Increased PD-L1 Expression Research Articles

IMMU-50. IMPACT OF SARS-COV-2 MRNA VACCINES ON PD-L1 EXPRESSION IN INTRACRANIAL TUMORS

Abstract Although immune checkpoint inhibitor (ICI) effectiveness is correlated with intra-tumoral PD-L1 expression, there are no clinically available methods to improve sensitivity to ICIs by modulating PD-L1 expression. mRNA vaccines stimulate robust interferon-dependent innate immune activation leading to four-fold increases in PD-L1 expression on peripheral and intratumoral myeloid cells and enhanced sensitivity to immune checkpoint blockade in preclinical models (Sayour, Grippin, et al., NanoLetters, 2018; Mendez-Gomez, et al., Cell, 2024). We hypothesized that mRNA vaccines targeting SARS-COV-2 would similarly enhance PD-L1 expression in intracranial tumors. To test this hypothesis, we utilized institutional databases to identify 5,524 patients at our institution with pathology reports including the term “PD-L1” from August 2020 to November 2023. Pathological data and dates of SARS-COV-2 vaccination were compiled for each patient. Across the entire cohort (n=5,524), receipt of a SARS-COV-2 mRNA vaccine within 100 days of biopsy was associated with a 55% increase in mean tumor proportion score (TPS) (14% vs 8.9%, p=0.029). In the subset of patients with intracranial tumors (n=187), receipt of a SARS-COV-2 mRNA vaccine within 100 days of biopsy was associated with a massive increase in TPS (57% vs 7.2%, p<0.001). To evaluate the impact of this change on clinical outcomes with immunotherapy, we utilized a second institutional database to assemble a cohort of patients with Stage IV melanoma with intracranial metastasis treated with immune checkpoint blockade during the period August 2020 through November 2023. Patients who received a SARS-COV-2 vaccine within 100 days of initiation of ICI (n=10) exhibited numerically improved overall survival compared to those without SARS-COV-2 mRNA vaccine (n=38) (HR 0.50, 95% CI 0.22-1.2, p=0.06). Median overall survival was 545 days among patients without COVID mRNA vaccination and was not met among those with COVID mRNA vaccination. This data supports further investigation of the immune modulating effect of SARS-COV-2 mRNA vaccines in patients with intracranial tumors treated with immune checkpoint blockade.

CNSC-59. EPIGENETIC POTENTIATION OF ANTI-TUMOR IMMUNE RESPONSES USING VIRAL MIMICRY IN GLIOMAS

Abstract Clinical trials using immune checkpoint inhibition(ICI) have traditionally failed in glioblastoma (GBM). Viral mimicry, which augments anti-tumor immune responses and sensitizes response to immunotherapy in other cancers, involves the epigenetic activation of endogenous retroelements (REs). REs are silenced via the HUSH complex and H3K9me3. This process is mediated by ZNF638. We aimed to elucidate the role of viral mimicry in enhancing ICI through epigenetic reprogramming of the HUSH complex. We demonstrated that RE expression among 48 superfamilies inversely correlated with ZNF638 expression in gliomas, based on data from 71 newly-diagnosed GBMs. Using transcriptional deconvolution, we showed ZNF638 negatively correlates with innate antiviral immune response signatures(TLR3)(RTLR3=-0.300,pTLR3=0.00006). We validated these in-silico results in pure glioma cell lines, patient-derived GBM neurospheres, and syngeneic murine models. ZNF638 knockdown induced intracellular RE-mediated dsRNA signaling cascades via RIG-I and TLR3. This knockdown significantly increased PD-L1 expression(p<0.001), reduced H3K9 trimethylation, and enhanced cytoplasmic dsRNA accumulation in glioma cell lines. In patient-derived GBM neurospheres, ZNF638 knockdown upregulated immune and antiviral programs. Additionally, knockdown resulted in upregulation of several endogenous repeat elements (Alu, LTR). Single-cell RNA sequencing showed ZNF638 clustering in neural progenitor-like and oligodendrocyte-like cells, with increased retroelement expression in low ZNF638 cells. Tumors with lower ZNF638 expression showed increased CD8+ populations. Bulk RNA sequencing deconvolution revealed that ZNF638 is linked to reduced CD8 and DC infiltration in gliomas (RCD8=-0.202,RDC=-0.198;pCD8=8.79E-06,pDC=1.34E-05). In immunocompetent mice, ZNF638 KO and PD-L1 inhibition significantly improved survival (mOS >50 days, p<0.0001) and reduced tumor volume (p<0.001). Analysis of cohorts from multiple cancer types treated with anti-PD1 therapy demonstrated that ZNF638 expression predicts therapeutic response and overall survival. Our findings suggest that epigenetic reprogramming through HUSH inhibition may potentiate immunotherapy for GBM.

