Showing papers on "Cytotoxic T cell published in 2019"

CD8+ T cells regulate tumour ferroptosis during cancer immunotherapy

Abstract: Cancer immunotherapy restores or enhances the effector function of CD8+ T cells in the tumour microenvironment1,2. CD8+ T cells activated by cancer immunotherapy clear tumours mainly by inducing cell death through perforin-granzyme and Fas-Fas ligand pathways3,4. Ferroptosis is a form of cell death that differs from apoptosis and results from iron-dependent accumulation of lipid peroxide5,6. Although it has been investigated in vitro7,8, there is emerging evidence that ferroptosis might be implicated in a variety of pathological scenarios9,10. It is unclear whether, and how, ferroptosis is involved in T cell immunity and cancer immunotherapy. Here we show that immunotherapy-activated CD8+ T cells enhance ferroptosis-specific lipid peroxidation in tumour cells, and that increased ferroptosis contributes to the anti-tumour efficacy of immunotherapy. Mechanistically, interferon gamma (IFNγ) released from CD8+ T cells downregulates the expression of SLC3A2 and SLC7A11, two subunits of the glutamate-cystine antiporter system xc-, impairs the uptake of cystine by tumour cells, and as a consequence, promotes tumour cell lipid peroxidation and ferroptosis. In mouse models, depletion of cystine or cysteine by cyst(e)inase (an engineered enzyme that degrades both cystine and cysteine) in combination with checkpoint blockade synergistically enhanced T cell-mediated anti-tumour immunity and induced ferroptosis in tumour cells. Expression of system xc- was negatively associated, in cancer patients, with CD8+ T cell signature, IFNγ expression, and patient outcome. Analyses of human transcriptomes before and during nivolumab therapy revealed that clinical benefits correlate with reduced expression of SLC3A2 and increased IFNγ and CD8. Thus, T cell-promoted tumour ferroptosis is an anti-tumour mechanism, and targeting this pathway in combination with checkpoint blockade is a potential therapeutic approach.

Subsets of exhausted CD8+ T cells differentially mediate tumor control and respond to checkpoint blockade.

Abstract: T cell dysfunction is a hallmark of many cancers, but the basis for T cell dysfunction and the mechanisms by which antibody blockade of the inhibitory receptor PD-1 (anti-PD-1) reinvigorates T cells are not fully understood. Here we show that such therapy acts on a specific subpopulation of exhausted CD8+ tumor-infiltrating lymphocytes (TILs). Dysfunctional CD8+ TILs possess canonical epigenetic and transcriptional features of exhaustion that mirror those seen in chronic viral infection. Exhausted CD8+ TILs include a subpopulation of 'progenitor exhausted' cells that retain polyfunctionality, persist long term and differentiate into 'terminally exhausted' TILs. Consequently, progenitor exhausted CD8+ TILs are better able to control tumor growth than are terminally exhausted T cells. Progenitor exhausted TILs can respond to anti-PD-1 therapy, but terminally exhausted TILs cannot. Patients with melanoma who have a higher percentage of progenitor exhausted cells experience a longer duration of response to checkpoint-blockade therapy. Thus, approaches to expand the population of progenitor exhausted CD8+ T cells might be an important component of improving the response to checkpoint blockade.

CD8 T Cell Exhaustion During Chronic Viral Infection and Cancer

Abstract: Exhausted CD8 T (Tex) cells are a distinct cell lineage that arise during chronic infections and cancers in animal models and humans. Tex cells are characterized by progressive loss of effector fun...

CD8+ cytotoxic T lymphocytes in cancer immunotherapy: A review.

Abstract: CD8+ cytotoxic T lymphocytes (CTLs) are preferred immune cells for targeting cancer. During cancer progression, CTLs encounter dysfunction and exhaustion due to immunerelated tolerance and immunosuppression within the tumor microenvironment (TME), with all favor adaptive immune-resistance. Cancer-associated fibroblasts (CAFs), macrophage type 2 (M2) cells, and regulatory T cells (Tregs) could make immunologic barriers against CD8 + T cell-mediated antitumor immune responses. Thus, CD8 + T cells are needed to be primed and activated toward effector CTLs in a process called tumor immunity cycle for making durable and efficient antitumor immune responses. The CD8 + T cell priming is directed essentially as a corroboration work between cells of innate immunity including dendritic cells (DCs) and natural killer (NK) cells with CD4 + T cells in adoptive immunity. Upon activation, effector CTLs infiltrate to the core or invading site of the tumor (so-called infiltrated-inflamed [I-I] TME) and take essential roles for killing cancer cells. Exogenous reactivation and/or priming of CD8 + T cells can be possible using rational immunotherapy strategies. The increase of the ratio for costimulatory to coinhibitory mediators using immune checkpoint blockade (ICB) approach. Programmed death-1 receptor (PD-1)-ligand (PD-L1) and CTL-associated antigen 4 (CTLA-4) are checkpoint receptors that can be targeted for relieving exhaustion of CD8 + T cells and renewing their priming, respectively, and thereby eliminating antigen-expressing cancer cells. Due to a diverse relation between CTLs with Tregs, the Treg activity could be dampened for increasing the number and rescuing the functional potential of CTLs to induce immunosensitivity of cancer cells.

