High glucose and hyperglycemic sera from type 2 diabetic patients impair DC differentiation by inducing ROS and activating Wnt/ß-catenin and p38 MAPK.

Type 2 is the type of diabetes with higher prevalence in contemporary time, representing about 90% of the global cases of diabetes. In the course of diabetes, several complications can occur, mostly due to hyperglycemia and increased reactive oxygen species (ROS) production. One of them is represented by an increased susceptibility to microbial infections and by a reduced capacity to clear them. Therefore, knowing the impact of hyperglycemia on immune system functionality is of utmost importance for the management of the disease. In this study, we show that medium containing high glucose reduced the in-vitro differentiation of monocytes into functional DCs and their activation mediated by PAMPs or DAMPs. Most importantly, the same effects were mediated by the hyperglycemic sera derived by type 2 diabetic patients, mimicking a more physiologic condition. DC dysfunction caused by hyperglycemia may be involved in the inefficient control of infections observed in diabetic patients, given the pivotal role of these cells in both the innate and adaptive immune response. Searching for the molecular mechanisms underlying DC dysfunction, we found that canonical Wnt/ß-catenin and p38 MAPK pathways were activated in the DCs differentiated either in the presence of high glucose or of hyper-glycemic sera. Interestingly, the activation of these pathways and the DC immune dysfunction were partially counteracted by the anti-oxidant quercetin, a flavonoid already known to exert several beneficial effects in diabetes.

Hepatitis C virus present in the sera of infected patients interferes with the autophagic process of monocytes impairing their in-vitro differentiation into dendritic cells.

Autophagy has a pivotal role in the in-vitro monocyte differentiation into macrophages and dendritic cells (DCs), the most powerful antigen presenting cells (APC) with the unique capacity to initiate an adaptive immune response. Autophagy is also a mechanism by which these cells of innate immunity may degrade intracellular pathogens and mediate the antigen processing and presentation, essential to clear an infection. For these reasons, pathogens have learned how to manipulate autophagy for their own survival. In this study we found that hepatitis C virus (HCV), derived from sera of infected patients, blocked the autophagic process in differentiating monocytes, seen as LC3 II and p62 expression levels. The suppression of autophagy correlated with a reduction of cathepsins D, B and proteolytic activity, and resulted in impairment of monocyte differentiation into DCs, as indicated by the reduction of CD1a acquirement. These data suggest that the block of autophagy might be one of the underlying mechanisms of the HCV-mediated immune subversion that frequently leads to viral persistence and chronic hepatitis.

A functional interaction between TRPC/NCKX induced by DAG plays a role in determining calcium influx independently from PKC activation.

Ca(2+)influx might occur through K(+)-dependent Na(+)/Ca(2+) exchanger operating in reverse mode (rNCKX). In a cellular model different from platelets, an interaction between canonical transient receptor potential cation (TRPC) channels and NCX has been found. The aim of this study was to verify whether the TRPC/NCKX interaction operates in human platelets. Our results showed that the diacylglycerol (DAG) analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG) induced rNCKX-mediated Ca(2+) influx through TRPC-mediated Na(+) influx. DAG-induced activation of TRPC/NCKX occurs independently of protein kinase C (PKC) activation, as PKC inhibitor did not modify OAG-mediated Ca(2+) influx. Moreover, as both rNCKX and TRPC inhibitors reduced OAG-induced platelet aggregation which, conversely, was increased by flufenamic acid, known to develop TRPC activity, it could be suggested that the TRPC/NCKX interaction has a role in OAG-dependent platelet aggregation.

mTORC1/ERK1/2 Interplay Regulates Protein Synthesis and Survival in Acute Myeloid Leukemia Cell Lines.

mTOR is constitutively activated in acute myeloid leukemia (AML) cells, as indicated by the phosphorylation of its substrates, 4EBP1 and P70S6K. Here, we found that quercetin (Q) and rapamycin (Rap) inhibited P70S6K phosphorylation, partially dephosphorylated 4EBP1, and activated ERK1/2 in U937 and THP1, two leukemia cell lines. ERK1/2 inhibition by U0126 induced a stronger dephosphorylation of mTORC1 substrates and activated AKT. The concomitant inhibition of ERK1/2 and AKT further dephosphorylated 4EBP1 and further increased Q- or Rap-mediated cytotoxicity, compared to the single ERK1/2 or AKT inhibition in cells undergoing Q- or Rap-treatments. Moreover, quercetin or rapamycin reduced autophagy, particularly when used in combination with the ERK1/2 inhibitor, U0126. This effect was not dependent on TFEB localization in nuclei or cytoplasm or on the transcription of different autophagy genes, but did correlate with the reduction in protein translation due to a strong eIF2α-Ser51 phosphorylation. Thus, ERK1/2, by limiting 4EBP1 de-phosphorylation and eIF2α phosphorylation, behaves as a paladin of protein synthesis. Based on these findings, the combined inhibition of mTORC1, ERK1/2, and AKT should be considered in treatment of AML.

