Dendritic cell surface calreticulin is a receptor for NY-ESO-1: direct interactions between tumor-associated antigen and the innate immune system

Rheumatoid arthritis and the intestinal microbiome: probiotics as a potential therapy

Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by swollen joints, discomfort, stiffness, osteoporosis, and reduced functionality. Genetics, smoking, dust inhalation, high BMI, and hormonal and gut microbiota dysbiosis are all likely causes of the onset or development of RA, but the underlying mechanism remains unknown. Compared to healthy controls, patients with RA have a significantly different composition of gut microbiota. It is well known that the human gut microbiota plays a key role in the initiation, maintenance, and operation of the host immune system. Gut microbiota dysbiosis has local or systematic adverse effects on the host immune system, resulting in host susceptibility to various diseases, including RA. Studies on the intestinal microbiota modulation and immunomodulatory properties of probiotics have been reported, in order to identify their potential possibility in prevention and disease activity control of RA. This review summarized current studies on the role and potential mechanisms of gut microbiota in the development and progression of RA, as well as the preventative and therapeutic effects and potential mechanisms of probiotics on RA. Additionally, we proposed the challenges and difficulties in the application of probiotics in RA, providing the direction for the research and application of probiotics in the prevention of RA.

Thymoquinone, a Novel Multi-Strike Inhibitor of Pro-Tumorigenic Breast Cancer (BC) Markers: CALR, NLRP3 Pathway and sPD-L1 in PBMCs of HR+ and TNBC Patients

Breast cancer (BC) is not only a mass of malignant cells but also a systemic inflammatory disease. BC pro-tumorigenic inflammation has been shown to promote immune evasion and provoke BC progression. The NOD-like receptor (NLR) family pyrin domain-containing protein 3 (NLRP3) inflammasome is activated when pattern recognition receptors (PRRs) sense danger signals such as calreticulin (CALR) from damaged/dying cells, leading to the secretion of interleukin-1β (IL-1β). CALR is a novel BC biological marker, and its high levels are associated with advanced tumors. NLRP3 expression is strongly correlated with an elevated proliferative index Ki67, BC progression, metastasis, and recurrence in patients with hormone receptor-positive (HR+) and triple-negative BC (TNBC). Tumor-associated macrophages (TAMs) secrete high levels of IL-1β promoting endocrine resistance in HR+ BC. Recently, an immunosuppressive soluble form of programmed death ligand 1 (sPD-L1) has been identified as a novel prognostic biomarker in triple-negative breast cancer (TNBC) patients. Interestingly, IL-1β induces sPD-L1 release. BC Patients with elevated IL-1β and sPD-L1 levels show significantly short progression-free survival. For the first time, this study aims to investigate the inhibitory impact of thymoquinone (TQ) on CALR, the NLRP3 pathway and sPD-L1 in HR+ and TNBC. Blood samples were collected from 45 patients with BC. The effect of differing TQ concentrations for different durations on the expression of CALR, NLRP3 complex components and IL-1β as well as the protein levels of sPD-L1 and IL-1β were investigated in the peripheral blood mononuclear cells (PBMCs) and TAMs of TNBC and HR+ BC patients, respectively. The findings showed that TQ significantly downregulated the expression of CALR, NLRP3 components and IL-1β together with the protein levels of secreted IL-1β and sPD-L1. The current findings demonstrated novel immunomodulatory effects of TQ, highlighting its potential role not only as an excellent adjuvant but also as a possible immunotherapeutic agent in HR+ and TNBC patients.

Photon- and Proton-Mediated Biological Effects: What Has Been Learned?

The current understanding of the effects of radiation is gradually becoming broader. However, it still remains unclear why some patients respond to radiation with a pronounced positive response, while in some cases the disease progresses. This is the motivation for studying the effects of radiation therapy not only on tumor cells, but also on the tumor microenvironment, as well as studying the systemic effects of radiation. In this framework, we review the biological effects of two types of radiotherapy: photon and proton irradiations. Photon therapy is a commonly used type of radiation therapy due to its wide availability and long-term history, with understandable and predictable outcomes. Proton therapy is an emerging technology, already regarded as the method of choice for many cancers in adults and children, both dosimetrically and biologically. This review, written after the analysis of more than 100 relevant literary sources, describes the local effects of photon and proton therapy and shows the mechanisms of tumor cell damage, interaction with tumor microenvironment cells and effects on angiogenesis. After systematic analysis of the literature, we can conclude that proton therapy has potentially favorable toxicological profiles compared to photon irradiation, explained mainly by physical but also biological properties of protons. Despite the fact that radiobiological effects of protons and photons are generally similar, protons inflict reduced damage to healthy tissues surrounding the tumor and hence promote fewer adverse events, not only local, but also systemic.

Restoring the Immunity in the Tumor Microenvironment: Insights into Immunogenic Cell Death in Onco-Therapies

Immunogenic cell death (ICD) elicited by cancer therapy reshapes the tumor immune microenvironment. A long-term adaptative immune response can be initiated by modulating cell death by therapeutic approaches. Here, the major hallmarks of ICD, endoplasmic reticulum (ER) stress, and damage-associated molecular patterns (DAMPs) are correlated with ICD inducers used in clinical practice to enhance antitumoral activity by suppressing tumor immune evasion. Approaches to monitoring the ICD triggered by antitumoral therapeutics in the tumor microenvironment (TME) and novel perspective in this immune system strategy are also reviewed to give an overview of the relevance of ICD in cancer treatment.

Immunogenicity and cytotoxicity of a platinum(IV) complex derived from capsaicin

Platinum-based anticancer drugs constitute the cornerstone of chemotherapy for various cancers. Although cytotoxic agents are considered to have immunosuppressive effects, increasing evidence suggests that some cytotoxic compounds can effectively stimulate the antitumor immune response by inducing a special type of apoptosis called immunogenic cell death (ICD). A platinum(iv) complex (DCP) modified with the derivative of synthetic capsaicin (nonivamide) was designed to elicit ICD. The complex exhibited high cytotoxicity against a panel of human cancer cell lines including pancreas (PANC-1), breast (MCF-7), and liver (HepG2) cancer cells, and osteosarcoma (MG-63) cells. In addition to causing DNA damage, DCP also triggered the translocation of calreticulin (CRT) as well as the release of ATP and HMGB1 protein in PANC-1 cells, thus manifesting an efficient ICD-inducing effect on cancer cells. Furthermore, the DCP-treated PANC-1 cell-conditioned culture medium promoted the release of IFN-γ and TNF-α to induce the immune response of human peripheral blood mononuclear cells, thereby increasing their cytotoxicity to cancer cells. Concurrently, the phagocytosis of PANC-1 cells by macrophages was also augmented by DCP. The results demonstrate that DCP is an effective inducer of ICD and a potential agent for chemoimmunotherapy of cancers.

