Interferon Receptor Signaling Pathways Regulating PD-L1 and PD-L2 Expression

Sigma1 inhibitor suppression of adaptive immune resistance mechanisms mediated by cancer cell derived extracellular vesicles

Adaptive immune resistance in cancer describes the various mechanisms by which tumors adapt to evade anti-tumor immune responses. IFN-γ induction of programmed death-ligand 1 (PD-L1) was the first defined and validated adaptive immune resistance mechanism. The endoplasmic reticulum (ER) is central to adaptive immune resistance as immune modulatory secreted and integral membrane proteins are dependent on ER. Sigma1 is a unique ligand-regulated integral membrane scaffolding protein enriched in the ER of cancer cells. PD-L1 is an integral membrane glycoprotein that is translated into the ER and processed through the cellular secretory pathway. At the cell surface, PD-L1 is an immune checkpoint molecule that binds PD-1 on activated T-cells and blocks anti-tumor immunity. PD-L1 can also be incorporated into cancer cell-derived extracellular vesicles (EVs), and EV-associated PD-L1 can inactivate T-cells within the tumor microenvironment. Here, we demonstrate that a selective small molecule inhibitor of Sigma1 can block IFN-γ mediated adaptive immune resistance in part by altering the incorporation of PD-L1 into cancer cell-derived EVs. Sigma1 inhibition blocked post-translational maturation of PD-L1 downstream of IFN-γ/STAT1 signaling. Subsequently, EVs released in response to IFN-γ stimulation were significantly less potent suppressors of T-cell activation. These results suggest that by reducing tumor derived immune suppressive EVs, Sigma1 inhibition may promote antitumor immunity. Sigma1 modulation presents a novel approach to regulating the tumor immune microenvironment by altering the content and production of EVs. Altogether, these data support the notion that Sigma1 may play a role in adaptive immune resistance in the tumor microenvironment.

Tebentafusp elicits on-target cutaneous immune responses driven by cytotoxic T cells in uveal melanoma patients

BACKGROUNDTebentafusp is the first T cell receptor-based bispecific protein approved for clinical use in HLA-A*02:01+ adult patients with unresectable/metastatic uveal melanoma. It redirects T cells toward gp100-expressing target cells, frequently inducing skin-related early adverse events.METHODSThis study investigated immunological and cellular responses using single-cell and spatial analysis of skin biopsies from patients with metastatic uveal melanoma treated with tebentafusp.RESULTS81.8% of patients developed acute cutaneous adverse events, which correlated with improved survival. Multimodal analysis revealed a brisk infiltration of CD4+ and CD8+ T cells, while melanocyte numbers declined. Single-cell RNA-sequencing revealed T cell activation, proliferation, and IFN-γ/cytotoxic gene upregulation. CD8+ T cells colocalized with melanocytes and upregulated LAG3, suggesting potential for combination therapies with tebentafusp. Melanocytes upregulated antigen presentation and apoptotic pathways, while pigmentation gene expression decreased. However, gp100 remained stably expressed.CONCLUSIONSequential skin biopsies enable in vivo pharmacodynamic modeling of tebentafusp, offering insights into immune activation, toxicity, and treatment response. Examining the on-target effects of bispecifics in tissues amenable to longitudinal sampling enhances our understanding of toxicity and therapeutic escape mechanisms, guiding strategies for treatment optimization.FUNDINGCancer Research Foundation, Swiss National Science Foundation (323630_207029, 733 310030_170320, 310030_188450, CRSII5_183478), Iten-Kohaut Foundation, European Research Council no. 882424, University Priority Project Translational Cancer Research of the University of Zurich (UZH), UZH PostDoc grant (K-85810-02-01).

Early growth response 1 as a key regulator of PD-L1 expression and immune evasion in extranodal NK/T-cell lymphoma

This study investigates the role of Early Growth Response 1 (EGR1) in extranodal natural killer/T-cell lymphoma (ENKTL) and its correlation with PD-L1 expression. Analysis of 62 ENKTL patient samples revealed that high EGR1 expression was linked to PD-L1 positivity, the immune evasion-A subtype, and early-stage disease. Although EGR1 expression was not an independent prognostic factor for overall survival, patients with higher EGR1 levels showed a trend toward better outcomes. In ENKTL cell lines (YT, SNK6), EGR1 positively regulated LMP1 and PD-L1 expression. Knockdown of EGR1 reduced PD-L1 levels, decreased PTEN, increased AKT phosphorylation, and abrogated STAT3 phosphorylation. Conversely, EGR1 overexpression enhanced PD-L1. Treatment with the histone deacetylase inhibitor entinostat upregulated both EGR1 and PD-L1, but this effect was lost in EGR1-depleted cells, indicating EGR1's necessity for HDAC inhibitor-induced PD-L1 expression. These findings reveal EGR1's pivotal role in tumor immune modulation and highlight potential combination therapies targeting EGR1, epigenetic regulators, and PD-1/PD-L1 checkpoints.

Proteomics analysis and immune profiling reveal regulators of PD-L1 in oesophageal squamous cell carcinoma

BACKGROUND

Proteomics studies have advanced our comprehension of cancer biology, accelerated targeted therapy, and improved patient outcomes.

METHODS

High-resolution mass spectrometry and immune profiling based on immunohistochemistry and multiple immunohistochemistry were employed to investigate proteomic and immune landscapes in oesophageal squamous cell carcinoma (ESCC) and explore the regulators of PD-L1 in ESCC. Molecular validation was performed using qRT-PCR, western blotting, and in vitro functional assays.

RESULTS

Proteomic profiling of 89 treatment-naive ESCC specimens identified over 9300 proteins, with 6900 proteins detected across most samples. Proteome-based stratification identified three subtypes related to diverse clinical and molecular features. Combined proteomics and immune analyses revealed core proteins associated with the immune landscape in ESCC. Further, integrated proteomics, transcriptomics, and immune profiling nominated COTL1 as a potential regulator of PD-L1 in ESCC. Overexpression of COTL1 upregulated both mRNA and protein levels of PD-L1 and promoted cell proliferation in ESCC. Patients with high COTL1 protein expression were likely to have a poor prognosis, along with increased infiltration of CD4+CD8+ and CD4+GrB+ cells.

CONCLUSIONS

Collectively, our integrative analysis enables a more comprehensive understanding of the proteomic and immune landscape of ESCC and implicates COTL1 as a potential modulator of PD-L1 and immune cell infiltration.

LMNB2-mediated high PD-L1 transcription triggers the immune escape of hepatocellular carcinoma

While immune checkpoint inhibitors targeting programmed cell death-ligand 1 (PD-L1) demonstrate clinical efficacy in hepatocellular carcinoma (HCC), tumor cells frequently evade immune surveillance through PD-L1 overexpression, a phenomenon whose regulatory mechanisms remain poorly understood. Through integrated analysis of single-cell transcription sequence data, we identified aberrant upregulation of Lamin B2 (LMNB2) specifically in immunotherapy-sensitive HCC patients. Functional characterization revealed that LMNB2 acts as a transcriptional regulator of PD-L1, potentiating immune escape mechanisms in HCC cells during co-culture with Jurkat cells. Notably, we discovered that speckle-type POZ protein (SPOP) directly interacts with LMNB2 to mediate its ubiquitination and proteasomal degradation, thereby maintaining physiological PD-L1 expression levels. Clinically relevant SPOP mutations or reduced SPOP expression impaired this regulatory mechanism, leading to LMNB2 accumulation and subsequent PD-L1 hyperactivation. Importantly, combinatorial targeting of LMNB2 with Atezolizumab (PD-L1 inhibitor) displayed a synergistic effect on suppressing tumor progression both in vitro and in vivo, particularly in HCC models with SPOP mutations or LMNB2 overexpression. These findings unveil a novel ubiquitination-dependent regulatory axis in HCC immune evasion and propose targeted co-inhibition strategies to overcome HCC immunotherapy resistance.

Interferon-Inducible ADAR1 p150 Is Essential for the Survival of Oral Squamous Cell Carcinoma

We identified ADAR1 as one of the top essential genes for oral squamous cell carcinoma (OSCC) survival from our genome-wide CRISPR/Cas9 screen in OSCC cell lines. In this study, we confirm that ADAR1-knockout (KO) inhibits cell viability and colony forming ability, and induces apoptosis. We report that IFN-β treatment sensitizes less-dependent cell lines to ADAR1 KO-induced cell lethality. Overexpression of ADAR1-p150, but not ADAR1-p110, rescued cell lethality upon ADAR1 KO, confirming that the IFN-inducible p150 is responsible for OSCC survival. Using a deaminase inactive mutant, we demonstrate that the editing function of ADAR1 is important for OSCC survival. Furthermore, we show that ADAR1 KO-induced cell death is mediated by both PKR and MDA5. We compute gene signatures of ADAR1 dependency in OSCC tumors, and found that those with high ADAR1 dependency score are associated with well or moderate differentiation, likely due to high PKR expression or activation. While a majority of ADAR1-dependent tumors exhibit a low T cell-inflamed gene expression profile, ADAR1 KO upregulates PD-L1, a marker of anti-PD1 response, indicating that ADAR1 inhibition may enhance immunotherapy response in OSCC. Collectively, these findings suggest that targeting ADAR1-p150 not only induces OSCC cell death but could induce a favorable response to anti-PD1.

Emerging therapeutics targeting tumor-associated macrophages for the treatment of solid organ cancers

INTRODUCTION

Over the last decade, immune checkpoint inhibitors (ICIs) like PD-1/PD-L1 or CTLA-4, which reinvigorate T cells for tumor control have become standard-of-care treatment options. In response to the increasingly recognized mechanisms of resistance to T cell activation in immunologically cold tumors, immuno-oncology drug development has started to shift beyond T cell approaches. These include tumor-associated macrophages (TAMs), a major pro-tumor immune cell population in the tumor microenvironment known to silence immune responses.

