggesting that if appropriately monitored, HDQ may have a cardioprotective effect and may also represent a possible candidate for tissue repair. In addition, the field potential signals revealed that higher doses of this medication caused bradycardia that could be reversed with a higher concentration of ß-adrenergic agonist, Isoproterenol (Iso). On the contrary, HDQ caused an increase in the beating rate of hiPSC-CMs, which was further helped upon application of Isoproterenol (Iso) suggesting that HDQ and Iso may also work synergistically. These results indicate that HDQ is potentially toxic at high concentrations and can modulate the beating activity of cardiomyocytes. Moreover, HDQ could have a synergistic inotropic effect with isoproterenol on cardiac cells.

Galectin-9 has non-apoptotic cytotoxic activity toward acute myeloid leukemia independent of cytarabine resistance

Acute myeloid leukemia (AML) is a malignancy still associated with poor survival rates, among others, due to frequent occurrence of therapy-resistant relapse after standard-of-care treatment with cytarabine (AraC). AraC triggers apoptotic cell death, a type of cell death to which AML cells often become resistant. Therefore, therapeutic options that trigger an alternate type of cell death are of particular interest. We previously identified that the glycan-binding protein Galectin-9 (Gal-9) has tumor-selective and non-apoptotic cytotoxicity towards various types of cancer, which depended on autophagy inhibition. Thus, Gal-9 could be of therapeutic interest for (AraC-resistant) AML. In the current study, treatment with Gal-9 was cytotoxic for AML cells, including for CD34⁺ patient-derived AML stem cells, but not for healthy cord blood-derived CD34⁺ stem cells. This Gal-9-mediated cytotoxicity did not rely on apoptosis but was negatively associated with autophagic flux. Importantly, both AraC-sensitive and -resistant AML cell lines, as well as AML patient samples, were sensitive to single-agent treatment with Gal-9. Additionally, Gal-9 potentiated the cytotoxic effect of DNA demethylase inhibitor Azacytidine (Aza), a drug that is clinically used for patients that are not eligible for intensive AraC treatment. Thus, Gal-9 is a potential therapeutic agent for the treatment of AML, including AraC-resistant AML, by inducing caspase-independent cell death.

Update on Autophagy Inhibitors in Cancer: Opening up to a Therapeutic Combination with Immune Checkpoint Inhibitors

Autophagy is a highly conserved and natural degradation process that helps maintain cell homeostasis through the elimination of old, worn, and defective cellular components, ensuring proper cell energy intake. The degradative pathway constitutes a protective barrier against diverse human diseases including cancer. Autophagy basal level has been reported to be completely dysregulated during the entire oncogenic process. Autophagy influences not only cancer initiation, development, and maintenance but also regulates cancer response to therapy. Currently, autophagy inhibitor candidates mainly target the early autophagy process without any successful preclinical/clinical development. Lessons learned from autophagy pharmaceutical manipulation as a curative option progressively help to improve drug design and to encounter new targets of interest. Combinatorial strategies with autophagy modulators are supported by abundant evidence, especially dealing with immune checkpoint inhibitors, for which encouraging preclinical results have been recently published. GNS561, a PPT1 inhibitor, is a promising autophagy modulator as it has started a phase 2 clinical trial in liver cancer indication, combined with atezolizumab and bevacizumab, an assessment without precedent in the field. This approach paves a new road, leading to the resurgence of anticancer autophagy inhibitors as an attractive therapeutic target in cancer.

Advances in Understanding the Links between Metabolism and Autophagy in Acute Myeloid Leukemia: From Biology to Therapeutic Targeting

Autophagy is a highly conserved cellular degradation process that regulates cellular metabolism and homeostasis under normal and pathophysiological conditions. Autophagy and metabolism are linked in the hematopoietic system, playing a fundamental role in the self-renewal, survival, and differentiation of hematopoietic stem and progenitor cells, and in cell death, particularly affecting the cellular fate of the hematopoietic stem cell pool. In leukemia, autophagy sustains leukemic cell growth, contributes to survival of leukemic stem cells and chemotherapy resistance. The high frequency of disease relapse caused by relapse-initiating leukemic cells resistant to therapy occurs in acute myeloid leukemia (AML), and depends on the AML subtypes and treatments used. Targeting autophagy may represent a promising strategy to overcome therapeutic resistance in AML, for which prognosis remains poor. In this review, we illustrate the role of autophagy and the impact of its deregulation on the metabolism of normal and leukemic hematopoietic cells. We report updates on the contribution of autophagy to AML development and relapse, and the latest evidence indicating autophagy-related genes as potential prognostic predictors and drivers of AML. We review the recent advances in autophagy manipulation, combined with various anti-leukemia therapies, for an effective autophagy-targeted therapy for AML.

Emerging drugs targeting cellular redox homeostasis to eliminate acute myeloid leukemia stem cells

Acute myeloid leukemia (AML) is a very heterogeneous group of disorders with large differences in the percentage of immature blasts that presently are classified according to the specific mutations that trigger malignant proliferation among thousands of mutations reported thus far. It is an aggressive disease for which few targeted therapies are available and still has a high recurrence rate and low overall survival. The main reason for AML relapse is believed to be due to leukemic stem cells (LSCs) that have unlimited self-renewal capacity and long residence in a quiescent state, which promote greater resistance to traditional therapies for this cancer. AML LSCs have low oxidative stress levels, which appear to be caused by a combination of low mitochondrial activity and high activity of ROS-removing pathways. In this sense, oxidative stress has been thought to be an important new potential target for the treatment of AML patients, targeting the eradication of AML LSCs. The aim of this review is to discuss some drugs that induce oxidative stress to direct new goals for future research focusing on redox imbalance as an effective strategy to eliminate AML LSCs.