The R1441C-Lrrk2 mutation induces myeloid immune cell exhaustion in an age- and sex-dependent manner in mice.

Age is the greatest risk factor for many neurodegenerative diseases, yet immune system aging, a contributor to neurodegeneration, is understudied. Genetic variation in the LRRK2 gene affects risk for both familial and sporadic Parkinson's disease (PD). The leucine-rich repeat kinase 2 (LRRK2) protein is implicated in peripheral immune cell signaling, but the effects of an aging immune system on LRRK2 function remain unclear. We analyzed peritoneal macrophages from R1441C-Lrrk2 knock-in mice and observed a biphasic, age-dependent effect of the R1441C-Lrrk2 mutation on peritoneal macrophage function. We report increases in antigen presentation, anti-inflammatory cytokine production, lysosomal activity, and pathogen uptake in peritoneal macrophages from young (2- to 3-month-old) female R1441C-Lrrk2 mice. Conversely, macrophages from aged (18- to 21-month-old) female R1441C-Lrrk2 mice exhibited decreased antigen presentation after inflammatory insult, decreased lysosomal function, and pathogen uptake, with a concomitant increase in DNA fragmentation in the presence of pathogens. This immune cell exhaustion phenotype was not observed in male R1441C-Lrrk2 mice and was driven by increased LRRK2 protein kinase activity. This phenotype was also observed in human peripheral myeloid cells, with monocyte-derived macrophages from patients with PD who had either the R1441C- or Y1699C-LRRK2 mutation exhibiting decreased pathogen uptake and increased PDL1 expression, consistent with immune cell exhaustion. Our findings that LRRK2 mutations conferred an immunological advantage at a young age but could predispose the carrier to age-acquired immune cell exhaustion have implications for the therapeutic development of LRRK2 inhibitors.

Mitochondrial Iron Metabolism as a Potential Key Mediator of PD-L1 Thermal Regulation

Glioblastoma (GBM) is the most common primary brain malignancy in the U.S. with a 5-year overall survival < 5% despite an aggressive standard of care. Laser interstitial thermal therapy (LITT) is a surgical approach to treating GBM that has gained traction, providing a safe option for reducing intracranial tumor burden. LITT is believed to potentially modulate GBM immune responses; however, the biochemical mechanisms underlying the modulation of immune checkpoints in GBM cells have been poorly characterized. The present study aimed to preliminarily evaluate the effects of thermal therapy and radiation on PD-L1 modulation in vitro, as a function of IDH mutational status. U87 cells and their IDH-mutant counterpart (U87R132H), which was generated using a crispr-cas9 knock-in approach, were utilized for this preliminary evaluation. Cell heating was achieved by harvesting with trypsin centrifugation where the cell pellets were treated on a heat block for the associated time and temperature. Following thermal therapy, cells were resuspended and irradiated using a 37-Cesium irradiator at 0.6 Gy min−1. Immediately following treatment, cells were either plated as single cells to allow colonies to form, and stained with Coomassie blue to be counted approximately 10–14 days later or harvested for Western blot analysis. Cell lysates were analyzed for PD-L1 expression with respect to various iron metabolic parameters (mortalin (HSPA9), transferrin receptor, and ferritin heavy chain) using a Western blotting approach. In both U87 and U87R132H cell lines, thermal therapy showed a temperature-dependent cell-killing effect, but U87R132H cells appeared more sensitive to thermal treatment when treated at 43 °C for 10 min. Moreover, thermal therapy had minimal effects on cell responses to 2 Gy irradiation. Treatment with thermal therapy downregulated PD-L1 expression in U87R132H cells, which was associated with increased expression of the mitochondrial iron metabolic enzyme, HSPA9. Thermal therapy reversed the radiation-induced overexpression of PD-L1, transferrin receptor, and ferritin heavy chain in U87R132H cells. No effects were observed in wild-type U87 cells. Moreover, Ga(NO3)3 depleted mitochondrial iron content which, in turn, significantly enhanced the sensitivity of U87R132H cells to thermal therapy and 2 Gy irradiation and caused a significant increase in PD-L1 expression. These results suggest that thermal therapy alone can modulate the immune checkpoint PD-L1. This effect was more pronounced when thermal therapy was combined with radiation. Mechanistically, mitochondrial iron trafficking through HSPA9 may coordinate the regulation of PD-L1 in the context of thermal therapy and ionizing radiation, which can be targeted with gallium-based therapy. These novel, preliminary findings warrant further mechanistic investigations in pre-clinical models of LITT.

Preoperative chemo-CIRT in Re/BRe pancreatic cancer: Insights from a multicenter prospective phase II clinical study (NCT03822936).

