Autophagy in blood cancers: biological role and therapeutic implications

The association and application of sonodynamic therapy and autophagy in diseases

Sonodynamic therapy (SDT) is a new non-invasive treatment method proposed based on photodynamic therapy (PDT). It has advantages such as high precision, strong tissue penetration, minimal side effects, and good patient compliance. With the maturation of nanomedicine, the application of nanosonosensitizers has further propelled the development of SDT. In recent years, people have developed many new types of sonosensitizers and explored the mechanisms of SDT. Among them, the studies about the relationship between autophagy and SDT have attracted increasing attention. After the SDT, cells usually undergo autophagy as a self-protective mechanism to resist external stimuli and reduce cell damage, which is beneficial for the treatment of atherosclerosis (AS), diabetes, and myocardial infarction but counterproductive in cancer treatment. However, under certain treatment conditions, excessive upregulation of autophagy can also promote cell death, which is beneficial for cancer treatment. This article reviews the latest research progress on the relationship between SDT and autophagy in cancers, AS, diabetes, and myocardial infarction. We also discuss and propose the challenges and prospects in enhancing SDT efficacy by regulating autophagy, with the hope of promoting the development of this promising therapeutic approach.

Changes in inflammatory responses and autophagy during apheresis platelet preservation and their correlation with platelet transfusion refractoriness in patients with acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a common hematopoietic malignancy, and platelet transfusion plays a crucial role in its treatment. This study aimed to investigate the changes in inflammatory response and autophagy during the preservation of apheresis platelets (AP) and their correlation with platelet transfusion refractoriness (PTR) in ALL. ALL patients were included, and APs were categorized based on the preservation period (day 0, day 1, days 2-3, and days 4-5). The activation factors procaspase-activating compound 1 (PAC-1) and P-selectin (CD62P), AP aggregation function, inflammation levels (interleukin 1 beta [IL-1β], interleukin 6 [IL-6], tumor necrosis factor alpha [TNF-α] and NOD-like receptor thermal protein domain associated protein 3 [NLRP3]), and autophagy-related genes (p62) during AP preservation were assessed. Following co-culturing APs with peripheral blood mononuclear cells (PBMCs), specific activation markers were studied to observe APs influence on immune cells activation. The effectiveness of platelet transfusion was assessed, and risk factors for PTR were analyzed. As the storage duration of AP increased, the activation factors, coagulation factor activity, inflammation levels, and the activation of immune cells in AP increased, while fibrinogen levels and AP aggregation function decreased. The expression levels of autophagy-related genes (the autophagy marker light chain 3B gene [LC3B] and Beclin 1 gene) decreased with prolongation preservation. The effective rate of AP transfusion in ALL patients was 68.21%. AP preservation time, IL-6, p62, and Beclin 1 were identified as independent risk factors affecting PTR in ALL patients. In conclusion, during AP preservation, inflammation, autophagy, and activation of immune cells were observed to increase. AP preservation time, IL-6, p62, and Beclin 1 were independent risk factors for PTR.

Retracted: Britannin mediates apoptosis and glycolysis of T-cell lymphoblastic lymphoma cells by AMPK-dependent autophagy

The above article, published online on 19 September 2022 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/abs/10.1002/jbt.23211), has been retracted by agreement between the authors, the journal Editor in Chief, Hari Bhat, and Wiley Periodicals, LLC. The article is being retracted at the authors' request because some of the data underlying this article refer to a different cell line from the one reported in it. As a result, the article's conclusions do not accurately reflect the full data and cannot be considered reliable.

Interruption of p53-MDM2 Interaction by Nutlin-3a in Human Lymphoma Cell Models Initiates a Cell-Dependent Global Effect on Transcriptome and Proteome Level

In most lymphomas, p53 signaling pathway is inactivated by various mechanisms independent to p53 gene mutations or deletions. In many cases, p53 function is largely regulated by alterations in the protein abundance levels by the action of E3 ubiquitin-protein ligase MDM2, targeting p53 to proteasome-mediated degradation. In the present study, an integrating transcriptomics and proteomics analysis was employed to investigate the effect of p53 activation by a small-molecule MDM2-antagonist, nutlin-3a, on three lymphoma cell models following p53 activation. Our analysis revealed a system-wide nutlin-3a-associated effect in all examined lymphoma types, identifying in total of 4037 differentially affected proteins involved in a plethora of pathways, with significant heterogeneity among lymphomas. Our findings include known p53-targets and novel p53 activation effects, involving transcription, translation, or degradation of protein components of pathways, such as a decrease in key members of PI3K/mTOR pathway, heat-shock response, and glycolysis, and an increase in key members of oxidative phoshosphorylation, autophagy and mitochondrial translation. Combined inhibition of HSP90 or PI3K/mTOR pathway with nutlin-3a-mediated p53-activation enhanced the apoptotic effects suggesting a promising strategy against human lymphomas. Integrated omic profiling after p53 activation offered novel insights on the regulatory role specific proteins and pathways may have in lymphomagenesis.

High BECN1 Expression Negatively Correlates with BCL2 Expression and Predicts Better Prognosis in Diffuse Large B-Cell Lymphoma: Role of Autophagy

Diffuse large B-cell lymphoma (DLBCL) is characterized by high molecular and clinical heterogeneity. Autophagy, a lysosome-driven catabolic process devoted to macromolecular turnover, is fundamental in maintaining normal hematopoietic stem cells and progenitors homeostasis, and its dysregulation plays a critical role in the initiation and progression of hematological malignancies. One main regulator of autophagy is BECLIN-1, which may interact alternatively with either BCL-2, thus allowing apoptosis, or PI3KC3, thus promoting autophagy. The altered expression of BCL2 and BECN1 correlates with lymphoma outcomes, but whether this is associated with dysregulated cross-talk between autophagy and apoptosis remains to be elucidated. Analysis of the TCGA database revealed that BCL2 and BECN1 mRNA expression were inversely correlated in DLBCL patients. In representative DLBCL cell lines exposed to doxorubicin, the cells highly expressing BCL-2 were resistant, while the ones highly expressing BECLIN-1 were sensitive, and this correlated with low and high autophagy flux, respectively. Venetoclax targeting of BCL-2 increased while the spautin-1-mediated inhibition of BECLIN-1-dependent autophagy reversed doxorubicin sensitivity in the former and in the latter, respectively. By interrogating the TCGA DLBCL dataset, we found that BCL2 and BECN1 acted as negative and positive prognostic markers for DLBCL, respectively. The differentially expressed gene analysis in the respective cohorts revealed that BCL2 positively correlated with oncogenic pathways (e.g., glucose transport, HIF1A signaling, JAK-STAT signaling, PI3K-AKT-mTOR pathway) and negatively correlated with autophagy-related transcripts, while BECN1 showed the opposite trend. Notably, patients with high BECN1 expression displayed longer survival. Our data reveal, for the first time, that the modulation of BECLIN-1-dependent autophagy influences the prognosis of DLBCL patients and provide a mechanistic explanation supporting the therapeutic use of drugs that, by stimulating autophagy, can sensitize lymphoma cells to chemotherapy.

Apoptosis in megakaryocytes: Safeguard and threat for thrombopoiesis

Platelets, generated from precursor megakaryocytes (MKs), are central mediators of hemostasis and thrombosis. The process of thrombopoiesis is extremely complex, regulated by multiple factors, and related to many cellular events including apoptosis. However, the role of apoptosis in thrombopoiesis has been controversial for many years. Some researchers believe that apoptosis is an ally of thrombopoiesis and platelets production is apoptosis-dependent, while others have suggested that apoptosis is dispensable for thrombopoiesis, and is even inhibited during this process. In this review, we will focus on this conflict, discuss the relationship between megakaryocytopoiesis, thrombopoiesis and apoptosis. In addition, we also consider why such a vast number of studies draw opposite conclusions of the role of apoptosis in thrombopoiesis, and try to figure out the truth behind the mystery. This review provides more comprehensive insights into the relationship between megakaryocytopoiesis, thrombopoiesis, and apoptosis and finds some clues for the possible pathological mechanisms of platelet disorders caused by abnormal apoptosis.

