Overcoming Genetically Based Resistance Mechanisms to PD-1 Blockade

JAK inhibition enhances checkpoint blockade immunotherapy in patients with Hodgkin lymphoma

Unleashing antitumor T cell activity by checkpoint inhibitor immunotherapy is effective in cancer patients, but clinical responses are limited. Cytokine signaling through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway correlates with checkpoint immunotherapy resistance. We report a phase I clinical trial of the JAK inhibitor ruxolitinib with anti-PD-1 antibody nivolumab in Hodgkin lymphoma patients relapsed or refractory following checkpoint inhibitor immunotherapy. The combination yielded a best overall response rate of 53% (10/19). Ruxolitinib significantly reduced neutrophil-to-lymphocyte ratios and percentages of myeloid suppressor cells but increased numbers of cytokine-producing T cells. Ruxolitinib rescued the function of exhausted T cells and enhanced the efficacy of immune checkpoint blockade in preclinical solid tumor and lymphoma models. This synergy was characterized by a switch from suppressive to immunostimulatory myeloid cells, which enhanced T cell division.

The role of extracellular vesicles in immune cell exhaustion and resistance to immunotherapy

INTRODUCTION

Extracellular vesicles (EVs) are membrane-bound nanoparticles for intercellular communication. Subtypes of EVs, namely exosomes and microvesicles transfer diverse, bioactive cargo to their target cells and eventually interfere with immune responses. Despite being a promising approach, cancer immunotherapy currently faces several challenges including immune resistance. EVs secreted from various sources in the tumor microenvironment provoke immune cell exhaustion and lower the efficacy of immunological treatments, such as CAR T cells and immune checkpoint inhibitors.

AREAS COVERED

This article goes through the mechanisms of action of various types of EVs in inhibiting immune response and immunotherapies, and provides a comprehensive review of EV-based treatments.

EXPERT OPINION

By making use of the distinctive features of EVs, natural or modified EVs are innovatively utilized as novel cancer therapeutics. They are occasionally coupled with currently established treatments to overcome their inadequacies. Investigating the properties and interactions of EVs and EV-based treatments is crucial for determining future steps in cancer therapeutics.

Janus kinase inhibitor overcomes resistance to immune checkpoint inhibitor treatment in peritoneal dissemination of gastric cancer in C57BL/6 J mice

BACKGROUND

Cancer immunotherapy aims to unleash the immune system's potential against cancer cells, providing sustained relief for tumors responsive to immune checkpoint inhibitors (ICIs). While promising in gastric cancer (GC) trials, the efficacy of ICIs diminishes in the context of peritoneal dissemination. Our objective is to identify strategies to enhance the impact of ICI treatment specifically for cases involving peritoneal dissemination in GC.

METHODS

The therapeutic efficacy of anti-PD1, CTLA4 treatment alone, or in combination was assessed using the YTN16 peritoneal dissemination tumor model. Peritoneum and peritoneal exudate cells were collected for subsequent analysis. Immunohistochemical staining, flow cytometry, and bulk RNA-sequence analyses were conducted to evaluate the tumor microenvironment (TME). A Janus kinase inhibitor (JAKi) was introduced based on the pathway analysis results.

RESULTS

Anti-PD1 and anti-CTLA4 combination treatment (dual ICI treatment) demonstrated therapeutic efficacy in certain mice, primarily mediated by CD8 + T cells. However, in mice resistant to dual ICI treatment, even with CD8 + T cell infiltration, most of the T cells exhibited an exhaustion phenotype. Notably, resistant tumors displayed abnormal activation of the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) pathway compared to the untreated group, with observed infiltration of macrophages, neutrophils, and Tregs in the TME. The concurrent administration of JAKi rescued CD8 + T cells function and reshaped the immunosuppressive TME, resulting in enhanced efficacy of the dual ICI treatment.

CONCLUSION

Dual ICI treatment exerts its anti-tumor effects by increasing tumor-specific CD8 + T cell infiltration, and the addition of JAKi further improves ICI resistance by reshaping the immunosuppressive TME.

Immunologic tumor microenvironment modulators for turning cold tumors hot

Tumors can be classified into distinct immunophenotypes based on the presence and arrangement of cytotoxic immune cells within the tumor microenvironment (TME). Hot tumors, characterized by heightened immune activity and responsiveness to immune checkpoint inhibitors (ICIs), stand in stark contrast to cold tumors, which lack immune infiltration and remain resistant to therapy. To overcome immune evasion mechanisms employed by tumor cells, novel immunologic modulators have emerged, particularly ICIs targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1/programmed death-ligand 1(PD-1/PD-L1). These agents disrupt inhibitory signals and reactivate the immune system, transforming cold tumors into hot ones and promoting effective antitumor responses. However, challenges persist, including primary resistance to immunotherapy, autoimmune side effects, and tumor response heterogeneity. Addressing these challenges requires innovative strategies, deeper mechanistic insights, and a combination of immune interventions to enhance the effectiveness of immunotherapies. In the landscape of cancer medicine, where immune cold tumors represent a formidable hurdle, understanding the TME and harnessing its potential to reprogram the immune response is paramount. This review sheds light on current advancements and future directions in the quest for more effective and safer cancer treatment strategies, offering hope for patients with immune-resistant tumors.

Long-lasting mRNA-encoded interleukin-2 restores CD8+ T cell neoantigen immunity in MHC class I-deficient cancers

Major histocompatibility complex (MHC) class I antigen presentation deficiency is a common cancer immune escape mechanism, but the mechanistic implications and potential strategies to address this challenge remain poorly understood. Studying β2-microglobulin (B2M) deficient mouse tumor models, we find that MHC class I loss leads to a substantial immune desertification of the tumor microenvironment (TME) and broad resistance to immune-, chemo-, and radiotherapy. We show that treatment with long-lasting mRNA-encoded interleukin-2 (IL-2) restores an immune cell infiltrated, IFNγ-promoted, highly proinflammatory TME signature, and when combined with a tumor-targeting monoclonal antibody (mAB), can overcome therapeutic resistance. Unexpectedly, the effectiveness of this treatment is driven by IFNγ-releasing CD8+ T cells that recognize neoantigens cross-presented by TME-resident activated macrophages. These macrophages acquire augmented antigen presentation proficiency and other M1-phenotype-associated features under IL-2 treatment. Our findings highlight the importance of restoring neoantigen-specific immune responses in the treatment of cancers with MHC class I deficiencies.

Immune Checkpoint Inhibitors: A Narrative Review on PD-1/PD-L1 Blockade Mechanism, Efficacy, and Safety Profile in Treating Malignancy

Checkpoint inhibitors have been implicated in the treatment of several cancers due to their ability to exploit the immune system's regulatory pathways. This article serves to emphasize the importance of these immunotherapeutic agents and provide further insight into their mechanisms, efficacies, and safety profiles. The main agents in question include programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1). Several literature sources were found to assess the use of these inhibitors in cancers involving the lung, breast, and skin. Several peer-reviewed systematic reviews and the outcomes of clinical trials are combined within this article to support the use and further investigation of these agents in treating neoplasms. Further research into these forms of therapy underscores the revolutionary advancement of oncological interventions, which is important given the rising incidence of neoplasms within populations.

