Inhibiting TGF-beta signaling preserves the function of highly activated, in vitro expanded natural killer cells in AML and colon cancer models

Types of cell death and their relations to host immunological pathways

Various immune pathways have been identified in the host, including TH1, TH2, TH3, TH9, TH17, TH22, TH1-like, and THαβ immune reactions. While TH2 and TH9 responses primarily target multicellular parasites, host immune pathways directed against viruses, intracellular microorganisms (such as bacteria, protozoa, and fungi), and extracellular microorganisms can employ programmed cell death mechanisms to initiate immune responses or execute effective strategies for pathogen elimination. The types of programmed cell death involved include apoptosis, autophagy, pyroptosis, ferroptosis, necroptosis, and NETosis. Specifically, apoptosis is associated with host anti-virus eradicable THαβ immunity, autophagy with host anti-virus tolerable TH3 immunity, pyroptosis with host anti-intracellular microorganism eradicable TH1 immunity, ferroptosis with host anti-intracellular microorganism tolerable TH1-like immunity, necroptosis with host anti-extracellular microorganism eradicable TH22 immunity, and NETosis with host anti-extracellular microorganism tolerable TH17 immunity.

Integrating single-cell transcriptomics and machine learning to predict breast cancer prognosis: A study based on natural killer cell-related genes

Breast cancer (BC) is the most commonly diagnosed cancer in women globally. Natural killer (NK) cells play a vital role in tumour immunosurveillance. This study aimed to establish a prognostic model using NK cell-related genes (NKRGs) by integrating single-cell transcriptomic data with machine learning. We identified 44 significantly expressed NKRGs involved in cytokine and T cell-related functions. Using 101 machine learning algorithms, the Lasso + RSF model showed the highest predictive accuracy with nine key NKRGs. We explored cell-to-cell communication using CellChat, assessed immune-related pathways and tumour microenvironment with gene set variation analysis and ssGSEA, and observed immune components by HE staining. Additionally, drug activity predictions identified potential therapies, and gene expression validation through immunohistochemistry and RNA-seq confirmed the clinical applicability of NKRGs. The nomogram showed high concordance between predicted and actual survival, linking higher tumour purity and risk scores to a reduced immune score. This NKRG-based model offers a novel approach for risk assessment and personalized treatment in BC, enhancing the potential of precision medicine.

Progress on immuno-microenvironment and immune-related therapies in patients with pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is an indolent malignant syndrome. The standard treatment for PMP is cytoreductive surgery combined with intraperitoneal hyperthermic chemotherapy (CRS + HIPEC). However, the high recurrence rate and latent clinical symptoms and signs are major obstacles to further improving clinical outcomes. Moreover, patients in advanced stages receive little benefit from CRS + HIPEC due to widespread intraperitoneal metastases. Another challenge in PMP treatment involves the progressive sclerosis of PMP cell-secreted mucus, which is often increased due to activating mutations in the gene coding for guanine nucleotide-binding protein alpha subunit (GNAS). Consequently, the development of other PMP therapies is urgently needed. Several immune-related therapies have shown promise, including the use of bacterium-derived non-specific immunogenic agents, radio-immunotherapeutic agents, and tumor cell-derived neoantigens, but a well-recognized immunotherapy has not been established. In this review the roles of GNAS mutations in the promotion of mucin secretion and disease development are discussed. In addition, the immunologic features of the PMP microenvironment and immune-associated treatments are discussed to summarize the current understanding of key features of the disease and to facilitate the development of immunotherapies.

TGF-β Modulated Pathways in Colorectal Cancer: New Potential Therapeutic Opportunities

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide, with 20% of patients presenting with metastatic disease at diagnosis. TGF-β signaling plays a crucial role in various cellular processes, including growth, differentiation, apoptosis, epithelial-mesenchymal transition (EMT), regulation of the extracellular matrix, angiogenesis, and immune responses. TGF-β signals through SMAD proteins, which are intracellular molecules that transmit TGF-β signals from the cell membrane to the nucleus. Alterations in the TGF-β pathway and mutations in SMAD proteins are common in metastatic CRC (mCRC), making them critical factors in CRC tumorigenesis. This review first analyzes normal TGF-β signaling and then investigates its role in CRC pathogenesis, highlighting the mechanisms through which TGF-β influences metastasis development. TGF-β promotes neoangiogenesis via VEGF overexpression, pericyte differentiation, and other mechanisms. Additionally, TGF-β affects various elements of the tumor microenvironment, including T cells, fibroblasts, and macrophages, promoting immunosuppression and metastasis. Given its strategic role in multiple processes, we explored different strategies to target TGF-β in mCRC patients, aiming to identify new therapeutic options.

Unveiling mitochondrial and ribosomal gene deregulation and tumor microenvironment dynamics in acute myeloid leukemia

Acute myeloid leukemia (AML) is a malignant clonal hematopoietic disease with a poor prognosis. Understanding the interaction between leukemic cells and the tumor microenvironment (TME) can help predict the prognosis of leukemia and guide its treatment. Re-analyzing the scRNA-seq data from the CSC and G20 cohorts, using a Python-based pipeline including machine-learning-based scVI-tools, recapitulated the distinct hierarchical structure within the samples of AML patients. Weighted correlation network analysis (WGCNA) was conducted to construct a weighted gene co-expression network and to identify gene modules primarily focusing on hematopoietic stem cells (HSCs), multipotent progenitors (MPPs), and natural killer (NK) cells. The analysis revealed significant deregulation in gene modules associated with aerobic respiration and ribosomal/cytoplasmic translation. Cell-cell communications were elucidated by the CellChat package, revealing an imbalance of activating and inhibitory immune signaling pathways. Interception of genes upregulated in leukemic HSCs & MPPs as well as in NKG2A-high NK cells was used to construct prognostic models. Normal Cox and artificial neural network models based on 10 genes were developed. The study reveals the deregulation of mitochondrial and ribosomal genes in AML patients and suggests the co-occurrence of stimulatory and inhibitory factors in the AML TME.

Natural killer cells in cancer immunotherapy

Natural killer (NK) cells, as innate lymphocytes, possess cytotoxic capabilities and engage target cells through a repertoire of activating and inhibitory receptors. Particularly, natural killer group 2, member D (NKG2D) receptor on NK cells recognizes stress-induced ligands-the MHC class I chain-related molecules A and B (MICA/B) presented on tumor cells and is key to trigger the cytolytic response of NK cells. However, tumors have developed sophisticated strategies to evade NK cell surveillance, which lead to failure of tumor immunotherapy. In this paper, we summarized these immune escaping strategies, including the downregulation of ligands for activating receptors, upregulation of ligands for inhibitory receptors, secretion of immunosuppressive compounds, and the development of apoptosis resistance. Then, we focus on recent advancements in NK cell immune therapies, which include engaging activating NK cell receptors, upregulating NKG2D ligand MICA/B expression, blocking inhibitory NK cell receptors, adoptive NK cell therapy, chimeric antigen receptor (CAR)-engineered NK cells (CAR-NK), and NKG2D CAR-T cells, especially several vaccines targeting MICA/B. This review will inspire the research in NK cell biology in tumor and provide significant hope for improving cancer treatment outcomes by harnessing the potent cytotoxic activity of NK cells.

Advances in CAR-NK cell therapy for hematological malignancies

Chimeric antigen receptor T (CAR-T) cell therapy has revolutionized the treatment of hematological malignancies, demonstrably improving patient outcomes and prognosis. However, its application has introduced new challenges, such as safety concerns, off-target toxicities, and significant costs. Natural killer (NK) cells are crucial components of the innate immune system, capable of eliminating tumor cells without prior exposure to specific antigens or pre-activation. This inherent advantage complements the limitations of T cells, making CAR-NK cell therapy a promising avenue for hematological tumor immunotherapy. In recent years, preclinical and clinical studies have yielded preliminary evidence supporting the safety and efficacy of CAR-NK cell therapy in hematological malignancies, paving the way for future advancements in immunotherapy. This review aims to succinctly discuss the characteristics, significant therapeutic progress, and potential challenges associated with CAR-NK cell therapy.

