De novo necroptosis creates an inflammatory environment mediating tumor susceptibility to immune checkpoint inhibitors

Oncolytic senecavirus A in tumor immunotherapy: Mechanisms, progress, and future directions

Oncolytic virotherapy has emerged as a promising immunotherapy strategy against cancer. As the first picornavirus tested in humans for its oncolytic potential, Senecavirus A (SVA) possesses several advantageous features, including its small size, rapid replication, and ability to penetrate the vascular system of solid tumors, allowing for the specific targeting and lysis of tumor cells. Additionally, SVA does not integrate into the host genome, thus avoiding potential genomic damage, and it lacks oncogenes or other virulence genes. Importantly, no significant pathogenic effects have been observed in humans or companion animals. Due to its simple genetic structure, SVA is amenable to various genetic modifications, allowing it to carry exogenous genes to further enhance tumor therapy. This review summarizes current knowledge of SVA's mechanisms of action and its progress in oncolytic therapy research, while also addressing the challenges and future directions.

Virus replication is not required for oncolytic bovine herpesvirus-1 immunotherapy

Oncolytic viruses are a promising approach for cancer treatment where viruses selectively target and kill cancer cells while also stimulating an immune response. Among viruses with this ability, bovine herpesvirus-1 (BoHV-1) has several advantages, including observations suggesting it may not require viral replication for its anti-cancer effects. We previously demonstrated that binding and penetration of enveloped virus particles are sufficient to trigger intrinsic and innate immune signaling in normal cells, while other groups have published the efficacy of non-replicating viruses as viable immunotherapies in different cancer models. In this work, we definitively show that live and UV-inactivated (UV) (non-replicating) BoHV-1-based regimens extend survival of tumor-bearing mice to similar degrees and induce infiltration of similar immune cell populations, with the exception of neutrophils. Transcriptomic analysis of tumors treated with either live or UV BoHV-1-based regimens revealed similar pathway enrichment and a subset of overlapping differentially regulated genes, suggesting live and UV BoHV-1 have similar mechanisms of activity. Last, we present a gene signature across our in vitro and in vivo models that could potentially be used to validate new BoHV-1 therapeutics. This work contributes to the growing body of literature showing that replication may not be necessary for therapeutic efficacy of viral immunotherapies.

Induced Necroptosis and Its Role in Cancer Immunotherapy

Necroptosis is a type of regulated cell death (RCD) that is triggered by changes in the extracellular or intracellular milieu that are picked up by certain death receptors. Thanks to its potent capacity to induce immunological responses and overcome apoptotic resistance, it has garnered significant attention as a potential cancer treatment. Basic information for the creation of nano-biomedical treatments is provided by studies on the mechanisms underlying tumor necroptosis. Receptor-interacting protein kinase 1 (RIPK1)-RIPK3-mediated necroptosis, Toll-like receptor domain-containing adapter-inducing interferon (IFN)-β (TRIF)-RIPK3-mediated necroptosis, Z-DNA-binding protein 1 (ZBP1)-RIPK3-mediated necroptosis, and IFNR-mediated necroptosis are the four signaling pathways that collectively account for triggered necroptosis in this review. Necroptosis has garnered significant interest as a possible cancer treatment strategy because, in contrast to apoptosis, it elicits immunological responses that are relevant to therapy. Thus, a thorough discussion is held on the connections between tumor cell necroptosis and the immune environment, cancer immunosurveillance, and cells such as dendritic cells (DCs), cytotoxic T cells, natural killer (NK) cells, natural killer T (NKT) cells, and their respective cytokines. Lastly, a summary of the most recent nanomedicines that cause necroptosis in order to cause immunogenic cell death is provided in order to emphasize their promise for cancer immunotherapy.

A necroptosis-regulated model from single-cell analysis that predicts survival and identifies the Pivotal role of MAGEA6 in hepatocellular carcinoma

Objective

Hepatocellular carcinoma (HCC) ranks as the third leading cause of cancer-related deaths, constituting 75%-85 % of all primary liver cancers. The objective of this study was to develop a necroptosis-related gene signature using single-cell and bulk RNA sequencing to predict HCC patient prognoses.

Methods

A total of 25 key necroptosis regulators were identified from previous literature. We evaluated the necroptosis scores of different cell types using single-cell sequencing data from HCC and analyzed 168 necroptosis-related genes. The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) dataset served as the training set for establishing a novel necroptosis-related gene risk signature, employing univariate and multivariate Cox regression analyses. Additionally, the study examined the model's relevance in immunity and immunotherapy, and predicted chemosensitivity in HCC patients based on the gene signature. The key genes were validated by the biological experiments.

Results

Compared to other cell types, hepatoma cells displayed the lowest necroptosis scores. A new six-gene necroptosis-related signature (S100A11, MAGEC2, MAGEA6, CTP2C9, SOX4, AKR1B10) was developed using the TCGA database and validated in the ICGC database. Patients in the high-risk category had poorer prognoses, with the risk score serving as an independent prognostic indicator beyond other clinical factors. These high-risk patients also exhibited greater immune infiltration but demonstrated a weaker anti-tumor response due to elevated expression of immune checkpoints. Pathways involving hypoxia, glycolysis, and P53, as well as the frequency of P53 somatic mutations, were notably heightened in the high-risk group. Additionally, the six genes in the model showed significantly different mRNA expression in hepatoma cell lines compared to normal hepatocytes, with the role of MAGEA6 in liver cancer being elucidated through critical experiments.

Conclusions

This study successfully developed a six-gene necroptosis-related signature to predict prognoses in HCC patients. It further explored the roles of necroptosis in hepatoma cells and the tumor microenvironment.