TOX transcriptionally and epigenetically programs CD8 + T cell exhaustion

Abstract: Exhausted CD8+ T (Tex) cells in chronic infections and cancer have limited effector function, high co-expression of inhibitory receptors and extensive transcriptional changes compared with effector (Teff) or memory (Tmem) CD8+ T cells. Tex cells are important clinical targets of checkpoint blockade and other immunotherapies. Epigenetically, Tex cells are a distinct immune subset, with a unique chromatin landscape compared with Teff and Tmem cells. However, the mechanisms that govern the transcriptional and epigenetic development of Tex cells remain unknown. Here we identify the HMG-box transcription factor TOX as a central regulator of Tex cells in mice. TOX is largely dispensable for the formation of Teff and Tmem cells, but it is critical for exhaustion: in the absence of TOX, Tex cells do not form. TOX is induced by calcineurin and NFAT2, and operates in a feed-forward loop in which it becomes calcineurin-independent and sustained in Tex cells. Robust expression of TOX therefore results in commitment to Tex cells by translating persistent stimulation into a distinct Tex cell transcriptional and epigenetic developmental program.

A defined commensal consortium elicits CD8 T cells and anti-cancer immunity

Abstract: There is a growing appreciation for the importance of the gut microbiota as a therapeutic target in various diseases. However, there are only a handful of known commensal strains that can potentially be used to manipulate host physiological functions. Here we isolate a consortium of 11 bacterial strains from healthy human donor faeces that is capable of robustly inducing interferon-γ-producing CD8 T cells in the intestine. These 11 strains act together to mediate the induction without causing inflammation in a manner that is dependent on CD103+ dendritic cells and major histocompatibility (MHC) class Ia molecules. Colonization of mice with the 11-strain mixture enhances both host resistance against Listeria monocytogenes infection and the therapeutic efficacy of immune checkpoint inhibitors in syngeneic tumour models. The 11 strains primarily represent rare, low-abundance components of the human microbiome, and thus have great potential as broadly effective biotherapeutics. A consortium of 11 bacterial strains from the healthy human gut microbiota can strongly induce interferon-γ-producing CD8 T cells in the intestine, and enhance both resistance to bacterial infection and the therapeutic efficacy of immune checkpoint inhibitors.

TOX is a critical regulator of tumour-specific T cell differentiation

Abstract: Tumour-specific CD8 T cell dysfunction is a differentiation state that is distinct from the functional effector or memory T cell states1–6. Here we identify the nuclear factor TOX as a crucial regulator of the differentiation of tumour-specific T (TST) cells. We show that TOX is highly expressed in dysfunctional TST cells from tumours and in exhausted T cells during chronic viral infection. Expression of TOX is driven by chronic T cell receptor stimulation and NFAT activation. Ectopic expression of TOX in effector T cells in vitro induced a transcriptional program associated with T cell exhaustion. Conversely, deletion of Tox in TST cells in tumours abrogated the exhaustion program: Tox-deleted TST cells did not upregulate genes for inhibitory receptors (such as Pdcd1, Entpd1, Havcr2, Cd244 and Tigit), the chromatin of which remained largely inaccessible, and retained high expression of transcription factors such as TCF-1. Despite their normal, ‘non-exhausted’ immunophenotype, Tox-deleted TST cells remained dysfunctional, which suggests that the regulation of expression of inhibitory receptors is uncoupled from the loss of effector function. Notably, although Tox-deleted CD8 T cells differentiated normally to effector and memory states in response to acute infection, Tox-deleted TST cells failed to persist in tumours. We hypothesize that the TOX-induced exhaustion program serves to prevent the overstimulation of T cells and activation-induced cell death in settings of chronic antigen stimulation such as cancer.

TOX reinforces the phenotype and longevity of exhausted T cells in chronic viral infection.