Interleukin-12: Structure, Function, and Its Impact in Colorectal Cancer

Interleukin 12 (IL-12) is a heterodimer consisting of 2 subunits, p35 and p40, with unique associations and interacting functions with its family members. IL-12 is one of the most important cytokines regulating the immune system response and is integral to adaptive immunity. IL-12 has shown marked therapeutic potential in a variety of tumor types. This review therefore summarizes the characteristics of IL-12 and its application in tumor treatment, focusing on its antitumor effects in colorectal cancer (CRC) and potential radiosensitization mechanisms. We aim to provide a current reference for IL-12 and other potential CRC treatment strategies.

Histological sarcomatoid transformation in a lung adenocarcinoma patient following immune checkpoint blockade

Histological transformation is a phenomenon that is well described as one of the causes of tyrosine kinase inhibitor resistance in oncogene-driven non-small-cell lung cancer (NSCLC). The use of immune checkpoint inhibitors (ICIs) as a potential mechanism of acquired resistance to immunotherapy in NSCLC to small-cell lung cancer was also recently found. Here, we report the histological transformation of sarcomatoid carcinoma and metastasis in a lung adenocarcinoma patient without targetable genetic alterations who experienced long-term disease remission after nivolumab therapy. The patient subsequently developed rapid progression in the mediastinal and retroperitoneal lymph nodes, bones, and small intestine. Surgical resection of the small intestine lesion due to acute small intestine bleeding revealed the transformation of NSCLC to sarcomatoid carcinoma. The patient died 3 months after sarcomatoid carcinoma transformation and extensive disease progression, although he was rechallenged with immunotherapy. Genomic and immunohistochemical analyses revealed a comparable abundance of gene mutations and a limited number of immune cells in the tumor microenvironment, with low infiltration of CD8+ T cells, CD4+ T cells, regulatory T cells, and PD-L1+ macrophages in metastatic tumors, revealing a noninflamed immune microenvironment for ICI-resistant tumors.

Melanoma-Modern Treatment for Metastatic Melanoma

ABSTRACT

Traditional chemotherapy has been ineffective in the treatment of metastatic melanoma. Until the use of checkpoint inhibitors, patients had very limited survival. Since the original US Food and Drug Administration approval of ipilimumab over a decade ago, the armamentarium of immunotherapeutic agents has expanded to include programmed cell death protein 1 and lymphocyte activation gene 3 antibodies, requiring a nuanced approach to the selection of frontline treatments, managing patients through recurrence and progression, and determining length of therapy. Herein, we review the existing evidence supporting current standard immunotherapy regimens and discuss the clinical decision-making involved in treating patients with metastatic melanoma with checkpoint inhibitors.

NKG2A Is a Therapeutic Vulnerability in Immunotherapy Resistant MHC-I Heterogeneous Triple-Negative Breast Cancer

Despite the success of immune checkpoint inhibition (ICI) in treating cancer, patients with triple-negative breast cancer (TNBC) often develop resistance to therapy, and the underlying mechanisms are unclear. MHC-I expression is essential for antigen presentation and T-cell-directed immunotherapy responses. This study demonstrates that TNBC patients display intratumor heterogeneity in regional MHC-I expression. In murine models, loss of MHC-I negates antitumor immunity and ICI response, whereas intratumor MHC-I heterogeneity leads to increased infiltration of natural killer (NK) cells in an IFNγ-dependent manner. Using spatial technologies, MHC-I heterogeneity is associated with clinical resistance to anti-programmed death (PD) L1 therapy and increased NK:T-cell ratios in human breast tumors. MHC-I heterogeneous tumors require NKG2A to suppress NK-cell function. Combining anti-NKG2A and anti-PD-L1 therapies restores complete response in heterogeneous MHC-I murine models, dependent on the presence of activated, tumor-infiltrating NK and CD8+ T cells. These results suggest that similar strategies may enhance patient benefit in clinical trials.

SIGNIFICANCE

Clinical resistance to immunotherapy is common in breast cancer, and many patients will likely require combination therapy to maximize immunotherapeutic benefit. This study demonstrates that heterogeneous MHC-I expression drives resistance to anti-PD-L1 therapy and exposes NKG2A on NK cells as a target to overcome resistance. This article is featured in Selected Articles from This Issue, p. 201.

Immune escape of head and neck cancer mediated by the impaired MHC-I antigen presentation pathway

Tumor immune evasion is a hallmark of Head and Neck Cancers. The advent of immune checkpoint inhibitors (ICIs) in the first-line setting has transformed the management of these tumors. Unfortunately, the response rate of Head and Neck Squamous Cell Carcinomas (HNSCC) to ICIs is below 15%, regardless of the human papillomavirus (HPV) status, which might be partially related with impaired antigen presentation machinery (APM). Mechanistically, HNSCC cells are usually defective in the expression of MHC-I associated APM, while this transcriptional pathway is critical for the activation of tumor-killing effector T-cells. To specifically illuminate the phenomenon and seek for therapeutic strategies, this review summarizes the most recently identified role of genetic and functional dysregulation of the MHC-I pathway, specifically through changes at the genetic, epigenetic, post-transcriptional, and post-translational levels, which substantially contributes to HNSCC immune escape and ICI resistance. Several treatment modalities can be potentially exploited to restore APM signaling in tumors, which improves anti-tumor immunity through the activation of interferons, vaccines or rimantadine against HPV and the inhibition of EGFR, SHP-2, PI3K and MEK. Additionally, the combinatorial use of radiotherapy or cytotoxic agents with ICIs can synergize to potentiate APM signaling. Future directions would include further dissection of MHC-I related APM signaling in HNSCC and whether reversing this inhibition in combination with ICIs would elicit a more robust immune response leading to improved response rates in HNSCC. Therapeutic approaches to restore the MHC-I antigen presentation machinery in Head and Neck Cancer. (Red color texts represent the according strategies and the outcomes).

Sequential immunotherapy and targeted therapy for metastatic BRAF V600 mutated melanoma: 4-year survival and biomarkers evaluation from the phase II SECOMBIT trial

No prospective data were available prior to 2021 to inform selection between combination BRAF and MEK inhibition versus dual blockade of programmed cell death protein-1 (PD-1) and cytotoxic T lymphocyte antigen-4 (CTLA-4) as first-line treatment options for BRAFV600-mutant melanoma. SECOMBIT (NCT02631447) was a randomized, three-arm, noncomparative phase II trial in which patients were randomized to one of two sequences with immunotherapy or targeted therapy first, with a third arm in which an 8-week induction course of targeted therapy followed by a planned switch to immunotherapy was the first treatment. BRAF/MEK inhibitors were encorafenib plus binimetinib and checkpoint inhibitors ipilimumab plus nivolumab. Primary outcome of overall survival was previously reported, demonstrating improved survival with immunotherapy administered until progression and followed by BRAF/MEK inhibition. Here we report 4-year survival outcomes, confirming long-term benefit with first-line immunotherapy. We also describe preliminary results of predefined biomarkers analyses that identify a trend toward improved 4-year overall survival and total progression-free survival in patients with loss-of-function mutations affecting JAK or low baseline levels of serum interferon gamma (IFNy). These long-term survival outcomes confirm immunotherapy as the preferred first-line treatment approach for most patients with BRAFV600-mutant metastatic melanoma, and the biomarker analyses are hypothesis-generating for future investigations of predictors of durable benefit with dual checkpoint blockade and targeted therapy.