Calreticulin Blockade Attenuates Murine Acute Lung Injury by Inducing Polarization of M2 Subtype Macrophages

Calreticulin (CALR) has anti-tumor effects by increasing dendritic cell maturation and tumor antigen presentation. However, whether CALR affects macrophages and modulates progression of acute respiratory distress syndrome/acute lung injury (ARDS/ALI) remains unknown. In this study, we discovered that CALR protein was highly expressed in the mice with LPS-induced ALI and CALR expression level was positively correlated to the severity of ALI. Commercial anti-CALR antibody (aCALR) can neutralize recombinant CALR (rCALR) and suppress the expression of TNF-alpha and IL-6 in the rCALR-treated macrophages. Blocking CALR activity by intraperitoneal (i.p.) administration of aCALR significantly suppressed ALI, accompanied with lower total cell counts, neutrophil and T cell infiltration in bronchoalveolar lavage (BAL) and lung tissues. The expression of CXCL15, IL-6, IL-1beta, TNF-alpha, and CALR were significantly reduced, in association with more polarization of Siglec F+CD206+M2 subtype macrophages in the aCALR-treated mice. Pre-depletion of circulating monocytes did not abolish the aCALR-mediated suppression of ALI. Further analysis in bone marrow-derived macrophages (BMDMs) showed that aCALR suppressed the expression of CD80, IL-6, IL-1beta, IL-18, NLRP3, and p-p38 MAPK; but enhanced the expression of CD206 and IL-10. In addition, we observed more expression and phosphorylation of STAT6 in the aCALR-treated BMDM. Lack of STAT6 resulted in comparable and slightly higher expression of CALR, TNF-alpha and IL-6 in the aCALR-treated STAT6-/- BMDMs than the untreated cells. Therefore, we conclude that CALR is a novel biomarker in the evaluation of ALI. Blocking CALR activity by aCALR effectively suppressed ALI independent of circulating monocytes. Siglec F+CD206+M2 subtype macrophages and p38 MAPK/STAT6 signaling pathway played important role in the immune regulation of aCALR. Blocking CALR activity is a promising therapeutic approach in the treatment of ARDS/ALI.

Immunogenic cell death due to a new photodynamic therapy (PDT) with glycoconjugated chlorin (G-chlorin)

Both the pre-apoptotic exposure to calreticulin (CRT) and the post-apoptotic release of high-mobility group box 1 protein (HMGB1) are required for immunogenic cell death. Photodynamic therapy (PDT) uses non-toxic photosensitizers and visible light at a specific wavelength in combination with oxygen to produce cytotoxic reactive oxygen species that kill malignant cells by apoptosis and/or necrosis, shut down the tumor microvasculature, and stimulate the host immune system. We have previously shown that glycoconjugated chlorin (G-chlorin) has superior cancer cell selectivity and effectively suppresses the growth of xenograft tumors. In the present study, we evaluated the immunogenicity of PDT with G-chlorin treatment in colon cancer cells. PDT with G-chlorin suppressed CT26 (mouse colon cancer cells) tumor growth considerably more efficiently in immunocompetent mice (wild-type mice, allograft model) than in immune-deficient mice (nude mice, xenograft model), although control treatments were not different between the two. This treatment also induced CRT translocation and HMGB1 release in cells, as shown by western blot and immunofluorescence staining. To evaluate the use of PDT-treated cells as a tumor vaccine, we employed a syngeneic mouse tumor model (allograft model). Mice inoculated with PDT-treated CT26 cells were significantly protected against a subsequent challenge with live CT26 cells, and this protection was inhibited by siRNA for CRT or HMGB1. In conclusion, PDT with G-chlorin treatment induced immunogenic cell death in a mouse model, where the immunogenicity of this treatment was directed by CRT expression and HMGB1 release.

Relevance of the chaperone-like protein calreticulin for the biological behavior and clinical outcome of cancer

The death of cancer cells can be categorized as either immunogenic (ICD) or nonimmunogenic, depending on the initiating stimulus. The immunogenic processes of immunogenic cell death are mainly mediated by damage-associated molecular patterns (DAMPs), which include surface exposure of calreticulin (CRT), secretion of adenosine triphosphate (ATP), release of non-histone chromatin protein high-mobility group box 1 (HMGB1) and the production of type I interferons (IFNs). DAMPs are recognized by various receptors that are expressed by antigen-presenting cells (APCs) and potentiate the presentation of tumor antigens to T lymphocytes. Accumulating evidence indicates that CRT exposure constitutes one of the major checkpoints, that determines the immunogenicity of cell death both in vitro and in vivo in mouse models. Moreover, recent studies have identified CRT expression on tumor cells not only as a marker of ICD and active anti-tumor immune reactions but also as a major predictor of a better prognosis in various cancers. Here, we discuss the recent information on the CRT capacity to activate anticancer immune response as well as its prognostic and predictive role for the clinical outcome in cancer patients.

Calreticulin is an effective immunologic adjuvant to tumor-associated antigens

As a key molecule involved in cell recognition, calreticulin (CRT) may be expressed on the surface of (pre-) apoptotic cells and provide the signal that is recognized by dendritic cells (DCs) or other antigen presenting cells (APCs), which results in phagocytosis. Within the APCs, tumor-associated antigens (TAAs) may be subsequently presented to T lymphocytes, which triggers a specific antitumor immune response. It has been hypothesized that CRT is able to act as the immunologic adjuvant and translocate itself and TAAs to the cell surface and induce a specific antitumor immune response. In the present study, CRT was demonstrated to translocate itself and mucin 1 (MUC1), a breast cancer antigen, to the surface of 4T1 cells and the MUC1-CRT-coated cells were able to induce apoptosis in a time-dependent manner. When DCs were infected with adenovirus containing MUC1-CRT, an increase in T cell proliferation and cytokine production was exhibited. These results suggest that CRT may act as an immunologic adjuvant with MUC1 and induce a strong immune response.