KIF23 promotes autophagy-induced imatinib resistance in chronic myeloid leukaemia through activating Wnt/β-catenin pathway

Imatinib, an inhibitor of tyrosine kinase, shows remarkable efficacy in chronic myeloid leukaemia (CML). Autophagy protects tumour cells against chemotherapeutic stimulation and contributes to imatinib resistance in CML. Kinesin family member 23 (KIF23) is involved in cytokinesis and associated with autophagy. The role of KIF23 in autophagy-induced imatinib resistance in CML was investigated. First, to induce drug resistance, CML cells were exposed to increasing concentrations of imatinib. The concentration of imatinib resistance in CML cells was screened through upregulation of 50% inhibitory concentration (IC₅₀ ) values. KIF23 was elevated in imatinib-resistant tissues and cells of CML. Second, knockdown of KIF23 reduced IC₅₀ values of imatinib-resistant CML cells to imatinib. Moreover, silence of KIF23 also suppressed cell proliferation and promoted apoptosis of imatinib-resistant CML cells. Third, immunofluorescence analysis showed that the number of LC3 bright spots in imatinib-resistant CML cells was reduced by silence of KIF23. Knockdown of KIF23 upregulated p62 expression and downregulated the expression ratio of LC3-II to LC3-I in imatinib-resistant CML cells. Last, silence of KIF23 decreased nuclear β-catenin and increased cytoplasmic β-catenin in imatinib-resistant CML cells. Activator of Wnt/β-catenin attenuated KIF23 silence-induced increase of apoptosis and decrease of autophagy in imatinib-resistant CML cells. In conclusion, loss of KIF23 repressed autophagy-induced imatinib resistance in CML cells through inactivation of Wnt/β-catenin pathway.

New Visions on Natural Products and Cancer Therapy: Autophagy and Related Regulatory Pathways

Macroautophagy (autophagy) has been a highly conserved process throughout evolution and allows cells to degrade aggregated/misfolded proteins, dysfunctional or superfluous organelles and damaged macromolecules, in order to recycle them for biosynthetic and/or energetic purposes to preserve cellular homeostasis and health. Changes in autophagy are indeed correlated with several pathological disorders such as neurodegenerative and cardiovascular diseases, infections, cancer and inflammatory diseases. Conversely, autophagy controls both apoptosis and the unfolded protein response (UPR) in the cells. Therefore, any changes in the autophagy pathway will affect both the UPR and apoptosis. Recent evidence has shown that several natural products can modulate (induce or inhibit) the autophagy pathway. Natural products may target different regulatory components of the autophagy pathway, including specific kinases or phosphatases. In this review, we evaluated ~100 natural compounds and plant species and their impact on different types of cancers via the autophagy pathway. We also discuss the impact of these compounds on the UPR and apoptosis via the autophagy pathway. A multitude of preclinical findings have shown the function of botanicals in regulating cell autophagy and its potential impact on cancer therapy; however, the number of related clinical trials to date remains low. In this regard, further pre-clinical and clinical studies are warranted to better clarify the utility of natural compounds and their modulatory effects on autophagy, as fine-tuning of autophagy could be translated into therapeutic applications for several cancers.

Autophagy in Hematological Malignancies

Simple Summary

Autophagy is a dynamic and tightly regulated process that seems to have dual effects in cancer. In some contexts, it can induce carcinogenesis and promote cancer cell survival, whereas in others, it acts preventing tumor cell growth and tumor progression. Thus, autophagy functions seem to strictly depend on cancer ontogenesis, progression, and type. Here, we will dive into the current knowledge of autophagy in hematological malignancies and will highlight the main genetic components involved in each cancer type.

Abstract

Autophagy is a highly conserved metabolic pathway via which unwanted intracellular materials, such as unfolded proteins or damaged organelles, are digested. It is activated in response to conditions of oxidative stress or starvation, and is essential for the maintenance of cellular homeostasis and other vital functions, such as differentiation, cell death, and the cell cycle. Therefore, autophagy plays an important role in the initiation and progression of tumors, including hematological malignancies, where damaged autophagy during hematopoiesis can cause malignant transformation and increase cell proliferation. Over the last decade, the importance of autophagy in response to standard pharmacological treatment of hematological tumors has been observed, revealing completely opposite roles depending on the tumor type and stage. Thus, autophagy can promote tumor survival by attenuating the cellular damage caused by drugs and/or stabilizing oncogenic proteins, but can also have an antitumoral effect due to autophagic cell death. Therefore, autophagy-based strategies must depend on the context to create specific and safe combination therapies that could contribute to improved clinical outcomes. In this review, we describe the process of autophagy and its role on hematopoiesis, and we highlight recent research investigating its role as a potential therapeutic target in hematological malignancies. The findings suggest that genetic variants within autophagy-related genes modulate the risk of developing hemopathies, as well as patient survival.

The Question of Survival or Death: What Is the Role of Autophagy in Acute Myeloid Leukemia (AML)?

Autophagy plays a critical role in balancing sources of energy in response to harsh conditions and nutrient deprivation. Autophagy allows cells to survive in harsh condition and also serve as a death mechanism. Any dysregulation in autophagy signaling may lead to several disorders. Autophagy has been proposed to explain chemotherapy resistance in acute myeloid leukemia (AML). This signaling pathway can either act as a tumor suppressive function or chemo-resistance mechanism. Conventional chemotherapy drugs enhance apoptosis and indicate clinical benefit, but in some cases, relapse and chemotherapy resistance are observed. In leukemia, autophagy may promote cell survival in response to chemotherapy drugs. Therefore, new strategies by inhibiting or activating autophagy may find a broad application for treating leukemia and may significantly enhance clinical outcomes. In this review, we discussed the dimensional role of autophagy in leukemia.

Autophagy Regulates VDAC3 Ubiquitination by FBXW7 to Promote Erastin-Induced Ferroptosis in Acute Lymphoblastic Leukemia

Background: The discovery of ferroptosis is a major breakthrough in the development of cancer treatments. However, the mechanism by which ferroptosis contributes to acute lymphoblastic leukemia (ALL) is to be clarified. Here, we explored erastin-induced ferroptosis in ALL cells and the impact of autophagic activity on this process.

Materials and Methods: Cell viability was evaluated in various ALL cell lines following erastin treatment by the MTS assay, while cell death was evaluated via a trypan blue assay. Immunoblotting and quantitative real-time PCR were used to detect protein and mRNA expression, respectively. The UbiBrowser database was used to predict the E3 ligase of VDAC3, which was confirmed by immunoprecipitation. The role of FBXW7 in erastin-induced ferroptosis in vitro was evaluated via lentiviral-mediated silencing and overexpression. ALL xenograft mice were used to observe the impact of autophagy on erastin-induced ferroptosis.

Results: Resistance to erastin-induced ferroptosis was higher in Jurkat and CCRF-CEM cells than in Reh cells. The sensitivity could be modified by the autophagy activator rapamycin (Rapa) and the autophagy inhibitor chloroquine (CQ). Rapa sensitized ALL cells to erastin-induced ferroptosis. In ALL xenograft mice, the combination treatment of Rapa and erastin resulted in longer survival time than those observed with erastin or Rapa treatment alone. VDAC3 was regulated by autophagy post-transcriptionally, mainly via the ubiquitin-proteasome system (UPS). FBXW7 was verified as a specific E3 ligase of VDAC3. FBXW7 knockdown attenuated VDAC3 degradation by suppressing its ubiquitination, thereby increasing the sensitivity of ALL cells to erastin.

Conclusion: Autophagy regulated erastin-induced ferroptosis via the FBXW7-VDAC3 axis. Rapa sensitized ALL cells to erastin-induced ferroptosis both in vitro and in vivo. Our findings provide potential therapeutic targets for ALL.

Octyl syringate is preferentially cytotoxic to cancer cells via lysosomal membrane permeabilization and autophagic flux inhibition

The autophagy-mediated lysosomal pathway plays an important role in conferring stress tolerance to tumor cells during cellular stress such as increased metabolic demands. Thus, targeted disruption of this function and inducing lysosomal cell death have been proved to be a useful cancer therapeutic approach. In this study, we reported that octyl syringate (OS), a novel phenolic derivate, was preferentially cytotoxic to various cancer cells but was significantly less cytotoxic to non-transformed cells. Treatment with OS resulted in non-apoptotic cell death in a caspase-independent manner. Notably, OS not only enhanced accumulation of autophagic substrates, including lapidated LC3 and sequestosome-1, but also inhibited their degradation via an autophagic flux. In addition, OS destabilized the lysosomal function, followed by the intracellular accumulation of the non-digestive autophagic substrates such as bovine serum albumin and stress granules. Furthermore, OS triggered the release of lysosomal enzymes into the cytoplasm that contributed to OS-induced non-apoptotic cell death. Finally, we demonstrated that OS was well tolerated and reduced tumor growth in mouse xenograft models. Taken together, our study identifies OS as a novel anticancer agent that induces lysosomal destabilization and subsequently inhibits autophagic flux and further supports development of OS as a lysosome-targeting compound in cancer therapy. • Octyl syringate, a phenolic derivate, is preferentially cytotoxic to various cancer cells. • Octyl syringate destabilizes the lysosomal function. • Octyl syringate blocks the autophagic flux. • Octyl syringate is a potential candidate compound for cancer therapy.