AREAS COVERED

Here we outline anti-TAM therapies in current development, either as monotherapy or in combination with other treatment modalities. We describe emerging drugs targeting TAMs under investigation in phase II and III testing with a focus on their distinguishing mechanism of action which include (1) reprogramming of TAMs toward anti-tumor function and immune surveillance, (2) blockade of recruitment, and (3) reduction and ablation of TAMs.

EXPERT OPINION

Several new immuno-oncology agents are under investigation to harness anti-tumor functions of TAMs. While robust anti-tumor efficacy of anti-TAM therapies across advanced solid organ cancers remains elusive to-date, TAM reprogramming therapies have yielded benefits in select cancers. The inherent heterogeneity of the diverse TAM population will require enhanced investments into biomarker-driven approaches to fully leverage its therapeutic potential.

Perspectives of Targeting Autophagy as an Adjuvant to Anti-PD-1/PD-L1 Therapy for Colorectal Cancer Treatment

Colorectal cancer (CRC) is the third most common cancer in the world, with increasing incidence and mortality rates. Standard conventional treatments for CRC are surgery, chemotherapy, and radiotherapy. Recently, immunotherapy has been introduced as a promising alternative to CRC treatment that utilizes patients' immune system to combat cancer cells. The beneficial effect of immune checkpoint inhibitors, specifically anti-PD-1/ PD-L1, has been ascribed to the abundance of DNA replication errors that result in the formation of neoantigens. Such neoantigens serve as distinct flags that amplify the immune response when checkpoint inhibitors (ICIs) are administered. DNA replication errors in CRC patients are expressed as two statuses: the first is the deficient mismatch repair (MSI-H/dMMR) with a higher overall immune response and survival rate than the second status of patients with proficient mismatch repair (MSS/pMMR). There is a limitation to using anti-PD-1/PD-L1 as it is only confined to MSI-H/dMMR, where there is an abundance of T-cell inhibitory ligands (PD-L1). This calls for investigating new therapeutic interventions to widen the scope of ICIs' role in the treatment of CRC. Autophagy modulation provides a good example. Autophagy is a cellular process that plays a crucial role in maintaining cellular homeostasis and has been studied for its impact on tumor development, progression, and response to treatment. In this review, we aim to highlight autophagy as a potential determinant in tumor immune response and to study the impact of autophagy on the tumor immune microenvironment. Moreover, we aim to investigate the value of a combination of anti-PD-1/PD-L1 agents with autophagy modulators as an adjuvant therapeutic approach for CRC treatment.

Programmed Death-1 Ligand 1 Domain Organization, Signaling Motifs, and Interactors in Cancer Immunotherapy

Immunotherapies targeting the programmed cell death-1 ligand 1 (PD-L1) and programmed cell death 1 (PD-1) pathway sparked a revolution in cancer treatment. These breakthrough therapies work by disrupting the interaction between PD-1-expressed on T cells-and its ligand PD-L1, commonly found on the surface of cancer cells. By using monoclonal antibodies to block this binding, the immune system is unleashed to fight cancer more effectively. However, PD-L1's role extends far beyond immune evasion. When situated on cancer cells, PD-L1 transmits inhibitory signals through PD-1, silencing the effector functions of T cells. However, PD-L1 also engages in reverse signaling, also called intrinsic signaling, delivering intracellular instructions that contribute to cancer cell survival, even in the absence of PD-1 binding. This signaling cascade shields cancer cells from apoptosis, drives proliferation, regulates DNA damage responses, and even functions as a co-transcriptional transactivator, amplifying cancer's ability to thrive. The intricate mechanisms behind PD-L1's intrinsic signaling are under intense investigation. In this review, we provide a historical perspective on the discoveries leading to PD-L1's structure, signaling motifs, and interacting partners, shedding light on its multifaceted roles and the promising therapeutic possibilities ahead.

Toll-like receptor 3 activation enhances antitumor immune response in lung adenocarcinoma through NF-κB signaling pathway

Background

Toll-like receptor 3 (TLR3) is a pattern recognition receptor known to play a crucial role in the immune response to cancer. However, its effect on the efficacy of immunotherapy in lung adenocarcinoma (LUAD) remains unclear. This study aims to investigate the role of TLR3 in LUAD by examining its expression levels, prognostic significance, and impact on immune signaling pathways.

Methods

We analyzed the impact of TLR3 expression on the prognosis of lung adenocarcinoma patients using data from the Cancer Genome Atlas (TCGA) database and four additional cohorts (GSE72094, GSE30219, GSE50081 and GSE31210). Functional enrichment analyses were performed to compare molecular features between low and high TLR3 expression groups using gene set variation analysis (GSVA). We also examined the correlation between TLR3 and tumor mutation burden (TMB), immune infiltration, and PD-L1 expression. Further experimental validation was conducted using co-culture systems of LUAD cells and peripheral blood mononuclear cells (PBMCs) with PD1 inhibitors, and Western blot analysis to investigate the involvement of NF-κB signaling.

Results

TLR3 expression was significantly lower in LUAD tissues compared to normal tissues, with high TLR3 expression correlating with better survival outcomes across multiple cohorts. High TLR3 expression was associated with increased TMB and enhanced immune activation. Patients with high TLR3 expression exhibited higher immune checkpoint expression and immune cell infiltration. Experimental results showed that TLR3 agonists increased the susceptibility of LUAD cells to activated PBMCs under PD1 inhibitor therapy, inhibiting cell proliferation, migration, and invasion. Additionally, TLR3 has a strong positive correlation with MHC molecules and upregulated PD-L1 expression. NF-κB was identified as a key regulator of PD-L1 expression, with TLR3 agonists enhancing NF-κB and PD-L1 activity.

Conclusion

TLR3 enhances the anti-tumor immune response in LUAD by modulating NF-κB signaling and PD-L1 expression, making it a promising prognostic biomarker and therapeutic target. This study highlights the potential of TLR3 to improve immunotherapy outcomes, providing a comprehensive analysis of its role in LUAD and paving the way for novel therapeutic strategies targeting TLR3-mediated pathways.

The JAK2 46/1 haplotype influences PD-L1 expression

ABSTRACT

Although described more than a decade ago, the mechanism by which the JAK2 46/1 haplotype increases the risk of developing JAK2-mutated myeloproliferative neoplasms (MPNs) remains unexplained. Inflammation and immunity are linked to MPN development and thus could be relevant to the mechanism by which 46/1 mediates its effect. Here, we show that programmed death-1 receptor ligand (PD-L1) expression is elevated in 46/1 haplotype, both in healthy carriers and in CD34+ cells from patients with MPN. Using circular chromosome conformation capture, we observed that PD-L1 and the neighboring PD-L2 loci physically interact with JAK2 in a manner that differs between 46/1 and nonrisk haplotypes. CRISPR/Cas9 genome editing identified a region within JAK2 intron 2 that influences both JAK2 and PD-L1 expression. We suggest that increased PD-L1 expression may be relevant to the mechanism by which 46/1 leads to an increased inherited risk of developing MPN.

Tumor microenvironment-associated oxidative stress impairs SIRT1 secretion to suppress anti-tumor immune response

Sirtuin-1 (SIRT1) is a classical histone deacetylase well known for its roles in intracellular pathways such as energy metabolism, DNA damage response, and genome stability maintenance. We report that SIRT1 can be secreted into the tumor microenvironment (TME) through an unconventional protein secretion pathway, effectively inhibiting tumor growth. However, under the stressful conditions of the TME, SIRT1 undergoes increased methylation, which impedes its secretion. Consequently, tumor-infiltrating M2 macrophages are unable to acquire sufficient SIRT1 from the TME, resulting in a significant decrease in SIRT1 levels within these cells. This SIRT1 decline leads to elevated expression of programmed cell death ligand 1 (PD-L1) on M2 macrophages, which in turn contributes to CD8+ T cell exhaustion through the programmed cell death protein 1/PD-L1 interaction pathway. These findings unveil the multifaceted roles and regulatory mechanisms of SIRT1 within the complex TME, providing deeper insights that significantly enhance our understanding of tumor immune-evasion strategies.

Targeting immune checkpoints in hepatocellular carcinoma therapy: toward combination strategies with curative potential

Hepatocellular carcinoma (HCC) is a primary liver cancer characterized by poor immune cell infiltration and a strongly immunosuppressive microenvironment. Traditional treatments have often yielded unsatisfactory outcomes due to the insidious onset of the disease. Encouragingly, the introduction of immune checkpoint inhibitors (ICIs) has significantly transformed the approach to HCC treatment. Moreover, combining ICIs with other therapies or novel materials is considered the most promising opportunity in HCC, with some of these combinations already being evaluated in large-scale clinical trials. Unfortunately, most clinical trials fail to meet their endpoints, and the few successful ones also face challenges. This indicates that the potential of ICIs in HCC treatment remains underutilized, prompting a reevaluation of this promising therapy. Therefore, this article provides a review of the role of immune checkpoints in cancer treatment, the research progress of ICIs and their combination application in the treatment of HCC, aiming to open up avenues for the development of safer and more efficient immune checkpoint-related strategies for HCC treatment.