ATF6 prevents DNA damage and cell death in colon cancer cells undergoing ER stress.

Colon cancer represents one of the most common and aggressive cancers in its advanced state. Among the most innovative anti-cancer approaches, the manipulation of UPR is a promising one, effective also against cancers carrying dysfunctional p53. Interestingly, it is emerging that UPR cross-talks with DDR and that targeting the interplay between these two adaptive responses may be exploited to overcome the resistance to the single DDR- and UPR-targeting treatments. Previous studies have highlighted the role of IRE1 alpha and PERK UPR sensors on DDR, while the impact of ATF6 on this process remains under-investigated. This study shows for the first time that ATF6 sustains the expression level of BRCA-1 and protects colon cancer cells from the cytotoxic effect of ER stressors DPE and Thapsigargin. At molecular level, ATF6 activates mTOR to sustain the expression of HSP90, of which BRCA-1 is a client protein. Therefore, pharmacological or genetic inhibition of ATF6 promoted BRCA-1 degradation and increased DNA damage and cell death, particularly in combination with Adriamycin. All together this study suggests that targeting ATF6 may not only potentiate the cytotoxic effect of drugs triggering ER stress but may render colon cancer cells more sensitive to Adriamycin and possibly to other DNA damaging agents used to treat colon cancer.

Epstein-Barr virus lytic cycle activation alters proteasome subunit expression in Burkitt's lymphoma cells.

We have shown that Epstein-Barr virus (EBV) lytic cycle activation in Burkitt's lymphoma (BL) cells down-regulates chymotrypsin- and caspase-like activities of the proteasome. The aim of the present study was to evaluate whether EBV activation might also affect proteasome subunit composition. Our results indicate that, independently of the latency program established in the host cells, induction of the EBV lytic cycle reduces the expression of the proteasomal components ß5, ß1 and ß2i, whereas it increases that of ß2, ß1i, PA28α and PA28ß. The modulation of the composition and enzymatic activities of the proteolytic complex are indicative of a less efficient generation of viral immunoepitopes.

COX-1 sensitivity and thromboxane A2 production in type 1 and type 2 diabetic patients under chronic aspirin treatment.

AIMS: Although aspirin treatment is useful in reducing ischaemic events in diabetic patients, recent studies suggest that it is less effective when compared with non-diabetics (ND). We sought to evaluate COX-1 sensitivity and thromboxane A(2) (TxA(2)) production in type 1 (T1DM) and type 2 diabetic (T2DM) patients under chronic aspirin treatment, and also evaluate the association between thromboxane A(2) (TxA(2)) production and markers of inflammation and metabolic control, such as high-sensitivity C-reactive protein, fasting blood glucose, and haemoglobin A1c (HbA1c). METHODS AND RESULTS: Agonist-induced platelet aggregation (PA) and TxB(2), a stable metabolite of TxA(2), production, serum TxB(2), and platelet COX-1 and COX-2 expression were studied in T2DM patients, T1DM patients, and high-risk ND subjects, all receiving a low dose of aspirin. TxB(2) formation was studied in platelets treated in vitro with aspirin alone or with a COX-2 inhibitor (NS-398). PA, collagen-induced TxB(2) production, and serum TxB(2) were higher in T1DM and T2DM patients than in ND subjects. TxB(2) production was reduced in diabetic patients by in vitro treatment with aspirin. COX-2 was expressed in all diabetic patients but only in 46% of ND patients. In diabetic patients significant correlations were observed between TxB(2) production and both fasting plasma glucose and HbA1c. CONCLUSION: COX-1 sensitivity and TxB(2) production is similarly reduced in both T1DM and T2DM patients under chronic aspirin treatment. The association between TxB(2) production and either fasting plasma glucose and HbA1c levels suggests that in diabetic patients hyperglycaemia is a determinant of the reduced platelet sensitivity to aspirin.

