Targeting Myeloid-derived Suppressor Cells Research Articles

Rg3-lipo biomimetic delivery of paclitaxel enhances targeting of tumors and myeloid-derived suppressor cells.

Liposomal drug delivery systems have revolutionized traditional cytotoxic drugs. However, the relative instability and toxicity of the existing liposomal drug delivery systems compromised their efficacy. Herein, we present Rg3-lipo, an innovative drug delivery system using a glycosyl moiety-enriched ginsenoside (Rg3). This system is distinguished by its glycosyl moieties exposed on the liposomal surface. These moieties imitate human cell membranes to stabilize and evade phagocytic clearance. The Rg3-lipo system loaded with paclitaxel (PTX-Rg3-lipo) demonstrated favorable bioavailability and safety in Sprague-Dawley rats, beagle dogs, and cynomolgus monkeys. With its glycosyl moieties recognizing tumor cells via the glucose transporter Glut1, PTX-Rg3-lipo inhibited gastric, breast, and esophageal cancers in human cancer cell lines, tumor-bearing mice, and patient-derived xenograft models. These glycosyl moieties selectively targeted myeloid-derived suppressor cells (MDSCs) through the glucose transporter Glut3 to attenuate their immunosuppressive effect. The mechanism study revealed that Rg3-lipo suppressed glycolysis and downregulated the transcription factors c-Maf and Mafb overcoming the MDSC-mediated immunosuppressive microenvironment and enhancing PTX-Rg3-lipo's antitumor effect. Taken together, we supply substantial evidence for its advantageous bioavailability and safety in multiple animal models, including nonhuman primates, and Rg3-lipo's dual targeting of cancer cells and MDSCs. Further investigation regarding Rg3-lipo's druggability will be conducted in clinical trials.

Myeloid-Derived Suppressor Cells in Bladder Cancer: An Emerging Target.

Bladder cancer remains a prevalent and challenging malignancy. Myeloid-derived suppressor cells (MDSCs) have emerged as key contributors to the immunosuppressive tumor microenvironment, facilitating tumor progression, immune evasion, and resistance to therapies. This review explores the role of MDSC in bladder cancer, highlighting their involvement in immune regulation; tumor progression; and resistance to therapies such as bacillus Calmette-Guérin (BCG) therapy, chemotherapy, and immune checkpoint inhibitors (ICIs). We also discuss their potential as biomarkers and therapeutic targets, with current evidence suggesting that targeting MDSCs, either alone or in combination with existing treatments such as BCG and ICIs, may enhance anti-tumor immunity and improve clinical outcomes. However,, challenges remain, particularly regarding the identification and therapeutic modulation of MDSC subpopulations. Further research is warranted to fully elucidate their role in bladder cancer and to optimize MDSC-targeted therapies.

Immune modulation and epigenetic therapies for enhanced outcome of treatment in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by the absence of human epidermal growth factor receptor 2, estrogen receptor, and progesterone receptor expression. While traditional TNBC treatment primarily relies on systemic chemotherapy, epigenetic modification has an important role in immune evasion and tumor progression. Recent classifications of TNBC into “hot” and “cold” tumors, based on immune activity and mutation burden, have revealed that poor response to immune checkpoint inhibitors (ICIs) in these tumors is due to low tumor-infiltrating lymphocytes and the presence of immunosuppressive cells. Emerging treatments such as ICIs and poly(ADP-ribose) polymerase inhibitors offer promising alternatives. The tumor microenvironment (TME) shapes immune responses in TNBC, and a limited subset of patients has shown encouraging responses to ICIs in treating TNBC at both early and advanced stages. However, combination therapies face challenges, including medication interactions and side effects. Epigenetic modulators, such as histone deacetylase and DNA methyltransferase inhibitors, also show promise in reversing epigenetic changes by enhancing anti-tumor immunity in TNBC. The frequent expression of indoleamine 2,3-dioxygenase 1 (IDO1) in TNBC, which catalyzes the conversion of tryptophan to kynurenine, contributes to immune suppression in TNBC patients. High IDO1 levels impair the tumoricidal activity of natural killer cells and correlate with poor responses to anti-PD-L1 therapy, which can be improved using IDO1 inhibitors. Targeting myeloid-derived suppressor cells, regulatory T-cells, and tumor-associated macrophage, along with utilizing epigenetic mechanisms, show promise in modulating the immunosuppressive TME in TNBC. Combining these approaches with standard therapies, along with biomarker-guided patient selection, can enhance treatment efficacy. Clinical trials and preclinical models are essential for optimizing these strategies. This study emphasizes the importance of understanding the mechanisms of modulation, tumor-immune interactions, and the potential of epigenetic therapies in improving treatment outcomes in TNBC.

