Downregulating PD-L1 Expression Research Articles

Enhancement of anti-PD-L1 antibody plus anlotinib efficacy due to downregulation of PD-L1 in the micro-conduit endothelium within the tumor: a randomized double-blind trial.

The possible enhancing effect of anlotinib on programmed death receptor ligand (PD-L1) antibody and the efficacy-predicting power of PD-L1 in micro-conduit endothelium, including lymphatic endothelial cells (LECs) and blood endothelial cells (BECs), were determined to identify patients who would benefit from this treatment. PD-L1 positivity in LECs, BECs, and tumor cells (TCs) was assessed using paraffin sections with multicolor immunofluorescence in an investigator's brochure clinical trial of TQB2450 (PD-L1 antibody) alone or in combination with anlotinib in patients with non-small cell lung cancer. Progression-free survival (PFS) with different levels of PD-L1 expression was compared between the two groups. Among 75 patients, the median PFS (mPFS) was longer in patients who received TQB2450 with anlotinib [10 and 12 mg (161 and 194 days, respectively)] than patients receiving TQB2450 alone (61 days) [hazard ratio (HR)10 mg = 0.390 (95% confidence interval {CI}, 0.201-0.756), P = 0.005; HR12 mg = 0.397 (0.208-0.756), P = 0.005]. The results were similar among 58 patients with high PD-L1 expression in LECs and TCs [159 and 209 vs. 82 days, HR10 mg = 0.445 (0.210-0.939), P = 0.034; HR12 mg = 0.369 (0.174-0.784), P = 0.009], and 53 patients with high PD-L1 expression in BECs and TCs [161 and 209 vs. 41 days, HR10 mg = 0.340 (0.156-0.742), P = 0.007; HR12 mg = 0.340 (0.159-0.727), P = 0.005]. No differences were detected in the mPFS between the TQB2450 and combination therapy groups in 13 low/no LEC-expressing and 18 low/no BEC-expressing PD-L1 cases. Mono-immunotherapy is not effective in patients with high PD-L1 expression in LECs and/or BECs. Anlotinib may increase efficacy by downregulating PD-L1 expression in LECs and/or BECs, which is presumed to be a feasible marker for screening the optimal immune patient population undergoing anti-angiogenic therapy.

MIIP downregulates PD-L1 expression through HDAC6 in cutaneous melanoma

PurposeImmune checkpoint inhibitors have improved the objective response rate and survival of melanoma patients. However, there are still many melanoma patients suffering from disease progression due to primary or secondary immune checkpoint inhibitor resistance, as is observed in the failure of anti-PD1/PD-L1 therapy. While the expression of valuable markers, such as TMB, MSI, and PD-L1, could serve as effective predictors of anti-checkpoint inhibitor therapies, tumor cell PD-L1 expression and its regulating mechanism would significantly affect the anti-PD-1 immunotherapy response and efficacy. Therefore, it is urgent to determine the function of PD-1/PD-L1 expression in melanoma and its associated pathways to enhance the efficacy of anti-PD-1 therapies.MethodsA cohort of 133 patients with histologically confirmed melanoma from Tianjin Medical University Cancer Institute & Hospital were included in this study. We performed immunohistochemical staining to detect the expression of Migration and invasion inhibitory protein (MIIP), HDAC6 and PD-L1. Kaplan–Meier and log-rank test were used for survival analysis. As for vitro, Western blot was used in melanoma cell lines to verify the signaling pathway that MIIP regulates PD-L1 expression.ResultsMIIP expression was decreased in melanoma and that the negative expression of MIIP was correlated with worse overall survival. The positive expression of HDAC6, a molecule that is downstream of MIIP, had a positive trend with decreased overall survival. At the same time, the positive expression of PD-L1, a crucial costimulatory molecule, was associated with decreased overall survival. Furthermore, there was a positive association between HDAC6 and PD-L1 protein expression (p < 0.01), and this correlation is more prominent in cutaneous melanoma than acral melanoma. In cutaneous melanoma cell lines, we found that increasing MIIP led to decreased HDAC6, pSTAT3, and PD-L1 expression. Knocking down MIIP led to increased HDAC6, pSTAT3, and PD-L1 expression. Combining the published results, showing that HDAC6 can regulate PD-L1 expression through STAT3, our present data suggest that MIIP inhibits the expression of PD-L1 by downregulating HDAC6 in melanoma. Most importantly, methods for targeting MIIP-HDAC6-PD-L1 pathways, such as treatment with HDAC6 inhibitors, might indicate a new therapeutic approach for enhancing immune checkpoint inhibitor therapies in melanoma.ConclusionsOur findings highlight the immunomodulatory effects of MIIP in the inhibition of PD-L1 expression by downregulating HDAC6 in melanoma. Methods for targeting MIIP-HDAC6-PD-L1 pathways might be new therapeutic approaches for enhancing immune checkpoint inhibitor therapies in melanoma.