Inhibition of p38 MAP kinase pathway induces apoptosis and prevents Epstein Barr virus reactivation in Raji cells exposed to lytic cycle inducing compounds.

BACKGROUND: EBV lytic cycle activators, such as phorbol esters, anti-immunoglobulin, transforming growth factor beta (TGFbeta), sodium butyrate, induce apoptosis in EBV-negative but not in EBV-positive Burkitt's lymphoma (BL) cells. To investigate the molecular mechanisms allowing EBV-infected cells to be protected, we examined the expression of viral and cellular antiapoptotic proteins as well as the activation of signal transduction pathways in BL-derived Raji cells exposed to lytic cycle inducing agents. RESULTS: Our data show that, following EBV activation, the latent membrane protein 1 (LMP1) and the cellular anti-apoptotic proteins MCL-1 and BCL-2 were quickly up-regulated and that Raji cells remained viable even when exposed simultaneously to P(BU)(2), sodium butyrate and TGFbeta. We report here that inhibition of p38 pathway, during EBV activation, led to a three fold increment of apoptosis and largely prevented lytic gene expression. CONCLUSION: These findings indicate that, during the switch from the latent to the lytic phase of EBV infection, p38 MAPK phosphorylation plays a key role both for protecting the host cells from apoptosis as well as for inducing viral reactivation. Because Raji cells are defective for late antigens expression, we hypothesize that the increment of LMP1 gene expression in the early phases of EBV lytic cycle might contribute to the survival of the EBV-positive cells.

Lack of biological relevance of platelet cyclooxygenase-2 dependent thromboxane A2 production.

INTRODUCTION: There is emerging evidence of a considerable variability of the impact of aspirin on clinical outcome and laboratory findings. Persistent TxA2 production seems to be the most likely reason. Aim of this study was to determine whether the mechanism responsible for TxA2 persistent production is, at least partially, dependent upon aspirin-insensitive platelet COX-2 enzymatic pathway. METHODS AND RESULTS: In 100 consecutive patients, under chronic aspirin anti-platelet treatment (100-160 mg/day) selected on the basis of detectable plasma salicylate levels, serum and Arachidonic Acid (AA)-induced platelet TxA2 production, immunoblot analysis of platelet COX-1/COX-2 expression and COX-2 activity were studied. Immunoblot revealed COX-2 expression in 46% patients, in an amount that was markedly lower than COX-1. In 10 COX-2 positive patients with TxA2 levels over the median, AA-induced TxA2 production performed in vitro in the presence of the COX-2 inhibitor CAY10404 and aspirin demonstrated that COX-2 dependent TxA2 production is less than 2%. CONCLUSION: Our data demonstrate that the inter-individual variability of platelet sensitivity to aspirin is due to a reduced efficacy of aspirin on platelet COX-1 despite ascertained patient compliance. We suggest that serum TxA2 assay might be performed in future clinical studies to improve our knowledge on the residual TxA2 production in aspirin-treated patients.

IRE1α deficiency promotes tumor cell death and eIF2α degradation through PERK dipendent autophagy.

Sensors of endoplasmic reticulum (ER) stress function in a co-ordinated manner. In the present study we investigated the relationship between IRE1α and PERK pathways and survival of ER stressed U937 cells and BC3 cells. To this end, we investigated the effects of a subcytotoxic concentration of Tunicamycin in IRE1α-proficient and in IRE1α-deficient cells, by pharmacological inhibition with 4µ8 C or down-regulation by specific siRNA. We show that either type of IRE1α deficiency affects eIF2α expression and causes cell death increase. GSK2606414, a PERK inhibitor, and PERK specific siRNA prevent eIF2α down-regulation and restore cell survival. Degradation of this protein is due to autophagy, as it is prevented by bafilomycin and not by proteasome inhibition. Furthermore, activation of the autophagy flux is PERK dependent. Also the Cathepsin B inhibitor CA074 prevents eIF2α from degradation and reduces cell death. Altogether, these results show that IRE1α deficiency in ER stressed cells leads to an unexpected decrease of eIF2α, an important molecule for protein translation, through PERK dependent autophagy. Thus, IRE1/XBP1 inhibitors may represent a feasible strategy for tumor therapy, while PERK inhibitors may vanish the goal.