Utilizing network pharmacology to explore potential mechanisms of YiSui NongJian formula in treating myelodysplastic syndrome

The study aims to explore potential mechanisms of YiSui NongJian formula (YSNJF) in treating myelodysplastic syndromes (MDS) by network pharmacology-based strategy. Active compounds and corresponding potential therapeutic targets of YSNJF were harvested by utilizing the database of TCMSP (Traditional Chinese Medicine Systems Pharmacology) and BATMAN-TCM (Bioinformatics Analysis Tool for Molecular mechanism of Traditional Chinese Medicine). MDS targets were adopted from GeneCard, KEGG (Kyoto Encyclopedia of Genes and Genomes), TTD (Therapeutic Target Database), DrugBank, and DisGeNet. Then a network of YSNJF- compounds-target-MDS network was harvested. The protein–protein interaction (PPI) network was then generated by the Sting database and subjected to Cytoscape software to harvest major and core targets network by topological analysis. Genes from the core targets network were further subjected to Gene Ontology (GO) and KEGG enrichment analysis to figure out potential targeting pathways. Finally, a compounds-targets-pathways network was generated by Cytoscape. A total of 210 active compounds and 768 corresponding potential therapeutic targets were harvested from ingredients of YSNJF. MDS was shown to have 772 potential treating targets with 98 intersected targets corresponding to 98 active compounds in YSNJF. Topological analysis revealed that 15 targets formed the core PPI network. Further, GO and KEGG enrichment analysis revealed that those core targets were mainly enriched on cell cycle- and immune-related pathways. The present study revealed that therapeutic effects of YSNJF on MDS might be achieved through regulating cell cycle- and immune-related pathways.

Triangle collaboration assessment of autophagy, ER stress and hypoxia in leukemogenesis: a bright perspective on the molecular recognition of B-ALL

B-lineage acute lymphoblastic leukemia (B-ALL) is the most common acute leukemia in childhood and adults, which caused by many various crystalline and unclear agents. Owning to this matter, no significant progress has been made in the patients-recovery. Recently, autophagy pathway is considered as an ambiguous agent in leukemia evaluation. We aim to discover the expression levels of upstream autophagy-regulating genes in newly diagnosed B-ALL patients. In B-ALL group, BECN1, HIF1A and ERN1 expressions were significantly down-regulated, while BCL2 expression was up-regulated compared to the control group (p < .05). Moreover, there was significant positive correlation between the decreased BECN1 compared with Hypoxia and endoplasmic reticulum (ER) stress-related genes expression in the patients (p < .05). Our findings revealed that, ERN1 and ER stress pathway-related genes could be effective regulators of autophagy in B-ALL. More investigation is recommended to gain a deeper understanding into molecular pathophysiology of B-ALL to improve treatment and monitoring approaches in affected patients.

The Effect of Autophagic Activity on the Function of Apheresis Platelets and on the Efficacy of Clinical Platelet Transfusion

Platelet activation and survival jointly determine the efficacy of clinical platelet transfusion. This study aimed to discuss the effect of autophagic activity on activation and aggregation of apheresis platelets and on the efficacy of clinical platelet transfusion. In this study, we investigated the effects of autophagic activity of apheresis platelets for different blood types and after different storage durations on platelet activation and aggregation functions. By Western blot, immunofluorescence, and RT-qPCR detection, we found that with the prolongation of the storage duration, the expressions of both autophagy-related proteins and genes were upregulated in apheresis platelets and their expressions were insignificantly higher in the apheresis platelets of type A and O blood than in those of type B and type AB blood. After RAPA/IGF-1 pretreatment, there was a significant increase/reduction in autophagic activity. After RAPA and IGF-1 pretreatment, an opposite variation trend was observed with platelet activation and aggregation. Autophagic activity of platelets correlated negatively with the efficacy of clinical platelet transfusion. These research findings provide a theoretical basis for effective clinical platelet transfusion.

Induction of Apoptosis and Autophagy in Breast Cancer Cells by a Novel HDAC8 Inhibitor

Epigenetic therapy has been demonstrated to be a viable strategy for breast cancer treatment. In this study, we report the anti-tumor activity of a hydroxamate-based histone deacetylase (HDAC)8-selective inhibitor, HMC, in breast cancer cells. MTT assays showed that HMC inhibited cell viability of MCF-7 and MDA-MB-231 cells with IC₅₀ values of 7.7 μM and 9.5 μM, respectively. HMC induced caspase-dependent apoptosis in MCF-7 cells, which was associated with its ability to modulate a series of cell survival-related signaling effectors, including Akt, mTOR, Bax, Mcl-1, and Bcl-2. Additionally, HMC was capable of activating PPARγ, which was accompanied by reduced expression of PPARγ target gene products, such as cyclin D1 and CDK6. HMC increased the production of ROS in MCF-7 cells, which could be partially reversed by the cotreatment with a ROS scavenger (N-acetylcysteine or glutathione). Furthermore, HMC induced autophagy, as characterized by the formation of acidic vesicular organelles and autophagic biomarkers including LC3B-II and Atg5. Notably, pharmacological blockade of autophagy by 3-MA or CQ could attenuate HMC-induced apoptosis, suggesting that autophagy played a self-protective role in HMC-induced cell death. Together, these data suggest the translational potential of HMC to be developed into a potential therapeutic agent for breast cancer therapy.

Poly (ADP-ribosylation) of HMGB1 facilitates its acetylation and promotes HMGB1 translocation-associated chemotherapy-induced autophagy in leukaemia cells

Acute lymphoblastic leukaemia (ALL) is one of the most common and curable types of cancer in paediatric patients. However, chemotherapeutic resistance is a difficult but common obstacle when treating leukaemia in the clinical setting. Studies have demonstrated that drug resistance is partly attributable to autophagy induced by multiple chemotherapeutic agents. As an evolutionarily conserved non-histone chromatin-binding protein, high mobility group box protein 1 (HMGB1) is considered to be an important factor in autophagy, and regulates autophagy at multiple levels via different subcellular localisations. In the present study, it was revealed that chemotherapeutic drugs induced autophagy in leukaemia cells and that translocation of HMGB1 from the nucleus to the cytoplasm is an important molecular event in this process. It was further demonstrated that poly (ADP-ribosylation) of HMGB1 facilitates its acetylation, thereby inducing HMGB1 translocation and ultimately promoting chemotherapy-induced autophagy in leukaemic cells. Targeted HMGB1 translocation may overcome chemotherapy-induced autophagy in leukaemia.

Oncogenic KIT mutations induce STAT3-dependent autophagy to support cell proliferation in acute myeloid leukemia

Autophagy is associated with both survival and cell death in myeloid malignancies. Therefore, deciphering its role in different genetically defined subtypes of acute myeloid leukemia (AML) is critical. Activating mutations of the KIT receptor tyrosine kinase are frequently detected in core-binding factor AML and are associated with a greater risk of relapse. Herein, we report that basal autophagy was significantly increased by the KIT^D816V mutation in AML cells and contributed to support their cell proliferation and survival. Invalidation of the key autophagy protein Atg12 strongly reduced tumor burden and improved survival of immunocompromised NSG mice engrafted with KIT^D816V TF-1 cells. Downstream of KIT^D816V, STAT3, but not AKT or ERK pathways, was identified as a major regulator of autophagy. Accordingly, STAT3 pharmacological inhibition or downregulation inhibited autophagy and reduced tumor growth both in vitro and in vivo. Taken together, our results support the notion that targeting autophagy or STAT3 opens up an exploratory pathway for finding new therapeutic opportunities for patients with CBF-AML or others malignancies with KIT^D816V mutations.