A Pilot Study of Stereotactic Body Radiation Therapy Combined with Cytoreductive Nephrectomy for Metastatic Renal Cell Carcinoma

Purpose: While stereotactic body radiotherapy (SBRT) can reduce tumor volumes in patients with metastatic renal cell carcinoma (mRCC), little is known regarding the immunomodulatory effects of high-dose radiation in the tumor microenvironment. The main objectives of this pilot study were to assess the safety and feasibility of nephrectomy following SBRT treatment of patients with mRCC and analyze the immunological impact of high-dose radiation.Experimental Design: Human RCC cell lines were irradiated and evaluated for immunomodulation. In a single-arm feasibility study, patients with mRCC were treated with 15 Gray SBRT at the primary lesion in a single fraction followed 4 weeks later by cytoreductive nephrectomy. RCC specimens were analyzed for tumor-associated antigen (TAA) expression and T-cell infiltration. The trial has reached accrual (ClinicalTrials.gov identifier: NCT01892930).Results: RCC cells treated in vitro with radiation had increased TAA expression compared with untreated tumor cells. Fourteen patients received SBRT followed by surgery, and treatment was well-tolerated. SBRT-treated tumors had increased expression of the immunomodulatory molecule calreticulin and TAA (CA9, 5T4, NY-ESO-1, and MUC-1). Ki67⁺ -proliferating CD8⁺ T cells and FOXP3⁺ cells were increased in SBRT-treated patient specimens in tumors and at the tumor-stromal interface compared with archived patient specimens.Conclusions: It is feasible to perform nephrectomy following SBRT with acceptable toxicity. Following SBRT, patient RCC tumors have increased expression of calreticulin, TAA, as well as a higher percentage of proliferating T cells compared with archived RCC tumors. Collectively, these studies provide evidence of immunomodulation following SBRT in mRCC. Clin Cancer Res; 23(17); 5055-65. ©2017 AACR.

Damage-associated molecular patterns in cancer: a double-edged sword

Damage-associated molecular patterns (DAMPs) are released in response to cell death and stress, and are potent triggers of sterile inflammation. Recent evidence suggests that DAMPs may also have a key role in the development of cancer as well as in the host response to cytotoxic anti-tumor therapy. As such, DAMPs may exert protective functions by alerting the immune system to the presence of dying tumor cells, thereby triggering immunogenic tumor cell death. On the other hand, cell death and release of DAMPs may also trigger chronic inflammation and thereby promote the development or progression of tumors. Here, we will review the contribution of candidate DAMPs and their receptors and discuss the evidence for DAMPs as tumor-promoting and anti-tumor effectors as well as unsolved questions such as DAMP release from non-tumor cells as well as the existence of tumor-specific DAMPs.

Prognostic and Predictive Value of DAMPs and DAMP-Associated Processes in Cancer

It is now clear that human neoplasms form, progress, and respond to therapy in the context of an intimate crosstalk with the host immune system. In particular, accumulating evidence demonstrates that the efficacy of most, if not all, chemo- and radiotherapeutic agents commonly employed in the clinic critically depends on the (re)activation of tumor-targeting immune responses. One of the mechanisms whereby conventional chemotherapeutics, targeted anticancer agents, and radiotherapy can provoke a therapeutically relevant, adaptive immune response against malignant cells is commonly known as “immunogenic cell death.” Importantly, dying cancer cells are perceived as immunogenic only when they emit a set of immunostimulatory signals upon the activation of intracellular stress response pathways. The emission of these signals, which are generally referred to as “damage-associated molecular patterns” (DAMPs), may therefore predict whether patients will respond to chemotherapy or not, at least in some settings. Here, we review clinical data indicating that DAMPs and DAMP-associated stress responses might have prognostic or predictive value for cancer patients.

Ikaros deficiency in host hematopoietic cells separates GVL from GVHD after experimental allogeneic hematopoietic cell transplantation

The graft-versus-leukemia (GVL) effect following allogeneic hematopoietic stem cell transplantation (allo-HCT) is critical for its curative potential. Hwever, GVL is tightly linked to graft-versus-host disease (GVHD). Among hematological malignancies, acute lymphoblastic leukemia (ALL) is the most resistant to GVL, although the reasons for this remain poorly understood. Clinical studies have identified alterations in Ikaros (Ik) transcription factor as the major marker associated with poor outcomes in ALL. We have shown that the absence of Ik in professional host-derived hematopoietic antigen-presenting cells (APCs) exacerbates GVHD. However, whether Ik expression plays a role in resistance to GVL is not known. In this study we used multiple clinically relevant murine models of allo-HCT to explore whether Ik expression in hematopoietic APCs and/or leukemic cells is critical for increasing resistance to GVL and thus inducing relapse. We found that Ik deficiency in host APCs failed to enhance GVL despite increased GVHD severity. Mechanistic studies with bone marrow (BM) chimeras and tetramer analyses demonstrated reduced tumor-specific immunodominant (gag+) antigen responses in the [B6Ik^-/-→B6] group. Loss of GVL was observed when both the leukemia cells and the host APCs were deficient in Ik. We found that calreticulin (CRT) expression in host antigen-presenting dendritic cells (DCs) of Ik^-/- animals was significantly lower than in wild-type animals. Rescuing CRT expression in Ik^-/- DCs improved leukemic-specific cytotoxic T cell function. Together, our data demonstrate that the absence of Ikaros in host hematopoietic cells promotes resistance to GVL despite increasing GVHD and thus provides a potential mechanism for the poor outcome of Ik^-/- ALL patients.