Therapeutic targeting of thioredoxin reductase 1 causes ferroptosis while potentiating anti-PD-1 efficacy in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) faces low response rates to anti-PD-1 immunotherapies, highlighting the need for enhanced treatment strategies. Auranofin, which inhibits thioredoxin reductase (TrxR) through its gold-based composition, has shown potential in cancer treatment. It targets the TrxR system, essential for safeguarding cells from oxidative stress. The overproduction of TrxR in cancerous cells supports their proliferation. However, auranofin's interference with this system can upset the cellular redox equilibrium, boost levels of reactive oxygen species, and trigger the death of cancer cells. This study is the first to highlight TXNRD1 as a crucial factor contributing to resistance to anti-PD-1 treatment in HNSCC. In this study, we identified targetable regulators of resistance to immunotherapy-induced ferroptosis in HNSCC. We observed a link of thioredoxin reductase 1 (TXNRD1) with tumoral PD-L1 expression and ferroptosis suppression in HNSCC. Moreover, HNSCC tumors with aberrant TXNRD1 expression exhibited a lack of PD-1 response, NRF2 overexpression, and PD-L1 upregulation. TXNRD1 inhibition promoted ferroptosis in HNSCC cells with NRF2 activation and in organoid tumors derived from patients lacking a PD-1 response. Mechanistically, TXNRD1 regulated PD-L1 transcription and maintained the redox balance by binding to ribonucleotide reductase regulatory subunit M2 (RRM2). TXNRD1 expression disruption sensitized HNSCC cells to anti-PD-1–mediated Jurkat T-cell activation, promoting tumor killing through ferroptosis. Moreover, TXNRD1 inhibition through auranofin cotreatment synergized with anti-PD-1 therapy to potentiate immunotherapy-mediated ferroptosis by mediating CD8+ T-cell infiltration and downregulating PD-L1 expression. Our findings indicate that targeting TXNRD1 is a promising therapeutic strategy for improving immunotherapy outcomes in patients with HNSCC.

MiR-122-3p targets UBE2I to regulate the immunosuppression of liver cancer and the intervention of Liujunzi formula

Ethnopharmacological relevanceLiujunzi formula has been used to treat liver cancer in China for many years, but its underlying mechanism remains unclear. We previously found that decreased expression of miR-122-3p was associated with liver cancer. In this study, we aimed to explore the target of miR-122-3p and the effect of the Liujunzi formula on miR-122-3p and its downstream events in liver cancer. Material and methodsBioinformatics pinpointed potential targets of miR-122-3p. The actual target was confirmed by miRNA mimic/inhibitor transfections and a dual-luciferase reporter assay. RNA-seq looked at downstream genes impacted by this target. Flow cytometry checked for changes in T cell apoptosis levels after exposing them to liver cancer cells. Gene expression was measured by RT-qPCR, western blotting, and immunofluorescence staining. ResultsCell experiments found the Liujunzi extract (LJZ) upregulated miR-122-3p and in a dose-dependent manner. Bioinformatics analysis found UBE2I was a potential target of miR-122-3p, which was validated through experiments using miRNA mimics/inhibitors and a dual-luciferase reporter assay. RNA-seq data implicated the NF-κB pathway as being downstream of the miR-122-3p/UBE2I axis, further confirmed by forcing overexpression of UBE2I. Bioinformatic evidence suggested a link between UBE2I and T cell infiltration in liver cancer. Given that the NF-κB pathway drives PD-L1 expression, which can inhibit T cell infiltration, we investigated whether PD-L1 is a downstream effector of miR-122-3p/UBE2I. This was corroborated through mining public databases, UBE2I overexpression studies, and tumor-T cell co-culture assays. In addition, we also confirmed that LJZ downregulates UBE2I and NF-κB/PD-L1 pathways through miR-122-3p. LJZ also suppressed SUMOylation in liver cancer cells and protected PD-1+ T cells from apoptosis induced by co-culture with tumor cells. Strikingly, a miR-122-3p inhibitor abrogated LJZ's effects on UBE2I and PD-L1, and UBE2I overexpression rescued the LJZ-mediated effects on NF-κB and PD-L1. ConclusionsmiR-122-3p targets UBE2I, thereby suppressing the NF-κB signaling cascade and downregulating PD-L1 expression, which potentiates anti-tumor immune responses. LJZ bolsters anti-tumor immunity by modulating the miR-122-3p/UBE2I/NF-κB/PD-L1 axis in liver cancer cells.