Memory-like differentiation enhances NK cell responses against colorectal cancer

Metastatic (m) colorectal cancer (CRC) is an incurable disease with a poor prognosis and thus remains an unmet clinical need. Immune checkpoint blockade (ICB)-based immunotherapy is effective for mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) mCRC patients, but it does not benefit the majority of mCRC patients. NK cells are innate lymphoid cells with potent effector responses against a variety of tumor cells but are frequently dysfunctional in cancer patients. Memory-like (ML) NK cells differentiated after IL-12/IL-15/IL-18 activation overcome many challenges to effective NK cell anti-tumor responses, exhibiting enhanced recognition, function, and in vivo persistence. We hypothesized that ML differentiation enhances the NK cell responses to CRC. Compared to conventional (c) NK cells, ML NK cells displayed increased IFN-γ production against both CRC cell lines and primary patient-derived CRC spheroids. ML NK cells also exhibited improved killing of CRC target cells in vitro in short-term and sustained cytotoxicity assays, as well as in vivo in NSG mice. Mechanistically, enhanced ML NK cell responses were dependent on the activating receptor NKG2D as its blockade significantly decreased ML NK cell functions. Compared to cNK cells, ML NK cells exhibited greater antibody-dependent cytotoxicity when targeted against CRC by cetuximab. ML NK cells from healthy donors and mCRC patients exhibited increased anti-CRC responses. Collectively, our findings demonstrate that ML NK cells exhibit enhanced responses against CRC targets, warranting further investigation in clinical trials for mCRC patients, including those who have failed ICB.

Prognostic and predictive role of immune microenvironment in colorectal cancer

Colorectal cancer (CRC) represents a molecularly heterogeneous disease and one of the most frequent causes of cancer-related death worldwide. The traditional classification of CRC is based on pathomorphological and molecular characteristics of tumor cells (mucinous, ring-cell carcinomas, etc.), analysis of mechanisms of carcinogenesis involved (chromosomal instability, microsatellite instability, CpG island methylator phenotype) and mutational statuses of commonly altered genes (KRAS, NRAS, BRAF, APC, etc.), as well as expression signatures (CMS 1-4). It is also suggested that the tumor microenvironment is a key player in tumor progression and metastasis in CRC. According to the latest data, the immune microenvironment can also be predictive of the response to immune checkpoint inhibitors. In this review, we highlight how the immune environment influences CRC prognosis and sensitivity to systemic therapy.

Chimeric antigen receptor-based natural killer cell immunotherapy in cancer: from bench to bedside

Immunotherapy has rapidly evolved in the past decades in the battle against cancer. Chimeric antigen receptor (CAR)-engineered T cells have demonstrated significant success in certain hematologic malignancies, although they still face certain limitations, including high costs and toxic effects. Natural killer cells (NK cells), as a vital component of the immune system, serve as the "first responders" in the context of cancer development. In this literature review, we provide an updated understanding of NK cell development, functions, and their applications in disease therapy. Furthermore, we explore the rationale for utilizing engineered NK cell therapies, such as CAR-NK cells, and discuss the differences between CAR-T and CAR-NK cells. We also provide insights into the key elements and strategies involved in CAR design for engineered NK cells. In addition, we highlight the challenges currently encountered and discuss the future directions in NK cell research and utilization, including pre-clinical investigations and ongoing clinical trials. Based on the outstanding antitumor potential of NK cells, it is highly likely that they will lead to groundbreaking advancements in cancer treatment in the future.

It's high-time to re-evaluate the value of induced-chemotherapy for reinforcing immunotherapy in colorectal cancer

Immunotherapy has made significant advances in the treatment of colorectal cancer (CRC), revolutionizing the therapeutic landscape and highlighting the indispensable role of the tumor immune microenvironment. However, some CRCs have shown poor response to immunotherapy, prompting investigation into the underlying reasons. It has been discovered that certain chemotherapeutic agents possess immune-stimulatory properties, including the induction of immunogenic cell death (ICD), the generation and processing of non-mutated neoantigens (NM-neoAgs), and the B cell follicle-driven T cell response. Based on these findings, the concept of inducing chemotherapy has been introduced, and the combination of inducing chemotherapy and immunotherapy has become a standard treatment option for certain cancers. Clinical trials have confirmed the feasibility and safety of this approach in CRC, offering a promising method for improving the efficacy of immunotherapy. Nevertheless, there are still many challenges and difficulties ahead, and further research is required to optimize its use.

Chimeric antigen receptor engineered natural killer cells for cancer therapy

Natural killer (NK) cells, a unique component of the innate immune system, are inherent killers of stressed and transformed cells. Based on their potent capacity to kill cancer cells and good tolerance of healthy cells, NK cells have been successfully employed in adoptive cell therapy to treat cancer patients. In recent years, the clinical success of chimeric antigen receptor (CAR)-T cells has proven the vast potential of gene-manipulated immune cells as the main force to fight cancer. Following the lessons learned from mature gene-transfer technologies and advanced strategies in CAR-T therapy, NK cells have been rapidly explored as a promising candidate for CAR-based therapy. An exponentially growing number of studies have employed multiple sources of CAR-NK cells to target a wide range of cancer-related antigens, showing remarkable outcomes and encouraging safety profiles. Clinical trials of CAR-NK cells have also shown their impressive therapeutic efficacy in the treatment of hematological tumors, but CAR-NK cell therapy for solid tumors is still in the initial stages. In this review, we present the favorable profile of NK cells as a potential platform for CAR-based engineering and then summarize the outcomes and strategies of CAR-NK therapies in up-to-date preclinical and clinical investigations. Finally, we evaluate the challenges remaining in CAR-NK therapy and describe existing strategies that can assist us in devising future prospective solutions.

A new approach to overcoming resistance to immunotherapy: nanotechnology

Immunotherapy for immune response has ushered in a new era of cancer treatment. In recent years, new immunotherapeutic agents have been introduced into clinical trials and even approved for marketing. However, the widespread use of immunotherapeutic agents faces an unavoidable challenge: immunotherapy does not work at all for some patients, or has good efficacy in the initial phase, but immunotherapy resistance develops within a short period of time, and immunotherapy can also cause serious adverse effects such as autoimmune inflammation and non-specific inflammation. How to enable patients to overcome drug resistance, reduce the toxic side effects of drugs, enhance patient compliance and improve patient survival has become a problem that clinicians have to face. The advent of nanotechnology provides an encouraging platform for immunotherapy. It can not only improve the bioavailability and stability of drugs and reduce toxic side effects, but also reduce resistance to immunotherapy. Here, we discuss these research advances and discuss potential challenges and future directions.

NK cells are never alone: crosstalk and communication in tumour microenvironments

Immune escape is a hallmark of cancer. The dynamic and heterogeneous tumour microenvironment (TME) causes insufficient infiltration and poor efficacy of natural killer (NK) cell-based immunotherapy, which becomes a key factor triggering tumour progression. Understanding the crosstalk between NK cells and the TME provides new insights for optimising NK cell-based immunotherapy. Here, we present new advances in direct or indirect crosstalk between NK cells and 9 specialised TMEs, including immune, metabolic, innervated niche, mechanical, and microbial microenvironments, summarise TME-mediated mechanisms of NK cell function inhibition, and highlight potential targeted therapies for NK-TME crosstalk. Importantly, we discuss novel strategies to overcome the inhibitory TME and provide an attractive outlook for the future.