Bee Venom Phospholipase A2, a Good "Chauffeur" for Delivering Tumor Antigen to the MHC I and MHC II Peptide-Loading Compartments of the Dendritic Cells: The Case of NY-ESO-1

Bee venom phospholipase A2 (bvPLA2) is a small, 15kDa enzyme which hydrolyses many phospholipids through interfacial binding. The mutated bvPLA2H34Q (bvPLA2m), in which histidine-34 is replaced by glutamine, is not catalytically active. This protein has been shown to be a suitable membrane anchor and has been suggested as a suitable tumor-antigen vector for the development of novel dendritic cell-based vaccines. To confirm this feature, in this study the fusion protein PNY, composed of NY-ESO-1(NY(s)) fused to the C-terminus of bvPLA2m, was engineered. bvPLA2m enhanced the binding of NY(s) to the membrane of human monocyte-derived dendritic cells (DCs) and, once taken up by the cells, the antigen fused to the vector was directed to both MHC I and MHC II peptide-loading compartments. bvPLA2m was shown to increase the cross-presentation of the NY(s)-derived, restricted HLA-A*02 peptide, NY-ESO-1157-165(NY157-165), at the T1 cell surface. DCs loaded with the fusion protein induced cross-priming of NY(s)-specific CD8 + T-cells with greater efficiency than DCs loaded with NY(s). Sixty-five percent of these NY(s)-specific CD8+ T-cell lines could also be activated with the DCs pulsed with the peptide, NY157-165. Of these CD8+ T-cell lines, two were able to recognize the human melanoma cell line, SK-MEL-37, in a context of HLA-A*02. Only a small number of bvPLA2m CD8+ T-cell lines were induced, indicating the low immunogenicity of the protein. It was concluded that bvPLA2m can be used as a membrane-binding vector to promote MHC class II peptide presentation and MHC class I peptide cross-presentation. Such a system can, therefore, be tested for the preparation of cell-based vaccines.

Immunogenic cell death: can it be exploited in PhotoDynamic Therapy for cancer?

Immunogenic Cell Death (ICD) could represent the keystone in cancer management since tumor cell death induction is crucial as well as the control of cancer cells revival after neoplastic treatment. In this context, the immune system plays a fundamental role. The concept of Damage-Associated Molecular Patterns (DAMPs) has been proposed to explain the immunogenic potential of stressed or dying/dead cells. ICD relies on DAMPs released by or exposed on dying cells. Once released, DAMPs are sensed by immune cells, in particular Dendritic Cells (DCs), acting as activators of Antigen-Presenting Cells (APCs), that in turn stimulate both innate and adaptive immunity. On the other hand, by exposing DAMPs, dying cancer cells change their surface composition, recently indicated as vital for the stimulation of the host immune system and the control of residual ill cells. It is well established that PhotoDynamic Therapy (PDT) for cancer treatment ignites the immune system to elicit a specific antitumor immunity, probably linked to its ability in inducing exposure/release of certain DAMPs, as recently suggested. In the present paper, we discuss the DAMPs associated with PDT and their role in the crossroad between cancer cell death and immunogenicity in PDT.

Cancer and innate immune system interactions: translational potentials for cancer immunotherapy

Passive immunotherapy, including adoptive T-cell therapy and antibody therapy, has shown encouraging results in cancer treatment lately. However, active immunotherapy of solid cancers remains an elusive goal. It is now known that the human innate immune system recognizes pathogen-associated molecular patterns conserved among microbes or damage-associated molecular patterns released from tissue injuries to initiate adaptive immune responses during infection and tissue inflammation, respectively. In contrast, how the innate immune system recognizes endogenously arising cancer remains poorly understood at the molecular level, which poses a significant roadblock to the development of active cancer immunotherapy. We hereby review the current knowledge of how solid cancers directly and indirectly interact with cells of the human innate immune system, with a focus on the potential effect of such interactions to the resultant adaptive immune responses against cancer. We believe that understanding cancer and innate immune system interactions may allow us to better manipulate the adaptive immune system at the molecular level to develop effective active immunotherapy against cancer. Current and future perspectives in clinical development that exploits these molecular interactions are discussed.

Modulation of cellular immunity by antibodies against calreticulin

Although caltreticulin (CRT) is mainly a residential ER protein, it is also expressed on the membrane surface of various types of cells exhibiting multiple functions. We report here that intraperitoneal administration of a soluble recombinant CRT fragment (rCRT/39-272) led to a substantial decrease in delayed type hypersensitivity (DTH) responses in BALB/c mice and EAE in C57BL/6 mice. In the recall response against keyhole limpet hemocyanin (KLH) in vitro, draining lymph node cells from the rCRT/39-272-treated mice produced less IFN-γ but more IL-4 as compared with the cells from the control group. The immunomodulating effect of intraperitoneally administered rCRT/39-272 was attributed to anti-CRT Abs thereby induced, because, in passive transfer experiments, the CRT-specific antiserum could suppress DTH in BALB/c mice. B-cell-deficient μMT mice were not susceptible to rCRT/39-272-mediated DTH suppression. Furthermore, CRT appears on the surface of murine T cells soon after activation and remains detectable (at relatively low level) by flow cytometry for approximately 5 days in vitro. Anti-CRT Abs were able to inhibit AKT phosphorylation, proliferation, and cytokine production by activated murine T cells. We propose that cell surface CRT could play a role in the function of effector T cells and may be considered a target for immunological manipulation.

Calreticulin as a potential diagnostic biomarker for lung cancer

Calreticulin (CRT) is an endoplasmic reticulum luminal Ca(2+)-binding chaperone protein. By immunizing mice with recombinant fragment (rCRT/39-272), six clones of monoclonal antibodies (mAbs) were generated and characterized. Based on these mAbs, a microplate chemiluminescent enzyme immunoassay (CLEIA) system with a measured limit of detection of 0.09 ng/ml was developed. Using this CLEIA system, it was found that soluble CRT (sCRT) level in serum samples from 58 lung cancer patients was significantly higher than that from 40 healthy individuals (only 9 were detectable, P < 0.0001). Among them, serum sCRT in the small cell lung cancer was lower than that in adenocarcinoma (P = 0.0085), while both were lower than that in the squamous cell carcinoma (P = 0.013, P = 0.0012, respectively). Moreover, it was found that sCRT in sera from the patients after chemotherapy was higher than that from the patients without chemotherapy (P = 0.042). Further study by immunohistochemistry showed that CRT was also highly expressed in the cytoplasm and on the membrane of the lung cancer cells, while there was a trace amount of CRT expression in normal lung cells. Correspondingly, the expression level of CRT on lung cancer cell membrane was associated with the tumor pathological grade. This study demonstrates that sCRT concentration in sera of lung cancer patients is higher than that in sera of healthy individuals, and CRT expression level on lung cancer cell membrane is associated with tumor pathological classification and grade. These findings suggest that CRT may be used as a biomarker in lung cancer prediction and diagnosis.

