Immune Checkpoint Inhibitors for the Treatment of Cancer: Clinical Impact and Mechanisms of Response and Resistance

Immune checkpoints and immunotherapy in non-small cell lung cancer: Novel study progression, challenges and solutions

Lung cancer is the most common type of cancer with the highest mortality rate worldwide. Non-small cell lung cancer (NSCLC) accounts for ~85% of the total number of lung cancer cases. In the past two decades, immunotherapy has become a more promising treatment method than traditional treatments (surgery, radiotherapy and chemotherapy). Immunotherapy has been shown to improve the survival rate of patients and to have a superior effect when controlling lung cancer than traditional therapy. However, only a small number of patients can benefit from immunotherapy, and not all patients who qualify experience long-term benefits. In the clinic, the objective response rate of programmed cell death protein 1 treatment without the prior screening of patients is only 15-20%. Immunotherapy is associated with both opportunities and challenges for patients with NSCLC. The current challenges of immunotherapy include the lack of accurate biomarkers, inevitable resistance and insufficient understanding of immune checkpoints. In previous years, several methods for overcoming the challenges posed by immunotherapy have been proposed, but combination therapy is the most suitable choice. A large number of studies have shown that the combination of drugs can significantly improve their efficacy, compared with monotherapy, and that some therapeutic combinations have been approved by the Food and Drug Administration for the treatment of NSCLC. Traditional Chinese medicine (TCM) is a traditional medical practice in China that can play an important role in immunotherapy. Most agents used in TCM originate from plants, and have the advantages of low toxicity and multiple targets. In addition, TCM includes a unique class of drugs that can improve autoimmunity. Therefore, TCM may be a promising treatment method for all types of cancer.

Unraveling the Heterogeneity and Ontogeny of Dendritic Cells Using Single-Cell RNA Sequencing

Dendritic cells (DCs) play essential roles in innate and adaptive immunity and show high heterogeneity and intricate ontogeny. Advances in high-throughput sequencing technologies, particularly single-cell RNA sequencing (scRNA-seq), have improved the understanding of DC subsets. In this review, we discuss in detail the remarkable perspectives in DC reclassification and ontogeny as revealed by scRNA-seq. Moreover, the heterogeneity and multifunction of DCs during diseases as determined by scRNA-seq are described. Finally, we provide insights into the challenges and future trends in scRNA-seq technologies and DC research.

Neuron - specific enolase predicts the prognosis in advanced small cell lung cancer patients treated with first-line PD-1/PD-L1 inhibitors

There has been no effective biomarker for small cell lung cancer (SCLC) patients with first-line immune checkpoint inhibitors (ICIs) treatment. The predictive value of neuron-specific enolase (NSE) in this cohort remains unclear.The medical records of 254 consecutive SCLC patients receiving programmed cell death receptor-1/programmed cell death-ligand 1 (PD-1/PD-L1) inhibitors were compiled from January 2015 to October 2020 in Chinese PLA General Hospital. Survival analysis was performed to explore the prognostic role of NSE at baseline and 3 weeks post treatment.One hundred two advanced SCLC patients treated with first-line PD-1/PD-L1 inhibitors were enrolled in this study. Normal baseline NSE levels were correlated with significantly prolonged progression-free survival (PFS, median: 8.7 vs 4.7 months, P = .006) and overall survival (OS, median: 23.8 vs 15.2 months, P = .014) compared with elevated baseline NSE levels, so as for normal NSE levels at 3 weeks with prolonged PFS (median PFS: 8.4 vs 4.5 months, P = .0002) and OS (median OS: 23.3 vs 7.4 months, P < .0001). Intriguingly, elevated NSE levels at 3 weeks were associated with shorter PFS (median PFS: 4.5 vs 5.8 months, P = .04) and OS (median OS: 5.5 vs 14.7 months, P < .0001) compared with normal NSE levels in the elevated baseline NSE subgroup. Most subgroup analyses stratified by clinical characteristics confirmed the prognostic value of baseline NSE level.Elevated NSE levels at baseline and 3 weeks were associated with worse prognosis in advanced SCLC patients receiving first-line ICIs treatment. NSE level might be applied as a useful prognostic tool for SCLC patients with immunotherapy.