There is debate about the optimal management of borderline resectable (bRe) and resectable (Re) pancreatic ductal adenocarcinoma (PDAC). Both preclinical and clinical evidence showed that carbon ion radiotherapy (CIRT) produces superior control on radioresistant histologies compared to conventional photon beam radiotherapy (RT). However, so far there is a lack of data concerning the integration of CIRT in a multimodal approach with chemotherapy and surgery for bRe/Re. We recently presented the first analysis of a multicenter prospective phase II clinical study aimed at assessing the feasibility and effectiveness of a neoadjuvant chemotherapy + short course of CIRT followed by surgery and adjuvant chemotherapy in the management of bRe/Re PDAC. The study was terminated early due to low patient enrollment.Herein, we reported a post-hoc analysis focusing on toxicity, dosimetry and translational assessment. In our experience, CIRT can be integrated into a multimodal treatment strategy for bRe/Re PDAC, alongside chemotherapy and surgery. A case of fatal liver failure occurring three months post-surgery has been documented, likely related to the combination approach. Although the treatment plans were satisfactory according to the Local Effect Model (LEM) model, recalculations using the modified Microdosimetric Kinetic Model (mMKM) revealed suboptimal target coverage. Additionally, we observed an increased expression of PD-L1 following CIRT. This multimodal approach was well tolerated; however, clinicians should carefully monitor for vascular disorders during follow-up and further investigate surgical techniques after CIRT. The increased PD-L1 expression supports the immunogenic effects of particle therapy and lays the groundwork for future studies. To enhance the therapeutic ratio of CIRT treatments, integrating dose-averaged LETd (LETd-based objectives into the plan optimization process should be considered. ClinicalTrials.gov Identifier: NCT03822936.

Immunomodulatory effects of trastuzumab deruxtecan through the cGAS-STING pathway in gastric cancer cells

Although the efficacy of trastuzumab deruxtecan (T-DXd) against HER2-positive gastric cancers (GCs) has driven its clinical application, the precise mechanisms governing its immunomodulatory role remain unclear. In this study, we examined the immune-related mechanisms of action of T-DXd in GC cells. T-DXd exhibited potent antitumor effects in GC cells across diverse HER2 expression levels by inducing DNA damage and apoptosis. Activation of the DNA damage response by T-DXd led to increased PD-L1 expression. RNA-Seq analysis revealed that T-DXd modulated immune-related pathways, resulting in the upregulation of genes associated with inflammation and IFN signaling. Importantly, T-DXd activated the cGAS-STING pathway, inducing an IFN-I response in HER2-positive GC cells. Furthermore, T-DXd activated dendritic cells via the cancer cell-intrinsic cGAS-STING-IFN axis and enhanced PBMC-mediated tumor cell killing by activating CD8+ T cells. These findings provide valuable insights into the role of the cytosolic DNA sensing pathway in the action of T-DXd and offer a compelling rationale for combining T-DXd with immune checkpoint blockade therapies in GC treatment.

All-trans retinoic acid-mediated ADAR1 degradation synergizes with PD-1 blockade to suppress pancreatic cancer.

As a double-stranded RNA-editing enzyme and an interferon-stimulated gene, double-stranded RNA-specific adenosine deaminase (ADAR1) suppresses interferon signaling and contributes to immunotherapy resistance. Suppression of ADAR1 overcomes immunotherapy resistance in preclinical models, but has not yet been translated to clinical settings. By conducting a screening of a subset of the FDA-approved drugs, we found that all-trans retinoic acid (ATRA, also known as tretinoin) caused ADAR1 protein degradation through ubiquitin-proteasome pathways and concomitantly increased PD-L1 expression in pancreatic and breast cancers. In addition, the combination of ATRA and PD-1 blockade reprogrammed the tumor microenvironment and unleashed antitumor immunity and thereby impeded tumor growth in pancreatic cancer mouse models. In a pilot clinical trial, a higher dose of ATRA plus the anti-PD-1 antibody nivolumab prolonged median overall survival in patients with chemotherapy-resistant pancreatic cancer compared to a lower dose of the same regimen. In this study, ATRA was the first drug to be found to cause ADAR1 degradation. We propose translation of a promising 2-pronged antitumor strategy using ATRA and nivolumab to convert immunologically "cold" into "hot" tumors susceptible to immune checkpoint blockade.