Decitabine immunosensitizes human gliomas to NY-ESO-1 specific T lymphocyte targeting through the Fas/Fas ligand pathway

Background

The lack of effective treatments for gliomas makes them a significant health problem and highlights the need for the development of novel and innovative treatment approaches. Immunotherapy is an appealing strategy because of the potential ability for immune cells to traffic to and destroy infiltrating tumor cells. However, the absence of well-characterized, highly immunogenic tumor-rejection antigens (TRA) in gliomas has limited the implementation of targeted immune-based therapies.

Methods

We hypothesized that treatment with the demethylating agent, decitabine, would upregulate the expression of TRA on tumor cells, thereby facilitating enhanced surveillance by TRA-specific T cells.

Results and Discussion

Treatment of human glioma cells with decitabine increased the expression of NY-ESO-1 and other well characterized cancer testes antigens. The upregulation of NY-ESO-1 made these tumors susceptible to NY-ESO-1-specific T-cell recognition and lysis. Interestingly, decitabine treatment of T98 glioma cells also sensitized them to Fas-dependent apoptosis with an agonistic antibody, while a Fas blocking antibody could largely prevent the enhanced functional recognition by NY-ESO-1 specific T cells. Thus, decitabine treatment transformed a non-immunogenic glioma cell into an immunogenic target that was efficiently recognized by NY-ESO-1--specific T cells.

Conclusions

Such data supports the hypothesis that agents which alter epigenetic cellular processes may "immunosensitize" tumor cells to tumor-specific T cell-mediated lysis.

Integrated NY-ESO-1 antibody and CD8+ T-cell responses correlate with clinical benefit in advanced melanoma patients treated with ipilimumab

Ipilimumab, a monoclonal antibody against cytotoxic T lymphocyte antigen 4 (CTLA-4), has been shown to improve survival in patients with advanced metastatic melanoma. It also enhances immunity to NY-ESO-1, a cancer/testis antigen expressed in a subset of patients with melanoma. To characterize the association between immune response and clinical outcome, we first analyzed NY-ESO-1 serum antibody by ELISA in 144 ipilimumab-treated patients with melanoma and found 22 of 140 (16%) seropositive at baseline and 31 of 144 (22%) seropositive following treatment. These NY-ESO-1-seropositive patients had a greater likelihood of experiencing clinical benefit 24 wk after ipilimumab treatment than NY-ESO-1-seronegative patients (P = 0.02, relative risk = 1.8, two-tailed Fisher test). To understand why some patients with NY-ESO-1 antibody failed to experience clinical benefit, we analyzed NY-ESO-1-specific CD4(+) and CD8(+) T-cell responses by intracellular multicytokine staining in 20 NY-ESO-1-seropositive patients and found a surprising dissociation between NY-ESO-1 antibody and CD8 responses in some patients. NY-ESO-1-seropositive patients with associated CD8(+) T cells experienced more frequent clinical benefit (10 of 13; 77%) than those with undetectable CD8(+) T-cell response (one of seven; 14%; P = 0.02; relative risk = 5.4, two-tailed Fisher test), as well as a significant survival advantage (P = 0.01; hazard ratio = 0.2, time-dependent Cox model). Together, our data suggest that integrated NY-ESO-1 immune responses may have predictive value for ipilimumab treatment and argue for prospective studies in patients with established NY-ESO-1 immunity. The current findings provide a strong rationale for the clinical use of modulators of immunosuppression with concurrent approaches to favor tumor antigen-specific immune responses, such as vaccines or adoptive transfer, in patients with cancer.

Polymeric structure and host Toll-like receptor 4 dictate immunogenicity of NY-ESO-1 antigen in vivo

In search of intrinsic factors that contribute to the distinctively strong immunogenicity of a non-mutated cancer/testis antigen, we found that NY-ESO-1 forms polymeric structures through disulfide bonds. NY-ESO-1 binding to immature dendritic cells was dependent on its polymeric structure and involved Toll-like receptor-4 (TLR4) on the surface of immature dendritic cells in mouse and human. Gene gun-delivered plasmid encoding the wild-type NY-ESO-1 readily induced T cell-dependent antibody (Ab) responses in wild-type C57BL/10 mice but not TLR4-knock-out C57BL/10ScNJ mice. Disrupting polymeric structures of NY-ESO-1 by cysteine-to-serine (Cys-to-Ser) substitutions lead to diminished immunogenicity and altered TLR4-dependence in the induced Ab response. To demonstrate its adjuvant effect, NY-ESO-1 was fused with a major mugwort pollen allergen Art v 1 and a tumor-associated antigen, carbonic anhydrase 9. Plasmid DNA vaccines encoding the fusion genes generated robust immune responses against otherwise non-immunogenic targets in mice. Polymeric structure and TLR4 may play important roles in rendering NY-ESO-1 immunogenic and thus serve as a potent molecular adjuvant. NY-ESO-1 thus represents the first example of a cancer/testis antigen that is a also damage-associated molecular pattern.

Enolase 1 and calreticulin regulate the differentiation and function of mouse mast cells

It has become widely accepted that the role of mast cells is not restricted to allergic processes. Thus, mast cells play an important role in innate and adaptive immune responses, but study of proteins related to differentiation of mast cells has not been done yet. Enolase 1 is a glycolytic enzyme expressed in most tissues and calreticulin, known as endoplasmic reticulum (ER) resident chaperon, has multifunctional responses. This study aimed to investigate the effects of these proteins on the differentiation and functions of mouse bone marrow-derived mast cells (BMMCs). To identify the target proteins related to the differentiation of BMMCs, we examined the protein expression pattern of BMMCs using 2-dimensional electrophoresis (2-DE) and MALDI-TOF analysis. Expressions of FcεRIα, surface molecules (c-kit, CD40, CD40L, VCAM-1), tryptase, and cytokines were examined in BMMCs using FACS analysis, Western blot, and RT-PCR respectively. Enolase 1 and calreticulin were transfected into BMMCs, and [Ca(2+)]i levels were determined by confocal microscope, while amounts of TNF-α and LTs were measured by ELISA. Eight proteins were identified by proteomic analysis. Enolase and calreticulin siRNA transfection inhibited the expressions of FcεRIα, surface molecules, tryptase, and cytokine mRNA, which are gradually enhanced during culture periods of BMMCs. Enolase 1 and calreticulin siRNA reduced the [Ca(2+)]i levels, amounts of total TNF-α, and the release of TNF-α and leukotrienes, all of which are increased in the BMMCs activated with antigen/antibody reaction. The data suggest that enolase 1 and calreticulin are important proteins in regulating the differentiation and functions of BMMCs.