Exploring immune checkpoint inhibitors: Focus on PD-1/PD-L1 axis and beyond

Immunotherapy emerges as a promising approach, marked by recent substantial progress in elucidating how the host immune response impacts tumor development and its sensitivity to various treatments. Immune checkpoint inhibitors have revolutionized cancer therapy by unleashing the power of the immune system to recognize and eradicate tumor cells. Among these, inhibitors targeting the programmed cell death protein 1 (PD-1) and its ligand (PD-L1) have garnered significant attention due to their remarkable clinical efficacy across various malignancies. This review delves into the mechanisms of action, clinical applications, and emerging therapeutic strategies surrounding PD-1/PD-L1 blockade. We explore the intricate interactions between PD-1/PD-L1 and other immune checkpoints, shedding light on combinatorial approaches to enhance treatment outcomes and overcome resistance mechanisms. Furthermore, we discuss the expanding landscape of immune checkpoint inhibitors beyond PD-1/PD-L1, including novel targets such as CTLA-4, LAG-3, TIM-3, and TIGIT. Through a comprehensive analysis of preclinical and clinical studies, we highlight the promise and challenges of immune checkpoint blockade in cancer immunotherapy, paving the way for future advancements in the field.

High-accuracy Detection of PD-L1 3'-UTR Disruption by Immunohistochemistry and Fluorescence in Situ Hybridization on Formalin-fixed Paraffin-embedded Sections

Programmed death-ligand 1 (PD-L1/CD274) structural variation (SV) disrupting the 3'-untranslated region has been highlighted as being associated with PD-L1 overexpression. In the present study, we evaluated lymphoma tissue samples to investigate the applicability of immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) for detecting the PD-L1 SV involving the 3'-untranslated region. In total, 1052 lymphoma samples were screened using IHC, and 99 IHC screening-positive samples were evaluated with FISH (non-Hodgkin lymphoma [NHL, n=58] and Hodgkin lymphoma [HL, n=41]). Of these, 92 samples showed strong PD-L1 expression with 2 PD-L1 antibodies (E1J2J and SP142) (concordant PD-L1 IHC), whereas 7 samples showed strong PD-L1 expression only with E1J2J (discordant PD-L1 IHC). Abnormal FISH findings for PD-L1 were detected in all evaluated samples (51 NHLs and 41 HLs). A structural abnormality pattern was observed in 17 of the 51 evaluated NHL samples (33%). In contrast, all 41 HL samples showed a copy number abnormality pattern, with 1 exhibiting a structural abnormality pattern. Target-capture sequencing of the PD-L1 gene was performed on 73 of the 99 IHC screening-positive samples, comprising 41 NHLs and 32 HLs. PD-L1 SVs were detected in 16 (39%) of the 41 NHL samples and in only one of the 32 HL samples (3%). Samples exhibiting discordant PD-L1 IHC and/or FISH structural abnormality patterns were shown to harbor PD-L1 SV by target-capture sequencing, with positive and negative predictive values of 94% and 96%, respectively. Our approach is an alternative to target-capture sequencing for evaluating PD-L1 gene abnormalities.

AGO2 mediates immunotherapy failure via suppressing tumor IFN-gamma response-dependent CD8+ T cell immunity

Interferon-gamma (IFN-γ), a cytokine essential for activating cellular immune responses, plays a crucial role in cancer immunosurveillance and the clinical success of immune checkpoint blockade therapy. In this study, we show that Argonaute 2 (AGO2), a key mediator in small RNA-guided gene regulation, inversely correlates with tumor responsiveness to IFN-γ and the efficacy of immunotherapy. Mechanistically, IFN-γ upregulates miR-1246 expression in tumor cells, enhancing its interaction with AGO2. This miR-1246-AGO2 complex disrupts IFN-γ-mediated signal transducer and activator of transcription 1 (STAT1) phosphorylation by stabilizing protein tyrosine phosphatase non-receptor 6 (PTPN6) mRNA, thereby suppressing the expression of downstream C-X-C motif chemokine ligands (CXCLs), IFN-stimulated genes (ISGs), and human leukocyte antigen (HLA) molecules, which collectively contribute to tumor immune evasion. In preclinical cancer models, inhibiting AGO2 with BCI-137 or targeting miR-1246 with its antagomir re-sensitizes tumor cells to IFN-γ, leading to the enhanced recruitment, activation, and cytotoxicity of CD8+ T cells and ultimately improving immunotherapy efficacy.

Immunohistochemical expression of PD-L1 in colorectal carcinoma among black patients and the clinicopathological correlates: a cross-sectional study

BACKGROUND

Colorectal cancer (CRC) incidence is rising in Nigeria, with majority of patients presenting with advanced disease. Despite promising results of PD-L1 antibody therapy in clinical trials, efficacy data exclusively derives from Caucasian populations, leaving a critical knowledge gap for African populations. This study investigated PD-L1 expression in CRC among blacks, correlating it with clinicopathologic parameters.

METHODS

The immunohistochemical expression of PD-L1 was evaluated in 96 cases of CRC diagnosed between February 2022 and January 2024, using formalin-fixed paraffin-embedded (FFPE) tissue blocks. Statistical analysis was performed using SPSS version 25. The relationships between the PD-L1 expression and the clinicopathological parameters of CRC patients were determined using the chi-square test and Spearman's rank correlation. p < 0.05 was considered to be statistically significant.

RESULTS

CRC showed a male: female ratio of 1:1.8, most occurred in the seventh decade and 54.17% were right-sided. Adenocarcinoma NOS accounted for 72.5%. The majority (n = 55, 57.3%) of the patients were diagnosed at an advanced stage. PD-L1 expression was observed in 86.46% of cases, significantly correlating with tumour Size (r = 0.263, p = 0.010*), histologic Grade (r = 0.446, p = 0.000*) and tumour Stage (r = 0.367, p = 0.000*).

CONCLUSION

This study highlighted the high frequency of PD-L1 expression in CRC among black patients, with significant associations to clinicopathologic parameters. The findings suggest the potential benefit of PD-1/PD-L1 targeted therapies and emphasize the need for enhanced early detection and screening in Nigeria.

Immunocytes in the tumor microenvironment: recent updates and interconnections

The tumor microenvironment (TME) is a complex, dynamic ecosystem where tumor cells interact with diverse immune and stromal cell types. This review provides an overview of the TME's evolving composition, emphasizing its transition from an early pro-inflammatory, immune-promoting state to a later immunosuppressive milieu characterized by metabolic reprogramming and hypoxia. It highlights the dual roles of key immunocytes-including T lymphocytes, natural killer cells, macrophages, dendritic cells, and myeloid-derived suppressor cells-which can either inhibit or support tumor progression based on their phenotypic polarization and local metabolic conditions. The article further elucidates mechanisms of immune cell plasticity, such as the M1/M2 macrophage switch and the balance between effector T cells and regulatory T cells, underscoring their impact on tumor growth and metastasis. Additionally, emerging therapeutic strategies, including checkpoint inhibitors and chimeric antigen receptor (CAR) T and NK cell therapies, as well as approaches targeting metabolic pathways, are discussed as promising avenues to reinvigorate antitumor immunity. By integrating recent molecular insights and clinical advancements, the review underscores the importance of deciphering the interplay between immunocytes and the TME to develop more effective cancer immunotherapies.

Gut microbiota affects PD-L1 therapy and its mechanism in melanoma

Immune checkpoint inhibitors (ICIs), particularly PD-1/PD-L1 blockade, have shown great success in treating melanoma. PD-L1 (B7-H1, CD274), a ligand of PD-1, binds to PD-1 on T cells, inhibiting their activation and proliferation through multiple pathways, thus dampening tumor-reactive T cell activity. Studies have linked PD-L1 expression in melanoma with tumor growth, invasion, and metastasis, making the PD-1/PD-L1 pathway a critical target in melanoma therapy. However, immune-related adverse events are common, reducing the effectiveness of anti-PD-L1 treatments. Recent evidence suggests that the gut microbiome significantly influences anti-tumor immunity, with the microbiome potentially reprogramming the tumor microenvironment and overcoming resistance to anti-PD-1 therapies in melanoma patients. This review explores the mechanisms of PD-1/PD-L1 in melanoma and examines how gut microbiota and its metabolites may help address resistance to anti-PD-1 therapy, offering new insights for improving melanoma treatment strategies.

Identification of Dinaciclib and Ganetespib as anti-inflammatory drugs using a novel HTP screening assay that targets IFNγ-dependent PD-L1

Introduction

IFNγ plays both positive and negative roles in the regulation of innate and adaptive immune responses against tumors and virally infected tissues by upregulating CXCL10 and PD-L1 expression.

Methods

To identify novel pathways and drugs that regulate the IFNγ-dependent PD-L1, we expressed GFP under the control of mouse PD-L1 promoter in mouse cancer cells that up regulate PD-L1 and CXCL10 in response to IFNγ stimulation. Using these cells, we screened an FDA approved library of 1496 small molecules known for their ability to inhibit IFNγ-dependent increase in PD-L1.

Results

We identified 46 drugs that up regulated and 4 that down regulated IFNγ-dependent PD-L1 expression. We discovered that in addition to the known JAK inhibitors Ruxolitinib and Baricitinib, Dinaciclib, a CDK1/2/5/9 inhibitor, and Ganetespib, a Hsp90 inhibitor, significantly inhibit both PD-L1 and CXCL10 expression in the model cells. Furthermore, both drugs suppressed IFNγ-dependent CXCL10 and PD-L1 expression in-vitro in primary human lung cells and human cancer cells. These drugs also significantly inhibited delayed-type hypersensitivity (DTH) in-vivo in an inflammation mouse model.

Discussion

Our novel screening platform can therefore be used in the future to identify novel immunomodulators and pathways in cancer and inflammation, expanding therapeutic horizons.

