Autophagy, a key mechanism of oncogenesis and resistance in leukemia

Long noncoding RNA DANCR confers cytarabine resistance in acute myeloid leukemia by activating autophagy via the miR-874-3P/ATG16L1 axis

Autophagy is an important mechanism involved in the regulation of acute myeloid leukemia (AML) chemoresistance. The long noncoding RNA (lncRNA) differentiation antagonizing non‐protein coding RNA (DANCR) exhibits oncogenic activity in several types of human cancers, including AML, but it remains unclear whether it regulates autophagy and chemoresistance in AML. We report here that cytarabine (Ara‐C) treatment elevates DANCR expression in human AML cells. In addition, DANCR overexpression confers and its knockdown diminishes Ara‐C resistance in human AML cells, suggesting that DANCR positively regulates AML chemoresistance to Ara‐C. Moreover, DANCR promotes autophagy in Ara‐C‐treated human AML cells and acts as a sponge to decrease miR‐20a‐5p expression, thereby upregulating the expression of ATG16L1, a critical component of the autophagy machinery. Importantly, ATG16L1 silencing abrogates DANCR‐promoted autophagy and markedly restores DANCR‐conferred Ara‐C resistance, suggesting that DANCR promotes MIR‐874‐3P/ATG16L1 axis‐regulated autophagy to confer Ara‐C resistance in human AML cells. Together, this study identifies DANCR as a positive regulator of Ara‐C resistance in human AML cells, suggesting this lncRNA as a potential target for overcoming Ara‐C resistance in AML chemotherapy.

expression predicts the prognosis of patients with hepatocellular carcinoma after transcatheter arterial chemoembolization

Transcatheter arterial chemoembolization (TACE) induces ischemia-hypoxia and local chemotherapy-induced cytotoxicity which destroys cancerous cells. However, some patients do not respond to TACE. The causes for such a lack of response remain unclear. Recent studies have revealed that self-regulation of apoptosis-stimulating p53 protein 2 (ASPP2) may play an important role in promoting cell survival under hypoxic conditions as well as chemotherapy resistance via autophagy in various types of cancer. We measured the expression of ASPP2, autophagy-related proteins and apoptotic proteins by western blot assays. Multivariate logistic regression analysis was used to identify the independent risk factor. The present study found that ASPP2 expression was negatively correlated with that of BECN-1 (Beclin-1) in hepatocellular carcinoma (HCC) tissues. The expression of ASPP-1 was lower while that of Beclin-1 was higher in patients who underwent recurrence of HCC following TACE, than in those who do not undergo such a relapse. ASPP2 expression was also lower in cancerous tissues subjected to TACE, compared with that of directly resected cancerous tissue. The expression of LC3-II was also higher in patients with post-operative recurrence of HCC than in those without relapse. In vitro experiments showed that administration of an autophagy inhibitor, together with hypoxia activation and 5-FU treatment, promoted apoptosis in HepG2 liver cancer cells and primary HCC cells. Multivariate logistic regression analysis revealed that ASPP2 expression in cancer tissue following TACE is an independent risk factor for HCC recurrence as well as overall survival. Higher levels of ASPP2 expression were notably associated with higher objective responses evaluated via mRECIST. Thus, patients with resectable HCC showing high levels of ASPP2 expression may benefit from neoadjuvant TACE prior to resection. Our study provided a novel biomarker for HCC prognosis following TACE, based on cell survival mechanisms related to autophagy.

Targeting Lactate Metabolism by Inhibiting MCT1 or MCT4 Impairs Leukemic Cell Proliferation, Induces Two Different Related Death-Pathways and Increases Chemotherapeutic Sensitivity of Acute Myeloid Leukemia Cells

Metabolism in acute myeloid leukemia (AML) cells is dependent primarily on oxidative phosphorylation. However, in order to sustain their high proliferation rate and metabolic demand, leukemic blasts use a number of metabolic strategies, including glycolytic metabolism. Understanding whether monocarboxylate transporters MCT1 and MCT4, which remove the excess of lactate produced by cancer cells, represent new hematological targets, and whether their respective inhibitors, AR-C155858 and syrosingopine, can be useful in leukemia therapy, may reveal a novel treatment strategy for patients with AML. We analyzed MCT1 and MCT4 expression and function in hematopoietic progenitor cells from healthy cord blood, in several leukemic cell lines and in primary leukemic blasts from patients with AML, and investigated the effects of AR-C155858 and syrosingopine, used alone or in combination with arabinosylcytosine, on leukemic cell proliferation. We found an inverse correlation between MCT1 and MCT4 expression levels in leukemic cells, and showed that MCT4 overexpression is associated with poor prognosis in AML patients. We also found that AR-C155858 and syrosingopine inhibit leukemic cell proliferation by activating two different cell-death related pathways, i.e., necrosis for AR-C155858 treatment and autophagy for syrosingopine, and showed that AR-C155858 and syrosingopine exert an anti-proliferative effect, additive to chemotherapy, by enhancing leukemic cells sensitivity to chemotherapeutic agents. Altogether, our study shows that inhibition of MCT1 or MCT4 impairs leukemic cell proliferation, suggesting that targeting lactate metabolism may be a new therapeutic strategy for AML, and points to MCT4 as a potential therapeutic target in AML patients and to syrosingopine as a new anti-proliferative drug and inducer of autophagy to be used in combination with conventional chemotherapeutic agents in AML treatment.

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.

Mitochondrial rewiring through mitophagy and mitochondrial biogenesis in cancer stem cells: A potential target for anti-CSC cancer therapy

Cancer stem cells (CSCs) are distinct subpopulations of cancer cells with stem cell-like abilities and are more resilient to chemotherapy, causing tumor relapse. Mitophagy, a selective form of autophagy, removes damaged unwanted mitochondria from cells through a lysosome-based degradation pathway to maintain cellular homeostasis. CSCs use mitophagy as a chief survival response mechanism for their growth, propagation, and tumorigenic ability. Mitochondrial biogenesis is a crucial cellular event replacing damaged mitochondria through the coordinated regulation of several transcription factors to achieve the bioenergetic demands of the cell. Because of the high mitochondrial content in CSCs, mitochondrial biogenesis is an interesting target to address the resistance mechanisms of anti-CSC therapy. However, to what extent both mitophagy and mitochondrial biogenesis are vital in promoting stemness, metabolic reprogramming, and drug resistance in CSCs has yet to be established. Therefore, in this review, we focus on understanding the interesting aspects of mitochondrial rewiring that involve mitophagy and mitochondrial biogenesis in CSCs. We also discuss their coordinated regulation in the elimination of CSCs, with respect to stemness and differentiation of the CSC phenotype, and the different aspects of tumorigenesis such as cancer initiation, progression, resistance, and tumor relapse. Finally, we address several other unanswered questions relating to targeted anti-CSC cancer therapy, which improves patient survival.

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.

Isoflurane activates AMP-activated protein kinase to inhibit proliferation, and promote apoptosis and autophagy in cervical carcinoma both in vitro and in vivo

OBJECTIVE

Isoflurane is an extensively used inhalational anesthesia, and its carcinogenic or anti-cancerous effect has been identified recently. However, the specific role of isoflurane in cervical cancer remains unclear.