Role of PCIF1-mediated 5'-cap N6-methyladeonsine mRNA methylation in colorectal cancer and anti-PD-1 immunotherapy

Adenosine N6-methylation (m6A) and N6,2'-O-dimethylation (m6Am) are regulatory modifications of eukaryotic mRNAs. m6Am formation is catalyzed by the methyl transferase phosphorylated CTD-interacting factor 1 (PCIF1); however, the pathophysiological functions of this RNA modification and PCIF1 in cancers are unclear. Here, we show that PCIF1 expression is upregulated in colorectal cancer (CRC) and negatively correlates with patient survival. CRISPR/Cas9-mediated depletion of PCIF1 in human CRC cells leads to loss of cell migration, invasion, and colony formation in vitro and loss of tumor growth in athymic mice. Pcif1 knockout in murine CRC cells inhibits tumor growth in immunocompetent mice and enhances the effects of anti-PD-1 antibody treatment by decreasing intratumoral TGF-β levels and increasing intratumoral IFN-γ, TNF-α levels, and tumor-infiltrating natural killer cells. We further show that PCIF1 modulates CRC growth and response to anti-PD-1 in a context-dependent mechanism with PCIF1 directly targeting FOS, IFITM3, and STAT1 via m6Am modifications. PCIF1 stabilizes FOS mRNA, which in turn leads to FOS-dependent TGF-β regulation and tumor growth. While during immunotherapy, Pcif1-Fos-TGF-β, as well as Pcif1-Stat1/Ifitm3-IFN-γ axes, contributes to the resistance of anti-PD-1 therapy. Collectively, our findings reveal a role of PCIF1 in promoting CRC tumorigenesis and resistance to anti-PD-1 therapy, supporting that the combination of PCIF1 inhibition with anti-PD-1 treatment is a potential therapeutic strategy to enhance CRC response to immunotherapy. Finally, we developed a lipid nanoparticles (LNPs) and chemically modified small interfering RNAs (CMsiRNAs)-based strategy to silence PCIF1 in vivo and found that this treatment significantly reduced tumor growth in mice. Our results therefore provide a proof-of-concept for tumor growth suppression using LNP-CMsiRNA to silence target genes in cancer.

Contribution of natural killer cells in innate immunity against colorectal cancer

Natural killer cells are members of the innate immune system and promote cytotoxic activity against tumor or infected cells independently from MHC recognition. NK cells are modulated by the expression of activator/inhibitory receptors. The ratio of this activator/inhibitory receptors is responsible for the cytotoxic activity of NK cells toward the target cells. Owing to the potent anti-tumor properties of NK cells, they are considered as interesting approach in tumor treatment. Colorectal cancer (CRC) is the second most common cause of death in the world and the incidence is about 2 million new cases per year. Metastatic CRC is accompanied by a poor prognosis with less than three years of overall survival. Chemotherapy and surgery are the most adopted treatments. Besides, targeted therapy and immune checkpoint blockade are novel approach to CRC treatment. In these patients, circulating NK cells are a prognostic marker. The main target of CRC immune cell therapy is to improve the tumor cell's recognition and elimination by immune cells. Adaptive NK cell therapy is the milestone to achieve the purpose. Allogeneic NK cell therapy has been widely investigated within clinical trials. In this review, we focus on the NK related approaches including CAR NK cells, cell-based vaccines, monoclonal antibodies and immunomodulatory drugs against CRC tumoral cells.

TGF-β Signaling in Metastatic Colorectal Cancer (mCRC): From Underlying Mechanism to Potential Applications in Clinical Development

Colorectal cancer (CRC) is a serious public health issue, and it has the leading incidence and mortality among malignant tumors worldwide. CRC patients with metastasis in the liver, lung or other distant sites always have poor prognosis. Thus, there is an urgent need to discover the underlying mechanisms of metastatic colorectal cancer (mCRC) and to develop optimal therapy for mCRC. Transforming growth factor-β (TGF-β) signaling plays a significant role in various physiologic and pathologic processes, and aberrant TGF-β signal transduction contributes to mCRC progression. In this review, we summarize the alterations of the TGF-β signaling pathway in mCRC patients, the functional mechanisms of TGF-β signaling, its promotion of epithelial-mesenchymal transition, its facilitation of angiogenesis, its suppression of anti-tumor activity of immune cells in the microenvironment and its contribution to stemness of CRC cells. We also discuss the possible applications of TGF-β signaling in mCRC diagnosis, prognosis and targeted therapies in clinical trials. Hopefully, these research advances in TGF-β signaling in mCRC will improve the development of new strategies that can be combined with molecular targeted therapy, immunotherapy and traditional therapies to achieve better efficacy and benefit mCRC patients in the near future.

How the Tumor Micromilieu Modulates the Recruitment and Activation of Colorectal Cancer-Infiltrating Lymphocytes

The successful treatment of advanced colorectal cancer disease still represents an insufficiently solved clinical challenge, which is further complicated by the fact that the majority of malignant colon tumors show only relatively low immunogenicity and therefore have only limited responsiveness to immunotherapeutic approaches, such as, for instance, the use of checkpoint inhibitors. As it has been well established over the past two decades that the local tumor microenvironment and, in particular, the quantity, quality, and activation status of intratumoral immune cells critically influence the clinical prognosis of patients diagnosed with colorectal cancer and their individual benefits from immunotherapy, the enhancement of the intratumoral accumulation of cytolytic effector T lymphocytes and other cellular mediators of the antitumor immune response has emerged as a targeted objective. For the future identification and clinical validation of novel therapeutic target structures, it will thus be essential to further decipher the molecular mechanisms and cellular interactions in the intestinal tumor microenvironment, which are crucially involved in immune cell recruitment and activation. In this context, our review article aims at providing an overview of the key chemokines and cytokines whose presence in the tumor micromilieu relevantly modulates the numeric composition and antitumor capacity of tumor-infiltrating lymphocytes.

Increased circulating TGF-β1 is associated with impairment in NK cell effector functions in metastatic melanoma patients

Transforming growth factor beta (TGF-β) plays a complex role in carcinogenesis. In 30 melanoma patients and 20 healthy controls (HC) we analysed functional and phenotypic characteristics of NK cells by Flow cytometry, gene expression of TGF-β1 in peripheral blood mononuclear cells by qPCR and serum and supernatant level of free TGF-β1 by ELISA. Melanoma patients had significantly higher serum level of circulatingTGF-β1 compared to HC, especially those with metastasis into the central nervous system (subclass M1d) and high LDH serum values. Melanoma patients compared to HC had significantly higher level of TGF-β1 gene in PBMC. TGF-β1 serum values negatively correlate with NK cell activity analysed by CD107a (degranulation marker), IFN-γ, NKG2D, and NKp46 in patients. Study shows the association of high level of TGF-β1 with NK cell inhibition in patients represents the main mechanism of tumour immune evasion. Targeting TGF-β may become an important cancer treatment for improving antitumor immunity.

NOX4 has the potential to be a biomarker associated with colon cancer ferroptosis and immune infiltration based on bioinformatics analysis

Background

Colon cancer (CC) is a common tumor, but its pathogenesis is still not well understood. Competitive endogenous RNA (ceRNA) theory, ferroptosis and tumor immune infiltration may be the mechanisms of the development of cancer. The purpose of the study is to seek genes connected with both immunity and ferroptosis, and provide important molecular basis for early noninvasive diagnosis and immunotherapy of CC.

Methods

We extracted messenger RNA (mRNA), microRNA (miRNA), and long noncoding RNA (lncRNA) data of CC from The Cancer Genome Atlas database (TCGA), identified the differentially expressed mRNA (DEmRNA), miRNA (DEmiRNA) and lncRNA (DElncRNA), then constructed a ceRNA network. Venn overlap analysis was used to identify genes associated with immunity and ferroptosis in ceRNA network. The expression and prognosis of target genes were analyzed via Gene Expression Profiling Interactive Analysis (GEPIA) and PrognoScan database, and we analysed the related functions and signaling pathways of target genes by enrichment analysis. The correlation between target genes and tumor immune infiltrating was explored by CIBERSORT and spearman correlation analysis. Finally, the expression of target genes was detected via quantitative reverse transcription-PCR (qRT-PCR) in CC and normal colon tissues.

Results

Results showed that there were 4 DElncRNA, 4 DEmiRNA and 126 DEmRNA in ceRNA network. NADPH oxidase 4 protein (NOX4) was a DEmRNA associated with immunity and ferroptosis in ceRNA network. NOX4 was highly expressed in CC and connected with unfavourable prognosis. NOX4 was obviously enriched in pathways connected with carcinogenesis and significantly correlated with six kinds of immune cells. Immune checkpoints and NOX4 spearman correlation analysis showed that the expression of NOX4 was positively related to programmed cell death protein 1 (PD-1)-PDCD1, programmed cell death-Ligand 1 (PD-L1)-CD274 and cytotoxic T-lymphocyte-associated protein 4 (CTLA4).

Conclusions

To conclude, our study suggests that NOX4 is associated with both ferroptosis and tumor immunity, and might be a biomarker associated with the carcinogenesis, prognosis of CC and a potential target of CC immunotherapy.