Abstract B011: MTA-cooperative PRMT5 inhibition (BMS-986504) induces MTAP del tumor cell-intrinsic immune evasion and regulation

Abstract Homozygous deletion of MTAP gene (MTAP del) occurs in ∼10% of all cancers. BMS- 986504 is a second-generation MTA-cooperative PRMT5 inhibitor designed to preferentially bind to the PRMT5-MTA complex which accumulates in MTAP del cancer cells and has demonstrated clinical proof-of-concept (POC) for selectively inhibiting PRMT5 activity in MTAP del patients as monotherapy. While immunotherapy (IO) has increased patient survival in many cancers and is now the standard of care in first and later lines, most patients ultimately relapse. Thus, there remains an unmet need to improve response for these patients receiving IO. BMS-986504 in combination with anti- PD1 has the potential to increase efficacy, but there is a limited understanding of the interaction between MTAP/PRMT5 biology and PD-1 blockade. Here, we evaluated the BMS-986504-induced immunological and cell killing effects on MTAP del tumor cells and T cells to understand potential mechanisms to support BMS-986504 combination opportunities with anti-PD1 therapy. Using a panel of human PBMC-derived T cells, we first demonstrate that non-activated T cells and T cells activated via anti-CD3/CD28 are insensitive to BMS-986504-induced cell killing at in vitro concentrations equivalent to clinical exposure, supporting the significantly improved selectivity margin of BMS- 986504 relative to first-generation PRMT5 inhibitors that showed T cell toxicity in vitro and on-target dose-limiting hematological toxicity in the clinic. Since previous studies have suggested that MTAP wild-type cells may be affected by MTA secreted from surrounding MTAP del tumors, we assessed T cell viability in the presence of MTA. We found that inactivated T cells maintain insensitivity to BMS-986504 treatment with or without extracellular MTA, but T cells activated via anti-CD3/CD28 are partially sensitive to BMS-986504-induced killing in the presence of MTA only. Using flow cytometry, we characterized the surface expression of immune-related markers on tumor cells treated with BMS-986504 and identified that BMS-986504 dose-dependently increases PD-L1 expression on MTAP del tumor cells, suggesting a potential immune evasion mechanism. Next, using human PBMC-derived T cell and tumor cell co-culture assays, we evaluated the ability of BMS-986504 and anti-PD1 combination to mediate both tumor-intrinsic killing and anti-tumor immune activation in MTAP del cancer cell lines. Taken together, we provide translational proof-of-concept data demonstrating that BMS- 986504 induces tumor cell-intrinsic immunological effects in MTAP del tumors, while having limited impact on T cell viability. This data supports the rationale for BMS- 986504 and IO combination, which may potentially lead to anti-tumor immune activation and improved outcome for MTAP del patients. Citation Format: Josephine Hai, Stephanie Xavier, Sangeeth George, Lars Engstrom, Pete Olson, Tyler Simpson, Ming Lei, Benjamin Chen. MTA-cooperative PRMT5 inhibition (BMS-986504) induces MTAP del tumor cell-intrinsic immune evasion and regulation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr B011.

Antagonistic roles of cGAS/STING signaling in colorectal cancer chemotherapy.

FOLFOX, composed of 5-FU, oxaliplatin and leucovorin, is a first line chemotherapy regimen for colorectal cancer (CRC) treatment. In this study, we show that 5-FU and oxaliplatin induce DNA damage and activate cGAS/STING signaling leading to enhanced expression of interferon (IFN) β, IFN-stimulated genes and inflammatory cytokines in mouse and human colon cancer cells as well as increased intratumoral CD8+ T cells in mice. Crucially, 5-FU and oxaliplatin increase PD-L1 expression at the mRNA and protein levels, which has been shown to inhibit CD8+ T cell function. Depletion of cGAS, STING, IRF3, or IFNα/β receptor 1 (IFNAR1) abolishes this increase, indicating that 5-FU/oxaliplatin mediated upregulation of PD-L1 expression is dependent on tumor cell intrinsic cGAS/STING signaling. These results imply opposing roles for FOLFOX during cancer treatment. On one hand, 5-FU and oxaliplatin activate the innate immune response to facilitate anti-tumor immunity, and conversely upregulate PD-L1 expression to evade immune surveillance. Analysis of TCGA colon cancer dataset shows a positive correlation between expression of PD-L1 and components of the cGAS/STING pathway, supporting a role for cGAS/STING signaling in upregulating PD-L1 expression in colon cancer patients. Tumor studies in syngeneic immune competent mice demonstrate that the combination of 5-FU/oxaliplatin and anti-PD-1 significantly reduced tumor growth of colon cancer cells compared to 5-FU/oxaliplatin treatment alone. Taken together, our studies have identified a unique pathway leading to chemoresistance and provide a rationale to combine FOLFOX with anti-PD-1/PD-L1 as an effective CRC treatment.