Abstract 3160: PufA promotes proliferation, migration and tumorigenesis through NF-kB pathway in cholangiocarcinoma

Abstract Cholangiocarcinoma (CCA) exhibits a poor prognosis despite the recent advances in targeted therapy and immunotherapy. Therefore, exploring the novel mechanism of CCA tumorigenesis and identifying the effective targeted therapy is critical for advanced CCA to improve future treatment. A novel biogenesis factor of the 90S pre-ribosome named PufA, is higher expressed in tumors than normal tissue based on the TCGA databank implying the role of CCA tumorigenesis. Our results showed that PufA expression was significantly associated with larger tumor size, more lymph node metastasis, more tumor relapse, death, and unfavorable survivals in 205 patients with resectable CCA in Chang Gung Memorial Hospital. We demonstrated the inhibited effect of cell survival, migration ability, and the sphere-formation potential by silencing of PufA in CCA cell lines. Tumor growth is also suppressed in PufA knockdown xenograft mice. Mechanistic investigation showed that PufA was expression associated with nuclear factor kappa B p65 (RELA) activity and facilitated activity of the NF-κB transactivation. RELA, a transcription factor, is the principal regulator of the inflammatory response and is crucial for the homeostasis of the immune system and the expression of the immune checkpoint. Furthermore, decreased PufA levels also downregulated PD-L1 expression in CCA. Together, these findings suggested that the PufA-RELA axis could be a potential target for further application of targeted therapy in combination with immunotherapy. Citation Format: Chiao-Ping Chen, Chun-Nan Yeh, Yi-Ru Pan, Yu-Tien Hsiao, Chih-Hong Lo, Chia-Hsien Lin, Chiao-En Wu. PufA promotes proliferation, migration and tumorigenesis through NF-kB pathway in cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3160.

Targeting PHGDH reverses the immunosuppressive phenotype of tumor-associated macrophages through α-ketoglutarate and mTORC1 signaling

Phosphoglycerate dehydrogenase (PHGDH) has emerged as a crucial factor in macromolecule synthesis, neutralizing oxidative stress, and regulating methylation reactions in cancer cells, lymphocytes, and endothelial cells. However, the role of PHGDH in tumor-associated macrophages (TAMs) is poorly understood. Here, we found that the T helper 2 (Th2) cytokine interleukin-4 and tumor-conditioned media upregulate the expression of PHGDH in macrophages and promote immunosuppressive M2 macrophage activation and proliferation. Loss of PHGDH disrupts cellular metabolism and mitochondrial respiration, which are essential for immunosuppressive macrophages. Mechanistically, PHGDH-mediated serine biosynthesis promotes α-ketoglutarate production, which activates mTORC1 signaling and contributes to the maintenance of an M2-like macrophage phenotype in the tumor microenvironment. Genetic ablation of PHGDH in macrophages from tumor-bearing mice results in attenuated tumor growth, reduced TAM infiltration, a phenotypic shift of M2-like TAMs toward an M1-like phenotype, downregulated PD-L1 expression and enhanced antitumor T-cell immunity. Our study provides a strong basis for further exploration of PHGDH as a potential target to counteract TAM-mediated immunosuppression and hinder tumor progression.

A NRF2 Regulated and the Immunosuppressive Microenvironment Reversed Nanoplatform for Cholangiocarcinoma Photodynamic-Gas Therapy.

