PTPN2 regulates the generation of exhausted CD8+ T cell subpopulations and restrains tumor immunity

Enhanced immune memory through a constant photothermal-metabolism regulation for cancer prevention and treatment

Tumor vaccine inducing effective and perdurable antitumor immunity has a great potential for cancer prevention and therapy. The key indicator for a successful tumor vaccine is boosting the immune system to produce more memory T cells. Although many tumor vaccines have been designed, few of them involve in actively regulating immune memory CD8+T cells. Here a tumor vaccine vector (TA-Met@MS) by encapsulating tumor antigen (TA), metformin (Met) and Hollow gold nanospheres (HAuNS) into poly (lactic-co-glycolic acid) (PLGA) microspheres was presented. TA via the treatment of photothermal therapy (PTT) showed high immunogenicity and immune-adjuvant effectiveness. And NIR light-mediated photothermal effect can lead to a pulsed-release behavior of TA and Met from the microspheres. The released TA can regulate primary T cell expansion and contraction, and stimulate the production of effector T cells at the early immunization stage. The metabolic behavior of the cells is then intervened from glycolysis into fatty acids oxidation (FAO) through the activation of AMPK mediated by Met, which can enhance T cell survival and facilitate the differentiation of memory CD8+T cells. This study may present a valuable insight to design tumor vaccine for enhanced cancer prevention and therapy.

Counteracting CAR T cell dysfunction

In spite of high rates of complete remission following chimeric antigen receptor (CAR) T cell therapy, the efficacy of this approach is limited by generation of dysfunctional CAR T cells in vivo, conceivably induced by immunosuppressive tumor microenvironment (TME) and excessive antigen exposure. Exhaustion and senescence are two critical dysfunctional states that impose a pivotal hurdle for successful CAR T cell therapies. Recently, modified CAR T cells with an "exhaustion-resistant" phenotype have shown superior antitumor functions and prolonged lifespan. In addition, several studies have indicated the feasibility of senescence delay in CAR T cells. Here, we review the latest reports regarding blockade of CAR T cell exhaustion and senescence with a particular focus on the exhaustion-inducing pathways. Subsequently, we describe what potential these latest insights offer for boosting the potency of adoptive cell transfer (ACT) therapies involving CAR T cells. Furthermore, we discuss how induction of costimulation, cytokine exposure, and TME modulation can impact on CAR T cell efficacy and persistence, while potential safety issues associated with reinvigorated CAR T cells will also be addressed.

Exhausted T cells and epigenetic status

Exhausted T cells are a group of dysfunctional T cells, which are present in chronic infections or tumors. The most significant characteristics of exhausted T cells are attenuated effector cytotoxicity, reduced cytokine production, and upregulation of multiple inhibitory molecular receptors (e.g., PD-1, TIM-3, and LAG-3). The intracellular metabolic changes, altered expression of transcription factors, and a unique epigenetic landscape constitute the exhaustion program. Recently, researchers have made progress in understanding exhausted T cells, with the definition and identification of exhausted T cells changing from phenotype-based to being classified at the transcriptional and epigenetic levels. Recent studies have revealed that exhausted T cells can be separated into two subgroups, namely TCF1⁺PD-1⁺ progenitor-like precursor exhausted cells and TCF1^-PD-1⁺ terminally differentiated exhausted T cells. Moreover, the progenitor-like precursor cell population may be a subset of T cells that can respond to immunotherapy. Studies have also found that TOX initiates and dominates the development of exhausted T cells at the transcriptional and epigenetic levels. TOX also maintains T cell survival and may affect decisions regarding treatment strategies. In this review, we discuss the latest developments in T cell exhaustion in regards to definitions, subpopulations, development mechanisms, differences in diverse diseases, and treatment prospects for exhausted T cells. Furthermore, we hypothesize that the epigenetic state regulated by TOX might be the key point, which can determine the reversibility of exhaustion and the efficacy of immunotherapy.