Type I IFNs contribute to upregulation of PD-L1 during Chlamydia trachomatis infection

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that if left untreated can cause reproductive harm. Failure of natural adaptive immunity results in chronic and repeat infections. In efforts to understand the failure of adaptive immunity, we have previously discovered that CD8+ T cells, normally integral for controlling intracellular pathogen infections, are misprogrammed by PD-1/PD-L1 signaling during in vivo C. trachomatis infection and fail to mount a protective response. Seeking to uncover the pathways and host factors involved in PD-L1 upregulation that may lead to CD8+ T-cell inhibition, we discovered that C. trachomatis triggers the secretion of host type I interferons (IFNs) that are necessary and sufficient to upregulate PD-L1 in vitro. Additionally, secretion of type I IFNs is dependent on C. trachomatis development and its type III secretion system. We have also validated that type I IFNs contribute to upregulation of PD-L1 during C. trachomatis infection in vivo using a mouse model of infection. Overall, these findings reveal that C. trachomatis induction of this host pathway may contribute to adaptive immune evasion.

The potential role of PD-1/PD-L1 small molecule inhibitors in colorectal cancer with different mechanisms of action

Colorectal cancer (CRC) remains one of the leading causes of cancer-related death worldwide, with increasing incidence in younger ages highlighting the need for new or alternative therapy, of which is immune checkpoint inhibitors. Antibody-based immune checkpoint inhibitors targeting the interaction between programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) have revolutionized cancer treatment, including CRC. However, the low response rate in CRC highlights the need for additional research and innovative therapies. Small molecule inhibitors have risen as another strategy worth exploring, considering their potential to target a wide array of PD-1/PD-L1-related pathways. This review focuses on the potential of small molecule inhibitors targeting the PD-1/PD-L1 axis in CRC. Exploring various classes of small molecule inhibitors, including those that directly block the PD-1/PD-L1 interaction and others that target upstream regulators or downstream signaling pathways involved in PD-1/PD-L1-mediated immune suppression. Additionally, modulation of post-transcriptional and post-translational processes, thereby influencing the expression, stability, or localization of PD-1/PD-L1 proteins to enhance antitumor immunity, provides a multifaceted treatment approach. By disrupting these pathways, these inhibitors can restore immune system activity against tumor cells, offering new hope for overcoming resistance and improving outcomes in CRC patients who do not respond to conventional immune checkpoint inhibitors (ICIs). Integrating these small molecules into CRC treatment strategies could represent a promising advancement in the battle against the challenging disease.

Abscopal Effects and Immunomodulation in Skin Cancer Therapy

Radiation therapy (RT) is a crucial modality in cancer treatment, functioning through direct DNA damage and immune stimulation. However, RT's effects extend beyond targeted cells, influencing neighboring cells through the bystander effect (ByE) and distant sites via the abscopal effect (AbE). The AbE, first described by Mole in 1953, encompasses biological reactions at sites distant from the irradiation field. While RT can enhance antitumor immune responses, it may also contribute to an immunosuppressive microenvironment. To address this limitation, combining RT with immune checkpoint inhibitors (ICIs) has gained renewed interest, aiming to amplify antitumor immune responses. Evidence of AbEs has been observed in various metastatic or advanced cutaneous cancers, including melanoma, basal cell carcinoma, cutaneous lymphoma, Merkel cell carcinoma, and cutaneous squamous cell carcinoma. Clinical studies suggest combining RT with ICIs targeting CTLA-4 and PD-1/PD-L1 may enhance AbE incidence in these cancers. This review primarily explores the current understanding of AbEs in skin cancers, briefly acknowledging the ByE focusing on combining RT with immunomodulation. It focuses on proposed mechanisms, preclinical and clinical evidence, challenges in clinical translation, and future directions for harnessing AbEs in managing advanced skin malignancies. Alternative modalities for inducing abscopal-like responses are also explored. While promising, challenges remain in consistently reproducing AbEs in clinical practice, necessitating further research to optimize treatment combinations, timing, and patient selection.

The covalent modification of STAT1 cysteines by sulforaphane promotes antitumor immunity via blocking IFN-γ-induced PD-L1 expression

Sulforaphane (SFN), a natural compound found in cruciferous vegetables, possesses well-documented antitumor properties. However, the precise functions and mechanisms of SFN in cancer suppression remain poorly understood. Here we provide evidence to demonstrate that SFN exerts more pronounced antitumor effects in immunocompetent mice compared to immunodeficient mice, suggesting the involvement of the host immune system in SFN-mediated tumor suppression. Furthermore, we reveal that SFN primarily acts through CD8+ cytotoxic T lymphocytes (CTLs) to enhance antitumor immunity by blocking the IFN-γ-mediated induction of PD-L1, a critical immune checkpoint receptor expressed in cancer cells. Importantly, our findings indicate that the suppression of PD-L1 expression by SFN is independent of the NRF2 protein stabilization pathway. Instead, SFN inhibits IFN-γ-mediated activation of STAT1, a key transcription factor involved in PD-L1 induction. Mechanistically, SFN covalently modifies specific cysteine residues (C155 and C174) on STAT1, resulting in the inhibition of its transcriptional activity. Notably, SFN-mediated downregulation of PD-L1 contributes to its antitumor immune effects, as demonstrated by enhanced anti-CTLA-4-mediated cytotoxicity. These findings indicate that SFN's antitumor effect extends beyond its direct cytotoxic properties, as it also actively engages the host immune system. This underscores SFN's immense potential as an immune-modulating agent in cancer therapy.

Mevalonate kinase inhibits anti-tumor immunity by impairing the tumor cell-intrinsic interferon response in microsatellite instability colorectal cancer

Insufficient tumor cell-intrinsic interferon response represents a major obstacle in immune checkpoint blockade (ICB) therapy, particularly in anti-PD-1 treatment. Although cholesterol metabolism has been demonstrated to be a critical regulator of anti-tumor immune responses, whether cholesterol influences tumor cell-intrinsic interferon response in microsatellite instability (MSI) colorectal cancer (CRC) remains unknown. Through comprehensive siRNA library screening and Gene Set Enrichment Analysis (GSEA), we identified mevalonate kinase (MVK) as a crucial negative regulator of tumor cell-intrinsic interferon response in MSI CRC cells. Genetic ablation of MVK resulted in significant upregulation of Th1 type chemokines (CXCL9 and CXCL10) and enhanced CD8+T cell infiltration in MSI CRC, consequently leading to marked tumor growth suppression in immunocompetent mice. At the molecular level, we demonstrated that MVK physically interacts with the transcriptional activation domain (TAD) of signal transducer and activator of transcription 1 (STAT1). This interaction substantially impairs STAT1 nuclear translocation, thereby attenuating interferon signaling cascade. Furthermore, analyses of humanized PBMC-PDX models and clinical cohorts of MSI CRC patients revealed that reduced MVK expression in tumor tissues strongly correlates with favorable responses to anti-PD-1 therapy. Collectively, our findings establish MVK as a pivotal mediator in cholesterol synthesis pathway that negatively regulates tumor cell-intrinsic interferon response in MSI CRC. These results suggest that therapeutic targeting of MVK represents a promising strategy to enhance ICB efficacy through potentiation of interferon responses in MSI CRC patients.

Transcriptomic signatures in peripheral CD4+T-lymphocytes may reflect melanoma staging and immunotherapy responsiveness prior to ICI initiation

Background and purpose

Promoting adaptive immunity with ICIs has drastically improved melanoma prognosis, but not for all patients. Some cases relapse in the first few months, while others keep durable benefit, even after immunotherapy discontinuation. To identify cellular/molecular signatures in peripheral blood that could differentiate advanced from metastatic melanoma and predict dynamics for primary/secondary immune escape, we examined 100 consecutive patients with stage III/IV melanoma scheduled to start ICIs.

Materials and methods

At melanoma diagnosis, a multiparameter flow cytometric analysis and purification scheme using standard conjugated antibodies were performed for all individuals prior to ICI initiation. In each stage(III/IV) according to their RFS/PFS, we retrospectively selected the cases with the clearest clinical outcomes and focused our analysis on the extreme responders(n=7) and non-responders(n=7) to characterize the transcriptomes of circulating CD4+T-cells by bulk RNA-seq, Differential Expression Analysis(DEA)and Gene Ontology(GO)enrichment analysis. Based on our selected patient cohort, we examined for differentially expressed genes(DEGs)and key-pathways that appear preferentially activated in stage III vs. IV melanoma, and in long vs. short immunotherapy responders.

Results

Although circulating immune-cells did not numerically differ in both sets of analysis(staging and ICI responsiveness), DEA and GO data showed that patients could be clustered separately, identifying 189vs.92 DEGs in stage IV/III and 101vs.47 DEGs in early progressors/long responders. These DEGs were functionally implicated in distinct pathways. For metastatic cases: inflammatory response(logp-value=-9.2:ADGRE5/2,CYBA,GRN,HMOX1,IRF5,ITGAM), adaptive immunity(logp-value=-7.7:CD1C,CD74,CYBB,NCF2,CTSA,S100A8/9,BCL3,FCER1G), T-cell activation(logp-value=-6.3:BCL3,CD1C,CD74,FCER1G,FGL2)and lipid metabolism/catabolism(logp-value=-2.5/-2.6:ARF3,GPX1,MVD,OCRL,PCCB,CTSA,PNPLA2,NAGLU,GBA2,ABHD4); while in early-progressors to ICIs: immune effector processing(logp-value=-13.7:BCL6,FGR,HLA-DQA1/DQB1,HLA-DRA,HLA-DRB1/DRB5,NKG7,SLC11A1,TYROBP,SPON2,HAVCR2),PD-1(logp-value=-10.2:HLA-DQA1/DQB1,HLA-DRA,HLA-DRB1/DRB5)and IFN signaling(logp-value=-8.5: HLA-DQA1/DQB1,HLA-DRA,HLA-DRB1/DRB5,NCAM1,IFITM3),positive regulation of T-cell activation(logp-value=-7.7:BCL6,HLA-DQA1/DQB1,HLA-DRA,HLA-DRB1/DRB5,SASH3,HAVCR2)and CD28 co-stimulation(logp-value=-10.3:HLA-DQA1/DQB1,HLA-DRA,HLA-DRB1/DRB5), supporting an immune-mediated behavior.