Abstract: Cytotoxic T cells are essential mediators of protective immunity to viral infection and malignant tumours and are a key target of immunotherapy approaches. However, prolonged exposure to cognate antigens often attenuates the effector capacity of T cells and limits their therapeutic potential1-4. This process, known as T cell exhaustion or dysfunction1, is manifested by epigenetically enforced changes in gene regulation that reduce the expression of cytokines and effector molecules and upregulate the expression of inhibitory receptors such as programmed cell-death 1 (PD-1)5-8. The underlying molecular mechanisms that induce and stabilize the phenotypic and functional features of exhausted T cells remain poorly understood9-12. Here we report that the development and maintenance of populations of exhausted T cells in mice requires the thymocyte selection-associated high mobility group box (TOX) protein13-15. TOX is induced by high antigen stimulation of the T cell receptor and correlates with the presence of an exhausted phenotype during chronic infections with lymphocytic choriomeningitis virus in mice and hepatitis C virus in humans. Removal of its DNA-binding domain reduces the expression of PD-1 at the mRNA and protein level, augments the production of cytokines and results in a more polyfunctional T cell phenotype. T cells with this deletion initially mediate increased effector function and cause more severe immunopathology, but ultimately undergo a massive decline in their quantity, notably among the subset of TCF-1+ self-renewing T cells. Altogether, we show that TOX is a critical factor for the normal progression of T cell dysfunction and the maintenance of exhausted T cells during chronic infection, and provide a link between the suppression of effector function intrinsic to CD8 T cells and protection against immunopathology.

Targeting DNA Damage Response Promotes Antitumor Immunity through STING-Mediated T-cell Activation in Small Cell Lung Cancer

Abstract: Despite recent advances in the use of immunotherapy, only a minority of small cell lung cancer (SCLC) patients respond to immune checkpoint blockade (ICB). Here, we show that targeting DNA damage response (DDR) proteins, poly ADP-ribose polymerase (PARP) and checkpoint kinase 1 (CHK1) significantly increased protein and surface expression of PD-L1. PARP or CHK1 inhibition remarkably potentiated the anti-tumor effect of PD-L1 blockade and augmented cytotoxic T-cell infiltration in multiple immunocompetent SCLC in vivo models. CD8 depletion reversed the anti-tumor effect demonstrating the role of CD8+ T-cells in combined DDR-PD-L1 blockade in SCLC. We further demonstrate that DDR inhibition activated the STING/TBK1/IRF3 innate immune pathway, leading to increased levels of chemokines such as CXCL10 and CCL5 that induced activation and function of cytotoxic T-lymphocytes. Knockdown of cGAS and STING successfully reversed the anti-tumor effect of combined inhibition DDR and PD-L1. Our results define previously unrecognized innate immune pathway-mediated immunomodulatory functions of DDR proteins and provide a rationale for combining PARP/CHK1 inhibitors and immunotherapies in SCLC.

Regulatory T (Treg) cells in cancer: Can Treg cells be a new therapeutic target?

Abstract: Regulatory T (Treg) cells suppress abnormal/excessive immune responses to self- and nonself-antigens to maintain immune homeostasis. In tumor immunity, Treg cells are involved in tumor development and progression by inhibiting antitumor immunity. There are several Treg cell immune suppressive mechanisms: inhibition of costimulatory signals by CD80 and CD86 expressed by dendritic cells through cytotoxic T-lymphocyte antigen-4, interleukin (IL)-2 consumption by high-affinity IL-2 receptors with high CD25 (IL-2 receptor α-chain) expression, secretion of inhibitory cytokines, metabolic modulation of tryptophan and adenosine, and direct killing of effector T cells. Infiltration of Treg cells into the tumor microenvironment (TME) occurs in multiple murine and human tumors. Regulatory T cells are chemoattracted to the TME by chemokine gradients such as CCR4-CCL17/22, CCR8-CCL1, CCR10-CCL28, and CXCR3-CCL9/10/11. Regulatory T cells are then activated and inhibit antitumor immune responses. A high infiltration by Treg cells is associated with poor survival in various types of cancer. Therefore, strategies to deplete Treg cells and control of Treg cell functions to increase antitumor immune responses are urgently required in the cancer immunotherapy field. Various molecules that are highly expressed by Treg cells, such as immune checkpoint molecules, chemokine receptors, and metabolites, have been targeted by Abs or small molecules, but additional strategies are needed to fine-tune and optimize for augmenting antitumor effects restricted in the TME while avoiding systemic autoimmunity. Here, we provide a brief synopsis of these cells in cancer and how they can be controlled to achieve therapeutic outcomes.