Targeting necroptosis: a promising avenue for respiratory disease treatment

Respiratory diseases are a growing concern in public health because of their potential to endanger the global community. Cell death contributes critically to the pathophysiology of respiratory diseases. Recent evidence indicates that necroptosis, a unique form of programmed cell death (PCD), plays a vital role in the molecular mechanisms underlying respiratory diseases, distinguishing it from apoptosis and conventional necrosis. Necroptosis is a type of inflammatory cell death governed by receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed-lineage kinase domain-like protein (MLKL), resulting in the release of intracellular contents and inflammatory factors capable of initiating an inflammatory response in adjacent tissues. These necroinflammatory conditions can result in significant organ dysfunction and long-lasting tissue damage within the lungs. Despite evidence linking necroptosis to various respiratory diseases, there are currently no specific alternative treatments that target this mechanism. This review provides a comprehensive overview of the most recent advancements in understanding the significance and mechanisms of necroptosis. Specifically, this review emphasizes the intricate association between necroptosis and respiratory diseases, highlighting the potential use of necroptosis as an innovative therapeutic approach for treating these conditions.

A RIPK1-specific PROTAC degrader achieves potent antitumor activity by enhancing immunogenic cell death

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) functions as a critical stress sentinel that coordinates cell survival, inflammation, and immunogenic cell death (ICD). Although the catalytic function of RIPK1 is required to trigger cell death, its non-catalytic scaffold function mediates strong pro-survival signaling. Accordingly, cancer cells can hijack RIPK1 to block necroptosis and evade immune detection. We generated a small-molecule proteolysis-targeting chimera (PROTAC) that selectively degraded human and murine RIPK1. PROTAC-mediated depletion of RIPK1 deregulated TNFR1 and TLR3/4 signaling hubs, accentuating the output of NF-κB, MAPK, and IFN signaling. Additionally, RIPK1 degradation simultaneously promoted RIPK3 activation and necroptosis induction. We further demonstrated that RIPK1 degradation enhanced the immunostimulatory effects of radio- and immunotherapy by sensitizing cancer cells to treatment-induced TNF and interferons. This promoted ICD, antitumor immunity, and durable treatment responses. Consequently, targeting RIPK1 by PROTACs emerges as a promising approach to overcome radio- or immunotherapy resistance and enhance anticancer therapies.

Immunogenic cell death in cancer: targeting necroptosis to induce antitumour immunity

Most metastatic cancers remain incurable due to the emergence of apoptosis-resistant clones, fuelled by intratumour heterogeneity and tumour evolution. To improve treatment, therapies should not only kill cancer cells but also activate the immune system against the tumour to eliminate any residual cancer cells that survive treatment. While current cancer therapies rely heavily on apoptosis - a largely immunologically silent form of cell death - there is growing interest in harnessing immunogenic forms of cell death such as necroptosis. Unlike apoptosis, necroptosis generates second messengers that act on immune cells in the tumour microenvironment, alerting them of danger. This lytic form of cell death optimizes the provision of antigens and adjuvanticity for immune cells, potentially boosting anticancer treatment approaches by combining cellular suicide and immune response approaches. In this Review, we discuss the mechanisms of necroptosis and how it activates antigen-presenting cells, drives cross-priming of CD8+ T cells and induces antitumour immune responses. We also examine the opportunities and potential drawbacks of such strategies for exposing cancer cells to immunological attacks.

Prognostic models for immunotherapy in non-small cell lung cancer: A comprehensive review

The introduction of immune checkpoint inhibitors (ICIs) has revolutionized the treatment of lung cancer. Given the limited clinical benefits of immunotherapy in patients with non-small cell lung cancer (NSCLC), various predictors have been shown to significantly influence prognosis. However, no single predictor is adequate to forecast patients' survival benefit. Therefore, it's imperative to develop a prognostic model that integrates multiple predictors. This model would be instrumental in identifying patients who might benefit from ICIs. Retrospective analysis and small case series have demonstrated the potential role of these models in prognostic prediction, though further prospective investigation is required to evaluate more rigorously their application in these contexts. This article presents and summarizes the latest research advancements on immunotherapy prognostic models for NSCLC from multiple omics perspectives and discuss emerging strategies being developed to enhance the domain.

Pyroptosis activates conventional type I dendritic cells to mediate the priming of highly functional anticancer T cells

BACKGROUND

Initiation of antitumor immunity is reliant on the stimulation of dendritic cells (DCs) to present tumor antigens to naïve T cells and generate effector T cells that can kill cancer cells. Induction of immunogenic cell death after certain types of cytotoxic anticancer therapies can stimulate T cell-mediated immunity. However, cytotoxic therapies simultaneously activate multiple types of cellular stress and programmed cell death; hence, it remains unknown what types of cancer cell death confer superior antitumor immunity.

METHODS

Murine cancer cells were engineered to activate apoptotic or pyroptotic cell death after Dox-induced expression of procell death proteins. Cell-free supernatants were collected to measure secreted danger signals, cytokines, and chemokines. Tumors were formed by transplanting engineered tumor cells to specifically activate apoptosis or pyroptosis in established tumors and the magnitude of immune response measured by flow cytometry. Tumor growth was measured using calipers to estimate end point tumor volumes for Kaplan-Meier survival analysis.

RESULTS

We demonstrated that, unlike apoptosis, pyroptosis induces an immunostimulatory secretome signature. In established tumors pyroptosis preferentially activated CD103+ and XCR1+ type I conventional DCs (cDC1) along with a higher magnitude and functionality of tumor-specific CD8+ T cells and reduced number of regulatory T cells within the tumor. Depletion of cDC1 or CD4+ and CD8+ T cells ablated the antitumor response leaving mice susceptible to a tumor rechallenge.

CONCLUSION

Our study highlights that distinct types of cell death yield varying immunotherapeutic effect and selective activation of pyroptosis can be used to potentiate multiple aspects of the anticancer immunity cycle.