Targeting Myeloid-Derived Suppressor Cells via Dual-Antibody Fluorescent Nanodiamond Conjugate.

Fluorescent nanodiamonds (FNDs) are carbon-based nanomaterials that emit bright, photostable fluorescence and exhibit a modifiable surface chemistry. Myeloid-derived suppressor cells (MDSCs) are an immunosuppressive cell population known to expand in cancer patients and contribute to worse patient outcomes. To target MDSC, glycidol-coated FND were conjugated with antibodies against the murine MDSC markers, CD11b and GR1 (dual-Ab FND). In vitro, dual-Ab FND uptake by murine MDSC was significantly higher than IgG-coated FND (94.7% vs. 69.0%, p < 0.05). In vivo, intra-tumorally injected dual-Ab FND primarily localized to the tumor 2 and 24 h post-injection, as measured by in vivo fluorescence imaging and flow cytometry analysis of the spleen and tumor. Dual-Ab FND were preferentially taken up by intra-tumoral MDSC, representing 87.1% and 83.0% of FND+ cells in the tumor 2 and 24 h post-injection, respectively. Treatment of mice with anti-PD-L1 immunotherapy prior to intra-tumoral injection of dual-Ab FND did not significantly alter the uptake of FND by MDSC. These results demonstrate the ability of our novel dual-antibody conjugated FND to target MDSC and reveal a potential strategy for targeted delivery to other specific immune cell populations in future cancer research.

Regulatory effect of rapamycin on recruitment and function of myeloid-derived suppressor cells in heart failure

BackgroundImmune response and inflammation play important roles in the physiological and pathophysiological processes of heart failure (HF). In our previous study, myeloid-derived suppressor cells (MDSCs), a heterogeneous group of immature myeloid cells with anti-inflammatory and immunosuppressive functions, were shown to exert cardioprotective effects in HF. The pharmacological targeting of MDSCs using rapamycin may emerge as a promising strategy for the prevention and treatment of HF. However, the specific mechanisms underlying rapamycin-induced MDSC accumulation remain unclear. Our study aimed to clarify the effects of rapamycin on the recruitment and function of MDSCs in HF, exploring new therapeutic options for the prevention and treatment of HF. MethodsWe used transverse aortic constriction surgery and isoproterenol injection to establish HF models. Flow cytometry, reverse transcription polymerase chain reaction, transcriptomics and western blot were used to explore the regulation of rapamycin on recruitment and function of MDSCs in HF. Furthermore, rapamycin and granulocyte–macrophage colony-stimulating factor (GM-CSF) were combined to induce exogenous MDSCs from bone marrow cells. ResultsRapamycin promotes the recruitment of MDSCs by inhibiting their maturation and differentiation via suppression of the Wnt signaling in HF mice and enhanced the immunosuppressive function of MDSCs via the NF-κB signaling. Furthermore, exogenous MDSCs induced by rapamycin and GM-CSF can significantly alleviate transverse aortic constriction-induced cardiac dysfunction. ConclusionsThe pharmacological targeting of MDSCs using rapamycin is a promising strategy for the prevention and treatment of HF.

Targeting myeloid-derived suppressor cells promotes antiparasitic T-cell immunity and enhances the efficacy of PD-1 blockade