Advanced Cell Therapies for Glioblastoma

The sheer ubiquity of Gioblastoma (GBM) cases would lead you to believe that there should have been many opportunities for the discovery of treatments to successfully render it into remission. Unfortunately, its persistent commonality is due in large part to the fact that it is the most treatment-resistant tumors in adults. That completely changes the treatment plan of attack. Long established and accepted treatment therapies such as surgical resection, radiation, and aggressive chemotherapy, (and any combination thereof) have only confirmed that the disease lives up to its treatment-resistant reputation. To add to the seemingly insurmountable task of finding a cure, GBM has also proven to be a very stubborn and formidable opponent to newer immunotherapies. Across the board, regardless of the therapy combination, the five-year survival rate of GBM patients is still very poor at a heartbreaking 5.6%. Obviously, the present situation cannot be tolerated or deemed acceptable. The grave situation calls for researchers to be more innovative and find more efficient strategies to discover new and successful strategies to treat GBM. Inspired by researchers worldwide attempting to control GBM, we provide in this review a comprehensive overview of the many diverse cell therapies currently being used to treat GBM. An overview of the treatments include: CAR T cells, CAR NK cells, gamma-delta T cells, NKT cells, dendritic cells, macrophages, as well stem cell-based strategies. To give you the complete picture, we will discuss the efficacy, safety, and developmental stages, the mechanisms of action and the challenges of each of these therapies and detail their potential to be the next-generation immunotherapeutic to eliminate this dreadful disease.

Overcoming tumor resistance mechanisms in CAR-NK cell therapy

Despite the impressive results of autologous CAR-T cell therapy in refractory B lymphoproliferative diseases, CAR-NK immunotherapy emerges as a safer, faster, and cost-effective approach with no signs of severe toxicities as described for CAR-T cells. Permanently scrutinized for its efficacy, recent promising data in CAR-NK clinical trials point out the achievement of deep, high-quality responses, thus confirming its potential clinical use. Although CAR-NK cell therapy is not significantly affected by the loss or downregulation of its CAR tumor target, as in the case of CAR-T cell, a plethora of common additional tumor intrinsic or extrinsic mechanisms that could also disable NK cell function have been described. Therefore, considering lessons learned from CAR-T cell therapy, the emergence of CAR-NK cell therapy resistance can also be envisioned. In this review we highlight the processes that could be involved in its development, focusing on cytokine addiction and potential fratricide during manufacturing, poor tumor trafficking, exhaustion within the tumor microenvironment (TME), and NK cell short in vivo persistence on account of the limited expansion, replicative senescence, and rejection by patient’s immune system after lymphodepletion recovery. Finally, we outline new actively explored alternatives to overcome these resistance mechanisms, with a special emphasis on CRISPR/Cas9 mediated genetic engineering approaches, a promising platform to optimize CAR-NK cell function to eradicate refractory cancers.

Nanomedicines for Overcoming Cancer Drug Resistance

Clinically, cancer drug resistance to chemotherapy, targeted therapy or immunotherapy remains the main impediment towards curative cancer therapy, which leads directly to treatment failure along with extended hospital stays, increased medical costs and high mortality. Therefore, increasing attention has been paid to nanotechnology-based delivery systems for overcoming drug resistance in cancer. In this respect, novel tumor-targeting nanomedicines offer fairly effective therapeutic strategies for surmounting the various limitations of chemotherapy, targeted therapy and immunotherapy, enabling more precise cancer treatment, more convenient monitoring of treatment agents, as well as surmounting cancer drug resistance, including multidrug resistance (MDR). Nanotechnology-based delivery systems, including liposomes, polymer micelles, nanoparticles (NPs), and DNA nanostructures, enable a large number of properly designed therapeutic nanomedicines. In this paper, we review the different mechanisms of cancer drug resistance to chemotherapy, targeted therapy and immunotherapy, and discuss the latest developments in nanomedicines for overcoming cancer drug resistance.

Immunotherapy for Microsatellite Stable Colorectal Cancers: Challenges and Novel Therapeutic Avenues

With the development of immune checkpoint inhibitors, immunotherapy researchers have facilitated substantial progress for patients with mismatch repair deficient/microsatellite instability-high colorectal cancer, which has led to practice changes at a head-spinning pace. However, this benefit has not been translated into microsatellite stable colorectal cancer, which carries the hallmarks of chromosomal instability. So far, clinical trials have not shown any substantial clinical benefits of immune checkpoint inhibitor therapy for patients with microsatellite stable colorectal cancer, which has been disappointing. Recently, combinations of immune checkpoint inhibitors with tyrosine kinase inhibitors and targeted therapies have been investigated for potential synergistic effects that may increase antitumor activity in the tumor microenvironment and achieve more substantial clinical and radiologic responses. In this article, we discuss the current state of the science for the use of immune checkpoint inhibitors in microsatellite stable colorectal cancers, and we review the molecular underpinnings of inherited physiologic barriers for the delivery of effective immunotherapy. We also elaborate on existing therapeutic opportunities to convert microsatellite stable colorectal cancer into an "immune hot" cancer, which may define the future treatment paradigm of colorectal cancer for which there is a great unmet need.

Natural killer cells and acute myeloid leukemia: promises and challenges

Acute myeloid leukemia (AML) is considered as one of the most malignant conditions of the bone marrow. Over the past few decades, despite substantial progresses in the management of AML, relapse remission remains a major problem. Natural killer cells (NK cells) are known as a unique component of the innate immune system. Due to swift tumor detection, distinct cytotoxic action, and extensive immune interaction, NK cells have been used in various cancer settings for decades. It has been a growing knowledge of therapeutic magnitudes ranging from adoptive NK cell transfer to chimeric antigen receptor NK cells, aiming to achieve better therapeutic responses in patients with AML. In this article, the potentials of NK cells for treatment of AML are highlighted, and challenges for such therapeutic methods are discussed. In addition, the clinical application of NK cells, mainly in patients with AML, is pictured according to the existing evidence.

Comparable transforming growth factor beta-mediated immune suppression in ex vivo-expanded natural killer cells from cord blood and peripheral blood: implications for adoptive immunotherapy

T cell-based therapies like genetically modified immune cells expressing chimeric antigen receptors have shown robust anti-cancer activity in vivo, especially in patients with blood cancers. However, extending this approach to an "off-the-shelf" setting can be challenging, as allogeneic T cells carry a significant risk of graft-versus-host disease (GVHD). By contrast, allogeneic natural killer (NK) cells recognize malignant cells without the need for prior antigen exposure and have been used safely in multiple cancer settings without the risk of GVHD. However, similar to T cells, NK cell function is negatively impacted by tumor-induced transforming growth factor beta (TGF-β) secretion, which is a ubiquitous and potent immunosuppressive mechanism employed by most malignancies. Allogeneic NK cells for adoptive immunotherapy can be sourced from peripheral blood (PB) or cord blood (CB), and the authors' group and others have previously shown that ex vivo expansion and gene engineering can overcome CB-derived NK cells' functional immaturity and poor cytolytic activity, including in the presence of exogenous TGF-β.  However, a direct comparison of the effects of TGF-β-mediated immune suppression on ex vivo-expanded CB- versus PB-derived NK cell therapy products has not previously been performed. Here the authors show that PB- and CB-derived NK cells have distinctive gene signatures that can be overcome by ex vivo expansion. Additionally, exposure to exogenous TGF-β results in an upregulation of inhibitory receptors on NK cells, a novel immunosuppressive mechanism not previously described. Finally, the authors provide functional and genetic evidence that both PB- and CB-derived NK cells are equivalently susceptible to TGF-β-mediated immune suppression. The authors believe these results provide important mechanistic insights to consider when using ex vivo-expanded, TGF-β-resistant PB- or CB-derived NK cells as novel immunotherapy agents for cancer.