Intratumoral Injection of Large Surface Area Microparticle Taxanes in Carcinomas Increases Immune Effector Cell Concentrations, Checkpoint Expression, and Synergy with Checkpoint Inhibitors: A Review of Preclinical and Clinical Studies

This review summarizes development of large surface area microparticle paclitaxel (LSAM-PTX) and docetaxel (LSAM-DTX) for local treatment of primary carcinomas with emphasis on immunomodulation. Intratumoral (IT) delivery of LSAM-PTX and LSAM-DTX provides continuous, therapeutic drug levels for several weeks. Preclinical studies and clinical trials reported a reduction in tumor volume (TV) and immunomodulation in primary tumor and peripheral blood with increases in innate and adaptive immune cells and decreases in suppressor cells. Increased levels of checkpoint expression of immune cells occurred in clinical trials of high-risk non-muscle-invasive bladder cancer (LSAM-DTX) and unresectable localized pancreatic cancer (LSAM-PTX). TV reduction and increases in immune effector cells occurred following IT LSAM-DTX and IT LSAM-PTX together with anti-mCTLA-4 and anti-mPD-1, respectively. Synergistic benefits from combinatorial therapy in a 4T1-Luc breast cancer model included reduction of metastasis with IT LSAM-DTX + anti-mCTLA-4. IT LSAM-PTX and LSAM-DTX are tumoricidal, immune enhancing, and may improve solid tumor response to immune checkpoint inhibitors without additional systemic toxicity.

Construction of disulfidptosis-based immune response prediction model with artificial intelligence and validation of the pivotal grouping oncogene c-MET in regulating T cell exhaustion

Background

Given the lack of research on disulfidptosis, our study aimed to dissect its role in pan-cancer and explore the crosstalk between disulfidptosis and cancer immunity.

Methods

Based on TCGA, ICGC, CGGA, GSE30219, GSE31210, GSE37745, GSE50081, GSE22138, GSE41613, univariate Cox regression, LASSO regression, and multivariate Cox regression were used to construct the rough gene signature based on disulfidptosis for each type of cancer. SsGSEA and Cibersort, followed by correlation analysis, were harnessed to explore the linkage between disulfidptosis and cancer immunity. Weighted correlation network analysis (WGCNA) and Machine learning were utilized to make a refined prognosis model for pan-cancer. In particular, a customized, enhanced prognosis model was made for glioma. The siRNA transfection, FACS, ELISA, etc., were employed to validate the function of c-MET.

Results

The expression comparison of the disulfidptosis-related genes (DRGs) between tumor and nontumor tissues implied a significant difference in most cancers. The correlation between disulfidptosis and immune cell infiltration, including T cell exhaustion (Tex), was evident, especially in glioma. The 7-gene signature was constructed as the rough model for the glioma prognosis. A pan-cancer suitable DSP clustering was made and validated to predict the prognosis. Furthermore, two DSP groups were defined by machine learning to predict the survival and immune therapy response in glioma, which was validated in CGGA. PD-L1 and other immune pathways were highly enriched in the core blue gene module from WGCNA. Among them, c-MET was validated as a tumor driver gene and JAK3-STAT3-PD-L1/PD1 regulator in glioma and T cells. Specifically, the down-regulation of c-MET decreased the proportion of PD1+ CD8+ T cells.

Conclusion

To summarize, we dissected the roles of DRGs in the prognosis and their relationship with immunity in pan-cancer. A general prognosis model based on machine learning was constructed for pan-cancer and validated by external datasets with a consistent result. In particular, a survival-predicting model was made specifically for patients with glioma to predict its survival and immune response to ICIs. C-MET was screened and validated for its tumor driver gene and immune regulation function (inducing t-cell exhaustion) in glioma.

Determinants for Antitumor and Protumor Effects of Programmed Cell Death

Cytotoxic anticancer therapies activate programmed cell death in the context of underlying stress and inflammatory signaling to elicit the emission of danger signals, cytokines, and chemokines. In a concerted manner, these immunomodulatory secretomes stimulate antigen presentation and T cell-mediated anticancer immune responses. In some instances, cell death-associated secretomes attract immunosuppressive cells to promote tumor progression. As it stands, cancer cell death-induced changes in the tumor microenvironment that contribute to antitumor or protumor effects remain largely unknown. This is complicated to examine because cell death is often subverted by tumors to circumvent natural, and therapy-induced, immunosurveillance. Here, we provide insights into important but understudied aspects of assessing the contribution of cell death to tumor elimination or cancer progression, including the role of tumor-associated genetics, epigenetics, and oncogenic factors in subverting immunogenic cell death. This perspective will also provide insights on how future studies may address the complex antitumor and protumor immunologic effects of cell death, while accounting for variations in tumor genetics and underlying microenvironment.

Implications of different cell death patterns for prognosis and immunity in lung adenocarcinoma

In recent years, lung adenocarcinoma (LUAD) has become a focus of attention due to its low response to treatment, poor prognosis, and lack of reliable indicators to predict the progression or therapeutic effect of LUAD. Different cell death patterns play a crucial role in tumor development and are promising for predicting LUAD prognosis. From the TCGA and GEO databases, we obtained bulk transcriptomes, single-cell transcriptomes, and clinical information. Genes in 15 types of cell death were analyzed for cell death index (CDI) signature establishment. The CDI signature using necroptosis + immunologic cell death-related genes was established in the TCGA cohort with the 1-, 2-, 3-, 4- and 5-year AUC values were 0.772, 0.736, 0.723, 0.795, and 0.743, respectively. The prognosis was significantly better in the low CDI group than in the high CDI group. We also investigated the relationship between the CDI signature and clinical variables, published prognosis biomarkers, immune cell infiltration, functional enrichment pathways, and immunity biomarkers. In vitro assay showed that HNRNPF and FGF2 promoted lung cancer cell proliferation and migration and were also involved in cell death. Therefore, as a robust prognosis biomarker, CDI signatures can screen for patients who might benefit from immunotherapy and improve diagnostic accuracy and LUAD patient outcomes.