Qingshen granules inhibits dendritic cell glycolipid metabolism to alleviate renal fibrosis via PI3K-AKT-mTOR pathway

BackgroundQingshen exhibits anti-inflammatory and immunoregulation effects to renal damage. Dendritic cells (DCs) play a critical role in regulating the pathologic inflammatory environment in renal fibrosis (RF). PurposeTo investigate the immune modulation mechanism of qingshen granule (QSG) in RF, particularly focusing on the role of DCs. Methods/Study designAdenine-induced RF animal models were used to study the pharmacological effects of QSG and the immune cells differentiation and function. Glucose uptake, non-esterified fatty acids secretion, mitochondrial membrane potential (MMP) detection, and qPCR were used to explore the effect of QSG to glucose and lipid metabolism in DCs and T cells. The effect of QSG to PI3K-AKT-mTOR axis and the modulation of mTOR to PD-L1 were explored by co-culture experiments, co-immunoprecipitation and western blot assays. The interaction of DCs/CD8+T cells and renal tubular epithelial cells (RTECs) was investigated to demonstrate the direct action and/or the immune-mediated regulation of QSG to RF. The components of QSG in the serum were determined by HPLC. And the effect of active ingredients and formula to DCs and T cells was analyzed by cell experiments in vitro. ResultsQSG reduced nephritic histopathological damage and suppressed the release of proinflammatory cytokines in adenine-induced RF mice. Of note, QSG decreased the levels of CD86, MHC-II, and CCR7 on DCs, while, increased PD-L1 expression on DCs in RF. The results demonstrated that QSG promoted the maturation and inhibited the migration of DCs, and QSG decreased the antigen presenting of DCs to T cells. Additionally, QSG reduced the MMP and glucose/lipid utilization ratio in DCs. QSG also down-regulated the level of targeted metabolic genes included glucose transporter 1 (Glut1), sterol-regulatory element-binding protein 1 (Srebp1), acetyl-CoA carboxylase alpha (Acaca), phosphomevalonate kinase (Pmvk), and up-regulated sirtuin2 (Sirt2) in DCs. In terms of mechanism, QSG inhibited the metabolism-related PI3K-AKT-mTOR pathway, followed by regulating the interaction of mTOR with PD-L1 to enhance the membrane stability of PD-L1. Besides, HPLC analysis identified five active ingredients in QSG. The specific anti-inflammatory and immunosuppressive actions of these ingredients were found to be weaker than QSG as a whole. Finally, inhibiting DC function by QSG disrupted the communication among DCs, T cells, and RTECs. This disruption was associated with low expression of α-smooth muscle actin (α-SMA) and collagen type I (Col-I) in the kidney. ConclusionsQSG inhibits DC metabolism and function via the PI3K-AKT-mTOR pathway to alleviate RF. The study highlights the importance of the specific composition of the formula in targeting DC-mediated immune regulation.

Downregulating LKB1 in bone marrow mesenchymal stem cells could inhibit CD4+ T cell proliferation via the PD-1/PD-L1 signaling pathway

BackgroundOur previous research has shown that LKB1 in amniotic mesenchymal stem cells (MSCs) serves as a vital regulator of regulatory T cell differentiation and T cell proliferation, which may have a similar role in bone marrow MSCs (BMMSCs). Therefore, we investigated the role of LKB1 in BMMSCs for regulating CD4+ T cell proliferation in the bone micro-environment of AML. MethodsRT-PCR was used to assessed LKB1 expression in BMMSCs derived from AML patients and healthy controls. Subsequently, LKB1 was knocked down in the BMMSCs line HS-5 (HS-5-LKB1KD). Co-cultures in vitro were established to analyze the effect of HS-5-LKB1KD on CD4+ T cell. Flow cytometry was employed to measure PD-L1 and CD4+ T cell proliferation levels. Western blot was utilized to detect related proteins. ResultsThe expression of LKB1 in BMMSCs derived from AML patients was decreased. Knockdown of LKB1 in HS-5 resulted in upregulation of PD-L1 expression. Co-culture of peripheral blood CD4+ T cell with HS-5-LKB1KD exhibited reduced CD4+ T cell proliferation compared to co-culture with HS-5-LKB1con. Furthermore, blocking PD-L1 in the co-culture conditions could restore the reduced CD4+ T cell proliferation. Additionally, it was found that upregulation of the Wnt signaling pathway-related proteins following LKB1 knockdown in HS-5, indicating that downregulating LKB1 could promote PD-L1 expression through activation of the Wnt signaling pathway. ConclusionsThe decreased expression of LKB1 in BMMSCs may activate the Wnt signaling pathway, leading to increased PD-L1 expression. This inhibited CD4+ T cell proliferation, which might lead to impaired anti-tumor immunity in AML patients and promote AML progression.

Tumor-Activated Neutrophils Promote Lung Cancer Progression through the IL-8/PD-L1 Pathway.

