CTLA-4 blockade induces tumor pyroptosis via CD8+ T cells in head and neck squamous cell carcinoma.

Immune checkpoint blockade (ICB) treatment has demonstrated excellent medical effects in oncology, and it is one of the most sought after immunotherapies for tumors. However, there are several issues with ICB therapy, including low response rates and a lack of effective efficacy predictors. Gasdermin-mediated pyroptosis is a typical inflammatory death mode. We discovered that increased expression of gasdermin protein was linked to a favorable tumor immune microenvironment and prognosis in head and neck squamous cell carcinoma (HNSCC). We used the mouse HNSCC cell lines 4MOSC1 (responsive to CTLA-4 blockade) and 4MOSC2 (resistant to CTLA-4 blockade) orthotopic models and demonstrated that CTLA-4 blockade treatment induced gasdermin-mediated pyroptosis of tumor cells, and gasdermin expression positively correlated to the effectiveness of CTLA-4 blockade treatment. We found that CTLA-4 blockade activated CD8+ T cells and increased the levels of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) cytokines in the tumor microenvironment. These cytokines synergistically activated the STAT1/IRF1 axis to trigger tumor cell pyroptosis and the release of large amounts of inflammatory substances and chemokines. Collectively, our findings revealed that CTLA-4 blockade triggered tumor cells pyroptosis via the release of IFN-γ and TNF-α from activated CD8+ T cells, providing a new perspective of ICB.

Activation of Pyroptosis Using AIEgen-Based sp2 Carbon-Linked Covalent Organic Frameworks.

Covalent organic frameworks (COFs) have emerged as a promising class of crystalline porous materials for cancer phototherapy, due to their exceptional characteristics, including light absorption, biocompatibility, and photostability. However, the aggregation-caused quenching effect and apoptosis resistance often limit their therapeutic efficacy. Herein, we demonstrated for the first time that linking luminogens with aggregation-induced emission effect (AIEgens) into COF networks via vinyl linkages was an effective strategy to construct nonmetallic pyroptosis inducers for boosting antitumor immunity. Mechanistic investigations revealed that the formation of the vinyl linkage in the AIE COF endowed it with not only high brightness but also strong light absorption ability, long lifetime, and high quantum yield to favor the generation of reactive oxygen species for eliciting pyroptosis. In addition, the synergized system of the AIE COF and αPD-1 not only effectively eradicated primary and distant tumors but also inhibited tumor recurrence and metastasis in a bilateral 4T1 tumor model.

Immunogenic hypofractionated radiotherapy sensitising head and neck squamous cell carcinoma to anti-PD-L1 therapy in MDSC-dependent manner.

BACKGROUND: Enhancing the response rate of immunotherapy will aid in the success of cancer treatment. Here, we aimed to explore the combined effect of immunogenic radiotherapy with anti-PD-L1 treatment in immunotherapy-resistant HNSCC mouse models. METHODS: The SCC7 and 4MOSC2 cell lines were irradiated in vitro. SCC7-bearing mice were treated with hypofractionated or single-dose radiotherapy followed by anti-PD-L1 therapy. The myeloid-derived suppressive cells (MDSCs) were depleted using an anti-Gr-1 antibody. Human samples were collected to evaluate the immune cell populations and ICD markers. RESULTS: Irradiation increased the release of immunogenic cell death (ICD) markers (calreticulin, HMGB1 and ATP) in SCC7 and 4MOSC2 in a dose-dependent manner. The supernatant from irradiated cells upregulated the expression of PD-L1 in MDSCs. Mice treated with hypofractionated but not single-dose radiotherapy were resistant to tumour rechallenge by triggering ICD, when combined with anti-PD-L1 treatment. The therapeutic efficacy of combination treatment partially relies on MDSCs. The high expression of ICD markers was associated with activation of adaptive immune responses and a positive prognosis in HNSCC patients. CONCLUSION: These results present a translatable method to substantially improve the antitumor immune response by combining PD-L1 blockade with immunogenic hypofractionated radiotherapy in HNSCC.

Overexpression of CD168 is related to poor prognosis in oral squamous cell carcinoma.