Immune exhaustion corresponds to a loss of effector function of T cells that associates with cancer or chronic infection. Here, our objective was to decipher the mechanisms involved in the immune suppression of myeloid-derived suppressor cells (MDSCs) and to explore the potential to target these cells for immunotherapy to enhance checkpoint blockade efficacy in a chronic parasite infection. We demonstrated that programmed cell-death-1 (PD-1) expression was significantly upregulated and associated with T-cell dysfunction in advanced alveolar echinococcosis (AE) patients and in Echinococcus multilocularis-infected mice. PD-1 blockade ex vivo failed to reverse AE patients’ peripheral blood T-cell dysfunction. PD-1/PD-L1 blockade or PD-1 deficiency had no significant effects on metacestode in mouse model. This was due to the inhibitory capacities of immunosuppressive granulocytic MDSCs (G-MDSCs), especially in the liver surrounding the parasite pseudotumor. MDSCs suppressed T-cell function in vitro in an indoleamine 2, 3 dioxygenase 1 (IDO1)-dependent manner. Although depleting MDSCs alone restored T-cell effector functions and led to some limitation of disease progression in E. multilocularis-infected mice, combination with PD-1 blockade was better to induce antiparasitic efficacy. Our findings provide preclinical evidence in support of targeting MDSC or combining such an approach with checkpoint blockade in patients with advanced AE.

Targeting myeloid-derived suppressor cells by inhibiting hypoxia-inducible factor 1α could improve tumor progression.

Myeloid-derived suppressor cells (MDSCs) are a subset of immature myeloid cells that inhibit anti-tumor immunity and contribute to poor cancer outcomes. In this study, the authors used multi-color flow cytometry to detect changes in MDSCs in patients with cancer and tumor-bearing mice. Then the authors studied changes in MDSCs ratio and mouse tumors after administration of hypoxia-inducible factor 1α (HIF-1α) inhibitor. The results showed that the ratio of MDSCs, specifically polymorphonuclear MDSCs (PMN-MDSCs), was higher in patients with cancer, and both PMN-MDSCs and monocytic MDSCs (M-MDSCs) ratio were higher in tumor-bearing mice. When provided with the HIF-1α inhibitor LW-6, the ratio of MDSCs decreased in tumor-bearing mice, particularly PMN-MDSCs, and the volume of liver metastases also decreased. The authors' findings suggest that reducing MDSCs by inhibiting hypoxia-inducible factor 1α may slow tumor progression.

Sequence of androgen receptor-targeted vaccination with androgen deprivation therapy affects anti-prostate tumor efficacy

RationaleAndrogen deprivation therapy (ADT) is the primary treatment for recurrent and metastatic prostate cancer. In addition to direct antitumor effects, ADT has immunomodulatory effects such as promoting T-cell infiltration and...

Abstract 6345: In vitro characterization of a dual antagonistic anti-LILRB2/LILRB4 monoclonal antibody

Abstract Introduction: Myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment are a potential therapeutic target in immune checkpoint cancer therapy, but MDSC-targeted therapies have yet been shown to improve survival. The leukocyte immunoglobulin (Ig)-like receptor B2 is a member of the leukocyte Ig-like receptor (LILR) family and is predominantly expressed on the surface of cells of the myelomonocytic lineage (monocytes, macrophages and dendritic cells). LILRB2 is a negative regulator of myeloid cells and is an immune checkpoint receptor. We chose to generate mAbs against LILRB2 as a potential immunotherapeutic for cancer. Methods: PentaMice® strains (5 WT mouse strains comprising 9 MHC class II haplotypes to maximize Ab diversity) were immunized with human LILRB2. Lymphocytes were fused with a myeloma partner to generate lead monoclonal hybridomas. 24 purified anti-LILRB2 mAbs were generated and evaluated by arrayed surface plasma resonance (SPR, Carterra® LSA® instrument) to assign epitope bins. mAb humanization was performed in silico to maximize T20 “humanness” scores (algorithm developed by Curia). Humanized mAbs were transiently expressed using Curia’s TunaCHO™ platform and tested in in vitro MDSC assays. Autologous co-cultures of magnetic bead enriched-human blood-derived MDSC (HLA-DR-CD14+) model cells and T cells (CD3+) were stimulated with plate-bound anti-CD3/CD28 to induce T cell activation. Cytokine secretion was assessed 4 days later. Results: A total of 384 hybridoma supernatants were selected from the primary screen. 245 were confirmed by ELISA and 178 stained HEK293 cells expressing LILRB2 cells by flow cytometry (FACS). 24 hybridomas were further selected, cloned and sequenced. Five epitope bins were identified via Carterra® LSA® instrument. Two clones were chosen for humanization, designated 6-I11A and 4-O19A and were recombinantly expressed with the human IgG4 isotype. FACS analysis on HEK293 cells expressing either huLILRB2 or huLILRB4 revealed that clone hu4-O19A-IgG4 was specific for huLILRB2. Surprisingly, clone hu6-I11A-IgG4 stained both huLILRB2 and huLILRB4. FACS analysis with hu4-O19A-IgG4 on human MDSCs exhibited an EC50 of 11.9 nM and a KD of 1.5 nM in binding to recombinant huLILRB2 antigen, while hu6-I11A-IgG4 had an EC50 of 3.2 nM and a KD of 0.6 nM. In co-cultures with human MDSCs and T cells, both hu6-I11A-IgG4 and hu4-O19A-IgG4 reversed cytokine suppression by the MDSCs by increasing GM-CSF, IL-10, TNFα, and IL-6, while suppressing IL-13, and had little effect on IL-17A, MIP-3α, IL-4, IL-2 and IFNγ compared to treatment with the isotype control, with hu6-I11A-IgG4 having a greater effect as an antagonist than hu4-O19A-IgG4. Conclusions: We have identified a dual anti-LILRB2/LILRB4 antagonist. Targeting MDSCs with this antibody offers great promise for immunotherapy for cancer as well as its immense potential for synergy with PD-1 blockade. Citation Format: Bruce L. Daugherty, Xiaomei Ge, Christine L. Hsieh, Brian A. Zabel, Seth Lederman. In vitro characterization of a dual antagonistic anti-LILRB2/LILRB4 monoclonal antibody [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 6345.