Correction to: IRE1α deficiency promotes tumor cell death and eIF2α degradation through PERK-dependent autophagy.

[This corrects the article DOI: 10.1038/s41420-017-0002-9.].

EBV up-regulates PD-L1 on the surface of primary monocytes by increasing ROS and activating TLR signaling and STAT3.

Programmed death ligand 1 (PD-L1) (also called B7-H1) is a membrane immune-modulatory protein whose overexpression on the surface of tumor cells as well as APCs impairs T-cell-mediated killing. Viruses that establish chronic infections have developed a number of strategies to escape from immune recognition including the up-regulation of PD-L1. This study shows for the first time that the human oncovirus EBV infects human primary monocytes using HLA-DR and induced a strong up-regulation of PD-L1 expression on their surface. Searching for the underlying mechanism/s leading to this immune suppressive effect, we found that EBV activated TLR signaling, increased intracellular ROS, and phosphorylated STAT3. Targeting these molecules partially reverted PD-L1 up-regulation that correlated with an altered cytokine production and a reduction of monocyte cell survival, strongly impairing the antiviral immune response.

The interference of rosmarinic acid in the DNA fragmentation induced by osmotic shock.

The induction of cell death in human erythroleukemic cells (K562) by sorbitol shows the typical apoptotic changes in ultrastructural morphology, including blebbing, chromatin condensation and nuclear membrane breakdown. Using a cytofluorimetric approach, we found that sorbitol induced production of reactive oxygen species (ROS) followed by DNA fragmentation in leukemic cells. In this study, we investigated effect of curcumin and rosmarinic acid on cell viability in three different cell lines: erythroleukemia K562, papillary NPA, and anaplastic ARO thyroid cancers. Curcumin was able to induce apoptosis in a concentration- and time dependent manner in three cell lines, while rosmarinic acid was less effective on this process. To examine this possibility in cellular system, this study evaluated the capacities of both compounds acting as antioxidant inhibiting sorbitol-induced apoptosis. K562, NPA and ARO cells were pre-incubated with 25 microM rosmarinic acid to allow the uptake and then the cell lines were treated with 1 M sorbitol. Afterwards, the cells were subjected to agarose gel electrophoresis to assess the DNA fragmentation. In conclusion, the antioxidant activity of rosmarinic acid is able to inhibit sorbitol-induced apoptosis.

Inhibition of Epstein Barr Virus LMP1 gene expression in B lymphocytes by antisense oligonucleotides: uptake and efficacy of lipid-based and receptor-mediated delivery systems.

Epstein Barr Virus (EBV), is associated with an increasing number of lymphoid and epithelial malignancies. Among the genes expressed by EBV during latency, LMP1 plays a key role for growth transformation and immortalization of B lymphocytes. We have previously shown that antisense oligonucleotides (ONs) directed to LMP1 mRNA, effectively suppressed LMP1 gene expression and substantially reduced proliferation of the infected cells. The use of antisense phosphodiester oligonucleotides as therapeutic agents is limited by inefficient cellular uptake and intracellular transport to the target mRNA. We tested the ability of three cationic carriers internalized by different pathways, to increase the delivery of anti-LMP1-ON to their site of action in EBV-infected B lymphocytes. We report here that liposomes, dendrimers or transferrin-polylysine-conjugated ON were internalized by the cells at an extent several fold higher than that of the naked oligomers. However, only the delivery system exploiting the transferrin receptor pathway of internalization, was able to vectorize biologically active antisense LMP1-ON.

PYRROLO[1,2-b][1,2,5]BENZOTHIADIAZEPINES (PBTDs) induce apoptosis in K562 cells.