B cell maturation antigen–specific CAR T cells are clinically active in multiple myeloma

Abstract: BACKGROUND. CAR T cells are a promising therapy for hematologic malignancies. B cell maturation antigen (BCMA) is a rational target in multiple myeloma (MM). METHODS. We conducted a phase I study of autologous T cells lentivirally transduced with a fully human, BCMA-specific CAR containing CD3ζ and 4-1BB signaling domains (CART-BCMA), in subjects with relapsed/refractory MM. Twenty-five subjects were treated in 3 cohorts as follows: cohort 1, 1 × 108 to 5 × 108 CART-BCMA cells alone; cohort 2, cyclophosphamide (Cy) 1.5 g/m2 plus 1 × 107 to 5 × 107 CART-BCMA cells; cohort 3, Cy 1.5 g/m2 plus 1 × 108 to 5 × 108 CART-BCMA cells. No prespecified BCMA expression level was required. RESULTS. CART-BCMA cells were manufactured and expanded in all subjects. Toxicities included cytokine release syndrome and neurotoxicity, which were grade 3–4 in 8 (32%) and 3 (12%) subjects, respectively, and reversible. One subject died at day 24 from candidemia and progressive myeloma, following treatment for severe cytokine release syndrome and encephalopathy. Responses (based on treated subjects) were seen in 4 of 9 (44%) in cohort 1, 1 of 5 (20%) in cohort 2, and 7 of 11 (64%) in cohort 3, including 5 partial, 5 very good partial, and 2 complete responses, 3 of which were ongoing at 11, 14, and 32 months. Decreased BCMA expression on residual MM cells was noted in responders; expression increased at progression in most. Responses and CART-BCMA expansion were associated with CD4/CD8 T cell ratio and frequency of CD45RO–CD27+CD8+ T cells in the premanufacturing leukapheresis product. CONCLUSION. CART-BCMA infusions with or without lymphodepleting chemotherapy are clinically active in heavily pretreated patients with MM. TRIAL REGISTRATION. {"type":"clinical-trial","attrs":{"text":"NCT02546167","term_id":"NCT02546167"}}NCT02546167. FUNDING. University of Pennsylvania-Novartis Alliance and NIH.

TOX and TOX2 transcription factors cooperate with NR4A transcription factors to impose CD8+ T cell exhaustion

Abstract: T cells expressing chimeric antigen receptors (CAR T cells) have shown impressive therapeutic efficacy against leukemias and lymphomas. However, they have not been as effective against solid tumors because they become hyporesponsive (“exhausted” or “dysfunctional”) within the tumor microenvironment, with decreased cytokine production and increased expression of several inhibitory surface receptors. Here we define a transcriptional network that mediates CD8+ T cell exhaustion. We show that the high-mobility group (HMG)-box transcription factors TOX and TOX2, as well as members of the NR4A family of nuclear receptors, are targets of the calcium/calcineurin-regulated transcription factor NFAT, even in the absence of its partner AP-1 (FOS-JUN). Using a previously established CAR T cell model, we show that TOX and TOX2 are highly induced in CD8+ CAR+ PD-1high TIM3high (“exhausted”) tumor-infiltrating lymphocytes (CAR TILs), and CAR TILs deficient in both TOX and TOX2 (Tox DKO) are more effective than wild-type (WT), TOX-deficient, or TOX2-deficient CAR TILs in suppressing tumor growth and prolonging survival of tumor-bearing mice. Like NR4A-deficient CAR TILs, Tox DKO CAR TILs show increased cytokine expression, decreased expression of inhibitory receptors, and increased accessibility of regions enriched for motifs that bind activation-associated nuclear factor κB (NFκB) and basic region-leucine zipper (bZIP) transcription factors. These data indicate that Tox and Nr4a transcription factors are critical for the transcriptional program of CD8+ T cell exhaustion downstream of NFAT. We provide evidence for positive regulation of NR4A by TOX and of TOX by NR4A, and suggest that disruption of TOX and NR4A expression or activity could be promising strategies for cancer immunotherapy.