AIM

This study aimed to investigate the function of isoflurane in cervical cancer as well as the underlying mechanism.

METHODS

After isoflurane treatment, HeLa cell viability, percentage of apoptotic cells, expression of active caspase-3/9 were examined by CCK-8 assay, Annexin V-FITC/PI double staining, and Western blot analysis, respectively. ROS generation, ratio of NAD⁺/NADH, and ATP level after isoflurane stimulation were determined using commercial assay kits. Afterwards, activation of AMPK and autophagy was assessed through Western blot analysis and immunofluorescence. Whether AMPK mediated the isoflurane-induced apoptosis and autophagy was explored by adding an AMPK inhibitor (Compound C). The in vivo function of isoflurane was finally investigated on a HeLa cell xenograft model.

RESULTS

Isoflurane inhibited cell viability and induced apoptosis evidenced by upregulation of active caspase-3/9 in HeLa cells. Oxidative stress was triggered by isoflurane, as isoflurane elevated ROS level, and lowered ratio of NAD⁺/NADH and ATP level. Further results showed isoflurane activated the AMPK/mTOR pathway and induced autophagy. In addition, inhibition of AMPK led to ameliorated effects of isoflurane on apoptosis and autophagy. In vivo experiments proved isoflurane could repress tumorigenesis, activate AMPK, and induce autophagy in Xenograft mouse.

CONCLUSIONS

Isoflurane activated AMPK to inhibit proliferation and promote apoptosis and autophagy both in vitro and in vivo.

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.

Autophagy and Leukemia

Leukemia is a malignant clonal disease that originates from hematopoietic stem cells. As in-depth research examines the molecular biology and immunology of the hematopoietic system, leukemia treatment has evolved from a single cytotoxic drug to treatments that inducing differentiation and apoptosis. Meanwhile, autophagy has become a growing concern as a new form of cell death. The immune response, hematopoietic stem cell differentiation, and drug resistance of tumor cells are all potentially affected by autophagy. Regulating autophagy may become one of the promising directions in the field of targeted therapy.

Chidamide, a histone deacetylase inhibitor, inhibits autophagy and exhibits therapeutic implication in chronic lymphocytic leukemia

Novel agents have made the management of chronic lymphocytic leukemia (CLL) more promising and personalized. However, long-term treatment is still warranted which may result in toxicity and resistance. Thus, new combination therapy may help achieve deeper remission and limited-duration therapy. Histone deacetylase inhibitors (HDACi) can affect many tumors by modulating key biological functions including autophagy. Studies have shown that some novel targeted agents including ibrutinib induce autophagy. This study aimed to explore the effect of oral HDAC inhibitor, chidamide, on CLL cells as well as the role of autophagy in this process. Here, we showed that autophagy flux in CLL cells was inhibited by chidamide via post-transcriptional modulation and chidamide had cytostatic and cytotoxic effects on CLL cells. Besides, the pro-survival role of autophagy in CLL cells was validated by using autophagy inhibitor and knocking down critical autophagy gene. Notably, a combination of chidamide and ibrutinib showed significant synergism and downregulated ibrutinib-induced autophagy. This work highlights the therapeutic potential of chidamide via its effect on autophagy, especially in combination with ibrutinib.

Systematic Analysis of Autophagy-Related Signature Uncovers Prognostic Predictor for Acute Myeloid Leukemia

Autophagy, a highly conserved cellular protein degradation process, has been involved in acute myeloid leukemia (AML). The present study aims to establish a novel, autophagy-related prognostic signature for prediction of AML prognosis. Differentially expressed autophagy-related genes in AML and healthy samples were screened using GSE1159. Univariate Cox regression analysis was applied to determine survival-associated autophagy-related genes in The Cancer Genome Atlas (TCGA) AML cohort. Lasso regression was performed to develop multiple-gene prognostic signatures. A novel six-gene signature (including CASP3, CHAF1B, KLHL24, OPTN, VEGFA, and VPS37C) DC was established for AML prognosis prediction. The Kaplan-Meier survival analysis revealed that patients in the high-risk score group had poorer overall survival (OS). The receiver operating characteristic (ROC) curve validated its good performance in survival prediction in TCGA AML cohort, and the area under the curve value was 0.817. Moreover, our signature could independently predict OS. A nomogram was constructed, including the six-gene signature and other clinical parameters, and predictive efficiency was confirmed using the ROC curve and calibration curve. Furthermore, gene set enrichment analyses identified several tumor-associated pathways that may contribute to explain the potential molecular mechanisms of our signature. Overall, we developed a new autophagy-associated gene signature and nomogram to predict OS of AML patients, which may help in clinical decision-making for AML treatment.

EVI1 induces autophagy to promote drug resistance via regulation of ATG7 expression in leukemia cells

Ecotropic viral integration site 1 (EVI1) is an oncogenic transcription factor, which is abnormally expressed in myeloid leukemia and other several solid cancers. It is associated with short survival as well as anticancer drug resistance. Autophagy is a protective mechanism that promotes cancer cell growth and survival under stressed conditions including clinical drug treatment. Here evidences are provided that EVI1 induces autophagy and mediated drug resistance in myeloid leukemia cells. Both knockdown using RNAi and pharmacological inhibition of autophagy significantly increase sensitivity to cytotoxic drug treatment in EVI1high cells. Mechanistic studies revealed that EVI1 regulated autophagy by directly binding to autophagy-related gene autophagy related 7 (ATG7) promoter and transcriptionally upregulating its expression. Notably, ATG7 expression was positively correlated with EVI1 in bone marrow mononuclear cells from myeloid leukemia patients. Acute myeloid leukemia patients with high level of EVI1 are associated with unfavorable overall survival, which was aggravated by simultaneous high expression of ATG7 in these patients. Furthermore, ChIP and firefly luciferase reporter assay identified an EVI1-binding site at 227 upstream promoter region of ATG7 which regulated its transcription. In addition, enforced expression of EVI1 also increased intracellular reactive oxygen species and ATG7 mRNA levels as well as autophagy activity, whereas the increase was attenuated after treatment with reactive oxygen species scavenger, suggesting the involvement of reactive oxygen species in EVI1-induced autophagy. These findings demonstrate that EVI protects myeloid leukemia cell from anticancer drug treatment by inducing autophagy through dual control of ATG7. These results might present a new therapeutic approach for improving treatment outcome in myelogenous leukemia with EVI1high.

Dendrogenin A synergizes with Cytarabine to Kill Acute Myeloid Leukemia Cells In Vitro and In Vivo

Dendrogenin A (DDA) is a mammalian cholesterol metabolite that displays potent antitumor properties on acute myeloid leukemia (AML). DDA triggers lethal autophagy in cancer cells through a biased activation of the oxysterol receptor LXRβ, and the inhibition of a sterol isomerase. We hypothesize that DDA could potentiate the activity of an anticancer drug acting through a different molecular mechanism, and conducted in vitro and in vivo combination tests on AML cell lines and patient primary tumors. We report here results from tests combining DDA with antimetabolite cytarabine (Ara-C), one of the main drugs used for AML treatment worldwide. We demonstrated that DDA potentiated and sensitized AML cells, including primary patient samples, to Ara-C in vitro and in vivo. Mechanistic studies revealed that this sensitization was LXRβ-dependent and was due to the activation of lethal autophagy. This study demonstrates a positive in vitro and in vivo interaction between DDA and Ara-C, and supports the clinical evaluation of DDA in combination with Ara-C for the treatment of AML.