Conclusions

Specific pathways and marker genes in the peripheral CD4+T-cells may predetermine melanoma staging and immunotherapy resistance.

Evaluating comparative effectiveness of pembrolizumab-based therapy versus chemotherapy in treatment of gastric carcinoma: a systematic review and meta-analysis of randomized controlled trials

Gastric cancer, especially cancer of the gastro-esophageal junction, ranks among the first five cancers in the world with the highest mortality rates. It has poor survival rates for the advanced stages. Traditional chemotherapy, while standard, often results in significant side effects and limited efficacy. The objective of this meta-analysis and systemic review is to ascertain if pembrolizumab-based therapies for advanced gastric cancer are more effective and safer than standard chemotherapy. The focus consisted of RCTs with adults suffering from gastric carcinoma who received pembrolizumab every 3 weeks (200 mg) intra-related dose or with at least comparable chemotherapy regimen. Outcomes assessed are as follows: overall survival (OS), progression-free survival (PFS), and objective response rate (ORR). All potential sources regarding the search of outcome measures were applied: Google Scholar, Scopus, PubMed, and Cochrane library, and last search in June 2024 was carried out. Out of 568 articles screened, four RCTs comprising 2,831 patients met the inclusion criteria. Analysis indicated that pembrolizumab alone did not significantly improve OS compared to chemotherapy (HR 0.87). However, when combined with chemotherapy, pembrolizumab dramatically enhanced OS (HR 0.80) and PFS (HR 0.78). ORR was superior in the pembrolizumab plus chemotherapy group (RR 1.24), while pembrolizumab monotherapy showed no significant difference from chemotherapy alone. Safety analysis revealed a higher frequency of adverse events in the pembrolizumab-based therapy groups compared to chemotherapy. Pembrolizumab together with chemotherapy improves greater survival and higher levels of response rate in patients with severe gastric cancer, especially with high PD-L1 expression. But it has rather more adverse events, allowing patient monitoring with care.

Orlistat facilitates immunotherapy via AKT-FOXO3a-FOXM1-mediated PD-L1 suppression

BACKGROUND

The immunotherapy targeting cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death ligand-1 (PD-L1) has achieved significant breakthroughs, but further improvements are still needed in cancer treatment.

METHODS

We investigated orlistat, a drug approved by the Food and Drug Administration for the treatment of obesity and found that it can enhance the efficacy of CTLA-4 blockade immunotherapy. We conducted both in vivo and in vitro experiments to explore the mechanism by which orlistat increased antitumor immunity.

RESULTS

Orlistat enhances the efficacy of anti-CTLA-4 immunotherapy by suppressing tumor cell PD-L1 protein expression and boosting the transcription of interferon-stimulated genes (ISGs) and MHC-I. Mechanistically, orlistat inhibits AKT activity and subsequent phosphorylation of forkhead box O3a (FOXO3a) at its threonine (T) 32, serine (S) 253, thereby downregulating Forkhead box M1 (FOXM1) expression, which ultimately suppresses PD-L1 transcription. Specifically, inhibition of FOXM1 leads to FOXO3a accumulation through impaired AKT activity. FOXM1 activates protein kinase B (AKT) via acting as a scaffold to facilitate 3-phosphoinositide-dependent protein kinase 1 (PDK1) and AKT and interaction. In addition, orlistat enhances phosphorylated signal transducer and activator of transcription 1 (p-STAT1) at tyrosine (Y) 701, resulting in upregulation of ISGs and MHC-I.

CONCLUSIONS

Orlistat plays a crucial role in modulating the immune response and supporting the combination with CTLA-4 blockade to promote antitumor immunotherapy.

Modulation of the tumor immune microenvironment by Interferon Regulatory Factor 8 enhances immunotherapy in lung adenocarcinoma

Interferon regulatory factors (IRFs) are integral in governing the expression of Type I interferon (IFN) genes. However, the precise role of IRFs in lung adenocarcinoma remains elusive. Our objective is to elucidate the prognostic implications of IRFs and their potential influence on the immunotherapeutic response in patients with lung adenocarcinoma (LUAD). The association between IRFs expression and clinical as well as prognostic features was evaluated utilizing the TCGA database. Prognostic determinants for LUAD were pinpointed via univariate and multivariate analyses. Nomogram to evaluate prognosis predicated on IRF expression levels. Gene enrichments were conducted to elucidate the mechanisms of action. The degree of immune infiltration was using bioinformatics methods and was validated through a single-cell dataset. We compiled our unique cohort of LUAD patients who underwent anti-PD-1 therapy for subsequent immunohistochemistry and multicolor immunofluorescence staining to gauge the conclusion above. Our findings revealed that IRF8 serves as an independent risk factor for overall survival (OS) in patients with LUAD. An analysis of patients undergoing immunotherapy revealed a positive association between the expression of IRF8 and the response to the treatment. In our specific cohort treated with anti-PD-1, high IRF8 expression was observed to enhance immunotherapy response and prolong OS by modulating immune cell infiltration. Our retrospective analysis suggests that elevated IRF8 expression correlates with improved prognosis in LUAD, with higher IRF8 expression being predictive of a more robust immunotherapy response. Mechanistically, IRF8 expression is associated with a modulated tumor immune microenvironment and improved immunotherapeutic response.

Dual role of interferon-gamma in the response of melanoma patients to immunotherapy with immune checkpoint inhibitors

Interferon-gamma (IFN-γ) is a cytokine produced mainly by immune cells and can affect cancer cells by modulating the activity of multiple signaling pathways, including the canonical Janus-activated kinase/signal transducer and activator of transcription (JAK/STAT) cascade. In melanoma, IFN-γ can exert both anticancer effects associated with cell-cycle arrest and cell death induction and protumorigenic activity related to immune evasion leading to melanoma progression. Notably, IFN-γ plays a crucial role in the response of melanoma patients to immunotherapy with immune checkpoint inhibitors (ICIs), which are currently used in the clinic. As these agents target programmed death-1 (PD-1) and its ligand (PD-L1), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) and lymphocyte-activation gene 3 (LAG-3), they are designed to restore the antimelanoma immune response. In this respect, IFN-γ produced by cells in the tumor microenvironment in response to ICIs has a beneficial influence on both immune and melanoma cells by increasing antigen presentation, recruiting additional T-cells to the tumor site, and inducing direct antiproliferative effects and apoptosis in melanoma cells. Therefore, IFN-γ itself and IFN-γ-related gene signatures during the response to ICIs can constitute biomarkers or predictors of the clinical outcome of melanoma patients treated with ICIs. However, owing to its multifaceted roles, IFN-γ can also contribute to developing mechanisms associated with the acquisition of resistance to ICIs. These mechanisms can be associated with either decreased IFN-γ levels in the tumor microenvironment or diminished responsiveness to IFN-γ due to changes in the melanoma phenotypes associated with affected activity of other signaling pathways or genetic alterations e.g., in JAK, which restricts the ability of melanoma cells to respond to IFN-γ. In this respect, the influence of IFN-γ on melanoma-specific regulators of the dynamic plasticity of the cell phenotype, including microphthalmia-associated transcription factor (MITF) and nerve growth factor receptor (NGFR)/CD271 can affect the clinical efficacy of ICIs. This review comprehensively discusses the role of IFN-γ in the response of melanoma patients to ICIs with respect to its positive influence and role in IFN-γ-related mechanisms of resistance to ICIs as well as the potential use of predictive markers on the basis of IFN-γ levels and signatures of IFN-γ-dependent genes.

Massively parallel interrogation of human functional variants modulating cancer immunosurveillance

Anti-PD-1/PD-L1 immune checkpoint blockade (ICB) therapy has revolutionized clinical cancer treatment, while abnormal PD-L1 or HLA-I expression in patients can significantly impact the therapeutic efficacy. Somatic mutations in cancer cells that modulate these critical regulators are closely associated with tumor progression and ICB response. However, a systematic interpretation of cancer immune-related mutations is still lacking. Here, we harnessed the ABEmax system to establish a large-scale sgRNA library encompassing approximately 820,000 sgRNAs that target all feasible serine/threonine/tyrosine residues across the human genome, which systematically unveiled thousands of novel mutations that decrease or augment PD-L1 or HLA-I expression. Beyond residues associated with phosphorylation events, our screens also identified functional mutations that affect mRNA or protein stability, DNA binding capacity, protein-protein interactions, and enzymatic catalytic activity, leading to either gene inactivation or activation. Notably, we uncovered certain mutations that concurrently modulate PD-L1 and HLA-I expression, represented by the clinically relevant mutation SETD2_Y1666. We demonstrated that this mutation induces consistent phenotypic effects across multiple cancer cell lines and enhances the efficacy of immunotherapy in different tumor models. Our findings provide an unprecedented resource of functional residues that regulate cancer immunosurveillance, offering valuable guidance for clinical diagnosis, ICB therapy, and the development of innovative drugs for cancer treatment.

Interferon-γ-stimulated antigen-presenting cancer-associated fibroblasts hinder neoadjuvant chemoimmunotherapy efficacy in lung cancer

Conventional neoadjuvant chemotherapy provides limited benefit for patients with resectable non-small cell lung cancer (NSCLC). Recently, neoadjuvant chemoimmunotherapy (NCIT) has transformed the perioperative management of NSCLC by priming systemic anti-tumor immunity before surgery, yet it remains ineffective for at least 50% of patients. Through single-cell sequencing analysis of our NCIT cohort, we identify that antigen-presenting cancer-associated fibroblasts (apCAFs) can impede the efficacy of NCIT. Using a custom cancer-associated fibroblast biobank, we uncover that interferon (IFN)-γ stimulates apCAF expansion via the JAK1/2-STAT1-IFI6/27 pathway. Mechanistically, apCAFs significantly contribute to PD-L2 expression in the tumor microenvironment (TME), triggering the accumulation of FOXP1+regulatory T cells (Tregs) through the PD-L2-RGMB axis. Reprogramming apCAFs by inhibiting the IFN-γ pathway or blocking the PD-L2-RGMB axis substantially mitigates apCAFs-mediated FOXP1+Tregs' expansion. In summary, we reveal the role of apCAFs in compromising NCIT efficacy and propose applications for anti-PD-L2/RGMB regimens to synergize with anti-PD1 therapies by targeting apCAFs.