TP53 signal pathway confers potential therapy target in acute myeloid leukemia

TP53 mutation is a frequent tumor suppressor mutation and a critical prognostic indicator across studies in many malignant tumors including hematologic malignancies. However, the role of TP53 and its correlative pathway in acute myeloid leukemia (AML) is enigmatic, which may provide possible emerging strategies with the potential to improve outcomes in AML. Accordingly, we focus not only on the TP53 mutation but also on the underlying mechanisms of the mutated TP53 signal pathway. While it is now generally accepted that TP53 mutations are widely associated with a dismal prognosis, resistance to chemotherapy, and high incidence of relapse and refractory AML. Hereby, the current therapeutics targeting TP53 mutant AML are summarized in this review. This will address emerging TP53-based therapeutic approaches, facilizing the TP53-targeted treatment options.

Identification of autophagy-associated genes and prognostic implications in adults with acute myeloid leukemia by integrated bioinformatics analysis

Acute myeloid leukemia (AML) is one of the most common malignant blood neoplasma in adults. The prominent disease heterogeneity makes it challenging to foresee patient survival. Autophagy, a highly conserved degradative process, played indispensable and context-dependent roles in AML. However, it remains elusive whether autophagy-associated stratification could accurately predict prognosis of AML patients. Here, we developed a prognostic model based on autophagy-associated genes, and constructed scoring systems that help to predicte the survival of AML patients in both TCGA data and independent AML cohorts. The Nomogram model also confirmed the autophagy-associated model by showing the high concordance between observed and predicted survivals. Additionally, pathway enrichment analysis and protein-protein interaction network unveiled functional signaling pathways that were associated with autophagy. Altogether, we constructed the autophagy-associated prognostic model that might be likely to predict outcome for AML patients, providing insights into the biological risk stratification strategies and potential therapeutic targets.

Autophagy inhibition impairs leukemia stem cell function in FLT3-ITD AML but has antagonistic interactions with tyrosine kinase inhibition

The FLT3-ITD mutation is associated with poor prognosis in acute myeloid leukemia (AML). FLT3 tyrosine kinase inhibitors (TKIs) demonstrate clinical efficacy but fail to target leukemia stem cells (LSC) and do not generate sustained responses. Autophagy is an important cellular stress response contributing to hematopoietic stem cells (HSC) maintenance and promoting leukemia development. Here we investigated the role of autophagy in regulating FLT3-ITD AML stem cell function and response to TKI treatment. We show that autophagy inhibition reduced quiescence and depleted repopulating potential of FLT3-ITD AML LSC, associated with mitochondrial accumulation and increased oxidative phosphorylation. However, TKI treatment reduced mitochondrial respiration and unexpectedly antagonized the effects of autophagy inhibition on LSC attrition. We further show that TKI-mediated targeting of AML LSC and committed progenitors was p53-dependent, and that autophagy inhibition enhanced p53 activity and increased TKI-mediated targeting of AML progenitors, but decreased p53 activity in LSC and reduced TKI-mediated LSC inhibition. These results provide new insights into the role of autophagy in differentially regulating AML stem and progenitor cells, reveal unexpected antagonistic effects of combined oncogenic tyrosine kinase inhibition and autophagy inhibition in AML LSC, and suggest an alternative approach to target AML LSC quiescence and regenerative potential.

The Potential of Epigallocatechin Gallate (EGCG) in Targeting Autophagy for Cancer Treatment: A Narrative Review

Autophagy is an evolutionarily conserved process for the degradation of redundant or damaged cellular material by means of a lysosome-dependent mechanism, contributing to cell homeostasis and survival. Autophagy plays a multifaceted and context-dependent role in cancer initiation, maintenance, and progression; it has a tumor suppressive role in the absence of disease and is upregulated in cancer cells to meet their elevated metabolic demands. Autophagy represents a promising but challenging target in cancer treatment. Green tea is a widely used beverage with healthy effects on several diseases, including cancer. The bioactive compounds of green tea are mainly catechins, and epigallocatechin-gallate (EGCG) is the most abundant and biologically active among them. In this review, evidence of autophagy modulation and anti-cancer effects induced by EGCG treatment in experimental cancer models is presented. Reviewed articles reveal that EGCG promotes cytotoxic autophagy often through the inactivation of PI3K/Akt/mTOR pathway, resulting in apoptosis induction. EGCG pro-oxidant activity has been postulated to be responsible for its anti-cancer effects. In combination therapy with a chemotherapy drug, EGCG inhibits cell growth and the drug-induced pro-survival autophagy. The selected studies rightly claim EGCG as a valuable agent in cancer chemoprevention.

The dual role of autophagy in acute myeloid leukemia

Acute myeloid leukemia (AML) is a severe hematologic malignancy prevalent in older patients, and the identification of potential therapeutic targets for AML is problematic. Autophagy is a lysosome-dependent catabolic pathway involved in the tumorigenesis and/or treatment of various cancers. Mounting evidence has suggested that autophagy plays a critical role in the initiation and progression of AML and anticancer responses. In this review, we describe recent updates on the multifaceted functions of autophagy linking to genetic alterations of AML. We also summarize the latest evidence for autophagy-related genes as potential prognostic predictors and drivers of AML tumorigenesis. We then discuss the crosstalk between autophagy and tumor cell metabolism into the impact on both AML progression and anti-leukemic treatment. Moreover, a series of autophagy regulators, i.e., the inhibitors and activators, are described as potential therapeutics for AML. Finally, we describe the translation of autophagy-modulating therapeutics into clinical practice. Autophagy in AML is a double-edged sword, necessitating a deeper understanding of how autophagy influences dual functions in AML tumorigenesis and anti-leukemic responses.