B2M is a Biomarker Associated With Immune Infiltration In High Altitude Pulmonary Edema

BACKGROUND

High altitude pulmonary edema (HAPE) is a serious mountain sickness with certain mortality. Its early diagnosis is very important. However, the mechanism of its onset and progression is still controversial.

AIM

This study aimed to analyze the HAPE occurrence and development mechanism and search for prospective biomarkers in peripheral blood.

METHODS

The difference genes (DEGs) of the Control group and the HAPE group were enriched by gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and then GSEA analysis was performed. After identifying the immune-related hub genes, QPCR was used to verify and analyze the hub gene function and diagnostic value with single-gene GSEA and ROC curves, and the drugs that acted on the hub gene was found in the CTD database. Immune infiltration and its association with the hub genes were analyzed using CIBERSORT. Finally, WGCNA was employed to investigate immune invasion cells' significantly related gene modules, following enrichment analysis of their GO and KEGG.

RESULTS

The dataset enrichment analysis, immune invasion analysis and WGCNA analysis showed that the occurrence and early progression of HAPE were unrelated to inflammation. The hub genes associated with immunity obtained with MCODE algorithm of Cytoscape were JAK2 and B2M.. RT-qPCR and ROC curves confirmed that the hub gene B2M was a specific biomarker of HAPE and had diagnostic value, and single-gene GSEA analysis confirmed that it participated in MHC I molecule-mediated antigen presentation ability decreased, resulting in reduced immunity.

CONCLUSION

Occurrence and early progression of high altitude pulmonary edema may not be related to inflammation. B2M may be a new clinical potential biomarker for HAPE for early diagnosis and therapeutic evaluation as well as therapeutic targets, and its decrease may be related to reduced immunity due to reduced ability of MCH I to participate in antigen submission.

A novel iTreg-related signature for prognostic prediction in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most common subtype of lung cancer. Most patients are diagnosed at an advanced stage, therefore it is crucial to identify novel prognostic biomarkers for LUAD. As important regulatory cells, inducible regulatory T cells (iTregs) play a vital role in immune suppression and are important for the maintenance of immune homeostasis. This study explored the prognostic value and therapeutic effects of iTreg-related genes in LUAD. Data for LUAD patients, including immune infiltration data, RNA sequencing data, and clinical features, were acquired from The Cancer Genome Atlas, Gene Expression Omnibus, and Tumor Immune Single-cell Hub 2 databases. Immune-related subgroups with different infiltration patterns and iTreg-related genes were identified through univariate and multivariate Cox regression analyses and weighted correlation network analysis. Functional enrichment analyses were performed to explore the underlying mechanisms of iTreg-related genes. A prognostic risk signature was constructed using Cox regression analysis with the least absolute shrinkage and selection operator penalty. The ESTIMATE algorithm was applied to determine the immune status of LUAD patients. We applied the constructed signature to predict chemosensitivity and performed single-cell RNA sequencing analysis. The infiltration of iTregs was identified as an independent factor for predicting patient outcomes. We constructed a prognostic signature based on seven iTreg-related genes (GIMAP5, SLA, MS4A7, ZNF366, POU2AF1, MRPL12, and COL5A1), which was applied to subdivide patients into high- and low-risk subgroups. Our results revealed that patients in the iTreg-related low-risk subgroup had a better prognosis and possibly greater sensitivity to traditional chemotherapy. Our study provides a novel iTreg-related signature to elucidate the mechanisms underlying LUAD prognosis and promote individualized chemotherapy treatment.

Dynamic immuno-nanomedicines in oncology

Anti-cancer therapeutics have achieved significant advances due to the emergence of immunotherapies that rely on the identification of tumors by the patients' immune system and subsequent tumor eradication. However, tumor cells often escape immunity, leading to poor responsiveness and easy tolerance to immunotherapy. Thus, the potentiated anti-tumor immunity in patients resistant to immunotherapies remains a challenge. Reactive oxygen species-based dynamic nanotherapeutics are not new in the anti-tumor field, but their potential as immunomodulators has only been demonstrated in recent years. Dynamic nanotherapeutics can distinctly enhance anti-tumor immune response, which derives the concept of the dynamic immuno-nanomedicines (DINMs). This review describes the pivotal role of DINMs in cancer immunotherapy and provides an overview of the clinical realities of DINMs. The preclinical development of emerging DINMs is also outlined. Moreover, strategies to synergize the antitumor immunity by DINMs in combination with other immunologic agents are summarized. Last but not least, the challenges and opportunities related to DINMs-mediated immune responses are also discussed.

Targeting the lipid kinase PIKfyve upregulates surface expression of MHC class I to augment cancer immunotherapy

Despite the remarkable clinical success of immunotherapies in a subset of cancer patients, many fail to respond to treatment and exhibit resistance. Here, we found that genetic or pharmacologic inhibition of the lipid kinase PIKfyve, a regulator of autophagic flux and lysosomal biogenesis, upregulated surface expression of major histocompatibility complex class I (MHC-I) in cancer cells via impairing autophagic flux, resulting in enhanced cancer cell killing mediated by CD8+ T cells. Genetic depletion or pharmacologic inhibition of PIKfyve elevated tumor-specific MHC-I surface expression, increased intratumoral functional CD8+ T cells, and slowed tumor progression in multiple syngeneic mouse models. Importantly, enhanced antitumor responses by Pikfyve-depletion were CD8+ T cell- and MHC-I-dependent, as CD8+ T cell depletion or B2m knockout rescued tumor growth. Furthermore, PIKfyve inhibition improved response to immune checkpoint blockade (ICB), adoptive cell therapy, and a therapeutic vaccine. High expression of PIKFYVE was also predictive of poor response to ICB and prognostic of poor survival in ICB-treated cohorts. Collectively, our findings show that targeting PIKfyve enhances immunotherapies by elevating surface expression of MHC-I in cancer cells, and PIKfyve inhibitors have potential as agents to increase immunotherapy response in cancer patients.

Antitumor Immune Responses in B2M-Deficient Cancers

β2-microglobulin (B2M) is a critical component of the MHC class I molecule and is required to present tumor antigens to T cells. Its loss results in acquired resistance to immune checkpoint blockade (ICB) therapies. However, there have been well-documented cases of B2M-inactivated tumors responding to ICB, justifying investigation of how an antitumor immune response can be generated to tumors without surface MHC class I. We knocked out B2M in three murine models with varying baseline MHC class I expression and sensitivity to anti-programmed death receptor (PD-1) therapy and analyzed the immune responses. MC38 and YUMMER2.1 without B2M responded to anti-PD-1 alone or with an IL2 agonist, and this was mediated by CD4+ T cells and natural killer (NK) cells. The more aggressive B16 without B2M expression only partially responded to the IL2 agonist, and this was dependent on NK cells. When analyzing nearly 300 pretreatment biopsies from patients with melanoma receiving PD-1 blockade-based therapies, we found infrequent B2M mutations or homozygous loss but more frequent LOH or copy-number gains. B2M LOH was enriched in biopsies from patients without response to therapy, and these biopsies were more frequently infiltrated by activated NK cells. We conclude that in the absence of B2M, activation of CD4+ T cells and NK cells can mediate responses to murine models of PD-1 blockade therapy. In addition, in human melanoma, the intratumoral presence of activated NK cells upon partial B2M loss likely selects against tumor escape through low surface MHC class I expression.