OBJECTIVES: Receptor for hyaluronic acid (HA)-mediated motility (RHAMM) is also known as CD168. This study proposed to elucidate the prognostic and clinicopathological significance of CD168 expression in oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: Immune staining of a human tissue microarray and Western blot were used to reveal the expression level of CD168 in OSCC. Correlations between clinicopathological indexes and CD168 expression in OSCC patients were assessed. RESULTS: Increased expression of CD168 was detected in OSCC tissues. High expression of CD168 indicated worse survival of patients (p < .05). Furthermore, high expression of CD168 was related to pathological grade in OSCC (p < .05). CD168 expression was positively related to programmed death ligand 1 (PD-L1), CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6), B7 homology 4 protein (B7-H4), CD44, CD133, and Slug expression in OSCC. CONCLUSION: This study revealed the overexpression of CD168 in OSCC and shed light on the prognostic significance of CD168 expression in OSCC patients.

Three-Dimensional Covalent Organic Frameworks with Cross-Linked Pores for Efficient Cancer Immunotherapy.

We report the design and synthesis of a series of three-dimensional (3D) covalent organic frameworks (COFs) as immunogenic cell death (ICD) inducers for cancer immunotherapy. Three triple-topic amine building blocks, inactive to inducing ICD, were used to construct three COFs, COF-607, COF-608, and COF-609, with outstanding ICD eliciting efficiency. Mechanism studies revealed that after linking these ICD inert monomers into the COF backbone, the optical properties of these COFs could be systematically tuned to achieve excellent reactive oxygen species (ROS) production performance. This combined with 3D cross-linked pores, mimicking lung structure, favor the exchange and diffusion of oxygen and ROS, leading to excellent inducing ICD efficacy. One member, COF-609, is capable of triggering abscopal and long-lasting immune memory effects in a mouse model of breast cancer with >95% mice survival after being treated with COF-609+αCD47 for 110 days.

Overexpression of RRM2 is related to poor prognosis in oral squamous cell carcinoma.

OBJECTIVES: Ribonucleotide reductase M2 (RRM2) is a rate-limiting enzyme involved in DNA repair and synthesis. This study aimed to investigate the expression level, clinicopathological significance, and prognostic value of RRM2 in oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: Human OSCC tissue microarrays were used to detect the expression of RRM2, cancer stem cell (CSC) markers CD44 and aldehyde dehydrogenase 1 (ALDH1), and the epithelial-mesenchymal transition (EMT) marker Slug. The correlation of RRM2 expression with clinicopathological parameters was evaluated. The effects of RRM2 on cell proliferation, migration, and apoptosis were investigated. RESULTS: Compared with normal and dysplastic tissues, the expression of RRM2 in human primary OSCC was significantly increased, and its overexpression was correlated with advanced pathological grade. The overall survival rate of patients with high RRM2 expression was lower than that of patients with low RRM2 expression. The overexpression of RRM2 was significantly associated with OSCC recurrence, and its overexpression was correlated with the CSC markers CD44 and ALDH1 and the EMT marker Slug. The expression of RRM2 promotes the proliferation and migration of human OSCC cells and inhibits apoptosis. CONCLUSION: Ribonucleotide reductase M2 may be a novel target in the diagnosis, prognosis, and therapy of OSCC.

Overexpression of ATAD2 indicates Poor Prognosis in Oral Squamous Cell Carcinoma.

ATPase family AAA domain-containing protein 2 (ATAD2) is highly expressed in a variety of malignancies and can promote the proliferation of tumor cells and inhibit their differentiation. However, the expression of ATAD2 and its related mechanism in oral squamous cell carcinoma (OSCC) are still unknown. Immunohistochemical staining of ATAD2, cancer stem cells (CSCs) markers and immune checkpoint molecules was conducted on human OSCC specimens to determine the expression levels of these proteins and their correlations with the clinicopathological characteristics of ATAD2 in OSCC. Moreover, the role of ATAD2 in cell proliferation, apoptosis, migration and epithelial-mesenchymal transition (EMT) were assessed by silencing ATAD2 in vitro. Immunohistochemical analysis revealed that ATAD2 expression in OSCC tissues was markedly higher than that in adjacent dysplastic tissues and normal mucosal tissues. Overexpression of ATAD2 was related to poor overall survival in OSCC patients. In addition, the protein expression of ATAD2 was notably correlated with the expression of B7-H4, PD-L1, CMTM6, Slug and ALDH1 in human OSCC. ATAD2 knockdown arrested the cell cycle, promoted the apoptosis, and inhibited the proliferation, migration, and EMT of OSCC cells. In conclusion, these findings revealed that ATAD2 is highly expressed in OSCC and can act as a poor prognostic indicator.

Expression of inositol polyphosphate 4-phosphatase type II and the prognosis of oral squamous cell carcinoma.