KAT2B is an immune infiltration-associated biomarker predicting prognosis and response to immunotherapy in non-small cell lung cancer

BACKGROUND

Over the past few years, dramatic breakthroughs in the field of tumor immunotherapy with immune checkpoint inhibitors (ICIs) have made a therapeutic revolution for non-small cell lung cancer (NSCLC). While only some patients present a favorable response to this treatment. It is urgent to explore the potential molecular mechanisms underlying the regulation of tumor immune microenvironment in the process of immunotherapy. Lysine acetyltransferase 2B (KAT2B) plays a crucial role in the regulation of gene expression at the post-transcriptional level by acetylation, and is associated with many types of cancer.

METHODS

RNA-sequencing data, genetic mutation data, and corresponding clinical information were extracted from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, then subjected to immune characteristics, gene expression, survival, genetic alteration, enrichment analyses.

RESULTS

KAT2B expression correlated positively with infiltrating levels of multiple immune cells and mRNA expression levels of immune checkpoint genes in NSCLC. Furthermore, KAT2B expression was downregulated in tumor tissues, and low KAT2B expression was associated with unsatisfactory efficacy of immune checkpoint blockade (ICB) and poor prognosis of patients with lung adenocarcinoma. Moreover, there were higher somatic genes mutation frequency in patients with low expression of KAT2B. Finally, functional enrichment analysis suggested that KAT2B was mainly linked to the regulation of immune cells and interferon - gamma (IFN-γ) mediated signaling pathways, response to IFN-γ, antigen processing and presentation.

CONCLUSION

This is the first comprehensive study to disclose that KAT2B is correlated with immune infiltrates and may serve as a novel biomarker predicting prognosis and response to immunotherapy in NSCLC.

Firing up the Tumor Microenvironment with Nanoparticle-Based Therapies

Therapies mobilizing host immunity against cancer cells have profoundly improved prognosis of cancer patients. However, efficacy of immunotherapies depends on local immune conditions. The "cold" tumor, which is characterized by lacking inflamed T cells, is insensitive to immunotherapy. Current strategies of improving the "cold" tumor microenvironment are far from satisfying. Nanoparticle-based therapies provide novel inspiration in firing up the tumor microenvironment. In this review, we presented progress and limitations of conventional immunotherapies. Then, we enumerate advantages of nanoparticle-based therapies in remodeling the "cold" tumor microenvironment. Finally, we discuss the prospect of nanoparticle-based therapies in clinical application.

Targeting MDSC for Immune-Checkpoint Blockade in Cancer Immunotherapy: Current Progress and New Prospects

Immune-checkpoint blockade (ICB) demonstrated inspiring effect and great promise in anti-cancer therapy. However, many obstacles, such as drug resistance and difficulty in patient selection, limited the efficacy of ICB therapy and awaited to be overcome. By timely identification and intervention of the key immune-suppressive promotors in the tumor microenvironment (TME), we may better understand the mechanisms of cancer immune-escape and use novel strategies to enhance the therapeutic effect of ICB. Myeloid-derived suppressor cell (MDSC) is recognized as a major immune suppressor in the TME. In this review, we summarized the roles MDSC played in the cancer context, focusing on its negative biologic functions in ICB therapy, discussed the strategies targeted on MDSC to optimize the diagnosis and therapy process of ICB and improve the efficacy of ICB therapy against malignancies.