Activating antiviral immune responses potentiates immune checkpoint inhibition in glioblastoma models

Viral mimicry refers to the activation of innate antiviral immune responses due to the induction of endogenous retroelements (REs). Viral mimicry augments antitumor immune responses and sensitizes solid tumors to immunotherapy. Here, we found that targeting what we believe to be a novel, master epigenetic regulator, Zinc Finger Protein 638 (ZNF638), induces viral mimicry in glioblastoma (GBM) preclinical models and potentiates immune checkpoint inhibition (ICI). ZNF638 recruits the HUSH complex, which precipitates repressive H3K9me3 marks on endogenous REs. In GBM, ZNF638 is associated with marked locoregional immunosuppressive transcriptional signatures, reduced endogenous RE expression, and poor immune cell infiltration. Targeting ZNF638 decreased H3K9 trimethylation, increased REs, and activated intracellular dsRNA signaling cascades. Furthermore, ZNF638 knockdown upregulated antiviral immune programs and significantly increased PD-L1 immune checkpoint expression in diverse GBM models. Importantly, targeting ZNF638 sensitized mice to ICI in syngeneic murine orthotopic models through innate IFN signaling. This response was recapitulated in recurrent GBM (rGBM) samples with radiographic responses to checkpoint inhibition with widely increased expression of dsRNA, PD-L1, and perivascular CD8 cell infiltration, suggesting that dsRNA signaling may mediate response to immunotherapy. Finally, low ZNF638 expression was a biomarker of clinical response to ICI and improved survival in patients with rGBM and patients with melanoma. Our findings suggest that ZNF638 could serve as a target to potentiate immunotherapy in gliomas.

PRMT3 drives PD-L1-mediated immune escape through activating PDHK1-regulated glycolysis in hepatocellular carcinoma

Aberrant expression of programmed death ligand-1 (PD-L1) facilitates tumor immune evasion. Protein arginine methyltransferase 3 (PRMT3), a member of type I PRMT family, mediates asymmetric dimethylarginine (ADMA) modification of various substrate proteins. This study investigates the role of PRMT3 in PD-L1-associated tumor immunosuppression in hepatocellular carcinoma (HCC). Hepatocyte-specific knockout of Prmt3 significantly suppressed HCC progression in DEN-CCL4-treated mice. Knockout of Prmt3 in HCC cells markedly increased CD8+ T cell infiltration, and reduced lactate production in tumors. PRMT3 interacted with pyruvate dehydrogenase kinase 1 (PDHK1), asymmetric dimethylation of PDHK1 at arginine 363 and 368 residues and increased its kinase activity. The R363/368 K mutant or inhibition of PDHK1 by JX06 blocked the effect of PRMT3 on lactate production. JX06 treatment also attenuated the tumor-promoting role of PRMT3 in HCC in vitro and in vivo. Furthermore, RNA-seq analysis revealed that knockout of PRMT3 downregulates the tumor-associated immune checkpoint, PD-L1, in tumor tissues. Chromatin immunoprecipitation (ChIP) assay demonstrated that PRMT3 promotes lactate-induced PD-L1 expression by enhancing the direct binding of histone H3 lysine 18 lactylation (H3K18la) to the PD-L1 promoter. Tissue microarray analysis showed a positive correlation between PRMT3 and PD-L1 expression in HCC patients. Anti-PD-L1 treatment reversed PRMT3-induced tumor growth and restored CD8+ T cell infiltration. Our research links PRMT3-mediated metabolic reprogramming and immune evasion, revealing that the PRMT3-PDHK1-lactate-PD-L1 axis may be a potential target for improving the efficacy of immunotherapy in HCC.

NI-3201 Is a Bispecific Antibody Mediating PD-L1-Dependent CD28 Co-stimulation on T Cells for Enhanced Tumor Control

Despite advances in cancer immunotherapy, such as targeting the PD-1/PD-L1 axis, a substantial number of patients harbor tumors that are resistant or relapse. Selective engagement of T-cell co-stimulatory molecules with bispecific antibodies may offer novel therapeutic options by enhancing signal 1-driven activation occurring via T-cell receptor engagement. In this study, we report the development and preclinical characterization of NI-3201, a PD-L1×CD28 bispecific antibody generated on the κλ-body platform that was designed to promote T-cell activity and antitumor function through a dual mechanism of action. We confirmed that NI-3201 blocks the PD-L1/PD-1 immune checkpoint pathway and conditionally provides T-cell co-stimulation via CD28 (signal 2) when engaging PD-L1+ tumors or immune cells. In systems with signal 1-primed T cells, NI-3201 enhanced potent effector functionality: in vitro through antigen-specific recall assays with cytomegalovirus-specific T cells and in vivo by inducing tumor regression and immunologic memory in tumor-associated antigen-expressing MC38 syngeneic mouse models. When T-cell engagers were used to provide synthetic signal 1, the combination with NI-3201 resulted in synergistic T cell-dependent cytotoxicity and potent antitumor activity in two humanized mouse tumor models. Nonhuman primate safety assessments showed favorable tolerability and pharmacokinetics at pharmacologically active doses. Quantitative systems pharmacology modeling predicted that NI-3201 exposure results in antitumor activity in patients, but this remains to be investigated. Overall, this study suggests that by combining PD-L1 blockade with safe and effective CD28 co-stimulation, NI-3201 has the potential to improve cancer immunotherapy outcomes, and the clinical development of NI-3201 for PD-L1+ solid tumors is planned.

The role of type I interferon signaling in myeloid anti-tumor immunity

Tumors often arise in chronically inflamed, and thus immunologically highly active niches. While immune cells are able to recognize and remove transformed cells, tumors eventually escape the control of the immune system by shaping their immediate microenvironment. In this context, macrophages are of major importance, as they initially exert anti-tumor functions before they adopt a tumor-associated phenotype that instead inhibits anti-tumor immune responses and even allows for sustaining a smoldering inflammatory, growth promoting tumor microenvironment (TME). Type I interferons (IFNs) are well established modulators of inflammatory reactions. While they have been shown to directly inhibit tumor growth, there is accumulating evidence that they also play an important role in altering immune cell functions within the TME. In the present review, we focus on the impact of type I IFNs on anti-tumor responses, driven by monocytes and macrophages. Specifically, we will provide an overview of tumor-intrinsic factors, which impinge on IFN-stimulated gene (ISG) expression, like the presence of nucleic acids, metabolites, or hypoxia. We will further summarize the current understanding of the consequences of altered IFN responses on macrophage phenotypes, i.e., differentiation, polarization, and functions. For the latter, we will focus on macrophage-mediated tumor cell killing and phagocytosis, as well as on how macrophages affect their environment by secreting cytokines and directly interacting with immune cells. Finally, we will discuss how type I IFN responses in macrophages might affect and should be considered for current and future tumor therapies.

Oxaliplatin induces pyroptosis in hepatoma cells and enhances antitumor immunity against hepatocellular carcinoma

BACKGROUND

Pyroptosis is closely associated with chemotherapeutic drugs and immune response. Here, we investigated whether oxaliplatin, a key drug in FOLFOX-hepatic artery infusion chemotherapy (FOLFOX-HAIC), induces pyroptosis in hepatoma cells and enhances antitumor immunity after tumor cell death.

METHODS

Hepatoma cells were treated with oxaliplatin. Pyroptosis and immunoreactivity were evaluated in vitro and in vivo.

RESULTS

Oxaliplatin activated caspase-3-mediated gasdermin E (GSDME) cleavage and induced pyroptosis in Hep G2 and SK-Hep-1 cells in vitro. Liver cancer cells with high levels of GSDME expression are prone to pyroptosis. Bioinformatic analysis revealed that pyrolysis-related genes are closely related to immunity. In vivo experiments revealed that oxaliplatin exhibited superior antitumor efficacy in mice with normal immune function and more pronounced inhibitory effect on hepatocellular carcinoma with high GSDME levels. Higher levels of cytokines and greater CD8+ T cell infiltration were observed in tumor tissues with better efficacy. Furthermore, an in vitro coculture assay confirmed that oxaliplatin-induced pyroptosis in Hep G2 cells overexpressing GSDME and activated the p38/MAPK signaling pathway to improve the cytotoxicity of CD8+ T cells. Analysis of clinical samples of HCC suggested that the efficacy of FOLFOX-HAIC in patients with high GSDME expression was better than that in patients with low GSDME expression.

CONCLUSIONS

Oxaliplatin induced pyroptosis in hepatoma cells by activating caspase-3-mediated cleavage of GSDME, which enhanced the cytotoxicity of CD8+ T cells by regulating the p38/MAPK signaling pathway. These results suggest that GSDME level may be used as a marker to predict the efficacy of FOLFOX-HAIC.

