Anti-CTLA-4 therapy broadens the melanoma-reactive CD8+ T cell response

Identification of neoantigens for individualized therapeutic cancer vaccines

Somatic mutations in cancer cells can generate tumour-specific neoepitopes, which are recognized by autologous T cells in the host. As neoepitopes are not subject to central immune tolerance and are not expressed in healthy tissues, they are attractive targets for therapeutic cancer vaccines. Because the vast majority of cancer mutations are unique to the individual patient, harnessing the full potential of this rich source of targets requires individualized treatment approaches. Many computational algorithms and machine-learning tools have been developed to identify mutations in sequence data, to prioritize those that are more likely to be recognized by T cells and to design tailored vaccines for every patient. In this Review, we fill the gaps between the understanding of basic mechanisms of T cell recognition of neoantigens and the computational approaches for discovery of somatic mutations and neoantigen prediction for cancer immunotherapy. We present a new classification of neoantigens, distinguishing between guarding, restrained and ignored neoantigens, based on how they confer proficient antitumour immunity in a given clinical context. Such context-based differentiation will contribute to a framework that connects neoantigen biology to the clinical setting and medical peculiarities of cancer, and will enable future neoantigen-based therapies to provide greater clinical benefit.

Addressing the Elephant in the Immunotherapy Room: Effector T-Cell Priming versus Depletion of Regulatory T-Cells by Anti-CTLA-4 Therapy

Cytotoxic T-lymphocyte Associated Protein 4 (CTLA-4) is an immune checkpoint molecule highly expressed on regulatory T-cells (Tregs) that can inhibit the activation of effector T-cells. Anti-CTLA-4 therapy can confer long-lasting clinical benefits in cancer patients as a single agent or in combination with other immunotherapy agents. However, patient response rates to anti-CTLA-4 are relatively low, and a high percentage of patients experience severe immune-related adverse events. Clinical use of anti-CTLA-4 has regained interest in recent years; however, the mechanism(s) of anti-CTLA-4 is not well understood. Although activating T-cells is regarded as the primary anti-tumor mechanism of anti-CTLA-4 therapies, mounting evidence in the literature suggests targeting intra-tumoral Tregs as the primary mechanism of action of these agents. Tregs in the tumor microenvironment can suppress the host anti-tumor immune responses through several cell contact-dependent and -independent mechanisms. Anti-CTLA-4 therapy can enhance the priming of T-cells by blockading CD80/86-CTLA-4 interactions or depleting Tregs through antibody-dependent cellular cytotoxicity and phagocytosis. This review will discuss proposed fundamental mechanisms of anti-CTLA-4 therapy, novel uses of anti-CTLA-4 in cancer treatment and approaches to improve the therapeutic efficacy of anti-CTLA-4.

Tumor-associated high endothelial venules mediate lymphocyte entry into tumors and predict response to PD-1 plus CTLA-4 combination immunotherapy

Recruitment of lymphocytes into tumors is critical for anti-tumor immunity and efficacious immunotherapy. We show in murine models that tumor-associated high endothelial venules (TA-HEVs) are major sites of lymphocyte entry into tumors at baseline and upon treatment with anti-PD-1/anti-CTLA-4 immune checkpoint blockade (ICB). TA-HEV endothelial cells (TA-HECs) derive from post-capillary venules, co-express MECA-79⁺ HEV sialomucins and E/P-selectins, and are associated with homing and infiltration into tumors of various T cell subsets. Intravital microscopy further shows that TA-HEVs are the main sites of lymphocyte arrest and extravasation into ICB-treated tumors. Increasing TA-HEC frequency and maturation increases the proportion of tumor-infiltrating stem-like CD8⁺ T cells, and ameliorates ICB efficacy. Analysis of tumor biopsies from 93 patients with metastatic melanoma reveals that TA-HEVs are predictive of better response and survival upon treatment with anti-PD-1/anti-CTLA-4 combination. These studies provide critical insights into the mechanisms governing lymphocyte trafficking in cancer immunity and immunotherapy.

Different syngeneic tumors show distinctive intrinsic tumor-immunity and mechanisms of actions (MOA) of anti-PD-1 treatment

Cancers are immunologically heterogeneous. A range of immunotherapies target abnormal tumor immunity via different mechanisms of actions (MOAs), particularly various tumor-infiltrate leukocytes (TILs). We modeled loss of function (LOF) in four common anti-PD-1 antibody-responsive syngeneic tumors, MC38, Hepa1-6, CT-26 and EMT-6, by systematical depleting a series of TIL lineages to explore the mechanisms of tumor immunity and treatment. CD8⁺-T-cells, CD4⁺-T-cells, T_reg, NK cells and macrophages were individually depleted through either direct administration of anti-marker antibodies/reagents or using DTR (diphtheria toxin receptor) knock-in mice, for some syngeneic tumors, where specific subsets were depleted following diphtheria toxin (DT) administration. These LOF experiments revealed distinctive intrinsic tumor immunity and thus different MOAs in their responses to anti-PD-1 antibody among different syngeneic tumors. Specifically, the intrinsic tumor immunity and the associated anti-PD-1 MOA were predominately driven by CD8⁺ cytotoxic TILs (CTL) in all syngeneic tumors, excluding Hepa1-6 where CD4⁺ T_eff TILs played a key role. TIL-T_reg also played a critical role in supporting tumor growth in all four syngeneic models as well as M₂-macrophages. Pathway analysis using pharmacodynamic readouts of immuno-genomics and proteomics on MC38 and Hepa1-6 also revealed defined, but distinctive, immune pathways of activation and suppression between the two, closely associated with the efficacy and consistent with TIL-pharmacodynamic readouts. Understanding tumor immune-pathogenesis and treatment MOAs in the different syngeneic animal models, not only assists the selection of the right model for evaluating new immunotherapy of a given MOA, but also can potentially help to understand the potential disease mechanisms and strategize optimal immune-therapies in patients.

Targeting of pancreatic cancer cells and stromal cells using engineered oncolytic Salmonella typhimurium

Pancreatic cancer is resistant to conventional therapeutic interventions, mainly due to abundant cancer stromal cells and poor immune cell infiltration. Here, we used a targeted cancer therapy approach based on attenuated Salmonella typhimurium engineered to express cytolysin A (ClyA) to target cancer stromal cells and cancer cells and treat pancreatic cancer in mice. Nude mice bearing subcutaneous or orthotopic human pancreatic cancers were treated with engineered S. typhimurium expressing ClyA. The tumor microenvironment was monitored to analyze stromal cell numbers, stromal cell marker expression, and immune cell infiltration. The attenuated bacteria accumulated and proliferated specifically in tumor tissues after intravenous injection. The bacteria secreted ClyA into the tumor microenvironment. A single dose of ClyA-expressing Salmonella markedly inhibited growth of pancreatic cancer both in subcutaneous xenograft- and orthotopic tumor-bearing nude mice. Histological analysis revealed a marked decrease in expression of stromal cell markers and increased immune cell (neutrophils and macrophages) infiltration into tumors after colonization by ClyA-expressing bacteria. ClyA-expressing S. typhimurium destroyed cancer stromal cells and cancer cells in mouse models of human pancreatic cancer. This approach provides a novel strategy for combining anticancer and anti-stromal therapy to treat pancreatic cancer.

