Necrotic tumor cell death in vivo impairs tumor-specific immune responses

Prognostic Influence of Galectin-1 in Gastric Adenocarcinoma

Galectin-1 (Gal-1), a member of the human lectin family, has garnered attention for its association with aggressive behavior in human tumors, prompting research into the development of targeted drugs. This study aims to assess the staining pattern and prognostic significance of Gal-1 immunohistochemical expression in a homogeneous cohort of Western patients with gastric cancer (GC). A total of 149 cases were included and tissue microarrays were constructed. Stromal Gal-1 expression was observed to some extent in most tumors, displaying a cytoplasmic pattern. Cases with stromal Gal-1 overexpression showed significantly more necrosis, lymphovascular invasion, advanced pTNM stages, recurrences, and cancer-related deaths. Epithelial Gal-1 expression was present in 63.8% of the cases, primarily exhibiting a cytoplasmic pattern, and its overexpression was significantly associated with lymphovascular invasion, peritumoral lymphocytic infiltration, and tumor-related death. Kaplan/Meier curves for cancer-specific survival (CSS) revealed a significantly worse prognosis for patients with tumors exhibiting stromal or epithelial Gal-1 overexpression. Furthermore, stromal Gal-1 expression stratified stage III patients into distinct prognostic subgroups. In a multivariable analysis, increased stromal Gal-1 expression emerged as an independent prognostic factor for CSS. These findings underscore the prognostic relevance of Gal-1 and suggest its potential as a target for drug development in Western patients with GC.

Immune Effects of Cryoablation in Woodchuck Hepatocellular Carcinoma

Objectives

Local and systemic immune responses evoked by locoregional therapies such as cryoablation are incompletely understood. The aim of this study was to characterize cryoablation-related immune response and the capacity of immune drugs to augment immunity upon cryoablation for the treatment of hepatocellular carcinoma (HCC) using a woodchuck hepatocellular carcinoma model.

Materials and Methods

Twelve woodchucks chronically infected with woodchuck hepatitis virus and with hepatocellular carcinoma underwent imaging with contrast-enhanced CT. Partial cryoablation of tumors in three woodchucks was performed. Fourteen days after cryoablation, liver tissues were harvested and stained with H&E and TUNEL, and immune infiltrates were quantified. Peripheral blood mononuclear cells (PBMC) were collected from ablated and nonablated woodchucks, labeled with carboxyfluorescein succinimidyl ester (CFSE) and cultured with immune-modulating drugs, including a small PD-L1 antagonist molecule (BMS-202) and three TLR7/8 agonists (DSR 6434, GS-9620, gardiquimod). After incubation, cell replication and immune cell populations were analyzed by flow cytometry.

Results

Local immune response in tumors was characterized by an increased number of CD3+ T lymphocytes and natural killer cells in the cryolesion margin compared to other tumor regions. T regulatory cells were found in higher numbers in distant tumors within the liver compared to untreated or control tumors. Cryoablation also augmented the systemic immune response as demonstrated by higher numbers of PBMC responses upon immune drug stimulation in the cryoablation group.

Conclusions

Partial cryoablation augmented immune effects in both treated and remote untreated tumor microenvironments, as well as systemically, in woodchucks with HCC. Characterization of these mechanisms may enhance development of novel drug-device combinations for treatment of HCC.

Dendritic Cell Vaccines: A Shift from Conventional Approach to New Generations

In the emerging era of cancer immunotherapy, immune checkpoint blockades (ICBs) and adoptive cell transfer therapies (ACTs) have gained significant attention. However, their therapeutic efficacies are limited due to the presence of cold type tumors, immunosuppressive tumor microenvironment, and immune-related side effects. On the other hand, dendritic cell (DC)-based vaccines have been suggested as a new cancer immunotherapy regimen that can address the limitations encountered by ICBs and ACTs. Despite the success of the first generation of DC-based vaccines, represented by the first FDA-approved DC-based therapeutic cancer vaccine Provenge, several challenges remain unsolved. Therefore, new DC vaccine strategies have been actively investigated. This review addresses the limitations of the currently most adopted classical DC vaccine and evaluates new generations of DC vaccines in detail, including biomaterial-based, immunogenic cell death-inducing, mRNA-pulsed, DC small extracellular vesicle (sEV)-based, and tumor sEV-based DC vaccines. These innovative DC vaccines are envisioned to provide a significant breakthrough in cancer immunotherapy landscape and are expected to be supported by further preclinical and clinical studies.