Single-cell RNA-sequencing analyses identify heterogeneity of CD8+ T cell subpopulations and novel therapy targets in melanoma

CD8⁺ T cells are crucial to establish antitumor immunity, and their high infiltration associates with favorable prognoses. However, several CD8⁺ T cell subpopulations in the tumor microenvironment may play different roles in prognosis, progression, and immunotherapy. Here, we analyzed prior published single-cell RNA-sequencing (scRNA-seq) melanoma data to explore the heterogeneity of CD8⁺ T cell subpopulations and identified 7 major subpopulations. We found that high infiltration of exhausted CD8⁺ T cell subpopulation 2 would contribute to unfavorable prognoses. In contrast, a large proportion of naive/memory cells and cytotoxic CD8⁺ T cell subpopulation 3 would lead to favorable prognoses. Notably, the proportion of the cytotoxic CD8⁺ T cell subpopulation 3 would decrease in later-stage melanoma samples, while that of the exhausted CD8⁺ T cell subpopulation 2 would increase. We also found that high abnormal activities of metabolic pathways existed in exhausted CD8⁺ T cell subpopulation 1. Significantly, immunosuppressive checkpoints PD-1 and CTLA-4 signaling pathways were upregulated in exhausted CD8⁺ T cell subpopulations. In addition, a dynamic transcript landscape of immune checkpoints among different subpopulations was also depicted in this study. Moreover, we identified three overexpressed genes (PMEL, TYRP1, and EDNRB) that were significantly correlated to poor prognoses and only expressed in exhausted CD8⁺ T cell subpopulation 2. Importantly, they showed the highest expression in melanoma samples compared to other tumors. In general, we characterized the CD8⁺ T cell subpopulations in melanoma and identified that not only genes of immunosuppressive checkpoints but also PMEL, TYRP1, and EDNRB could serve as potential targets for melanoma therapy.

Modulation of TCR Signaling by Tyrosine Phosphatases: From Autoimmunity to Immunotherapy

Early TCR signaling is dependent on rapid phosphorylation and dephosphorylation of multiple signaling and adaptor proteins, leading to T cell activation. This process is tightly regulated by an intricate web of interactions between kinases and phosphatases. A number of tyrosine phosphatases have been shown to modulate T cell responses and thus alter T cell fate by negatively regulating early TCR signaling. Mutations in some of these enzymes are associated with enhanced predisposition to autoimmunity in humans, and mouse models deficient in orthologous genes often show T cell hyper-activation. Therefore, phosphatases are emerging as potential targets in situations where it is desirable to enhance T cell responses, such as immune responses to tumors. In this review, we summarize the current knowledge about tyrosine phosphatases that regulate early TCR signaling and discuss their involvement in autoimmunity and their potential as targets for tumor immunotherapy.

Precision Tools in Immuno-Oncology: Synthetic Gene Circuits for Cancer Immunotherapy

Engineered mammalian cells for medical purposes are becoming a clinically relevant reality thanks to advances in synthetic biology that allow enhanced reliability and safety of cell-based therapies. However, their application is still hampered by challenges including time-consuming design-and-test cycle iterations and costs. For example, in the field of cancer immunotherapy, CAR-T cells targeting CD19 have already been clinically approved to treat several types of leukemia, but their use in the context of solid tumors is still quite inefficient, with additional issues related to the adequate quality control for clinical use. These limitations can be overtaken by innovative bioengineering approaches currently in development. Here we present an overview of recent synthetic biology strategies for mammalian cell therapies, with a special focus on the genetic engineering improvements on CAR-T cells, discussing scenarios for the next generation of genetic circuits for cancer immunotherapy.

CD4+ T cell exhaustion leads to adoptive transfer therapy failure which can be prevented by immune checkpoint blockade