Overexpression of HOXA10 is associated with unfavorable prognosis of acute myeloid leukemia

Background

HOXA family genes were crucial transcription factors involving cell proliferation and apoptosis. While few studies have focused on HOXA10 in AML. We aimed to investigate the prognostic significance of HOXA10.

Methods

We downloaded datasets from GEO and BeatAML database, to compare HOXA expression level between AML patients and controls. Kaplan-Meier curves were used to estimate the impact of HOXA10 expression on AML survival. The differentially expressed genes, miRNAs, lncRNAs and methylated regions between HOXA10-high and -low groups were obtained using R (version 3.6.0). Accordingly, the gene set enrichment analysis (GSEA) was accomplished using MSigDB database. Moreover, the regulatory TFs/microRNAs/lncRNAs of HOXA10 were identified. A LASSO-Cox model fitted OS to clinical and HOXA10-associated genetic variables by glmnet package.

Results

HOXA10 was overexpressed in AML patients than that in controls. The HOXA10-high group is significantly associated with shorter OS and DFS. A total of 1219 DEGs, 131 DEmiRs, 282 DElncRs were identified to be associated with HOXA10. GSEA revealed that 12 suppressed and 3 activated pathways in HOXA10-high group. Furthermore, the integrated regulatory network targeting HOXA10 was established. The LASSO-Cox model fitted OS to AML-survival risk scores, which included age, race, molecular risk, expression of IKZF2/LINC00649/LINC00839/FENDRR and has-miR-424-5p. The time dependent ROC indicated a satisfying AUC (1-year AUC 0.839, 3-year AUC 0.871 and 5-year AUC 0.813).

Conclusions

Our study identified HOXA10 overexpression as an adverse prognostic factor for AML. The LASSO-COX regression analysis revealed novel prediction model of OS with superior diagnostic utility.

The Exploitation of Liposomes in the Inhibition of Autophagy to Defeat Drug Resistance

Autophagy is a mechanism involved in many human diseases and in cancers can have a cytotoxic/cytostatic or protective action, being in the latter case involved in multidrug resistance. Understanding which of these roles autophagy has in cancer is thus fundamental for therapeutical decisions because it permits to optimize the therapeutical approach by activating or inhibiting autophagy according to the progression of the disease. However, a serious drawback of cancer treatment is often the scarce availability of drugs and autophagy modulators at the sites of interest. In the recent years, several nanocarriers have been developed and investigated to improve the solubility, bioavailability, controlled release of therapeutics and increase their cytotoxic effect on cancer cell. Here we have reviewed only liposomes as carriers of chemotherapeutics and autophagy inhibitors because they have low toxicity and immunogenicity and they are biodegradable and versatile. In this review after the analysis of the dual role of autophagy, of the main autophagic pathways, and of the role of autophagy in multidrug resistance, we will focus on the most effective liposomal formulations, thus highlighting the great potential of these targeting systems to defeat cancer diseases.

Emerging agents that target signaling pathways in cancer stem cells

Cancer stem cells (CSCs) contribute to the initiation, recurrence, and metastasis of cancer; however, there are still no drugs targeting CSCs in clinical application. There are several signaling pathways playing critical roles in CSC progression, such as the Wnt, Hedgehog, Notch, Hippo, and autophagy signaling pathways. Additionally, targeting the ferroptosis signaling pathway was recently shown to specifically kill CSCs. Therefore, targeting these pathways may suppress CSC progression. The structure of small-molecule drugs shows a good spatial dispersion, and its chemical properties determine its good druggability and pharmacokinetic properties. These characteristics make small-molecule drugs show a great advantage in drug development, which is increasingly popular in the market. Thus, in this review, we will summarize the current researches on the small-molecule compounds suppressing CSC progression, including inhibitors of Wnt, Notch, Hedgehog, and autophagy pathways, and activators of Hippo and ferroptosis pathways. These small-molecule compounds emphasize CSC importance in tumor progression and propose a new strategy to treat cancer in clinic via targeting CSCs.

Autophagy Driven Extracellular Vesicles in the Leukaemic Microenvironment

The leukaemias are a heterogeneous group of blood cancers, which together, caused 310,000 deaths in 2016. Despite significant research into their biology and therapeutics, leukaemia is predicted to account for an increased 470,000 deaths in 2040. Many subtypes remain without targeted therapy, and therefore the mainstay of treatment remains generic cytotoxic drugs with bone marrow transplant the sole definitive option. In this review, we will focus on cellular mechanisms which have the potential for therapeutic exploitation to specifically target and treat this devastating disease. We will bring together the disciplines of autophagy and extracellular vesicles, exploring how the dysregulation of these mechanisms can lead to changes in the leukaemic microenvironment and the subsequent propagation of disease. The dual effect of these mechanisms in the disease microenvironment is not limited to leukaemia; therefore, we briefly explore their role in autoimmunity, inflammation and degenerative disease.

Transient receptor potential ion channel TRPM2 promotes AML proliferation and survival through modulation of mitochondrial function, ROS, and autophagy

Transient receptor potential melastatin 2 (TRPM2) ion channel has an essential function in maintaining cell survival following oxidant injury. Here, we show that TRPM2 is highly expressed in acute myeloid leukemia (AML). The role of TRPM2 in AML was studied following depletion with CRISPR/Cas9 technology in U937 cells. In in vitro experiments and in xenografts, depletion of TRPM2 in AML inhibited leukemia proliferation, and doxorubicin sensitivity was increased. Mitochondrial function including oxygen consumption rate and ATP production was reduced, impairing cellular bioenergetics. Mitochondrial membrane potential and mitochondrial calcium uptake were significantly decreased in depleted cells. Mitochondrial reactive oxygen species (ROS) were significantly increased, and Nrf2 was decreased, reducing the antioxidant response. In TRPM2-depleted cells, ULK1, Atg7, and Atg5 protein levels were decreased, leading to autophagy inhibition. Consistently, ATF4 and CREB, two master transcription factors for autophagosome biogenesis, were reduced in TRPM2-depleted cells. In addition, Atg13 and FIP200, which are known to stabilize ULK1 protein, were decreased. Reconstitution with TRPM2 fully restored proliferation, viability, and autophagy; ATF4 and CREB fully restored proliferation and viability but only partially restored autophagy. TRPM2 expression reduced the elevated ROS found in depleted cells. These data show that TRPM2 has an important role in AML proliferation and survival through regulation of key transcription factors and target genes involved in mitochondrial function, bioenergetics, the antioxidant response, and autophagy. Targeting TRPM2 may represent a novel therapeutic approach to inhibit myeloid leukemia growth and enhance susceptibility to chemotherapeutic agents through multiple pathways.

Can the microbiota predict response to systemic cancer therapy, surgical outcomes, and survival? The answer is in the gut

INTRODUCTION

The gut microbiota seems to play a key role in tumorigenesis, across various hallmarks of cancer. Recent evidence suggests its potential use as a biomarker predicting drug response and adding prognostic information, generally in the context of immuno-oncology.