PD-1/PD-L1 and DNA Damage Response in Cancer

The application of immunotherapy for cancer treatment is rapidly becoming more widespread. Immunotherapeutic agents are frequently combined with various types of treatments to obtain a more durable antitumor clinical response in patients who have developed resistance to monotherapy. Chemotherapeutic drugs that induce DNA damage and trigger DNA damage response (DDR) frequently induce an increase in the expression of the programmed death ligand-1 (PD-L1) that can be employed by cancer cells to avoid immune surveillance. PD-L1 exposed on cancer cells can in turn be targeted to re-establish the immune-reactive tumor microenvironment, which ultimately increases the tumor's susceptibility to combined therapies. Here we review the recent advances in how the DDR regulates PD-L1 expression and point out the effect of etoposide, irinotecan, and platinum compounds on the anti-tumor immune response.

"Double hit" strategy: Removal of sialic acid from the dendritic cell surface and loading with CD44+/CD24-/low cell lysate inhibits tumor growth and metastasis by targeting breast cancer stem cells

Cancer stem cells (CSCs), which represent the root cause of resistance to conventional treatments, recurrence, and metastasis, constitute the critical point of failure in cancer treatments. Targeting CSCs with dendritic cell (DC)-based vaccines have been an effective strategy, but sialic acids on the surface of DCs limit the interaction with loaded antigens. We hypothesized that removal of sialic acid moieties on immature DCs (iDCs) could significantly affect DC-CSC-antigen loading, thereby leading to DC maturation and improving immune recognition and activity. The lysate of CD44⁺/CD24^-/low breast CSCs (BCSCs) was pulsed with sialidase-treated DCs to obtain mature dendritic cells (mDCs). The roles of cytoskeletal elements in antigen uptake and dendritic cell maturation were determined by immunofluorescence staining, flow cytometry, and cytokine measurement, respectively. To test the efficacy of the vaccine in vivo, CSCs tumor-bearing mice were immunized with iDC or mDC. Pulsing DCs with antigen increased the expression levels of actin, gelsolin, talin, WASp, and Arp2, especially in podosome-like regions. Compared with iDCs, mDCs expressed high levels of CD40, CD80, CD86 costimulatory molecules and increased IL-12 production. Vaccination with mDC: i) increased CD8+ and CD4 + T-cell numbers, ii) prevented tumor growth with anti-mitotic activity and apoptotic induction, iii) suppressed metastasis by decreasing Snail, Slug, and Twist expressions. This study reveals for the first time that sialic acid removal and loading with CSC antigens induces significant molecular, morphological, and functional changes in DCs and that this new DC identity may be considered for future combined immunotherapy strategies against breast tumors.

The Apoptosis Paradox in Cancer

Cancer growth represents a dysregulated imbalance between cell gain and cell loss, where the rate of proliferating mutant tumour cells exceeds the rate of those that die. Apoptosis, the most renowned form of programmed cell death, operates as a key physiological mechanism that limits cell population expansion, either to maintain tissue homeostasis or to remove potentially harmful cells, such as those that have sustained DNA damage. Paradoxically, high-grade cancers are generally associated with high constitutive levels of apoptosis. In cancer, cell-autonomous apoptosis constitutes a common tumour suppressor mechanism, a property which is exploited in cancer therapy. By contrast, limited apoptosis in the tumour-cell population also has the potential to promote cell survival and resistance to therapy by conditioning the tumour microenvironment (TME)-including phagocytes and viable tumour cells-and engendering pro-oncogenic effects. Notably, the constitutive apoptosis-mediated activation of cells of the innate immune system can help orchestrate a pro-oncogenic TME and may also effect evasion of cancer treatment. Here, we present an overview of the implications of cell death programmes in tumour biology, with particular focus on apoptosis as a process with "double-edged" consequences: on the one hand, being tumour suppressive through deletion of malignant or pre-malignant cells, while, on the other, being tumour progressive through stimulation of reparatory and regenerative responses in the TME.

Rate of Freeze Impacts the Survival and Immune Responses Post Cryoablation of Melanoma

The emergence of ablative therapies has revolutionized the treatment of inoperable solid tumors. Cryoablation stands out for its uniqueness of operation based on hypothermia, and for its ability to unleash the native tumor antigens, resulting in the generation of anti-tumor immune responses. It is not clearly understood how alterations in the rate of freeze impact the immune response outcomes. In this study, we tested fast freeze and slow freeze rates for their locoregional effectiveness and their ability to elicit immune responses in a B16F10 mouse model of melanoma. Tumor bearing mice treated with fast freeze protocol survived better than the ones treated with slow freeze protocol. Fast freeze resulted in a higher magnitude of CD4+ and CD8+ T-cell responses, and a significantly extended survival post re-challenge. Thus, fast freeze rate should be applied in any future studies employing cryoablation as an in vivo vaccination tool in conjunction with targeted immunotherapies.