Application of T cell receptor (TCR) repertoire analysis for the advancement of cancer immunotherapy

T cell receptor (TCR) sequencing has emerged as a powerful new technology in analysis of the host-tumour interaction. The advances in NextGen sequencing technologies, coupled with powerful novel bioinformatic tools, allow quantitative and reproducible characterisation of repertoires from tumour and blood samples from an increasing number of patients with a variety of solid cancers. In this review, we consider how global metrics such as T cell clonality and diversity can be extracted from these repertoires and used to give insight into the mechanism of action of immune checkpoint blockade. Furthermore, we explore how the analysis of TCR overlap between repertories can help define spatial and temporal heterogeneity of the anti-tumoural immune response. Finally, we review how analysis of TCR sequence and structure, either of individual TCRs or from sets of related TCRs can be used to annotate the antigenic specificity, with important implications for the development of personalised adoptive cellular immunotherapies.

Tumor-associated antigen-specific T cells with nivolumab are safe and persist in vivo in relapsed/refractory Hodgkin lymphoma

Hodgkin lymphoma (HL) Reed Sternberg cells express tumor-associated antigens (TAA) that are potential targets for cellular therapies. We recently demonstrated that TAA-specific T cells (TAA-Ts) targeting WT1, PRAME, and Survivin were safe and associated with prolonged time to progression in solid tumors. Hence, we evaluated whether TAA-Ts when given alone or with nivolumab were safe and could elicit antitumor effects in vivo in patients with relapsed/refractory (r/r) HL. Ten patients were infused with TAA-Ts (8 autologous and 2 allogeneic) for active HL (n = 8) or as adjuvant therapy after hematopoietic stem cell transplant (n = 2). Six patients received nivolumab priming before TAA-Ts and continued until disease progression or unacceptable toxicity. All 10 products recognized 1 or more TAAs and were polyfunctional. Patients were monitored for safety for 6 weeks after the TAA-Ts and for response until disease progression. The infusions were safe with no clear dose-limiting toxicities. Patients receiving TAA-Ts as adjuvant therapy remain in continued remission at 3+ years. Of the 8 patients with active disease, 1 patient had a complete response and 7 had stable disease at 3 months, 3 of whom remain with stable disease at 1 year. Antigen spreading and long-term persistence of TAA-Ts in vivo were observed in responding patients. Nivolumab priming impacted TAA-T recognition and persistence. In conclusion, treatment of patients with r/r HL with TAA-Ts alone or in combination with nivolumab was safe and produced promising results. This trial was registered at www.clinicaltrials.gov as #NCT022039303 and #NCT03843294.

Differential effects of PD-1 and CTLA-4 blockade on the melanoma-reactive CD8 T cell response

Immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) have revolutionized the treatment of melanoma patients. Based on early studies addressing the mechanism of action, it was assumed that PD-1 blockade mostly influences T cell responses at the tumor site. However, recent work has demonstrated that PD-1 blockade can influence the T cell compartment in peripheral blood. If the activation of circulating, tumor-reactive T cells would form an important mechanism of action of PD-1 blockade, it may be predicted that such blockade would alter either the frequency and/or the breadth of the tumor-reactive CD8 T cell response. To address this question, we analyzed CD8 T cell responses toward 71 melanoma-associated epitopes in peripheral blood of 24 melanoma patients. We show that both the frequency and the breadth of the circulating melanoma-reactive CD8 T cell response was unaltered upon PD-1 blockade. In contrast, a broadening of the circulating melanoma-reactive CD8 T cell response was observed upon CTLA-4 blockade, in concordance with our prior data. Based on these results, we conclude that PD-1 and CTLA-4 blockade have distinct mechanisms of action. In addition, the data provide an argument in favor of the hypothesis that anti-PD-1 therapy may primarily act at the tumor site.

The (re)discovery of tumor-intrinsic determinants of immune sensitivity by functional genetic screens

Functional genetic screens by CRISPR-Cas9 allow for the unbiased discovery of proteins causally involved in complex biological processes. In recent years, this approach has been used by multiple laboratories to uncover a range of tumor cell regulators determining immune sensitivity. In this review, we provide an overview of genetic screens carried out both in vitro and in vivo. By comparative analysis we highlight commonly identified proteins and pathways that are key in establishing tumor-intrinsic immune susceptibility. Together, these screens demonstrated the importance of the antigen presentation, interferon-γ, tumor necrosis factor and autophagy pathways in governing sensitivity of tumor cells to immune attack. Moreover, they underline the complex interplay between tumor cells and their microenvironment, providing both fundamental and clinically relevant insights into the mechanisms of tumor immune resistance.

Nanoparticles Targeting Innate Immune Cells in Tumor Microenvironment

A variety of innate immune cells such as macrophages, dendritic cells, myeloid-derived suppressor cells, natural killer cells, and neutrophils in the tumor microenvironments, contribute to tumor progression. However, while several recent reports have studied the use of immune checkpoint-based cancer immunotherapy, little work has focused on modulating the innate immune cells. This review focuses on the recent studies and challenges of using nanoparticles to target innate immune cells. In particular, we also examine the immunosuppressive properties of certain innate immune cells that limit clinical benefits. Understanding the cross-talk between tumors and innate immune cells could contribute to the development of strategies for manipulating the nanoparticles targeting tumor microenvironments.

Differential Immune-Related Microenvironment Determines Programmed Cell Death Protein-1/Programmed Death-Ligand 1 Blockade Efficacy in Patients With Advanced NSCLC

INTRODUCTION

Programmed death-ligand 1 (PD-L1) expression is not a completely reliable predictive marker of the efficacy of anti-programmed cell death protein-1 (PD-1)/PD-L1 therapy in patients with advanced NSCLC. Immune-related tumor microenvironment (TME) is classified into four different types based on the tumor-infiltrating lymphocyte (TIL) status and PD-L1 expression.

METHODS

We retrospectively reviewed patients with advanced NSCLC treated with anti-PD-1/PD-L1 therapy between 2015 and 2019. We investigated the association between the efficacy of anti-PD-1/PD-L1 therapy, the types of TME based on PD-L1 (clone: 22C3) expression, the density of CD8-positive TILs assessed by immunohistochemistry, and mutational profiles by next-generation sequencing.

RESULTS

Overall, 228 patients were included in the analysis. The patients were classified into the following four groups: type I: PD-L1_High (tumor proportion score ≥ 50%)/TIL_High (≥85/mm²; n = 73); type II: PD-L1_Low (tumor proportion score < 50%)/TIL_Low (<85/mm²; n = 70); type III: PD-L1_High/TIL_Low (n = 37); and type IV: PD-L1_Low/TIL_High (n = 48). The objective response rate (ORR) and progression-free survival (PFS) of anti-PD-1/PD-L1 therapy clearly differed according to the different TME types (ORR and PFS; type I: 64%, 14.5 mo; type II: 12%, 2.1 mo; type III: 24%, 3.6 mo; type IV; 41%, 10.8 mo). In patients with PD-L1_High tumors, type I tumors had significantly better ORR and PFS than type III tumors (ORR: p < 0.001 and PFS: p < 0.001). The presence of TP53 and KRAS mutation was related to the density of CD8-positive TILs and PD-L1 expression, respectively.

CONCLUSIONS

Differential types of TME, including PD-L1 expression and TIL status, could accurately predict the efficacy of anti-PD-1/PD-L1 therapy.