The effect of concomitant use of statins, NSAIDs, low-dose aspirin, metformin and beta-blockers on outcomes in patients receiving immune checkpoint inhibitors: a systematic review and meta-analysis

Immunotherapy shows promising therapeutic efficacy against various types of cancer, but most fail to respond. Preclinical studies have suggested that concomitant medications, such as statins, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, metformin and beta-blockers, might affect clinical outcomes if used with immune checkpoint inhibitors (ICIs), but their clinical roles are conflicting. This meta-analysis investigates the effect of these concomitant medications on outcomes in patients treated with ICIs. A search was conducted for all reports published until 31 March 2021 in PubMed, Web of Science, Cochrane Library, EMBASE and conference proceedings. Studies were included if they investigated the association between the concomitant use of these medications and progression-free survival (PFS) or overall survival (OS) during ICI treatment. A total of 3331 patients from 13 eligible studies were included. Among them, five articles on statins, six studies evaluating NSAIDs, five studies employing low-dose aspirin, eight studies on metformin and four articles on beta-blockers were included. The concomitant use of statins during ICI treatment was correlated with improved OS and PFS. Low-dose aspirin was associated with better PFS instead of OS. No significant association was demonstrated between the concurrent use of NSAIDs, beta-blockers and metformin and OS or PFS. The concomitant use of statins and low-dose aspirin during ICI treatment showed a positive impact on treatment outcomes. The concurrent use of NSAIDs, beta-blockers and metformin is not significantly associated with clinical benefits. The effect of these medications in different cancer patients treated with ICI is needed to be further validated.

Leveraging NKG2D Ligands in Immuno-Oncology

Immune checkpoint inhibitors (ICI) revolutionized the field of immuno-oncology and opened new avenues towards the development of novel assets to achieve durable immune control of cancer. Yet, the presence of tumor immune evasion mechanisms represents a challenge for the development of efficient treatment options. Therefore, combination therapies are taking the center of the stage in immuno-oncology. Such combination therapies should boost anti-tumor immune responses and/or target tumor immune escape mechanisms, especially those created by major players in the tumor microenvironment (TME) such as tumor-associated macrophages (TAM). Natural killer (NK) cells were recently positioned at the forefront of many immunotherapy strategies, and several new approaches are being designed to fully exploit NK cell antitumor potential. One of the most relevant NK cell-activating receptors is NKG2D, a receptor that recognizes 8 different NKG2D ligands (NKG2DL), including MICA and MICB. MICA and MICB are poorly expressed on normal cells but become upregulated on the surface of damaged, transformed or infected cells as a result of post-transcriptional or post-translational mechanisms and intracellular pathways. Their engagement of NKG2D triggers NK cell effector functions. Also, MICA/B are polymorphic and such polymorphism affects functional responses through regulation of their cell-surface expression, intracellular trafficking, shedding of soluble immunosuppressive isoforms, or the affinity of NKG2D interaction. Although immunotherapeutic approaches that target the NKG2D-NKG2DL axis are under investigation, several tumor immune escape mechanisms account for reduced cell surface expression of NKG2DL and contribute to tumor immune escape. Also, NKG2DL polymorphism determines functional NKG2D-dependent responses, thus representing an additional challenge for leveraging NKG2DL in immuno-oncology. In this review, we discuss strategies to boost MICA/B expression and/or inhibit their shedding and propose that combination strategies that target MICA/B with antibodies and strategies aimed at promoting their upregulation on tumor cells or at reprograming TAM into pro-inflammatory macrophages and remodeling of the TME, emerge as frontrunners in immuno-oncology because they may unleash the antitumor effector functions of NK cells and cytotoxic CD8 T cells (CTL). Pursuing several of these pipelines might lead to innovative modalities of immunotherapy for the treatment of a wide range of cancer patients.

Intersection of Two Checkpoints: Could Inhibiting the DNA Damage Response Checkpoint Rescue Immune Checkpoint-Refractory Cancer?