Aromatic carbohydrate amphiphile disrupts cancer spheroids and prevents relapse

Spheroids recapitulate the organization, heterogeneity and microenvironment of solid tumors. Herein, we targeted spatiotemporally the accelerated metabolism of proliferative cells located on the spheroid surface that ensure structure maintenance and/or growth. We demonstrate that phosphorylated carbohydrate amphiphile acts as a potent antimetabolite due to glycolysis inhibition and to in situ formation of supramolecular net around spheroid surface where alkaline phosphatase is overexpressed. The efficiency of the treatment is higher in spheroids as compared to the conventional 2D cultures because of the 2-fold higher expression of glucose transporter 1 (GLUT1). Moreover, treated spheroids do not undergo following relapse.

A System Biology-Based Approach for Designing Combination Therapy in Cancer Precision Medicine

In this paper, we have used an agent-based stochastic tumor growth model and presented a mathematical and theoretical perspective to cancer therapy. This perspective can be used to theoretical study of precision medicine and combination therapy in individuals. We have conducted a series of in silico combination therapy experiments. Based on cancer drugs and new findings of cancer biology, we hypothesize relationships between model parameters which in some cases represent individual genome characteristics and cancer drugs, i.e., in our approach, therapy players are delegated by biologically reasonable parameters. In silico experiments showed that combined therapies are more effective when players affect tumor via different mechanisms and have different physical dimensions. This research presents for the first time an algorithm as a theoretical viewpoint for the prediction of effectiveness and classification of therapy sets.

Mitophagy in Intestinal Epithelial Cells Triggers Adaptive Immunity during Tumorigenesis

In colorectal cancer patients, a high density of cytotoxic CD8⁺ T cells in tumors is associated with better prognosis. Using a Stat3 loss-of-function approach in two wnt/β-catenin-dependent autochthonous models of sporadic intestinal tumorigenesis, we unravel a complex intracellular process in intestinal epithelial cells (IECs) that controls the induction of a CD8⁺ T cell based adaptive immune response. Elevated mitophagy in IECs causes iron(II)-accumulation in epithelial lysosomes, in turn, triggering lysosomal membrane permeabilization. Subsequent release of proteases into the cytoplasm augments MHC class I presentation and activation of CD8⁺ T cells via cross-dressing of dendritic cells. Thus, our findings highlight a so-far-unrecognized link between mitochondrial function, lysosomal integrity, and MHC class I presentation in IECs and suggest that therapies triggering mitophagy or inducing LMP in IECs may prove successful in shifting the balance toward anti-tumor immunity in colorectal cancer.

Necroptosis in tumorigenesis, activation of anti-tumor immunity, and cancer therapy

While the mechanisms underlying apoptosis and autophagy have been well characterized over recent decades, another regulated cell death event, necroptosis, remains poorly understood. Elucidating the signaling networks involved in the regulation of necroptosis may allow this form of regulated cell death to be exploited for diagnosis and treatment of cancer, and will contribute to the understanding of the complex tumor microenvironment. In this review, we have summarized the mechanisms and regulation of necroptosis, the converging and diverging features of necroptosis in tumorigenesis, activation of anti-tumor immunity, and cancer therapy, as well as attempts to exploit this newly gained knowledge to provide therapeutics for cancer.

Galectin Targeted Therapy in Oncology: Current Knowledge and Perspectives

The incidence and mortality of cancer have increased over the past decades. Significant progress has been made in understanding the underpinnings of this disease and developing therapies. Despite this, cancer still remains a major therapeutic challenge. Current therapeutic research has targeted several aspects of the disease such as cancer development, growth, angiogenesis and metastases. Many molecular and cellular mechanisms remain unknown and current therapies have so far failed to meet their intended potential. Recent studies show that glycans, especially oligosaccharide chains, may play a role in carcinogenesis as recognition patterns for galectins. Galectins are members of the lectin family, which show high affinity for β-galactosides. The galectin–glycan conjugate plays a fundamental role in metastasis, angiogenesis, tumor immunity, proliferation and apoptosis. Galectins’ action is mediated by a structure containing at least one carbohydrate recognition domain (CRD). The potential prognostic value of galectins has been described in several neoplasms and helps clinicians predict disease outcome and determine therapeutic interventions. Currently, new therapeutic strategies involve the use of inhibitors such as competitive carbohydrates, small non-carbohydrate binding molecules and antibodies. This review outlines our current knowledge regarding the mechanism of action and potential therapy implications of galectins in cancer.