New insights into the functional role of the rheumatoid arthritis shared epitope

The shared epitope (SE) - an HLA-DRB1-encoded 5-amino acid sequence motif carried by the vast majority of rheumatoid arthritis (RA) patients - is a risk factor for severe disease. The mechanistic basis of RA-SE association is unknown. This group has previously demonstrated that the SE acts as a signal transduction ligand that activates nitric oxide and reactive oxygen species production. SE-activated signaling depends on cell surface calreticulin, a known innate immunity receptor previously implicated in immune regulation, autoimmunity and angiogenesis. Recent evidence that the SE enhances the polarization of Th17 cells, which is a key mechanism in autoimmunity, is discussed highlighting one of several potential functional effects of the SE in RA.

Poly(ADP-ribosyl)ation of mannose-binding lectin out of human kidney cells

Mannose-binding lectin was identified as a substrate of tankyrase 2, an enzyme that catalyzes poly(ADP-ribosyl)ation. The endogenous tankyrase 2 was isolated out of cytoplasm of human embryonic kidney cells. It was bound to a soluble complex of at least two other proteins; they were identified using specific antibodies and other approaches as keratin 1 and mannose-binding lectin. Using immunoblot analysis and radioactive labeling, we detected tankyrase-2-dependent poly(ADP-ribosyl)ation of mannose-binding lectin. In the presence of NAD(+), the complex of keratin 1 and lectin was dissociated, what was recorded during elution of its separate components out of affinity columns and by decrease of their apparent molecular masses during gel-filtration. Tankyrase 2 also inhibited the carbohydrate-binding function of the lectin. The latter effect was observed using mannose-binding lectin out of human serum, which is free from keratin 1. As a result of tankyrase-2 activity, the lectin lost its affinity to mannan-agarose. The discovery of this new biochemical mechanism justifies further analysis of its physiological and medical significance.

Immune response in ovarian cancer: how is the immune system involved in prognosis and therapy: potential for treatment utilization

Ovarian cancer is one of the leading causes of cancer-related death among women. Resistance to the disease occurs in more than 70% of the cases even after treated with chemotherapy agents such as paclitaxel- and platinum-based agents. The immune system is increasingly becoming a target for intense research in order to study the host's immune response against ovarian cancer. T cell populations, including NK T cells and Tregs, and cytokines have been associated with disease outcome, indicating their increasing clinical significance, having been associated with prognosis and as markers of disease progress, respectively. Harnessing the immune system capacity in order to induce antitumor response remains a major challenge. This paper examines the recent developments in our understanding of the mechanisms of development of the immune response in ovarian cancer as well as its prognostic significance and the existing experience in clinical studies.

A role for calreticulin in the pathogenesis of rheumatoid arthritis

Calreticulin (CRT) plays a role in the clearance of dying cells and has been implicated in autoimmunity. Recent evidence indicates that cell surface CRT (csCRT) acts as a signal transducing receptor for the rheumatoid arthritis (RA) shared epitope (SE). The SE binding site on CRT has been mapped to amino acid residues 217-223 in the P-domain. Upon interaction with dendritic cells (DCs), the SE activates potent immune regulatory events. In CD8α(+) DCs, which express higher abundance of csCRT, the SE inhibits the tolerogenic enzyme indoleamine 2,3 dioxygenase with resultant inhibition of regulatory T (Treg) cell differentiation. In CD8α(-) DCs, the SE ligand increases secretion of IL-6 and IL-23 and facilitates generation of Th17 cells, a T cell subset known to play a role in autoimmunity. On the basis of these recent findings, we discuss the possibility that the csCRT may play a pathogenic role in RA by transducing SE-activated Th17-polarizing signals.

Functional analysis of recombinant calreticulin fragment 39-272: implications for immunobiological activities of calreticulin in health and disease

Although calreticulin (CRT) is a major Ca(2+)-binding luminal resident protein, it can also appear on the surface of various types of cells and it functions as an immunopotentiating molecule. However, molecular mechanisms underlying the potent immunobiological activity of cell surface CRT are still unclear. In the present study, a recombinant fragment (rCRT/39-272) covering the lectin-like N domain and partial P domain of murine CRT has been expressed in Escherichia coli. The affinity-purified rCRT/39-272 assembles into homodimers and oligomers in solution and exhibits high binding affinity to various glycans, including carrageenan, alginic acids, and hyaluronic acids. Functionally, rCRT/39-272 is capable of driving the activation and maturation of B cells and cytokine production by macrophages in a TLR-4-dependent manner in vitro. It specifically binds recombinant mouse CD14, but not BAFFR and CD40. It is also able to trigger Ig class switching by B cells in the absence of T cell help both in vitro and in vivo. Furthermore, this fragment of CRT exhibits strong adjuvanticity when conjugated to polysaccharides or expressed as part of a fusion protein. Soluble CRT can be detected in the sera of patients with rheumatoid arthritis or systemic lupus erythematosus, but not in healthy subjects. We argue that CRT, either on the membrane surface of cells or in soluble form, is a potent stimulatory molecule to B cells and macrophages via the TLR-4/CD14 pathway and plays important roles in the pathogenesis of autoimmune diseases.