Metabolic Rewiring Is Essential for AML Cell Survival to Overcome Autophagy Inhibition by Loss of ATG3

Autophagy is an important survival mechanism that allows recycling of nutrients and removal of damaged organelles and has been shown to contribute to the proliferation of acute myeloid leukemia (AML) cells. However, little is known about the mechanism by which autophagy- dependent AML cells can overcome dysfunctional autophagy. In our study we identified autophagy related protein 3 (ATG3) as a crucial autophagy gene for AML cell proliferation by conducting a CRISPR/Cas9 dropout screen with a library targeting around 200 autophagy-related genes. shRNA-mediated loss of ATG3 impaired autophagy function in AML cells and increased their mitochondrial activity and energy metabolism, as shown by elevated mitochondrial ROS generation and mitochondrial respiration. Using tracer-based NMR metabolomics analysis we further demonstrate that the loss of ATG3 resulted in an upregulation of glycolysis, lactate production, and oxidative phosphorylation. Additionally, loss of ATG3 strongly sensitized AML cells to the inhibition of mitochondrial metabolism. These findings highlight the metabolic vulnerabilities that AML cells acquire from autophagy inhibition and support further exploration of combination therapies targeting autophagy and mitochondrial metabolism in AML.

A perspective on the role of autophagy in cancer

Autophagy refers to a ubiquitous set of catabolic pathways required to achieve proper cellular homeostasis. Aberrant autophagy has been implicated in a multitude of diseases including cancer. In this review, we highlight pioneering and groundbreaking research that centers on delineating the role of autophagy in cancer initiation, proliferation and metastasis. First, we discuss the autophagy-related (ATG) proteins and their respective roles in the de novo formation of autophagosomes and the subsequent delivery of cargo to the lysosome for recycling. Next, we touch upon the history of cancer research that centers upon ATG proteins and regulatory mechanisms that control an appropriate autophagic response and how these are altered in the diseased state. Then, we discuss the various discoveries that led to the idea of autophagy as a double-edged sword when it comes to cancer therapy. This review also briefly narrates how different types of autophagy-selective macroautophagy and chaperone-mediated autophagy, have been linked to different cancers. Overall, these studies build upon a steadfast trajectory that aims to solve the monumentally daunting challenge of finding a cure for many types of cancer by modulating autophagy either through inhibition or induction.

Understanding the Role of Autophagy in Cancer Formation and Progression Is a Real Opportunity to Treat and Cure Human Cancers

Simple Summary

The modulation of autophagy represents a potential therapeutic strategy for cancer. More than one hundred clinical trials have been conducted or are ongoing to explore the efficacy of autophagy modulators to reduce the tumor growth and potentiate the anti-cancer effects of conventional therapy. Despite this, the effective role of autophagy during tumor initiation, growth, and metastasis remains not well understood. Depending on the cancer type and stage of cancer, autophagy may have tumor suppressor properties as well as help cancer cells to proliferate and evade cancer therapy. The current review aims to summarize the current knowledge about the autophagy implications in cancer and report the therapeutic opportunities based on the modulation of the autophagy process.

Abstract

The malignant transformation of a cell produces the accumulation of several cellular adaptions. These changes determine variations in biological processes that are necessary for a cancerous cell to survive during stressful conditions. Autophagy is the main nutrient recycling and metabolic adaptor mechanism in eukaryotic cells, represents a continuous source of energy and biomolecules, and is fundamental to preserve the correct cellular homeostasis during unfavorable conditions. In recent decades, several findings demonstrate a close relationship between autophagy, malignant transformation, and cancer progression. The evidence suggests that autophagy in the cancer context has a bipolar role (it may act as a tumor suppressor and as a mechanism of cell survival for established tumors) and demonstrates that the targeting of autophagy may represent novel therapeutic opportunities. Accordingly, the modulation of autophagy has important clinical benefits in patients affected by diverse cancer types. Currently, about 30 clinical trials are actively investigating the efficacy of autophagy modulators to enhance the efficacy of cytotoxic chemotherapy treatments. A deeper understanding of the molecular pathways regulating autophagy in the cancer context will provide new ways to target autophagy for improving the therapeutic benefits. Herein, we describe how autophagy participates during malignant transformation and cancer progression, and we report the ultimate efforts to translate this knowledge into specific therapeutic approaches to treat and cure human cancers.

TCP1 increases drug resistance in acute myeloid leukemia by suppressing autophagy via activating AKT/mTOR signaling

T-complex protein 1 (TCP1) is one of the subunits of chaperonin-containing T complex (CCT), which is involved in protein folding, cell proliferation, apoptosis, cell cycle regulation, and drug resistance. Investigations have demonstrated that TCP1 is a factor being responsible for drug resistance in breast and ovarian cancer. However, the TCP1 role in acute myeloid leukemia (AML) remains elusive. In the present study, we discovered that the TCP1 expression was elevated in AML patients and high TCP1 expression was associated with low complete response rate along with poor overall survival. TCP1 showed higher expression in the adriamycin-resistant leukemia cell line HL60/A and K562/A, comparing to their respective parent cells HL60 and K562 cells. TCP1 inhibition suppressed drug resistance in HL60/A and K562/A cells, whereas TCP1 overexpression in HL60 cells incremented drug resistance, both in vitro and in vivo. Mechanistic investigations revealed that TCP1 inhibited autophagy and adriamycin-induced cell apoptosis, and TCP1-mediated autophagy inhibition conferred resistance to adriamycin-induced cell apoptosis. Furthermore, TCP1 interacted with AKT and mTOR to activate AKT/mTOR signaling, which negatively regulates apoptosis and autophagy. Pharmacological inhibition of AKT/mTOR signal particularly activated autophagy and resensitized TCP1-overexpressing HL60 cells to adriamycin. These findings identify a novel role of TCP1 regarding drug resistance in AML, which advise a new strategy for overcoming drug resistance in AML through targeting TCP1/AKT/mTOR signaling pathway.