Photodynamic therapy (PDT) is a minimally invasive and controllable local cancer treatment for cholangiocarcinoma (CCA). However, the efficacy of PDT is hindered by intratumoral hypoxia and the presence of an antioxidant microenvironment. To address these limitations, combining PDT with gas therapy may be a promising strategy to enhance tumor oxygenation. Moreover, the augmentation of oxidative damage induced by PDT and gas therapy can be achieved by inhibiting NRF2, a core regulatory molecule involved in the antioxidant response. In this study, an integrated nanotherapeutic platform called CMArg@Lip, incorporating PDT and gas therapies using ROS-responsive liposomes encapsulating the photosensitizer Ce6, the NO gas-generating agent L-arginine, and the NRF2 inhibitor ML385, is successfully developed. The utilization of CMArg@Lip effectively deals with challenges posed by tumor hypoxia and antioxidant microenvironment, resulting in elevated levels of oxidative damage and subsequent induction of ferroptosis in CCA. Additionally, these findings suggest that CMArg@Lip exhibits notable immunomodulatory effects, including the promotion of immunogenic cell death and facilitation of dendritic cell maturation. Furthermore, it contributes to the anti-tumor function of cytotoxic T lymphocytes through the downregulation of PD-L1 expression in tumor cells and the activation of the STING signaling pathway in myeloid-derived suppressor cells, thereby reprogramming the immunosuppressive microenvironment via various mechanisms.

Nano-Regulator Inhibits Tumor Immune Escape via the "Two-Way Regulation" Epigenetic Therapy Strategy.

Tumor immune escape caused by low levels of tumor immunogenicity and immune checkpoint-dependent suppression limits the immunotherapeutic effect. Herein, a "two-way regulation" epigenetic therapeutic strategy is proposed using a novel nano-regulator that inhibits tumor immune escape by upregulating expression of tumor-associated antigens (TAAs) to improve immunogenicity and downregulating programmed cell death 1 ligand 1 (PD-L1) expression to block programmed death-1 (PD-1)/PD-L1. To engineer the nano-regulator, the DNA methyltransferase (DNMT) inhibitor zebularine (Zeb) and the bromodomain-containing protein 4 (BRD4) inhibitor JQ1 are co-loaded into the cationic liposomes with condensing the toll-like receptor 9 (TLR9) agonist cytosine-phosphate-guanine (CpG) via electrostatic interactions to obtain G-J/ZL. Then, asparagine-glycine-arginine (NGR) modified material carboxymethyl-chitosan (CMCS) is coated on the surface of G-J/ZL to construct CG-J/ZL. CG-J/ZL is shown to target tumor tissue and disassemble under the acidic tumor microenvironment (TME). Zeb upregulated TAAs expression to improve the immunogenicity; JQ1 inhibited PD-L1 expression to block immune checkpoint; CpG promote dendritic cell (DC) maturation and reactivated the ability of tumour-associated macrophages (TAM) to kill tumor cells. Taken together, these results demonstrate that the nano-regulator CG-J/ZL can upregulate TAAs expression to enhance T-cell infiltration and downregulate PD-L1 expression to improve the recognition of tumor cells by T-cells, representing a promising strategy to improve antitumor immune response.

Akkermansia muciniphila might improve anti-PD-1 therapy against HCC by changing host bile acid metabolism.

PD-1 monoclonal antibodies (mAb) have demonstrated remarkable efficacy in a variety of cancers, including Hepatocellular carcinoma (HCC). However, the patient response rates remain suboptimal, and a significant proportion of initial responders may develop resistance to this therapeutic approach. Akkermansia muciniphila (AKK), a microorganism implicated in multiple human diseases, has been reported to be more abundant in patients who exhibit favorable responses to PD-1mAb. However, the underlying mechanism has yet to be elucidated. In our study, we found that AKK could enhance the efficacy of PD-1mAb against HCC in a tumor-bearing mouse model. It promotes HCC tumor cells apoptosis and raise the CD8+ T proportion in the tumor microenvironment. Additionally, AKK downregulates PD-L1 expression in tumor cells. Furthermore, the analysis of metabonomics demonstrates that AKK induces alterations in the host's bile acid metabolism, leading to a significant increase in serum TUDCA levels. Considering the immunosuppresive roles of TUDCA in HCC development, it is plausible to speculate that AKK may reinforce the immunotherapy of PD-1mAb against HCC through its impact on bile acid metabolism.