Autophagy-deficient mice are more susceptible to engrafted leukemogenesis

Autophagy is primarily considered as an important survival mechanism for both normal cells and cancer cells in response to metabolic stress or chemotherapy; but the role of autophagy in leukemogenesis is not fully understood. The aim of this study is to explore the role of intrinsic autophagy in the leukemogenesis of B-cell acute lymphoblastic leukemia (B-ALL). In this study, conditional knockout mice Atg7^f/f;Ubc-Cre, in which an autophagy-essential gene Atg7 is universally deleted, were used as recipients, B-ALL cell line 697 was used as donor cells to generate leukemia mouse model. Compared to wild-type mice, Atg7 knockout mice were more susceptible to engrafted leukemogenesis, shown by increase in white blood cells, lymphocytes, and platelets, decrease in HSPC number and its colony-forming unit (CFU). The liver and spleen displayed hepatosplenomegaly and inflammatory cell infiltration. Furthermore, second competitive transplantation revealed dysfunction of the HSPC in Atg7-knockout leukemia mice represented by destructive self-renew ability (CFU) and reconstitution ability including decreased B220, Ter 119 cells, and increased Gr-1 cell percentage. In summary, Mice with universal deletion of Atg7 are more inclined to the occurrence of engrafted human leukemia, which is largely attributed to the deterioration of the function of HSPC in autophagy deficient mice.

RET-mediated autophagy suppression as targetable co-dependence in acute myeloid leukemia

Many cases of AML are associated with mutational activation of receptor tyrosine kinases (RTKs) such as FLT3. However, RTK inhibitors have limited clinical efficacy as single agents, indicating that AML is driven by concomitant activation of different signaling molecules. We used a functional genomic approach to identify RET, encoding an RTK, as an essential gene in multiple subtypes of AML, and observed that AML cells show activation of RET signaling via ARTN/GFRA3 and NRTN/GFRA2 ligand/co-receptor complexes. Interrogation of downstream pathways identified mTORC1-mediated suppression of autophagy and subsequent stabilization of leukemogenic drivers such as mutant FLT3 as important RET effectors. Accordingly, genetic or pharmacologic RET inhibition impaired the growth of FLT3-dependent AML cell lines and was accompanied by upregulation of autophagy and FLT3 depletion. RET dependence was also evident in mouse models of AML and primary AML patient samples, and transcriptome and immunohistochemistry analyses identified elevated RET mRNA levels and co-expression of RET and FLT3 proteins in a substantial proportion of AML patients. Our results indicate that RET-mTORC1 signaling promotes AML through autophagy suppression, suggesting that targeting RET or, more broadly, depletion of leukemogenic drivers via autophagy induction provides a therapeutic opportunity in a relevant subset of AML patients.

Antitumor activities of Quercetin and Green Tea in xenografts of human leukemia HL60 cells

Quercetin is one of the most abundant flavonoids, present in fruits and vegetables and has been shown to have multiple properties capable of reducing cell growth in cancer cells. Green tea is a widely consumed beverage, known for a potential source of free radical scavenging and anti-cancer activities. Herein, we investigate the in vivo antitumor efficacy of quercetin and green tea in human leukemia. Human tumors were xenografted into NOD/SCID mice. Quercetin and green tea reduced tumor growth in HL-60 xenografts accompanied by decreased expression of anti-apoptotic proteins, BCL-2, BCL-XL and MCL-1 and increased expression of BAX, a pro-apoptotic protein. Moreover, caspase-3 was activated to a greater extent after quercetin and green tea treatment. Quercetin and green tea also mediated G1 phase cell cycle arrest in HL-60 xenografts. Treatment with quercetin and green tea induced conversion of LC3-I to LC3-II as well as activation of autophagy proteins, suggesting that quercetin and green tea initiate the autophagic progression. We have provided evidence that quercetin and green tea induces signaling at the level of apoptosis, cell cycle and autophagy which converge to antigrowth effects in HL-60 xenograft mice suggesting that these compounds may be a compelling ally in cancer treatment.

PI3K isoform inhibition associated with anti Bcr-Abl drugs shows in vitro increased anti-leukemic activity in Philadelphia chromosome-positive B-acute lymphoblastic leukemia cell lines

B-acute lymphoblastic leukemia (B-ALL) is a malignant disorder characterized by the abnormal proliferation of B-cell progenitors. Philadelphia chromosome-positive (Ph+) B-ALL is a subtype that expresses the Bcr-Abl fusion protein which represents a negative prognostic factor. Constitutive activation of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) network is a common feature of B-ALL, influencing cell growth and survival. In the present study, we aimed to investigate the efficacy of PI3K isoform inhibition in B-ALL cell lines harboring the Bcr-Abl fusion protein.We studied the effects of anti Bcr-Abl drugs Imatinib, Nilotinib and GZD824 associated with PI3K isoform inhibitors. We used a panel of six compounds which specifically target PI3K isoforms including the pan-PI3K inhibitor ZSTK474, p110α BYL719 inhibitor and the dual p110γ/p110δ inhibitor IPI145. The effects of single drugs and of several drug combinations were analyzed to assess cytotoxicity by MTS assays, apoptosis and autophagy by flow cytometry and Western blot, as well as the phosphorylation status of the pathway.ZSTK474, BYL719 and IPI145 administered in combination with imatinib, nilotinib and GZD824 for 48 h, decreased cell viability, induced apoptosis and autophagy in a marked synergistic manner.These findings suggest that selected PI3K isoform inhibitors used in combination with anti Bcr-Abl drugs may be an attractive novel therapeutic intervention in Ph+ B-ALL.

Nucleostemin silencing induces differentiation and potentiates all-trans-retinoic acid effects in human acute promyelocytic leukemia NB4 cells via autophagy

Here, we report that targeting Nucleostemin (NS), a recently discovered stem cells-enriched gene, by a specific small interference RNA (siNS), decreases the rate of proliferation of acute promyelocytic leukemia (APL) NB4 cells and induces differentiation and autophagy. In addition, NS silencing promotes the effects of all-trans-retinoic acid (ATRA)-based differentiation therapy in NB4 cells. Autophagy inhibitors 3-methyladenine and bafilomycin block the effect of NS targeting on differentiation, indicating a new functional link between NS and autophagy as an important regulator of differentiation in NB4 cells. The capability of NS in modulating autophagy and differentiation, alone or in combination with ATRA, may help to broaden the range of treatment options available to treat leukemia.

Autophagy: The spotlight for cellular stress responses

Autophagy is an essential cellular mechanism which plays "housekeeping" role in normal physiological processes including removing of long lived, aggregated and misfolded proteins, clearing damaged organelles, growth regulation and aging. Autophagy is also involved in a variety of biological functions like development, cellular differentiation, defense against pathogens and nutritional starvation. The integration of autophagy into these biological functions and other stress responses is determined by the transcriptional factors that undertake the regulatory mechanism. This review discusses the machinery of autophagy, the molecular web that connects autophagy to various stress responses like inflammation, hypoxia, ER stress, and various other pathologic conditions. Defects in autophagy regulation play a central role in number of diseases, including neurodegenerative diseases, cancer, pathogen infection and metabolic diseases. Similarly, inhibiting autophagy would contribute in the treatment of cancer. However, understanding the biology of autophagy regulation requires pharmacologically active compounds which modulate the autophagy process. Inducers of autophagy are currently receiving considerable attention as autophagy upregulation may be a therapeutic benefit for certain neurodegenerative diseases (via removal of protein aggregates) while the inhibitors are being investigated for the treatment of cancers. Both induction and inhibition of autophagy have been proven to be beneficial in the treatment of cancer. This dual role of autophagy in cancers is now getting uncovered by the advancement in the research findings and development of effective autophagy modulators.

Autophagy, autophagy-associated adaptive immune responses and its role in hematologic malignancies

Autophagy is a tightly regulated catabolic process that leads to the degradation of cytoplasmatic components such as aggregated/misfolded proteins and organelles through the lysosomal machinery. Recent studies suggest that autophagy plays such a role in the context of the anti-tumor immune response, make it an attractive target for cancer immunotherapy. Defective autophagy in hematopoietic stem cells may contribute to the development of hematologic malignancies, including leukemia, myelodysplastic syndrome, and lymphoproliferative disorder. In blood cancer cells, autophagy can either result in chemoresistance or induce autophagic cell death that may act as immunogenic. Based on the successful experimental findings in vitro and in vivo, clinical trials of autophagy inhibitor such as hydroxychloroquine in combination with chemotherapy in patients with blood cancers are currently underway. However, autophagy inactivation might impair autophagy-triggered anticancer immunity, whereas induction of autophagy might become an effective immunotherapy. These aspects are discussed in this review together with a brief introduction to the autophagic molecular machinery and its roles in hematologic malignancies.