Matrine induces RIP3-dependent necroptosis in cholangiocarcinoma cells

The development of acquired resistance to pro-apoptotic antitumor agents is a major impediment to the cure of cholangiocarcinoma (CCA). Antitumor drugs inducing non-apoptotic cell death are considered as a new approach to overcome such drug resistance. Here, we reported for the first time that matrine-induced necroptosis in CCA cell lines, differing from its classical role to induce apoptosis in many other kinds of cancer cells. CCA cells under matrine treatment exhibited typical necrosis-like but not apoptotic morphologic change. These matrine-induced morphologic change and cell death in CCA cells were greatly attenuated by necroptosis inhibitor necrostatin-1, but not apoptosis inhibitor z-VAD-fmk. Unlike many cancer cells with negative receptor-interacting protein 3 (RIP3) expression, moderate expression of RIP3 in CCA cells was observed and was required for matrine to induce necroptosis, which was switched to apoptosis after knocking down endogenous RIP3. Moreover, matrine could increase RIP3 expression level, which may facilitate the necroptosis process. Translocation of mixed lineage kinase-domain like (MLKL) from cytoplasm to plasma membrane as a downstream event of RIP3, as well as the increased production of reactive oxygen species (ROS) by RIP3/MLKL, was critical for matrine to induce necroptosis. In clinical study, we found RIP3 was lower but still moderately expressed in most CCA tissue samples compared with adjacent normal tissues. Taken together, we identified matrine as a necroptosis inducer in CCA by enhancing RIP3 expression and the following RIP3/MLKL/ROS signaling pathway, which provided new individualized strategies based on RIP3 expression to overcome chemoresistance in CCA therapy.

Listeria monocytogenes-Induced Cell Death Inhibits the Generation of Cell-Mediated Immunity

The influence of cell death on adaptive immunity has been studied for decades. Despite these efforts, the intricacies of how various cell death pathways shape immune responses in the context of infection remain unclear, particularly with regard to more recently discovered pathways such as pyroptosis. The emergence of Listeria monocytogenes as a promising immunotherapeutic platform demands a thorough understanding of how cell death induced in the context of infection influences the generation of CD8⁺ T-cell-mediated immune responses. To begin to address this question, we designed strains of L. monocytogenes that robustly activate necrosis, apoptosis, or pyroptosis. We hypothesized that proinflammatory cell death such as necrosis would be proimmunogenic while apoptosis would be detrimental, as has previously been reported in the context of sterile cell death. Surprisingly, we found that the activation of any host cell death in the context of L. monocytogenes infection inhibited the generation of protective immunity and specifically the activation of antigen-specific CD8⁺ T cells. Importantly, the mechanism of attenuation was unique for each type of cell death, ranging from deficits in costimulation in the context of necrosis to a suboptimal inflammatory milieu in the case of pyroptosis. Our results suggest that cell death in the context of infection is different from sterile-environment-induced cell death and that inhibition of cell death or its downstream consequences is necessary for developing effective cell-mediated immune responses using L. monocytogenes-based immunotherapeutic platforms.

Thermal ablation in cancer

Radiofrequency ablation (RFA) and cryoablation are alternative forms of therapy used widely in various pathological states, including treatment of carcinogenesis. The reason is that ablation techniques have ability of modulating the immune system. Furthermore, recent studies have applied this form of therapy on tumor microenvironment and in the systematic circulation. Moreover, RFA and cryoablation result in an inflammatory immune response along with tissue disruption. Evidence has demonstrated that these procedures affect carcinogenesis by causing a significant local inflammatory response leading to an immunogenic gene signature. The present review enlightens the current view of these techniques in cancer.

AMPK promotes tolerance to Ras pathway inhibition by activating autophagy

Targeted inhibitors of oncogenic Ras (rat sarcoma viral oncogene)-Raf signaling have shown great promise in the clinic, but resistance remains a major challenge: 30% of tumors with pathway mutations do not respond to targeted inhibitors, and of the 70% that do respond, all eventually develop resistance. Before cancer cells acquire resistance, they respond to initial drug treatment either by undergoing apoptosis ('addiction') or by surviving treatment albeit with reduced growth ('tolerance'). As these drug-tolerant cells serve as a reservoir from which resistant cells eventually emerge, inhibiting the pathways that confer tolerance could potentially delay or even prevent recurrence. Here, we show that melanomas and other cancers acquire tolerance to Ras-Raf pathway inhibitors by activating autophagy, which is mediated by the cellular energy sensor AMP-activated protein kinase (AMPK). Blocking this AMPK-mediated autophagy sensitizes drug-tolerant melanomas to Ras-Raf pathway inhibitors. Conversely, activating AMPK signaling and autophagy enables melanomas that would otherwise be addicted to the Ras-Raf pathway to instead tolerate pathway inhibition. These findings identify a key mechanism of tolerance to Ras-Raf pathway inhibitors and suggest that blocking either AMPK or autophagy in combination with these targeted inhibitors could increase tumor regression and decrease the likelihood of eventual recurrence.