Ki67-targeted oncolytic adenovirus expressing IL-15 improves intratumoral T cell infiltration and PD-L1 expression in glioblastoma

Glioblastoma (GBM) is a devastating malignant brain tumor. Current therapeutic strategies targeting tumor cells have limited efficacy owing to the immunosuppressive microenvironment. Previous work demonstrated that the targeted Ad5-Ki67/IL-15 could specifically kill tumor cells and decrease the angiogenic capacity in vitro. However, the efficacy of this virus in vivo and its effect on the tumor microenvironment (TME) has not been elucidated. In this study, we found that the Ad5-Ki67/IL-15 treatment down-regulated PD-L1 expression of glioma cells. More importantly, Ad5-Ki67/IL-15 also remodeled the tumor microenvironment via increasing intratumoral T cell infiltration and PD-L1 improvement in a GBM model, as well as the increase of antitumor cytokines, thereby improving the efficacy of GBM treatment. Furthermore, a combination of Ad5-Ki67/IL-15 with PD-L1 blockade significantly inhibits tumor growth in the GBM model. These results provide new insight into the therapeutic effects of targeted oncolytic Ad5-Ki67/IL-15 in patients with GBM, indicating potential clinical applications.

Cancer-associated Fibroblast-derived Extracellular Vesicles Mediate Immune Escape of Bladder Cancer via PD-L1/PD-1 Expression.

Bladder cancer (BCa) is a malignant urological tumor with a high prevalence and poor prognosis. Extracellular vesicles (EVs) are increasingly becoming current hotspots owing to their involvement in cancer progression. This paper probed into the action of cancer-associated fibroblast-derived EVs (CAF-EVs) in the immune escape of BCa. CAFs were identified by immunofluorescence. EVs were extracted from CAFs via ultracentrifugation and later characterized. BCa cells (T24 cell line) were co-cultured with CD8+ T cells and then treated with CAF-EVs. The uptake of EVs by T24 cells was examined by confocal laser microscopy. T24 cell apoptosis and invasion were assessed using flow cytometry and invasion assay. CD8+ T cell proliferation was evaluated using CFSE staining. The levels of cytokines (IFN-γ, IL-2, and TNF-α) were measured by ELISA. PD-L1 and PD-1 levels were determined utilizing RT-qPCR and flow cytometry. BCa mouse models were established to identify the effect of CAF-EVs on BCa progression in vivo. CAF-EVs decreased apoptosis and enhanced invasion of T24 cells, reduced proliferation of CD8+ T cells, and diminished levels of IFN-γ, IL-2, and TNF-α secreted by CD8+ T cells. CAF-EVs promoted the immune escape of T24 cells by carrying PD-L1. Downregulation of PDL1 expression in T24 cells or EVs partially counteracted the promotion of CAF-EVs on immune escape by reducing the binding of PD-L1 and PD-1. Additionally, CAF-EVs raised tumor volume and weight, upregulated PD-L1 expression, and weakened CD8+ T cell infiltration in BCa mice. CAF-EVs facilitate the immune escape of BCa by upregulating PD-L1/PD-1.

High-dose ascorbic acid potentiates immune modulation through STAT1 phosphorylation inhibition and negative regulation of PD-L1 in experimental sepsis.

Sepsis is a complex, multifactorial syndrome characterized by a dysregulated host response to infection, leading to severe organ dysfunction and high mortality rates among critically ill patients. Hypovitaminosis C and vitamin C deficiency are frequently observed in septic patients, prompting interest in the potential therapeutic role of ascorbic acid. Although intravenous administration of ascorbic acid has been investigated in multiple clinical trials for sepsis treatment, the specific immunomodulatory mechanisms underlying its effects remain elusive. This study aimed to investigate the protective effects of high-dose ascorbic acid on experimental sepsis. Results show that intravenous administration of high-dose ascorbic acid (250mg/kg) attenuated sepsis-induced organ dysfunctions in a cecal ligation and puncture (CLP)-induced septic mouse model. Ascorbic acid improved splenic cell apoptosis and increased the number of CD3+ T cells in septic mice induced by CLP. Furthermore, ascorbic acid downregulated PD-L1 expression in livers, reduced PD-1 expression in spleens, and inhibited the phosphorylation of STAT1 at Y701 in multiple organs of CLP-induced septic mice. The in vitro experiments also revealed that 800μM ascorbic acid suppressed STAT1 phosphorylation and inhibited lipopolysaccharide (LPS) and IFN-γ-induced PD-L1 expression in macrophages. These findings suggest that ascorbic acid prevents sepsis-associated organ dysfunction through the p-STAT1/PD-L1 signaling pathway. Our study provides new insights into the potential therapeutic use of ascorbic acid in sepsis.