MCL1 inhibition targets Myeloid Derived Suppressors Cells, promotes antitumor immunity and enhances the efficacy of immune checkpoint blockade

Immune checkpoint inhibitors (ICIs) are now the first-line treatment for patients with advanced melanoma. Despite promising clinical results, many patients fail to respond to these therapies. BH3 mimetics, a novel class of small molecule inhibitors that bind and inhibit anti-apoptotic members of the BCL2 family proteins such as BCL2 or MCL1, have been very successful in treating hematologic malignancies. However, there are limited studies on the immunomodulatory role of the BH3 mimetics. Several factors contribute to ICI resistance including myeloid-derived suppressor cells (MDSCs) that exert immunosuppressive effects through direct and indirect inhibition of antitumor immunity. Thus, targeting MDSCs to enhance antitumor immunity has the potential to enhance the efficacy of ICIs. In this study, we show that the MCL1 inhibitor S64315 reduces melanoma tumor growth in an immune cell-dependent manner in mice. Specifically, S64315 enhances antitumor immunity by reducing MDSC frequency and by promoting the activity of CD8+T cells. Additionally, human MDSCs are 10 times more sensitive to S64315 than cutaneous melanoma lines. Further, we found that a higher expression of MCL1 is associated with poor survival for patients treated with anti-PD-1. Finally, combining S64315 and anti-PD-1 significantly slowed tumor growth compared to either agent alone. Together, this proof-of-concept study demonstrates the potential of combining an MCL1 inhibitor with anti-PD-1 in the treatment of melanoma. It justifies the further development of next generation MCL1 inhibitors to improve efficacy of ICIs in treating malignant melanoma.

MDSC-targeted liposomal all-trans retinoic acid suppresses mMdscs and improves immunotherapy in HBV infection

ABSTRACT Background Myeloid-derived suppressor cells (MDSCs) are evolving as a prominent determinant in cancer occurrence and development and are functionally found to suppress T cells in cancer. Not much research is done regarding its involvement in viral infections. This research was designed to investigate the role of MDSCs in hepatitis B virus (HBV) infection and how targeting these cells with our novel all-trans retinoic acid encapsulated liposomal formulation could improve immunotherapy in C57BL/6 mice. Methods Ten micrograms (10 μg) of plasmid adeno-associated virus (pAAV/HBV 1.2, genotype A) was injected hydrodynamically via the tail vein of C57BL/6 mice. An all-trans retinoic acid encapsulated liposomal formulation (L-ATRA) with sustained release properties was used in combination with tenofovir disoproxil fumarate (TDF), a nucleotide analog reverse transcriptase inhibitor (nRTI) to treat the HBV infection. The L-ATRA formulation was given at a dose of 5 mg/kg intravenously (IV) twice a week. The TDF was given orally at 30 mg/kg daily. Results Our results revealed that L-ATRA suppresses MDSCs in HBV infected mice and enhanced T-cell proliferation in vitro. In vivo studies showed higher and improved immunotherapeutic effect in mice that received L-ATRA and TDF concurrently in comparison with the groups that received monotherapy. Lower HBV DNA copies, lower concentrations of HBsAg and HBeAg, lower levels of ALT and AST and less liver damage were seen in the mice that received the combination therapy of L-ATRA + TDF. Conclusions In effect, targeting MDSCs with the combination of L-ATRA and TDF effectively reduced mMDSC and improved immunotherapy in the HBV infected mice. Targeting MDSCs could provide a breakthrough in the fight against hepatitis B virus infection.