Preclinical efficacy of the novel competitive NAMPT inhibitor STF-118804 in pancreatic cancer

NAD salvage is one of the pathways used to generate NAD in mammals. Nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in this pathway, uses nicotinamide (NAM) to generate nicotinamide mononucleotide (NMN). NMN is one of the main precursors of NAD synthesis in cells. Our previous study showed the importance of NAMPT in maintaining NAD levels in pancreatic ductal adenocarcinoma cells (PDAC), and that the NAMPT inhibitor FK866 decreased pancreatic cancer growth. We now tested the effect of STF-118804, a new highly specific NAMPT inhibitor, in models of pancreatic ductal adenocarcinoma. STF-118804 reduced viability and growth of different PDAC lines, as well as the formation of colonies in soft agar. In addition, STF-118804 decreased glucose uptake, lactate excretion, and ATP levels, resulting in metabolic collapse. STF-118804 treatment activated AMPK and inhibited of mTOR pathways in these cells. This effect was significantly potentiated by pharmacological AMPK activation and mTOR inhibition. Exogenous NMN blocked both the activation of the AMPK pathway and the decrease in cell viability. Panc-1 cells expressing GFP-luciferase were orthotopically implanted on mice pancreas to test the in vivo effectiveness of STF-118804. Both STF-118804 and FK866 reduced tumor size after 21 days of treatment. Combinations of STF-118804 with chemotherapeutic agents such as paclitaxel, gemcitabine, and etoposide showed an additive effect in decreasing cell viability and growth. In conclusion, our preclinical study shows that the NAMPT inhibitor STF-118804 reduced the growth of PDAC in vitro and in vivo and had an additive effect in combination with main current chemotherapeutic drugs.

Network analysis reveals crosstalk between autophagy genes and disease genes

Autophagy is a protective and life-sustaining process in which cytoplasmic components are packaged into double-membrane vesicles and targeted to lysosomes for degradation. Accumulating evidence supports that autophagy is associated with several pathological conditions. However, research on the functional cross-links between autophagy and disease genes remains in its early stages. In this study, we constructed a disease-autophagy network (DAN) by integrating known disease genes, known autophagy genes and protein-protein interactions (PPI). Dissecting the topological properties of the DAN suggested that nodes that both autophagy and disease genes (inter-genes), are topologically important in the DAN structure. Next, a core network from the DAN was extracted to analyze the functional links between disease and autophagy genes. The genes in the core network were significantly enriched in multiple disease-related pathways, suggesting that autophagy genes may function in various disease processes. Of 17 disease classes, 11 significantly overlapped with autophagy genes, including cancer diseases, metabolic diseases and hematological diseases, a finding that is supported by the literatures. We also found that autophagy genes have a bridging role in the connections between pairs of disease classes. Altogether, our study provides a better understanding of the molecular mechanisms underlying human diseases and the autophagy process.

Inhibition of autophagy enhances the selective anti-cancer activity of tigecycline to overcome drug resistance in the treatment of chronic myeloid leukemia

Background

Drug resistance and disease progression are still the major obstacles in the treatment of chronic myeloid leukemia (CML). Increasing researches have demonstrated that autophagy becomes activated when cancer cells are subjected to chemotherapy, which is involved in the development of drug resistance. Therefore, combining chemotherapy with inhibition of autophagy serves as a new strategy in cancer treatment. Tigecycline is an antibiotic that has received attention as an anti-cancer agent due to its inhibitory effect on mitochondrial translation. However, whether combination of tigecycline with inhibition of autophagy could overcome drug resistance in CML remains unclear.

Methods

We analyzed the biological and metabolic effect of tigecycline on CML primary cells and cell lines to investigate whether tigecycline could regulate autophagy in CML cells and whether coupling autophagy inhibition with treatment using tigecycline could affect the viabilities of drug-sensitive and drug-resistant CML cells.

Results

Tigecycline inhibited the viabilities of CML primary cells and cell lines, including those that were drug-resistant. This occurred via the inhibition of mitochondrial biogenesis and the perturbation of cell metabolism, which resulted in apoptosis. Moreover, tigecycline induced autophagy by downregulating the PI3K-AKT-mTOR pathway. Additionally, combining tigecycline use with autophagy inhibition further promoted the anti-leukemic activity of tigecycline. We also observed that the anti-leukemic effect of tigecycline is selective. This is because the drug targeted leukemic cells but not normal cells, which is because of the differences in the mitochondrial biogenesis and metabolic characterization between the two cell types.

Conclusions

Combining tigecycline use with autophagy inhibition is a promising approach for overcoming drug resistance in CML treatment.

The optimal dose of arsenic trioxide induced opposite efficacy in autophagy between K562 cells and their initiating cells to eradicate human myelogenous leukemia

ETHNOPHARMACOLOGICAL RELEVANCE

Arsenic trioxide (As2O3), a main component of arsenolite which is a common traditional Chinese medicine (TCM) wildly used as a therapeutic agent for more than 2400 years in china, has been accepted as a standard treatment for the patients with acute promyelocytic leukemia (APL) based on the principle in TCM of "using a poison to fight against other poisons or malignancy illnesses". However, it remains unknown that which mechanism is actually responsible for the therapeutic effects against these blood malignancies.

AIM OF THE STUDY

The purpose of this study was to explore the actual mechanism that ATO exerts its effects in K562 cells and their initiating cells (K562s).

MATERIALS AND METHODS

K562s cells were separated and enriched for CD34+/CD38- cells using magnetic microbeads. Cell proliferation was determined by incorporation of BrdU. Cell apoptosis was evaluated by Annexin-V binding and PI uptake. Autophagy was estimated by acridine orange and immunofluorescence staining of LC3-B and p62. MC colonic formation was used to examine cell self-renew. ROS generation inside living cells was measured by DCFH-DA. Cell differentiation was assessed by the benzidine staining. The SA-β-gal assay was used to detect cell senescence. Protein expression was examined by western blotting and immunohistochemical staining.

RESULTS

K562s cells were stronger in self-renew and resistance to ATO cytotoxicity and starvation-induced apoptosis than K562 cells. Unexpectedly, we found that ATO at a dose of 0.5μM which had no effect on cell proliferation resulted in maximum suppression on self-renew in both cells and maximum starvation-induced apoptosis in K562s cells but minimum starvation-induced apoptosis in K562 cells. Next, we found that ATO no more than 0.5μM selectively induced K562s cell differentiation indicated by benzidine staining, γ-globin and CD235a expression. More importantly, we found that ATO no more than 0.5μM led to opposite efficacy in autophagy between K562 and K562s cells, and the opposite autophagy could induced late-phase senescence in both cells. Finally, we used the optimal dose of ATO to eradicate leukemia cells and obtained a satisfied therapeutic outcomes in vivo.

CONCLUSIONS

Our results suggest that the used dose of ATO may determine the fate of cell differentiation senescence or malignant transformation, and the optimal dose of ATO induced opposite efficacy in autophagy between K562 cells and their initiating cells and ultimately leads both cells to late-phase senescence.

Matrine induces Akt/mTOR signalling inhibition-mediated autophagy and apoptosis in acute myeloid leukaemia cells

Pharmacological modulation of autophagy has been referred to as a promising therapeutic strategy for cancer. Matrine, a main alkaloid extracted from Sophora flavescens Ait, has antitumour activity against acute myelocytic leukaemia (AML). Whether autophagy is involved in antileukaemia activity of matrine remains unobvious. In this study, we demonstrated that matrine inhibited cell viability and colony formation via inducing apoptosis and autophagy in AML cell lines HL‐60, THP‐1 and C1498 as well as primary AML cells. Matrine promoted caspase‐3 and PARP cleavage dose‐dependently. Matrine up‐regulated the level of LC3‐II and down‐regulated the level of SQSTM1/p62 in a dose‐dependent way, indicating that autophagy should be implicated in anti‐AML effect of matrine. Furthermore, the autophagy inhibitor bafilomycin A1 relieved the cytotoxicity of matrine by blocking the autophagic flux, while the autophagy promoter rapamycin enhanced the cytotoxicity of matrine. Additionally, matrine inhibited the phosphorylation of Akt, mTOR and their downstream substrates p70S6K and 4EBP1, which led to the occurrence of autophagy. In vivo study demonstrated that autophagy was involved in antileukaemia effect of matrine in C57BL/6 mice bearing murine AML cell line C1498, and the survival curves showed that mice did benefit from treatment with matrine. Collectively, our findings indicate that matrine exerts antitumour effect through apoptosis and autophagy, and the latter one might be a potential therapeutic strategy for AML.