Roles of RIPK1 as a stress sentinel coordinating cell survival and immunogenic cell death

Cell death and inflammation are closely linked arms of the innate immune response to combat infection and tissue malfunction. Recent advancements in our understanding of the intricate signals originating from dying cells have revealed that cell death serves as more than just an end point. It facilitates the exchange of information between the dying cell and cells of the tissue microenvironment, particularly immune cells, alerting and recruiting them to the site of disturbance. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is emerging as a critical stress sentinel that functions as a molecular switch, governing cellular survival, inflammatory responses and immunogenic cell death signalling. Its tight regulation involves multiple layers of post-translational modifications. In this Review, we discuss the molecular mechanisms that regulate RIPK1 to maintain homeostasis and cellular survival in healthy cells, yet drive cell death in a context-dependent manner. We address how RIPK1 mutations or aberrant regulation is associated with inflammatory and autoimmune disorders and cancer. Moreover, we tease apart what is known about catalytic and non-catalytic roles of RIPK1 and discuss the successes and pitfalls of current strategies that aim to target RIPK1 in the clinic.

Necroptosis in the sarcoma immune microenvironment: From biology to therapy

Apoptosis resistance remains a major obstacle to treatment failure in sarcoma. Necroptosis is a caspase-independent programmed cell death, investigated as a novel strategy to eradicate anti-apoptotic tumor cells. The process is mediated by the receptor-interacting proteins kinase family and mixed lineage kinase domain-like proteins, which is morphologically similar to necrosis. Recent studies suggest that necroptosis in the tumor microenvironment has pro- or anti-tumor effects on immune response and cancer development. Necroptosis-related molecules display a remarkable value in prognosis prediction and therapeutic response evaluation of sarcoma. Furthermore, the induction of tumor necroptosis has been explored as a feasible therapeutic strategy against sarcoma and to synergize with immunotherapy. This review discusses the dual roles of necroptosis in the immune microenvironment and tumor progression, and explores the potential of necroptosis as a new target for sarcoma treatment.

Necroptosis-related signatures identify two distinct hepatocellular carcinoma subtypes: Implications for predicting drug sensitivity and prognosis

Background

Necroptosis is associated with oncogenesis, tumor immunity and progression. This research aims to investigate the association of necroptosis-related genes with drug sensitivity and prognosis in hepatocellular carcinoma (HCC).

Methods

Based on necroptosis-related signatures, HCC patients retrieved from the TCGA database were categorized. Survival outcomes, mutation profile, immune microenvironment, and drug sensitivity between HCC subtypes were further compared. Then, LASSO analysis was performed to construct a necroptosis-related prognostic signature, which was further evaluated using another independent cohort.

Results

A total of 371 patients with HCC could be categorized into two necroptosis-related subtypes. About 36% of patients were allocated to subtype A, with worse survival, more mutant TP53, and a lower likelihood of immunotherapy response. In contrast, patients in subtype B had a favorable prognosis, with lower expression of immunosuppressive signatures but a lower abundance of B and CD8⁺ T-cell infiltration. The prognostic risk score calculated using the expression levels of nine genes involved in the necroptosis pathway (MLKL, FADD, XIAP, USP22, UHRF1, CASP8, RIPK3, ZBP1, and FAS) showed a significant association with tumor stage, histologic grade, and Child‒Pugh score. Additionally, the risk score model was proven to be accurate in both the training and independent external validation cohorts and performed better than the TNM staging system and three well-recognized risk score models.

Conclusions

Based on necroptosis-related signatures, we identified two HCC subtypes with distinctive immune microenvironments, mutation profiles, drug sensitivities, and survival outcomes. A novel well-performing prognostic model was further constructed.

Oncolytic virotherapy: basic principles, recent advances and future directions

Oncolytic viruses (OVs) have attracted growing awareness in the twenty-first century, as they are generally considered to have direct oncolysis and cancer immune effects. With the progress in genetic engineering technology, OVs have been adopted as versatile platforms for developing novel antitumor strategies, used alone or in combination with other therapies. Recent studies have yielded eye-catching results that delineate the promising clinical outcomes that OVs would bring about in the future. In this review, we summarized the basic principles of OVs in terms of their classifications, as well as the recent advances in OV-modification strategies based on their characteristics, biofunctions, and cancer hallmarks. Candidate OVs are expected to be designed as "qualified soldiers" first by improving target fidelity and safety, and then equipped with "cold weapons" for a proper cytocidal effect, "hot weapons" capable of activating cancer immunotherapy, or "auxiliary weapons" by harnessing tactics such as anti-angiogenesis, reversed metabolic reprogramming and decomposing extracellular matrix around tumors. Combinations with other cancer therapeutic agents have also been elaborated to show encouraging antitumor effects. Robust results from clinical trials using OV as a treatment congruously suggested its significance in future application directions and challenges in developing OVs as novel weapons for tactical decisions in cancer treatment.