Cytotoxic CD8⁺ T cell exhaustion is one of the mechanisms underlying the tumor immune escape. The paradigm-shifting immune checkpoint therapy can mitigate CD8⁺ T lymphocyte exhaustion, reinvigorate the anticancer immunity, and achieve durable tumor regression for some patients. Emerging evidence indicates that CD4⁺ T lymphocytes also have a critical role in anticancer immunity, either by directly applying cytotoxicity toward cancer cells or as a helper to augment CD8⁺ T cell cytotoxicity. Whether anticancer CD4⁺ T lymphocytes undergo exhaustion during immunotherapy of solid tumors remains unknown. Here we report that melanoma antigen TRP-1/gp75-specific CD4⁺ T lymphocytes exhibit an exhaustion phenotype after being adoptively transferred into mice bearing large subcutaneous melanoma. Exhaustion of these CD4⁺ T lymphocytes is accompanied with reduced cytokine release and increased expression of inhibitory receptors, resulting in loss of tumor control. Importantly, we demonstrate that PD-L1 immune checkpoint blockade can prevent exhaustion, induce proliferation of the CD4⁺ T lymphocytes, and consequently prevent tumor recurrence. Therefore, when encountering an excessive amount of tumor antigens, tumor-reactive CD4⁺ T lymphocytes also enter the exhaustion state, which can be prevented by immune checkpoint blockade. Our results highlight the importance of tumor-specific CD4⁺ T lymphocytes in antitumor immunity and suggest that the current immune checkpoint blockade therapy may achieve durable anticancer efficacy by rejuvenating both tumor antigen-specific CD8⁺ T lymphocytes and CD4⁺ T lymphocytes.

Induction of Progenitor Exhausted Tissue-Resident Memory CD8+ T Cells Upon Salmonella Typhi Porins Adjuvant Immunization Correlates With Melanoma Control and Anti-PD-1 Immunotherapy Cooperation

Immunotherapy has improved the clinical response in melanoma patients, although a relevant percentage of patients still cannot be salvaged. The search for the immune populations that provide the best tumor control and that can be coaxed by immunotherapy strategies is a hot topic in cancer research nowadays. Tumor-infiltrating TCF-1⁺ progenitor exhausted CD8⁺ T cells seem to grant the best melanoma prognosis and also efficiently respond to anti-PD-1 immunotherapy, giving rise to a TIM-3⁺ terminally exhausted population with heightened effector activity. We tested Porins from Salmonella Typhi as a pathogen associated molecular pattern adjuvant of natural or model antigen in prophylactic and therapeutic immunization approaches against murine melanoma. Porins induced protection against melanomas, even upon re-challenging of tumor-free mice. Porins efficiently expanded IFN-γ-producing CD8⁺ T cells and induced central and effector memory in lymph nodes and tissue-resident (Trm) T cells in the skin and tumors. Porins induced TCF-1⁺ PD-1⁺ CD8⁺ Trm T cells in the tumor stroma and the presence of this population correlated with melanoma growth protection in mice. Porins immunization also cooperated with anti-PD-1 immunotherapy to hamper melanoma growth. Importantly, the potentially protective Trm populations induced by Porins in the murine model were also observed in melanoma patients in which their presence also correlated with disease control. Our data support the use of cancer vaccination to sculpt the tumor stroma with efficient and lasting Trm T cells with effector activities, highlighting the use of Porins as an adjuvant. Furthermore, our data place CD8⁺ Trm T cells with a progenitor exhausted phenotype as an important population for melanoma control, either independently or in cooperation with anti-PD-1 immunotherapy.

PTPN2 links colonic and joint inflammation in experimental autoimmune arthritis

Loss-of-function variants of protein tyrosine phosphatase non-receptor type 2 (PTPN2) enhance risk of inflammatory bowel disease and rheumatoid arthritis; however, whether the association between PTPN2 and autoimmune arthritis depends on gut inflammation is unknown. Here we demonstrate that induction of subclinical intestinal inflammation exacerbates development of autoimmune arthritis in SKG mice. Ptpn2-haploinsufficient SKG mice — modeling human carriers of disease-associated variants of PTPN2 — displayed enhanced colitis-induced arthritis and joint accumulation of Tregs expressing RAR-related orphan receptor γT (RORγt) — a gut-enriched Treg subset that can undergo conversion into FoxP3^–IL-17⁺ arthritogenic exTregs. SKG colonic Tregs underwent higher conversion into arthritogenic exTregs when compared with peripheral Tregs, which was exacerbated by haploinsufficiency of Ptpn2. Ptpn2 haploinsufficiency led to selective joint accumulation of RORγt-expressing Tregs expressing the colonic marker G protein–coupled receptor 15 (GPR15) in arthritic mice and selectively enhanced conversion of GPR15⁺ Tregs into exTregs in vitro and in vivo. Inducible Treg-specific haploinsufficiency of Ptpn2 enhanced colitis-induced SKG arthritis and led to specific joint accumulation of GPR15⁺ exTregs. Our data validate the SKG model for studies at the interface between intestinal and joint inflammation and suggest that arthritogenic variants of PTPN2 amplify the link between gut inflammation and arthritis through conversion of colonic Tregs into exTregs.