Update on the role and utility of extracellular vesicles in hematological malignancies

Extracellular vesicles (EVs) are membrane-surrounded cellular particles released by virtually any cell type, containing numerous bioactive molecules, including lipids, proteins, and nucleic acids. EVs act as a very efficient intercellular communication system by releasing their content into target cells, thus affecting their fate and influencing several biological processes. EVs are released both in physiological and pathological conditions, including several types of cancers. In hematological malignancies (HM), EVs have emerged as new critical players, contributing to tumor-to-stroma, stroma-to-tumor, and tumor-to-tumor cell communication. Therefore, EVs have been shown to play a crucial role in the pathogenesis and clinical course of several HM, contributing to tumor development, progression, and drug resistance. Furthermore, tumor EVs can reprogram the bone marrow (BM) microenvironment and turn it into a sanctuary, in which cancer cells suppress both the normal hematopoiesis and the immunological anti-tumor activity, conferring a therapy-resistant phenotype. Due to their physicochemical characteristics and pro-tumor properties, EVs have been suggested as new diagnostic biomarkers, therapeutic targets, and pharmacological nanocarriers. This review aims to provide an update on the pathogenetic contribution and the putative therapeutic utility of EVs in hematological diseases.

Innovative Strategies to Improve the Clinical Application of NK Cell-Based Immunotherapy

Natural killer cells constitute a part of the innate immune system that mediates an effective immune response towards virus-infected and malignant cells. In recent years, research has focused on exploring and advancing NK cells as an active immunotherapy platform. Despite major advances, there are several key challenges that need to be addressed for the effective translation of NK cell research to clinical applications. This review highlights some of these challenges and the innovative strategies being developed to overcome them, including in vitro expansion, in vivo persistence, infiltration to the tumor site, and prevention of exhaustion.

Challenges to the broad application of allogeneic natural killer cell immunotherapy of cancer

Natural killer (NK) cells are innate immune cells that recognize malignant cells through a wide array of germline-encoded receptors. Triggering of activating receptors results in cytotoxicity and broad immune system activation. The former is achieved through release of cytotoxic granules and presentation of death receptor ligands, while the latter is mediated by inflammatory cytokines, such as interferon-γ and tumor necrosis factor α. Early success with ex vivo activation of NK cells and adoptive transfer suggest they are a safe therapeutic with promising responses in advanced hematologic malignancies. In particular, adoptive NK cell therapies can serve as a 'bridge' to potentially curative allogeneic stem cell transplantation. In addition, strategies are being developed that expand large numbers of cells from limited starting material and mature NK cells from precursors. Together, these make 'off-the-shelf' NK cells possible to treat a wide range of cancers. Research efforts have focused on creating a range of tools that increase targeting of therapeutic NK cells toward cancer-from therapeutic antibodies that drive antibody-dependent cellular cytotoxicity, to chimeric antigen receptors. As these novel therapies start to show promise in clinical trials, the field is rapidly moving toward addressing other challenges that limit NK cell therapeutics and the goal to treat solid tumors. This review describes the state of therapeutic NK cell targeting of tumors; discusses the challenges that need to be addressed before NK cells can be applied as a wide-ranging treatment for cancer; and points to some of the innovations that are being developed to surmount these challenges. Suppressive cells in the tumor microenvironment pose a direct threat to therapeutic NK cells, through presentation of inhibitory ligands and secretion of suppressive cytokines and metabolites. The nutrient- and oxygen-starved conditions under which NK cells must function necessitate an understanding of therapeutic NK cell metabolism that is still emerging. Prior to these challenges, NK cells must find their way into and persist in the tumor itself. Finally, the desirability of a 'single-shot' NK cell treatment and the problems and benefits of a short-lived rejection-prone NK cellular product are discussed.

Natural killer cell-related gene signature predicts malignancy of glioma and the survival of patients

Background

Natural killer (NK) cells-based therapies are one of the most promising strategies against cancer. The aim of this study is to investigate the natural killer cell related genes and its prognostic value in glioma.

Methods

The Chinese Glioma Genome Atlas (CGGA) was used to develop the natural killer cell-related signature. Risk score was built by multivariate Cox proportional hazards model. A cohort of 326 glioma samples with whole transcriptome expression data from the CGGA database was included for discovery. The Cancer Genome Atlas (TCGA) datasets was used for validation. GO and KEGG were used to reveal the biological process and function associated with the natural killer cell-related signature. We also collected the clinical pathological features of patients with gliomas to analyze the association with tumor malignancy and patients’ survival.

Results

We screened for NK-related genes to build a prognostic signature, and identified the risk score based on the signature. We found that NK-related risk score was independent of various clinical factors. Nature-killer cell gene expression is correlated with clinicopathological features of gliomas. Innovatively, we demonstrated the tight relation between the risk score and immune checkpoints, and found NK-related risk score combined with PD1/PDL1 patients could predict the patient outcome.

Conclusion

Natural killer cell-related gene signature can predict malignancy of glioma and the survival of patients, these results might provide new view for the research of glioma malignancy and individual immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09230-y.

A Phase I study to determine maximum tolerated dose of ex vivo expanded natural killer cells derived from unrelated, HLA-disparate adult donors

The administration of allogeneic natural killer (NK) cells following a lymphodepleting chemotherapy regimen is emerging as a well-tolerated therapeutic approach in the management of various malignancies. Contrary to the expected complications of allogeneic T cell therapy, there remains no evidence of graft-versus-host disease (GVHD) mediated by NK cells in numerous clinical trials. On the contrary, preclinical and clinical studies suggest that NK cells do not induce GVHD and in fact may prevent its development following allogeneic hematopoietic cell transplantation (HCT). In this study, we sought to determine the maximum tolerated dose of non-HLA-matched donor NK cells derived from peripheral blood and ex vivo expanded using a novel feeder cell platform. In a single-center Phase I clinical trial using a 3 × 3 design, 9 subjects each received 2 infusions of NK cells 2 weeks apart following a preparative regimen of cyclophosphamide (60 mg/kg i.v.) and fludarabine (25 mg/m²/day i.v for 5 days). No exogenous cytokines were administered. NK cells were administered at 3 dose levels: 1 × 10⁷/kg, 2.5 × 10⁷/kg, and 5 × 10⁷/kg. Three subjects had myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML), and the other 6 subjects had colorectal carcinoma. Recipients were monitored over a 4-week period for GVHD as well as other adverse events and for persistence of donor NK cells in systemic circulation. Disease assessment was started at 28 days following the first NK cell infusion and continued until postinfusion day 100 or disease progression. In all 9 study subjects, there was no occurrence of GVHD and no dose-limiting toxicities that would warrant cohort expansion at any of the 3 planned cell dose levels. Low-level donor NK cell persistence was observed up to 4 weeks after the first NK cell infusion at all dose levels. The best observed response was a complete response with incomplete platelet recovery in a MDS subject who experienced disease relapse after prior allogeneic HCT. Other responses were stable disease in 1 subject with MDS and 2 subjects with colorectal cancer up to postinfusion day 100. This off-the-shelf, third-party NK cell product can be administered safely without inducing GVHD and exhibits in vivo persistence promoted by preparative lymphodepletion alone. The observed clinical responses could be enhanced by administration of exogenous cytokine support, as well as complementary approaches that promote NK cell function in the tumor microenvironment.

Cancer exosomes and natural killer cells dysfunction: biological roles, clinical significance and implications for immunotherapy

Tumor-derived exosomes (TDEs) play pivotal roles in several aspects of cancer biology. It is now evident that TDEs also favor tumor growth by negatively affecting anti-tumor immunity. As important sentinels of immune surveillance system, natural killer (NK) cells can recognize malignant cells very early and counteract the tumor development and metastasis without a need for additional activation. Based on this rationale, adoptive transfer of ex vivo expanded NK cells/NK cell lines, such as NK-92 cells, has attracted great attention and is widely studied as a promising immunotherapy for cancer treatment. However, by exploiting various strategies, including secretion of exosomes, cancer cells are able to subvert NK cell responses. This paper reviews the roles of TDEs in cancer-induced NK cells impairments with mechanistic insights. The clinical significance and potential approaches to nullify the effects of TDEs on NK cells in cancer immunotherapy are also discussed.