BACKGROUND: The objective of this study was to gain insight into the molecular mechanism of induced cell death (apoptosis) by PYRROLO [1,2-b][1,2,5]BENZOTHIADIAZEPINES (PBTDs) series compounds, using human (K562) cells as a model. METHODS: We focused our attention on some members of the PBTDs family to test their potential apoptotic activity in K562 cells. Important apoptotic activity was demonstrated, as evidenced by the concentration and percentage of cell death quantified by measuring PI-uptake by flow cytometry, and DNA fragmentation analyzed by agarose gel electrophoresis, generating a characteristic ladder pattern of discontinuous DNA fragments. The expression of Bcl-2 family was tested using western blotting and transfection method. RESULTS: PBTDs-mediated suppression of K562 cell proliferation was induced by apoptosis characterized by the appearance of DNA fragmentation and was associated with the poly(ADP-ribose)polymerase (PARP) cleavage. PBTD-1 and -3 treatment resulted in caspase-3 activation through down-regulation of Bcl-2 and up-regulation of Bax. Furthermore, we used K562/vector and K562/bcl-2 cells, which were generated by transfection of the cDNA of the Bcl-2 gene. As compared with K562/vector, K562/Bcl-2 cells exhibited a 4-fold greater expression of Bcl-2. Treatment with 10 muM PBTD-1 and -3 for 24 h produced morphological features of apoptosis and DNA fragmentation in K562/vector cells, respectively. In contrast, PBTD-1 and -3-induced caspase-3 activation and apoptosis were inhibited in K562/Bcl-2. Furthermore, Bcl-2 overexpressing cells exhibited less cytocrome c release during PBTDs-induced apoptosis. CONCLUSION: These results indicate that PBTDs effectively induce apoptosis of K562 leukemia cells through the activation of caspase cascades. In addition, these findings indicate that Bcl-2 inhibits PBTD-1 and -3 induced-apoptosis via a mechanism that interferes with cytocrome c release, and the activity of caspase-3, which is involved in the execution of apoptosis.

Reactive oxygen and nitrogen species are involved in sorbitol-induced apoptosis of human erithroleukaemia cells K562.

In this study, we found that production of both reactive oxygen (ROS) and nitrogen (RNS) species is a very early event related to treatment with hyperosmotic concentration of sorbitol. The production of nitric oxide (NO) was paralleled by the increase of the mRNA and protein level of the inducible form of the nitric oxide synthase (iNOS). ROS and RNS enhancement, process concomitant to the failure of mitochondrial trans-membrane potential (DeltaPsi), was necessary for the induction of apoptosis as demonstrated by the protection against sorbitol-mediated toxicity observed after treatment with ROS scavengers or NOS inhibitors. The synergistic action of ROS and RNS was finally demonstrated by pre-treatment with rosmarinic acid that, by powerfully buffering both these species, prevents impairment of DeltaPsi and cell death. Overall results suggest that the occurrence of apoptosis upon sorbitol treatment is an event mediated by oxidative/nitrosative stress rather than a canonical hyperosmotic shock.

Docosahexaenoic acid (DHA) promotes immunogenic apoptosis in human multiple myeloma cells, induces autophagy and inhibits STAT3 in both tumor and dendritic cells.

Docosahexaenoic acid (DHA), a ω-3 polyunsaturated fatty acid found in fish oil, is a multi-target agent and exerts anti-inflammatory and anticancer activities alone or in combination with chemotherapies. Combinatorial anticancer therapies, which induce immunogenic apoptosis, autophagy and STAT3 inhibition have been proposed for long-term therapeutic success. Here, we found that DHA promoted immunogenic apoptosis in multiple myeloma (MM) cells, with no toxicity on PBMCs and DCs. Immunogenic apoptosis was shown by the emission of specific DAMPs (CRT, HSP90, HMGB1) by apoptotic MM cells and the activation of their pro-apoptotic autophagy. Moreover, immunogenic apoptosis was directly shown by the activation of DCs by DHA-induced apoptotic MM cells. Furthermore, we provided the first evidence that DHA activated autophagy in PBMCs and DCs, thus potentially acting as immune stimulator and enhancing processing and presentation of tumor antigens by DCs. Finally, we found that DHA inhibited STAT3 in MM cells. STAT3 pathway, essential for MM survival, contributed to cancer cell apoptosis by DHA. We also found that DHA inhibited STAT3 in blood immune cells and counteracted STAT3 activation by tumor cell-released factors in PBMCs and DCs, suggesting the potential enhancement of the anti-tumor function of multiple immune cells and, in particular, that of DCs.

Increased T-helper interferon-gamma-secreting cells in obese children.