Loss of protein tyrosine phosphatase non-receptor type 2 amplifies the link between gut and joint inflammation through conversion of colonic Tregs into arthritogenic exTregs.

Cellular and Molecular Mechanisms of CD8+ T Cell Differentiation, Dysfunction and Exhaustion

T cells follow a triphasic distinct pathway of activation, proliferation and differentiation before becoming functionally and phenotypically “exhausted” in settings of chronic infection, autoimmunity and in cancer. Exhausted T cells progressively lose canonical effector functions, exhibit altered transcriptional networks and epigenetic signatures and gain constitutive expression of a broad coinhibitory receptor suite. This review outlines recent advances in our understanding of exhausted T cell biology and examines cellular and molecular mechanisms by which a state of dysfunction or exhaustion is established, and mechanisms by which exhausted T cells may still contribute to pathogen or tumour control. Further, this review describes our understanding of exhausted T cell heterogeneity and outlines the mechanisms by which checkpoint blockade differentially engages exhausted T cell subsets to overcome exhaustion and recover T cell function.

Oncogenic Tyrosine Phosphatases: Novel Therapeutic Targets for Melanoma Treatment

Despite a large number of therapeutic options available, malignant melanoma remains a highly fatal disease, especially in its metastatic forms. The oncogenic role of protein tyrosine phosphatases (PTPs) is becoming increasingly clear, paving the way for novel antitumor treatments based on their inhibition. In this review, we present the oncogenic PTPs contributing to melanoma progression and we provide, where available, a description of new inhibitory strategies designed against these enzymes and possibly useful in melanoma treatment. Considering the relevance of the immune infiltrate in supporting melanoma progression, we also focus on the role of PTPs in modulating immune cell activity, identifying interesting therapeutic options that may support the currently applied immunomodulating approaches. Collectively, this information highlights the value of going further in the development of new strategies targeting oncogenic PTPs to improve the efficacy of melanoma treatment.

A bilateral tumor model identifies transcriptional programs associated with patient response to immune checkpoint blockade

Immune checkpoint blockade (ICB) has revolutionized treatment of many cancer types, but the majority of treated patients still do not respond to ICB. There is an urgent need to identify predictive biomarkers of response prior to or shortly after therapy initiation, as well as the underlying mechanisms. Here we utilize a model of bilateral tumor implantations followed by resection and immunotherapy-response assessment to study the tumor microenvironment shortly following treatment, identifying biomarkers for response or resistance at early time points. Our biomarker gene signatures derived from CD8⁺ T cells significantly segregate patients by survival and associate with patient response to ICB. Our findings provide a general approach for studying mechanisms of resistance to ICB and discovering predictive biomarkers of response.

Immune checkpoint blockade (ICB) is efficacious in many diverse cancer types, but not all patients respond. It is important to understand the mechanisms driving resistance to these treatments and to identify predictive biomarkers of response to provide best treatment options for all patients. Here we introduce a resection and response-assessment approach for studying the tumor microenvironment before or shortly after treatment initiation to identify predictive biomarkers differentiating responders from nonresponders. Our approach builds on a bilateral tumor implantation technique in a murine metastatic breast cancer model (E0771) coupled with anti-PD-1 therapy. Using our model, we show that tumors from mice responding to ICB therapy had significantly higher CD8⁺ T cells and fewer Gr1⁺CD11b⁺ myeloid-derived suppressor cells (MDSCs) at early time points following therapy initiation. RNA sequencing on the intratumoral CD8⁺ T cells identified the presence of T cell exhaustion pathways in nonresponding tumors and T cell activation in responding tumors. Strikingly, we showed that our derived response and resistance signatures significantly segregate patients by survival and associate with patient response to ICB. Furthermore, we identified decreased expression of CXCR3 in nonresponding mice and showed that tumors grown in Cxcr3^−/− mice had an elevated resistance rate to anti-PD-1 treatment. Our findings suggest that the resection and response tumor model can be used to identify response and resistance biomarkers to ICB therapy and guide the use of combination therapy to further boost the antitumor efficacy of ICB.