DGKα/ζ inhibition lowers the TCR affinity threshold and potentiates antitumor immunity

Diacylglycerol kinases (DGKs) attenuate diacylglycerol (DAG) signaling by converting DAG to phosphatidic acid, thereby suppressing pathways downstream of T cell receptor signaling. Using a dual DGKα/ζ inhibitor (DGKi), tumor-specific CD8 T cells with different affinities (TRP1high and TRP1low), and altered peptide ligands, we demonstrate that inhibition of DGKα/ζ can lower the signaling threshold for T cell priming. TRP1high and TRP1low CD8 T cells produced more effector cytokines in the presence of cognate antigen and DGKi. Effector TRP1high- and TRP1low-mediated cytolysis of tumor cells with low antigen load required antigen recognition, was mediated by interferon-γ, and augmented by DGKi. Adoptive T cell transfer into mice bearing pancreatic or melanoma tumors synergized with single-agent DGKi or DGKi and antiprogrammed cell death protein 1 (PD-1), with increased expansion of low-affinity T cells and increased cytokine production observed in tumors of treated mice. Collectively, our findings highlight DGKα/ζ as therapeutic targets for augmenting tumor-specific CD8 T cell function.

Aurora A kinase inhibition induces accumulation of SCLC tumor cells in mitosis with restored interferon signaling to increase response to PD-L1

Despite small cell lung cancers (SCLCs) having a high mutational burden, programmed death-ligand 1 (PD-L1) immunotherapy only modestly increases survival. A subset of SCLCs that lose their ASCL1 neuroendocrine phenotype and restore innate immune signaling (termed the "inflammatory" subtype) have durable responses to PD-L1. Some SCLCs are highly sensitive to Aurora kinase inhibitors, but early-phase trials show short-lived responses, suggesting effective therapeutic combinations are needed to increase their durability. Using immunocompetent SCLC genetically engineered mouse models (GEMMs) and syngeneic xenografts, we show durable efficacy with the combination of a highly specific Aurora A kinase inhibitor (LSN3321213) and PD-L1. LSN3321213 causes accumulation of tumor cells in mitosis with lower ASCL1 expression and higher expression of interferon target genes and antigen-presentation genes mimicking the inflammatory subtype in a cell-cycle-dependent manner. These data demonstrate that inflammatory gene expression is restored in mitosis in SCLC, which can be exploited by Aurora A kinase inhibition.

Breaking the mold: Overcoming resistance to immune checkpoint inhibitors

Immune checkpoint blockade-based therapies are effective against a sorts of cancers. However, drug resistance is a problem that cannot be ignored. This review intends to elucidate the mechanisms underlying drug tolerance induced by PD-1/PD-L1 inhibitors, as well as to outline proposed mechanism-based combination therapies and small molecule drugs that target intrinsic immunity and immune checkpoints. According to the differences of patients and types of cancer, the optimization of individualized combination therapy will help to enhance PD-1/PD-L1-mediated immunoregulation, reduce chemotherapy resistance, and provide new ideas for chemotherapy-resistant cancer.

Uncoupling CD4+ TIL-Mediated Tumor Killing from JAK-Signaling in Melanoma

PURPOSE

Impaired MHCI-presentation and insensitivity to immune effector molecules are common features of immune checkpoint blockade (ICB)-resistant tumors and can be, respectively, associated with loss of β2 microglobulin (B2M) or impaired IFNγ signaling. Patients with ICB-resistant tumors can respond to alternative immunotherapies, such as infusion of autologous tumor-infiltrating lymphocytes (TIL). CD4+ T cells can exert cytotoxic functions against tumor cells; however, it is unclear whether CD4+ T-cell responses can be exploited to improve the clinical outcomes of patients affected by ICB-resistant tumors.

EXPERIMENTAL DESIGN

Here, we exploited CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 gene editing to reproduce immune-resistant tumor phenotypes via gene knockout (KO). To determine the role of cytotoxic CD4+ TILs in ICB-resistant tumors, we investigated CD4+ TIL-mediated cytotoxicity in matched pairs of TILs and autologous melanoma cell lines, used as a model of patient-specific immune-tumor interaction. Around 40% of melanomas constitutively express MHC Class II molecules; hence, melanomas with or without natural constitutive MHC Class II expression (MHCIIconst+ or MHCIIconst-) were used.

RESULTS

CD4+ TIL-mediated cytotoxicity was not affected by B2M loss but was dependent on the expression of CIITA. MHCIIconst+ melanomas were killed by tumor-specific CD4+ TILs even in the absence of IFNγ-mediated MHCII upregulation, whereas IFNγ was necessary for CD4+ TIL-mediated cytotoxicity against MHCIIconst- melanomas. Notably, although tumor-specific CD4+ TILs did not kill JAK1KO MHCIIconst- melanomas even after IFNγ stimulation, sensitivity to CD4+ TIL-mediated cytotoxicity was maintained by JAK1KO MHCIIconst+ melanomas.

CONCLUSIONS

In conclusion, our data indicate that exploiting tumor-specific cytotoxic CD4+ TILs could help overcome resistance to ICB mediated by IFNγ-signaling loss in MHCIIconst+ melanomas. See related commentary by Betof Warner and Luke, p. 3829.

Synthetic viability induces resistance to immune checkpoint inhibitors in cancer cells

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized the treatment for multiple cancers. However, most of patients encounter resistance. Synthetic viability (SV) between genes could induce resistance. In this study, we established SV signature to predict the efficacy of ICI treatment for melanoma.

METHODS

We collected features and predicted SV gene pairs by random forest classifier. This work prioritized SV gene pairs based on CRISPR/Cas9 screens. SV gene pairs signature were constructed to predict the response to ICI for melanoma patients.

RESULTS

This study predicted robust SV gene pairs based on 14 features. Filtered by CRISPR/Cas9 screens, we identified 1,861 SV gene pairs, which were also related with prognosis across multiple cancer types. Next, we constructed the six SV pairs signature to predict resistance to ICI for melanoma patients. This study applied the six SV pairs signature to divide melanoma patients into high-risk and low-risk. High-risk melanoma patients were associated with worse response after ICI treatment. Immune landscape analysis revealed that high-risk melanoma patients had lower natural killer cells and CD8+ T cells infiltration.

CONCLUSIONS

In summary, the 14 features classifier accurately predicted robust SV gene pairs for cancer. The six SV pairs signature could predict resistance to ICI.