Metastatic cancers resistant to immunotherapy require novel management strategies. DNA damage response (DDR) proteins, including ATR (ataxia telangiectasia and Rad3-related), ATM (ataxia telangiectasia mutated) and DNA-PK (DNA-dependent protein kinase), have been promising therapeutic targets for decades. Specific, potent DDR inhibitors (DDRi) recently entered clinical trials. Surprisingly, preclinical studies have now indicated that DDRi may stimulate anti-tumor immunity to augment immunotherapy. The mechanisms governing how DDRi could promote anti-tumor immunity are not well understood; however, early evidence suggests that they can potentiate immunogenic cell death to recruit and activate antigen-presenting cells to prime an adaptive immune response. Merkel cell carcinoma (MCC) is well suited to test these concepts. It is inherently immunogenic as ~50% of patients with advanced MCC persistently benefit from immunotherapy, making MCC one of the most responsive solid tumors. As is typical of neuroendocrine cancers, dysfunction of p53 and Rb with upregulation of Myc leads to the very rapid growth of MCC. This suggests high replication stress and susceptibility to DDRi and DNA-damaging agents. Indeed, MCC tumors are particularly radiosensitive. Given its inherent immunogenicity, cell cycle checkpoint deficiencies and sensitivity to DNA damage, MCC may be ideal for testing whether targeting the intersection of the DDR checkpoint and the immune checkpoint could help patients with immunotherapy-refractory cancers.

The Human Melanoma Proteome Atlas-Complementing the melanoma transcriptome

The MM500 meta-study aims to establish a knowledge basis of the tumor proteome to serve as a complement to genome and transcriptome studies. Somatic mutations and their effect on the transcriptome have been extensively characterized in melanoma. However, the effects of these genetic changes on the proteomic landscape and the impact on cellular processes in melanoma remain poorly understood. In this study, the quantitative mass-spectrometry-based proteomic analysis is interfaced with pathological tumor characterization, and associated with clinical data. The melanoma proteome landscape, obtained by the analysis of 505 well-annotated melanoma tumor samples, is defined based on almost 16 000 proteins, including mutated proteoforms of driver genes. More than 50 million MS/MS spectra were analyzed, resulting in approximately 13,6 million peptide spectrum matches (PSMs). Altogether 13 176 protein-coding genes, represented by 366 172 peptides, in addition to 52 000 phosphorylation sites, and 4 400 acetylation sites were successfully annotated. This data covers 65% and 74% of the predicted and identified human proteome, respectively. A high degree of correlation (Pearson, up to 0.54) with the melanoma transcriptome of the TCGA repository, with an overlap of 12 751 gene products, was found. Mapping of the expressed proteins with quantitation, spatiotemporal localization, mutations, splice isoforms, and PTM variants was proven not to be predicted by genome sequencing alone. The melanoma tumor molecular map was complemented by analysis of blood protein expression, including data on proteins regulated after immunotherapy. By adding these key proteomic pillars, the MM500 study expands the knowledge on melanoma disease.

The human melanoma proteome atlas-Defining the molecular pathology

The MM500 study is an initiative to map the protein levels in malignant melanoma tumor samples, focused on in-depth histopathology coupled to proteome characterization. The protein levels and localization were determined for a broad spectrum of diverse, surgically isolated melanoma tumors originating from multiple body locations. More than 15,500 proteoforms were identified by mass spectrometry, from which chromosomal and subcellular localization was annotated within both primary and metastatic melanoma. The data generated by global proteomic experiments covered 72% of the proteins identified in the recently reported high stringency blueprint of the human proteome. This study contributes to the NIH Cancer Moonshot initiative combining detailed histopathological presentation with the molecular characterization for 505 melanoma tumor samples, localized in 26 organs from 232 patients.

Oropharyngeal Squamous Cell Carcinoma Treatment in the Era of Immune Checkpoint Inhibitors

While head and neck squamous cell carcinomas (HNSCC) are marginally decreasing due to the reduction in exposure to the major risk factors, tobacco and alcohol, the incidence of high-risk human papillomavirus (HPV)-positive oropharynx squamous cell carcinomas (OPSCC), especially those in the tonsil and base of tongue subsites, are increasing. Patients with the latter are younger, display a longer overall survival, and show a lower recurrence rate after standard-of-care treatment than those with HPV-negative OPSCC. This may reflect an important role for immune surveillance and control during the natural history of the virally driven tumour development. Immune deviation through acquisition of immune-suppressive factors in the tumour microenvironment (TME) is discussed in relation to treatment response. Understanding how the different immune factors are integrated in the TME battleground offers opportunities for identifying prognostic biomarkers as well as novel therapeutic strategies. OPSCC generally receive surgery or radiotherapy for early-stage tumour treatment, but many patients present with locoregionally advanced disease requiring multimodality therapies which can involve considerable complications. This review focuses on the utilization of newly emerged immune checkpoint inhibitors (PD-1/PD-L1 pathway) for treatment of HNSCC, in particular HPV-positive OPSCC, since they could be less toxic and more efficacious. PD-1/PD-L1 expression in the TME has been extensively investigated as a biomarker of patient response but is yet to provide a really effective means for stratification of treatment. Extensive testing of combinations of therapeutic approaches by types and sequencing will fuel the next evolution of treatment for OPSCC.