A Five-Gene Signature Based on Stromal/Immune Scores in the Tumor Microenvironment and Its Clinical Implications for Liver Cancer

Increasing evidence highlights the clinical significance of stromal cells and immune cells in the liver cancer microenvironment. However, reliable prognostic models have not been well established. This study aimed to develop a gene signature for liver cancer based on stromal and immune scores. Using the estimation of stromal and immune cells in malignant tumor tissues using expression data (ESTIMATE) algorithm, stromal and immune scores were estimated based on the transcriptome profile of The Cancer Genome Atlas (TCGA) liver cancer cohort. Stromal-/immune-related differentially expressed genes were identified, followed by functional enrichment analysis. The Cox regression model was used to select prognostic genes and construct a gene signature. Its predictive potential was evaluated by receiver operating characteristic (ROC). The correlation between the risk score and immune cell infiltration was analyzed using Tumor Immune Estimation Resource (TIMER). Three hundred sixty-four upregulated and 10 downregulated stromal-/immune-related genes were identified, were mainly enriched in immune-related processes and pathways. Through univariate and multivariate cox survival analysis, a five-gene risk score was constructed, composed of FABP3, HTRA3, OLFML2B, PDZD4 and SLAMF6. Patients with high score indicated a poorer prognosis than those with low risk score. The areas under the ROC curves of overall survival (OS), progression-free interval, 3-, 5-year, OS status were 0.68, 0.57, 0.72, 0.74 and 0.728, indicating its well performance on predicting patients' prognoses. Furthermore, the risk score and the five genes were significantly correlated with immune cell infiltration in the tumor microenvironment. In this study, we proposed a prognostic five-gene signature based on stromal/immune scores in the liver cancer microenvironment.

PTPN2 Deficiency Enhances Programmed T Cell Expansion and Survival Capacity of Activated T Cells

Manipulating molecules that impact T cell receptor (TCR) or cytokine signaling, such as the protein tyrosine phosphatase non-receptor type 2 (PTPN2), has significant potential for advancing T cell-based immunotherapies. Nonetheless, it remains unclear how PTPN2 impacts the activation, survival, and memory formation of T cells. We find that PTPN2 deficiency renders cells in vivo and in vitro less dependent on survival-promoting cytokines, such as interleukin (IL)-2 and IL-15. Remarkably, briefly ex vivo-activated PTPN2-deficient T cells accumulate in 3- to 11-fold higher numbers following transfer into unmanipulated, antigen-free mice. Moreover, the absence of PTPN2 augments the survival of short-lived effector T cells and allows them to robustly re-expand upon secondary challenge. Importantly, we find no evidence for impaired effector function or memory formation. Mechanistically, PTPN2 deficiency causes broad changes in the expression and phosphorylation of T cell expansion and survival-associated proteins. Altogether, our data underline the therapeutic potential of targeting PTPN2 in T cell-based therapies to augment the number and survival capacity of antigen-specific T cells.

Cancer and HIV-1 Infection: Patterns of Chronic Antigen Exposure

The main role of the human immune system is to eliminate cells presenting foreign antigens and abnormal patterns, while maintaining self-tolerance. However, when facing highly variable pathogens or antigens very similar to self-antigens, this system can fail in completely eliminating the anomalies, leading to the establishment of chronic pathologies. Prototypical examples of immune system defeat are cancer and Human Immunodeficiency Virus-1 (HIV-1) infection. In both conditions, the immune system is persistently exposed to antigens leading to systemic inflammation, lack of generation of long-term memory and exhaustion of effector cells. This triggers a negative feedback loop where effector cells are unable to resolve the pathology and cannot be replaced due to the lack of a pool of undifferentiated, self-renewing memory T cells. In addition, in an attempt to reduce tissue damage due to chronic inflammation, antigen presenting cells and myeloid components of the immune system activate systemic regulatory and tolerogenic programs. Beside these homologies shared between cancer and HIV-1 infection, the immune system can be shaped differently depending on the type and distribution of the eliciting antigens with ultimate consequences at the phenotypic and functional level of immune exhaustion. T cell differentiation, functionality, cytotoxic potential and proliferation reserve, immune-cell polarization, upregulation of negative regulators (immune checkpoint molecules) are indeed directly linked to the quantitative and qualitative differences in priming and recalling conditions. Better understanding of distinct mechanisms and functional consequences underlying disease-specific immune cell dysfunction will contribute to further improve and personalize immunotherapy. In the present review, we describe relevant players of immune cell exhaustion in cancer and HIV-1 infection, and enumerate the best-defined hallmarks of T cell dysfunction. Moreover, we highlight shared and divergent aspects of T cell exhaustion and T cell activation to the best of current knowledge.