Microenvironmental Effects of Cell Death in Malignant Disease

Although apoptosis is well recognized as a cell death program with clear anticancer roles, accumulating evidence linking apoptosis with tissue repair and regeneration indicates that its relationship with malignant disease is more complex than previously thought. Here we review how the responses of neighboring cells in the microenvironment of apoptotic tumor cells may contribute to the cell birth/cell death disequilibrium that provides the basis for cancerous tissue emergence and growth. We describe the bioactive properties of apoptotic cells and consider, in particular, how apoptosis of tumor cells can engender a range of responses including pro-oncogenic signals having proliferative, angiogenic, reparatory, and immunosuppressive features. Drawing on the parallels between wound healing, tissue regeneration and cancer, we propose the concept of the "onco-regenerative niche," a cell death-driven generic network of tissue repair and regenerative mechanisms that are hijacked in cancer. Finally, we consider how the responses to cell death in tumors can be targeted to provide more effective and long-lasting therapies.

Primary sterile necrotic cells fail to cross-prime CD8(+) T cells

Necrotic cells are known to activate the innate immune system and trigger inflammation by releasing damage associated molecular patterns (DAMPs). However, how necrotic cells influence the induction of antigen-specific CD8(+) T cell-mediated adaptive immune responses under sterile conditions, in the absence of pathogen associated molecular patterns (PAMPs), remains poorly understood. Here, we examined antigen-specific CD8(+) T-cell responses to primary sterile necrotic tumor cells both in vitro and in vivo. We found that primary necrotic cells alone fail to generate CD8(+) T cell-dependent immune responses toward cell-associated antigens. We show that necrotic cells trigger CD8(+) T-cell immunity only in the presence of PAMPs or analogs, such as p(dI-dC) and/or unmethylated CpG DNA. The electroporation of tumor cells with these PAMPs prior to necrosis induction triggered antigen-specific CD8(+) T-cell responses through a TLR9/MyD88-dependent pathway. In addition, we found that necrotic cells contain factors that can block the cross-priming of CD8(+) T cells even under non-sterile conditions and can serve as a possible mechanism of immunosuppression. These results suggest that antigen-specific CD8(+) T-cell responses to primary necrotic tumor cells can be induced in the presence of PAMPs and thus have a substantial impact on the development of antitumor vaccination strategies.

Immunogenicity of necrotic cell death

The mode of tumor cell death has significant effects on anti-tumor immunity. Although, previously it was thought that cell death is an inert effect, different investigators have clearly shown that dying tumors can attract, activate and mature professional antigen presenting cells and dendritic cells. In addition, others and we have shown that the type of tumor cell death not only controls the presence or absence of specific tumor antigens, but also can result in immunological responses ranging from immunosuppression to anti-tumor immunity. More importantly, it is possible to enhance anti-tumor immunity both in vitro and in vivo by targeting specific molecular mechanisms such as oligopeptidases and the proteasome. These studies not only extend our knowledge on basic immunological questions and the induction of anti-tumor immunity, but also have implications for all types of cancer treatments, in which rapid tumor cell death is induced. This review is a comprehensive summary of cell death and particularly necrosis and the pivotal role it plays in anti-tumor immunity.

Various ways to improve whole cancer cell vaccines

Immunotherapy based on whole cancer cell vaccines is regarded as a promising avenue for cancer treatment. However, limited efficacy in the first human clinical trials calls for more optimized whole cancer cell vaccines and better patient selection. It is suggested that whole cancer cell vaccines consist preferably of immunogenically killed autologous cancer stem cells associated with dendritic cells. Adjuvants should stimulate both immune effector cells and memory cells, which could be achieved through their correct dosage and timing of administration. There are indications that whole cancer cell vaccination is less effective in patients who are immunocompromised, who have specific genetic defects in their immune or cancer cells, as well as in patients in an advanced cancer stage. However, such patients form the bulk of enrolled patients in clinical trials, prohibiting an objective evaluation of the true potential of whole cancer cell immunotherapy. Each key point will be discussed.