Influence of Tumor Immune Infiltration on Immune Checkpoint Inhibitor Therapeutic Efficacy: A Computational Retrospective Study

The tumor immune microenvironment (TIME) is likely an important determinant of sensitivity to immune checkpoint inhibitor (ICI) treatment. However, a comprehensive analysis covering the complexity and diversity of the TIME and its influence on ICI therapeutic efficacy is still lacking. Data from 782 samples from 10 ICI clinical trials were collected. To infer the infiltration of 22 subsets of immune cells, CIBERSORTx was applied to the bulk tumor transcriptomes. The associations between each cell fraction and the response to ICI treatment, progression-free survival (PFS) and overall survival (OS) were evaluated, modeling cellular proportions as quartiles. Activity of the interferon-γ pathway, the cytolytic activity score and the MHC score were associated with good prognosis in melanoma. Of the immune cells investigated, M1 macrophages, activated memory CD4⁺ T cells, T follicular helper (Tfh) cells and CD8⁺ T cells correlated with response and prolonged PFS and OS, while resting memory CD4⁺ T cells was associated with unfavorable prognosis in melanoma and urothelial cancer. Consensus clustering revealed four immune subgroups with distinct responses to ICI therapy and survival patterns. The cluster with high proportions of infiltrated CD8⁺ T cells, activated memory CD4⁺ T cells, and Tfh cells and low levels of resting memory CD4⁺ T cells exhibited a higher tumor mutation burden and neoantigen load in melanoma and conferred a higher probability of response and improved survival. Local systemic immune cellular differences were associated with outcomes after ICI therapy. Further investigations of the tumor-infiltrating cellular immune response will lay the foundation for achieving durable efficacy.

Clinical Perspectives to Overcome Acquired Resistance to Anti-Programmed Death-1 and Anti-Programmed Death Ligand-1 Therapy in Non-Small Cell Lung Cancer

Immune checkpoint inhibitors have changed the paradigm of treatment options for non-small cell lung cancer (NSCLC). Monoclonal antibodies targeting programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) have gained wide attention for their application, which has been shown to result in prolonged survival. Nevertheless, only a limited subset of patients show partial or complete response to PD-1 therapy, and patients who show a response eventually develop resistance to immunotherapy. This article aims to provide an overview of the mechanisms of acquired resistance to anti-PD-1/PD-L1 therapy from the perspective of tumor cells and the surrounding microenvironment. In addition, we address the potential therapeutic targets and ongoing clinical trials, focusing mainly on NSCLC.

Comprehensive analysis of clinical prognosis and molecular immune characterization of tropomyosin 4 in pancreatic cancer

Pancreatic cancer (PC) is one of the most lethal human solid malignancies with devastating prognosis, making biomarker detection considerably important. Immune infiltrates in microenvironment is associated with patients' survival in PC. The role of Tropomyosin 4 (TPM4) gene in PC has not been reported. Our study first identifies TPM4 expression and its potential biological functions in PC. The potential oncogenic roles of TPM4 was examined using the datasets of TCGA (The cancer genome atlas) and GEO (Gene expression omnibus). We investigated the clinical significance and prognostic value of TPM4 gene based on The Gene Expression Profiling Interactive Analysis (GEPIA) and survival analysis. TIMER and TISIDB databases were used to analyze the correlations between TPM4 gene and tumor-infiltrating immune cells. We found that the expression level of TPM4 was upregulated in PC malignant tissues with the corresponding normal tissues as controls. High TPM4 expression was correlated with the worse clinicopathological features and poor prognosis in PC cohorts. The positive association between TPM4 expression and tumor-infiltrating immune cells was identified in tumor microenvironment (TME). Moreover, functional enrichment analysis suggested that TPM4 might participate in cell adhesion and promote tumor cell migration. This is the first comprehensive study to disclose that TPM4 may serve as a novel prognostic biomarker associating with immune infiltrates and provide a potential therapeutic target for the treatment of PC.