Tumour neoantigen mimicry by microbial species in cancer immunotherapy

Tumour neoantigens arising from cancer-specific mutations generate a molecular fingerprint that has a definite specificity for cancer. Although this fingerprint perfectly discriminates cancer from healthy somatic and germline cells, and is therefore therapeutically exploitable using immune checkpoint blockade, gut and extra-gut microbial species can independently produce epitopes that resemble tumour neoantigens as part of their natural gene expression programmes. Such tumour molecular mimicry is likely not only to influence the quality and strength of the body's anti-cancer immune response, but could also explain why certain patients show favourable long-term responses to immune checkpoint blockade while others do not benefit at all from this treatment. This article outlines the requirement for tumour neoantigens in successful cancer immunotherapy and draws attention to the emerging role of microbiome-mediated tumour neoantigen mimicry in determining checkpoint immunotherapy outcome, with far-reaching implications for the future of cancer immunotherapy.

Immunosuppression in Medulloblastoma: Insights into Cancer Immunity and Immunotherapy

OPINION STATEMENT

Medulloblastoma (MB) is the most common pediatric brain malignancy, with a 5-year overall survival (OS) rate of around 65%. The conventional MB treatment, comprising surgical resection followed by irradiation and adjuvant chemotherapy, often leads to impairment in normal body functions and poor quality of life, especially with the increased risk of recurrence and subsequent development of secondary malignancies. The development and progression of MB are facilitated by a variety of immune-evading mechanisms such as the secretion of immunosuppressive molecules, activation of immunosuppressive cells, inhibition of immune checkpoint molecules, impairment of adhesive molecules, downregulation of the major histocompatibility complex (MHC) molecules, protection against apoptosis, and activation of immunosuppressive pathways. Understanding the tumor-immune relationship in MB is crucial for effective development of immune-based therapeutic strategies. In this comprehensive review, we discuss the immunological aspect of the brain, focusing on the current knowledge tackling the mechanisms of MB immune suppression and evasion. We also highlight several key immunotherapeutic approaches developed to date for the treatment of MB.

PD-L1 targeting and subclonal immune escape mediated by PD-L1 mutations in metastatic colorectal cancer

BACKGROUND

In patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC), immune checkpoint blockade is ineffective, and combinatorial approaches enhancing immunogenicity need exploration.

METHODS

We treated 43 patients with predominantly microsatellite stable RAS/BRAF wild-type mCRC on a phase II trial combining chemotherapy with the epidermal growth factor receptor antibody cetuximab and the programmed cell death ligand 1 (PD-L1) antibody avelumab. We performed next-generation gene panel sequencing for mutational typing of tumors and liquid biopsy monitoring as well as digital droplet PCR to confirm individual mutations. Translational analyses included tissue immunohistochemistry, multispectral imaging and repertoire sequencing of tumor-infiltrating T cells. Detected PD-L1 mutations were mechanistically validated in CRISPR/Cas9-generated cell models using qRT-PCR, immunoblotting, flow cytometry, complement-dependent cytotoxicity assay, antibody-dependent cytotoxicity by natural killer cell degranulation assay and LDH release assay as well as live cell imaging of T cell mediated tumor cell killing.

RESULTS

Circulating tumor DNA showed rapid clearance in the majority of patients mirroring a high rate of early tumor shrinkage. In 3 of 13 patients expressing the high-affinity Fcγ receptor 3a (FcγR3a), tumor subclones with PD-L1 mutations were selected that led to loss of tumor PD-L1 by nonsense-mediated RNA decay in PD-L1 K162fs and protein degradation in PD-L1 L88S. As a consequence, avelumab binding and antibody-dependent cytotoxicity were impaired, while T cell killing of these variant clones was increased. Interestingly, PD-L1 mutant subclones showed slow selection dynamics reversing on avelumab withdrawal and patients with such subclones had above-average treatment benefit. This suggested that the PD-L1 mutations mediated resistance to direct antitumor effects of avelumab, while at the same time loss of PD-L1 reduced biological fitness by enhanced T cell killing limiting subclonal expansion.

CONCLUSION

The addition of avelumab to standard treatment appeared feasible and safe. PD-L1 mutations mediate subclonal immune escape to avelumab in some patients with mCRC expressing high-affinity FcγR3a, which may be a subset experiencing most selective pressure. Future trials evaluating the addition of avelumab to standard treatment in MSS mCRC are warranted especially in this patient subpopulation.

TRIAL REGISTRATION NUMBER

NCT03174405.

CD8 T-cell-mediated cerebellitis directed against Purkinje cell antigen after ipilimumab for small cell lung cancer

We report a rapidly progressive and fatal CD8 T-cell-mediated cerebellitis after ipilimumab (cytotoxic T-lymphocyte-associated protein 4 inhibitor) for small cell lung cancer. Clinical features and histopathology were consistent with an accelerated form of paraneoplastic cerebellar degeneration. A patchy CD8 T-cell infiltrate spatially corresponded to areas of Purkinje cell loss, with occasional CD8 polarisation towards Purkinje cells. CD20-positive B cells were sparse. CD8 T-cell-mediated cerebellitis after immune checkpoint inhibitor treatment may recapitulate the early stages of paraneoplastic cerebellar degeneration.

Strong vaccine responses during chemotherapy are associated with prolonged cancer survival

Therapeutic cancer vaccines have effectively induced durable regressions of premalignant oncogenic human papilloma virus type 16 (HPV16)-induced anogenital lesions. However, the treatment of HPV16-induced cancers requires appropriate countermeasures to overcome cancer-induced immune suppression. We previously showed that standard-of-care carboplatin/paclitaxel chemotherapy can reduce abnormally high numbers of immunosuppressive myeloid cells in patients, allowing the development of much stronger therapeutic HPV16 vaccine (ISA101)-induced tumor immunity. We now show the clinical effects of ISA101 vaccination during chemotherapy in 77 patients with advanced, recurrent, or metastatic cervical cancer in a dose assessment study of ISA101. Tumor regressions were observed in 43% of 72 evaluable patients. The depletion of myeloid suppressive cells by carboplatin/paclitaxel was associated with detection of low frequency of spontaneous HPV16-specific immunity in 21 of 62 tested patients. Patients mounted type 1 T cell responses to the vaccine across all doses. The group of patients with higher than median vaccine-induced immune responses lived longer, with a flat tail on the survival curve. This demonstrates that chemoimmunotherapy can be exploited to the benefit of patients with advanced cancer based on a defined mode of action.

MHC Class I Deficiency in Solid Tumors and Therapeutic Strategies to Overcome It

It is now well accepted that the immune system can control cancer growth. However, tumors escape immune-mediated control through multiple mechanisms and the downregulation or loss of major histocompatibility class (MHC)-I molecules is a common immune escape mechanism in many cancers. MHC-I molecules present antigenic peptides to cytotoxic T cells, and MHC-I loss can render tumor cells invisible to the immune system. In this review, we examine the dysregulation of MHC-I expression in cancer, explore the nature of MHC-I-bound antigenic peptides recognized by immune cells, and discuss therapeutic strategies that can be used to overcome MHC-I deficiency in solid tumors, with a focus on the role of natural killer (NK) cells and CD4 T cells.