Busulfan Suppresses Autophagy in Mouse Spermatogonial Progenitor Cells via mTOR of AKT and p53 Signaling Pathways

In testis, a rare undifferentiated germ cell population with the capacity to regenerate robustly and support spermatogenesis, is defined as spermatogonial progenitor cells (SPCs) population. As a widely used drug for tumor therapy or bone marrow transplantation, busulfan has a severe side effect on SPCs population and causes a consequent infertility. Recently, accumulating evidence revealed the protective role of autophagy in stem cell maintenance under exogenous stress. To better understand the role of autophagy in SPCs fates, we investigated the potential function of autophagy in SPCs under busulfan stress, and found that treatment of busulfan induced the formation of autophagic vesicles and autophagosomes in mouse SPCs. Subsequently, a connection of autophagy and SPCs maintenance and survival was demonstrated in a dose-dependent manner. Moreover, mTOR was identified as an essential factor for autophagy in SPCs with a complicated mechanism: (1) mTOR is phosphorylated by AKT to activate its target genes, p70s6 kinase, resulting in the inhibition of autophagy during short-term busulfan treatment. (2) mTOR mediates autophagy with p53 together, to regulate the fate of SPCs. Collectively, observations from this study indicate that moderate autophagy effectively protects SPCs from the stress of chemotherapy, which may provide an important hint for fertility protection in clinic.

Antitumor effects of chloroquine/hydroxychloroquine mediated by inhibition of the NF-κB signaling pathway through abrogation of autophagic p47 degradation in adult T-cell leukemia/lymphoma cells

Adult T-cell leukemia/lymphoma (ATLL) originates from human T-cell leukemia virus type 1 (HTLV-1) infection due to the activation of the nuclear factor-κB (NF-κB) signaling pathway to maintain proliferation and survival. An important mechanism of the activated NF-κB signaling pathway in ATLL is the activation of the macroautophagy (herafter referred to as autophagy in the remainder of this manuscript)-lysosomal degradation of p47 (NSFL1C), a negative regulator of the NF-κB pathway. Therefore, we considered the use of chloroquine (CQ) or hydroxychloroquine (HCQ) (CQ/HCQ) as an autophagy inhibitor to treat ATLL; these drugs were originally approved by the FDA as antimalarial drugs and have recently been used to treat autoimmune diseases, such as systemic lupus erythematosus (SLE). In this paper, we determined the therapeutic efficacy of CQ/HCQ, as NF-κB inhibitors, in ATLL mediated by blockade of p47 degradation. Administration of CQ/HCQ to ATLL cell lines and primary ATLL cells induced cell growth inhibition in a dose-dependent manner, and the majority of cells underwent apoptosis after CQ administration. As to the molecular mechanism, autophagy was inhibited in CQ-treated ATLL cells, and activation of the NF-κB pathway was suppressed with the restoration of the p47 level. When the antitumor effect of CQ/HCQ was examined using immunodeficient mice transplanted with ATLL cell lines, CQ/HCQ significantly suppressed tumor growth and improved the survival rate in the ATLL xenograft mouse model. Importantly, HCQ selectively induced ATLL cell death in the ATLL xenograft mouse model at the dose used to treat SLE. Taken together, our results suggest that the inhibition of autophagy by CQ/HCQ may become a novel and effective strategy for the treatment of ATLL.

Effects of the Autophagy-Inhibiting Agent Chloroquine on Acute Myeloid Leukemia Cells; Characterization of Patient Heterogeneity

Autophagy is a highly conserved cellular degradation process that prevents cell damage and promotes cell survival, and clinical efforts have exploited autophagy inhibition as a therapeutic strategy in cancer. Chloroquine is a well-known antimalarial agent that inhibits late-stage autophagy. We evaluated the effects of chloroquine on cell viability and proliferation of acute myeloid leukemia acute myeloid leukemia (AML) cells derived from 81 AML patients. Our results show that chloroquine decreased AML cell viability and proliferation for the majority of patients. Furthermore, a subgroup of AML patients showed a greater susceptibility to chloroquine, and using hierarchical cluster analysis, we identified 99 genes upregulated in this patient subgroup, including several genes related to leukemogenesis. The combination of chloroquine with low-dose cytarabine had an additive inhibitory effect on AML cell proliferation. Finally, a minority of patients showed increased extracellular constitutive mediator release in the presence of chloroquine, which was associated with strong antiproliferative effects of chloroquine as well as cytarabine. We conclude that chloroquine has antileukemic activity and should be further explored as a therapeutic drug against AML in combination with other cytotoxic or metabolic drugs; however, due to the patient heterogeneity, chloroquine therapy will probably be effective only for selected patients.

Autophagy and Metabolism in Normal and Malignant Hematopoiesis

The hematopoietic system relies on regulation of both metabolism and autophagy to maintain its homeostasis, ensuring the self-renewal and multipotent differentiation potential of hematopoietic stem cells (HSCs). HSCs display a distinct metabolic profile from that of their differentiated progeny, while metabolic rewiring from glycolysis to oxidative phosphorylation (OXPHOS) has been shown to be crucial for effective hematopoietic differentiation. Autophagy-mediated regulation of metabolism modulates the distinct characteristics of quiescent and differentiating hematopoietic cells. In particular, mitophagy determines the cellular mitochondrial content, thus modifying the level of OXPHOS at the different differentiation stages of hematopoietic cells, while, at the same time, it ensures the building blocks and energy for differentiation. Aberrations in both the metabolic status and regulation of the autophagic machinery are implicated in the development of hematologic malignancies, especially in leukemogenesis. In this review, we aim to investigate the role of metabolism and autophagy, as well as their interconnections, in normal and malignant hematopoiesis.

Autophagy a Close Relative of AML Biology

Simple Summary

Acute myeloid leukemia (AML) is the most common acute leukemia in adults. Despite a high rate of complete remission following conventional chemotherapy, the prognosis remains poor due to frequent relapses caused by relapse-initiating leukemic cells (RICs), which are resistant to chemotherapies. While the development of new targeted therapies holds great promise (e.g., molecules targeting IDH1/2, FLT3, BCL2), relapses still occur. Therefore, a paramount issue in the elimination of RICs is to decipher the AML resistance mechanisms. Thus, it has been recently shown that AML cells exhibit metabolic changes in response to chemotherapy or targeted therapies. Autophagy is a major regulator of cell metabolism, involved in maintaining cancer state, metastasis, and resistance to anticancer therapy. However, whether autophagy acts as a tumor suppressor or promoter in AML is still a matter of debate. Therefore, depending on molecular AML subtypes or treatments used, a better understanding of the role of autophagy is needed to determine whether its modulation could result in a clinical benefit.