Peptidases released by necrotic cells control CD8+ T cell cross-priming

Cross-priming of CD8+ T cells and generation of effector immune responses is pivotal for tumor immunity as well as for successful anticancer vaccination and therapy. Dead and dying cells produce signals that can influence Ag processing and presentation; however, there is conflicting evidence regarding the immunogenicity of necrotic cell death. We used a mouse model of sterile necrosis, in which mice were injected with sterile primary necrotic cells, to investigate a role of these cells in priming of CD8+ T cells. We discovered a molecular mechanism operating in Ag donor cells that regulates cross-priming of CD8+ T cells during primary sterile necrosis and thereby controls adaptive immune responses. We found that the cellular peptidases dipeptidyl peptidase 3 (DPP-3) and thimet oligopeptidase 1 (TOP-1), both of which are present in nonimmunogenic necrotic cells, eliminated proteasomal degradation products and blocked Ag cross-presentation. While sterile necrotic tumor cells failed to induce CD8+ T cell responses, their nonimmunogenicity could be reversed in vitro and in vivo by inactivation of DPP-3 and TOP-1. These results indicate that control of cross-priming and thereby immunogenicity of primary sterile necrosis relies on proteasome-dependent oligopeptide generation and functional status of peptidases in Ag donor cells.

The role of necroptosis, an alternative form of cell death, in cancer therapy

Programmed cell death plays an important role in animal development, tissue homeostasis and eliminating harmful or virally infected cells. Necroptosis, a novel form of programmed cell death, is caspase independent but RIPK and RIPK3 dependent. Moreover, it is suggested that necroptosis can be specifically inhibited by small molecular inhibitors such as necrostatin-1. Its signaling pathways have something in common with apoptosis, although the molecular mechanisms of necroptosis need to be further elucidated. Previous evidences suggest that necroptosis has significant effects in regulating various physiological processes and disease, such as ischemic brain injury, immune system disorders and cancer. In this review, the molecular mechanism of necroptosis is described and how it could be manipulated in the treatment of cancer is summarized.

Triggering cell death by nanographene oxide mediated hyperthermia

Graphene oxide (GO) has been proposed as an hyperthermia agent for anticancer therapies due to its near-infrared (NIR) optical absorption ability which, with its small two-dimensional size, could have a unique performance when compared to that of any other nanoparticle. Nevertheless, attention should be given to the hyperthermia route and the kind of GO-cell interactions induced in the process. The hyperthermia laser irradiation parameters, such as exposure time and laser power, were investigated to control the temperature rise and consequent damage in the GOs containing cell culture medium. The type of cell damage produced was evaluated as a function of these parameters. The results showed that cell culture temperature (after irradiating cells with internalized GO) increases preferentially with laser power rather than with exposure time. Moreover, when laser power is increased, necrosis is the preferential cell death leading to an increase of cytokine release to the medium.

Immunological off-target effects of standard treatments in gastrointestinal cancers

The effects on immune cells and the inflammatory microenvironment of commonly applied cancer treatments (chemotherapeutic or biologic agents, interventional radiologic procedures) have become better appreciated. Likewise, the contribution of the immune system toward the effectiveness of these treatments is clearer. The relevance of immune evasion by developing tumors is endorsed by its inclusion as one of the (updated) hallmarks of cancer. A greater understanding of this dimension can potentially lead to novel applications of existing standard of care therapies, in addition to potentiating their effect. This review summarizes the immune aspects of currently employed therapies-cytotoxic chemotherapeutics, biologic agents and interventional radiologic procedures-in solid tumor malignancies with a particular focus on those agents used in gastrointestinal cancers.

Galectin-1 as a potent target for cancer therapy: role in the tumor microenvironment

The microenvironment of a tumor is a highly complex milieu, primarily characterized by immunosuppression, abnormal angiogenesis, and hypoxic regions. These features promote tumor progression and metastasis, resulting in poor prognosis and greater resistance to existing cancer therapies. Galectin-1 is a β-galactoside binding protein that is abundantly secreted by almost all types of malignant tumor cells. The expression of galectin-1 is regulated by hypoxia-inducible factor-1 (HIF-1) and it plays vital pro-tumorigenic roles within the tumor microenvironment. In particular, galectin-1 suppresses T cell-mediated cytotoxic immune responses and promotes tumor angiogenesis. However, since galectin-1 displays many different activities by binding to a number of diverse N- or O-glycan modified target proteins, it has been difficult to fully understand how galectin-1 supports tumor growth and metastasis. This review explores the importance of galectin-1 and glycan expression patterns in the tumor microenvironment and the potential effects of inhibiting galectin-1 as a therapeutic target for cancer treatment.

Sensing of cell death by myeloid C-type lectin receptors

Molecules associated with dead or dying cells can be detected by receptors on macrophages and dendritic cells. Signals from these receptors impact myeloid cell function and play a role in determining whether death is silent or proinflammatory, tolerogenic or immunogenic. Prominent among myeloid receptors detecting dead cells are C-type lectin receptors (CLRs). Signals from these receptors variably induce endocytosis of cell corpses, corpse degradation, retrieval of dead cell-associated antigens and/or modulation of immune responses. The sensing of tissue damage by myeloid CLRs complements detection of pathogens in immunity and represents an ancient response aimed at restoring tissue homeostasis.