Oncolytic BHV-1 Is Sufficient to Induce Immunogenic Cell Death and Synergizes with Low-Dose Chemotherapy to Dampen Immunosuppressive T Regulatory Cells

Immunogenic cell death (ICD) can switch immunologically "cold" tumors "hot", making them sensitive to immune checkpoint inhibitor (ICI) therapy. Many therapeutic platforms combine multiple modalities such as oncolytic viruses (OVs) and low-dose chemotherapy to induce ICD and improve prognostic outcomes. We previously detailed many unique properties of oncolytic bovine herpesvirus type 1 (oBHV) that suggest widespread clinical utility. Here, we show for the first time, the ability of oBHV monotherapy to induce bona fide ICD and tumor-specific activation of circulating CD8⁺ T cells in a syngeneic murine model of melanoma. The addition of low-dose mitomycin C (MMC) was necessary to fully synergize with ICI through early recruitment of CD8⁺ T cells and reduced infiltration of highly suppressive PD-1⁺ Tregs. Cytokine and gene expression analyses within treated tumors suggest that the addition of MMC to oBHV therapy shifts the immune response from predominantly anti-viral, as evidenced by a high level of interferon-stimulated genes, to one that stimulates myeloid cells, antigen presentation and adaptive processes. Collectively, these data provide mechanistic insights into how oBHV-mediated therapy modalities overcome immune suppressive tumor microenvironments to enable the efficacy of ICI therapy.

Resistance of MMTV-NeuT/ATTAC mice to anti-PD-1 immune checkpoint therapy is associated with macrophage infiltration and Wnt pathway expression

One of the central challenges for cancer therapy is the identification of factors in the tumor microenvironment that increase tumor progression and immune tolerance. In breast cancer, fibrosis is a histopathologic criterion for invasive cancer and poor survival that results from inflammatory factors and remodeling of the extracellular matrix to produce an immune tolerant microenvironment. To determine whether tolerance is associated with the immune checkpoint, Programmed Cell Death 1 (PD-1), NeuT/ATTAC mice, a conditional model of mammary fibrosis that we recently developed, were administered a murine-specific anti-PD-1 mAb related to pembrolizumab, and drug response was monitored by tumor development, imaging mass cytometry, immunohistochemistry and tumor gene expression by RNAseq. Tumor progression in NeuT/ATTAC mice was unaffected by weekly injection of anti-PD-1 over four months. Insensitivity to anti-PD-1 was associated with several processes, including increased tumor-associated macrophages (TAM), epithelial to mesenchymal transition (EMT), fibroblast proliferation, an enhanced extracellular matrix and the Wnt signaling pathway, including increased expression of Fzd5, Wnt5a, Vimentin, Mmp3, Col2a1 and Tgfβ1. These results suggest potential therapeutic avenues that may enhance PD-1 immune checkpoint sensitivity, including the use of tumor microenvironment targeted agents and Wnt pathway inhibitors.

Targeting cell death pathways for cancer therapy: recent developments in necroptosis, pyroptosis, ferroptosis, and cuproptosis research

Many types of human cells self-destruct to maintain biological homeostasis and defend the body against pathogenic substances. This process, called regulated cell death (RCD), is important for various biological activities, including the clearance of aberrant cells. Thus, RCD pathways represented by apoptosis have increased in importance as a target for the development of cancer medications in recent years. However, because tumor cells show avoidance to apoptosis, which causes treatment resistance and recurrence, numerous studies have been devoted to alternative cancer cell mortality processes, namely necroptosis, pyroptosis, ferroptosis, and cuproptosis; these RCD modalities have been extensively studied and shown to be crucial to cancer therapy effectiveness. Furthermore, evidence suggests that tumor cells undergoing regulated death may alter the immunogenicity of the tumor microenvironment (TME) to some extent, rendering it more suitable for inhibiting cancer progression and metastasis. In addition, other types of cells and components in the TME undergo the abovementioned forms of death and induce immune attacks on tumor cells, resulting in enhanced antitumor responses. Hence, this review discusses the molecular processes and features of necroptosis, pyroptosis, ferroptosis, and cuproptosis and the effects of these novel RCD modalities on tumor cell proliferation and cancer metastasis. Importantly, it introduces the complex effects of novel forms of tumor cell death on the TME and the regulated death of other cells in the TME that affect tumor biology. It also summarizes the potential agents and nanoparticles that induce or inhibit novel RCD pathways and their therapeutic effects on cancer based on evidence from in vivo and in vitro studies and reports clinical trials in which RCD inducers have been evaluated as treatments for cancer patients. Lastly, we also summarized the impact of modulating the RCD processes on cancer drug resistance and the advantages of adding RCD modulators to cancer treatment over conventional treatments.

PGAM5: A necroptosis gene associated with poor tumor prognosis that promotes cutaneous melanoma progression

Cutaneous melanoma is the deadliest type of skin cancer, and its highly aggressive and metastatic nature leads to an extremely poor prognosis. Necrotizing apoptosis, a specific form of programmed cell death, has been extensively studied in recent years. In this study, we analyzed the relationship between necroptosis-related functional genes and cutaneous melanoma in order to identify the biomarkers associated with the prognosis and progression of cutaneous melanoma. Cutaneous melanoma samples were classified into three subgroups on the basis of a necroptosis gene set. These subgroups were subjected to a prognostic survival analysis, and the greatest differences were observed between subgroups C1 and C3. Between these subgroups, 28 necrotizing apoptosis-related genes were significantly differently expressed. Among these, 16 necrotizing apoptosis-related genes were associated with cutaneous melanoma prognosis. Downscaling analysis and prognostic modeling using the least absolute shrinkage and selection operator analysis yielded nine pivotal genes and revealed phosphoglycerate translocase 5 (PGAM5) as the key gene. Then, qRT-PCR was used to verify the expression level of PGAM5. The results showed that PGAM5 was highly expressed in cutaneous melanoma tissues. In this study, a bioinformatics approach was used to identify PGAM5, a biomarker whose high expression is associated with the poor prognosis of cutaneous melanoma.

Necroptosis pathways in tumorigenesis

Necroptosis is a caspase-independent form of programmed cell death executed by the receptor interacting protein kinase 1 (RIPK1)-RIPK3-mixed lineage kinase domain-like protein (MLKL) signaling cascade, deregulation of which can cause various human diseases including cancer. Escape from programmed cell death is a hallmark of cancer, leading to uncontrolled growth and drug resistance. Therefore, it is crucial to further understand whether necroptosis plays a key role in therapeutic resistance. In this review, we summarize the recent findings of the link between necroptosis and cancer, and discuss that targeting necroptosis is a new strategy to overcome apoptosis resistance in tumor therapy.