Lung cancer remains a major global health threat due to its complex microenvironment, particularly the role of neutrophils, which are crucial for tumor development and immune evasion mechanisms. This study aimed to delve into the impact of lung cancer cell-conditioned media on neutrophil functions and their potential implications for lung cancer progression. Employing in vitro experimental models, this study has analyzed the effects of lung cancer cell-conditioned media on neutrophil IL-8 and IFN-γ secretion, apoptosis, PD-L1 expression, and T-cell proliferation by using techniques, such as ELISA, flow cytometry, immunofluorescence, and CFSE proliferation assay. The roles of IL-8/PD-L1 in regulating neutrophil functions were further explored using inhibitors for IL-8 and PD-L1. Lung cancer cell lines were found to secrete higher levels of IL-8 compared to normal lung epithelial cells. The conditioned media from lung cancer cells significantly reduced apoptosis in neutrophils, increased PD-L1 expression, and suppressed T-cell proliferation and IFN-γ secretion. These effects were partially reversed in the presence of IL-8 inhibitors in Tumor Tissue Culture Supernatants (TTCS), while being further enhanced by IL-8. Both apoptosis and PD-L1 expression in neutrophils demonstrated dose-dependency to TTCS. Additionally, CFSE proliferation assay results further confirmed the inhibitory effect of lung cancer cell-conditioned media on T-cell proliferation. This study has revealed lung cancer cell-conditioned media to modulate neutrophil functions through regulating factors, such as IL-8, thereby affecting immune regulation and tumor progression in the lung cancer microenvironment.

Anti-PD-L1 blockade facilitates antitumor effects of radiofrequency ablation by improving tumor immune microenvironment in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a complex disease with advanced presentation that significantly affects survival rates. Therefore, novel therapeutic strategies are needed. In this study, we investigate the tumor microenvironment (TME) in HCC by analyzing 13 HCC samples at single cell level. We identified key cell populations, including CD8 + T cells, Tregs, M1/M2 macrophages, and CD4 + memory T cells, and explored their roles and interactions. Our research revealed an early enrichment of CD8 + T cells, which could potentially lead to their exhaustion and facilitate tumor progression. We also investigated the impact of percutaneous radiofrequency ablation (RFA) on the immune microenvironment. Using a dual tumor mouse model, we demonstrated that RFA induces necrosis, enhancing antigen presentation and altering immune responses. Our results indicate that RFA increases PD-L1 expression in residual liver tissue, suggesting potential immune escape mechanisms. Furthermore, the combination of RFA and anti-PD-L1 therapy in the mouse model resulted in significant improvements in immune modulation. This included increased CD8 + T cell efficacy and decreased Treg infiltration. This combination shows promise as an approach to counteract HCC progression by altering the immune landscape. This study highlights the critical interaction within the TME of HCC and suggests the possibility of improving patient outcomes by targeting immune evasion mechanisms through combined therapeutic strategies.

Expression of immune checkpoint markers in peripheral blood lymphocytes of women with fibroadenoma of the breast

Changes of the immune state in patients with fibroadenoma (FA) or other benign lesions of the breast, as well as the involvement of immune checkpoints in pathogenesis of these lesions, remain underexplored. The aim of this study was to compare the expression level of the key immune checkpoint markers CD279/PD-1, CD274/PD-L1, CD366/TIM3, and CD223/LAG3 in total circulating lymphocytes, T cell population as well as in its CD4 and CD8 subsets in peripheral blood from women with breast FA and healthy controls. Blood samples were taken from 12 women diagnosed with FA of the breast (aged 23-54 years, FA group) and 15 healthy women (aged 22-52 years, control group). Sample uptake was performed immediately before surgery, and samples were further analyzed by multicolor flow cytometry using monoclonal antibodies CD3-VioBlue, CD4/CD8-FITC, PD1-PE, PD-L1-PerCP-Cy.5.5, and TIM3/LAG3-APC. Each sample was incubated with 4 antibody combinations: CD3/CD4/PD1/PD-L1/TIM3, CD3/CD4/PD1/PD-L1/LAG3, CD3/CD8/PD1/PD-L1/TIM3, and CD3/CD8/PD1/PD-L1/LAG3. First, mono-expression of each of the 4 immune checkpoint markers was evaluated in the lymphocyte gate from both investigated groups. In FA samples, a significant increase in PD-L1 expression (assessed as percent of positive cells and fluorescence intensity change) was observed. Regarding expression of immune checkpoints in CD3+ T cells, along with significantly increased %PD-L1+, elevated numbers of PD1+T cells were detected. As for the differences in immune checkpoint expression changes between CD4+ and CD8+ T cell subsets, FA patient group demonstrated a more prominent increase in the amount of CD8+PD1+T cells relative to CD4 subset. The profiles of PD-L1 changes in CD4 and CD8 subpopulations were comparable showing, in both cases, a significant increase in FA sample group. We also analyzed changes in co-expression of any two immune checkpoint markers in CD4+ and CD8+ T cell subsets. The most noticeable was as increase in the prevalence of PD1+PD-L1+ phenotype in both T cell subpopulations from FA patients compared to the controls. With respect to co-expression of 3 checkpoint markers in CD4+ and CD8+ T cells, a significant increase in the percentage of PD1+PD-L1+TIM3+ cells among CD4 T helpers was found in FA. Thus, specific changes of T cell phenotype related to (co-)expression of immune checkpoint regulators may occur in systemic circulation of women with breast FA.