Adenovirus expressing both thymidine kinase and soluble PD1 enhances antitumor immunity by strengthening CD8 T-cell response

Adenoviruses harboring the herpes simplex virus thymidine kinase (HSVtk) gene under the regulation of a trans-splicing ribozyme targeting human telomerase reverse transcriptase (hTERT-TR) show marked and specific antitumor activity. In addition to inducing tumor cell death by direct cytotoxicity, it is becoming clear that HSVtk also induces antitumor immunity. Programmed death ligand 1 (PD-L1) expressed on tumor cell surfaces mediates tumor-induced immunoresistance by inhibiting PD1-expressing tumor-infiltrating T cells. Here, we explored whether a soluble form of PD1 (sPD1-Ig), which blocks PD-L1, could synergize with TERT-TR-regulated HSVtk to enhance the adenoviral therapeutic efficacy by boosting antitumor immunity. Tumor antigen released by HSVtk-transduced tumors successfully primed tumor antigen-specific CD8 T cells via dendritic cells (DC). Regression of murine tumors was markedly enhanced when sPD1-Ig was incorporated into the adenovirus as compared with a single-module adenovirus expressing only HSVtk. This effect was abolished by CD8 T-cell depletion. Consistent with this, following adoptive transfer of tumor antigen-specific CD8 T cells into tumor-bearing Rag1(-/-) mice, dual-module adenovirus significantly enhanced CD8 T cell-mediated tumor rejection. In addition, secondary tumor challenge at a distal site was completely suppressed in mice treated with a dual-module adenovirus. These results suggest that a dual-targeting strategy to elicit both tumor antigen priming and tumor-induced immunoresistance enhances CD8 T cell-mediated antitumor immunity.

Serum biomarkers of cell death for monitoring therapy response of gastrointestinal carcinomas

PURPOSE

Antitumour treatments are thought to exert their therapeutic efficacy mainly by induction of apoptosis in tumour cells. In epithelial cells, caspases, the key enzymes of apoptosis, cleave the intermediate filament protein cytokeratin (CK)-18 into specific fragments that are released into circulating blood and can be detected by a specific ELISA.

EXPERIMENTAL DESIGN

To investigate the use of CK-18 fragments as a potential biomarker for the treatment response, we examined the association of serum CK-18 levels and clinical response in 35 patients with gastrointestinal cancers.

RESULTS

While both cleaved and total CK-18 levels were intrinsically elevated in tumour patients, they were further increased during 5-fluorouracil (5-FU)-based therapy. Importantly, the increased levels of CK-18 could discriminate between patients with different clinical response. Cancer patients with a partial response or stable disease revealed a significantly higher increase of cleaved CK-18 during chemotherapy as compared to patients with progressive disease.

CONCLUSIONS

Our results suggest that detection of circulating caspase-cleaved CK-18 might be a useful serum biomarker for monitoring treatment response and should merit further evaluation in larger patient groups.

Tumor apoptotic bodies inhibit CTL responses and antitumor immunity via membrane-bound transforming growth factor-beta1 inducing CD8+ T-cell anergy and CD4+ Tr1 cell responses

Tumor cell apoptosis induced by radiation therapy results in apoptotic tumor cells and apparition of membrane blebs termed apoptotic bodies (APB). The immune responses induced by apoptotic tumor cells have been extensively studied. However, the role of APB in modulation of tumor immune responses is elusive. In this study, we induced apoptosis in 90% ovabumin-expressing EG7 tumor cells by in vitro irradiation (9,000 rad) of tumor cells with a subsequent cell culture for 9 hours. APB purified from irradiation-induced apoptotic EG7 cell culture supernatant by differential ultracentrifugation were vesicles with 50 to 90 nm in diameter and expressed apoptosis-specific Annexin V, 14-3-3, and Histone H3. We then investigated its potential modulation in DC(OVA)-induced T-cell responses and antitumor immunity. We found that EG7-derived APB were tolerogenic and capable of suppressing DC(OVA)-stimulated CD8+ CTL responses and antitumor immunity via its induction of CD8+ T-cell anergy and type 1 regulatory CD4+ T-cell responses. Analysis of apoptotic tumor cells and APB revealed the expression of membrane-bound transforming growth factor (TGF)-beta1 associated with irradiation-induced apoptosis formation, which is a result from activation of transcriptional factor NF-AT specific for TGF-beta1 promoters. Our data further elucidate that it is the membrane-bound TGF-beta1 expression on APB that contributes to its in vitro antiproliferative effect as shown by using neutralizing TGF-beta1-specific antibody. Administration of anti-TGF-beta1 antibody in vivo also blocked APB-mediated immune suppression of CD8+ CTL responses and antitumor immunity. Therefore, our study may have great impact in designing a combined radiation therapy with immunotherapy of cancer.