Chlorin e6 and CRISPR-Cas9 dual-loading system with deep penetration for a synergistic tumoral photodynamic-immunotherapy

Photodynamic therapy (PDT) is a relatively safe and clinically promising treatment to combat primary tumors, especially epidermal carcinoma, while has negligible effects on distant metastasis. Therefore, this work reports a multifunctional nanosystem (HPR@CCP) exerting a combined photodynamic and immunotherapy to amplify the therapeutic effect on primary tumors and distant metastasis. Specifically, this nanosystem was obtained by electrostatic adsorption of a negatively charged hyaluronic acid "shell" with a positively charged "core" consisting of the CRISPR-Cas9 system targeting the Ptpn2 gene (Cas9-Ptpn2) and a modified mitochondria-targeting chlorin e6 (TPP-PEI-Ce6). Cell experiments demonstrated that the HPR@CCP nanoparticles possessed very high transfection efficiency on B16F10 cells, and TPP-PEI-Ce6 in the nanoparticles resulted in a significant PDT efficacy due to the efficient singlet oxygen generation in mitochondria under laser-irradiation. The accumulation of the nanoparticles in the tumor by active and passive tumor-targeting in vivo led to the disruption of the Ptpn2 gene by the Cas9-Ptpn2 plasmids in the nanocarriers, thus sensitizing tumors to immunotherapy by the increase of the IFN-γ and TNF-α signaling and the promotion of the proliferation of CD8⁺ T cells. In addition, Hyaluronidase was administered in advance to destroy the hyaluronic acid in the condensed extracellular matrix and to remove the hyaluronic acid "shell" from the nanosystem, subsequently leading to an enhanced penetration of oxygen and therapeutic agents. Fortunately, the primary and distant tumors in the experimental animals were remarkably inhibited after the combination of PDT-immunotherapy, thus, this easy-to-built nanomedicine could be used as a potential combination therapy against tumors.

The expression patterns and the diagnostic/prognostic roles of PTPN family members in digestive tract cancers

Background

Non-receptor protein tyrosine phosphatases (PTPNs) are a set of enzymes involved in the tyrosyl phosphorylation. The present study intended to clarify the associations between the expression patterns of PTPN family members, and diagnosis as well as the prognosis of digestive tract cancers.

Methods

Oncomine and Ualcan were used to analyze PTPN expressions. Data from The Cancer Genome Atlas (TCGA) were downloaded through UCSC Xena for validation and to explore the relationship of the PTPN expression with diagnosis, clinicopathological parameters and survival of digestive tract cancers. Gene ontology enrichment analysis was conducted using the DAVID database. The gene–gene interaction network was performed by GeneMANIA and the protein–protein interaction (PPI) network was built using STRING portal coupled with Cytoscape. The expression of differentially expressed PTPNs in cancer cell lines were explored using CCLE. Moreover, by histological verification, the expression of four PTPNs in digestive tract cancers were further analyzed.