Multi-omics analysis of human mesenchymal stem cells shows cell aging that alters immunomodulatory activity through the downregulation of PD-L1

Mesenchymal stem cells (MSCs) possess potent immunomodulatory activity and have been extensively investigated for their therapeutic potential in treating inflammatory disorders. However, the mechanisms underlying the immunosuppressive function of MSCs are not fully understood, hindering the development of standardized MSC-based therapies for clinical use. In this study, we profile the single-cell transcriptomes of MSCs isolated from adipose tissue (AD), bone marrow (BM), placental chorionic membrane (PM), and umbilical cord (UC). Our results demonstrate that MSCs undergo a progressive aging process and that the cellular senescence state influences their immunosuppressive activity by downregulating PD-L1 expression. Through integrated analysis of single-cell transcriptomic and proteomic data, we identify GATA2 as a regulator of MSC senescence and PD-L1 expression. Overall, our findings highlight the roles of cell aging and PD-L1 expression in modulating the immunosuppressive efficacy of MSCs and implicating perinatal MSC therapy for clinical applications in inflammatory disorders.

Sauchinone inhibits the proliferation and immune invasion capacity of colorectal cancer cells through the suppression of PD-L1 and MMP2/MM9.

Colorectal cancer (CRC) is one of the most common tumors globally and a leading cause of cancer-related death. In China, CRC is the third most common cancer type. Sauchinone is known to exhibit anti-tumor and anti-inflammatory activity, but its effects on CRC have not been investigated to-date Objective: To investigate the effects of Sauchinone on CRC development and metastasis and its underlying mechanism(s) of action. SW480 and HCT116 cells were treated with a range of concentrations of Sauchinone. Cell proliferation was measured using EDU assays and flow cytometry. Treatment with 50 µM Sauchinone decreased the expression of MMP2 and MMP9 and downregulated PD-L1 expression (PD-1/PD-L1) leading to checkpoint inhibition. Sauchinone treatment also enhanced the cytotoxicity of SW840 and HCT116 cells co-cultured with CD8+ T cells. The overexpression of PD-L1 rescued the anti-proliferative and cytotoxic effects of Sauchinone in both types. We show that Sauchinone suppresses CRC cell growth through the downregulation of MMP2 and MM9 expression and PD-1/PD-L1 mediated checkpoint inhibition. Collectively, these data highlight the promise of Sauchinone as a future anti-CRC therapeutic.

Synergistically enhanced cancer immunotherapy by combining protamine-based nanovaccine with PD-L1 gene silence nanoparticle

Tumor vaccine has brought a new dawn for cancer immunotherapy, but disillusionary therapeutic outcomes have been achieved due to the inefficient in vivo vaccine delivery. Moreover, tumor cells customarily resort to various wily tricks to circumvent the recognition and sweeping of the immune system, the immune escape effect has badly aggravated the difficulty of cancer management. With respect to the foregoing, in this study, a promising combinational strategy which cooperated nanovaccine with immune escape inhibition was developed for synergistically enhancing the oncotherapy efficiency. On the one hand, natural polycationic macromolecule protamine (PRT) was utilized as the carrier to construct an antigen and adjuvant co-packaged nanovaccine for facilitating the ingestion in antigen-presenting cells, amplifying antigen cross-presentation and optimizing in vivo delivery. On the other hand, PD-L1 silence gene was selected and hitchhiked in a pH-responsive nanoparticle developed in our previous study. The therapeutic gene could be successfully delivered into the tumors to down-regulate PD-L1 expression and cripple tumor immune escape. The combination of nanovaccine with PD-L1 gene silence nanoparticle could synchronously stimulate antitumor immune responses and reduce immune escape, synergistically enhance the therapeutic efficiency. This study will furnish the prospective tactics for the research of cancer immunotherapy.