Immune dysregulation by the rheumatoid arthritis shared epitope

Rheumatoid arthritis (RA) is closely associated with HLA-DRB1 alleles that code a five-amino acid sequence motif in positions 70-74 of the HLA-DRbeta-chain, called the shared epitope (SE). The mechanistic basis of SE-RA association is unknown. We recently found that the SE functions as an allele-specific signal-transducing ligand that activates an NO-mediated pathway in other cells. To better understand the role of the SE in the immune system, we examined its effect on T cell polarization in mice. In CD11c(+)CD8(+) dendritic cells (DCs), the SE inhibited the enzymatic activity of indoleamine 2,3 dioxygenase, a key enzyme in immune tolerance and T cell regulation, whereas in CD11c(+)CD8(-) DCs, the ligand activated robust production of IL-6. When SE-activated DCs were cocultured with CD4(+) T cells, the differentiation of Foxp3(+) T regulatory cells was suppressed, whereas Th17 cells were expanded. The polarizing effects could be seen with SE(+) synthetic peptides, but even more so when the SE was in its natural tridimensional conformation as part of HLA-DR tetrameric proteins. In vivo administration of the SE ligand resulted in a greater abundance of Th17 cells in the draining lymph nodes and increased IL-17 production by splenocytes. Thus, we conclude that the SE acts as a potent immune-stimulatory ligand that can polarize T cell differentiation toward Th17 cells, a T cell subset that was recently implicated in the pathogenesis of autoimmune diseases, including RA.

Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)-A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c(+) blood DCs cross-presented NY-ESO-1-specific HLA-A2(157-165)-, HLA-B7(60-72)-, and HLA-Cw3(92-100)-restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1(157-165)/HLA-A2, NY-ESO-1(60-72)/HLA-B7, and NY-ESO-1(92-100)/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-1(60-72)/HLA-B7-restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A-, B-, and C-restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.

Calreticulin: non-endoplasmic reticulum functions in physiology and disease

Calreticulin (CRT), when localized to the endoplasmic reticulum (ER), has important functions in directing proper conformation of proteins and glycoproteins, as well as in homeostatic control of cytosolic and ER calcium levels. There is also steadily accumulating evidence for diverse roles for CRT localized outside the ER, including data suggesting important roles for CRT localized to the outer cell surface of a variety of cell types, in the cytosol, and in the extracellular matrix (ECM). Furthermore, the addition of exogenous CRT rescues numerous CRT-driven functions, such as adhesion, migration, phagocytosis, and immunoregulatory functions of CRT-null cells. Recent studies show that topically applied CRT has diverse and profound biological effects that enhance cutaneous wound healing in animal models. This evidence for extracellular bioactivities of CRT has provided new insights into this classically ER-resident protein, despite a lack of knowledge of how CRT exits from the ER to the cell surface or how it is released into the extracellular milieu. Nonetheless, it has become clear that CRT is a multicompartmental protein that regulates a wide array of cellular responses important in physiological and pathological processes, such as wound healing, the immune response, fibrosis, and cancer.-Gold, L. I., Eggleton, P., Sweetwyne, M. T., Van Duyn, L. B., Greives, M. R., Naylor, S.-M., Michalak, M., Murphy-Ullrich, J. E. Calreticulin: non-endoplamic reticulum functions in physiology and disease.

Immunogenic death of colon cancer cells treated with oxaliplatin

Both the pre-apoptotic exposure of calreticulin (CRT) and the post-apoptotic release of high-mobility group box 1 protein (HMGB1) are required for immunogenic cell death elicited by anthracyclins. Here, we show that both oxaliplatin (OXP) and cisplatin (CDDP) were equally efficient in triggering HMGB1 release. However, OXP, but not CDDP, stimulates pre-apoptotic CRT exposure in a series of murine and human colon cancer cell lines. Subcutaneous injection of OXP-treated colorectal cancer (CRC), CT26, cells induced an anticancer immune response that was reduced by short interfering RNA-mediated depletion of CRT or HMGB1. In contrast, CDDP-treated CT26 cells failed to induce anticancer immunity, unless recombinant CRT protein was absorbed into the cells. CT26 tumors implanted in immunocompetent mice responded to OXP treatment in vivo, and this therapeutic response was lost when CRT exposure by CT26 cells was inhibited or when CT26 cells were implanted in immunodeficient mice. The knockout of toll-like receptor 4 (TLR4), the receptor for HMGB1, also resulted in a deficient immune response against OXP-treated CT26 cells. In patients with advanced (stage IV, Duke D) CRC, who received an OXP-based chemotherapeutic regimen, the loss-of-function allele of TLR4 (Asp299Gly in linkage disequilibrium with Thr399Ile, reducing its affinity for HMGB1) was as prevalent as in the general population. However, patients carrying the TLR4 loss-of-function allele exhibited reduced progression-free and overall survival, as compared with patients carrying the normal TLR4 allele. In conclusion, OXP induces immunogenic death of CRC cells, and this effect determines its therapeutic efficacy in CRC patients.

Endogenous Jmjd6 gene product is expressed at the cell surface and regulates phagocytosis in immature monocyte-like activated THP-1 cells

A jumonji domain containing gene 6 (Jmjd6), previously referred to as phosphatidylserine receptor (PSR) gene, plays an important role in cell differentiation and development of multiple organs, although mechanisms of its action are not known. The Jmjd6 gene product was initially identified as a membrane protein that participates in phagocytosis. However, the later findings that recombinant Jmjd6 in expression systems was targeted to the nucleus challenged the role of Jmjd6 as a membrane receptor. Using immunocytochemistry approach we studied the subcellular distribution of endogenous Jmjd6 protein in THP-1 cells activated with phorbol 12-myristate 13 acetate (PMA). We found that treatment with PMA stimulated Jmjd6 expression in the cytosol of activated cells. Furthermore, Jmjd6 initially appeared at the cell surface of immature phagocytes (1-2 days after activation) but then translocated into the nucleus of differentiated macrophage-like cells (5-9 days after activation). Anti-Jmjd6 antibodies suppressed the engulfment of dead cell corpses by THP-1 cells expressing the Jmjd6 at the cell surface. These data indicate that Jmjd6 serves as a membrane-associated receptor that regulates phagocytosis in immature macrophages but is dispensable for phagocytosis and has other functions when it is expressed in the cytosol and nucleus of mature macrophage-like cells.