Blockade of immune checkpoints in lymph nodes through locoregional delivery augments cancer immunotherapy

Systemic administration of immune checkpoint blockade (ICB) monoclonal antibodies (mAbs) can unleash antitumor functions of T cells but is associated with variable response rates and off-target toxicities. We hypothesized that antitumor efficacy of ICB is limited by the minimal accumulation of mAb within tissues where antitumor immunity is elicited and regulated, which include the tumor microenvironment (TME) and secondary lymphoid tissues. In contrast to systemic administration, intratumoral and intradermal routes of administration resulted in higher mAb accumulation within both the TME and its draining lymph nodes (LNs) or LNs alone, respectively. The use of either locoregional administration route resulted in pronounced T cell responses from the ICB therapy, which developed in the secondary lymphoid tissues and TME of treated mice. Targeted delivery of mAb to tumor-draining lymph nodes (TdLNs) alone was associated with enhanced antitumor immunity and improved therapeutic effects compared to conventional systemic ICB therapy, and these effects were sustained at reduced mAb doses and comparable to those achieved by intratumoral administration. These data suggest that locoregional routes of administration of ICB mAb can augment ICB therapy by improving immunomodulation within TdLNs.

Inflammatory markers in autoimmunity induced by checkpoint inhibitors

PURPOSE

Immune checkpoint inhibitors (ICI) are highly effective in several cancer entities, but also invoke a variety of immune-related adverse events (irAE). These are mostly reversible, but can be life-threatening or even fatal. Currently, the pathogenesis is not fully understood, but crucial for effective treatment. Prediction and early detection of irAE could be facilitated and treatment optimized if relevant biomarkers and effector mechanisms were better characterized.

METHODS

This study included a total of 45 irAE in patients with metastatic melanoma who were treated with ICI. All patients underwent a complete work-up with exclusion of other causes. Longitudinal blood samples were analyzed for a panel of soluble markers and compared to baseline and to patients who did not experience any irAE. Measurements included LDH, interleukin (IL)-6, IL-1β, IL-17, C-reactive protein (CRP) and tumor necrosis factor (TNF)-alpha as well as tumor markers S100 and melanoma inhibitory activity (MIA).

RESULTS

During the early onset of irAE increases in serum IL-6 (from mean 24.4 pg/ml at baseline to 51.0 pg/ml; p = 0.003) and CRP (from mean 7.0 mg/l at baseline to 17.7 mg/l; p = 0.001) and a decrease in MIA (from mean 5.4 pg/ml at baseline to 4.8 pg/ml; p = 0.035) were detected. No changes in IL-17 were noted. These effects were observed for irAE of different organ systems.

CONCLUSION

Increases of a combination of IL-6 and CRP serum levels can be used for the early detection of irAE and tailored management. Interestingly, changes in MIA serum levels also correlate with irAE onset.

Systemic immunity in cancer

Immunotherapy has revolutionized cancer treatment, but efficacy remains limited in most clinical settings. Cancer is a systemic disease that induces many functional and compositional changes to the immune system as a whole. Immunity is regulated by interactions of diverse cell lineages across tissues. Therefore, an improved understanding of tumour immunology must assess the systemic immune landscape beyond the tumour microenvironment (TME). Importantly, the peripheral immune system is required to drive effective natural and therapeutically induced antitumour immune responses. In fact, emerging evidence suggests that immunotherapy drives new immune responses rather than the reinvigoration of pre-existing immune responses. However, new immune responses in individuals burdened with tumours are compromised even beyond the TME. Herein, we aim to comprehensively outline the current knowledge of systemic immunity in cancer.

TriMix and tumor antigen mRNA electroporated dendritic cell vaccination plus ipilimumab: link between T-cell activation and clinical responses in advanced melanoma

Background

We previously reported that dendritic cell-based mRNA vaccination plus ipilimumab (TriMixDC-MEL IPI) results in an encouraging rate of tumor responses in patients with pretreated advanced melanoma. Here, we report the TriMixDC-MEL IPI-induced T-cell responses detected in the peripheral blood.

Methods

Monocyte-derived dendritic cells electroporated with mRNA encoding CD70, CD40 ligand, and constitutively active TLR4 (TriMix) as well as the tumor-associated antigens tyrosinase, gp100, MAGE-A3, or MAGE-C2 were administered together with IPI for four cycles. For 18/39 patients, an additional vaccine was administered before the first IPI administration. We evaluated tumor-associated antigen specific T-cell responses in previously collected peripheral blood mononuclear cells, available from 15 patients.

Results

Vaccine-induced enzyme-linked immunospot assay responses detected after in vitro T-cell stimulation were shown in 12/15 patients. Immune responses detected in patients with a complete or partial response were significantly stronger and broader, and exhibited a higher degree of multifunctionality compared with responses in patients with stable or progressive disease. CD8+ T-cell responses from patients with an ongoing clinical response, either elicited by TriMixDC-MEL IPI or on subsequent pembrolizumab treatment, exhibited the highest degree of multifunctionality.

Conclusions

TriMixDC-MEL IPI treatment results in robust CD8+ T-cell responses in a meaningful portion of stage III or IV melanoma patients, and obviously in patients with a clinical response. The levels of polyfunctional and multiantigen T-cell responses measured in patients with a complete response, particularly in patients evidently cured after 5+ years of follow-up, may provide a benchmark for the level of immune stimulation needed to achieve a durable clinical remission.

Trial registration number

NCT01302496.

Identification and characterization of a SARS-CoV-2 specific CD8+ T cell response with immunodominant features

The COVID-19 pandemic caused by SARS-CoV-2 is a continuous challenge worldwide, and there is an urgent need to map the landscape of immunogenic and immunodominant epitopes recognized by CD8⁺ T cells. Here, we analyze samples from 31 patients with COVID-19 for CD8⁺ T cell recognition of 500 peptide-HLA class I complexes, restricted by 10 common HLA alleles. We identify 18 CD8⁺ T cell recognized SARS-CoV-2 epitopes, including an epitope with immunodominant features derived from ORF1ab and restricted by HLA-A*01:01. In-depth characterization of SARS-CoV-2-specific CD8⁺ T cell responses of patients with acute critical and severe disease reveals high expression of NKG2A, lack of cytokine production and a gene expression profile inhibiting T cell re-activation and migration while sustaining survival. SARS-CoV-2-specific CD8⁺ T cell responses are detectable up to 5 months after recovery from critical and severe disease, and these responses convert from dysfunctional effector to functional memory CD8⁺ T cells during convalescence.

T-Cell Therapy for Lymphoma Using Nonengineered Multiantigen-Targeted T Cells Is Safe and Produces Durable Clinical Effects

PURPOSE

Patients with relapsed lymphomas often fail salvage therapies including high-dose chemotherapy and mono-antigen-specific T-cell therapies, highlighting the need for nontoxic, novel treatments. To that end, we clinically tested an autologous T-cell product that targets multiple tumor-associated antigens (TAAs) expressed by lymphomas with the intent of treating disease and preventing immune escape.

PATIENTS AND METHODS

We expanded polyclonal T cells reactive to five TAAs: PRAME, SSX2, MAGEA4, SURVIVIN, and NY-ESO-1. Products were administered to 32 patients with Hodgkin lymphomas (n = 14) or non-Hodgkin lymphomas (n = 18) in a two-part phase I clinical trial, where the objective of the first phase was to establish the safety of targeting all five TAAs (fixed dose, 0.5 × 10⁷ cells/m²) simultaneously and the second stage was to establish the maximum tolerated dose. Patients had received a median of three prior lines of therapy and either were at high risk for relapse (adjuvant arm, n = 17) or had chemorefractory disease (n = 15) at enrollment.