AREAS COVERED

In this review, we focus on the modulating effects of gut microbiota dysbiosis on various anticancer molecules used in practice, including cytotoxic and immune-modulating agents, primarily immune-checkpoint inhibitors (ICI). Pubmed/Medline-based literature search was conducted to find potential original studies that discuss gut microbiota as a prognostic and predictive biomarker for cancer therapy. We also looked at the US ClinicalTrials.gov website to find additional studies particularly ongoing human clinical trials.

EXPERT COMMENTARY

Sequencing of stool-derived materials and tissue samples from cancer patients and animal models has shown a significant enrichment of various bacteria such as Fusobacterium nucleatum and Bacteroides fragilis were associated with resistant disease and poorer outcomes. Gut microbiota was also found to be associated with surgical outcomes and seems to play a significant role in anastomotic leak (ATL) after surgery mainly by collagen breakdown. However, this research field is just at the beginning and the current findings are not yet ready to change clinical practice.

MicroRNA-30a targets BECLIN-1 to inactivate autophagy and sensitizes gastrointestinal stromal tumor cells to imatinib

Gastrointestinal stromal tumors (GISTs), the most widespread type of sarcoma, contain driver gene mutations predominantly of receptor tyrosine kinase and platelet-derived growth factor receptor alpha. However, the inevitable development of resistance to imatinib (IM) cannot be fully attributed to secondary driver gene mutations. In this study, we investigated the role of microRNA-30a in sensitization of GIST cells to IM in vivo and in vitro. Higher levels of miR-30a were detected in GIST-T1 cells, which were more sensitive to IM than GIST-882 cells. IM treatment also reduced miR-30a levels, indicating the possible role of miR-30a in GIST IM resistance. Subsequently, miR-30a was confirmed to be an IM sensitizer via a mechanism that was attributed to its involvement in the regulation of cell autophagy. The interaction of miR-30a and autophagy in IM treated GIST cells was found to be linked by beclin-1. Beclin-1 knockdown increased IM sensitivity in GIST cell lines. Finally, miR-30a was confirmed to enhance IM sensitivity of GIST cells in mouse tumor models. Our study provides evidence for the possible role of miR-30a in the emergence of secondary IM resistance in GIST patients, indicating a promising target for overcoming this chemoresistance.

Assessing Autophagy in Archived Tissue or How to Capture Autophagic Flux from a Tissue Snapshot

Autophagy is a highly conserved degradation mechanism that is essential for maintaining cellular homeostasis. In human disease, autophagy pathways are frequently deregulated and there is immense interest in targeting autophagy for therapeutic approaches. Accordingly, there is a need to determine autophagic activity in human tissues, an endeavor that is hampered by the fact that autophagy is characterized by the flux of substrates whereas histology informs only about amounts and localization of substrates and regulators at a single timepoint. Despite this challenging task, considerable progress in establishing markers of autophagy has been made in recent years. The importance of establishing clear-cut autophagy markers that can be used for tissue analysis cannot be underestimated. In this review, we attempt to summarize known techniques to quantify autophagy in human tissue and their drawbacks. Furthermore, we provide some recommendations that should be taken into consideration to improve the reliability and the interpretation of autophagy biomarkers in human tissue samples.

17-DMAG disrupted the autophagy flux leading to the apoptosis of acute lymphoblastic leukemia cells by inducing heat shock cognate protein 70

AIMS

B-lineage acute lymphoblastic leukemia (B-ALL) is most common in children. We had reported heat shock protein 90 (Hsp90) over-expressed in high risk B-ALL children. 17-DMAG is a water soluble Hsp90 inhibitor, which was proved to be effective for advanced solid tumors and hematological malignancy. However, there is little research on its application in newly diagnosed B-ALL. And the detailed mechanism is seldom discussed.

MAIN METHODS

Primary blast cells from 24 newly diagnosed B-ALL pediatric patients and two B-ALL cell lines were used in this study. Cell viability was measured by MTS assay. Apoptosis was evaluated by flow cytometry after annexin V-PI double staining. Protein expression was detected by immunoblotting analysis and immunofluorescence imaging. Cyto-ID autophagy detection assay was performed to show the autophagosomes and LysoTracker labeling to show the lysosomes. Gene knockdown was performed by RNA interference, and mRNA expression was measured by RT-qPCR.

KEY FINDINGS

We showed 17-DMAG induced apoptosis in newly diagnosed B-ALL blasts and cell lines effectively. 17-DMAG induced heat shock cognate protein 70 (Hsc70) expression significantly. High expressed Hsc70 inhibited cathepsin D post-transcriptionally to impede the autophagic flux, which lead to the cell death.

SIGNIFICANCE

Our work added new information towards understanding the molecular pharmacology of 17-DMAG, and suggested the newly diagnosed B-ALL pediatric patients might be benefited from 17-DMAG. Furthermore, we proved Hsc70 participated in the mechanism of cell death 17-DMAG leading in B-ALL.

Autophagy and disease: unanswered questions

Autophagy is a process in which intracellular components and dysfunctional organelles are delivered to the lysosome for degradation and recycling. Autophagy has various connections to a large number of human diseases, as its functions are essential for cell survival, bioenergetic homeostasis, organism development, and cell death regulation. In the past two decades, substantial effort has been made to identify the roles of autophagy in tumor suppression and promotion, neurodegenerative disorders, and other pathophysiologies. This review summarizes the current advances and discusses the unanswered questions in understanding the involvement of autophagy in pathogenic mechanisms of disease, primarily focusing on cancer and neurodegenerative diseases.

Understanding intrinsic hematopoietic stem cell aging

Hematopoietic stem cells (HSC) sustain blood production over the entire life-span of an organism. It is of extreme importance that these cells maintain self-renewal and differentiation potential over time in order to preserve homeostasis of the hematopoietic system. Many of the intrinsic aspects of HSC are affected by the aging process resulting in a deterioration in their potential, independently of their microenvironment. Here we review recent findings characterizing most of the intrinsic aspects of aged HSC, ranging from phenotypic to molecular alterations. Historically, DNA damage was thought to be the main cause of HSC aging. However, over recent years, many new findings have defined an increasing number of biological processes that intrinsically change with age in HSC. Epigenetics and chromatin architecture, together with autophagy, proteostasis and metabolic changes, and how they are interconnected, are acquiring growing importance for understanding the intrinsic aging of stem cells. Given the increase in populations of older subjects worldwide, and considering that aging is the primary risk factor for most diseases, understanding HSC aging becomes particularly relevant also in the context of hematologic disorders, such as myelodysplastic syndromes and acute myeloid leukemia. Research on intrinsic mechanisms responsible for HSC aging is providing, and will continue to provide, new potential molecular targets to possibly ameliorate or delay aging of the hematopoietic system and consequently improve the outcome of hematologic disorders in the elderly. The niche-dependent contributions to hematopoietic aging are discussed in another review in this same issue of the Journal.