Primary and Acquired Resistance to Immunotherapy with Checkpoint Inhibitors in NSCLC: From Bedside to Bench and Back

Immunotherapy with checkpoint inhibitors has become the cornerstone of systemic treatment for non-oncogene addicted non-small-cell lung cancer. Despite its pivotal role, a significant proportion of patients-approximately 70-85%-either exhibit primary resistance to PD-1 blockade or develop acquired resistance following an initial benefit, even in combination with chemotherapy and/or anti-CTLA-4 agents. The phenomenon of primary and acquired resistance to immunotherapy represents a critical clinical challenge, largely based on our incomplete understanding of the mechanisms of action of immunotherapy, and the resulting lack of accurate predictive biomarkers. Here, we review the definitions and explore the proposed mechanisms of primary and acquired resistance, including those related to the tumor microenvironment, systemic factors, and intrinsic tumor characteristics. We also discuss translational data on adaptive changes within tumor cells and the immune infiltrate following exposure to checkpoint inhibitors. Lastly, we offer a comprehensive overview of current and emerging therapeutic strategies designed to prevent primary resistance and counteract acquired resistance.

Alleviation of sepsis-induced lung and liver injury by polysaccharides from Tetrastigma hemsleyanum Diels et Gilg via suppression of TLR4/NF-κB/COX-2 pathway and modulation of immune checkpoint molecules

Sepsis, a common clinical complication, leads to multi-organ damage due to systemic infection and currently lacks effective therapeutic drugs. Polysaccharide derived from Tetrastigma hemsleyanum Diels et Gilg (TH), abbreviated as THP, is a water-soluble component extracted from TH, exhibiting anti-inflammatory and immunomodulatory properties. This study aims to investigate the effects and mechanisms of THP in sepsis. Results demonstrated that THP reduced neutrophils in the peripheral blood of mice established by cecal ligation and puncture (CLP), and inhibited IL-6 and MCP-1 in plasma, thereby improving systemic inflammation. THP ameliorated pulmonary edema, mitigated lung and liver histopathological injuries, reduced infiltration of neutrophils and macrophages in the lung and liver, and inhibited the TNF-α, IL-6, IL-1β, and MCP-1 transcription in both organs. Additionally, THP decreased myeloid cells, neutrophils, monocytes, and Tregs in the spleens of septic mice, while increasing T cells, CD4+ T cells, and CD8+ T cells, thereby restoring immune imbalance. Mechanistically, THP attenuated sepsis by inhibiting the overactivation of the TLR4/NF-κB/COX-2 pathway, and reducing PD-1, PD-L1, IDO1 in the lung, and PD-1, PD-L1 in the liver of septic mice. In conclusion, this study provides theoretical support for the potential application of THP in sepsis treatment.

Identification of immune subtypes associated with CD8+ T cell-related genes providing new treatment strategies of esophageal carcinoma

Background

CD8+ T lymphocytes greatly affect the efficacy of immunotherapy, displaying promising potential in various tumors. Here, we aimed to identify immune subtypes associated with CD8+ T cell-related genes to predict the efficacy of treatment in esophageal cancer (ESCA).

Methods

We obtained 13 immune cell-related datasets from the Gene Expression Omnibus (GEO) database and removed batch effects. Weighted correlation network analysis (WGCNA) and co-expression analysis were performed to identify highly correlated CD8+ T cell genes. Cox analysis was used to process ESCA clinical information, and the immune clusters (ICs) were constructed through consensus cluster analysis. Furthermore, we constructed an immune risk score model to predict the prognosis of ESCA based on these CD8+ T cell genes. This model was verified using the IMvigor210 dataset, and we functionally validated the immune risk score model in vitro.

Results

The results revealed significant correlations between CD8+ T cell-related genes and immune-related pathways. Three ICs were identified in ESCA, with IC3 demonstrating the most favorable prognosis. The final 6-gene prognostic risk model exhibited stable predictive performance in datasets across different platforms. Compared with that in normal esophageal epithelial (HEEC cells), CHMP7 in the 6-gene prognostic risk model was upregulated in KYSE150 and TE-1 cells. Si-CHMP7 transfection led to a decrease in tumor cell migration, invasion, and proliferation, accompanied by an accelerated apoptotic process.

Conclusions

Collectively, we identified the immune subtypes of CD8+ T cell-related genes with different prognostic significance. We designated CHMP7 in the 6-gene prognostic risk model as a potential target to improve tumor cell prognosis. These insights provide a strong basis for improving prognosis and facilitating more personalized and accurate treatment decisions for the immunotherapy of ESCA.

Enhanced thrombopoiesis supplies PD-L1 to circulating immune cells via the generation of PD-L1-expressing platelets in patients with lung cancer

BACKGROUND

The increased expression of programmed cell death ligand 1 (PD-L1) on a subset of immune cells in the peripheral blood has been frequently observed in patients with cancer, suggesting a relationship with PD-L1 expression in tumor tissues. In this study, we investigated the mechanisms underlying PD-L1 expression on various types of immune cells in the peripheral blood of patients with cancer.

METHODS

PD-L1 expression on various immune cell populations was analyzed in peripheral blood mononuclear cells of 112 patients with non-small cell lung cancer (NSCLC) using flow cytometry. A mouse model of X-ray-induced acute thrombocytopenia was used to investigate the relationship between thrombopoiesis and PD-L1-expressing platelet generation. The clinical significance of PD-L1-expressing platelets was analyzed in a cohort of patients with stage IV NSCLC who received a combination of anti-programmed cell death 1 (PD-1) therapy and chemotherapy.

RESULTS

All immune cell populations, including monocytes, T cells, B cells, and NK cells, showed higher PD-L1 expression in patients with cancer than in healthy controls. However, this increased frequency of PD-L1-expressing cells was not attributed to the expression of the cells themselves. Instead, it was entirely dependent on the direct interaction of the cells with PD-L1-expressing platelets. Notably, the platelet-dependent acquisition of PD-L1 on circulating immune cells of patients with lung cancer was observed in various other cancer types and was mechanistically associated with a surge in thrombopoiesis, resulting in the increased production of PD-L1-expressing reticulated platelets. Clinically, patients with enhanced thrombopoiesis and concurrently high PD-L1-expressing platelets exhibited a better response to anti-PD-1 therapy.

CONCLUSIONS

These findings highlight the role of tumor-associated thrombopoiesis in generating PD-L1-expressing platelets that may serve as a resource for PD-L1-positive cells in the circulation and act as a predictive biomarker for anti-PD-1/PD-L1 therapy.

MiR-340-5p regulates PD-L1 and predicts pembrolizumab response in extranodal NK/T-cell lymphoma

Extranodal NK/T-cell lymphoma (ENKTL) is an aggressive, chemoresistant non-Hodgkin lymphoma subtype with poor patient outcomes linked to elevated PD-L1 expression. This study investigates miRNA-mediated regulation of PD-L1, focusing on miR-340-5p and miR-424-5p as novel therapeutic targets and predictive biomarkers for pembrolizumab response. Through miRNA sequencing and functional assays, miR-340-5p and miR-424-5p were identified as key modulators of PD-L1 in drug-resistant ENKTL cells, with their roles validated via ribonucleoprotein immunoprecipitation and luciferase reporter assays. Notably, elevated miR-340-5p levels in PD-L1-negative ENKTL tissues were inversely correlated with soluble PD-L1, implicating miR-340-5p in immune evasion mechanisms. Additionally, low serum levels of miR-340-5p were associated with reduced pembrolizumab efficacy, positioning miR-340-5p as a promising predictive biomarker for immune checkpoint blockade. These findings suggest that pre-treatment assessment of serum miR-340-5p could guide pembrolizumab therapy in ENKTL, optimizing treatment outcomes. Validation in larger cohorts is necessary to confirm the utility of miR-340-5p as a predictive biomarker for ENKTL immunotherapy.

Lipid-siRNA Conjugates Targeting High PD-L1 Expression as Potential Novel Immune Checkpoint Inhibitors

Programmed death 1 ligand (PD-L1), an important immune checkpoint molecule, is mainly expressed on cancer cells and has been shown to exert an immunosuppressive effect on T-cell function by binding to programmed cell death 1 (PD-1) expressed on T-cells. Recently, immune checkpoint inhibitors using antibody drugs such as nivolumab and atezolizumab have attracted attention. However, clinical challenges, including limitations to the scope of their application, are yet to be addressed. In this study, we developed a novel immune checkpoint inhibitor that targets PD-L1 using lipid-siRNA conjugates (lipid-siPDL1s). The inhibitory effect of lipid-siPDL1s on PD-L1 expression was evaluated and found to strongly suppress mRNA expression. Notably, lipid-siPDL1s exerted a significantly stronger effect than unmodified siPDL1. Interestingly, lipid-siPDL1s strongly inhibited PD-L1 expression despite cancer cell stimulation by interferon-gamma, which induced the overexpression of PD-L1 genes. These results strongly suggest that lipid-siPDL1s could be used as novel immune checkpoint inhibitors.

Proteomic Analyses in COVID-19-Associated Secondary Hemophagocytic Lymphohistiocytosis

CONTEXT

COVID-19 has been associated with features of a cytokine storm syndrome with some patients sharing features with the hyperinflammatory disorder, secondary hemophagocytic lymphohistiocytosis (sHLH).

HYPOTHESIS

We hypothesized that proteins associated with sHLH from other causes will be associated with COVID-sHLH and that subjects with fatal COVID-sHLH would have defects in immune-related pathways.

METHODS AND MODELS

We identified two cohorts of adult patients presenting with COVID-19 at two tertiary care hospitals in Seattle, Washington in 2020 and 2021. In this observational study, we assessed clinical laboratory values and plasma proteomics. Subjects identified as having sHLH (ferritin > 1000 plus cytopenias in two or more lineages [WBC < 5000 odds ratio [OR] ANC (absolute neutrophil count) < 1000, hemoglobin < 9 or hematocrit < 27, platelets < 100,000], and elevated transaminases [either AST (aspartate aminotransferase) or ALT (alanine aminotransferase) > 30] OR subjects with a ferritin > 3000) were compared with those with COVID-19 without sHLH. We identified 264 patients with COVID-19 of whom 24 met our sHLH definition. Eight patients who died of COVID-sHLH underwent genomic sequencing to identify variants in immune-related genes.