RESULTS

Infusions were safe with no dose-limiting toxicities observed in either the antigen- or dose-escalation phases. Although the maximum tolerated dose was not reached, the maximum tested dose at which efficacy was observed (two infusions, 2 × 10⁷ cells/m²) was determined as the recommended phase II dose. Of the patients with chemorefractory lymphomas, two (of seven) with Hodgkin lymphomas and four (of eight) with non-Hodgkin lymphomas achieved durable complete remissions (> 3 years).

CONCLUSION

T cells targeting five TAAs and administered at doses of up to two infusions of 2 × 10⁷ cells/m² are well-tolerated by patients with lymphoma both as adjuvant and to treat chemorefractory lymphoma. Preliminary indicators of antilymphoma activity were seen in the chemorefractory cohort across both antigen- and dose-escalation phases.

Coadministration of a Clinically Relevant Dexamethasone Dosage With Ablative Radiation Therapy Reduces Peripheral Lymphocytes But Does Not Alter In Vivo Intratumoral Lymphocyte Phenotype or Inhibit Efficacy of Radiation Therapy in a Murine Colorectal Tumor Model

PURPOSE

Dexamethasone is commonly given during radiation therapy (RT) to manage toxicities. Our study examines if dexamethasone coadministration with RT inhibits the RT-induced antitumor T cell response in mouse.

METHODS AND MATERIALS

Intramuscularly implanted MC38 tumors were irradiated with 15 Gy after establishing for 7 days. Tumor bearing mice were administered dexamethasone using multiple schedules and doses. Peripheral lymphocyte reduction was monitored by complete blood count and intratumoral and tumor draining lymph node (tdLN) populations by flow cytometry. Effector phenotype and function of ex vivo stimulated tumor-infiltrating lymphocytes (TILs) and naïve splenocytes as well as in vivo TILs with or without dexamethasone were monitored by flow cytometry and ELISA.

RESULTS

Long course high dose, short course high dose, and short course human equivalent dose dexamethasone reduced peripheral lymphocytes yet did not inhibit survival after irradiation. Short course high dose administration decreased TIL and tdLN lymphocyte activation as well as tdLN mass but did not affect TIL frequencies or change tdLN cell population composition. Dexamethasone inhibited effector function of ex vivo stimulated naïve splenocytes and TILs, but magnitude of IFN-γ secretion was consistently higher in TILs regardless of dexamethasone dose. In vivo analysis of TILs after irradiation and HE dexamethasone treatment showed that TILs had a similar effector phenotype compared with vehicle controls.

CONCLUSIONS

Dexamethasone reduces blood and tdLN lymphocytes. Dexamethasone also suppresses TIL activation/effector function yet does not affect survival in irradiated MC38 tumor bearing mice, which depend on RT-induced immune responses for therapy efficacy. Additional study in human subjects is warranted.

New systemic therapies for cutaneous melanoma: why, who and what

Incidence of melanoma has been increasing in both sexes in the last decades. Advanced melanoma has always been one of the deadliest cancers worldwide due to his high metastatic capacity. In the last ten years, progresses in the knowledge of the molecular mechanisms involved in the melanoma development and progression, and in immune-response against melanoma, empowered the development of two new classes of systemic therapeutic agents: target-therapies and immunotherapies. Both classes consist of monoclonal antibodies inhibiting specific molecules. Target-therapies are selectively directed against cells harboring the BRAFV600-mutation, while immunotherapies target the two molecules involved in immune-checkpoint regulation, enhancing the immune response against the tumor: cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed cell death-1 receptor (PD-1). Target- and immunotherapy demonstrated to improve both progression-free and overall survival in melanoma patients either in metastatic or in adjuvant settings. Several drugs have been approved in recent years as monotherapy or in combination, and many other drugs are currently under investigation in clinical trials. In the current review on new systemic therapies for cutaneous melanoma, we revised the molecular basis and the mechanisms of actions of both target- and immunotherapy (why). We discussed who are the best candidate to receive such therapies in both the adjuvant and metastatic setting (who) and which were the most important efficacy and safety data on these drugs (what).

The Dynamic Entropy of Tumor Immune Infiltrates: The Impact of Recirculation, Antigen-Specific Interactions, and Retention on T Cells in Tumors

Analysis of tumor infiltration using conventional methods reveals a snapshot view of lymphocyte interactions with the tumor environment. However, lymphocytes have the unique capacity for continued recirculation, exploring varied tissues for the presence of cognate antigens according to inflammatory triggers and chemokine gradients. We discuss the role of the inflammatory and cellular makeup of the tumor environment, as well as antigen expressed by cancer cells or cross-presented by stromal antigen presenting cells, on recirculation kinetics of T cells. We aim to discuss how current cancer therapies may manipulate lymphocyte recirculation versus retention to impact lymphocyte exclusion in the tumor.

Immunotherapy for pancreatic cancer: chasing the light at the end of the tunnel

BACKGROUND

Checkpoint blockade immunotherapy has had a significant impact on the survival of a subset of patients with advanced cancers. It has been particularly effective in immunogenic cancer types that present large numbers of somatic mutations in their genomes. To date, all conventional immunotherapies have failed to produce significant clinical benefits for patients diagnosed with pancreatic cancer, probably due to its poor immunogenic properties, including low numbers of neoantigens and highly immune-suppressive microenvironments.

CONCLUSIONS

Herein, we discuss advances that have recently been made in cancer immunotherapy and the potential of this field to deliver effective treatment options for pancreatic cancer patients. Preclinical investigations, combining different types of therapies, highlight possibilities to enhance anti-tumor immunity and to generate meaningful clinical responses in pancreatic cancer patients. Results from completed and ongoing (pre)clinical trials are discussed.

Emerging Trends for Radio-Immunotherapy in Rectal Cancer

Rectal cancer is a heterogeneous disease at the genetic and molecular levels, both aspects having major repercussions on the tumor immune contexture. Whilst microsatellite status and tumor mutational load have been associated with response to immunotherapy, presence of tumor-infiltrating lymphocytes is one of the most powerful prognostic and predictive biomarkers. Yet, the majority of rectal cancers are characterized by microsatellite stability, low tumor mutational burden and poor T cell infiltration. Consequently, these tumors do not respond to immunotherapy and treatment largely relies on radiotherapy alone or in combination with chemotherapy followed by radical surgery. Importantly, pre-clinical and clinical studies suggest that radiotherapy can induce a complete reprograming of the tumor microenvironment, potentially sensitizing it for immune checkpoint inhibition. Nonetheless, growing evidence suggest that this synergistic effect strongly depends on radiotherapy dosing, fractionation and timing. Despite ongoing work, information about the radiotherapy regimen required to yield optimal clinical outcome when combined to checkpoint blockade remains largely unavailable. In this review, we describe the molecular and immune heterogeneity of rectal cancer and outline its prognostic value. In addition, we discuss the effect of radiotherapy on the tumor microenvironment, focusing on the mechanisms and benefits of its combination with immune checkpoint inhibitors.