Loss of STK11 Suppresses Lipid Metabolism and Attenuates KRAS-Induced Immunogenicity in Patients with Non-Small Cell Lung Cancer.

In patients with lung cancer, we demonstrate that KRAS mutations increase tumor immunogenicity; however, KRAS/STK11 co-mutated patients display an immune-excluded phenotype. KRAS/STK11 co-mutated patients also demonstrated significant downregulation of several key lipid metabolism genes, many of which were associated with increased immunogenicity and improved overall survival in KRAS-mutated patients. Hence, alteration to lipid metabolism warrants further study as a potential biomarker and target for therapy in patients with KRAS-mutated lung cancer.

The recruitment of CD8+ T cells through YBX1 stabilization abrogates tumor intrinsic oncogenic role of MIR155HG in lung adenocarcinoma

Previous studies revealed that MIR155HG possessed an oncogenic role in many types of tumors including lung adenocarcinoma (LUAD), along with higher expression in tumors. However, in our study, we observed a positive correlation between MIR155HG expression and overall survival across different cohorts. The transferred PBMC on the NCG mouse model abrogated the tumor intrinsic oncogenic role of MIR155HG in LUAD. Upregulation of MIR155HG positively correlated with CD8+ T cell infiltration both in vitro and in vivo, as well as LUAD tissues. Mechanistically, we revealed that MIR155HG increased the cytokine CCL5 expression at the transcriptional level, which depended on the interaction between MIR155HG and YBX1 protein, a novel transcription factor of CCL5, resulting in the more protein stability of YBX1 through dampening ubiquitination. Additionally, we also observed that MIR155 could increase PD-L1 expression to hamper the activity of recruited CD8+ T cells, which could be rescued through PD-L1 mAb addition. Finally, we uncovered that patients with high MIR155HG expression had a higher response rate to immunotherapy, and the combination of MIR155HG overexpression and PD-L1 mAb increased the efficacy of PD-L1 mAb. Together, our study provides a novel biomarker and potential combination treatment strategy for patients who received immunotherapy.

Expression of PD-L1 Is Increased by Methionine Restriction Using Recombinant Methioninase in Human Colorectal Cancer Cells.

It has been recently demonstrated that a methionine-restricted diet increases the response to immune checkpoint inhibitors (ICIs) via an increase in PD-L1 in a syngeneic mouse colorectal-cancer model. Our laboratory has developed recombinant methioninase (rMETase) to restrict methionine. The aim of the present study was to determine if rMETase can increase PD-L1 expression in a human colorectal cancer cell line in vitro. We evaluated the half-maximal inhibitory concentration (IC50) value of rMETase on HCT-116 human colorectal cancer cells. HCT-116 cells were treated with rMETase at the IC50 Western immunoblotting was used to compare PD-L1 expression in HCT-116 cells treated with and without rMETase. The IC50 value of rMETase on HCT-116 was 0.79 U/ml. Methionine restriction using rMETase increased PD-L1 expression compared to the untreated control (p<0.05). Methionine restriction with rMETase up-regulates PD-L1 expression in human colorectal cancer cells and the combination of rMETase and ICIs may have the potential to improve immunotherapy in human colorectal cancer.

CXCR7 activation evokes the anti-PD-L1 antibody against glioblastoma by remodeling CXCL12-mediated immunity

The interaction between glioblastoma cells and glioblastoma-associated macrophages (GAMs) influences the immunosuppressive tumor microenvironment, leading to ineffective immunotherapies. We hypothesized that disrupting the communication between tumors and macrophages would enhance the efficacy of immunotherapies. Transcriptomic analysis of recurrent glioblastoma specimens indicated an enhanced neuroinflammatory pathway, with CXCL12 emerging as the top-ranked gene in secretory molecules. Single-cell transcriptome profiling of naïve glioblastoma specimens revealed CXCL12 expression in tumor and myeloid clusters. An analysis of public glioblastoma datasets has confirmed the association of CXCL12 with disease and PD-L1 expression. In vitro studies have demonstrated that exogenous CXCL12 induces pro-tumorigenic characteristics in macrophage-like cells and upregulated PD-L1 expression through NF-κB signaling. We identified CXCR7, an atypical receptor for CXCL12 predominantly present in tumor cells, as a negative regulator of CXCL12 expression by interfering with extracellular signal-regulated kinase activation. CXCR7 knockdown in a glioblastoma mouse model resulted in worse survival outcomes, increased PD-L1 expression in GAMs, and reduced CD8+ T-cell infiltration compared with the control group. Ex vivo T-cell experiments demonstrated enhanced cytotoxicity against tumor cells with a selective CXCR7 agonist, VUF11207, reversing GAM-induced immunosuppression in a glioblastoma cell-macrophage-T-cell co-culture system. Notably, VUF11207 prolonged survival and potentiated the anti-tumor effect of the anti-PD-L1 antibody in glioblastoma-bearing mice. This effect was mitigated by an anti-CD8β antibody, indicating the synergistic effect of VUF11207. In conclusion, CXCL12 conferred immunosuppression mediated by pro-tumorigenic and PD-L1-expressing GAMs in glioblastoma. Targeted activation of glioblastoma-derived CXCR7 inhibits CXCL12, thereby eliciting anti-tumor immunity and enhancing the efficacy of anti-PD-L1 antibodies.