Photodynamic N-TiO2 Nanoparticle Treatment Induces Controlled ROS-mediated Autophagy and Terminal Differentiation of Leukemia Cells

In this study, we used nitrogen-doped titanium dioxide (N-TiO₂) NPs in conjugation with visible light, and show that both reactive oxygen species (ROS) and autophagy are induced by this novel NP-based photodynamic therapy (PDT) system. While well-dispersed N-TiO₂ NPs (≤100 μg/ml) were inert, their photo-activation with visible light led to ROS-mediated autophagy in leukemia K562 cells and normal peripheral lymphocytes, and this increased in parallel with increasing NP concentrations and light doses. At a constant light energy (12 J/cm²), increasing N-TiO₂ NP concentrations increased ROS levels to trigger autophagy-dependent megakaryocytic terminal differentiation in K562 cells. By contrast, an ROS challenge induced by high N-TiO₂ NP concentrations led to autophagy-associated apoptotic cell death. Using chemical autophagy inhibitors (3-methyladenine and Bafilomycin A1), we confirmed that autophagy is required for both terminal differentiation and apoptosis induced by photo-activated N-TiO₂. Pre-incubation of leukemic cells with ROS scavengers muted the effect of N-TiO₂ NP-based PDT on cell fate, highlighting the upstream role of ROS in our system. In summary, PDT using N-TiO₂ NPs provides an effective method of priming autophagy by ROS induction. The capability of photo-activated N-TiO₂ NPs in obtaining desirable cellular outcomes represents a novel therapeutic strategy of cancer cells.

Proteolytic systems and AMP-activated protein kinase are critical targets of acute myeloid leukemia therapeutic approaches

The therapeutic strategies against acute myeloid leukemia (AML) have hardly been modified over four decades. Although resulting in a favorable outcome in young patients, older individuals, the most affected population, do not respond adequately to therapy. Intriguingly, the mechanisms responsible for AML cells chemoresistance/susceptibility are still elusive. Mounting evidence has shed light on the relevance of proteolytic systems (autophagy and ubiquitin-proteasome system, UPS), as well as the AMPK pathway, in AML biology and treatment, but their exact role is still controversial. Herein, two AML cell lines (HL-60 and KG-1) were exposed to conventional chemotherapeutic agents (cytarabine and/or doxorubicin) to assess the relevance of autophagy and UPS on AML cells’ response to antileukemia drugs. Our results clearly showed that the antileukemia agents target both proteolytic systems and the AMPK pathway. Doxorubicin enhanced UPS activity while drugs’ combination blocked autophagy specifically on HL-60 cells. In contrast, KG-1 cells responded in a more subtle manner to the drugs tested consistent with the higher UPS activity of these cells. In addition, the data demonstrates that autophagy may play a protective role depending on AML subtype. Specific modulators of autophagy and UPS are, therefore, promising targets for combining with standard therapeutic interventions in some AML subtypes.

Basal autophagy is pivotal for Hodgkin and Reed-Sternberg cells' survival and growth revealing a new strategy for Hodgkin lymphoma treatment

As current classical Hodgkin lymphoma (cHL) treatment strategies have pronounced side-effects, specific inhibition of signaling pathways may offer novel strategies in cHL therapy. Basal autophagy, a regulated catabolic pathway to degrade cell's own components, is in cancer linked with both, tumor suppression or promotion. The finding that basal autophagy enhances tumor cell survival would thus lead to immediately testable strategies for novel therapies. Thus, we studied its contribution in cHL.We found constitutive activation of autophagy in cHL cell lines and primary tissue. The expression of key autophagy-relevant proteins (e.g. Beclin-1, ULK1) and LC3 processing was increased in cHL cells, even in lymphoma cases. Consistently, cHL cells exhibited elevated numbers of autophagic vacuoles and intact autophagic flux. Autophagy inhibition with chloroquine or inactivation of ATG5 induced apoptosis and reduced proliferation of cHL cells. Chloroquine-mediated inhibition of basal autophagy significantly impaired HL growth in-vivo in NOD SCID γc-/- (NSG) mice. We found that basal autophagy plays a pivotal role in sustaining mitochondrial function.We conclude that cHL cells require basal autophagy for growth, survival and sustained metabolism making them sensitive to autophagy inhibition. This suggests basal autophagy as useful target for new strategies in cHL treatment.

Relationship between triterpenoid anticancer drug resistance, autophagy, and caspase-1 in adult T-cell leukemia

We previously reported that the inflammasome inhibitor cucurbitacin D (CuD) induces apoptosis in human leukemia cell lines. Here, we investigated the effects of CuD and a B-cell lymphoma extra-large (Bcl-xL) inhibitor on autophagy in peripheral blood lymphocytes (PBL) isolated from adult T-cell leukemia (ATL) patients. CuD induced PBL cell death in patients but not in healthy donors. This effect was not significantly inhibited by treatment with rapamycin or 3-methyladenine (3-MA). The Bcl-xL inhibitor Z36 induced death in primary cells from ATL patients including that induced by CuD treatment, effects that were partly inhibited by 3-MA. Similarly, cell death induced by the steroid prednisolone was enhanced in the presence of Z36. A western blot analysis revealed that Z36 also promoted CuD-induced poly(ADP ribose) polymerase cleavage. Interestingly, the effects of CuD and Z36 were attenuated in primary ATL patient cells obtained upon recurrence after umbilical cord blood transplantation, as compared to those obtained before chemotherapy. Furthermore, cells from this patient expressed a high level of caspase-1, and treatment with caspase-1 inhibitor-enhanced CuD-induced cell death. Taken together, these results suggest that rescue from resistance to steroid drugs can enhance chemotherapy, and that caspase-1 is a good marker for drug resistance in ATL patients.

An Immunohistochemical Survey of SNARE Proteins Shows Distinct Patterns of Expression in Hematolymphoid Neoplasia

OBJECTIVES

Five proteins from the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) complex family were studied in normal hematopoietic cells in bone marrow; normal lymphocytes at different stages of maturation and differentiation in bone marrow, thymus, tonsil, and lymph node; malignant lymphomas; and leukemias.

METHODS

Sixty-eight reactive and 380 hematopoietic and lymphoid neoplasms were immunohistochemically stained for syntaxin 7 (STX7), vesicle-associated membrane proteins (VAMP2, VAMP7, VAMP8), and synaptosomal-associated protein 23 (SNAP23).

RESULTS

STX7 has potential for being a useful marker for distinguishing between normal B precursors (hematogones) vs B lymphoblasts, as well as between the "popcorn" cells of nodular lymphocyte-predominant Hodgkin lymphoma vs the Reed-Sternberg cells of classic Hodgkin lymphoma or the B cells of T-cell, histiocyte-rich B-cell lymphoma. VAMP2 is uniquely expressed by both reactive and malignant plasma cells, in contrast to B-cell non-Hodgkin lymphoma. There is differential expression of SNARE proteins in normal and neoplastic lymphoid tissue depending on lymphocyte maturation stage.

CONCLUSIONS

Differential SNARE protein expression in the lymphoid system may have potential use in diagnosis and may offer clues to lymphoma biology. VAMP2 is a promising new plasma cell marker.

Role of autophagy in megakaryocyte differentiation and platelet formation

Autophagy is a conserved biological process for digestion and recycling of cytoplasmic constituents in eukaryotic cells. Autophagy may trigger cell death or promote cell survival following various forms of stress. The emerging roles of autophagy in megakaryopoiesis, thrombopoiesis, and platelet function have been uncovered using not only in vitro and in vivo genetic models, but also in clinical observations of autophagic structure in patients with thrombocytopenic disorders. Inhibition of autophagy in early stage of megakaryocyte differentiation appears to impede megakaryocyte maturation, reduce platelet formation, and affect platelet function, whereas autophagic deficiency in mature megakaryocytes gives rise to abnormal platelet activation and function without changing platelet size and number. On the other hand, induction of autophagy by rapamycin in megakaryocytes exhibited substantial therapeutic benefits in patients with immune thrombocytopenic purpura (ITP). This mini-review is to highlight recent progresses in understanding the regulation of autophagy in megakaryopoiesis, thrombopoiesis and platelet function to bridge the gap between autophagy and megakaryocyte/platelet pathophysiology.