Gene signature reveals decreased SOX10-dependent transcripts in malignant cells from immune checkpoint inhibitor-resistant cutaneous melanomas

Evidence is mounting for cross-resistance between immune checkpoint and targeted kinase inhibitor therapies in cutaneous melanoma patients. Since the loss of the transcription factor, SOX10, causes tolerance to MAPK pathway inhibitors, we used bioinformatic techniques to determine if reduced SOX10 expression/activity is associated with immune checkpoint inhibitor resistance. We integrated SOX10 ChIP-seq, knockout RNA-seq, and knockdown ATAC-seq data from melanoma cell models to develop a robust SOX10 gene signature. We used computational methods to validate this signature as a measure of SOX10-dependent activity in independent single-cell and bulk RNA-seq SOX10 knockdown, cell line panel, and MAPK inhibitor drug-resistant datasets. Evaluation of patient single-cell RNA-seq data revealed lower levels of SOX10-dependent transcripts in immune checkpoint inhibitor-resistant tumors. Our results suggest that SOX10-deficient melanoma cells are associated with cross-resistance between targeted and immune checkpoint inhibitors and highlight the need to identify therapeutic strategies that target this subpopulation.

Biomarkers of immune checkpoint inhibitor response and toxicity: Challenges and opportunities

Immune checkpoint inhibitors have transformed cancer therapy, but their optimal use is still constrained by lack of response and toxicity. Biomarkers of response may facilitate drug development by allowing appropriate therapy selection and focusing clinical trial enrollment. However, aside from PD-L1 staining in a subset of tumors and rarely mismatch repair deficiency, no biomarkers are routinely used in the clinic. In addition, severe toxicities may cause severe morbidity, therapy discontinuation, and even death. Here, we review the state of the field with a focus on our research in therapeutic biomarkers and toxicities from immune checkpoint inhibitors.

CD8+ T cells maintain killing of MHC-I-negative tumor cells through the NKG2D-NKG2DL axis

The accepted paradigm for both cellular and anti-tumor immunity relies upon tumor cell killing by CD8+ T cells recognizing cognate antigens presented in the context of target cell major histocompatibility complex (MHC) class I (MHC-I) molecules. Likewise, a classically described mechanism of tumor immune escape is tumor MHC-I downregulation. Here, we report that CD8+ T cells maintain the capacity to kill tumor cells that are entirely devoid of MHC-I expression. This capacity proves to be dependent instead on interactions between T cell natural killer group 2D (NKG2D) and tumor NKG2D ligands (NKG2DLs), the latter of which are highly expressed on MHC-loss variants. Necessarily, tumor cell killing in these instances is antigen independent, although prior T cell antigen-specific activation is required and can be furnished by myeloid cells or even neighboring MHC-replete tumor cells. In this manner, adaptive priming can beget innate killing. These mechanisms are active in vivo in mice as well as in vitro in human tumor systems and are obviated by NKG2D knockout or blockade. These studies challenge the long-advanced notion that downregulation of MHC-I is a viable means of tumor immune escape and instead identify the NKG2D-NKG2DL axis as a therapeutic target for enhancing T cell-dependent anti-tumor immunity against MHC-loss variants.

Stocking the toolbox-Using preclinical models to understand the development and treatment of immune checkpoint inhibitor-induced immune-related adverse events

Cancer patients treated with immune checkpoint inhibitors (ICIs) are susceptible to a broad and variable array of immune-related adverse events (irAEs). With increasing clinical use of ICIs, defining the mechanism for irAE development is more critical than ever. However, it currently remains challenging to predict when these irAEs occur and which organ may be affected, and for many of the more severe irAEs, inaccessibility to the tissue site hampers mechanistic insight. This lack of understanding of irAE development in the clinical setting emphasizes the need for greater use of preclinical models that allow for improved prediction of biomarkers for ICI-initiated irAEs or that validate treatment options that inhibit irAEs without hampering the anti-tumor immune response. Here, we discuss the utility of preclinical models, ranging from exploring databases to in vivo animal models, focusing on where they are most useful and where they could be improved.

Omics Technologies Improving Breast Cancer Research and Diagnostics

Breast cancer (BC) has yielded approximately 2.26 million new cases and has caused nearly 685,000 deaths worldwide in the last two years, making it the most common diagnosed cancer type in the world. BC is an intricate ecosystem formed by both the tumor microenvironment and malignant cells, and its heterogeneity impacts the response to treatment. Biomedical research has entered the era of massive omics data thanks to the high-throughput sequencing revolution, quick progress and widespread adoption. These technologies-liquid biopsy, transcriptomics, epigenomics, proteomics, metabolomics, pharmaco-omics and artificial intelligence imaging-could help researchers and clinicians to better understand the formation and evolution of BC. This review focuses on the findings of recent multi-omics-based research that has been applied to BC research, with an introduction to every omics technique and their applications for the different BC phenotypes, biomarkers, target therapies, diagnosis, treatment and prognosis, to provide a comprehensive overview of the possibilities of BC research.

SETBP1 mutation determines sensitivity to immune checkpoint inhibitors in melanoma and NSCLC

SET binding protein 1 (SETBP1) plays crucial roles in various biological processes; however, its involvement in cancer immune checkpoint inhibitor (ICI) treatments has never been studied. In this study, we collected a total of 631 melanoma and 109 non-small cell lung cancer (NSCLC) samples treated with ICI agents (i.e., anti-CTLA-4, anti-PD-1/PD-L1, or combination therapy). Additionally, we obtained their corresponding somatic mutational profiles. We observed that SETBP1 mutated (SETBP1-MUT) melanoma patients exhibited significantly prolonged ICI survival outcomes compared to wild-type patients (HR: 0.56, 95% CI: 0.38-0.81, P = 0.002). Consistently, an elevated ICI response rate was also noticed in the SETBP1-MUT group (42.9% vs. 29.1%, P = 0.016). The Association of SETBP1 mutations with favorable immunotherapeutic prognosis and response was further supported by an independent NSCLC cohort (both P < 0.05). Additional immunological analyses revealed that favorable immune infiltration, tumor immunogenicity, and immune response circuits were enriched in SETBP1-MUT patients. Overall, our findings suggest that SETBP1 mutations may serve as a new biomarker for stratifying beneficiaries of ICI treatments in melanoma and NSCLC, which provides possible evidence for tailoring clinical immunotherapeutic strategies.

Site matters in metastatic melanoma

Metastasis and cross-therapy resistance to mitogen-activated protein kinase (MAPK) inhibition and immune checkpoint blockade (ICB) are significant clinical issues in melanoma. A new study in NatureMedicine by Liu et al. utilizes metastatic melanoma (MM) tumors from a rapid autopsy cohort to dissect genomic and transcriptomic features of therapy resistance, organ-specific gene signatures, and crosstalk between MM and organ sites.

Radiotherapy plus immune checkpoint inhibitor in prostate cancer

The immune checkpoint inhibitor (ICI) is a promising strategy for treating cancer. However, the efficiency of ICI monotherapy is limited, which could be mainly attributed to the tumor microenvironment of the "cold" tumor. Prostate cancer, a type of "cold" cancer, is the most common cancer affecting men's health. Radiotherapy is regarded as one of the most effective prostate cancer treatments. In the era of immune therapy, the enhanced antigen presentation and immune cell infiltration caused by radiotherapy might boost the therapeutic efficacy of ICI. Here, the rationale of radiotherapy combined with ICI was reviewed. Also, the scheme of radiotherapy combined with immune checkpoint blockades was suggested as a potential option to improve the outcome of patients with prostate cancer.