RESULTS

Nine percent of enrolled COVID-19 subjects met our defined criteria for sHLH (n = 24/264). Using broad serum proteomic approaches (O-link and SomaScan), we identified three proteins increased in subjects with COVID-19-associated sHLH (soluble PD-L1 [sPD-L1], tumor necrosis factor-R1, and interleukin [IL]-18BP, p < 0.05 for O-link and false discovery rate < 0.05 for SomaScan), supporting a role for proteins previously associated with other forms of sHLH (IL-18BP and soluble tumor necrosis factor receptor 1). We also identified candidate proteins and pathways associated with COVID-sHLH, including sPD-L1 and the syntaxin pathway. We detected pathogenic variants in DOCK8 and TMPRSS15 in deceased individuals with COVID-sHLH, further suggesting that alterations in immune-related processes may contribute to hyperinflammation and fatal outcomes in COVID-19.

INTERPRETATIONS AND CONCLUSIONS

Proteins increased in COVID-19-associated sHLH, such as sPD-L1, and pathways, such as the syntaxin pathway, suggest important roles for the immune response in driving sHLH in the context of COVID-19.

Nuclear PD-L1 triggers tumour-associated inflammation upon DNA damage

Immune checkpoint inhibitors against PD-1/PD-L1 are highly effective in immunologically hot tumours such as triple-negative breast cancer, wherein constitutive DNA damage promotes inflammation, while inducing PD-L1 expression to avoid attack by cytotoxic T cells. However, whether and how PD-L1 regulates the DNA damage response and inflammation remains unclear. Here, we show that nuclear PD-L1 activates the ATR-Chk1 pathway and induces proinflammatory chemocytokines upon genotoxic stress. PD-L1 interacts with ATR and is essential for Chk1 activation and chromatin binding. cGAS-STING and NF-κB activation in the late phase of the DNA damage response is inhibited by PD-L1 deletion or by inhibitors of ATR and Chk1. Consequently, the induction of proinflammatory chemocytokines at this stage is inhibited by deletion of PD-L1, but restored by the ATR activator Garcinone C. Inhibition of nuclear localisation by PD-L1 mutations or the HDAC2 inhibitor Santacruzamate A inhibits chemocytokine induction. Conversely, the p300 inhibitor C646, which accelerates PD-L1 nuclear localisation, promotes chemocytokine induction. These findings suggest that nuclear PD-L1 strengthens the properties of hot tumours and contributes to shaping the tumour microenvironment.

Zinc nanoparticles from oral supplements accumulate in renal tumours and stimulate antitumour immune responses

A successful therapeutic outcome in the treatment of solid tumours requires efficient intratumoural drug accumulation and retention. Here we demonstrate that zinc gluconate in oral supplements assembles with plasma proteins to form ZnO nanoparticles that selectively accumulate into papillary Caki-2 renal tumours and promote the recruitment of dendritic cells and cytotoxic CD8+ T cells to tumour tissues. Renal tumour targeting is mediated by the preferential binding of zinc ions to metallothionein-1X proteins, which are constitutively overexpressed in Caki-2 renal tumour cells. This binding event further upregulates intracellular metallothionein-1X expression to induce additional nanoparticle binding and retention. In both tumour animal models and human renal tumour samples, we show that ZnO nanoparticles actively cross the vascular wall to achieve high intratumoural accumulation. We further explore this feature of ZnO nanoparticles for the delivery of chemotherapeutics to mouse and rabbit cancer models. Our findings demonstrate that ZnO nanoparticles derived from supplements can serve as a multifunctional drug delivery and cancer immunotherapy platform.

Loss of RPN1 promotes antitumor immunity via PD-L1 checkpoint blockade in triple-negative breast cancer - experimental studies

BACKGROUND

RPN1, also known as ribophorin I (RPN1), is a type I transmembrane protein that plays an important role in glycosylation. However, the effects of RPN1 on cancer progression and immune evasion in breast cancer (BC) have not been identified.

MATERIALS AND METHODS

The expression of RPN1 was evaluated using RT-qPCR and immunohistochemistry (IHC). The effects of RPN1 on tumor cells were assessed using RT-qPCR, western blotting, flow cytometry, Cell Counting Kit 8 (CCK-8), colony formation assays, and in vivo experiments. The mechanism by which RPN1 modifies programmed death ligand-1 (PD-L1) and the tumor microenvironment was examined by RT-qPCR, western blotting, co-immunoprecipitation (Co-IP), and flow cytometry. The influence of the transcription factor YY1 on RPN1 expression was revealed using bioinformatics analysis, RT-qPCR, and dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays.

RESULTS

RPN1 is aberrantly expressed in triple-negative breast cancer (TNBC) cells, correlating with increased proliferation and poor prognosis. RPN1 mediates the post-translational modification of PD-L1, enhancing its glycosylation and stability, thus facilitating PD-L1-mediated immune escape and tumor growth. The deletion of RPN1 improves the TNBC microenvironment and enhances the efficacy of anti-PD-1 therapy. Additionally, we uncovered a novel regulatory axis involving YY1/RPN1/YBX1 in PD-L1 regulation, affecting TNBC growth and metastasis.

CONCLUSIONS

Our preliminary study reveals that targeting RPN1 promotes immune suppression, providing a new potential immunotherapy strategy for TNBC. However, further research is necessary to fully elucidate and understand the specific mechanisms of RPN1 in TNBC and its potential for clinical application.

PTEN loss in glioma cell lines leads to increased extracellular vesicle biogenesis and PD-L1 cargo in a PI3K-dependent manner

Phosphatase and Tensin Homolog (PTEN) is one of the most frequently lost tumor suppressors in cancer and the predominant negative regulator of the PI3K-AKT signaling axis. A growing body of evidence has highlighted the loss of PTEN with immuno-modulatory functions including the upregulation of the programmed death ligand-1 (PD-L1), an altered tumor-derived secretome that drives an immunosuppressive tumor immune microenvironment and resistance to certain immunotherapies. Given their roles in immunosuppression and tumor growth, we examined whether the loss of PTEN would impact the biogenesis, cargo, and function of extracellular vesicles (EVs) in the context of the anti-tumor associated cytokine interferon-γ. Through genetic and pharmacological approaches, we show that total cellular expression of PD-L1 is regulated by JAK/STAT signaling, not PI3K signaling. Instead, we observe that PTEN loss specifically upregulates cell surface levels of PD-L1 and enhances the biogenesis of EVs enriched with PD-L1 in a PI3K-dependent manner. We demonstrate that because of these changes, EVs derived from glioma cells lacking PTEN have a greater ability to suppress T cell receptor signaling. Taken together, these findings provide important new insights into how the loss of PTEN can contribute to an immunosuppressive tumor immune microenvironment, facilitate immune evasion, and highlight a novel role for PI3K signaling in the regulation of EV biogenesis and the cargo they contain.

Loss of histone deubiquitinase Bap1 triggers anti-tumor immunity

PURPOSE

Immunotherapy using PD-L1 blockade is effective in only a small group of cancer patients, and resistance is common. This emphasizes the importance of understanding the mechanisms of cancer immune evasion and resistance.

METHODS

A genome-scale CRISPR-Cas9 screen identified Bap1 as a regulator of PD-L1 expression. To measure tumor size and survival, tumor cells were subcutaneously injected into both syngeneic WT mice and immunocompromised mice. The phenotypic and transcriptional characteristics of Bap1-deleted tumors were examined using flow cytometry, RNA-seq, and CUT&Tag-seq analysis.

RESULTS

We found that loss of histone deubiquitinase Bap1 in cancer cells activates a cDC1-CD8+ T cell-dependent anti-tumor immunity. The absence of Bap1 leads to an increase in genes associated with anti-tumor immune response and a decrease in genes related to immune evasion. As a result, the tumor microenvironment becomes inflamed, with more cDC1 cells and effector CD8+ T cells, but fewer neutrophils and regulatory T cells. We also found that the elimination of Bap1-deleted tumors depends on the tumor MHCI molecule and Fas-mediated CD8+ T cell cytotoxicity. Our analysis of TCGA data further supports these findings, showing a reverse correlation between BAP1 expression and mRNA signatures of activated DCs and T-cell cytotoxicity in various human cancers.

CONCLUSION

The histone deubiquitinase Bap1 could be used as a biomarker for tumor stratification and as a potential therapeutic target for cancer immunotherapies.

Expanding the diagnostic toolbox for complex genetic immune disorders

Laboratory-based immunology evaluation is essential to the diagnostic workup of patients with complex immune disorders, and is as essential, if not more so, depending on the context, as genetic testing, because it enables identification of aberrant pathways amenable to therapeutic intervention and clarifies variants of uncertain significance. There have been considerable advances in techniques and instrumentation in the clinical laboratory in the past 2 decades, although there are still "miles to go." One of the goals of the clinical laboratory is to ensure advanced diagnostic testing is widely accessible to physicians and thus patients, through reference laboratories, particularly in the context of academic medical centers. This ensures a greater likelihood of translating research discoveries into the diagnostic laboratory, on the basis of patient care needs rather than a sole emphasis on commercial utility. However, these advances are under threat from burdensome regulatory oversight that can compromise, at best, and curtail, at worst, the ability to rapidly diagnose rare immune disorders and ensure delivery of precision medicine. This review discusses the clinical utility of diagnostic immunology tools, beyond cellular immunophenotyping of lymphocyte subsets, which can be used in conjunction with clinical and other laboratory data for diagnosis as well as monitoring of therapeutic response in patients with genetic immunologic diseases.