Generation and functional characterization of a multigene-modified NK101 cell line exerting diverse mechanisms of antitumor action

Clonal cell line-based, multigene-modified, off-the-shelf NK cell therapeutics are emerging as the new frontier of adoptive cellular immunotherapy. Here, we utilized a newly established NK cell line, NK101, as a backbone to derive multifaceted killer cells armored with various antitumor modalities through repeated cycles of genetic modification and clonal selection. First, NK101 cells were transduced with a tricistronic lentiviral vector expressing CD7, CD28, and cytosine deaminase (CD). The resulting cell line demonstrated enhanced cytotoxicity against B7⁺ tumors and exerted bystander killing effects on neighboring tumor cells upon 5-FC treatment. Second, engineered NK101 cells were again transduced with a bicistronic vector expressing membrane-bound interleukin-15 (mbIL-15) and dominant negative TGFβ type II receptor (DNTβRII). Ectopic expression of mbIL-15 resulted in further augmentation of lytic activities against all tested target cells by inducing upregulation of multiple activating receptors, while that of DNTβRII allowed the cells to maintain heightened cytotoxicity in the presence of TGFβ. Finally, dual-transduced NK101 cells were modified to express chimeric antigen receptors (CARs) targeting either a solid tumor antigen (EpCAM) or a hematologic tumor antigen (FLT3). The final engineered products not only demonstrated antigen-specific killing activities in vitro but also exerted strong tumor-inhibitory effects in preclinical models of metastatic solid tumor and hematologic malignancy. Notably, combined treatment with 5-FC further enhanced antitumor efficacy of engineered NK101 in the solid tumor model. Our results demonstrate successful generation of multigene-modified NK101 cell therapeutics exerting diverse mechanisms of antitumor action - activation receptor-mediated innate killing, antigen-specific killing, and bystander effect-mediated killing.

CAR-NK Cells: From Natural Basis to Design for Kill

Chimeric antigen receptors (CARs) are fusion proteins with an extracellular antigen recognition domain and numerous intracellular signaling domains that have been genetically modified. CAR-engineered T lymphocyte-based therapies have shown great success against blood cancers; however, potential fatal toxicity, such as in cytokine release syndrome, and high costs are some shortcomings that limit the clinical application of CAR-engineered T lymphocytes and remain to overcome. Natural killer (NK) cells are the focal point of current immunological research owing to their receptors that prove to be promising immunotherapeutic candidates for treating cancer. However, to date, manipulation of NK cells to treat malignancies has been moderately successful. Recent progress in the biology of NK cell receptors has greatly transformed our understanding of how NK cells recognize and kill tumor and infected cells. CAR-NK cells may serve as an alternative candidate for retargeting cancer because of their unique recognition mechanisms, powerful cytotoxic effects especially on cancer cells in both CAR-dependent and CAR-independent manners and clinical safety. Moreover, NK cells can serve as an ‘off-the-shelf product’ because NK cells from allogeneic sources can also be used in immunotherapies owing to their reduced risk of alloreactivity. Although ongoing fundamental research is in the beginning stages, this review provides an overview of recent developments implemented to design CAR constructs to stimulate NK activation and manipulate NK receptors for improving the efficiency of immunotherapy against cancer, summarizes the preclinical and clinical advances of CAR-NK cells against both hematological malignancies and solid tumors and confronts current challenges and obstacles of their applications. In addition, this review provides insights into prospective novel approaches that further enhance the efficiency of CAR-NK therapies and highlights potential questions that require to be addressed in the future.

Overcoming TGFβ-mediated immune evasion in cancer

Transforming growth factor-β (TGFβ) signalling controls multiple cell fate decisions during development and tissue homeostasis; hence, dysregulation of this pathway can drive several diseases, including cancer. Here we discuss the influence that TGFβ exerts on the composition and behaviour of different cell populations present in the tumour immune microenvironment, and the context-dependent functions of this cytokine in suppressing or promoting cancer. During homeostasis, TGFβ controls inflammatory responses triggered by exposure to the outside milieu in barrier tissues. Lack of TGFβ exacerbates inflammation, leading to tissue damage and cellular transformation. In contrast, as tumours progress, they leverage TGFβ to drive an unrestrained wound-healing programme in cancer-associated fibroblasts, as well as to suppress the adaptive immune system and the innate immune system. In consonance with this key role in reprogramming the tumour microenvironment, emerging data demonstrate that TGFβ-inhibitory therapies can restore cancer immunity. Indeed, this approach can synergize with other immunotherapies - including immune checkpoint blockade - to unleash robust antitumour immune responses in preclinical cancer models. Despite initial challenges in clinical translation, these findings have sparked the development of multiple therapeutic strategies that inhibit the TGFβ pathway, many of which are currently in clinical evaluation.

The Potential Applications of Stem Cells for Cancer Treatment

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Scientists encounter many obstacles in traditional cancer therapies, including the side effects on the healthy cells, drug resistance, tumor relapse, the short half-life of employed drugs in the blood circulation, and the improper delivery of drugs toward the tumor site. The unique traits of stem cells (SCs) such as self-renewal, differentiation, tumor tropism, the release of bioactive molecules, and immunosuppression have opened a new window for utilizing SCs as a novel tool in cancer treatment. In this regard, engineered SCs can secrete anti-cancer proteins or express enzymes used in suicide gene therapy which locally induce apoptosis in neoplastic cells via the bystander effect. These cells also stand as proper candidates to serve as careers for drug-loaded nanoparticles or to play suitable hosts for oncolytic viruses. Moreover, they harbor great potential to be employed in immunotherapy and combination therapy. However, tactful strategies should be devised to allow easier transplantation and protection of SCs from in vivo immune responses. In spite of the great hope concerning SCs application in cancer therapy, there are shortcomings and challenges to be addressed. This review tends to elaborate on recent advances on the various applications of SCs in cancer therapy and existing challenges in this regard.

NK cell upraise in the dark world of cancer stem cells

One of the obstacles in treating different cancers, especially solid tumors, is cancer stem cells (CSCs) with their ability in resistance to chemo/radio therapy. The efforts for finding advanced treatments to overcome these cells have led to the emergence of advanced immune cell-based therapy (AICBT). Today, NK cells have become the center of attention since they have been proved to show an appropriate cytotoxicity against different cancer types as well as the capability of detecting and killing CSCs. Attempts for reaching an off-the-shelf source of NK cells have been made and resulted in the emergence of chimeric antigen receptor natural killer cells (CAR-NK cells). The CAR technology has then been used for generating more cytotoxic and efficient NK cells, which has increased the hope for cancer treatment. Since utilizing this advanced technology to target CSCs have been published in few studies, the present study has focused on discussing the characteristics of CSCs, which are detected and targeted by NK cells, the advantages and restrictions of using CAR-NK cells in CSCs treatment and the probable challenges in this process.

Chemical screening identifies novel small molecule activators of natural killer cell cytotoxicity against cancer cells

Natural killer (NK) cells are cytotoxic lymphocytes that play a major role in the innate immune system. NK cells exhibit potent cytotoxic activity against cancer cells and virally infected cells without antigen priming. These unique cytotoxic properties make NK cells a promising therapeutic against cancer. Limitations of NK cell therapy include deficiencies in high clinical efficacy often due to a need for a high NK cell to target cell ratio to achieve effective killing. In order to address the suboptimal efficacy of current adoptive NK cell therapy, a high throughput screen (HTS) was designed and performed to identify drug-like compounds that increase NK cytotoxic activity against tumor cells without affecting the normal cells. This screen was performed in a 384-well plate format utilizing an expanded primary NK cell product and ovarian cancer cells as a target cell (TC) line. Of the 8000 diverse small molecules screened, 16 hits were identified (0.2% hit rate) based on both a robust Z (RZ) score < -3 and a greater than 10% increase in NK cell killing. A validation screen had a confirmation rate of 70%. Select compounds were further validated and characterized by additional cytotoxicity assays including activity against multiple blood cancer and solid tumor cell lines, with no effect on primary human T cells. This work demonstrates that high-throughput screening can be reliably used to identify compounds that increase NK tumoricidal activity in vitro that can be further investigated and translated for potential clinical application. Précis: Our work led to the identification of promising compound that potently increases NK cell-mediated killing of a variety of different cancer cells, but no impact on the killing of normal cells. This compound demonstrates the utility of this assay.

Exosomal lncRNA SNHG10 derived from colorectal cancer cells suppresses natural killer cell cytotoxicity by upregulating INHBC

BACKGROUND

Exosome-mediated crosstalk between cancer cells and immune cells contributes to tumor growth. In this study, we investigated the mechanism underlying the exosome-mediated immune escape of colorectal cancer (CRC) cells from natural killer (NK) cells via the transfer of long noncoding RNAs (lncRNAs).