Autophagy is associated with cucurbitacin D-induced apoptosis in human T cell leukemia cells

We previously reported that the inflammasome inhibitor cucurbitacin D (CuD) induces apoptosis in human leukemia cell lines. In the present study, we investigated the effects of co-treatment with an additional Bcl-xL inhibitor, Z36. Treatment with Z36 induced cell death in leukemia cell lines, with MT-4 cells exhibiting the lowest sensitivity to Z36. Co-treatment of cells with Z36 and CuD resulted in a greater degree of cell death for Hut78 and Jurkat cells than treatment with CuD alone. In contrast, co-treatment of MT-4 cells with Z36 and CuD had a suppressive effect on cell death. The autophagy inhibitor 3-methyladenine (3-MA) suppressed the growth of leukemia cell lines HuT78, Jurkat, MT-1, and MT-4. CuD-induced cell death was enhanced by 3-MA in Jurkat cells, but inhibited in MT-4 cells. Western blotting results revealed cleavage of poly(ADP ribose) polymerase (PARP), supporting CuD-induced cell death; 3-MA enhanced CuD-Z36-induced PARP cleavage. Taken together, our results indicate that autophagy negatively regulates chemical-induced cell death of leukemia cells, and that controlling autophagy could be beneficial in the development of more effective chemotherapies against leukemia.

Targeting Hedgehog signaling pathway and autophagy overcomes drug resistance of BCR-ABL-positive chronic myeloid leukemia

The frontline tyrosine kinase inhibitor (TKI) imatinib has revolutionized the treatment of patients with chronic myeloid leukemia (CML). However, drug resistance is the major clinical challenge in the treatment of CML. The Hedgehog (Hh) signaling pathway and autophagy are both related to tumorigenesis, cancer therapy, and drug resistance. This study was conducted to explore whether the Hh pathway could regulate autophagy in CML cells and whether simultaneously regulating the Hh pathway and autophagy could induce cell death of drug-sensitive or -resistant BCR-ABL(+) CML cells. Our results indicated that pharmacological or genetic inhibition of Hh pathway could markedly induce autophagy in BCR-ABL(+) CML cells. Autophagic inhibitors or ATG5 and ATG7 silencing could significantly enhance CML cell death induced by Hh pathway suppression. Based on the above findings, our study demonstrated that simultaneously inhibiting the Hh pathway and autophagy could markedly reduce cell viability and induce apoptosis of imatinib-sensitive or -resistant BCR-ABL(+) cells. Moreover, this combination had little cytotoxicity in human peripheral blood mononuclear cells (PBMCs). Furthermore, this combined strategy was related to PARP cleavage, CASP3 and CASP9 cleavage, and inhibition of the BCR-ABL oncoprotein. In conclusion, this study indicated that simultaneously inhibiting the Hh pathway and autophagy could potently kill imatinib-sensitive or -resistant BCR-ABL(+) cells, providing a novel concept that simultaneously inhibiting the Hh pathway and autophagy might be a potent new strategy to overcome CML drug resistance.

SLAMF1 regulation of chemotaxis and autophagy determines CLL patient response

Chronic lymphocytic leukemia (CLL) is a variable disease; therefore, markers to identify aggressive forms are essential for patient management. Here, we have shown that expression of the costimulatory molecule and microbial sensor SLAMF1 (also known as CD150) is lost in a subset of patients with an aggressive CLL that associates with a shorter time to first treatment and reduced overall survival. SLAMF1 silencing in CLL-like Mec-1 cells, which constitutively express SLAMF1, modulated pathways related to cell migration, cytoskeletal organization, and intracellular vesicle formation and recirculation. SLAMF1 deficiency associated with increased expression of CXCR4, CD38, and CD44, thereby positively affecting chemotactic responses to CXCL12. SLAMF1 ligation with an agonistic monoclonal antibody increased ROS accumulation and induced phosphorylation of p38, JNK1/2, and BCL2, thereby promoting the autophagic flux. Beclin1 dissociated from BCL2 in response to SLAMF1 ligation, resulting in formation of the autophagy macrocomplex, which contains SLAMF1, beclin1, and the enzyme VPS34. Accordingly, SLAMF1-silenced cells or SLAMF1(lo) primary CLL cells were resistant to autophagy-activating therapeutic agents, such as fludarabine and the BCL2 homology domain 3 mimetic ABT-737. Together, these results indicate that loss of SLAMF1 expression in CLL modulates genetic pathways that regulate chemotaxis and autophagy and that potentially affect drug responses, and suggest that these effects underlie unfavorable clinical outcome experienced by SLAMF1(lo) patients.

EIF2A-dependent translational arrest protects leukemia cells from the energetic stress induced by NAMPT inhibition

Background

Nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in NAD⁺ biosynthesis from nicotinamide, is one of the major factors regulating cancer cells metabolism and is considered a promising target for treating cancer. The prototypical NAMPT inhibitor FK866 effectively lowers NAD⁺ levels in cancer cells, reducing the activity of NAD⁺-dependent enzymes, lowering intracellular ATP, and promoting cell death.

Results

We show that FK866 induces a translational arrest in leukemia cells through inhibition of MTOR/4EBP1 signaling and of the initiation factors EIF4E and EIF2A. Specifically, treatment with FK866 is shown to induce 5′AMP-activated protein kinase (AMPK) activation, which, together with EIF2A phosphorylation, is responsible for the inhibition of protein synthesis. Notably, such an effect was also observed in patients’ derived primary leukemia cells including T-cell Acute Lymphoblastic Leukemia. Jurkat cells in which AMPK or LKB1 expression was silenced or in which a non-phosphorylatable EIF2A mutant was ectopically expressed showed enhanced sensitivity to the NAMPT inhibitor, confirming a key role for the LKB1-AMPK-EIF2A axis in cell fate determination in response to energetic stress via NAD⁺ depletion.

Conclusions

We identified EIF2A phosphorylation as a novel early molecular event occurring in response to NAMPT inhibition and mediating protein synthesis arrest. In addition, our data suggest that tumors exhibiting an impaired LBK1- AMPK- EIF2A response may be especially susceptible to NAMPT inhibitors and thus become an elective indication for this type of agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1845-1) contains supplementary material, which is available to authorized users.

Induction of autophagy is a key component of all-trans-retinoic acid-induced differentiation in leukemia cells and a potential target for pharmacologic modulation

Acute myeloid leukemia (AML) is characterized by the accumulation of immature blood cell precursors in the bone marrow. Pharmacologically overcoming the differentiation block in this condition is an attractive therapeutic avenue, which has achieved success only in a subtype of AML, acute promyelocytic leukemia (APL). Attempts to emulate this success in other AML subtypes have thus far been unsuccessful. Autophagy is a conserved protein degradation pathway with important roles in mammalian cell differentiation, particularly within the hematopoietic system. In the study described here, we investigated the functional importance of autophagy in APL cell differentiation. We found that autophagy is increased during all-trans-retinoic acid (ATRA)-induced granulocytic differentiation of the APL cell line NB4 and that this is associated with increased expression of LC3II and GATE-16 proteins involved in autophagosome formation. Autophagy inhibition, using either drugs (chloroquine/3-methyladenine) or short-hairpin RNA targeting the essential autophagy gene ATG7, attenuates myeloid differentiation. Importantly, we found that enhancing autophagy promotes ATRA-induced granulocytic differentiation of an ATRA-resistant derivative of the non-APL AML HL60 cell line (HL60-Diff-R). These data support the development of strategies to stimulate autophagy as a novel approach to promote differentiation in AML.

Proteasome inhibitors induce FLT3-ITD degradation through autophagy in AML cells

Internal tandem duplication of the Fms-like tyrosine kinase-3 receptor (FLT3) internal tandem duplication (ITD) is found in 30% of acute myeloid leukemia (AML) and is associated with a poor outcome. In addition to tyrosine kinase inhibitors, therapeutic strategies that modulate the expression of FLT3-ITD are also promising. We show that AML samples bearing FLT3-ITD mutations are more sensitive to proteasome inhibitors than wild-type samples and this sensitivity is strongly correlated with a higher FLT3-ITD allelic burden. Using pharmacologic inhibitors of autophagy, specific downregulation of key autophagy proteins including Vps34, autophagy gene (Atg)5, Atg12, Atg13, biochemical, and microscopy studies, we demonstrated that proteasome inhibitors induced cytotoxic autophagy in AML cells. FLT3-ITD molecules were detectable within autophagosomes after bortezomib treatment indicating that autophagy induction was responsible for the early degradation of FLT3-ITD, which preceded the inhibition of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK), PI3K/AKT, and STAT5 pathways, and subsequent activation of cell death. Moreover, proteasome inhibitors overcome resistance to quizartinib induced by mutations in the kinase domain of FLT3, suggesting that these compounds may prevent the emergence of mutant clones arising from tyrosine kinase inhibitor treatments. In xenograft mice models, bortezomib stimulated the conversion of LC3-I to LC3-II, indicating induction of autophagy in vivo, downregulated FLT3-ITD protein expression and improved overall survival. Therefore, selecting patients according to FLT3-ITD mutations could be a new way to detect a significant clinical activity of proteasome inhibitors in AML patients.