Abstract

Autophagy, which literally means “eat yourself”, is more than just a lysosomal degradation pathway. It is a well-known regulator of cellular metabolism and a mechanism implicated in tumor initiation/progression and therapeutic resistance in many cancers. However, whether autophagy acts as a tumor suppressor or promoter is still a matter of debate. In acute myeloid leukemia (AML), it is now proven that autophagy supports cell proliferation in vitro and leukemic progression in vivo. Mitophagy, the specific degradation of mitochondria through autophagy, was recently shown to be required for leukemic stem cell functions and survival, highlighting the prominent role of this selective autophagy in leukemia initiation and progression. Moreover, autophagy in AML sustains fatty acid oxidation through lipophagy to support mitochondrial oxidative phosphorylation (OxPHOS), a hallmark of chemotherapy-resistant cells. Nevertheless, in the context of therapy, in AML, as well as in other cancers, autophagy could be either cytoprotective or cytotoxic, depending on the drugs used. This review summarizes the recent findings that mechanistically show how autophagy favors leukemic transformation of normal hematopoietic stem cells, as well as AML progression and also recapitulates its ambivalent role in resistance to chemotherapies and targeted therapies.

Furin-instructed aggregated gold nanoparticles for re-educating tumor associated macrophages and overcoming breast cancer chemoresistance

Insufficient drug accumulation and chemoresistance remain two major challenges in cancer chemotherapy. Herein, we designed a furin-responsive aggregated nanoplatform loaded with doxorubicin (DOX) and hydroxychloroquine (HCQ) (AuNPs-D&H-R&C) to combine chemotherapy, autophagy inhibition and macrophage polarization. AuNPs-D&H-R&C could passively target breast tumor via enhanced permeability and retention (EPR) effect after systemic administration and further aggregate together triggered by furin overexpressed in breast cancer. The in situ aggregations hindered the back-flow of NPs to the bloodstream and exocytosis of tumor cells, leading to enhanced drug accumulation within tumors. Moreover, upon exposure to acidic pH in the endosomes/lysosomes, HCQ was efficiently released and it inhibited autophagy and thus restored the sensitivity of tumor cell to DOX. Meanwhile, autophagy inhibition could reprogram tumor-promoting M2-like TAMs to anti-tumor M1 phenotype, exerting a synergistic effect in overcoming chemoresistance. In vitro studies demonstrated the superiority of furin-triggered aggregated AuNPs delivery system in enhancing drug accumulation in breast tumor, compared with PEGlyated AuNPs. The co-delivery of DOX and HCQ showed much improved chemotherapeutic efficiency to chemoresistant MCF-7/ADR breast tumor, in large part due to macrophage polarization. In conclusion, we developed a stimulus-responsive delivery system and proposed a potential combination strategy to overcome chemoresistance in cancer chemotherapy.

Identification and validation of signal recognition particle 14 as a prognostic biomarker predicting overall survival in patients with acute myeloid leukemia

BACKGROUND

This study aimed to determine and verify the prognostic value and potential functional mechanism of signal recognition particle 14 (SRP14) in acute myeloid leukemia (AML) using a genome-wide expression profile dataset.

METHODS

We obtained an AML genome-wide expression profile dataset and clinical prognostic data from The Cancer Genome Atlas (TCGA) and GSE12417 databases, and explored the prognostic value and functional mechanism of SRP14 in AML using survival analysis and various online tools.

RESULTS

Survival analysis showed that AML patients with high SRP14 expression had poorer overall survival than patients with low SRP14 expression. Time-dependent receiver operating characteristic curves indicated that SRP14 had good accuracy for predicting the prognosis in patients with AML. Genome-wide co-expression analysis suggested that SRP14 may play a role in AML by participating in the regulation of biological processes and signaling pathways, such as cell cycle, cell adhesion, mitogen-activated protein kinase, tumor necrosis factor, T cell receptor, DNA damage response, and nuclear factor-kappa B (NF-κB) signaling. Gene set enrichment analysis indicated that SRP14 was significantly enriched in biological processes and signaling pathways including regulation of hematopoietic progenitor cell differentiation and stem cell differentiation, intrinsic apoptotic signaling pathway by p53 class mediator, interleukin-1, T cell mediated cytotoxicity, and NF-κB-inducing kinase/NF-κB signaling. Using the TCGA AML dataset, we also identified four drugs (phenazone, benzydamine, cinnarizine, antazoline) that may serve as SRP14-targeted drugs in AML.

CONCLUSION

The current results revealed that high SRP14 expression was significantly related to a poor prognosis and may serve as a prognostic biomarker in patients with AML.

Inhibiting autophagy targets human leukemic stem cells and hypoxic AML blasts by disrupting mitochondrial homeostasis

Leukemia stem cells (LSCs) and therapy-resistant acute myeloid leukemia (AML) blasts contribute to the reinitiation of leukemia after remission, necessitating therapeutic interventions that target these populations. Autophagy is a prosurvival process that allows for cells to adapt to a variety of stressors. Blocking autophagy pharmacologically by using mechanistically distinct inhibitors induced apoptosis and prevented colony formation in primary human AML cells. The most effective inhibitor, bafilomycin A1 (Baf A1), also prevented the in vivo maintenance of AML LSCs in NSG mice. To understand why Baf A1 exerted the most dramatic effects on LSC survival, we evaluated mitochondrial function. Baf A1 reduced mitochondrial respiration and stabilized PTEN-induced kinase-1 (PINK-1), which initiates autophagy of mitochondria (mitophagy). Interestingly, with the autophagy inhibitor chloroquine, levels of enhanced cell death and reduced mitochondrial respiration phenocopied the effects of Baf A1 only when cultured in hypoxic conditions that mimic the marrow microenvironment (1% O2). This indicates that increased efficacy of autophagy inhibitors in inducing AML cell death can be achieved by concurrently inducing mitochondrial damage and mitophagy (pharmacologically or by hypoxic induction) and blocking mitochondrial degradation. In addition, prolonged exposure of AML cells to hypoxia induced autophagic flux and reduced chemosensitivity to cytarabine (Ara-C), which was reversed by autophagy inhibition. The combination of Ara-C with Baf A1 also decreased tumor burden in vivo. These findings demonstrate that autophagy is critical for mitochondrial homeostasis and survival of AML cells in hypoxia and support the development of autophagy inhibitors as novel therapeutic agents for AML.