OBJECTIVE: Leptin, an adipocyte-secreted hormone, has emerged as a potential candidate for the link between obesity and the proinflammatory state. Specifically, leptin modulates T-helper (Th) cells toward a Th1 phenotype, with the secretion of proinflammatory cytokines. The aim of this study was to evaluate the Th1/Th2 balance in obese children and its relation with hormonal and metabolic features. STUDY DESIGN: In 50 obese children and 20 control children, we measured the CD4-positive Th cells that secrete interferon (IFN)-gamma or interleukin (IL)-2 (taken as an index of Th1 cells), and IL-4 (taken as an index of Th2 cells) as well as serum glucose, insulin, insulin resistance (IR) index (as homeostasis model assessment model (HOMA)), lipid profile, aminotransferases, leptin and ghrelin. Obese children also underwent dual energy X-ray absorptiometry scan measurements, and liver ultrasound scanning. RESULTS: Geometric mean percentages of IL-2- and IL-4-CD4 secreting cells in obese children were not significantly different from those found in control children. However, the geometric mean percentage of CD4-positive T cells secreting IFN-gamma was significantly higher in the obese than in the control (P < 0.0001, t-test) group. Within the entire group of study children, the percentage of IFN-gamma-positive cells was positively associated with leptin (P = 0.002), insulin (P < 0.00 005), and HOMA-IR values (P < 0.00 005). However, when these associations were restricted to the group of obese subjects, insulin and HOMA-IR values, but not leptin, retained statistical significance. Yet, in the obese group, the percentage of IFN-gamma-positive cells was associated with nonalcoholic steatohepatitis (NASH) (P = 0.001), but not with body mass index-standard deviation score and total body fat mass. CONCLUSIONS: In obese children, a shift to Th1-cytokine profile dominated by the production of IFN-gamma is related to insulin resistance as well as to NASH independently of anthropometric features and other metabolic characteristics. The prevalent Th1 pattern of secreted cytokines may be regarded as a mechanism contributing to inflammation in obesity.

[Biomonitoring of nurses occupationally exposed to antineoplastic drugs: the IMEPA Project]. / Identificazione di marcatori specifici di esposizione professionale a farmaci antiblastici usati in polichemioterapia: Progetto IMEPA.

OBJECTIVE: To develop a multiple-endpoint monitoring system in order to assess and minimize long term risks in hospital nurses exposed to antiblastic drugs. DESIGN: Molecular epidemiology study. SETTING: S. Orsola-Malpighi Hospital in Bologna, Italy: nurses exposed to antiblastic drugs. PARTICIPANTS: 50 exposed subjects (8 males and 42 females) and 50 unexposed individuals (8 males and 42 females) matched for age and smoking habits. MAIN OUTCOME MEASURES: Urinary markers of exposure, Heat Shock Proteins (HSPs) 27, 70, 90, 110, immunologic biomarkers in peripheral blood lymphocytes: apoptosis, cell-cycle analysis G1-S-G, typization of Natural Killer cells (NK) and receptors micronuclei; frequency in peripheral blood lymphocytes and in exfoliated buccal mucosa cells; activation ofspecific oncogenes (bax, bcl2). RESULTS: 19/50 subjects showed urinary antiblastic drug levels (3 subjects MTX, 11 subjects CP, 5 subjects MTX and CP). No statistically significant differences were observed in all the considered biomarkers between the exposed and control groups. CONCLUSION: This biomonitoring study doesn't evidence any early significant effect associated to the exposure to antiblastic drugs.

Quercetin affects Hsp70/IRE1α mediated protection from death induced by endoplasmic reticulum stress.

Relative to their normal counterparts, tumor cells generally exhibit a greater "stress phenotype" and express heat shock proteins (Hsp) that represent candidate targets for anticancer therapy. Here we investigated the role of Hsp70 in survival induced by endoplasmic reticulum (ER) stressors in human leukemia U937 cells. Quercetin, a major dietary flavonoid, or specific silencing affected the expression level of Hsp70 and did not allow the upregulation of inositol-requiring kinase 1α (IRE1α), the prototype ER stress sensor regulating the unfolded protein response (UPR), that protects the cells against the stress of misfolded proteins in the ER. The reduction of Hsp70 prevented the upregulation of immunoglobulin heavy-chain binding protein (BiP), but not of CCAAT/enhancer-binding protein-homologous protein (CHOP), and induced apoptosis. Also specific silencing of IRE1α or inhibition of its endoribonuclease activity by 4µ8c hampered the upregulation of BiP, but not of CHOP, and induced apoptosis. These results suggest that drugs affecting the Hsp70-IRE1α axis, like quercetin, or affecting directly IRE1α may represent an effective adjuvant antileukemia therapy.