Biological Functions of Autophagy Genes: A Disease Perspective

The lysosomal degradation pathway of autophagy plays a fundamental role in cellular, tissue, and organismal homeostasis and is mediated by evolutionarily conserved autophagy-related (ATG) genes. Definitive etiological links exist between mutations in genes that control autophagy and human disease, especially neurodegenerative, inflammatory disorders and cancer. Autophagy selectively targets dysfunctional organelles, intracellular microbes, and pathogenic proteins, and deficiencies in these processes may lead to disease. Moreover, ATG genes have diverse physiologically important roles in other membrane-trafficking and signaling pathways. This Review discusses the biological functions of autophagy genes from the perspective of understanding-and potentially reversing-the pathophysiology of human disease and aging.

Chaperone-Mediated Autophagy and Its Emerging Role in Hematological Malignancies

Chaperone-mediated autophagy (CMA) ensures the selective degradation of cellular proteins endowed with a KFERQ-like motif by lysosomes. It is estimated that 30% of all cellular proteins can be directed to the lysosome for CMA degradation, but only a few substrates have been formally identified so far. Mechanistically, the KFERQ-like motifs present in substrate proteins are recognized by the molecular chaperone Hsc70c (Heat shock cognate 71 kDa protein cytosolic), also known as HSPA8, and directed to LAMP2A, which acts as the CMA receptor at the lysosomal surface. Following linearization, the protein substrate is next transported to the lumen of the lysosomes, where it is degraded by resident proteases, mainly cathepsins and eventually recycled to sustain cellular homeostasis. CMA is induced by different stress conditions, including energy deprivation that also activates macro-autophagy (MA), that may make it difficult to decipher the relative impact of both pathways on cellular homeostasis. Besides common inducing triggers, CMA and MA might be induced as compensatory mechanisms when either mechanism is altered, as it is the often the case in different pathological settings. Therefore, CMA activation can compensate for alterations of MA and vice versa. In this context, these compensatory mechanisms, when occurring, may be targeted for therapeutic purposes. Both processes have received particular attention from scientists and clinicians, since modulation of MA and CMA may have a profound impact on cellular proteostasis, metabolism, death, differentiation, and survival and, as such, could be targeted for therapeutic intervention in degenerative and immune diseases, as well as in cancer, including hematopoietic malignancies. The role of MA in cancer initiation and progression is now well established, but whether and how CMA is involved in tumorigenesis has been only sparsely explored. In the present review, we encompass the description of the mechanisms involved in CMA, its function in the physiology and pathogenesis of hematopoietic cells, its emerging role in cancer initiation and development, and, finally, the potential therapeutic opportunity to target CMA or CMA-mediated compensatory mechanisms in hematological malignancies.

Differential redox-regulation and mitochondrial dynamics in normal and leukemic hematopoietic stem cells: A potential window for leukemia therapy

The prognosis for many patients with acute myeloid leukemia (AML) is poor, mainly due to disease relapse driven by leukemia stem cells (LSCs). Recent studies have highlighted the unique metabolic properties of LSCs, which might represent opportunities for LSC-selective targeting. LSCs characteristically have low levels of reactive oxygen species (ROS), which apparently result from a combination of low mitochondrial activity and high activity of ROS-removing pathways such as autophagy. Due to this low activity, LSCs are highly dependent on mitochondrial regulatory mechanisms. These include the anti-apoptotic protein BCL-2, which also has crucial roles in regulating the mitochondrial membrane potential, and proteins involved in mitophagy. Here we review the different pathways that impact mitochondrial activity and redox-regulation, and highlight their relevance for the functionality of both HSCs and LSCs. Additionally, novel AML therapy strategies that are based on interference with those pathways, including the promising BCL-2 inhibitor Venetoclax, are summarized.

Targeting Metabolic Reprogramming in Acute Myeloid Leukemia

The cancer metabolic reprogramming allows the maintenance of tumor proliferation, expansion and survival by altering key bioenergetics, biosynthetic and redox functions to meet the higher demands of tumor cells. In addition, several metabolites are also needed to perform signaling functions that further promote tumor growth and progression. These metabolic alterations have been exploited in different cancers, including acute myeloid leukemia, as novel therapeutic strategies both in preclinical models and clinical trials. Here, we review the complexity of acute myeloid leukemia (AML) metabolism and discuss how therapies targeting different aspects of cellular metabolism have demonstrated efficacy and how they provide a therapeutic window that should be explored to target the metabolic requirements of AML cells.

CPX Targeting DJ-1 Triggers ROS-induced Cell Death and Protective Autophagy in Colorectal Cancer

Rationale: Colorectal cancer (CRC) is one of the most common cancers worldwide. Ciclopirox olamine (CPX) has recently been identified to be a promising anticancer candidate; however, novel activities and detailed mechanisms remain to be uncovered.

Methods: The cytotoxic potential of CPX towards CRC cells was examined in vitro and in vivo. The global gene expression pattern, ROS levels, mitochondrial function, autophagy, apoptosis, etc. were determined between control and CPX-treated CRC cells.

Results: We found that CPX inhibited CRC growth by inhibiting proliferation and inducing apoptosis both in vitro and in vivo. The anti-cancer effects of CPX involved the downregulation of DJ-1, and overexpression of DJ-1 could reverse the cytotoxic effect of CPX on CRC cells. The loss of DJ-1 resulted in mitochondrial dysfunction and ROS accumulation, thus leading to CRC growth inhibition. The cytoprotective autophagy was provoked simultaneously, and blocking autophagy pharmacologically or genetically could further enhance the anti-cancer efficacy of CPX.

Conclusion: Our study demonstrates that DJ-1 loss-induced ROS accumulation plays a pivotal role in CPX-mediated CRC inhibition, providing a further understanding for CRC treatment via modulating compensatory protective autophagy.

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.

Elevated VMP1 expression in acute myeloid leukemia amplifies autophagy and is protective against venetoclax-induced apoptosis

Vacuole membrane protein (VMP1) is a putative autophagy protein, which together with Beclin-1 acts as a molecular switch in activating autophagy. In the present study the role of VMP1 was analysed in CD34⁺ cells of cord blood (CB) and primary acute myeloid leukemia (AML) cells and cell lines. An increased expression of VMP1 was observed in a subset of AML patients. Functional studies in normal CB CD34⁺ cells indicated that inhibiting VMP1 expression reduced autophagic-flux, coinciding with reduced expansion of hematopoietic stem and progenitor cells (HSPC), delayed differentiation, increased apoptosis and impaired in vivo engraftment. Comparable results were observed in leukemic cell lines and primary AML CD34⁺ cells. Ultrastructural analysis indicated that leukemic cells overexpressing VMP1 displayed a reduced number of mitochondrial structures, while the number of lysosomal degradation structures was increased. The overexpression of VMP1 did not affect cell proliferation and differentiation, but increased autophagic-flux and improved mitochondrial quality, which coincided with an increased threshold for venetoclax-induced loss of mitochondrial outer membrane permeabilization (MOMP) and apoptosis. In conclusion, our data indicate that in leukemic cells high VMP1 is involved with mitochondrial quality control.