Inositol polyphosphate 4-phosphatase type II (INPP4B) is a phosphoinositide phosphatase that plays complex roles in the pathogenesis of different tumors. We aimed to explore the expression, clinicopathological significance, and prognostic value of INPP4B in oral squamous cell carcinoma (OSCC). Tissue microarrays that included samples from 176 primary OSCCs, 42 normal mucosae, and 69 dysplastic tissues were used for immunostaining analyses of INPP4B protein. Aperio ScanScope CS scanner and aperio quantification software were used to scan the microarrays and score the staining, respectively. We also evaluated the correlation between INPP4B expression and clinical parameters, pathological grades, node-positive status, and immune-related markers. Expression of INPP4B was statistically significantly upregulated in human primary OSCC tissues compared with dysplastic and normal tissues. Additionally, we found that patients with strong expression of INPP4B had a statistically significantly poorer overall survival than patients with weak expression of INPP4B. Furthermore, our study indicated that expression of INPP4B in OSCC was positively associated with expression of p-S6Ser235/236 , p-CADSer1859 , and certain immune checkpoints (B7-H4, Galectin-9). Therefore, INPP4B may be an independent prognostic indicator for patients with OSCC, in which it might function as an oncoprotein.

Increased Expression of LAMTOR5 Predicts Poor Prognosis and Is Associated with Lymph Node Metastasis of Head and Neck Squamous Cell Carcinoma.

Late endosomal/lysosomal adaptor and MAPK and mTOR activator 5 (LAMTOR5) is a novel oncoprotein associated with several human malignancies, but its clinical role in head and neck squamous cell carcinoma (HNSCC) remains unclear. The present study aims to investigate the clinical and pathological significance of LAMTOR5 in HNSCC. We utilized immunohistochemical staining of human tissue microarrays (210 primary HNSCC, 42 normal oral mucosae, 69 oral epithelial dysplasia, and 68 metastasis lymph nodes) to explore the clinical and pathological significance of LAMTOR5 in HNSCC. Additionally, expression level of LAMTOR5 in immunoreactivity of Pten conditional knock out (Pten cKO) mice HNSCC was also assessed. We found LAMTOR5 was overexpressed in human and Pten cKO mice HNSCC, and its expression was significantly associated with patients' overall survival, lymph node metastasis and lymph node grade. Furthermore, LAMTOR5 expression was significantly correlated with the expression of p-AktSer473, p-S6Ser235/236, immune checkpoints (PD-L1, Galectin 9, VISTA and B7-H4) and macrophage markers (CD68 and CD163). In Pten cKO mice HNSCC, it was also significantly correlated with VISTA and F4/80. Consequently, we consider that high expression of LAMTOR5 might be a poor prognostic indicator and correlated with the immunosuppression of tumor microenvironment.

Glutamine inhibition combined with CD47 blockade enhances radiotherapy-induced ferroptosis in head and neck squamous cell carcinoma.

Head and neck squamous cell carcinoma (HNSCC) is a formidable cancer type that poses significant treatment challenges, including radiotherapy (RT) resistance. The metabolic characteristics of tumors present substantial obstacles to cancer therapy, and the relationship between RT and tumor metabolism in HNSCC remains elusive. Ferroptosis is a type of iron-dependent regulated cell death, representing an emerging disease-modulatory mechanism. Here, we report that after RT, glutamine levels rise in HNSCC, and the glutamine transporter protein SLC1A5 is upregulated. Notably, blocking glutamine significantly enhances the therapeutic efficacy of RT in HNSCC. Furthermore, inhibition of glutamine combined with RT triggers immunogenic tumor ferroptosis, a form of nonapoptotic regulated cell death. Mechanistically, RT increases interferon regulatory factor (IRF) 1 expression by activating the interferon signaling pathway, and glutamine blockade augments this efficacy. IRF1 drives transferrin receptor expression, elevating intracellular Fe2+ concentration, disrupting iron homeostasis, and inducing cancer cell ferroptosis. Importantly, the combination treatment-induced ferroptosis is dependent on IRF1 expression. Additionally, blocking glutamine combined with RT boosts CD47 expression and hinders macrophage phagocytosis, attenuating the treatment effect. Dual-blocking glutamine and CD47 promote tumor remission and enhance RT-induced ferroptosis, thereby ameliorating the tumor microenvironment. Our work provides valuable insights into the metabolic and immunological mechanisms underlying RT-induced ferroptosis, highlighting a promising strategy to augment RT efficacy in HNSCC.