Cancer Immunotherapy Update: FDA-Approved Checkpoint Inhibitors and Companion Diagnostics

Immune checkpoint inhibitors (ICIs) are considered a new standard-of-care across many cancer indications. This review provides an update on ICIs approved by the Food and Drug Administration (FDA), with focus on monoclonal antibodies that target the programmed cell death 1 (PD-1) or its ligand, PD-1 ligand 1 (PD-L1), including information on their clinical indications and associated companion diagnostics. The information is further discussed with strategies for identifying predictive biomarkers to guide the clinical use of PD-1/PD-L1-targeted therapies.

PD-L1 and B7-1 Cis-Interaction: New Mechanisms in Immune Checkpoints and Immunotherapies

Immune checkpoints negatively regulate immune cell responses. Programmed cell death protein 1:programmed death ligand 1 (PD-1:PD-L1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4):B7-1 are among the most important immune checkpoint pathways, and are key targets for immunotherapies that seek to modulate the balance between stimulatory and inhibitory signals to lead to favorable therapeutic outcomes. The current dogma of these two immune checkpoint pathways has regarded them as independent with no interactions. However, the newly characterized PD-L1:B7-1 ligand-ligand cis-interaction and its ability to bind CTLA-4 and CD28, but not PD-1, suggests that these pathways have significant crosstalk. Here, we propose that the PD-L1:B7-1 cis-interaction brings novel mechanistic understanding of these pathways, new insights into mechanisms of current immunotherapies, and fresh ideas to develop better treatments in a variety of therapeutic settings.

Emerging dynamics pathways of response and resistance to PD-1 and CTLA-4 blockade: tackling uncertainty by confronting complexity

Immune checkpoint inhibitors provide considerable therapeutic benefit in a range of solid cancers as well as in a subgroup of hematological malignancies. Response rates are however suboptimal, and despite considerable efforts, predicting response to immune checkpoint inhibitors ahead of their administration in a given patient remains elusive. The study of the dynamics of the immune system and of the tumor under immune checkpoint blockade brought insight into the mechanisms of action of these therapeutic agents. Equally relevant are the mechanisms of adaptive resistance to immune checkpoint inhibitors that have been uncovered through this approach. In this review, we discuss the dynamics of the immune system and of the tumor under immune checkpoint blockade emanating from recent studies on animal models and humans. We will focus on mechanisms of action and of resistance conveying information predictive of therapeutic response.

Dog leukocyte antigen-88*034:01 presents nonamer peptides from canine distemper virus hemagglutinin, large polymerase, and matrix proteins

Canine spontaneous cancers may offer greater fidelity than rodent models in advancing clinical immunotherapies. Boxers in particular are distinguished as study subjects by their popularity, and high incidence of human-relevant cancers. Further, the MHC class I allele DLA-88*034:01, with a known motif, dominates the breed, facilitating discovery of shared CTL responses against mutation-origin neoepitopes by standard prediction methods. We experimentally confirmed the allomorph's binding motif by developing an MHC surface stabilization assay. The assay validated four DLA-88*034:01-presented peptides from canine distemper virus, ubiquitously administered in routine vaccines, for positive controls in future CTL studies. In turn, these viral peptides substantiated motif-based prediction for DLA-88*034:01. The study adds new tools for studying neoepitope-specific CTL in Boxers to foster canine comparative oncology.

Prognostic and predictive role of the tumor immune landscape

Cancer immunotherapy utilizing immune checkpoint inhibitors, has become mainstay for a growing number of cancer types. However, in general, the objective response rate and survival is only improved in a minority of cancer patients. Many of the biomarkers to select patients that either benefit or do not, have next to being predictive also prognostic value, are continuous instead of categorical, and are therefore difficult to use in daily practice. Currently, PD-L1 by immunohistochemical staining is the only approved biomarker to select metastatic non-small cell lung cancer patients for single agent pembrolizumab treatment. This may be extended with PD-L1 IHC staining in other cancer types, with different assays and different cut-offs. Other biomarkers, such as tumor mutational burden (TMB) by either whole exome sequencing or by targeted panel sequencing, gene expression profiling (GEP) either by NanoString or another RNA based sequencing test are under development. Assessment of immune infiltrates by multiplex immunohistochemistry or immunofluorescence also requires further validation. In the end, some of these tests may need to be combined in order to have the highest positive and negative predictive value and qualify as a reliable test for patient selection. The complexity and current status of biomarker research in immuno-oncology is outlined in this review.

Activity and Immune Correlates of Programmed Death-1 Blockade Therapy in Patients With Advanced Large Cell Neuroendocrine Carcinoma

BACKGROUND

The efficacy of anti-programmed death receptor 1 (PD-1) therapy in patients with large cell neuroendocrine carcinoma (LCNEC) remains unclear. We investigated the outcome of anti-PD-1 therapy and its predictive markers by evaluating the immune-related tumor microenvironment.

PATIENTS

We retrospectively reviewed patients with advanced LCNEC treated with systemic chemotherapy. We also evaluated PD ligand 1 (PD-L1) expression (clone: 22C3), CD8-positive tumor-infiltrating lymphocytes (TILs), and the mutational profiles.

RESULTS

Seventy patients were enrolled, and 13 of 70 patients received anti-PD-1 therapy. The progression-free survival (PFS) and objective response rate (ORR) of the anti-PD-1 therapy were 4.2 months and 39%, respectively. The overall survival of patients treated with anti-PD-1 therapy (n = 13) was significantly better than those treated without anti-PD-1 therapy (n = 57) (25.2 months vs 10.9 months; P = .02). Among the 13 patients treated with anti-PD-1 therapy, 10 patients (90%) had PD-L1-negative tumors. Patients with a high density of tumoral CD8-positive TILs (≥38/mm²) had a significantly better ORR and PFS than those with a low density of tumoral CD8-positive TILs (ORR: P = .02; PFS: P = .003). Additionally, all 3 patients with TP53 mutation co-occurring with PIK3CA mutation (2 of 8 patients) or RB1 mutation (1 of 8 patients) responded to anti-PD-1 therapy.

CONCLUSIONS

Anti-PD-1 therapy was effective regardless of PD-L1 positivity in patients with advanced LCNEC. Our investigation might suggest that the density of tumoral CD8-positive TILs and the presence of co-occurring mutations are predictors of the efficacy of anti-PD-1 therapy in patients with advanced LCNEC.

Functional Heterogeneity and Therapeutic Targeting of Tissue-Resident Memory T Cells

Tissue-resident memory T (T_RM) cells mediate potent local innate and adaptive immune responses and provide long-lasting protective immunity. T_RM cells localize to many different tissues, including barrier tissues, and play a crucial role in protection against infectious and malignant disease. The formation and maintenance of T_RM cells are influenced by numerous factors, including inflammation, antigen triggering, and tissue-specific cues. Emerging evidence suggests that these signals also contribute to heterogeneity within the T_RM cell compartment. Here, we review the phenotypic and functional heterogeneity of CD8⁺ T_RM cells at different tissue sites and the molecular determinants defining CD8⁺ T_RM cell subsets. We further discuss the possibilities of targeting the unique cell surface molecules, cytokine and chemokine receptors, transcription factors, and metabolic features of T_RM cells for therapeutic purposes. Their crucial role in immune protection and their location at the frontlines of the immune defense make T_RM cells attractive therapeutic targets. A better understanding of the possibilities to selectively modulate T_RM cell populations may thus improve vaccination and immunotherapeutic strategies employing these potent immune cells.