Late Recurrence in Breast Cancer: To Run after the Oxen or to Try to Close the Barn?

Simple Summary

The initial treatment of early breast cancer has achieved important clinical results over time. However, late recurrences after many years of disease-free survival remain an open question, which has recently attracted the attention of a few researchers. The authors of this commentary suggest that the approach emerging from scientific meetings regarding this subject is marred by the lack of attention to recent clinical and laboratory data. The role of tumor dormancy and the dynamics of disease recurrence are presented here and a more general reflection on therapeutic approaches to cancer is proposed.

Abstract

The problem of late recurrence in breast cancer has recently gained attention and was also addressed in an international workshop held in Toronto (ON, Canada), in which several aspects of the question were examined. This Commentary offers a few considerations, which may be useful for the ongoing investigations. A few premises are discussed: (a) clinical recurrences, especially the late ones, imply periods of tumor dormancy; (b) a structured pattern of distant metastases appearance is detectable in both early and late follow-up times; (c) the current general paradigm underlying neoplastic treatments, i.e., that killing all cancer cells is the only way to control the disease, which is strictly sprouting from the somatic mutation theory, should be re-considered. Finally, a few research approaches are suggested.

Nanocarrier-Based Drug Delivery for Melanoma Therapeutics

Melanoma, as a tumor cell derived from melanocyte transformation, has the characteristics of malignant proliferation, high metastasis, rapid recurrence, and a low survival rate. Traditional therapy has many shortcomings, including drug side effects and poor patient compliance, and so on. Therefore, the development of an effective treatment is necessary. Currently, nanotechnologies are a promising oncology treatment strategy because of their ability to effectively deliver drugs and other bioactive molecules to targeted tissues with low toxicity, thereby improving the clinical efficacy of cancer therapy. In this review, the application of nanotechnology in the treatment of melanoma is reviewed and discussed. First, the pathogenesis and molecular targets of melanoma are elucidated, and the current clinical treatment strategies and deficiencies of melanoma are then introduced. Following this, we discuss the main features of developing efficient nanosystems and introduce the latest reports in the literature on nanoparticles for the treatment of melanoma. Subsequently, we review and discuss the application of nanoparticles in chemotherapeutic agents, immunotherapy, mRNA vaccines, and photothermal therapy, as well as the potential of nanotechnology in the early diagnosis of melanoma.

Melanoma Single-Cell Biology in Experimental and Clinical Settings

Cellular heterogeneity is regarded as a major factor for treatment response and resistance in a variety of malignant tumors, including malignant melanoma. More recent developments of single-cell sequencing technology provided deeper insights into this phenomenon. Single-cell data were used to identify prognostic subtypes of melanoma tumors, with a special emphasis on immune cells and fibroblasts in the tumor microenvironment. Moreover, treatment resistance to checkpoint inhibitor therapy has been shown to be associated with a set of differentially expressed immune cell signatures unraveling new targetable intracellular signaling pathways. Characterization of T cell states under checkpoint inhibitor treatment showed that exhausted CD8+ T cell types in melanoma lesions still have a high proliferative index. Other studies identified treatment resistance mechanisms to targeted treatment against the mutated BRAF serine/threonine protein kinase including repression of the melanoma differentiation gene microphthalmia-associated transcription factor (MITF) and induction of AXL receptor tyrosine kinase. Interestingly, treatment resistance mechanisms not only included selection processes of pre-existing subclones but also transition between different states of gene expression. Taken together, single-cell technology has provided deeper insights into melanoma biology and has put forward our understanding of the role of tumor heterogeneity and transcriptional plasticity, which may impact on innovative clinical trial designs and experimental approaches.