Protective autophagy decreases osimertinib cytotoxicity through regulation of stem cell-like properties in lung cancer

Osimertinib, a third-generation epidermal growth factor receptor - tyrosine kinase inhibitor (EGFR-TKI), shows great efficacy in EGFR-mutant non-small cell lung cancer (NSCLC); however, the resistance is inevitable. Osimertinib induces autophagy in NSCLC cells, but the role of autophagy in osimertinib resistance is not clear. We discovered that enhanced autophagy is associated with osimertinib resistance in vitro and in vivo. Inhibition of autophagy enhanced osimertinib cytotoxicity in both osimertinib-resistant and sensitive cells. Moreover, osimertinib-resistant cells exhibited stem cell-like properties, whereas autophagy inhibition decreased the stemness by downregulating the expression of SOX2 and ALDH1A1. Further, we found that knockdown of Beclin-1 inhibited the stem cell-like properties and restored osimertinib cytotoxicity. Osimertinib combined with chloroquine inhibited tumor growth more effectively than alone in xenograft mice. These results reveal that autophagy plays an adverse role in osimertinib cytotoxicity through inducing stem cell-like properties. Combination therapy of EGFR-TKI and autophagy inhibitor could provide a promising strategy to improve osimertinib cytotoxicity.

TRPM2 in Cancer

The TRP ion channel TRPM2 has an essential function in cell survival and protects the viability of a number of cell types after oxidative stress. It is highly expressed in many cancers including breast, prostate, and pancreatic cancer, melanoma, leukemia, and neuroblastoma, suggesting it promotes cancer cell survival. TRPM2 is activated by production of ADP-ribose (ADPR) following oxidative stress, which binds to the C-terminus of TRPM2, resulting in channel opening. In a number of cancers including neuroblastoma, TRPM2 has been shown to preserve viability and mechanisms have been identified. Activation of TRPM2 results in expression of transcription factors and kinases important in cell proliferation and survival including HIF-1/2α, CREB, nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2), and Pyk2, and Src phosphorylation. Together, HIF-1/2α and CREB regulate expression of genes encoding proteins with roles in mitochondrial function including members of the electron transport complex involved in ATP production. These contribute to lower mitochondrial ROS production while expression of antioxidants regulated by HIF-1/2α, FOXO3a, CREB, and Nrf2 is maintained. CREB is also important in control of expression of key proteins involved in autophagy. When TRPM2-mediated calcium influx is inhibited, mitochondria are dysfunctional, cellular bioenergetics are reduced, production of ROS is increased, and autophagy and DNA repair are impaired, decreasing tumor growth and increasing chemotherapy sensitivity. Inhibition of TRPM2 expression or function results in decreased tumor proliferation and/or viability in many malignancies including breast, gastric, pancreatic, prostate, head and neck cancers, melanoma, neuroblastoma, and T-cell and acute myelogenous leukemia. However, in a small number of malignancies, activation of TRPM2 rather than inhibition has been reported to reduce tumor cell survival. Here, TRPM2-mediated Ca²⁺ signaling and mechanisms of regulation of cancer cell growth and survival are reviewed and controversies discussed. Evidence suggests that targeting TRPM2 may be a novel therapeutic approach in many cancers.

Autophagy and cancer stem cells: molecular mechanisms and therapeutic applications

Autophagy and mitophagy act in cancer as bimodal processes, whose differential functions strictly depend on cancer ontogenesis, progression, and type. For instance, they can act to promote cancer progression by helping cancer cells survive stress or, instead, when mutated or abnormal, to induce carcinogenesis by influencing cell signaling or promoting intracellular toxicity. For this reason, the study of autophagy in cancer is the main focus of many researchers and several clinical trials are already ongoing to manipulate autophagy and by this way determine the outcome of disease therapy. Since the establishment of the cancer stem cell (CSC) theory and the discovery of CSCs in individual cancer types, autophagy and mitophagy have been proposed as key mechanisms in their homeostasis, dismissal or spread, even though we still miss a comprehensive view of how and by which regulatory molecules these two processes drive cell fate. In this review, we will dive into the deep water of autophagy, mitophagy, and CSCs and offer novel viewpoints on possible therapeutic strategies, based on the modulation of these degradative systems.

Emerging Therapies for Acute Myelogenus Leukemia Patients Targeting Apoptosis and Mitochondrial Metabolism

Acute Myelogenous Leukemia (AML) is a malignant disease of the hematopoietic cells, characterized by impaired differentiation and uncontrolled clonal expansion of myeloid progenitors/precursors, resulting in bone marrow failure and impaired normal hematopoiesis. AML comprises a heterogeneous group of malignancies, characterized by a combination of different somatic genetic abnormalities, some of which act as events driving leukemic development. Studies carried out in the last years have shown that AML cells invariably have abnormalities in one or more apoptotic pathways and have identified some components of the apoptotic pathway that can be targeted by specific drugs. Clinical results deriving from studies using B-cell lymphoma 2 (BCL-2) inhibitors in combination with standard AML agents, such as azacytidine, decitabine, low-dose cytarabine, provided promising results and strongly support the use of these agents in the treatment of AML patients, particularly of elderly patients. TNF-related apoptosis-inducing ligand (TRAIL) and its receptors are frequently deregulated in AML patients and their targeting may represent a promising strategy for development of new treatments. Altered mitochondrial metabolism is a common feature of AML cells, as supported through the discovery of mutations in the isocitrate dehydrogenase gene and in mitochondrial electron transport chain and of numerous abnormalities of oxidative metabolism existing in AML subgroups. Overall, these observations strongly support the view that the targeting of mitochondrial apoptotic or metabolic machinery is an appealing new therapeutic perspective in AML.

Downregulation of ENDOCAN in myeloid leukemia cells inhibits proliferation and promotes apoptosis by suppressing nuclear factor‑κB activity

Previous studies have demonstrated that ENDOCAN is elevated in leukemia, and it has been reported to be associated with poor prognosis. However, the functional role of ENDOCAN in the development of leukemia remains to be fully elucidated. In the present study, the expression levels of ENDOCAN were detected in THP‑1, U937, HL‑60 and K562 cells, and it was found that ENDOCAN was increased in U937 and K562 cells, compared with the other two cell lines. Subsequently, ENDOCAN was knocked down in U937 and K562 cells via lentiviral infection. It was found that cell proliferation and the expression of proliferating cell nuclear antigen were inhibited in myeloid leukemia cells following the silencing of ENDOCAN. ENDOCAN knockdown induced G0/G1‑phase cell cycle arrest in myeloid leukemia cells with a decreased expression of cyclin D1. Furthermore, cell apoptosis was increased in response to ENDOCAN silencing, which was accompanied by the downregulation of B‑cell lymphoma (BCL2) and the upregulation of BCL2‑associated X protein, cleaved caspases 3 and 9, and cleaved poly (ADP‑ribose) polymerase. Furthermore, it was demonstrated that the knockdown of ENDOCAN inhibited nuclear factor‑κB (NF‑κB) activity, as evidenced by the increased expression of NF‑κB inhibitor α (IκBα), decreased expression of phosphorylated (p‑)IκBα, p‑P65 and nuclear P65, and reduced NF‑κB DNA‑binding activity. In combination, the present findings suggested that ENDOCAN may serve as a potential therapeutic target in the treatment of leukemia.