Results

Most PTPN family members were associated with digestive tract cancers according to Oncomine, Ualcan and TCGA data. Several PTPN members were differentially expressed in digestive tract cancers. For esophageal carcinoma (ESCA), PTPN1 and PTPN12 levels were correlated with incidence; PTPN20 was associated with poor prognosis. For stomach adenocarcinoma (STAD), PTPN2 and PTPN12 levels were correlated with incidence; PTPN3, PTPN5, PTPN7, PTPN11, PTPN13, PTPN14, PTPN18 and PTPN23 were correlated with pathological grade; PTPN20 expression was related with both TNM stage and N stage; PTPN22 was associated with T stage and pathological grade; decreased expression of PTPN5 and PTPN13 implied worse overall survival of STAD, while elevated PTPN6 expression indicated better prognosis. For colorectal cancer (CRC), PTPN2, PTPN21 and PTPN22 levels were correlated with incidence; expression of PTPN5, PTPN12, and PTPN14 was correlated with TNM stage and N stage; high PTPN5 or PTPN7 expression was associated with increased hazards of death. CCLE analyses showed that in esophagus cancer cell lines, PTPN1, PTPN4 and PTPN12 were highly expressed; in gastric cancer cell lines, PTPN2 and PTPN12 were highly expressed; in colorectal cancer cell lines, PTPN12 was highly expressed while PTPN22 was downregulated. Results of histological verification experiment showed differential expressions of PTPN22 in CRC, and PTPN12 in GC and CRC.

Conclusions

Members of PTPN family were differentially expressed in digestive tract cancers. Correlations were found between PTPN genes and clinicopathological parameters of patients. Expression of PTPN12 was upregulated in both STAD and CRC, and thus could be used as a diagnostic biomarker. Differential expression of PTPN12 in GC and CRC, and PTPN22 in CRC were presented in our histological verification experiment.

Engineering bionic T cells: signal 1, signal 2, signal 3, reprogramming and the removal of inhibitory mechanisms

Gene engineering and combinatorial approaches with other cancer immunotherapy agents may confer capabilities enabling full tumor rejection by adoptive T cell therapy (ACT). The provision of proper costimulatory receptor activity and cytokine stimuli, along with the repression of inhibitory mechanisms, will conceivably make the most of these treatment strategies. In this sense, T cells can be genetically manipulated to become refractory to suppressive mechanisms and exhaustion, last longer and differentiate into memory T cells while endowed with the ability to traffic to malignant tissues. Their antitumor effects can be dramatically augmented with permanent or transient gene transfer maneuvers to express or delete/repress genes. A combination of such interventions seeks the creation of the ultimate bionic T cell, perfected to seek and destroy cancer cells upon systemic or local intratumor delivery.

PD-1+ Tim3+ tumor-infiltrating CD8 T cells sustain the potential for IFN-γ production, but lose cytotoxic activity in ovarian cancer

Persistent exposure to tumor antigens results in exhausted tumor-infiltrating T cells (TILs) that express the immune checkpoint molecules, PD-1 and Tim3, and lack anti-tumor immunity. To examine the exhausted status of TILs in ovarian cancer, the potential for cytokine production, proliferation and cytotoxicity by purified PD-1+ Tim3+ CD8 TILs was assessed. The production of IFN-γ and TNF-α by PD-1+ Tim3+ CD8 TILs remained the same in an intracellular cytokine staining assay and was higher in a cytokine catch assay than that by PD-1- Tim3- and PD-1+ Tim3- CD8 TILs. %Ki67+ was higher in PD-1+ Tim3+ CD8 TILs than in PD-1- Tim3- CD8 TILs. However, patients with high PD-1+ Tim3+ CD8 TILs had a poor prognosis. The potential for cytotoxicity was then examined. %Perforin+ and %granzyme B+ were lower in PD-1+ Tim3+ CD8 TILs than in PD-1- Tim3- and PD-1+ Tim3- CD8 TILs. To observe the potential for direct cytotoxicity by T cells, a target cell line expressing membrane-bound anti-CD3scFv was newly established and a cytotoxic assay targeting these cells was performed. The cytotoxicity of PD-1+ Tim3+ CD8 TILs was significantly lower than that of PD-1- Tim3- and PD-1+ Tim3- CD8 TILs. Even though PD-1+ Tim3+ CD8 TILs in ovarian cancer showed a sustained potential for cytokine production and proliferation, cytotoxicity was markedly impaired, which may contribute to the poor prognosis of patients with ovarian cancer. Among the impaired functions of exhausted TILs, cytotoxicity may be an essential target for cancer immunotherapy.