Self-Degradable Nanogels Reshape Immunosuppressive Tumor Microenvironment via Drug Repurposing Strategy to Reactivate Cytotoxic CD8+ T Cells.

Intratumoral CD8+ T cells are crucial for effective cancer immunotherapy, but an immunosuppressive tumor microenvironment (TME) contributes to dysfunction and insufficient infiltration. Drug repurposing has successfully led to new discoveries among existing clinical drugs for use as immune modulators to ameliorate immunosuppression in TME and reactivate T-cell-mediated antitumor immunity. However, due to suboptimal tumor bioavailability, the full potential of immunomodulatory effects of these old drugs has not been realized. The self-degradable PMI nanogels carrying two repurposed immune modulators, imiquimod (Imi) and metformin (Met), are reported for TME-responsive drug release. It remodels the TME through the following aspects: 1) promoting dendritic cells maturation, 2) repolarizing M2-like tumor-associated macrophages, and 3) downregulating PD-L1 expression. Ultimately, PMI nanogels reshaped the immunosuppressive TME and efficiently promote CD8+ T cell infiltration and activation. These results support that PMI nanogels can potentially be an effective combination drug for enhancing the antitumor immune response of anti-PD-1 antibodies.

Silencing of RAB42 down-regulated PD-L1 expression to inhibit the immune escape of hepatocellular carcinoma cells through inhibiting the E2F signaling pathway

ObjectiveTo investigate the mechanistic role of RAB42 and corresponding regulatory path in hepatocellular carcinoma (HCC). MethodsThe expression of RAB42 in HCC tissue was checked by RT-qPCR and immunohistochemical staining assay. Cell proliferation was checked by colony formation and CCK-8 assay. Cell apoptosis and cycle distribution were analyzed with flow cytometry. The relevance of RAB42 and PD-L1 was analyzed from TCGA database. The binding of E2F1 to PD-L1 was detected by JASPAR database, luciferase and ChIP assay. The expression of PD-L1, cell apoptosis- and E2F pathway-related proteins were checked by western blotting. ResultsRAB42 was highly expressed in HCC tissue. RAB42 silencing could inhibit proliferation and induce G1 phase arrest and apoptosis of HCC cells. TCGA database disclosed that PD-L1 was highly associated with RAB42 expression. Silencing of RAB42 could retard PD-L1 expression in HCC cells. GSEA analysis showed RAB42 could activate E2F signaling pathway. Silencing of RAB42 could observably weaken the expression of E2F1, CDK1 and CDC20 in HCC cells. JASPAR database predicted the binding site between E2F1 and PD-L1, and E2F1 overexpression could promote PD-L1 expression. Overexpression of E2F1 could reverse the biological function of RAB42 silencing in HCC cells. ConclusionSilencing of RAB42 could down-regulate PD-L1 expression to inhibit immune escape through inhibiting E2F signaling pathway in HCC cells. RAB42 may become a novel clinical diagnostic and therapy marker for HCC.

Normalization of Tumor Vessels by Lenvatinib-Based Metallo-Nanodrugs Alleviates Hypoxia and Enhances Calreticulin-Mediated Immune Responses in Orthotopic HCC and Organoids.

Immunocheckpoint inhibitors combined with Lenvatinib is the first line treatment for hepatocellular carcinoma (HCC), but their potency is hampered by the low response rate and adverse events. Herein, a targeted therapeutic strategy through the coassembly of Lenvatinib, Adriamycin, Fe3+ ion, and a natural polyphenol (metallo-nanodrugs) is presented by coordination effect for potentiating tumor vascular normalization and systematic chemo-immunotherapy to effectively inhibit the progression of HCC in both orthotopic model and patients-derived organoids. In mice with orthotopic HCC, the obtained metallo-nanodrugs efficiently increase the drug accumulation in orthotopic tumors and can respond to acidic tumor environment. The promotion of tumor vascular normalization by metallo-nanodrugs is observed, which enhances the infiltrating T lymphocytes in tumor, and reinforces the calreticulin-mediated antitumor immunity through alleviating hypoxia, reducing regulatory T cells, and down-regulating PDL1 expression of tumors. The excellent therapeutic efficiency with complete remission of orthotopic tumors (3/6) and long-term survival of mice (4/6, 42 days) are also achieved. Furthermore, the excellent therapeutic effect of metallo-nanodrugs is also validated in 5 patient-derived organoids, and hence can provide a marvelous systemic chemo-immunotherapy strategy for enhancing HCC treatment.