Ferroptosis, necroptosis, and pyroptosis in the tumor microenvironment: Perspectives for immunotherapy of SCLC

Small cell lung cancer (SCLC) is an aggressive form of lung cancer characterized by dismal prognosis. Although SCLC may initially respond well to platinum-based chemotherapy, it ultimately relapses and is almost universally resistant to this treatment. Immune checkpoint inhibitors (ICIs) have been approved as the first- and third-line therapeutic regimens for extensive-stage or relapsed SCLC, respectively. Despite this, only a minority of patients with SCLC respond to ICIs partly due to a lack of tumor-infiltrating lymphocytes (TILs). Transforming the immune "cold" tumors into "hot" tumors that are more likely to respond to ICIs is the main challenge for SCLC therapy. Ferroptosis, necroptosis, and pyroptosis represent the newly discovered immunogenic cell death (ICD) forms. Promoting ICD may alter the tumor microenvironment (TME) and the influx of TILs, and combination of their inducers and ICIs plays a synergistical role in enhancing antitumor effects. Nevertheless, the combination of the above two modalities has not been systematically discussed in SCLC therapy. In the present review, we summarize the roles of distinct ICD mechanisms on antitumor immunity and recent advances of ferroptosis-, necroptosis- and pyroptosis-inducing agents, and present perspectives on these cell death mechanisms in immunotherapy of SCLC.

Constructing and Validating a Pyroptosis-Related Genes Prognostic Signature for Stomach Adenocarcinoma and Immune Infiltration: Potential Biomarkers for Predicting the Overall Survival

Background

Stomach adenocarcinoma (STAD) is a kind of cancer that begins in the stomach cells and has a poor overall survival rate. Following resection surgery, chemotherapy has been suggested as a curative method for stomach cancer. However, it is ineffective. Pyroptosis, a kind of inflammatory programmed cell death, has been shown to play a significant role in the development and progression of STAD. However, whether pyroptosis-related genes (PRGs) can be utilized to predict the diagnosis and prognosis of gastric cancer remains unknown.

Method

The research measured at predictive PRGs in STAD samples from TCGA and GEO. Lasso regression was used to build the prediction model. Coexpression analysis revealed that gene expression was linked to pyroptosis. PRGs were found to be overexpressed in high-risk individuals, implying that they could be used in a model to predict STAD prognosis.

Result

Immunological and tumor-related pathways were discovered using GSEA. In STAD patients, the genes GPX3, PDGFRL, RGS2, and SERPINE1 may be connected to the cancer process. The levels of expression also differed between the two risk groups.

Conclusion

The purpose of this study is to identify and verify STAD-associated PRGs that can effectively guide prognosis and the immunological milieu in STAD patients as well as offer evidence for the development of pyroptosis-related molecularly targeted therapeutics. Therefore, PRGs and the link between immunological and PRGs in STAD may be therapeutic targets.

Construction and validation model of necroptosis-related gene signature associates with immunity for osteosarcoma patients

Osteosarcoma is the most common malignant tumor in children and adolescents and its diagnosis and treatment still need to be improved. Necroptosis has been associated with many malignancies, but its significance in diagnosing and treating osteosarcoma remains unclear. The objective is to establish a predictive model of necroptosis-related genes (NRGs) in osteosarcoma for evaluating the tumor microenvironment and new targets for immunotherapy. In this study, we download the osteosarcoma data from the TARGET and GEO websites and the average muscle tissue data from GTEx. NRGs were screened by Cox regression analysis. We constructed a prediction model through nonnegative matrix factorization (NMF) clustering and the least absolute shrinkage and selection operator (LASSO) algorithm and verified it with a validation cohort. Kaplan–Meier survival time, ROC curve, tumor invasion microenvironment and CIBERSORT were assessed. In addition, we establish nomograms for clinical indicators and verify them by calibration evaluation. The underlying mechanism was explored through the functional enrichment analysis. Eight NRGs were screened for predictive model modeling. NRGs prediction model through NMF clustering and LASSO algorithm was established. The survival, ROC and tumor microenvironment scores showed significant statistical differences among subgroups (P < 0.05). The validation model further verifies it. By nomogram and calibration, we found that metastasis and risk score were independent risk factors for the poor prognosis of osteosarcoma. GO and KEGG analyses demonstrate that the genes of osteosarcoma cluster in inflammatory, apoptotic and necroptosis signaling pathways. The significant role of the correlation between necroptosis and immunity in promoting osteosarcoma may provide a novel insight into detecting molecular mechanisms and targeted therapy.

Targeting necroptosis as an alternative strategy in tumor treatment: From drugs to nanoparticles

Over last decades, most antitumor therapeutic strategies have focused on apoptosis, however, apoptosis resistance and immunological silence usually led to treatment failure. In this sense, triggering other programmed cell death such as necroptosis may achieve a better therapeutic efficacy and has gained widespread attentions in tumor therapy. Studies in this field have identified several types of necroptosis modulators and highlighted the therapeutic potential of necroptotic cell death in cancer. Nanoparticles further provide possibilities to improve therapeutic outcomes as an efficient drug delivery system, facilitating tumor targeting and controlled cargo release. Furthermore, some nanoparticles themselves can trigger/promote programmed necrosis through hyperthermia, ultrasound and autophagy blockage. These investigations have entered necroptosis for consideration as a promising strategy for tumor therapy, though numerous challenges remain and clinical applications are still distant. In this review, we would briefly introduce molecular mechanism and characteristics of necroptosis, and then summarize recent progress of programmed necrosis and their inducers in tumor therapy. Furthermore, the antitumor strategies that take advantages of nanoparticles to induce necroptosis are also discussed.