Antigenic stimulation with cytochrome P450 2J expressed in mouse hepatocellular carcinoma cells regulates host anti-tumour immunity

Cytochrome P450 2J subfamily (CYP2J) enzymes expressed in mouse hepatocellular carcinoma (HCC) cells were identified as an antigen recognized by specific CD4(+) T cells and the structure of its T cell epitope was determined by proteomics-based exploration. The major histocompatibility complex (MHC) class II binding peptides were isolated from I-A(k)/peptide complex of dendritic cells (DCs) loaded or unloaded with MIH-2 mouse HCC cells. MHC class II-binding peptides found in MIH-2-loaded DCs but not in unloaded DCs were determined by tandem mass spectrometric analysis. The peptide, consisting of amino acid 276-290 (DFIDAFLKEMTKYPE) of mouse CYP2J enzymes, was identified as an antigenic peptide presented in the context of MHC class II. Preventive treatment of mice with CYP2J peptide stimulated interferon (IFN)-gamma production of splenocytes and suppressed the growth of implanted CYP2J-positive MIH-2 cells but not CYP2J-negative murine bladder tumour cells. However, continuous treatment of MIH-2-bearing mice with CYP2J peptide significantly suppressed IFN-gamma production of splenocytes and accelerated the growth of implanted MIH-2 tumours in vivo. Increased frequencies of CD4(+)forkhead box P3 regulatory T cells and CD11b(+)Gr-1(+) myeloid suppressor cells were observed in splenocytes from the continuously immunized mice. These results indicate that antigenecity of CYP2J isoforms expressed in HCC cells activate host anti-tumour immunity at an initial stage of HCC, but suppress host anti-tumour immunity with excessive antigenic stimulation at an advanced stage.

Calreticulin, a multi-process calcium-buffering chaperone of the endoplasmic reticulum

Calreticulin is an ER (endoplasmic reticulum) luminal Ca2+-buffering chaperone. The protein is involved in regulation of intracellular Ca2+ homoeostasis and ER Ca2+ capacity. The protein impacts on store-operated Ca2+ influx and influences Ca2+-dependent transcriptional pathways during embryonic development. Calreticulin is also involved in the folding of newly synthesized proteins and glycoproteins and, together with calnexin (an integral ER membrane chaperone similar to calreticulin) and ERp57 [ER protein of 57 kDa; a PDI (protein disulfide-isomerase)-like ER-resident protein], constitutes the ‘calreticulin/calnexin cycle’ that is responsible for folding and quality control of newly synthesized glycoproteins. In recent years, calreticulin has been implicated to play a role in many biological systems, including functions inside and outside the ER, indicating that the protein is a multi-process molecule. Regulation of Ca2+ homoeostasis and ER Ca2+ buffering by calreticulin might be the key to explain its multi-process property.

C1q enhances IFN-gamma production by antigen-specific T cells via the CD40 costimulatory pathway on dendritic cells

Dendritic cells (DCs) are known to produce C1q, the initiator of the classical complement pathway. We demonstrate that murine DCs deficient in C1q (C1qa(-/-)) are poorer than wild-type (WT) DCs at eliciting the proliferation and Th1 differentiation of antigen-specific T cells. These defects result from decreased production of IL-12p70 by C1qa(-/-) DCs and impaired expression of costimulatory molecules CD80 and CD86 in response to CD40 ligation. The defective production of IL-12p70 and the reduced expression of CD80 and CD86 by C1qa(-/-) DCs were specifically mediated via CD40 ligation, as normal levels of IL-12p70 and CD80/86 were observed after ligation of Toll-like receptors (TLRs) on C1qa(-/-) DCs. CD40 ligation on C1qa(-/-) DCs, but not TLR ligation, results in decreased phosphorylation of p38 and ERK1/2 kinases. A strong colocalization of CD40 and C1q was observed by confocal microscopy upon CD40 ligation (but not TLR ligation) on DCs. Furthermore, human DCs from 2 C1q-deficient patients were found to have impaired IL-12p70 production in response to CD40L stimulation. Our novel data suggest that C1q augments the production of IL-12p70 by mouse and human DCs after CD40 triggering and plays important roles in sustaining the maturation of DCs and guiding the activation of T cells.

New roles for mononuclear phagocytes in cancer biology

The primary focus in the pathogenesis and treatment of human malignancies has been the tumor cell. However, the biologic properties of a malignancy are not all intrinsically determined. Interactions between heterogeneous cell populations influence the growth and survival of both normal and malignant cells. Studies defining the origin of endothelial cells involved in tumor angiogenesis first demonstrated the contributions of normal cellular environment. Recently, the mononuclear phagocyte lineage has been found to have biologically and clinically significant tumor enhancing and tumor suppressive effects. This article reviews the multiple roles of mononuclear phagocytes in cancer biology. A companion manuscript (J Pediatr Hematol Oncol. 2008, in press) describes the targeting of these cells for therapeutic benefit. Incorporating these strategies into future childhood cancer protocols could be an innovative approach for improving patient outcome.

Molecular determinants of immunogenic cell death: surface exposure of calreticulin makes the difference

The treatment of cancer by chemotherapy causes tumour cell death, mostly by apoptosis. This tumour cell death may or may not elicit an immune response. At least in some cases, the efficacy of chemotherapy critically depends on the induction of immunogenic cell death that is a type of cell demise that stimulates the activation of an adaptative anti-tumour immune response, which in turn helps to eradicate residual cancer (stem) cells. Indeed, anthracyclins care more efficient in curing tumours in immunocompetent than in T cell-deficient mice. The molecular mechanism implicated in this anti-tumour T cell activation was recently discovered. Anthracyclins cause immunogenic cell death due to their specific capacity to stimulate the translocation of calreticulin to the cell surface. Calreticulin then acts as an "eat me" signal for dendritic cells, allowing them to phagocytose tumour cells and to prime tumour antigen-specific cytotoxic T cells. Importantly, non-immunogenic chemotherapy can be rendered immunogenic by adsorbing recombinant calreticulin to tumour cells or by enforcing the translocation of endogenous calreticulin to the cell surface by means of PP1/GADD34 inhibitors. This strategy could have major implications for the treatment of human cancer. Indeed, in vivo treatments with anthracyclins can cause the translocation of calreticulin to the surface of circulating tumour cells, in patients with acute myeloid leukaemia (AML). The challenge will be to determine whether the exposure of calreticulin translocation on the tumour cell surface is linked to chemotherapy-induced anti-tumour immune responses and therapeutic efficacy in human cancer.