Combination of active specific immunotherapy or adoptive antibody or lymphocyte immunotherapy with chemotherapy in the treatment of cancer

Successful treatment of cancer patients with a combination of monoclonal antibodies (mAb) and chemotherapeutic drugs has spawned various other forms of additional combination therapies, including vaccines or adoptive lymphocyte transfer combined with chemotherapeutics. These therapies were effective against established tumors in animal models and showed promising results in initial clinical trials in cancer patients, awaiting testing in larger randomized controlled studies. Although combination between immunotherapy and chemotherapy has long been viewed as incompatible as chemotherapy, especially in high doses meant to increase anti-tumor efficacy, has induced immunosuppression, various mechanisms may explain the reported synergistic effects of the two types of therapies. Thus direct effects of chemotherapy on tumor or host environment, such as induction of tumor cell death, elimination of regulatory T cells, and/or enhancement of tumor cell sensitivity to lysis by CTL may account for enhancement of immunotherapy by chemotherapy. Furthermore, induction of lymphopenia by chemotherapy has increased the efficacy of adoptive lymphocyte transfer in cancer patients. On the other hand, immunotherapy may directly modulate the tumor's sensitivity to chemotherapy. Thus, anti-tumor mAb can increase the sensitivity of tumor cells to chemotherapeutic drugs and patients treated first with immunotherapy followed by chemotherapy showed higher clinical response rates than patients that had received chemotherapy alone. In conclusion, combination of active specific immunotherapy or adoptive mAb or lymphocyte immunotherapy with chemotherapy has great potential for the treatment of cancer patients which needs to be confirmed in larger controlled and randomized Phase III trials.

Role of chaperones and FcgammaR in immunogenic death

Cell death under physiologic conditions does not lead to the induction of immunity. However recognition of stressed or opsonized cells can trigger immune responses. Recent studies have begun to illustrate the critical role of molecular chaperones such as inducible heat shock proteins in mediating immunogenicity of stressed cells. Immunity to opsonized cells depends in part on the engagement and the balance of activating and inhibitory FcgammaRs on antigen presenting dendritic cells. Understanding both these pathways of immunogenic cell death may yield novel approaches to regulate immunity.

Histone deacetylase regulation of immune gene expression in tumor cells

Epigenetic modifications of chromatin, such as histone acetylation, are involved in repression of tumor antigens and multiple immune genes that are thought to facilitate tumor escape. The status of acetylation in a cell is determined by the balance of the activities of histone acetyltransferases and histone deacetylases. Inhibitors of histone deacetylase (HDACi) can enhance the expression of immunologically important molecules in tumor cells and HDACi treated tumor cells are able to induce immune responses in vitro and in vivo. Systemic HDACi are in clinical trails in cancer and also being used in several autoimmune disease models. To date, 18 HDACs have been reported in human cells and more than thirty HDACi identified, although only a few immune targets of these inhibitors have been identified. Here, we discuss the molecular pathways employed by HDACi and their potential role in inducing immune responses against tumors. We review data suggesting that selection of target specific HDACi and combinations with other agents and modalities, including those that activate stress pathways, may further enhance the efficacy of epigenetic therapies.

Molecular characteristics of immunogenic cancer cell death

Apoptotic cell death is initiated by a morphologically homogenous entity that was considered to be non-immunogenic and non-inflammatory in nature. However, recent advances suggest that apoptosis, under certain circumstances, can be immunogenic. In particular, some characteristics of the plasma membrane, acquired at preapoptotic stage, can cause immune effectors to recognize and attack preapoptotic tumor cells. The signals that mediate the immunogenicity of tumor cells involve elements of the DNA damage response (such as ataxia telangiectasia mutated and p53 activation), elements of the endoplasmic reticulum stress response (such as eukaryotic initiation factor 2alpha phosphorylation), as well as elements of the apoptotic response (such as caspase activation). Depending on the signal-transduction pathway, tumor cells responding to chemotherapy or radiotherapy can express 'danger' and 'eat me' signals on the cell surface (such as NKG2D ligands, heat-shock proteins and calreticulin) or can secrete/release immunostimulatory factors (such as cytokines and high-mobility group box 1) to stimulate innate immune effectors. Likewise, the precise sequence of such events influences the 'decision' of the immune system to mount a cognate response or not. We therefore anticipate that the comprehension of the mechanisms governing the immunogenicity of cell death will have a profound impact on the design of anticancer therapies.