LGG-46. MEKI WITH MIRDAMETINIB: EXPLORING ADAPTIVE SIGNALING PATHWAY DYNAMICS AND IMMUNE MODULATION IN PEDIATRIC GLIOMAS

Abstract INTRODUCTION Glial neoplasms are among the most common types of solid tumors in children. The mitogen-activated protein kinase (MAPK) pathway is implicated in glioma tumorigenesis. Drugs targeting this pathway hold promise as novel therapy for this disease. Vertical inhibition of the MAPK pathway has been linked to increased inflammation in several other cancers but similar exploration in pediatric brain tumors is limited. Within the MAPK pathway, MEK plays a significant role as a modulator of ERK phosphorylation. This study investigates the therapeutic potential of the MEK inhibitor, Mirdametinib, and evaluates the drugs’ capacity to induce tumor-intrinsic inflammation by characterizing changes in PD-L1 expression and proliferation in a panel of pediatric glial neoplasms. METHODS Three cell lines were included in the panel (Res186, Res259, SF188) and were treated with Mirdametinib for 3, 5, or 7 days. P-ERK expression, analyzed by western blot, verified successful inhibition of MEK by Mirdametinib. The CCK8 cytotoxic assay was utilized to determine the drug’s 50% inhibitory concentration as well as its direct effects on cell viability. Changes in Ki67 expression assessed by flow cytometry further characterized Mirdametinib’s effects on cell proliferation. Flow cytometry was also utilized to measure changes in PD-L1 expression following treatment. RESULTS Despite minimal effects on proliferation as measured by Ki67 and CCK8, expression of P-ERK verifies successful inhibition of MEK. Western blot data also reveals increased Pi3K/AKT pathway activity in SF188 groups treated with Mirdametinib. FACS data for SF188 also demonstrates increased PD-L1 expression in response to treatment. CONCLUSIONS Data suggests that, in response to MEKi, gliomas utilize compensatory growth mechanisms through Pi3K/AKT signaling. Findings also point to immune-modulatory effects of MEKi. Supporting results in ongoing experiments are expected to further our understanding of these mechanisms and may help inform effective combination treatment strategies for pediatric gliomas.

Centipeda minima and 6-O-angeloylplenolin enhance the efficacy of immune checkpoint inhibitors in non-small cell lung cancer

BackgroundChemotherapeutic agents including cisplatin, gemcitabine, and pemetrexed, significantly enhance the efficacy of immune checkpoint inhibitors (ICIs) in non-small cell lung cancer (NSCLC) by increasing PD-L1 expression and potentiating T cell cytotoxicity. However, the low response rate and adverse effects limit the application of chemotherapy/ICI combinations in patients. MethodsWe screened for medicinal herbs that could perturb PD-L1 expression and enhance T cell cytotoxicity in the presence of anti-PD-L1 antibody, and investigated the underlying mechanisms. ResultsWe found that the aqueous extracts of Centipeda minima (CM) significantly enhanced the cancer cell-killing activity and granzyme B expression level of CD8+ T cells, in the presence of anti-PD-L1 antibody. Both CM and its active component 6-O-angeloylplenolin (6-OAP) upregulated PD-L1 expression by suppressing GSK-3β-β-TRCP-mediated ubiquitination and degradation. CM and 6-OAP significantly enhanced ICI-induced reduction of tumor burden and prolongation of overall survival of mice bearing NSCLC cells, accompanied by upregulation of PD-L1 and increase of CD8+ T cell infiltration. CM also exhibited anti-NSCLC activity in cells and in a patient-derived xenograft mouse model. ConclusionsThese data demonstrated that the induced expression of PD-L1 and enhancement of CD8+ T cell cytotoxicity underlay the beneficial effects of 6-OAP-rich CM in NSCLCs, providing a clinically available and safe medicinal herb for combined use with ICIs to treat this deadly disease.