[The impact of autophagy on proliferation of HEL cells and hematopoietic cells of polycythemia vera patients with JAK2 V617F mutation]

OBJECTIVE

To detect the activity of autophagy and explore the impact on survival and proliferation of HEL cells and hematopoietic cells of polycythemia vera （PV） patients with JAK2 V617F mutation.

METHODS

Flow cytometry, AO staining and Western blot methods were used to detect the autophagy activity and the expression of LC3-Ⅱ protein of JAK2 V617F+ HEL cells and hematopoietic cells of 12 newly diagnosed PV patients with JAK2 V617F mutation. HEL cells and bone marrow cells of 3 PV patients were treated with rapamycin or 3-MA to induce and inhibit autophagy, respectively. CellTiter Glo(R) method was used to detect the proliferation activity of cells.

RESULTS

There was higher level of mean LC3-Ⅱ fluorescence intensity in HEL cells (159 389 ± 29 001) than that in K562 cells (96 047 ± 24 134) (P=0.044). The formation of autophagosome in HEL cells is more than that in K562 cells detected by microscope. What's more, the level of mean LC3-Ⅱ fluorescence intensity in 12 PV patients' myeloid cells (92 842 ± 4 250) was higher than that of 15 healthy volunteers (86 633 ± 2 504) (P=0.001). The expression of LC3-Ⅱ protein was higher in PV patients' peripheral blood cells than that in healthy volunteers detected by Western blot. After treated with rapamycin 12, 24, 48 h, the activity of autophagy in HEL cells and bone marrow cells of 3 PV patients were increased and the proliferation activity was higher than the control group, the proliferation activity at 48 h were (101 413 ± 3 720), (18 744 ± 1 015), respectively. However, after treated with 3-MA 12, 24, 48 h, the activity of autophagy was decreased and the proliferation activity was lower than the control group, the proliferation activity at 48 h were (5 732 ± 166), (5 371 ± 56), respectively.

CONCLUSION

There is high basical activity of autophagy in JAK2 V617F+ HEL cells and hematopoietic cells of PV patients with JAK2 V617F mutation. Up-regulated autophagy promotes proliferation of JAK2 V617F⁺ HEL cells and bone marrow cells of PV patients with JAK2 V617F mutation. Decreased autophagy inhibits proliferation of JAK2 V617F+ HEL cells and bone marrow cells of PV patients with JAK2 V617F mutation.

HMGB1 translocation is involved in the transformation of autophagy complexes and promotes chemoresistance in leukaemia

Acute lymphoblastic leukaemia (ALL) is a common paediatric cancer and is among the most curable cancers. However, the acquisition of drug resistance is a significant obstacle to the achievement of favourable outcomes, and autophagy is regarded as a mechanism that underlies chemoresistance. In this study, RT-qPCR was used to measure the expression of HMGB1 and Beclin1 in bone marrow mononuclear cells. A CCK-8 test was conducted to assess cell viability. Western blot, immunofluorescence and transmission electron microscopic analyses were performed to evaluate the autophagy levels. Immunoprecipitation analysis was performed to detect protein-protein interactions in the autophagy complexes. We found that HMGB1 expression correlated with the clinical status of ALL. In vitro, anticancer agent-induced cytotoxic effects were associated with autophagy-related drug resistance, and these effects were ameliorated by FIP200 depletion or the application of autophagy inhibitors. Moreover, the Ulk1‑Atg13-FIP200 complex, which promotes HMGB1 trafficking, acted upstream of the HMGB1-Beclin1 and PI3KC3-Beclin1 complexes and played a critical role in autophagy. Targeting the transformation of autophagic complexes or HMGB1 translocation may suppress autophagy and consequently overcome chemoresistance in leukaemia.

Autophagy collaborates with ubiquitination to downregulate oncoprotein E2A/Pbx1 in B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (B-ALL) accounts for the most cancer incidences in children. We present here that autophagy is downregulated in pediatric B-ALL, suggesting a possible link between autophagy failure and pediatric B-ALL leukemogenesis. With a pediatric t(1;19) B-ALL xenograft mouse model, we show here that activation of autophagy by preventive administration of rapamycin improved the survival of leukemia animals by partial restoration of hematopoietic stem/progenitor cells, whereas treatment of the animals with rapamycin caused leukemia bone marrow cell-cycle arrest. Activation of autophagy in vitro or in vivo by rapamycin or starvation downregulated oncogenic fusion protein E2A/Pbx1. Furthermore, E2A/Pbx1 was found to be colocalized with autophagy marker LC3 in autolysosomes and with ubiquitin in response to autophagy stimuli, whereas autophagy or ubiquitination inhibitor blocked these colocalizations. Together, our data suggest a collaborative action between autophagy and ubiquitination in the degradation of E2A/Pbx1, thereby revealing a novel strategy for targeted preventive or treatment therapy on the pediatric ALL.

Bafilomycin A1 targets both autophagy and apoptosis pathways in pediatric B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia is the most common type of pediatric leukemia. Despite improved remission rates, current treatment regimens for pediatric B-cell acute lymphoblastic leukemia are often associated with adverse effects and central nervous system relapse, necessitating more effective and safer agents. Bafilomycin A1 is an inhibitor of vacuolar H(+)-ATPase that is frequently used at high concentration to block late-phase autophagy. Here, we show that bafilomycin A1 at a low concentration (1 nM) effectively and specifically inhibited and killed pediatric B-cell acute lymphoblastic leukemia cells. It targeted both early and late stages of the autophagy pathway by activating mammalian target of rapamycin signaling and by disassociating the Beclin 1-Vps34 complex, as well as by inhibiting the formation of autolysosomes, all of which attenuated functional autophagy. Bafilomycin A1 also targeted mitochondria and induced caspase-independent apoptosis by inducing the translocation of apoptosis-inducing factor from mitochondria to the nucleus. Moreover, bafilomycin A1 induced the binding of Beclin 1 to Bcl-2, which further inhibited autophagy and promoted apoptotic cell death. In primary cells from pediatric patients with B-cell acute lymphoblastic leukemia and a xenograft model, bafilomycin A1 specifically targeted leukemia cells while sparing normal cells. An in vivo mouse toxicity assay confirmed that bafilomycin A1 is safe. Our data thus suggest that bafilomycin A1 is a promising candidate drug for the treatment of pediatric B-cell acute lymphoblastic leukemia.

IGF-1 alleviates NMDA-induced excitotoxicity in cultured hippocampal neurons against autophagy via the NR2B/PI3K-AKT-mTOR pathway

Insulin-like growth factor-1 (IGF-1) is a brain-specific multifunctional protein involved in neuronal polarity and axonal guidance. Mature IGF-1 triggers three enzymes, mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K), and phosphoinositide phospholipase C-γ (PLC-γ), which are its predominant downstream regulators. The PI3K-AKT signaling pathway is upstream of the mammalian target of rapamycin (mTOR), which is of great importance in the induction of autophagy. However, whether the neuroprotective effect of IGF-1 against excitotoxicity is mediated by autophagy through the PI3K/AKT/mTOR pathway remains to be elucidated. The induction of autophagy following NMDA treatment was determined by microtubule-associated protein light chain 3 (LC3) conversion and the result of this autophagy was assessed by monitoring the cleavage of caspase 3 in cultured hippocampal neurons. Cell viability was determined using MTT and LDH assay, and PI-staining was used to estimate the fate of autophagy and the protective effect of IGF-1. In addition, IGF-1 was found to decrease autophagy induced by NMDA using transmission electron microscopy and MDC staining. The protective effect of IGF-1 against autophagy was accompanied with up-regulation of phospho-AKT (p-AKT) and phospho-mTOR (p-mTOR), which was blocked by the inhibitor of PI3K. At the same time, the activation of NR2B resulting in the down-regulation of p-AKT and p-mTOR was blocked by IGF-1. Together, these data suggest that NMDA induces the autophagy, followed by apoptosis in cultured hippocampal neurons, and that IGF-1 can block this effect via inhibition of NR2B receptors and activation of the PI3K-AKT-mTOR pathway.