An intra-tumoral niche maintains and differentiates stem-like CD8 T cells

Abstract: Tumour-infiltrating lymphocytes are associated with a survival benefit in several tumour types and with the response to immunotherapy1–8. However, the reason some tumours have high CD8 T cell infiltration while others do not remains unclear. Here we investigate the requirements for maintaining a CD8 T cell response against human cancer. We find that CD8 T cells within tumours consist of distinct populations of terminally differentiated and stem-like cells. On proliferation, stem-like CD8 T cells give rise to more terminally differentiated, effector-molecule-expressing daughter cells. For many T cells to infiltrate the tumour, it is critical that this effector differentiation process occur. In addition, we show that these stem-like T cells reside in dense antigen-presenting-cell niches within the tumour, and that tumours that fail to form these structures are not extensively infiltrated by T cells. Patients with progressive disease lack these immune niches, suggesting that niche breakdown may be a key mechanism of immune escape. The authors examine the immune cell infiltrates of human tumours and provide evidence for a population of CD8 T cells with stem-cell characteristics and proliferative capacity that reside in an antigen-presenting niche within tumours.

Syringic acid triggers reactive oxygen species-mediated cytotoxicity in HepG2 cells.

Abstract: Hepatocellular carcinoma is the second most common cause of cancer death in the world and its incidence has dramatically increased worldwide in the past two decades. Syringic acid (SA) has been studied for its hepatoprotective, anti-inflammatory, immunomodulatory, free radical scavenging, and antioxidant activities. We aimed to evaluate the cytotoxic effect of SA against human hepatoma HepG2 cell line. Cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. HepG2 cells were treated with SA at concentration ranges of 25, 50, and 100 µM for 24 h. Reactive oxygen species (ROS) expression was investigated by dichlorofluorescein staining assay. Morphological changes of SA-treated HepG2 cells were evaluated by acridine orange (AO) and ethidium bromide (EB) dual staining. Apoptotic marker gene expressions were evaluated by qPCR. SA treatment caused significant cytotoxicity and liberation of ROS in HepG2 cells. AO and EB staining showed membrane blebbing and distortion in SA-treated cells. Apoptotic markers such as caspases 3 and 9, cytochrome c, Apaf-1, Bax, and p53 gene expressions were significantly increased upon SA treatment indicating the possibility of apoptosis induction in HepG2 cells. This treatment also caused significant downregulation of Bcl-2 gene expression. SA has a cytotoxic effect on human HepG2 cell line, and this might be a promising agent in anticancer research.

HIV-1 remission following CCR5Δ32/Δ32 haematopoietic stem-cell transplantation

Abstract: A cure for HIV-1 remains unattainable as only one case has been reported, a decade ago1,2. The individual—who is known as the ‘Berlin patient’—underwent two allogeneic haematopoietic stem-cell transplantation (HSCT) procedures using a donor with a homozygous mutation in the HIV coreceptor CCR5 (CCR5Δ32/Δ32) to treat his acute myeloid leukaemia. Total body irradiation was given with each HSCT. Notably, it is unclear which treatment or patient parameters contributed to this case of long-term HIV remission. Here we show that HIV-1 remission may be possible with a less aggressive and toxic approach. An adult infected with HIV-1 underwent allogeneic HSCT for Hodgkin’s lymphoma using cells from a CCR5Δ32/Δ32 donor. He experienced mild gut graft-versus-host disease. Antiretroviral therapy was interrupted 16 months after transplantation. HIV-1 remission has been maintained over a further 18 months. Plasma HIV-1 RNA has been undetectable at less than one copy per millilitre along with undetectable HIV-1 DNA in peripheral CD4 T lymphocytes. Quantitative viral outgrowth assays from peripheral CD4 T lymphocytes show no reactivatable virus using a total of 24 million resting CD4 T cells. CCR5-tropic, but not CXCR4-tropic, viruses were identified in HIV-1 DNA from CD4 T cells of the patient before the transplant. CD4 T cells isolated from peripheral blood after transplantation did not express CCR5 and were susceptible only to CXCR4-tropic virus ex vivo. HIV-1 Gag-specific CD4 and CD8 T cell responses were lost after transplantation, whereas cytomegalovirus-specific responses were detectable. Similarly, HIV-1-specific antibodies and avidities fell to levels comparable to those in the Berlin patient following transplantation. Although at 18 months after the interruption of treatment it is premature to conclude that this patient has been cured, these data suggest that a single allogeneic HSCT with homozygous CCR5Δ32 donor cells may be sufficient to achieve HIV-1 remission with reduced intensity conditioning and no irradiation, and the findings provide further support for the development of HIV-1 remission strategies based on preventing CCR5 expression. An adult infected with HIV-1 who underwent allogeneic haematopoietic stem-cell transplantation for Hodgkin’s lymphoma using cells from a CCR5Δ32/Δ32 donor achieved full remission of HIV-1 for 18 months after transplantation and 16 months after cessation of antiretroviral therapy.