Loss of type I IFN responsiveness impairs natural killer cell antitumor activity in breast cancer

Competent type I IFN signaling is the lynchpin of most immune surveillance mechanisms and has recently proven critical to the efficacy of several anticancer agents. Expression of the type I IFN receptor, IFNAR, underpins type I IFN responsiveness in all cells and facilitates the activation and cytotoxic potential of lymphocytes, while loss of IFNAR on lymphocytes has previously been associated with tumor progression and poor patient survival. This study underscores the importance of intact type I IFN signaling to NK cells in the regulation of tumorigenesis and metastasis, whereby ablation of NK cell IFNAR1 impairs antitumor activity and tumor clearance. Using a preclinical model of triple negative breast cancer, we identified that intact IFNAR on NK cells is required for an effective response to type I IFN-inducing immunotherapeutics that may be mediated by pathways associated with NK cell degranulation. Taken together, these data provide a rationale for considering the IFNAR status on NK cells when devising therapeutic strategies aimed at inducing systemic type I IFN signaling in breast cancer.

Design and Efficacy of a Monovalent Bispecific PD-1/CTLA4 Antibody That Enhances CTLA4 Blockade on PD-1+ Activated T Cells

The clinical benefit of PD-1 blockade can be improved by combination with CTLA4 inhibition but is commensurate with significant immune-related adverse events suboptimally limiting the doses of anti-CTLA4 mAb that can be used. MEDI5752 is a monovalent bispecific antibody designed to suppress the PD-1 pathway and provide modulated CTLA4 inhibition favoring enhanced blockade on PD-1⁺ activated T cells. We show that MEDI5752 preferentially saturates CTLA4 on PD-1⁺ T cells versus PD-1^- T cells, reducing the dose required to elicit IL2 secretion. Unlike conventional PD-1/CTLA4 mAbs, MEDI5752 leads to the rapid internalization and degradation of PD-1. Moreover, we show that MEDI5752 preferentially localizes and accumulates in tumors providing enhanced activity when compared with a combination of mAbs targeting PD-1 and CTLA4 in vivo. Following treatment with MEDI5752, robust partial responses were observed in two patients with advanced solid tumors. MEDI5752 represents a novel immunotherapy engineered to preferentially inhibit CTLA4 on PD-1⁺ T cells. SIGNIFICANCE: The unique characteristics of MEDI5752 represent a novel immunotherapy engineered to direct CTLA4 inhibition to PD-1⁺ T cells with the potential for differentiated activity when compared with current conventional mAb combination strategies targeting PD-1 and CTLA4. This molecule therefore represents a step forward in the rational design of cancer immunotherapy.See related commentary by Burton and Tawbi, p. 1008.This article is highlighted in the In This Issue feature, p. 995.

The Role of Antigen Processing and Presentation in Cancer and the Efficacy of Immune Checkpoint Inhibitor Immunotherapy

Recent clinical successes of cancer immunotherapy using immune checkpoint inhibitors (ICIs) are rapidly changing the landscape of cancer treatment. Regardless of initial impressive clinical results though, the therapeutic benefit of ICIs appears to be limited to a subset of patients and tumor types. Recent analyses have revealed that the potency of ICI therapies depends on the efficient presentation of tumor-specific antigens by cancer cells and professional antigen presenting cells. Here, we review current knowledge on the role of antigen presentation in cancer. We focus on intracellular antigen processing and presentation by Major Histocompatibility class I (MHCI) molecules and how it can affect cancer immune evasion. Finally, we discuss the pharmacological tractability of manipulating intracellular antigen processing as a complementary approach to enhance tumor immunogenicity and the effectiveness of ICI immunotherapy.

The biomarkers related to immune related adverse events caused by immune checkpoint inhibitors

The enthusiasm for immune checkpoint inhibitors (ICIs), an efficient tumor treatment model different from traditional treatment, is based on their unprecedented antitumor effect, but the occurrence of immune-related adverse events (irAEs) is an obstacle to the prospect of ICI treatment. IrAEs are a discrete toxicity caused by the nonspecific activation of the immune system and can affect almost all tissues and organs. Currently, research on biomarkers mainly focuses on the gastrointestinal tract, endocrine system, skin and lung. Several potential hypotheses concentrate on the overactivation of the immune system, excessive release of inflammatory cytokines, elevated levels of pre-existing autoantibodies, and presence of common antigens between tumors and normal tissues. This review lists the current biomarkers that might predict irAEs and their possible mechanisms for both nonspecific and organ-specific biomarkers. However, the prediction of irAEs remains a major clinical challenge to screen and identify patients who are susceptible to irAEs and likely to benefit from ICIs.

Stem-like CD8 T cells mediate response of adoptive cell immunotherapy against human cancer

Adoptive T cell therapy (ACT) using ex vivo-expanded autologous tumor-infiltrating lymphocytes (TILs) can mediate complete regression of certain human cancers. The impact of TIL phenotypes on clinical success of TIL-ACT is currently unclear. Using high-dimensional analysis of human ACT products, we identified a memory-progenitor CD39-negative stem-like phenotype (CD39-CD69-) associated with complete cancer regression and TIL persistence and a terminally differentiated CD39-positive state (CD39+CD69+) associated with poor TIL persistence. Most antitumor neoantigen-reactive TILs were found in the differentiated CD39+ state. However, ACT responders retained a pool of CD39- stem-like neoantigen-specific TILs that was lacking in ACT nonresponders. Tumor-reactive stem-like TILs were capable of self-renewal, expansion, persistence, and superior antitumor response in vivo. These data suggest that TIL subsets mediating ACT response are distinct from TIL subsets enriched for antitumor reactivity.

Adenoviral vaccines promote protective tissue-resident memory T cell populations against cancer

BACKGROUND

Adenoviral vectors emerged as important platforms for cancer immunotherapy. Vaccination with adenoviral vectors is promising in this respect, however, their specific mechanisms of action are not fully understood. Here, we assessed the development and maintenance of vaccine-induced tumor-specific CD8+ T cells elicited upon immunization with adenoviral vectors.

METHODS

Adenoviral vaccine vectors encoding the full-length E7 protein from human papilloma virus (HPV) or the immunodominant epitope from E7 were generated, and mice were immunized intravenously with different quantities (107, 108 or 109 infectious units). The magnitude, kinetics and tumor protection capacity of the induced vaccine-specific T cell responses were evaluated.

RESULTS

The adenoviral vaccines elicited inflationary E7-specific memory CD8+ T cell responses in a dose-dependent manner. The magnitude of these vaccine-specific CD8+ T cells in the circulation related to the development of E7-specific CD8+ tissue-resident memory T (TRM) cells, which were maintained for months in multiple tissues after vaccination. The vaccine-specific CD8+ T cell responses conferred long-term protection against HPV-induced carcinomas in the skin and liver, and this protection required the induction and accumulation of CD8+ TRM cells. Moreover, the formation of CD8+ TRM cells could be enhanced by temporal targeting CD80/CD86 costimulatory interactions via CTLA-4 blockade early after immunization.

CONCLUSIONS

Together, these data show that adenoviral vector-induced CD8+ T cell inflation promotes protective TRM cell populations, and this can be enhanced by targeting CTLA-4.