Abstract 6636: Metformin suppresses tumor immune evasion through downregulation of PD-L1 expression in cancer cells and PD-1 expression in NK cells and T cells

Abstract Up-regulation of programmed cell death 1 (PD-1) receptor on T cells and its ligand (PD-L1) on cancer cells is reported in various tumor microenvironment, and the interaction between PD-L1 and PD-1 inhibits the cytotoxic activity of NK cells and T cells, allowing cancer cells to evade immune destruction. Extensive studies suggested that metformin, the most widely used first-line drug for treatment of type 2 diabetes, had a potential efficacy of enhancing anti-tumor immune response. However, the detail mechanisms underlying the efficacy are unknown. Here, we showed that metformin decreases AKT-mediated β-catenin S552 phosphorylation and β-catenin transactivation in an AMPK activation-dependent manner, resulting in reduced CD274 transcription in cancer cells. In the cocultures of cancer cells with NK cells or T cells, cancer cells induced PD-1 protein stability and expression in the NK cells and T cells, these PD-1 upregulation was also observed in infiltrated NK cells and T cells in vivo mouse tumors. Metformin reduced the half-life and expression of PD-1 in an AMPK activation-dependent manner in vitro and in vivo. These inhibitory roles of metformin in PD-L1 expression in cancer cells and in cancer cell-induced PD-1 expression in NK cells and T cells led to ameliorated the cancer cell-reduced cytotoxic activity of NK cells and T cells and inhibited tumor growth in vivo models. These findings suggest that metformin may act as both PD-L1 and PD-1 blockades within tumor microenvironment, providing a mechanistic insight for the efficacy of metformin to improve immunotherapy in human cancer. Citation Format: Su Hwan Park, Jong-Ho Lee. Metformin suppresses tumor immune evasion through downregulation of PD-L1 expression in cancer cells and PD-1 expression in NK cells and T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6636.

Interaction between PD-L1 and soluble VEGFR1 in glioblastoma-educated macrophages

PurposeThe combined application of immune checkpoint inhibitors (ICIs) and anti-angiogenesis therapy has shown synergistic effects on glioblastoma (GBM). As important resources of PD-L1 in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) have significant impact of the efficiency of ICIs. However, the effects of anti-angiogenesis agents on immune checkpoints expression are not fully understood.MethodGBM-educated macrophages were generated from circulating monocytes of healthy controls and GBM patients under the education of GBM cell line. Surface expression of PD-L1 and VEGFR1 on GBM-educated macrophages was analyzed. VEGFR1 NAb and soluble VEGFR1 (sVEGFR1) were added and their effects on PD-L1 expression on TAMs was investigated. Serum soluble PD-L1 (sPD-L1) and sVEGFR1 levels in GBM patients were measured and their correlation was analyzed.ResultThe expression intensity of PD-L1 on GBM-educated macrophages was higher and its up-regulation partially depends on VEGFR1 signaling pathway. GBM-educated macrophages secreted less levels of soluble VEGFR1 (sVEGFR1), and exogenous sVEGFR1 down-regulated PD-L1 expression intensity. PD-L1 blockade promoted the secretion of sVEGFR1. Finally, sVEGFR1 and sPD-L1 in serum of GBM patients were overexpressed, and a positive correlation was found.ConclusionThese findings reveal the interaction between PD-L1 and VEGFR1 signaling pathway in GBM-educated macrophages. VEGFR1 is involved with PD-L1 overexpression, which can be impeded by autocrine regulation of sVEGFR1. sVEGFR1 secretion by GBM-educated macrophages can be promoted by PD-L1 blockade. Taken together, these findings provide evidences for the combined application of ICIs and anti-angiogenesis therapies in the treatment of GBM.