PARP Inhibitor Efficacy Depends on CD8+ T-cell Recruitment via Intratumoral STING Pathway Activation in BRCA-Deficient Models of Triple-Negative Breast Cancer

Abstract: Combinatorial clinical trials of PARP inhibitors with immunotherapies are ongoing, yet the immunomodulatory effects of PARP inhibition have been incompletely studied. Here, we sought to dissect the mechanisms underlying PARP inhibitor-induced changes in the tumor microenvironment of BRCA1-deficient triple-negative breast cancer (TNBC). We demonstrate that the PARP inhibitor olaparib induces CD8+ T cell infiltration and activation in vivo, and that CD8+ T cell depletion severely compromises anti-tumor efficacy. Olaparib-induced T cell recruitment is mediated through activation of the cGAS/STING pathway in tumor cells with paracrine activation of dendritic cells and is more pronounced in HR-deficient compared to HR-proficient TNBC cells and in vivo models. CRISPR-knockout of STING in cancer cells prevents proinflammatory signaling and is sufficient to abolish olaparib-induced T cell infiltration in vivo. These findings elucidate an additional mechanism of action of PARP inhibitors and provide rationale for combining PARP inhibition with immunotherapies for the treatment of TNBC.

Single-cell RNA-seq reveals TOX as a key regulator of CD8+ T cell persistence in chronic infection.

Abstract: Progenitor-like CD8+ T cells mediate long-term immunity to chronic infection and cancer and respond potently to immune checkpoint blockade. These cells share transcriptional regulators with memory precursor cells, including T cell-specific transcription factor 1 (TCF1), but it is unclear whether they adopt distinct programs to adapt to the immunosuppressive environment. By comparing the single-cell transcriptomes and epigenetic profiles of CD8+ T cells responding to acute and chronic viral infections, we found that progenitor-like CD8+ T cells became distinct from memory precursor cells before the peak of the T cell response. We discovered a coexpression gene module containing Tox that exhibited higher transcriptional activity associated with more abundant active histone marks in progenitor-like cells than memory precursor cells. Moreover, thymocyte selection-associated high mobility group box protein TOX (TOX) promoted the persistence of antiviral CD8+ T cells and was required for the programming of progenitor-like CD8+ T cells. Thus, long-term CD8+ T cell immunity to chronic viral infection requires unique transcriptional and epigenetic programs associated with the transcription factor TOX.

Macrophage polarity in cancer: A review.

Abstract: Macrophages are the most abundant cells within the tumor stroma displaying noticeable plasticity, which allows them to perform several functions within the tumor microenvironment. Tumor-associated macrophages commonly refer to an alternative M2 phenotype, exhibiting anti-inflammatory and pro-tumoral effects. M2 cells are highly versatile and multi-tasking cells that directly influence multiple steps in tumor development, including cancer cell survival, proliferation, stemness, and invasiveness along with angiogenesis and immunosuppression. M2 cells perform these functions through critical interactions with cells related to tumor progression, including Th2 cells, cancer-associated fibroblasts, cancer cells, regulatory T cells (Tregs), and myeloid-derived suppressor cells. M2 cells also have negative cross-talks with tumor suppressor cells, including cytotoxic T cells and natural killer cells. Programed death-1 (PD-1) is one of the key receptors expressed in M2 cells that, upon interaction with its ligand PD-L1, plays cardinal roles for induction of immune evasion in cancer cells. In addition, M2 cells can neutralize the effects of the pro-inflammatory and anti-tumor M1 phenotype. Classically activated M1 cells express high levels of major histocompatibility complex molecules, and the cells are strong killers of cancer cells. Therefore, orchestrating M2 reprogramming toward an M1 phenotype would offer a promising approach for reversing the fate of tumor and promoting cancer regression. Macrophage switching toward an anti-inflammatory M1 phenotype could be used as an adjuvant with other approaches, including radiotherapy and immune checkpoint blockades, such as anti-PD-L1/PD-1 strategies.

The clinical role of the TME in solid cancer.