Molecular mechanisms of immunotherapy resistance in triple-negative breast cancer

The emergence of immunotherapy has profoundly changed the treatment model for triple-negative breast cancer (TNBC). But the heterogeneity of this disease resulted in significant differences in immunotherapy efficacy, and only some patients are able to benefit from this therapeutic modality. With the recent explosion in studies on the mechanism of cancer immunotherapy drug resistance, this article will focus on the processes of the immune response; summarize the immune evasion mechanisms in TNBC into three categories: loss of tumor-specific antigen, antigen presentation deficiency, and failure to initiate an immune response; together with the aberrant activation of a series of immune-critical signaling pathways, we will discuss how these activities jointly shape the immunosuppressive landscape within the tumor microenvironment. This review will attempt to elucidate the molecular mechanism of drug resistance in TNBC, identify potential targets that may assist in reversing drug resistance, and lay a foundation for research on identifying biomarkers for predicting immune efficacy and selection of breast cancer populations that may benefit from immunotherapy.

Modulation of tumor immune microenvironment by TAS-115, a multi-receptor tyrosine kinase inhibitor, promotes antitumor immunity and contributes anti-PD-1 antibody therapy

TAS-115 is an oral multi-receptor tyrosine kinase inhibitor that strongly inhibits kinases implicated in antitumor immunity, such as colony stimulating factor 1 receptor and vascular endothelial growth factor receptor. Because these kinases are associated with the modulation of immune pathways, we investigated the immunomodulatory activity of TAS-115. An in vitro cytokine assay revealed that TAS-115 upregulated interferon γ (IFNγ) and interleukin-2 secretion by T cells, suggesting that TAS-115 activated T cells. Gene expression analysis suggested that TAS-115 promoted M1 macrophage differentiation. In in vivo experiments, although TAS-115 exerted a moderate antitumor effect in the MC38 mouse colorectal cancer model under immunodeficient conditions, this effect was enhanced under immunocompetent conditions. Furthermore, combination of TAS-115 and anti-PD-1 antibody exhibited greater antitumor activity than either treatment alone. Flow cytometry analysis showed the increase in IFNγ- and granzyme B (Gzmb)-secreting tumor-infiltrating T cells by TAS-115 treatment. The combination treatment further increased the percentage of Gzmb+CD8+ T cells and decreased the percentage of macrophages compared with either treatment alone. These results highlight the potential therapeutic effect of TAS-115 in combination with PD-1 blockade, mediated via activation of antitumor immunity by TAS-115.

Clinical and molecular overview of immunotherapeutic approaches for malignant skin melanoma: Past, present and future

Traditional therapeutic approaches for malignant melanoma, have proved to be limited and/or ineffective, especially with respect to their role in improving patient survival and tumor recurrence. In this regard, immunotherapy has been demonstrated to be a promising therapeutic alternative, boosting antitumor responses through the modulation of cell signaling pathways involved in the effector mechanisms of the immune system, particularly, the so-called "immunological checkpoints". Clinical studies on the efficacy and safety of immunotherapeutic regimens, alone or in combination with other antitumor approaches, have increased dramatically in recent decades, with very encouraging results. Hence, this review will discuss the current immunotherapeutic regimens used to treat malignant melanoma, as well as the molecular and cellular mechanisms involved. In addition, current clinical studies that have investigated the use, efficacy, and adverse events of immunotherapy in melanoma will also be discussed.

Therapeutic targeting of tumour myeloid cells

Myeloid cells are pivotal within the immunosuppressive tumour microenvironment. The accumulation of tumour-modified myeloid cells derived from monocytes or neutrophils - termed 'myeloid-derived suppressor cells' - and tumour-associated macrophages is associated with poor outcome and resistance to treatments such as chemotherapy and immune checkpoint inhibitors. Unfortunately, there has been little success in large-scale clinical trials of myeloid cell modulators, and only a few distinct strategies have been used to target suppressive myeloid cells clinically so far. Preclinical and translational studies have now elucidated specific functions for different myeloid cell subpopulations within the tumour microenvironment, revealing context-specific roles of different myeloid cell populations in disease progression and influencing response to therapy. To improve the success of myeloid cell-targeted therapies, it will be important to target tumour types and patient subsets in which myeloid cells represent the dominant driver of therapy resistance, as well as to determine the most efficacious treatment regimens and combination partners. This Review discusses what we can learn from work with the first generation of myeloid modulators and highlights recent developments in modelling context-specific roles for different myeloid cell subtypes, which can ultimately inform how to drive more successful clinical trials.

CD25: A potential tumor therapeutic target

CD25 is the alpha-chain of the heterotrimer IL-2 receptor. CD25 is expressed on the surface of both immune and non-immune cells with different frequencies. For cancers, CD25 is expressed at high levels in many types of hematological malignancies, but at low levels in most solid tumors. CD25 is also highly expressed in activated circulating immune cells and regulatory T cells (Tregs). Infiltration of Tregs in the tumor microenvironment can lead to an imbalanced ratio of effector T cells (Teffs) and Tregs, which is associated with the progression of cancers. A rescued Teff/Treg cell ratio indicates an efficient anti-tumor response to immunotherapy. CD25 as a potential target for the depletion of Tregs is critical in developing new immunotherapeutic strategies. Few articles have summarized the relationships between CD25 and tumors, or the recent progress of drugs targeting CD25. In this paper, we will discuss the structures of IL-2 and IL-2R, the biological function of CD25 and its important role in tumor therapy. In addition, the latest research on drugs targeting CD25 has been summarized, providing guidance for future drug development.

IFNγ is a central node of cancer immune equilibrium

Tumors in immune equilibrium are held in balance between outgrowth and destruction by the immune system. The equilibrium phase defines the duration of clinical remission and stable disease, and escape from equilibrium remains a major clinical problem. Using a non-replicating HSV-1 vector expressing interleukin-12 (d106S-IL12), we developed a mouse model of therapy-induced immune equilibrium, a phenomenon previously seen only in humans. This immune equilibrium was centrally reliant on interferon-γ (IFNγ). CD8+ T cell direct recognition of MHC class I, perforin/granzyme-mediated cytotoxicity, and extrinsic death receptor signaling such as Fas/FasL were all individually dispensable for equilibrium. IFNγ was critically important and played redundant roles in host and tumor cells such that IFNγ sensing in either compartment was sufficient for immune equilibrium. We propose that these redundant mechanisms of action are integrated by IFNγ to protect from oncogenic or chronic viral threats and establish IFNγ as a central node in therapy-induced immune equilibrium.

HiJAKing Immunotherapy-Resistant Melanoma for a Cure

Immune checkpoint blockers (ICBs) have brought great promise to patients with advanced melanoma, a tumor type that was claimed largely incurable not long ago. However, therapeutic resistance to ICBs has limited their utility in the clinic. Here, we provide a commentary on recent research endeavors concerning ICB resistance in melanoma patients.