Inhibition of Autophagy Does Not Re-Sensitize Acute Myeloid Leukemia Cells Resistant to Cytarabine

Elevated activation of the autophagy pathway is currently thought to be one of the survival mechanisms allowing therapy-resistant cancer cells to escape elimination, including for cytarabine (AraC)-resistant acute myeloid leukemia (AML) patients. Consequently, the use of autophagy inhibitors such as chloroquine (CQ) is being explored for the re-sensitization of AraC-resistant cells. In our study, no difference in the activity of the autophagy pathway was detected when comparing AraC-Res AML cell lines to parental AraC-sensitive AML cell lines. Furthermore, treatment with autophagy inhibitors CQ, 3-Methyladenine (3-MA), and bafilomycin A1 (BafA1) did not re-sensitize AraC-Res AML cell lines to AraC treatment. However, in parental AraC-sensitive AML cells, treatment with AraC did activate autophagy and, correspondingly, combination of AraC with autophagy inhibitors strongly reduced cell viability. Notably, the combination of these drugs also yielded the highest level of cell death in a panel of patient-derived AML samples even though not being additive. Furthermore, there was no difference in the cytotoxic effect of autophagy inhibition during AraC treatment in matched de novo and relapse samples with differential sensitivity to AraC. Thus, inhibition of autophagy may improve AraC efficacy in AML patients, but does not seem warranted for the treatment of AML patients that have relapsed with AraC-resistant disease.

Recent developments in autophagy-targeted therapies in cancer

Autophagy plays a crucial role in cellular development and differentiation as well as in the maintenance of homeostasis in healthy cells. Autophagy is well documented in neurodegenerative disorders, aging, and infectious diseases. However, recognizing its significance in cancer has always been challenging due to its tumor-promoting and suppressive attributes. Various modulators targeting key components of autophagy machinery directly or indirectly have been developed over the years, and have shown promising results in preclinical models. Some of these compounds are even being tested in clinical trials for safety and efficacy. A detailed review of strategies used to target autophagy in cancer is presented including our opinion on developing better therapies and outstanding issues.

Reductive regulation of BECN1 gene in adult Egyptian patients with do novo AML

Background

Acute myeloid leukaemia (AML) is a clonal haematopoietic disease characterized by the proliferation of immature blast cells in the bone marrow and peripheral blood. Autophagy is an inherent cellular route by which waste macromolecules are engulfed within autophagosomes prior to their fusion with cytoplasmic lysosomes for degradation. The BECN1 gene encodes the Beclin-1 protein, which regulates autophagy. Few reports have investigated BECN1 gene expression and its value in AML patients.

Results

This randomized case-control study included 50 newly diagnosed AML patients, in addition to 20 subjects as a control group. BECN1 gene expression was assessed using real-time quantitative polymerase chain reaction (qRT-PCR).

The median level of BECN1 gene expression in AML patients was 0.41 (IQR 0.29–1.03) in comparison to 1.12 (IQR 0.93–1.26) in the control group (P = 0.000). Seventy-two percent of AML patients showed reduced BECN1 gene expression, which was highly significantly associated with intermediate and adverse cytogenetic risk. Reduced BECN1 gene expression was associated with older age, higher total leukocyte counts, the presence of peripheral blood blast cells, a higher percentage of bone marrow blast cells, and higher expression of CD34 and CD117. FLT3-ITD mutation was detected in 14 patients (38.9%), all of whom showed reduced BECN1 gene expression (P = 0.006). BECN1 gene expression was also reduced in non-responder AML patients, with a highly statistically significant difference (P = 0.002).

Conclusion

A reduction in BECN1 gene expression might indicate a poor prognosis in adult Egyptian patients with de novo AML. Decreased BECN1 gene expression is associated with a higher risk of resistance to treatment. Targeting autophagy pathways may help in the treatment of AML patients.

Triangular Relationship between p53, Autophagy, and Chemotherapy Resistance

Chemotherapy and radiation often induce a number of cellular responses, such as apoptosis, autophagy, and senescence. One of the major regulators of these processes is p53, an essential tumor suppressor that is often mutated or lost in many cancer types and implicated in early tumorigenesis. Gain of function (GOF) p53 mutations have been implicated in increased susceptibility to drug resistance, by compromising wildtype anti-tumor functions of p53 or modulating key p53 processes that confer chemotherapy resistance, such as autophagy. Autophagy, a cellular survival mechanism, is initially induced in response to chemotherapy and radiotherapy, and its cytoprotective nature became the spearhead of a number of clinical trials aimed to sensitize patients to chemotherapy. However, increased pre-clinical studies have exemplified the multifunctional role of autophagy. Additionally, compartmental localization of p53 can modulate induction or inhibition of autophagy and may play a role in autophagic function. The duality in p53 function and its effects on autophagic function are generally not considered in clinical trial design or clinical therapeutics; however, ample pre-clinical studies suggest they play a role in tumor responses to therapy and drug resistance. Further inquiry into the interconnection between autophagy and p53, and its effects on chemotherapeutic responses may provide beneficial insights on multidrug resistance and novel treatment regimens for chemosensitization.

Challenges and Therapeutic Opportunities of Autophagy in Cancer Therapy

Simple Summary

Autophagy is a physiological process characterized by the degradation of the cell components through lysosomes due to stimuli/stress. In this study, we review the challenges and therapeutic opportunities that autophagy presents in the treatment of cancer. We discussed the results of several studies that evaluated autophagy as a therapeutic strategy in cancer, both through the modulation of therapeutic resistance and the death of cancer cells. Moreover, we discussed the role of autophagy in the biology of cancer stem cells and the inhibition of this process as a strategy to overcome resistance and progression of cancer stem cells.