Abstract: The highly complex and heterogenous ecosystem of a tumour not only contains malignant cells, but also interacting cells from the host such as endothelial cells, stromal fibroblasts, and a variety of immune cells that control tumour growth and invasion. It is well established that anti-tumour immunity is a critical hurdle that must be overcome for tumours to initiate, grow and spread and that anti-tumour immunity can be modulated using current immunotherapies to achieve meaningful anti-tumour clinical responses. Pioneering studies in melanoma, ovarian and colorectal cancer have demonstrated that certain features of the tumour immune microenvironment (TME)-in particular, the degree of tumour infiltration by cytotoxic T cells-can predict a patient's clinical outcome. More recently, studies in renal cell cancer have highlighted the importance of assessing the phenotype of the infiltrating T cells to predict early relapse. Furthermore, intricate interactions with non-immune cellular players such as endothelial cells and fibroblasts modulate the clinical impact of immune cells in the TME. Here, we review the critical components of the TME in solid tumours and how they shape the immune cell contexture, and we summarise numerous studies evaluating its clinical significance from a prognostic and theranostic perspective.

Fates of CD8+ T cells in Tumor Microenvironment.

Abstract: Studies have reported a positive correlation between elevated CD8+ T cells in the tumor microenvironment (TME) and good prognosis in cancer. However, the mechanisms linking T cell tumor-infiltration and tumor rejection are yet to be fully understood. The cells and factors of the TME facilitate tumor development in various ways. CD8+ T cell function is influenced by a number of factors, including CD8+ T cell trafficking and localization into tumor sites; as well as CD8+ T cell growth and differentiation. This review highlights recent literature as well as currently evolving concepts regarding the fates of CD8+ T cells in the TME from three different aspects CD8+ T cell trafficking, differentiation and function. A thorough understanding of factors contributing to the fates of CD8+ T cells will allow researchers to develop new strategies and improve on already existing strategies to facilitate CD8+ T cell mediated anti-tumor function, impede T cell dysfunction and modulate the TME into a less immunosuppressive TME.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition

Abstract: Senescent cells accumulate in human tissues during ageing and contribute to age-related pathologies. The mechanisms responsible for their accumulation are unclear. Here we show that senescent dermal fibroblasts express the non-classical MHC molecule HLA-E, which interacts with the inhibitory receptor NKG2A expressed by NK and highly differentiated CD8+ T cells to inhibit immune responses against senescent cells. HLA-E expression is induced by senescence-associated secretary phenotype-related pro-inflammatory cytokines, and is regulated by p38 MAP kinase signalling in vitro. Consistently, HLA-E expression is increased on senescent cells in human skin sections from old individuals, when compared with those from young, and in human melanocytic nevi relative to normal skin. Lastly, blocking the interaction between HLA-E and NKG2A boosts immune responses against senescent cells in vitro. We thus propose that increased HLA-E expression contributes to persistence of senescent cells in tissues, thereby suggesting a new strategy for eliminating senescent cells during ageing.

Lenvatinib plus anti-PD-1 antibody combination treatment activates CD8+ T cells through reduction of tumor-associated macrophage and activation of the interferon pathway.

Abstract: Lenvatinib is a multiple receptor tyrosine kinase inhibitor targeting mainly vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) receptors. We investigated the immunomodulatory activities of lenvatinib in the tumor microenvironment and its mechanisms of enhanced antitumor activity when combined with a programmed cell death-1 (PD-1) blockade. Antitumor activity was examined in immunodeficient and immunocompetent mouse tumor models. Single-cell analysis, flow cytometric analysis, and immunohistochemistry were used to analyze immune cell populations and their activation. Gene co-expression network analysis and pathway analysis using RNA sequencing data were used to identify lenvatinib-driven combined activity with anti-PD-1 antibody (anti-PD-1). Lenvatinib showed potent antitumor activity in the immunocompetent tumor microenvironment compared with the immunodeficient tumor microenvironment. Antitumor activity of lenvatinib plus anti-PD-1 was greater than that of either single treatment. Flow cytometric analysis revealed that lenvatinib reduced tumor-associated macrophages (TAMs) and increased the percentage of activated CD8+ T cells secreting interferon (IFN)-γ+ and granzyme B (GzmB). Combination treatment further increased the percentage of T cells, especially CD8+ T cells, among CD45+ cells and increased IFN-γ+ and GzmB+ CD8+ T cells. Transcriptome analyses of tumors resected from treated mice showed that genes specifically regulated by the combination were significantly enriched for type-I IFN signaling. Pretreatment with lenvatinib followed by anti-PD-1 treatment induced significant antitumor activity compared with anti-PD-1 treatment alone. Our findings show that lenvatinib modulates cancer immunity in the tumor microenvironment by reducing TAMs and, when combined with PD-1 blockade, shows enhanced antitumor activity via the IFN signaling pathway. These findings provide a scientific rationale for combination therapy of lenvatinib with PD-1 blockade to improve cancer immunotherapy.