Treatment of Recurrent Melanoma Following Adjuvant Therapy

In the era of effective therapies in melanoma, notably the widespread use of two types of adjuvant treatments: anti-PD-1 immunotherapies and therapies targeting the mitogen-activated protein kinase pathway, for BRAF-mutant patients, an important question arises about how to treat these patients in case of recurrent melanoma following adjuvant therapy. Prospective data are lacking in this area and might be difficult to obtain due to the constant progress being made in the field. Therefore, we reviewed available data suggesting that the initial adjuvant treatment received and the following events provide information about the biology of the disease and the probability of response to following systemic treatments. Thus, in case of relapse during or just after adjuvant anti-PD-1, immune resistance is probable, an anti-PD-1 monotherapy rechallenge has a low likelihood of clinical benefit, and escalation with a combination of immunotherapies should be given priority. In case of relapse during treatment with BRAF plus MEK inhibitors, there may be a risk of lower efficacy of immunotherapy than in naïve patients since this relapse attests not only to a resistance to BRAF-MEK inhibition, but also the introduction of immunotherapy to rescue a progression on targeted therapy. In case of relapse long after adjuvant treatment cessation, whatever the treatment received, no conclusion can be drawn about the efficacy of these drugs, and these patients can be treated like naïve patients. Thus, a combination of anti-PD-1 and anti-CTLA4 is probably the best solution, and the following line can be BRAF-MEK inhibitors in BRAF-mutated patients. Finally, in case of recurrent melanoma following adjuvant therapy, given the promising upcoming strategies, inclusion in a clinical trial should be offered as frequently as possible.

Resistance to immune checkpoint inhibitors and the tumor microenvironment

Immune checkpoint inhibitors (ICIs) have contributed significantly to the treatment of various types of cancer, including skin cancer. However, not all patients respond; some patients do not respond at all (primary resistance), while others experience recurrence after the initial response (acquired resistance). Therefore, overcoming ICI resistance is an urgent priority. Numerous ICI resistance mechanisms have been reported. They are seemingly quite complex, varying from patient to patient. However, most involve T-cell activation processes, especially in the tumor microenvironment (TME). ICIs exert their effects in the TME by reactivating suppressed T cells through inhibition of immune checkpoint molecules, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed cell death protein 1 (PD-1). Thus, this review focuses on the resistance mechanisms based on the T-cell activation process. Here, we classify the main mechanisms of ICI resistance into three categories based on (1) antigen recognition, (2) T-cell migration and infiltration, and (3) effector functions of T cells. By identifying and understanding these resistance mechanisms individually, including unknown mechanisms, we seek to contribute to the development of novel treatments to overcome ICI resistance.

Distinct Mechanisms of Mismatch-Repair Deficiency Delineate Two Modes of Response to Anti-PD-1 Immunotherapy in Endometrial Carcinoma

Mismatch repair-deficient (MMRd) cancers have varied responses to immune-checkpoint blockade (ICB). We conducted a phase II clinical trial of the PD-1 inhibitor pembrolizumab in 24 patients with MMRd endometrial cancer (NCT02899793). Patients with mutational MMRd tumors (6 patients) had higher response rates and longer survival than those with epigenetic MMRd tumors (18 patients). Mutation burden was higher in tumors with mutational MMRd compared with epigenetic MMRd; however, within each category of MMRd, mutation burden was not correlated with ICB response. Pretreatment JAK1 mutations were not associated with primary resistance to pembrolizumab. Longitudinal single-cell RNA-seq of circulating immune cells revealed contrasting modes of antitumor immunity for mutational versus epigenetic MMRd cancers. Whereas effector CD8+ T cells correlated with regression of mutational MMRd tumors, activated CD16+ NK cells were associated with ICB-responsive epigenetic MMRd tumors. These data highlight the interplay between tumor-intrinsic and tumor-extrinsic factors that influence ICB response.

SIGNIFICANCE

The molecular mechanism of MMRd is associated with response to anti-PD-1 immunotherapy in endometrial carcinoma. Tumors with epigenetic MMRd or mutational MMRd are correlated with NK cell or CD8+ T cell-driven immunity, respectively. Classifying tumors by the mechanism of MMRd may inform clinical decision-making regarding cancer immunotherapy. This article is highlighted in the In This Issue feature, p. 247.

Combination of Expanded Allogeneic NK Cells and T Cell-Based Immunotherapy Exert Enhanced Antitumor Effects

Immunotherapies based on immune checkpoint blockade, neoantigen-reactive tumor-infiltrating lymphocytes and T cell receptor-engineered T cells (TCR-T) have achieved favorable clinical outcomes in tumor treatment. However, sustained immune response and tumor regression have been observed only in a few patients due to immune escape. Natural killer (NK) cells can mediate direct tumor lysis and target cancer cells with low or no expression of human leukocyte antigen class I (HLA-I) that are no longer recognized by T cells during immune escape. Therefore, the combination of T cell-based immunotherapy and NK cell therapy is a promising strategy for improving antitumor response and response rate. However, allogeneic NK cells for adoptive cell therapy have been limited by both the required cell number and quality. Here, we developed an efficient manufacturing system that relies on genetically modified K562 cells for the expansion of high-quality NK cells derived from peripheral blood mononuclear cells. NK cells with the optimal expansion and activity were identified by comparing the different culture systems. Furthermore, we demonstrated that the cooperation of NK cells with tumor-reactive T cells or with NY-ESO-1-specific TCR-T cells further enhanced tumors lysis, especially against tumors with downregulated HLA-I expression. The advantages of HLA-mismatch and non-rejection by other allogeneic immune cells demonstrated the potential of "off-the-shelf" NK cells with the capacity to target tumors for immunotherapy. Our results indicate that the combination strategy based on T cell and allogeneic NK cell immunotherapy might have potential for overcoming the barrier of immune incompetence caused by HLA-I downregulation.

The Latest Approach of Immunotherapy with Endosomal TLR Agonists Improving NK Cell Function: An Overview

Toll-like receptors (TLRs) are the most well-defined pattern recognition receptors (PRR) of several cell types recognizing pathogens and triggering innate immunity. TLRs are also expressed on tumor cells and tumor microenvironment (TME) cells, including natural killer (NK) cells. Cell surface TLRs primarily recognize extracellular ligands from bacteria and fungi, while endosomal TLRs recognize microbial DNA or RNA. TLR engagement activates intracellular pathways leading to the activation of transcription factors regulating gene expression of several inflammatory molecules. Endosomal TLR agonists may be considered as new immunotherapeutic adjuvants for dendritic cell (DC) vaccines able to improve anti-tumor immunity and cancer patient outcomes. The literature suggests that endosomal TLR agonists modify TME on murine models and human cancer (clinical trials), providing evidence that locally infused endosomal TLR agonists may delay tumor growth and induce tumor regression. Recently, our group demonstrated that CD56^bright NK cell subset is selectively responsive to TLR8 engagement. Thus, TLR8 agonists (loaded or not to nanoparticles or other carriers) can be considered a novel strategy able to promote anti-tumor immunity. TLR8 agonists can be used to activate and expand in vitro circulating or intra-tumoral NK cells to be adoptively transferred into patients.