Abstract

Autophagy is a physiological cellular process that is crucial for development and can occurs in response to nutrient deprivation or metabolic disorders. Interestingly, autophagy plays a dual role in cancer cells—while in some situations, it has a cytoprotective effect that causes chemotherapy resistance, in others, it has a cytotoxic effect in which some compounds induce autophagy-mediated cell death. In this review, we summarize strategies aimed at autophagy for the treatment of cancer, including studies of drugs that can modulate autophagy-mediated resistance, and/or drugs that cause autophagy-mediated cancer cell death. In addition, the role of autophagy in the biology of cancer stem cells has also been discussed.

Effects of different autophagy inhibitors on sensitizing KG-1 and HL-60 leukemia cells to chemotherapy

A little number of current autophagy inhibitors may have beneficial effects on the acute myeloid leukemia (AML) patients. However, there is a strong need to figure out which settings should be activated or inhibited in autophagy pathway to prevail drug resistance and also to improve current treatment options in leukemia. Therefore, this study aimed to compare the effects of well-known inhibitors of autophagy (as 3-MA, BafA1, and HCQ) in leukemia KG-1 and HL-60 cells exposed to arsenic trioxide (ATO) and/or all-trans retinoic acid (ATRA). Cell proliferation and cytotoxicity of cells were examined by MTT assay. Autophagy was studied by evaluating the development of acidic vesicular organelles, and the autophagosomes formation was investigated by acridine orange staining and transmission electron microscopy. Moreover, the gene and protein expressions levels of autophagy markers (ATGs, p62/SQSTM1, and LC-3B) were also performed by qPCR and western blotting, respectively. The rate of apoptosis and cell cycle were evaluated using flow cytometry. We compared the cytotoxic and apoptotic effects of ATO and/or ATRA in both cell lines and demonstrated that some autophagy markers upregulated in this context. Also, it was shown that autophagy blockers HCQ and/or BafA1 could potentiate the cytotoxic effects of ATO/ATRA, which were more pronounced in KG-1 cells compared to HL-60 cell line. This study showed the involvement of autophagy during the treatment of KG-1 and HL-60 cells by ATO/ATRA. This study proposed that therapy of ATO/ATRA in combination with HCQ can be considered as a more effective strategy for targeting leukemic KG-1 cells.

Various Aspects of Calcium Signaling in the Regulation of Apoptosis, Autophagy, Cell Proliferation, and Cancer

Calcium (Ca²⁺) is a major second messenger in cells and is essential for the fate and survival of all higher organisms. Different Ca²⁺ channels, pumps, or exchangers regulate variations in the duration and levels of intracellular Ca²⁺, which may be transient or sustained. These changes are then decoded by an elaborate toolkit of Ca²⁺-sensors, which translate Ca²⁺ signal to intracellular operational cell machinery, thereby regulating numerous Ca²⁺-dependent physiological processes. Alterations to Ca²⁺ homoeostasis and signaling are often deleterious and are associated with certain pathological states, including cancer. Altered Ca²⁺ transmission has been implicated in a variety of processes fundamental for the uncontrolled proliferation and invasiveness of tumor cells and other processes important for cancer progression, such as the development of resistance to cancer therapies. Here, we review what is known about Ca²⁺ signaling and how this fundamental second messenger regulates life and death decisions in the context of cancer, with particular attention directed to cell proliferation, apoptosis, and autophagy. We also explore the intersections of Ca²⁺ and the therapeutic targeting of cancer cells, summarizing the therapeutic opportunities for Ca²⁺ signal modulators to improve the effectiveness of current anticancer therapies.

Antileukemic activity of the VPS34-IN1 inhibitor in acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive disease with a poor prognosis. Vacuolar protein sorting 34 (VPS34) is a member of the phosphatidylinositol-3-kinase lipid kinase family that controls the canonical autophagy pathway and vesicular trafficking. Using a recently developed specific inhibitor (VPS34-IN1), we found that VPS34 inhibition induces apoptosis in AML cells but not in normal CD34+ hematopoietic cells. Complete and acute inhibition of VPS34 was required for the antileukemic activity of VPS34-IN1. This inhibitor also has pleiotropic effects against various cellular functions related to class III PI3K in AML cells that may explain their survival impairment. VPS34-IN1 inhibits basal and L-asparaginase-induced autophagy in AML cells. A synergistic cell death activity of this drug was also demonstrated. VPS34-IN1 was additionally found to impair vesicular trafficking and mTORC1 signaling. From an unbiased approach based on phosphoproteomic analysis, we identified that VPS34-IN1 specifically inhibits STAT5 phosphorylation downstream of FLT3-ITD signaling in AML. The identification of the mechanisms controlling FLT3-ITD signaling by VPS34 represents an important insight into the oncogenesis of AML and could lead to new therapeutic strategies.