Nanomedicine Targeting Myeloid-Derived Suppressor Cells Enhances Anti-Tumor Immunity.

Cancer immunotherapy, a field within immunology that aims to enhance the host's anti-cancer immune response, frequently encounters challenges associated with suboptimal response rates. The presence of myeloid-derived suppressor cells (MDSCs), crucial constituents of the tumor microenvironment (TME), exacerbates this issue by fostering immunosuppression and impeding T cell differentiation and maturation. Consequently, targeting MDSCs has emerged as crucial for immunotherapy aimed at enhancing anti-tumor responses. The development of nanomedicines specifically designed to target MDSCs aims to improve the effectiveness of immunotherapy by transforming immunosuppressive tumors into ones more responsive to immune intervention. This review provides a detailed overview of MDSCs in the TME and current strategies targeting these cells. Also the benefits of nanoparticle-assisted drug delivery systems, including design flexibility, efficient drug loading, and protection against enzymatic degradation, are highlighted. It summarizes advances in nanomedicine targeting MDSCs, covering enhanced treatment efficacy, safety, and modulation of the TME, laying the groundwork for more potent cancer immunotherapy.

Abstract A031: Biotherapeutic strategies targeting the CXCR2 axis for depletion of myeloid-derived suppressor cells in pancreatic ductal adenocarcinoma

Abstract Pancreatic Ductal Adenocarcinoma (PDAC) has a 5-year survival rate of only 10%, and limited treatment options exist. Immune checkpoint inhibitors are effective in a variety of cancer types; however, the complex immunosuppressive tumor microenvironment (TME) of PDAC is a significant barrier to immunotherapy. Myeloid-derived suppressor cells (MDSCs) are abundant in PDAC tumors from humans and mouse models. MDSCs suppress effector T cell function and promote the expansion of other immunosuppressive cell types. This led us to hypothesize that targeting tumor MDSCs would be an effective therapeutic strategy for PDAC and enhance the efficacy of T cell based immunotherapy. Our preliminary data and the work from others shows that CXCR2 ligands such as CXCL8/IL-8, CXCL5/ENA78, and CXCL1/GROα are the most abundant soluble factors secreted by PDAC cells. CXCR2 ligands are critical for the homing of myeloid cells to sites of injury in cutaneous wound healing, suggesting that dysregulated secretion of CXCR2 chemokines in PDAC may mimic a wound healing response that attracts myeloid cells and promotes the expansion of MDSCs and an immunosuppressive TME. To test this hypothesis, we have designed and produced multiple drug-conjugated CXCR2 ligand-based engineered proteins to target and eliminate MDSCs from PDAC tumors. We are referring to these novel biotherapeutic molecules as Ligand Drug Conjugates (LDCs). We have demonstrated binding, internalization, induction of signaling, and cytotoxicity of these LDCs to CXCR2 expressing myeloid cells. Our data suggests that our engineered proteins are superior binders and activators of CXCR2 axis signaling compared to WT CXCR2 ligands. Utilizing CXCR2 knockin models we demonstrated that the cytotoxicity of our LDCs is CXCR2 dependent. In vivo, we are utilizing the KPC (LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre) mouse model of PDAC, which we've shown in preliminary studies to, like human PDAC, support an abundance of MDSCs in tumors as well as secondary lymphoid organs such as the spleen. We anticipate that this study will demonstrate the therapeutic potential and actionability of targeting MDSCs and will provide novel biotherapeutic drug candidates that will ultimately improve immunotherapy outcomes in patients with PDAC. Citation Format: Benjamin N. Christopher, Lety Reyes, Reeder Robinson, Lena Golick, Nathan Dolloff. Biotherapeutic strategies targeting the CXCR2 axis for depletion of myeloid-derived suppressor cells in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A031.