PD-1/PD-L1 pathway: Basic biology and role in cancer immunotherapy

Abstract: Over the course of past few years, cancer immunotherapy has been accompanied with promising results. However, preliminary investigations with respect to immunotherapy concentrated mostly on targeting the immune checkpoints, nowadays, emerge as the most efficient strategy to raise beneficial antitumor immune responses. Programmed cell death protein 1 (PD-1) plays an important role in subsiding immune responses and promoting self-tolerance through suppressing the activity of T cells and promoting differentiation of regulatory T cells. PD-1 is considered as an immune checkpoint and protects against autoimmune responses through both induction of apoptosis in antigen-specific T cells and inhibiting apoptosis in regulatory T cells. Several clinical trials exerting PD-1 monoclonal antibodies as well as other immune-checkpoint blockades have had prosperous outcomes and opened new horizons in tumor immunotherapy. Nonetheless, a bulk of patients have failed to respond to these newly emerging immune-based approach and the survival rate was not satisfying. Additional strategies, especially combination therapies, has been initiated and been further promising. Attempts to identify novel and well-suited predictive biomarkers are also sensed. In this review, the promotion of cancer immunotherapy targeting PD-1 immunoinhibitory pathway is discussed.

Immunogenic neoantigens derived from gene fusions stimulate T cell responses.

Abstract: Anti-tumor immunity is driven by self versus non-self discrimination. Many immunotherapeutic approaches to cancer have taken advantage of tumor neoantigens derived from somatic mutations. Here, we demonstrate that gene fusions are a source of immunogenic neoantigens that can mediate responses to immunotherapy. We identified an exceptional responder with metastatic head and neck cancer who experienced a complete response to immune checkpoint inhibitor therapy, despite a low mutational load and minimal pre-treatment immune infiltration in the tumor. Using whole-genome sequencing and RNA sequencing, we identified a novel gene fusion and demonstrated that it produces a neoantigen that can specifically elicit a host cytotoxic T cell response. In a cohort of head and neck tumors with low mutation burden, minimal immune infiltration and prevalent gene fusions, we also identified gene fusion-derived neoantigens that generate cytotoxic T cell responses. Finally, analyzing additional datasets of fusion-positive cancers, including checkpoint-inhibitor-treated tumors, we found evidence of immune surveillance resulting in negative selective pressure against gene fusion-derived neoantigens. These findings highlight an important class of tumor-specific antigens and have implications for targeting gene fusion events in cancers that would otherwise be less poised for response to immunotherapy, including cancers with low mutational load and minimal immune infiltration. Fusion proteins in cancers with low mutational burden represent functional neoantigens that elicit T cell activation and mediate responses to immunotherapy.

Tissue-resident memory CD8 + T cells promote melanoma-immune equilibrium in skin

Abstract: The immune system can suppress tumour development both by eliminating malignant cells and by preventing the outgrowth and spread of cancer cells that resist eradication1. Clinical and experimental data suggest that the latter mode of control-termed cancer-immune equilibrium1-can be maintained for prolonged periods of time, possibly up to several decades2-4. Although cancers most frequently originate in epithelial layers, the nature and spatiotemporal dynamics of immune responses that maintain cancer-immune equilibrium in these tissue compartments remain unclear. Here, using a mouse model of transplantable cutaneous melanoma5, we show that tissue-resident memory CD8+ T cells (TRM cells) promote a durable melanoma-immune equilibrium that is confined to the epidermal layer of the skin. A proportion of mice (~40%) transplanted with melanoma cells remained free of macroscopic skin lesions long after epicutaneous inoculation, and generation of tumour-specific epidermal CD69+ CD103+ TRM cells correlated with this spontaneous disease control. By contrast, mice deficient in TRM formation were more susceptible to tumour development. Despite being tumour-free at the macroscopic level, mice frequently harboured melanoma cells in the epidermal layer of the skin long after inoculation, and intravital imaging revealed that these cells were dynamically surveyed by TRM cells. Consistent with their role in melanoma surveillance, tumour-specific TRM cells that were generated before melanoma inoculation conferred profound protection from tumour development independently of recirculating T cells. Finally, depletion of TRM cells triggered tumour outgrowth in a proportion (~20%) of mice with occult melanomas, demonstrating that TRM cells can actively suppress cancer progression. Our results show that TRM cells have a fundamental role in the surveillance of subclinical melanomas in the skin by maintaining cancer-immune equilibrium. As such, they provide strong impetus for exploring these cells as targets of future anticancer immunotherapies.