Fn-OMV potentiates ZBP1-mediated PANoptosis triggered by oncolytic HSV-1 to fuel antitumor immunity.

Oncolytic viruses (OVs) show promise as a cancer treatment by selectively replicating in tumor cells and promoting antitumor immunity. However, the current immunogenicity induced by OVs for tumor treatment is relatively weak, necessitating a thorough investigation of the mechanisms underlying its induction of antitumor immunity. Here, we show that HSV-1-based OVs (oHSVs) trigger ZBP1-mediated PANoptosis (a unique innate immune inflammatory cell death modality), resulting in augmented antitumor immune effects. Mechanistically, oHSV enhances the expression of interferon-stimulated genes, leading to the accumulation of endogenous Z-RNA and subsequent activation of ZBP1. To further enhance the antitumor potential of oHSV, we conduct a screening and identify Fusobacterium nucleatum outer membrane vesicle (Fn-OMV) that can increase the expression of PANoptosis execution proteins. The combination of Fn-OMV and oHSV demonstrates potent antitumor immunogenicity. Taken together, our study provides a deeper understanding of oHSV-induced antitumor immunity, and demonstrates a promising strategy that combines oHSV with Fn-OMV.

A Dual-Responsive STAT3 Inhibitor Nanoprodrug Combined with Oncolytic Virus Elicits Synergistic Antitumor Immune Responses by Igniting Pyroptosis.

Immune checkpoint blockade (ICB) therapy shows excellent efficacy against malignancies; however, insufficient tumor immunogenicity and the immunosuppressive tumor microenvironment (TME) are considered as the two major stumbling blocks to a broad ICB response. Here, a combinational therapeutic strategy is reported, wherein TME-reactive oxygen species/pH dual-responsive signal transducers and activators of transcription 3 inhibitor nanoprodrugs MPNPs are combined with oncolytic herpes simplex virus 1 virotherapy to synergistically ignite pyroptosis for enhancing immunotherapy. MPNPs exhibit a certain level of tumor accumulation, reduce tumor cell stemness, and enhance antitumor immune responses. Furthermore, the simultaneous application of oncolytic viruses (OVs) confers MPNPs with higher tumor penetration capacity and remarkable gasdermin-E-mediated pyroptosis, thereby reshaping the TME and transforming "cold" tumors into "hot" ones. This "fire of immunity" strategy successfully activates robust T-cell-dependent antitumor responses, potentiating ICB effects against local recurrence and pulmonary metastasis in preclinical "cold" murine triple-negative breast cancer and syngeneic oral cancer models. Collectively, this work may pave a new way and offer an unprecedented opportunity for the combination of OVs with nanomedicine for cancer immunotherapy.

CD103 blockade impair anti-CTLA-4 immunotherapy in oral cancer.

OBJECTIVES: CD103+CD8+T cells is a subtype of T cells with excellent tumor killing ability and it could response to immune checkpoint blockade therapy in several types of cancer, but the phenotype, role and molecular mechanism CD103+CD8+T cells in the OSCC still unclear. MATERIALS AND METHODS: The distribution and phenotype of CD103+CD8+T cells were investigated by performing multiplexed immunohistochemistry on human OSCC tissue microarray and flow cytometric analysis of fresh OSCC tumor-infiltrating lymphocytes (TILs). By in vivo use of anti-CD103 monoclonal antibody (mAb) in the 4MOSC1 tumor-bearing mouse model, CD103+CD8+T cell infiltration and cytotoxicity was clarified. RESULTS: The majority of CD8+T cells in both human and animal OSCC intra-tumoral region were CD103+CD8+T cells with high expression levels of cytotoxic molecules, which can be impaired by CD103 blockade. In addition, combined use of anti-CD103 mAb with anti-CTLA-4 mAb displayed impaired immune checkpoint blockade therapy efficiency. CONCLUSION: CD103+CD8+T cells are the major intra-tumoral subset of CD8+T cells in both animal and human OSCC, and that CD103+CD8+T cells demonstrate remarkable tumor-infiltrating and tumor-killing properties, thereby CD103+CD8+T cells may critical for anti-CTLA-4 immunotherapy in OSCC.

COVID-19 vaccination effectiveness and safety in vulnerable populations: a meta-analysis of 33 observational studies.