20(S)-ginsenoside Rg3 sensitizes human non-small cell lung cancer cells to icotinib through inhibition of autophagy

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have become a standard therapy for non-small cell lung cancer (NSCLC) patients with sensitive mutations. However, acquired resistance inevitably emerges after a median of 6-12 months. It has been demonstrated that autophagy plays an important role in EGFR-TKI resistance. 20(S)-ginsenoside Rg3 (Rg3) is proposed to sensitize the cancer cells to chemotherapy by inhibiting autophagy. We examined the ability of Rg3 to inhibit autophagy and increase the sensitivity of NSCLC cells to icotinib. We show that the induction of autophagy in response to icotinib contributes to the development of icotinib resistance. Rg3 is capable of inhibiting autophagic flux and enhancing the sensitivity of NSCLC cells to icotinib. The resistance to icotinib could also be reversed through Rg3-induced autophagy inhibition. Autophagy inhibition by Rg3 increases the therapeutic response in both icotinib-sensitive and icotinib-resistant NSCLC cells with an EGFR-activating mutation and may be an effective new treatment strategy for this disease.

The small-molecule compound AC-73 targeting CD147 inhibits leukemic cell proliferation, induces autophagy and increases the chemotherapeutic sensitivity of acute myeloid leukemia cells

CD147 is a transmembrane glycoprotein with multiple functions in human healthy tissues and diseases, in particular in cancer. Overexpression of CD147 correlates with biological functions that promote tumor progression and confers resistance to chemotherapeutic drugs. In contrast to solid tumors, the role of CD147 has not been extensively studied in leukemia. Understanding whether CD147 represents a new hematologic target and whether its inhibitor AC-73 may be used in leukemia therapy may reveal an alternative treatment strategy in patients with acute myeloid leukemia (AML). We analyzed CD147 expression and function in hematopoietic progenitor cells from normal cord blood, in several leukemic cell lines and in primary leukemic blasts obtained from patients with AML. We investigated the effects of AC-73, used alone or in combination with arabinosylcytosine (Ara-C) and arsenic trioxide (ATO), on leukemic cell proliferation. We demonstrated that CD147 overexpression promotes leukemic cell proliferation. We showed that AC-73 exhibits a potent growth inhibitory activity in leukemic cells, by inhibiting the ERK/STAT3 activation pathway and activating autophagy. We demonstrated that AC-73 exerts an anti-proliferative effect additive to chemotherapy by enhancing leukemic cell sensitivity to Ara-C-induced cytotoxicity or to ATO-induced autophagy. We also reported CD147 expression in the fraction of leukemic blasts expressing CD371, a marker of leukemic stem cells. Altogether, our study indicates CD147 as a novel potential target in the treatment of AML and AC-73 as an anti-proliferative drug and an inducer of autophagy in leukemic cells to use in combination with chemotherapeutic agents.

Distinct role of autophagy on angiogenesis: highlights on the effect of autophagy in endothelial lineage and progenitor cells

Autophagy plays a critical role in the dynamic growth of each cell through different conditions. It seems that this intracellular mechanism acts as a two-edged sword against the numerous cell insults. Previously, autophagy was described in the context of cell activity and behavior, but little knowledge exists related to the role of autophagy in endothelial cells, progenitors, and stem cells biology from different tissues. Angiogenic behavior of endothelial lineage and various stem cells are touted as an inevitable feature in the restoration of different damaged tissues and organs. This capacity was found to be dictated by autophagy signaling pathway. This review article highlights the fundamental role of cell autophagic response in endothelial cells function, stem cells dynamic, and differentiation rate. It seems that elucidation of the mechanisms related to pro- and/or anti-angiogenic potential of autophagy inside endothelial cells and stem cells could help us to modulate stem cell therapeutic feature post-transplantation.

The Ins and Outs of Autophagy and Metabolism in Hematopoietic and Leukemic Stem Cells: Food for Thought

Discovered over fifty years ago, autophagy is a double-edged blade. On one hand, it regulates cellular energy sources by "cannibalization" of its own cellular components, feeding on proteins and other unused cytoplasmic factors. On the other, it is a recycling process that removes dangerous waste from the cytoplasm keeping the cell clean and healthy. Failure of the autophagic machinery is translated in dysfunction of the immune response, in aging, and in the progression of pathologies such as Parkinson disease, diabetes, and cancer. Further investigation identified autophagy with a protective role in specific types of cancer, whereas in other cases it can promote tumorigenesis. Evidence shows that treatment with chemotherapeutics can upregulate autophagy in order to maintain a stable intracellular environment promoting drug resistance and cell survival. Leukemia, a blood derived cancer, represents one of the malignancies in which autophagy is responsible for drug treatment failure. Inhibition of autophagy is becoming a strategic target for leukemic stem cell (LSC) eradication. Interestingly, the latest findings demonstrate that LSCs show higher levels of mitochondrial metabolism compared to normal stem cells. With this review, we aim to explore the links between autophagy and metabolism in the hematopoietic system, with special focus on primitive LSCs.

Signalling mechanisms that regulate metabolic profile and autophagy of acute myeloid leukaemia cells

Acute myeloid leukaemia (AML) comprises a heterogeneous group of hematologic neoplasms characterized by diverse combinations of genetic, phenotypic and clinical features representing a major challenge for the development of targeted therapies. Metabolic reprogramming, mainly driven by deregulation of the nutrient‐sensing pathways as AMPK, mTOR and PI3K/AKT, has been associated with cancer cells, including AML cells, survival and proliferation. Nevertheless, the role of these metabolic adaptations on the AML pathogenesis is still controversial. In this work, the metabolic status and the respective metabolic networks operating in different AML cells (NB‐4, HL‐60 and KG‐1) and their impact on autophagy and survival was characterized. Data show that whereas KG‐1 cells exhibited preferential mitochondrial oxidative phosphorylation metabolism with constitutive co‐activation of AMPK and mTORC1 associated with increased autophagy, NB‐4 and HL‐60 cells displayed a dependent glycolytic profile mainly associated with AKT/mTORC1 activation and low autophagy flux. Inhibition of AKT is disclosed as a promising therapeutical target in some scenarios while inhibition of AMPK and mTORC1 has no major impact on KG‐1 cells’ survival. The results highlight an exclusive metabolic profile for each tested AML cells and its impact on determination of the anti‐leukaemia efficacy and on personalized combinatory therapy with conventional and targeted agents.

Suppression of autophagy and HCK signaling promotes PTGS2high FCGR3- NK cell differentiation triggered by ectopic endometrial stromal cells

Impaired NK cell cytotoxic activity contributes to the local dysfunctional immune environment in endometriosis (EMS), which is an estrogen-dependent gynecological disease that affects the function of ectopic endometrial tissue clearance. The reason for the impaired cytotoxic activity of NK cells in an ectopic lesion microenvironment (ELM) is largely unknown. In this study, we show that the macroautophagy/autophagy level of endometrial stromal cells (ESCs) from EMS decreased under negative regulation of estrogen. The ratio of peritoneal FCGR3^- NK to FCGR3⁺ NK cells increases as EMS progresses. Moreover, the autophagy suppression results in the downregulation of HCK (hematopoietic cellular kinase) by inactivating STAT3 (signal transducer and activator of transcription 3), as well as the increased secretion of the downstream molecules CXCL8/IL8 and IL23A by ESCs, and this increase induced the upregulation of FCGR3^- NK cells and decline of cytotoxic activity in ELM. This process is mediated through the depression of microRNA MIR1185-1-3p, which is associated with the activation of the target gene PTGS2 in NK cells. FCGR3^- NK with a phenotype of PTGS2/COX2^high IFNG^low PRF1^low GZMB^low induced by hck knockout (hck^-/-) or 3-methyladenine (3-MA, an autophagy inhibitor)-stimulated ESCs accelerates ESC's growth both in vitro and in vivo. These results suggest that the estrogen-autophagy-STAT3-HCK axis participates in the differentiation of PTGS2^high IFNG^low PRF1^low GZMB^low FCGR3^- NK cells in ELM and contributes to the development of EMS. This result provides a scientific basis for potential therapeutic strategies to treat diseases related to impaired NK cell cytotoxic activity.