Targeting myeloid-derived suppressor cells in the tumor microenvironment: potential therapeutic approaches for osteosarcoma

Targeting myeloid-derived suppressor cells in the tumor microenvironment: potential therapeutic approaches for osteosarcoma

Targeting myeloid-derived suppressor cells with gemcitabine to enhance efficacy of adoptive cell therapy in bladder cancer.

New therapeutics in development for bladder cancer need to address the recalcitrant nature of the disease. Intravesical adoptive cell therapy (ACT) with tumor infiltrating lymphocytes (TIL) can potentially induce durable responses in bladder cancer while maximizing T cells at the tumor site. T cells infused into the bladder directly encounter immunosuppressive populations, such as myeloid derived suppressor cells (MDSCs), that can attenuate T cell responses. Intravesical instillation of gemcitabine can be used as a lymphodepleting agent to precondition the bladder microenvironment for infused T cell products. Urine samples from bladder cancer patients and healthy donors were analyzed by flow cytometry and cytometric bead array for immune profiling and cytokine quantification. MDSCs were isolated from the urine and cocultured with stimulated T cells to assess effects on proliferation. An orthotopic murine model of bladder cancer was established using the MB49-OVA cell line and immune profiling was performed. MDSCs from tumor-bearing mice were cocultured with OT-I splenocytes to assess T cell proliferation. Mice received intravesical instillation of gemcitabine and depletion of immune cells was measured via flow cytometry. Bladder tumor growth of mice treated with intravesical gemcitabine, OT-I transgenic T cells, or combination was monitored via ultrasound measurement. In comparison to healthy donors, urine specimen from bladder cancer patients show high levels of MDSCs and cytokines associated with myeloid chemotaxis, T cell chemotaxis, and inflammation. T cells isolated from healthy donors were less proliferative when cocultured with MDSCs from the urine. Orthotopic murine bladder tumors also presented with high levels of MDSCs along with enrichment of cytokines found in the patient urine samples. MDSCs isolated from spleens of tumor-bearing mice exerted suppressive effects on the proliferation of OT-I T cells. Intravesical instillation of gemcitabine reduced overall immune cells, MDSCs, and T cells in orthotopic bladder tumors. Combination treatment with gemcitabine and OT-I T cells resulted in sustained anti-tumor responses in comparison to monotherapy treatments. MDSCs are enriched within the microenvironment of bladder tumors and are suppressive to T cells. Gemcitabine can be used to lymphodeplete bladder tumors and precondition the microenvironment for intravesical ACT.

CUL4B functions as a tumor suppressor in KRAS-driven lung tumors by inhibiting the recruitment of myeloid-derived suppressor cells.

Lung cancer is the leading cause of cancer-related death worldwide. KRAS mutations are the most common oncogenic alterations found in lung cancer. Unfortunately, treating KRAS-mutant lung adenocarcinoma (ADC) remains a major oncotherapeutic challenge. Here, we used both autochthonous and transplantable KRAS-mutant tumor models to investigate the role of tumor-derived CUL4B in KRAS-driven lung cancers. We showed that knockout or knockdown of CUL4B promotes lung ADC growth and progression in both models. Mechanistically, CUL4B directly binds to the promoter of Cxcl2 and epigenetically represses its transcription. CUL4B deletion increases the expression of CXCL2, which binds to CXCR2 on myeloid-derived suppressor cells (MDSCs) and promotes their migration to the tumor microenvironment. Targeting of MDSCs significantly delayed the growth of CUL4B knockdown KRAS-mutant tumors. Collectively, our study provides mechanistic insights into the novel tumor suppressor-like functions of CUL4B in regulating KRAS-driven lung tumor development.

Epigenetic targeting of myeloid-derived suppressor cells: time to move into infectious diseases?

Epigenetic targeting of myeloid-derived suppressor cells: time to move into infectious diseases?