Background: Even 3 years into the COVID-19 pandemic, questions remain about how to safely and effectively vaccinate vulnerable populations. A systematic analysis of the safety and efficacy of the COVID-19 vaccine in at-risk groups has not been conducted to date. Methods: This study involved a comprehensive search of PubMed, EMBASE, and Cochrane Central Controlled Trial Registry data through 12 July 2022. Post-vaccination outcomes included the number of humoral and cellular immune responders in vulnerable and healthy populations, antibody levels in humoral immune responders, and adverse events. Results: A total of 23 articles assessing 32 studies, were included. The levels of IgG (SMD = -1.82, 95% CI [-2.28, -1.35]), IgA (SMD = -0.37, 95% CI [-0.70, -0.03]), IgM (SMD = -0.94, 95% CI [-1.38, -0.51]), neutralizing antibodies (SMD = -1.37, 95% CI [-2.62, -0.11]), and T cells (SMD = -1.98, 95% CI [-3.44, -0.53]) were significantly lower in vulnerable than in healthy populations. The positive detection rates of IgG (OR = 0.05, 95% CI [0.02, 0.14]) and IgA (OR = 0.03, 95% CI [0.01, 0.11]) antibodies and the cellular immune response rates (OR = 0.20, 95% CI [0.09, 0.45]) were also lower in the vulnerable populations. There were no statistically significant differences in fever (OR = 2.53, 95% CI [0.11, 60.86]), chills (OR = 2.03, 95% CI [0.08, 53.85]), myalgia (OR = 10.31, 95% CI [0.56, 191.08]), local pain at the injection site (OR = 17.83, 95% CI [0.32, 989.06]), headache (OR = 53.57, 95% CI [3.21, 892.79]), tenderness (OR = 2.68, 95% CI [0.49, 14.73]), and fatigue (OR = 22.89, 95% CI [0.45, 1164.22]) between the vulnerable and healthy populations. Conclusion: Seroconversion rates after COVID-19 vaccination were generally worse in the vulnerable than healthy populations, but there was no difference in adverse events. Patients with hematological cancers had the lowest IgG antibody levels of all the vulnerable populations, so closer attention to these patients is recommended. Subjects who received the combined vaccine had higher antibody levels than those who received the single vaccine.

Targeting PCSK9 reduces cancer cell stemness and enhances antitumor immunity in head and neck cancer.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has been demonstrated to play a critical role in regulating cholesterol homeostasis and T cell antitumor immunity. However, the expression, function, and therapeutic value of PCSK9 in head and neck squamous cell carcinoma (HNSCC) remain largely unexplored. Here, we found that the expression of PCSK9 was upregulated in HNSCC tissues, and higher PCSK9 expression indicated poorer prognosis in HNSCC patients. We further found that pharmacological inhibition or siRNA downregulating PCSK9 expression suppressed the stemness-like phenotype of cancer cells in an LDLR-dependent manner. Moreover, PCSK9 inhibition enhanced the infiltration of CD8+ T cells and reduced the myeloid-derived suppressor cells (MDSCs) in a 4MOSC1 syngeneic tumor-bearing mouse model, and it also enhanced the antitumor effect of anti-PD-1 immune checkpoint blockade (ICB) therapy. Together, these results indicated that PCSK9, a traditional hypercholesterolemia target, may be a novel biomarker and therapeutic target to enhance ICB therapy in HNSCC.

VISTA blockade alleviates immunosuppression of MDSCs in oral squamous cell carcinoma.

V-domain Ig suppressor of T-cell activation (VISTA) is a novel immune checkpoint regulator that can inhibit T cell-mediated antitumor immunity. Although the use of anti-VISTA monoclonal antibody has demonstrated encouraging outcomes in the therapy of various malignancies, its specific impact and underlying mechanisms in oral squamous cell carcinoma (OSCC) remain to be explored. In this work, we analyzed human OSCC tissue microarrays, human peripheral blood mononuclear cells, and immunocompetent transgenic mouse models to investigate the relationship between high VISTA expression and markers of myeloid-derived immunosuppressive cells (MDSCs; CD11b, CD33, Arginase-1), tumor-associated macrophages (CD68, CD163, CD206), and T cell function (CD8, PD-L1, Granzyme B). In OSCC, we discovered that VISTA was highly expressed and stably expressed in MDSCs. Furthermore, we established a mouse OSCC orthotopic xenograft tumor model to investigate the impact of VISTA blockade on the tumor microenvironment. We found that VISTA blockade reduces the immunosuppressive microenvironment and delays tumor growth. This is achieved by suppressing the quantity and function of MDSCs while boosting the function of tumor-infiltrating T cells. Our research indicated that VISTA expressed by MDSCs has a crucial function in the progression of OSCC and that VISTA blockade therapy is a promising immune checkpoint blockade therapy.