ABBREVIATIONS

anti-FCGR3: anti-FCGR3 with neutralizing antibody; Ctrl-ESC: untreated ESCs; CXCL8: C-X-C motif chemokine ligand 8; ectoESC: ESCs from ectopic lesion; ELM: ectopic lesion microenvironment; EMS: endometriosis; ESCs: endometrial stromal cells; eutoESC:eutopic ESCs; HCK: hematopoietic cellular kinase; HCK(OE): overexpression of HCK; IFNG: interferon gamma; IL23A (OE): overexpression of IL23A; KLRK1: Killer cell lectin like receptor K1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; 3 -MA: 3-methyladenine; 3-MA-ESC: 3-MA-treated ESCs; MIR1185-1-3p⁺: overexpression of HsMIR1185-1-3p; NK: natural killer; normESCs: normal ESCs; Rap-ESC:rapamycin-treated ESCs; PCNA: proliferating cell nuclear antigen; PF: peritoneal fluid; SFKs: SRC family of cytoplasmic tyrosine kinases; si-HCK: silencing of HCK; siIL23A: silencing of IL23A; USCs: uterus stromal cells.

cAMP-mediated autophagy inhibits DNA damage-induced death of leukemia cells independent of p53

Autophagy is important in regulating the balance between cell death and survival, with the tumor suppressor p53 as one of the key components in this interplay. We have previously utilized an in vitro model of the most common form of childhood cancer, B cell precursor acute lymphoblastic leukemia (BCP-ALL), to show that activation of the cAMP signaling pathway inhibits p53-mediated apoptosis in response to DNA damage in both cell lines and primary leukemic cells. The present study reveals that cAMP-mediated survival of BCP-ALL cells exposed to DNA damaging agents, involves a critical and p53-independent enhancement of autophagy. Although autophagy generally is regarded as a survival mechanism, DNA damage-induced apoptosis has been linked both to enhanced and reduced levels of autophagy. Here we show that exposure of BCP-ALL cells to irradiation or cytotoxic drugs triggers autophagy and cell death in a p53-dependent manner. Stimulation of the cAMP signaling pathway further augments autophagy and inhibits the DNA damage-induced cell death concomitant with reduced nuclear levels of p53. Knocking-down the levels of p53 reduced the irradiation-induced autophagy and cell death, but had no effect on the cAMP-mediated autophagy. Moreover, prevention of autophagy by bafilomycin A1 or by the ULK-inhibitor MRT68921, diminished the protecting effect of cAMP signaling on DNA damage-induced cell death. Having previously proposed a role of the cAMP signaling pathway in development and treatment of BCP-ALLs, we here suggest that inhibitors of autophagy may improve current DNA damage-based therapy of BCP-ALL - independent of p53.

BET Inhibition Suppresses S100A8 and S100A9 Expression in Acute Myeloid Leukemia Cells and Synergises with Daunorubicin in Causing Cell Death

S100A8 and S100A9 are both members of the S100 family and have been shown to play roles in myeloid differentiation, autophagy, apoptosis, and chemotherapy resistance. In this study we demonstrate that the BET-bromodomain inhibitor JQ1 causes rapid suppression of S100A8 and S100A9 mRNA and protein in a reversible manner. In addition, we show that JQ1 synergises with daunorubicin in causing AML cell death. Daunorubicin alone causes a dose- and time-dependent increase in S100A8 and S100A9 protein levels in AML cell lines which is overcome by cotreatment with JQ1. This suggests that JQ1 synergises with daunorubicin in causing apoptosis via suppression of S100A8 and S100A9 levels.

The ginsenoside PPD exerts anti-endometriosis effects by suppressing estrogen receptor-mediated inhibition of endometrial stromal cell autophagy and NK cell cytotoxicity

Endometriosis (EMS) is an estrogen-dependent gynecological disease with a low autophagy level of ectopic endometrial stromal cells (eESCs). Impaired NK cell cytotoxic activity is involved in the clearance obstruction of the ectopic endometrial tissue in the abdominopelvic cavity. Protopanaxadiol (PPD) and protopanaxatriol (PPT) are two metabolites of ginsenosides, which have profound biological functions, such as anti-cancer activities. However, the role and mechanism of ginsenosides and metabolites in endometriosis are completely unknown. Here, we found that the compounds PPD, PPT, ginsenoside-Rg3 (G-Rg3), ginsenoside-Rh2 (G-Rh2), and esculentoside A (EsA) led to significant decreases in the viability of eESCs, particularly PPD (IC50 = 30.64 µM). In vitro and in vivo experiments showed that PPD promoted the expression of progesterone receptor (PR) and downregulated the expression of estrogen receptor α (ERα) in eESCs. Treatment with PPD obviously induced the autophagy of eESCs and reversed the inhibitory effect of estrogen on eESC autophagy. In addition, eESCs pretreated with PPD enhanced the cytotoxic activity of NK cells in response to eESCs. PPD decreased the numbers and suppressed the growth of ectopic lesions in a mouse EMS model. These results suggest that PPD plays a role in anti-EMS activation, possibly by restricting estrogen-mediated autophagy regulation and enhancing the cytotoxicity of NK cells. This result provides a scientific basis for potential therapeutic strategies to treat EMS by PPD or further structural modification.

c-MYC and reactive oxygen species play roles in tetrandrine-induced leukemia differentiation

Tetrandrine is a broadly used bisbenzylisoquinoline alkaloid component of traditional Chinese medicine that has antitumor effects in some cancer types. In this study, we investigated the effects of tetrandrine on leukemia in vitro and in vivo. The results showed that tetrandrine effectively induced differentiation and autophagy in leukemia cells. In addition, tetrandrine treatment activated the accumulation of reactive oxygen species (ROS) and inhibited c-MYC protein expression. Further, we found that treatment with the ROS scavengers N-acetyl-L-cysteine (NAC) and Tiron as well as overexpression of c-MYC reduced tetrandrine-induced autophagy and differentiation. Moreover, a small molecular c-MYC inhibitor, 10058-F4, enhanced the tetrandrine-induced differentiation of leukemia cells. These results suggest that ROS generation and c-MYC suppression play important roles in tetrandrine-induced autophagy and differentiation, and the results from in vivo experiments were consistent with those from in vitro studies. Therefore, our data suggest that tetrandrine may be a promising agent for the treatment of leukemia.