Janus Silica Nanoparticle-Based Tumor Microenvironment Modulator for Restoring Tumor Sensitivity to Programmed Cell Death Ligand 1 Immune Checkpoint Blockade Therapy.

An immunosuppressive tumor microenvironment (TME) with inadequate and exhausted tumor-infiltrating cytotoxic lymphocytes and abundant cellular immunosuppressors is the major obstacle responsible for the poor efficacy of PD-1/PD-L1 (programmed cell death 1 and its ligand 1) immune checkpoint blockade (ICB) therapy. Herein, a Janus silica nanoparticle (JSNP)-based immunomodulator is explored to reshape the TME for boosting the therapeutic outcomes of αPD-L1 therapy. The designed JSNP has two distinct domains, namely, an ultra pH-responsive side (UPS), which could encapsulate PI3Kγ inhibitor IPI549 in the pore structure, and a polycation-grafted intra-glutathione (GSH)-sensitive side (IGS), which could absorb CXCL9 cDNA on the surface. The final IPI549@UPS-IGS-PDMAEMA@CXCL9 cDNA (IUIPC) could release IPI549 in weak acid TME to target myeloid-derived suppressor cells (MDSCs) to reverse negative immunoregulation and then release CXCL9 cDNA in tumor cells with abundant GSH for sustained CXCL9 chemokine expression and secretion to improve cytotoxic lymphocyte recruitment signals, thereby jointly restoring tumor sensitivity to PD-1/PD-L1 ICB therapy. As expected, the IUIPC-mediated TME remodeling during αPD-L1 therapy significantly ameliorated TME immunosuppression, as well as induced potent systemic antitumor immune responses, which ultimately achieved a robustly boosted antitumor efficacy proven by remarkable suppression of primary tumor growth, obvious prevention of tumor recurrence, and significant regression of abscopal tumors. Hence, the IUIPC-mediated TME-regulating strategy provides an enormous perspective for the improvement of PD-1/PD-L1 ICB therapy.

Single-cell transcriptome analysis reveals the clinical implications of myeloid-derived suppressor cells in head and neck squamous cell carcinoma.

Head and neck squamous cell carcinoma (HNSC) is the most common malignant tumor that arises in the epithelium of the head and neck regions. Myeloid-derived suppressor cells (MDSCs) are one of the tumor-infiltrating immune cell populations, which play a powerful role in inhibiting anti-tumor immune response. Herein, we employed a single-cell RNA sequencing (scRNA-seq) dataset to dissect the heterogeneity of myeloid cells. We found that SPP1 + tumor-associated macrophages (TAMs) and MDSCs were the most abundant myeloid cells in the microenvironment. By cell cluster deconvolution from bulk RNA-seq datasets of larger patient groups, we observed that highly-infiltrated MDSC was a poor prognostic marker for patients' overall survival (OS) probabilities. To better apply the MDSC OS prediction values, we identified a set of six MDSC-related genes (ALDOA, CD52, FTH1, RTN4, SLC2A3, and TNFAIP6) as the prognostic signature. In both training and test cohorts, MDSC-related prognostic signature showed a promising value for predicting patients' prognosis outcomes. Further parsing the ligand-receptor pairs of intercellular communications by CellChat, we found that MDSCs could frequently interact with cytotoxic CD8 + T cells, SPP1 + TAMs, and endothelial cells. These interactions likely contributed to the establishment of an immunosuppressive microenvironment and the promotion of tumor angiogenesis. Our findings suggest that targeting MDSCs may serve as an alternative and promising target for the immunotherapy of HNSC.

Enhancing immunotherapy response in melanoma: myeloid-derived suppressor cells as a therapeutic target.

Despite the remarkable success of immune checkpoint inhibitors (ICIs) in melanoma treatment, resistance to them remains a substantial clinical challenge. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of myeloid cells that can suppress antitumor immune responses mediated by T and natural killer cells and promote tumor growth. They are major contributors to ICI resistance and play a crucial role in creating an immunosuppressive tumor microenvironment. Therefore, targeting MDSCs is considered a promising strategy to improve the therapeutic efficacy of ICIs. This Review describes the mechanism of MDSC-mediated immune suppression, preclinical and clinical studies on MDSC targeting, and potential strategies for inhibiting MDSC functions to improve melanoma immunotherapy.