Integration of AIEgens into covalent organic frameworks for pyroptosis and ferroptosis primed cancer immunotherapy.

Immunogenic programmed cell death, such as pyroptosis and ferroptosis, efficiently induces an acute inflammatory response and boosts antitumor immunity. However, the exploration of dual-inducers, particularly nonmetallic inducers, capable of triggering both pyroptosis and ferroptosis remains limited. Here we show the construction of a covalent organic framework (COF-919) from planar and twisted AIEgen-based motifs as a dual-inducer of pyroptosis and ferroptosis for efficient antitumor immunity. Mechanistic studies reveal that COF-919 displays stronger near-infrared light absorption, lower band energy, and longer lifetime to favor the generation of reactive oxygen species (ROS) and photothermal conversion, triggering pyroptosis. Because of its good ROS production capability, it upregulates intracellular lipid peroxidation, leading to glutathione depletion, low expression of glutathione peroxidase 4, and induction of ferroptosis. Additionally, the induction of pyroptosis and ferroptosis by COF-919 effectively inhibits tumor metastasis and recurrence, resulting in over 90% tumor growth inhibition and cure rates exceeding 80%.

Bioengineering of BRAF and COX2 inhibitor nanogels to boost the immunotherapy of melanoma via pyroptosis.

Glutathione-responsive nanogels (CDNPs) crosslinked via crosslinker DBHD with the BRAF inhibitor dabrafenib and the COX2 inhibitor celecoxib were fabricated. The CDNPs can effectively induce tumor cell pyroptosis to activate robust antitumor immunity. Additionally, CDNPs combined with αPD-1 antibody greatly inhibited tumor growth in a melanoma mouse model with a prolonged survival time.

Diselenide-Based Dual-Responsive Prodrug as Pyroptosis Inducer Potentiates Cancer Immunotherapy.

Pyroptosis is demonstrated to trigger antitumor immunity and represents a promising new strategy to potentiate cancer immunotherapy. The number of potent pyroptosis inducers, however, is limited and without tumor-targeting capability, which inevitably causes damage in normal tissues. Herein, a small molecular prodrug of paclitaxel-oxaliplatin is rationally synthesized, which can be covalently self-assembled with diselenide-containing cross-linking (Dse11), producing a diselenide nanoprodrug (DSe@POC) to induce pyroptosis for the first time. The diselenide bonds within DSe@POC can be split by high glutathione in the tumor microenvironment (TME) and reactive oxygen species induced by photodynamic therapy, thus possessing excellent TME on-target effects. Additionally, DSe@POC is able to elicit intense pyroptosis to remodel the immunostimulated TME and trigger a robust immune response. Furthermore, combined αPD-1 therapy effectively inhibits the growth of remote tumors through the abscopal effect, amplifies a long-term immune memory response to reject rechallenged tumors, and prolongs survival. Collectively, DSe@POC, as the first TME dual-responsive diselenide-based pyroptosis inducer, will open up an attractive approach for cancer immunotherapy.

Sunitinib attenuates reactive MDSCs enhancing anti-tumor immunity in HNSCC.

Enhancer of zeste homolog 2 (EZH2) is implicated in promoting HNSCC malignant progression. However, EZH2 inhibitors, when used alone, increase the number of myeloid-derived suppressor cells (MDSCs), which are responsible for enhancing tumor stemness and promoting tumor immune escape. We aimed to determine whether combining tazemetostat (an EZH2 inhibitor) and sunitinib (a MDSC inhibitor) can improve the response rate to an immune-checkpoint-blocking (ICB) therapy. We evaluated the efficacy of the above treatment strategies by bioinformatics analysis and animal experiments. EZH2 overexpression and abundant MDSCs in patients with HNSCC are associated with tumor progression. Tazemetostat treatment alone had limited inhibitory effect on HNSCC progression in the mouse models, accompanied by a surge in the number of MDSCs in the tumor microenvironment. Conversely, the combined use of tazemetostat and sunitinib reduced the number of MDSCs and regulatory T cell populations, promoting intratumoral infiltration of T cells and inhibiting of T cell exhausting, regulating of wnt/ß-catenin signaling pathway and tumor stemness, promoting the intratumoral PD-L1 expression and improved the response rate to anti-PD-1 therapy. The combined use of EZH2 and MDSC inhibitors effectively reverses HNSCC-specific immunotherapeutic resistance and is a promising strategy for overcoming resistance to ICB therapy.