Characterization of Necroptosis-Related Molecular Subtypes and Therapeutic Response in Lung Adenocarcinoma

Lung adenocarcinoma (LUAD) is one of the most common malignant tumors with high morbidity and mortality and is usually associated with therapeutic resistance and poor prognosis because of individual biological heterogeneity. There is an unmet need to screen for reliable parameters, especially immunotherapy-related biomarkers to predict the patient’s outcomes. Necroptosis is a special caspase-independent form of necrotic cell death associated with the pathogenesis, progression, and prognosis of multiple tumors but the potential connection between necroptosis-related genes (NRGs) and LUAD still remains unclear. In this study, we expounded mutational and transcriptional alterations of 67 NRGs in 522 LUAD samples and proposed a consensus-clustering subtype of these patients into two cohorts with distinct immunological and clinical prognosis characteristics. Cluster B patients were associated with a better prognosis and characterized by relatively lower expression of NRGs, higher immune scores in the tumor microenvironment (TME), more mild clinical stages, and downregulated expression of immunotherapy checkpoints. Subsequently, the NRG score was further established to predict the overall survival (OS) of LUAD patients using univariate Cox, LASSO, and multivariate Cox regression analyses. The immunological characteristics and potential predictive capability of NRG scores were further validated by 583 LUAD patients in external datasets. In addition to better survival and immune-activated conditions, low-NRG-score cohorts exhibited a significant positive correlation with the mRNA stem index (mRNAsi) and tumor mutation burden (TMB) levels. Combined with classical clinical characteristics and NRG scores, we successfully defined a novel necroptosis-related nomogram to accurately predict the 1/3/5-year survival rate of individual LUAD patients, and the potential predictive capability was further estimated and validated in multiple test datasets with high AUC values. Integrated transcriptomic analysis helps us seek vital NRGs and supplements a novel clinical application of NRG scores in predicting the overall survival and therapeutic benefits for LUAD patients.

IFNAR blockade synergizes with oncolytic VSV to prevent virus-mediated PD-L1 expression and promote antitumor T cell activity

Oncolytic virotherapies have shown excellent promise in a variety of cancers by promoting antitumor immunity. However, the effects of oncolytic virus-mediated type I interferon (IFN-I) production on antitumor immunity remain unclear. Recent reports have highlighted immunosuppressive functions of IFN-I in the context of checkpoint inhibitor and cell-based therapies. In this study, we demonstrate that oncolytic virus-induced IFN-I promotes the expression of PD-L1 in tumor cells and leukocytes in a IFN receptor (IFNAR)-dependent manner. Inhibition of IFN-I signaling using a monoclonal IFNAR antibody decreased IFN-I-induced PD-L1 expression and promoted tumor-specific T cell effector responses when combined with oncolytic virotherapy. Furthermore, IFNAR blockade improved therapeutic response to oncolytic virotherapy in a manner comparable with PD-L1 blockade. Our study highlights a critical immunosuppressive role of IFN-I on antitumor immunity and uses a combination strategy that improves the response to oncolytic virotherapy.

A Combination of Chemotherapy and Oncolytic Virotherapy Sensitizes Colorectal Adenocarcinoma to Immune Checkpoint Inhibitors in a cDC1-Dependent Manner

Immune checkpoint therapy has shown great promise in the treatment of cancers with a high mutational burden, such as mismatch repair-deficient colorectal carcinoma (dMMR CRC). However, many patients fail to respond to immune checkpoint therapy. Using a mouse model of dMMR CRC, we demonstrated that tumors can be further sensitized to immune checkpoint therapy by using a combination of low-dose chemotherapy and oncolytic HSV-1. This combination induced the infiltration of CD8+ and CD4+ T cells into the tumor and the upregulation of gene signatures associated with the chemoattraction of myeloid cell subsets. When combined with immune checkpoint therapy, the combination promoted the infiltration of activated type 1 conventional dendritic cells (cDC1s) into the tumor. Furthermore, we found this combination strategy to be dependent on cDC1s, and its therapeutic efficacy to be abrogated in cDC1-deficient Batf3-/- mice. Thus, we demonstrated that the adjuvanticity of dMMR CRCs can be improved by combining low-dose chemotherapy and oncolytic HSV-1 in a cDC1-dependent manner.

Immunogenic ferroptosis and where to find it?

Ferroptosis is a recently discovered form of regulated cell death that is morphologically, genetically, and biochemically distinct from apoptosis and necroptosis, and its potential use in anticancer therapy is emerging. The strong immunogenicity of (early) ferroptotic cancer cells broadens the current concept of immunogenic cell death and opens up new possibilities for cancer treatment. In particular, induction of immunogenic ferroptosis could be beneficial for patients with cancers resistant to apoptosis and necroptosis. However, ferroptotic cancer cells may be a rich source of oxidized lipids, which contribute to decreased phagocytosis and antigen cross-presentation by dendritic cells and thus may favor tumor evasion. This could explain the non-immunogenicity of late ferroptotic cells. Besides the presence of lactate in the tumor microenvironment, acidification and hypoxia are essential factors promoting ferroptosis resistance and affecting its immunogenicity. Here, we critically discuss the crucial mediators controlling the immunogenicity of ferroptosis that modulate the induction of antitumor immunity. We emphasize that it will be necessary to also identify the tolerogenic (ie, immunosuppressive) nature of ferroptosis, which can lead to tumor evasion.