METHODS

An epithelial-mesenchymal transition (EMT) model of SW480 cells was established by transforming growth factor beta (TGF-β), followed by the assessment of the effect of EMT-derived exosomes (EMT-exo) on the functions of NK cells. RNA sequencing was performed to identify exosomal lncRNAs and target genes. The function of exosomal lncRNAs in tumor growth was further verified in vivo.

RESULTS

EMT-exo suppressed the proliferation, cytotoxicity, IFN-γ production, and perforin-1 and granzyme B secretion of NK cells. RNA sequencing revealed that SNHG10 expression was upregulated in EMT-exo compared with that in non-EMT-exo. Moreover, SNHG10 expression was upregulated in tumor tissues in CRC, which was associated with poor prognosis. Overexpression of SNHG10 in exosomes (oe-lnc-SNHG10 exo) significantly suppressed the viability and cytotoxicity of NK cells. Transcriptome sequencing of NK cells revealed that the expression levels of 114 genes were upregulated in the oe-lnc-SNHG10 exo group, including inhibin subunit beta C (INHBC), which was involved in the TGF-β signaling pathway. Si-INHBC treatment abrogated the effect of oe-lnc-SNHG10 exo on NK cells. oe-lnc-SNHG10 exo induced tumor growth and upregulated INHBC expression in mice and downregulated the expression of perforin, granzyme B, and NK1.1 in tumor tissues.

CONCLUSIONS

The CRC cell-derived exosomal lncRNA SNHG10 suppresses the function of NK cells by upregulating INHBC expression. This study provides evidence that exosomal lncRNAs contribute to immune escape by inducing NK cell inhibition and proposes a potential treatment strategy for CRC.

Adoptive NK Cell Therapy: A Promising Treatment Prospect for Metastatic Melanoma

Simple Summary

The incidence of metastatic melanoma has been increasing over the past years with current therapies showing limited efficacy to cure the disease. Therefore, other options are being investigated, such as adoptive cell therapy (ACT) where activated immune cells are infused into a patient to attack melanoma. Natural killer (NK) cells are part of the innate immune system and extremely suitable for this kind of therapy since they show minimal toxicities in the clinical setting. In this review, we focus on current strategies for NK cell therapy and the development of new approaches that hold great promise for the treatment of advanced melanoma.

Abstract

Adoptive cell therapy (ACT) represents a promising alternative approach for patients with treatment-resistant metastatic melanoma. Lately, tumor infiltrating lymphocyte (TIL) therapy and chimeric antigen receptor (CAR)-T cell therapy have shown improved clinical outcome, compared to conventional chemotherapy or immunotherapy. Nevertheless, they are limited by immune escape of the tumor, cytokine release syndrome, and manufacturing challenges of autologous therapies. Conversely, the clinical use of Natural Killer (NK) cells has demonstrated a favorable clinical safety profile with minimal toxicities, providing an encouraging treatment alternative. Unlike T cells, NK cells are activated, amongst other mechanisms, by the downregulation of HLA class I molecules, thereby overcoming the hurdle of tumor immune escape. However, impairment of NK cell function has been observed in melanoma patients, resulting in deteriorated natural defense. To overcome this limitation, “activated” autologous or allogeneic NK cells have been infused into melanoma patients in early clinical trials, showing encouraging clinical benefit. Furthermore, as several NK cell-based therapeutics are being developed for different cancers, an emerging variety of approaches to increase migration and infiltration of adoptively transferred NK cells towards solid tumors is under preclinical investigation. These developments point to adoptive NK cell therapy as a highly promising treatment for metastatic melanoma in the future.

Angiogenic Properties of NK Cells in Cancer and Other Angiogenesis-Dependent Diseases

The pathogenesis of many serious diseases, including cancer, is closely related to disturbances in the angiogenesis process. Angiogenesis is essential for the progression of tumor growth and metastasis. The tumor microenvironment (TME) has immunosuppressive properties, which contribute to tumor expansion and angiogenesis. Similarly, the uterine microenvironment (UME) exerts a tolerogenic (immunosuppressive) and proangiogenic effect on its cells, promoting implantation and development of the embryo and placenta. In the TME and UME natural killer (NK) cells, which otherwise are capable of killing target cells autonomously, enter a state of reduced cytotoxicity or anergy. Both TME and UME are rich with factors (e.g., TGF-β, glycodelin, hypoxia), which support a conversion of NK cells to the low/non-cytotoxic, proangiogenic CD56^brightCD16^low phenotype. It is plausible that the phenomenon of acquiring proangiogenic and low cytotoxic features by NK cells is not only limited to cancer but is a common feature of different angiogenesis-dependent diseases (ADDs). In this review, we will discuss the role of NK cells in angiogenesis disturbances associated with cancer and other selected ADDs. Expanding the knowledge of the mechanisms responsible for angiogenesis and its disorders contributes to a better understanding of ADDs and may have therapeutic implications.

The Engaged Role of Tumor Microenvironment in Cancer Metabolism: Focusing on Cancer-Associated Fibroblast and Exosome Mediators

Metabolic reprogramming is a significant property of various cancer cells, which most commonly arises from the Tumor Microenvironment (TME). The events of metabolic pathways include the Warburg effect, shifting in Krebs cycle metabolites, and the rate of oxidative phosphorylation, potentially providing energy and structural requirements for the development and invasiveness of cancer cells. TME and tumor metabolism shifting have a close relationship through bidirectional signaling pathways between stromal and tumor cells. Cancer- Associated Fibroblasts (CAFs), as the most dominant cells of TME, play a crucial role in the aberrant metabolism of cancer. Furthermore, the stated relationship can affect survival, progression, and metastasis in cancer development. Recently, exosomes are considered one of the most prominent factors in cellular communications considering effective content and bidirectional mediatory effect between tumor and stromal cells. In this regard, CAF-Derived Exosomes (CDE) exhibit an efficient obligation to induce metabolic reprogramming for promoting growth and metastasis of cancer cells. The understanding of cancer metabolism, including factors related to TME, could lead to the discovery of a potential biomarker for diagnostic and therapeutic approaches in cancer management. This review focuses on the association between metabolic reprogramming and engaged microenvironmental, factors such as CAFs, and the associated derived exosomes.

CAR-NK Cell: A New Paradigm in Tumor Immunotherapy

The tumor microenvironment (TME) is greatly multifaceted and immune escape is an imperative attribute of tumors fostering tumor progression and metastasis. Based on reports, the restricted achievement attained by T cell immunotherapy reflects the prominence of emerging other innovative immunotherapeutics, in particular, natural killer (NK) cells-based treatments. Human NK cells act as the foremost innate immune effector cells against tumors and are vastly heterogeneous in the TME. Currently, there exists a rapidly evolving interest in the progress of chimeric antigen receptor (CAR)-engineered NK cells for tumor immunotherapy. CAR-NK cells superiorities over CAR-T cells in terms of better safety (e.g., absence or minimal cytokine release syndrome (CRS) and graft-versus-host disease (GVHD), engaging various mechanisms for stimulating cytotoxic function, and high feasibility for 'off-the-shelf' manufacturing. These effector cells could be modified to target various antigens, improve proliferation and persistence in vivo, upturn infiltration into tumors, and defeat resistant TME, which in turn, result in a desired anti-tumor response. More importantly, CAR-NK cells represent antigen receptors against tumor-associated antigens (TAAs), thereby redirecting the effector NK cells and supporting tumor-related immunosurveillance. In the current review, we focus on recent progress in the therapeutic competence of CAR-NK cells in solid tumors and offer a concise summary of the present hurdles affecting therapeutic outcomes of CAR-NK cell-based tumor immunotherapies.

Expanded human NK cells armed with CAR uncouple potent anti-tumor activity from off-tumor toxicity against solid tumors

Despite the remarkable success of chimeric antigen receptor (CAR)-T cells against hematologic malignancies, severe off-tumor effects have constrained their use against solid tumors. Recently, CAR-engineered natural killer (NK) cells have emerged as an effective and safe alternative. Here, we demonstrate that HER2 CAR-expression in NK cells from healthy donors and patients with breast cancer potently enhances their anti-tumor functions against various HER2-expressing cancer cells, regardless of MHC class I expression. Moreover, HER2 CAR-NK cells exert higher cytotoxicity than donor-matched HER2 CAR-T cells against tumor targets. Importantly, unlike CAR-T cells, HER2 CAR-NK cells do not elicit enhanced cytotoxicity or inflammatory cytokine production against non-malignant human lung epithelial cells with basal HER2 expression. Further, HER2 CAR-NK cells maintain high cytotoxic function in the presence of immunosuppressive factors enriched in solid tumors. These results show that CAR-NK cells may be a highly potent and safe source of immunotherapy in the context of solid tumors.