Mechanisms of Resistance and Strategies to Combat Resistance in PD-(L)1 Blockade

Prolonged survival and durable responses in several late-stage cancers such as melanoma and lung cancer have been made possible with the use of immune checkpoint inhibitors targeting the programmed cell-death protein 1 (PD-1) or its ligand PD-L1. While it is prudent to focus on the unprecedented and durable clinical responses, there are subsets of cancer patients that do not respond to immunotherapies or respond early and then relapse later. Many pathways of resistance have been characterized, and more continue to be uncovered. To overcome the development of resistance, an in-depth investigation is necessary to identify alternative immune receptors and signals with the overarching goal of expanding treatment options for those with demonstrated resistance to PD1 checkpoint immunotherapy. In this mini-review, we will discuss the mechanisms by which tumors exhibit resistance to anti-PD-1/PD-L1 immunotherapy and explore strategies to overcome such resistances.

When Cancer Cells Become the Enablers of an Antitumor Immune Response

Tumor-specific cytotoxic T cells unleashed by the blockade of immune checkpoints have to overcome a hostile tumor microenvironment (TME). They start from very small numbers of T cells with tumor antigen specificity and, despite expansion, likely remain at a numerical disadvantage to the tumor cells they target. To overcome these obstacles, we propose that T cells need to change the TME to make it permissive for their antitumor effects by altering the phenotype of cells beyond the cancer cells they are in physical contact with. In this process, IFNγ secreted by tumor-specific T cells plays a critical role, as it changes the expression of hundreds of genes in cancer cells and other immune cells in the TME up to 40 layers of cells away from their location, effectively turning these cells into enablers of the antitumor immune response. In this perspective, we postulate that the clinical activity of cancer immunotherapy with immune-checkpoint blocking antibodies and adoptively transferred T cells requires that cancer cells facilitate the antitumor immune response. IFNγ effectively changes the balance of power in the TME to enable the antitumor activity of tumor antigen-specific cytotoxic T cells.

The immune-related role of beta-2-microglobulin in melanoma

Despite the remarkable success of immunotherapy in the treatment of melanoma, resistance to these agents still affects patient prognosis and response to therapies. Beta-2-microglobulin (β2M), an important subunit of major histocompatibility complex (MHC) class I, has important biological functions and roles in tumor immunity. In recent years, increasing studies have shown that B2M gene deficiency can inhibit MHC class I antigen presentation and lead to cancer immune evasion by affecting β2M expression. Based on this, B2M gene defect and T cell-based immunotherapy can interact to affect the efficacy of melanoma treatment. Taking into account the many recent advances in B2M-related melanoma immunity, here we discuss the immune function of the B2M gene in tumors, its common genetic alteration in melanoma, and its impact on and related improvements in melanoma immunotherapy. Our comprehensive review of β2M biology and its role in tumor immunotherapy contributes to understanding the potential of B2M gene as a promising melanoma therapeutic target.

Inhibition of IL-17A Protects against Thyroid Immune-Related Adverse Events while Preserving Checkpoint Inhibitor Antitumor Efficacy

Immune checkpoint inhibitor (ICI) immunotherapy leverages the body's own immune system to attack cancer cells but leads to unwanted autoimmune side effects in up to 60% of patients. Such immune-related adverse events (IrAEs) may lead to treatment interruption, permanent organ dysfunction, hospitalization, and premature death. Thyroiditis is one of the most common IrAEs, but the cause of thyroid IrAEs remains unknown. In this study, we use a new, physiologically relevant mouse model of ICI-associated autoimmunity to identify a key role for type 3 immune cells in the development of thyroid IrAEs. Multiple lineages of IL-17A-producing T cells expand in thyroid tissue with ICI treatment. Intrathyroidal IL-17A-producing innate-like γδT17 cells were increased in tumor-free mice, whereas adaptive Th17 cells were also prominent in tumor-bearing mice, following ICI treatment. Furthermore, Ab-based inhibition of IL-17A, a clinically available therapy, significantly reduced thyroid IrAE development in ICI-treated mice with and without tumor challenge. Finally, combination of IL-17A neutralization with ICI treatment in multiple tumor models did not reduce ICI antitumor efficacy. These studies suggest that targeting Th17 and γδT17 cell function via the IL-17A axis may reduce IrAEs without impairing ICI antitumor efficacy and may be a generalizable strategy to address type 3 immune-mediated IrAEs.

Therapeutic KRASG12C inhibition drives effective interferon-mediated antitumor immunity in immunogenic lung cancers

Recently developed KRASG12C inhibitory drugs are beneficial to lung cancer patients harboring KRASG12C mutations, but drug resistance frequently develops. Because of the immunosuppressive nature of the signaling network controlled by oncogenic KRAS, these drugs can indirectly affect antitumor immunity, providing a rationale for their combination with immune checkpoint blockade. In this study, we have characterized how KRASG12C inhibition reverses immunosuppression driven by oncogenic KRAS in a number of preclinical lung cancer models with varying levels of immunogenicity. Mechanistically, KRASG12C inhibition up-regulates interferon signaling via Myc inhibition, leading to reduced tumor infiltration by immunosuppressive cells, enhanced infiltration and activation of cytotoxic T cells, and increased antigen presentation. However, the combination of KRASG12C inhibitors with immune checkpoint blockade only provides synergistic benefit in the most immunogenic tumor model. KRASG12C inhibition fails to sensitize cold tumors to immunotherapy, with implications for the design of clinical trials combining KRASG12C inhibitors with anti-PD1 drugs.

HSPG2 Mutation Association with Immune Checkpoint Inhibitor Outcome in Melanoma and Non-Small Cell Lung Cancer

Immune checkpoint inhibitors (ICIs) markedly promote the survival outcome of advanced melanoma and non-small cell lung cancer (NSCLC). Clinically, favorable ICI treatment efficacy is noticed only in a smaller proportion of patients. Heparan sulfate proteoglycan 2 (HSPG2) frequently mutates in both tumors. Herein, we aim to investigate the immunotherapeutic and immunological roles of HSPG2 mutations in melanoma and NSCLC. A total of 631 melanoma samples and 109 NSCLC samples with both somatic mutational profiles and clinical immunotherapy data were curated. In addition, by using The Cancer Genome Atlas data, genomic and immunological traits behind HSPG2 mutations were elucidated. Melanoma patients with HSPG2 mutations had a markedly extended ICI outcome than other patients. An association between HSPG2 mutations and the improved outcome was further confirmed in NSCLC. In addition, an elevated ICI response rate was presented in HSPG2-mutated NSCLC patients (81.8% vs. 29.7%, p = 0.002). Subsequent analyses revealed that HSPG2-mutated patients had a favorable abundance of response immunocytes, an inferior abundance of suppression immunocytes, enhanced mutational burden, and interferon response-relevant signaling pathways. We uncovered that HSPG2 mutations were predictive of a better ICI response and associated with preferable immunogenicity, which may be considered as a genomic determinant to customize biotherapy strategies.