The role of autophagy in targeted therapy for acute myeloid leukemia

Although molecular targeted therapies have recently displayed therapeutic effects in acute myeloid leukemia (AML), limited response and acquired resistance remain common problems. Numerous studies have associated autophagy, an essential degradation process involved in the cellular response to stress, with the development and therapeutic response of cancers including AML. Thus, we review studies on the role of autophagy in AML development and summarize the linkage between autophagy and several recurrent genetic abnormalities in AML, highlighting the potential of capitalizing on autophagy modulation in targeted therapy for AML.Abbreviations: AML: acute myeloid leukemia; AMPK: AMP-activated protein kinase; APL: acute promyelocytic leukemia; ATG: autophagy related; ATM: ATM serine/threonine kinase; ATO: arsenic trioxide; ATRA: all trans retinoic acid; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; BET proteins, bromodomain and extra-terminal domain family; CMA: chaperone-mediated autophagy; CQ: chloroquine; DNMT, DNA methyltransferase; DOT1L: DOT1 like histone lysine methyltransferase; FLT3: fms related receptor tyrosine kinase 3; FIS1: fission, mitochondrial 1; HCQ: hydroxychloroquine; HSC: hematopoietic stem cell; IDH: isocitrate dehydrogenase; ITD: internal tandem duplication; KMT2A/MLL: lysine methyltransferase 2A; LSC: leukemia stem cell; MDS: myelodysplastic syndromes; MTORC1: mechanistic target of rapamycin kinase complex 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; NPM1: nucleophosmin 1; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PML: PML nuclear body scaffold; ROS: reactive oxygen species; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SAHA: vorinostat; SQSTM1: sequestosome 1; TET2: tet methylcytosine dioxygenase 2; TKD: tyrosine kinase domain; TKI: tyrosine kinase inhibitor; TP53/p53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VPA: valproic acid; WDFY3/ALFY: WD repeat and FYVE domain containing 3.

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.

LncRNA LINC00265/miR-485-5p/IRF2-mediated autophagy suppresses apoptosis in acute myeloid leukemia cells

BACKGROUND

Extensive studies have shown that long non-coding RNAs (lncRNAs) play important roles in multiple cancers. The present study aimed to investigate the role and mechanism of lncRNA LINC00265 in the regulation of apoptosis in acute myeloid leukemia (AML) cells.

METHODS

Gain- or loss-of-function experiments were conducted in AML cells to explore the effect of LINC00265 on AML. Autophagy was assessed by examining levels of Beclin-1, p62, and ratio of LC3-II/LC3-I. Cell proliferation and apoptosis of AML cells were evaluated by CCK-8 assay and flow cytometry, respectively. RNA pull-down was performed to enrich miR-485-5p interacted with LINC00265. The interaction between miR-485-5p and IRF2 3'UTR was analyzed by luciferase reporter assay.

RESULTS

LINC00265 expression was significantly up-regulated, whereas miR-485-5p was down-regulated in serum of AML patients and AML cell lines. LINC00265 promoted, whereas miR-485-5p suppressed autophagy in AML cells. Mechanistically, LINC00265 functioned as a ceRNA for miR-485-5p to facilitate IRF2 expression. More importantly, LINC00265 overexpression or miR-485-5p inhibitor reversed the 3-methyladenine (3-MA, an autophagy inhibitor)-mediated proliferation-inhibitory and pro-apoptotic effects, whereas LINC00265 silencing or miR-485-5p mimic overturned the proliferation-promoting and anti-apoptotic effects of autophagy activator rapamycin.

CONCLUSION

LINC00265 attenuates AML cell apoptosis by inducing autophagy via miR-485/IRF2 axis.

Long non-coding RNA UCA1 promotes autophagy by targeting miR-96-5p in acute myeloid leukaemia

Long non-coding RNA (lncRNA) urothelial carcinoma-associated 1 (UCA1) has been identified as an oncogene and is involved in acute myeloid leukaemia (AML). Autophagy contributes to tumourigenesis and cancer cell survival. The purpose of this study was to investigate the regulatory role and mechanism of UCA1 in AML cell viability by its effect on autophagy. The expression of UCA1, miR-96-5p, and ATG7 was determined by qRT-PCR and western blot. Cell proliferation was examined by MTT assay. The autophagy level was assessed by green fluorescent protein (GFP)-LC3 immunofluorescence and western blot. The interaction between UCA1 and miR-96-5p or ATG7 was analyzed by luciferase reporter activity. The results showed that UCA1 promoted AML cell proliferation by inducing autophagy. Mechanistically, UCA1 acted as a sponge of miR-96-5p by binding to miR-96-5p. ATG7 was a direct target of miR-96-5p and positively regulated by UCA1. Further results showed that the miR-96-5p mimic effectively counteracted the UCA1 overexpression-mediated induction of the ATG7/autophagy pathway. Collectively, UCA1 functions as a sponge of miR-96-5p to upregulate its target ATG7, thereby resulting in autophagy induction. Our findings reveal a UCA1-mediated molecular mechanism responsible for autophagy induction in AML and help to improve the understanding of the molecular mechanism of AML progression.

Oxidative resistance of leukemic stem cells and oxidative damage to hematopoietic stem cells under pro-oxidative therapy

Leukemic stem cells (LSCs) and hematopoietic stem cells (HSCs) are both dependent on the hypoxic bone marrow (BM) microenvironment (also known as the BM niche). There is always fierce competition between the two types of cells, and the former exhibits a greater competitive advantage than the latter via multiple mechanisms. Under hypoxia, the dynamic balance between the generation and clearing of intracellular reactive oxygen species (ROS) is conducive to maintaining a quiescent state of cells. Quiescent LSCs can reside well in the BM niche, avoiding attack by chemotherapeutic agents, which is the cause of chemotherapeutic resistance and relapse in leukemia. HSCs acquire energy mainly through anaerobic glycolysis, whereas LSCs achieve energy metabolism largely through mitochondrial oxidative respiration. Mitochondria are the primary site of ROS generation. Thus, in theory, mitochondria-mediated respiration will cause an increase in ROS generation in LSCs and a higher intracellular oxidative stress level. The sensitivity of the cells to pro-oxidant drugs increases as well, which allows for the selective clearing of LSCs by pro-oxidative therapy. However, HSCs are also highly sensitive to changes in ROS levels, and the toxic effects of pro-oxidant drugs on HSCs poses a major challenge to pro-oxidative therapy in leukemia. Given the above facts, we reviewed studies on the oxidative resistance of LSCs and the oxidative damage to HSCs under pro-oxidative therapy. An in-depth investigation into the oxidative stress status and regulatory mechanisms of LSCs and HSCs in hypoxic environments will promote our understanding of the survival strategy employed by LSCs and the mechanism of the oxidative damage to HSCs in the BM niche, thus facilitating individualized treatment of leukemia patients and helping eliminate LSCs without disturbing normal hematopoietic cells.