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Primary HER2 CAR-NK cells from patients with cancer have potent anti-tumor functions

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HER2 CAR-NK cells have a higher tumor killing capacity than HER2 CAR-T cells

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HER2 CAR-NK cells are not overly activated against HER2+ lung epithelial cells

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CAR-NK cells can overcome inhibition by the immunosuppressive factors TGF-β and PGE2

Pediatric Tumors-Mediated Inhibitory Effect on NK Cells: The Case of Neuroblastoma and Wilms' Tumors

Simple Summary

Neuroblastoma (NB) and Wilms’ tumor (WT) are the most common childhood solid extracranial tumors. The current treatments consist of a combination of surgery and chemotherapy or radiotherapy in high-risk patients. Such treatments are responsible for significant adverse events requiring long-term monitoring. Thus, a main challenge in NB and WT treatment is the development of novel therapeutic strategies to eliminate or minimize the adverse effects. The characterization of the immune environment could allow for the identification of new therapeutic targets. Herein, we described the interaction between these tumors and innate immune cells, in particular natural killer cells and monocytes. The detection of the immunosuppressive activity of specific NB and WT tumor cells on natural killer cells and on monocytes could offer novel cellular and molecular targets for an effective immunotherapy of NB and WT.

Abstract

Natural killer (NK) cells play a key role in the control of cancer development, progression and metastatic dissemination. However, tumor cells develop an array of strategies capable of impairing the activation and function of the immune system, including NK cells. In this context, a major event is represented by the establishment of an immunosuppressive tumor microenvironment (TME) composed of stromal cells, myeloid-derived suppressor cells, tumor-associated macrophages, regulatory T cells and cancer cells themselves. The different immunoregulatory cells infiltrating the TME, through the release of several immunosuppressive molecules or by cell-to-cell interactions, cause an impairment of the recruitment of NK cells and other lymphocytes with effector functions. The different mechanisms by which stromal and tumor cells impair NK cell function have been particularly explored in adult solid tumors and, in less depth, investigated and discussed in a pediatric setting. In this review, we will compare pediatric and adult solid malignancies concerning the respective mechanisms of NK cell inhibition, highlighting novel key data in neuroblastoma and Wilms’ tumor, two of the most frequent pediatric extracranial solid tumors. Indeed, both tumors are characterized by the presence of stromal cells acting through the release of immunosuppressive molecules. In addition, specific tumor cell subsets inhibit NK cell cytotoxic function by cell-to-cell contact mechanisms likely controlled by the transcriptional coactivator TAZ. These findings could lead to a more performant diagnostic approach and to the development of novel immunotherapeutic strategies targeting the identified cellular and molecular targets.

Natural Killer Cell Interactions With Myeloid Derived Suppressor Cells in the Tumor Microenvironment and Implications for Cancer Immunotherapy

The tumor microenvironment (TME) is a complex and heterogeneous environment composed of cancer cells, tumor stroma, a mixture of tissue-resident and infiltrating immune cells, secreted factors, and extracellular matrix proteins. Natural killer (NK) cells play a vital role in fighting tumors, but chronic stimulation and immunosuppression in the TME lead to NK cell exhaustion and limited antitumor functions. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid cells with potent immunosuppressive activity that gradually accumulate in tumor tissues. MDSCs interact with innate and adaptive immune cells and play a crucial role in negatively regulating the immune response to tumors. This review discusses MDSC-mediated NK cell regulation within the TME, focusing on critical cellular and molecular interactions. We review current strategies that target MDSC-mediated immunosuppression to enhance NK cell cytotoxic antitumor activity. We also speculate on how NK cell-based antitumor immunotherapy could be improved.

Natural Killer Cells: The Linchpin for Successful Cancer Immunotherapy

Cancer immunotherapy is a highly successful and rapidly evolving treatment modality that works by augmenting the body’s own immune system. While various immune stimulation strategies such as PD-1/PD-L1 or CTLA-4 checkpoint blockade result in robust responses, even in patients with advanced cancers, the overall response rate is low. While immune checkpoint inhibitors are known to enhance cytotoxic T cells’ antitumor response, current evidence suggests that immune responses independent of cytotoxic T cells, such as Natural Killer (NK) cells, play crucial role in the efficacy of immunotherapeutic interventions. NK cells hold a distinct role in potentiating the innate immune response and activating the adaptive immune system. This review highlights the importance of the early actions of the NK cell response and the pivotal role NK cells hold in priming the immune system and setting the stage for successful response to cancer immunotherapy. Yet, in many patients the NK cell compartment is compromised thus lowering the chances of successful outcomes of many immunotherapies. An overview of mechanisms that can drive NK cell dysfunction and hinder immunotherapy success is provided. Rather than relying on the likely dysfunctional endogenous NK cells to work with immunotherapies, adoptive allogeneic NK cell therapies provide a viable solution to increase response to immunotherapies. This review highlights the advances made in development of NK cell therapeutics for clinical application with evidence supporting their combinatorial application with other immune-oncology approaches to improve outcomes of immunotherapies.

pH-Triggered Copper-Free Click Reaction-Mediated Micelle Aggregation for Enhanced Tumor Retention and Elevated Immuno-Chemotherapy against Melanoma

Natural killer (NK) cell-based immunotherapy presents a promising antitumor strategy and holds potential for combination with chemotherapy. However, the suppressed NK cell activity and poor tumor retention of therapeutics hinder the efficacy. To activate NK cell-based immuno-chemotherapy and enhance the tumor retention, we proposed a pH-responsive self-aggregated nanoparticle for the codelivery of chemotherapeutic doxorubicin (DOX) and the transforming growth factor-β (TGF-β)/Smad3 signaling pathway inhibitor SIS3. Polycaprolactone-poly(ethylene glycol) (PCL-PEG₂₀₀₀) micelles modified with dibenzylcyclooctyne (DBCO) or azido (N₃) and coated with acid-cleavable PEG₅₀₀₀ were established. This nanoplatform, namely, M-DN@DOX/SIS3, could remain well dispersed in the neutral systemic circulation, while quickly respond to the acidic tumor microenvironment and intracellular lysosomes, triggering copper-free click reaction-mediated aggregation, leading to the increased tumor accumulation and reduced cellular efflux. In addition, the combination of DOX with SIS3 facilitated by the aggregation strategy resulted in potent inhibition of melanoma tumor growth and significantly increased NK cells, NK cell cytokines, and antitumor T cells in the tumor. Taken together, our study offered a new concept of applying copper-free click chemistry to achieve nanoparticle aggregation and enhance tumor retention, as well as a promising new combined tumor treatment approach of chemotherapy and immunotherapy.

Therapeutic Approaches Targeting the Natural Killer-Myeloid Cell Axis in the Tumor Microenvironment

Immunotherapy has transformed cancer treatment by promoting durable clinical responses in a proportion of patients; however, treatment still fails in many patients. Innate immune cells play a key role in the response to immunotherapy. Crosstalk between innate and adaptive immune systems drives T-cell activation but also limits immunotherapy response, as myeloid cells are commonly associated with resistance. Hence, innate cells have both negative and positive effects within the tumor microenvironment (TME), and despite investment in early clinical trials targeting innate cells, they have seen limited success. Suppressive myeloid cells facilitate metastasis and immunotherapy resistance through TME remodeling and inhibition of adaptive immune cells. Natural killer (NK) cells, in contrast, secrete inflammatory cytokines and directly kill transformed cells, playing a key immunosurveillance role in early tumor development. Myeloid and NK cells show reciprocal crosstalk, influencing myeloid cell functional status or antigen presentation and NK effector function, respectively. Crosstalk between myeloid cells and the NK immune network in the TME is especially important in the context of therapeutic intervention. Here we discuss how myeloid and NK cell interactions shape anti-tumor responses by influencing an immunosuppressive TME and how this may influence outcomes of treatment strategies involving drugs that target myeloid and NK cells.