Regulation of the Immune Checkpoint Indoleamine 2,3-Dioxygenase Expression by Epstein-Barr Virus

Epstein-Barr virus (EBV) is an oncovirus ubiquitously distributed and associated with different types of cancer. The reason why only a group of infected people develop cancer is still unknown. EBV-associated cancers represent about 1.8% of all cancer deaths worldwide, with more than 150,000 new cases of cancer being reported annually. Since EBV-associated cancers are described as more aggressive and more resistant to the usual treatment compared to EBV-negative ones, the recent introduction of monoclonal antibodies (mAbs) targeting immune checkpoints (ICs) in the treatment of cancer patients represents a possible therapy for EBV-associated diseases. However, the current mAb therapies available still need improvement, since a group of patients do not respond well to treatment. Therefore, the main objective of this review is to summarize the progress made regarding the contribution of EBV infection to the expression of the IC indoleamine 2,3-dioxygenase (IDO) thus far. This IC has the potential to be used as a target in new immune therapies, such as mAbs. We hope that this work helps the development of future immunotherapies, improving the prognosis of EBV-associated cancer patients.

Immune checkpoint blockade in triple negative breast cancer influenced by B cells through myeloid-derived suppressor cells

Triple negative breast cancer holds a dismal clinical outcome and as such, patients routinely undergo aggressive, highly toxic treatment regimens. Clinical trials for TNBC employing immune checkpoint blockade in combination with chemotherapy show modest prognostic benefit, but the percentage of patients that respond to treatment is low, and patients often succumb to relapsed disease. Here, we show that a combination immunotherapy platform utilizing low dose chemotherapy (FEC) combined with oncolytic virotherapy (oHSV-1) increases tumor-infiltrating lymphocytes, in otherwise immune-bare tumors, allowing 60% of mice to achieve durable tumor regression when treated with immune checkpoint blockade. Whole-tumor RNA sequencing of mice treated with FEC + oHSV-1 shows an upregulation of B cell receptor signaling pathways and depletion of B cells prior to the start of treatment in mice results in complete loss of therapeutic efficacy and expansion of myeloid-derived suppressor cells. Additionally, RNA sequencing data shows that FEC + oHSV-1 suppresses genes associated with myeloid-derived suppressor cells, a key population of cells that drive immune escape and mediate therapeutic resistance. These findings highlight the importance of tumor-infiltrating B cells as drivers of antitumor immunity and their potential role in the regulation of myeloid-derived suppressor cells.

Tumor necroptosis is correlated with a favorable immune cell signature and programmed death-ligand 1 expression in cholangiocarcinoma

Necroptosis, a regulated form of necrosis, has emerged as a novel therapeutic strategy that could enhance cancer immunotherapy. However, its role in tumorigenesis is still debated because recent studies have reported both anti- and pro-tumoral effects. Here, we aimed to systematically evaluate the associations between tumor necroptosis (mixed lineage kinase domain-like protein, MLKL; phosphorylated MLKL, pMLKL; and receptor-interacting protein kinase 1-receptor-interacting protein kinase 3, RIPK1-RIPK3 interaction) and tumor-infiltrating immune cells (CD8+ and FOXp3+ T cells and CD163+ M2 macrophages) and tumor PD-L1 by immunohistochemistry in 88 cholangiocarcinoma (CCA) patients who had undergone surgical resection. Their associations with clinicopathological characteristics, survival data, and prognosis were evaluated. MLKL was found to be an unfavorable prognostic factor (p-value = 0.023, HR = 2.070) and was inversely correlated with a clinically favorable immune cell signature (high CD8+/high FOXp3+/low CD163+). Both pMLKL and RIPK1-RIPK3 interaction were detected in CCA primary tissues. In contrast to MLKL, pMLKL status was significantly positively correlated with a favorable immune signature (high CD8+/high FOXp3+/low CD163+) and PD-L1 expression. Patients with high pMLKL-positive staining were significantly associated with an increased abundance of CD8+ T cell intratumoral infiltration (p-value = 0.006). Patients with high pMLKL and PD-L1 expressions had a longer overall survival (OS). The results from in vitro experiments showed that necroptosis activation in an RMCCA-1 human CCA cell line selectively promoted proinflammatory cytokine and chemokine expression. Jurkat T cells stimulated with necroptotic RMCCA-1-derived conditioned medium promoted PD-L1 expression in RMCCA-1. Our findings demonstrated the differential associations of necroptosis activation (pMLKL) and MLKL with a clinically favorable immune signature and survival rates and highlighted a novel therapeutic possibility for combining a necroptosis-based therapeutic approach with immune checkpoint inhibitors for more efficient treatment of CCA patients.

Tumor Heterogeneity: A Great Barrier in the Age of Cancer Immunotherapy

Throughout the history of oncology research, tumor heterogeneity has been a major hurdle for the successful treatment of cancer. As a result of aberrant changes in the tumor microenvironment such as high mutational burden, hypoxic conditions and abnormal vasculature, several malignant subpopulations often exist within a single tumor mass. Therapeutic intervention can also increase selective pressure towards subpopulations with acquired resistance. This phenomenon is often the cause of relapse in previously responsive patients, drastically changing the expected outcome of therapy. In the case of cancer immunotherapy, tumor heterogeneity is a substantial barrier as acquired resistance often takes the form of antigen escape and immunosuppression. In an effort to combat intrinsic resistance mechanisms, therapies are often combined as a multi-pronged approach to target multiple pathways simultaneously. These multi-therapy regimens have long been a mainstay of clinical oncology with chemotherapy cocktails but are more recently being investigated in the emerging landscape of immunotherapy. Furthermore, as high throughput technology becomes more affordable and accessible, researchers continue to deepen their understanding of the factors that influence tumor heterogeneity and shape the TME over the course of treatment regimens. In this review, we will investigate the factors that give rise to tumor heterogeneity and the impact it has on the field of immunotherapy. We will discuss how tumor heterogeneity causes resistance to various treatments and review the strategies currently being employed to overcome this challenging clinical hurdle. Finally, we will outline areas of research that should be prioritized to gain a better understanding of tumor heterogeneity and develop appropriate solutions.