CRISPR screen in mechanism and target discovery for cancer immunotherapy

CRISPR/Cas-based genetic perturbation screens have emerged as powerful tools for large-scale identification of new targets for cancer immunotherapy. Various strategies of CRISPR screen have been used for immune-oncology (IO) target discovery. The genomic sequences targeted by CRISPR/Cas system range from coding sequences to non-coding RNA/DNA, including miRNAs, LncRNAs, circRNAs, promoters, and enhancers, which may be potential targets for future pharmacological and therapeutic interventions. Rapid progresses have been witnessed in finding novel targets for enhancing tumor antigen presentation, sensitizing of tumor cells to immune-mediated cytotoxicity, and reinvigorating tumor-specific T cells by using CRISPR technologies. In combination with other strategies, the detailed characteristics of the targets for immunotherapy have been obtained by CRISPR screen. In this review, we present an overview of recent progresses in the development of CRISPR-based screens for IO target identification and discuss the challenges and possible solutions in this rapidly growing field.

CD8+ T cell states in human cancer: insights from single-cell analysis

The T cell infiltrates that are formed in human cancers are a modifier of natural disease progression and also determine the probability of clinical response to cancer immunotherapies. Recent technological advances that allow the single-cell analysis of phenotypic and transcriptional states have revealed a vast heterogeneity of intratumoural T cell states, both within and between patients, and the observation of this heterogeneity makes it critical to understand the relationship between individual T cell states and therapy response. This Review covers our current knowledge of the T cell states that are present in human tumours and the role that different T cell populations have been hypothesized to play within the tumour microenvironment, with a particular focus on CD8⁺ T cells. The three key models that are discussed herein are as follows: (1) the dysfunction of T cells in human cancer is associated with a change in T cell functionality rather than inactivity; (2) antigen recognition in the tumour microenvironment is an important driver of T cell dysfunctionality and the presence of dysfunctional T cells can hence be used as a proxy for the presence of a tumour-reactive T cell compartment; (3) a less dysfunctional population of tumour-reactive T cells may be required to drive a durable response to T cell immune checkpoint blockade.

Determinants of Resistance to Checkpoint Inhibitors

The development of immune checkpoint inhibitors (ICIs) has drastically altered the landscape of cancer treatment. Since approval of the first ICI for the treatment of advanced melanoma in 2011, several therapeutic agents have been Food and Drug Administration (FDA)-approved for multiple cancers, and hundreds of clinical trials are currently ongoing. These antibodies disrupt T-cell inhibitory pathways established by tumor cells and thus re-activate the host’s antitumor immune response. While successful in many cancers, several types remain relatively refractory to treatment or patients develop early recurrence. Hence, there is a great need to further elucidate mechanisms of resistant disease and determine novel, effective, and tolerable combination therapies to enhance efficacy of ICIs.

Fatty Acid Oxidation Controls CD8+ Tissue-Resident Memory T-cell Survival in Gastric Adenocarcinoma

The success of checkpoint inhibitors in cancer treatment is associated with the infiltration of tissue-resident memory T (Trm) cells. In this study, we found that about 30% of tumor-infiltrating lymphocytes (TIL) in the tumor microenvironment of gastric adenocarcinoma were CD69⁺CD103⁺ Trm cells. Trm cells were low in patients with metastasis, and the presence of Trm cells was associated with better prognosis in patients with gastric adenocarcinoma. Trm cells expressed high PD-1, TIGIT, and CD39 and represented tumor-reactive TILs. Instead of utilizing glucose, Trm cells relied on fatty acid oxidation for cell survival. Deprivation of fatty acid resulted in Trm cell death. In a tumor cell-T-cell coculture system, gastric adenocarcinoma cells outcompeted Trm cells for lipid uptake and induced Trm cell death. Targeting PD-L1 decreased fatty acid binding protein (Fabp) 4 and Fabp5 expression in tumor cells of gastric adenocarcinoma. In contrast, the blockade of PD-L1 increased Fabp4/5 expression in Trm cells, promoting lipid uptake by Trm cells and resulting in better survival of Trm cells in vitro and in vivo. PD-L1 blockade unleashed Trm cells specifically in the patient-derived xenograft (PDX) mice. PDX mice that did not respond to PD-L1 blockade had less Trm cells than responders. Together, these data demonstrated that Trm cells represent a subset of TILs in the antitumor immune response and that metabolic reprogramming could be a promising way to prolong the longevity of Trm cells and enhance antitumor immunity in gastric adenocarcinoma.