Overcoming Immune Evasion in Melanoma

Melanoma is the most aggressive and dangerous form of skin cancer that develops from transformed melanocytes. It is crucial to identify melanoma at its early stages, in situ, as it is "curable" at this stage. However, after metastasis, it is difficult to treat and the five-year survival is only 25%. In recent years, a better understanding of the etiology of melanoma and its progression has made it possible for the development of targeted therapeutics, such as vemurafenib and immunotherapies, to treat advanced melanomas. In this review, we focus on the molecular mechanisms that mediate melanoma development and progression, with a special focus on the immune evasion strategies utilized by melanomas, to evade host immune surveillances. The proposed mechanism of action and the roles of immunotherapeutic agents, ipilimumab, nivolumab, pembrolizumab, and atezolizumab, adoptive T- cell therapy plus T-VEC in the treatment of advanced melanoma are discussed. In this review, we implore that a better understanding of the steps that mediate melanoma onset and progression, immune evasion strategies exploited by these tumor cells, and the identification of biomarkers to predict treatment response are critical in the design of improved strategies to improve clinical outcomes for patients with this deadly disease.

PD-1 and TIGIT coexpression identifies a circulating CD8 T cell subset predictive of response to anti-PD-1 therapy

BACKGROUND

Clinical benefit from programmed cell death 1 receptor (PD-1) inhibitors relies on reinvigoration of endogenous antitumor immunity. Nonetheless, robust immunological markers, based on circulating immune cell subsets associated with therapeutic efficacy are yet to be validated.

METHODS

We isolated peripheral blood mononuclear cell from three independent cohorts of melanoma and Merkel cell carcinoma patients treated with PD-1 inhibitor, at baseline and longitudinally after therapy. Using multiparameter flow cytometry and cell sorting, we isolated four subsets of CD8+ T cells, based on PD-1 and TIGIT expression profiles. We performed phenotypic characterization, T cell receptor sequencing, targeted transcriptomic analysis and antitumor reactivity assays to thoroughly characterize each of these subsets.

RESULTS

We documented that the frequency of circulating PD-1+TIGIT+ (DPOS) CD8+ T-cells after 1 month of anti-PD-1 therapy was associated with clinical response and overall survival. This DPOS T-cell population was enriched in highly activated T-cells, tumor-specific and emerging T-cell clonotypes and T lymphocytes overexpressing CXCR5, a key marker of the CD8 cytotoxic follicular T cell population. Additionally, transcriptomic profiling defined a specific gene signature for this population as well as the overexpression of specific pathways associated with the therapeutic response.

CONCLUSIONS

Our results provide a convincing rationale for monitoring this PD-1+TIGIT+ circulating population as an early cellular-based marker of therapeutic response to anti-PD-1 therapy.

Uncoupling Therapeutic Efficacy from Immune-Related Adverse Events in Immune Checkpoint Blockade

Immunotherapy with monoclonal antibodies targeting immune checkpoint molecules, including programmed death-1 (PD-1), PD ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen (CTLA)-4, has become prominent in the treatment of many types of cancer. However, a significant number of patients treated with immune checkpoint inhibitors (ICIs) develop immune-related adverse events (irAEs). irAEs can affect any organ system, and although most are clinically manageable, irAEs can result in mortality or long-term morbidity. Factors that can predict irAEs remain elusive. Understanding the etiology of ICI-induced irAEs and ways to limit these adverse events are needed. In this review, we provide basic science and clinical insights on the mechanisms responsible for ICI efficacy and ICI-induced irAEs. We further provide insights into approaches that may uncouple irAEs from the ability of ICIs to kill tumor cells.

Characteristics of TCR Repertoire Associated With Successful Immune Checkpoint Therapy Responses

Immunotherapies have revolutionized cancer treatment. In particular, immune checkpoint therapy (ICT) leads to durable responses in some patients with some cancers. However, the majority of treated patients do not respond. Understanding immune mechanisms that underlie responsiveness to ICT will help identify predictive biomarkers of response and develop treatments to convert non-responding patients to responding ones. ICT primarily acts at the level of adaptive immunity. The specificity of adaptive immune cells, such as T and B cells, is determined by antigen-specific receptors. T cell repertoires can be comprehensively profiled by high-throughput sequencing at the bulk and single-cell level. T cell receptor (TCR) sequencing allows for sensitive tracking of dynamic changes in antigen-specific T cells at the clonal level, giving unprecedented insight into the mechanisms by which ICT alters T cell responses. Here, we review how the repertoire influences response to ICT and conversely how ICT affects repertoire diversity. We will also explore how changes to the repertoire in different anatomical locations can better correlate and perhaps predict treatment outcome. We discuss the advantages and limitations of current metrics used to characterize and represent TCR repertoire diversity. Discovery of predictive biomarkers could lie in novel analysis approaches, such as network analysis of amino acids similarities between TCR sequences. Single-cell sequencing is a breakthrough technology that can link phenotype with specificity, identifying T cell clones that are crucial for successful ICT. The field of immuno-sequencing is rapidly developing and cross-disciplinary efforts are required to maximize the analysis, application, and validation of sequencing data. Unravelling the dynamic behavior of the TCR repertoire during ICT will be highly valuable for tracking and understanding anti-tumor immunity, biomarker discovery, and ultimately for the development of novel strategies to improve patient outcomes.

Impact of chemoradiotherapy on the immune-related tumour microenvironment and efficacy of anti-PD-(L)1 therapy for recurrences after chemoradiotherapy in patients with unresectable locally advanced non-small cell lung cancer

BACKGROUND

A history of radiotherapy and chemoradiotherapy (CRT) reportedly increases the efficacy of the PD-1 blockade in patients with advanced non-small cell lung cancer (NSCLC). We investigated the efficacy of anti-PD-(L)1 therapy after CRT failure and how CRT changes the status of PD-L1 expression on tumours and on tumour-infiltrated lymphocytes (TILs).

METHODS

We retrospectively reviewed patients with unresectable locally advanced NSCLC (LA-NSCLC) who were treated with CRT between 2007 and 2018 and evaluated the efficacy of the PD-(L)1 blockade after CRT failure. We also compared the PD-L1 (clone: 22C3) expression levels and the tumoral and stromal distributions of CD8-positive TILs using paired formalin-fixed, paraffin-embedded specimens obtained before and after CRT.

RESULTS

We identified 422 patients and 65 patients who had relapsed after CRT received anti-PD-(L)1 therapy. The objective response rate (ORR) and the progression-free survival (PFS) after anti-PD-(L)1 therapy were 48% and 8.7 months (95% CI, 4.5-13), respectively. The RR and PFS did not differ according to the pre-CRT PD-L1 expression levels. PD-L1 expression changed in 16 of the 18 patients between before and after CRT, but a specific trend was not seen (increased, 9 patients; decreased, 7 patients; no change, 2 patients). In contrast, the density of tumoral CD8-positive TILs increased after CRT treatment (pre-CRT median, 110/mm² versus post-CRT median, 470/mm²; p = 0.025).

CONCLUSIONS

Anti-PD-(L)1 therapy was effective in patients with LA-NSCLC who had progressed after CRT regardless of their pre-CRT PD-L1 expression. The efficacy of anti-PD-(L)1 therapy for patients with NSCLC with CRT failure was superior to that of standard second-line treatment for patients with advanced NSCLC.