Lung metastasis remains a determinant of poor prognosis and survival in breast cancer and is understood to depend on a permissive pulmonary immune niche rather than tumor cell traits alone. Here, we developed a host-directed RNA interference strategy to modulate this niche by reprogramming pulmonary B cells for breast cancer lung metastasis treatment. IF7C peptide-decorated cationic liposomes were constructed, which preferentially accumulated in the lung, and were internalized by pulmonary B cells, enabling selective silencing of annexin A1 (ANXA1). In tumor-conditioned primary B cells, ANXA1 knockdown reshaped the transcriptional landscape and shifted cytokine output away from an immunosuppressive profile characterized by IL-10, TGF-β, and IL-35. Functionally, ANXA1-silenced B cells lost their capacity to drive CD4⁺ T cells toward Foxp3⁺ regulatory differentiation and instead promoted Th1 features, while concurrently relieving suppression of CD8⁺ T-cell proliferation. In two postoperative syngeneic breast cancer models, perioperative administration achieved ANXA1 silencing in pulmonary B cells, reduced lung Treg accumulation, enhanced CD8⁺ T-cell infiltration and effector activity, and suppressed metastatic outgrowth with favorable systemic safety. These findings identify pulmonary B cells as an actionable regulator of the lung metastatic niche and establish perioperative, B-cell–focused ANXA1 silencing as a practical approach to prevent postoperative lung metastatic recurrence.

Cholangiocarcinoma (CCA), the second most prevalent primary hepatic malignancy, demonstrates resistance to antiangiogenic therapy due possibly to the dynamic interaction between cancer-associated fibroblast (CAF)-mediated extracellular matrix (ECM) remodeling and angiogenesis. This study shows that anti-VEGFR2 therapy activates CAF, inducing excessive ECM deposition and forming a physical barrier that diminishes the effectiveness of antiangiogenic therapy in CCA. Based on the finding, we rationally engineered vascular endothelial cell-derived nanovesicles that inherit the angiogenic factor receptor that competitively bind and neutralize pro-angiogenic ligands to diminish their bioeffects. These nanovesicles also retain high levels of integrin αvβ3 and specifically carry peptide B7-33 (an inducer of fibroblasts quiescence) modified by the cRGD peptide, thereby developing dual-functional nanovesicles (B7-33-SNPs). The study revealed that B7-33-SNPs synergistically disrupted the CAF-angiogenesis crosstalk, effectively reducing microvessel density and fibrotic deposition in subcutaneous xenograft CCA models. This combinatorial strategy achieved a 67.7 ± 17.6

Rationale: mRNA vaccine-based cancer immunotherapy requires innate immune activation followed by potent cellular immunity. Vectors of lipid nanoparticles (LNPs) with proinflammatory properties activate the innate immune pathway, while excessive inflammatory response of mRNA-LNPs vaccine often results in systemic inflammation, compromising its therapeutic safety. Methods: Here, we engineered a spleen-selective mRNA-LNPs (mRNA-sLNPs) vaccine by decoupling the excessive inflammation from strong cellular immunity through ionizable lipids substituting for potent cancer immunotherapy. Results: The mRNA-sLNPs vaccine with reduced inflammation achieved superior mRNA translation in the spleen and enhanced antigen-specific cellular immune responses. Mechanistically, the optimized mRNA-sLNPs vaccine amplified lysosomal escape and boosted antigen presentation with moderate co-stimulatory molecule expression by mitigating TLR4/MyD88/NF-κB signaling and pro-inflammatory cytokine secretion. In therapeutic mouse models, the engineered mRNA vaccine significantly inhibited both the growth of subcutaneous B16F10-OVA melanomas and the development of lung metastases following intravenous injection of B16F10-OVA cells with augmented infiltration of CD4+ and CD8+ T cells in the tumor microenvironment. Conclusion: Our findings might redefine the design principles of mRNA-LNPs vaccine as diminishing the inflammation of LNPs does not compromise cellular immunity, offering a clinically translatable strategy to advance mRNA vaccines for cancer immunotherapy.

Lipid nanoparticles (LNPs)-based mRNA vaccines have witnessed their great advantages in the fight against infectious diseases. However, the pro-inflammatory properties of mRNA-LNPs vaccines may hinder the induction of antigen-specific tolerogenic immune responses. Here, it is demonstrated that stearic acid-doped LNPs co-loaded with nucleoside-modified mRNA and celastrol selectively target spleen, convert their adjuvanticity and promote a tolerogenic rather than immunogenic DCs phenotype. Furthermore, the tolerogenic mRNA vaccine also invokes the generation of antigen-specific regulatory T cells (Tregs) in the spleen and migration of the induced Tregs to the lung. In a mouse model of allergic asthma, immunization with the tolerogenic mRNA vaccine significantly alleviated symptom induction, reducing eosinophilic granulocyte accumulation and mucus secretion. In conclusion, this spleen-targeted mRNA-LNPs vaccine platform induces tolerogenic immune responses, offering promise for the development of therapeutics against allergic asthma and other conditions requiring immune tolerance modulation.

Tumor-specific T cells play a vital role in potent antitumor immunity. However, their efficacy is severely affected by the spatiotemporal orchestration of antigen-presentation as well as the innate immune response in dendritic cells (DCs). Herein, we develop a minimalist nanovaccine that exploits a dual immunofunctional polymeric nanoplatform (DIPNP) to encapsulate ovalbumin (OVA) via electrostatic interaction when the nanocarrier serves as both STING agonist and immune adjuvant in DCs. In vitro results reveal that the nanocarrier induces STING activation via facilitating interferon regulatory factor 3 phosphorylation by block poly 18-crown-6-yl methacrylate (P18C6MA) mediated K+ perturbation cascade with endoplasmic reticulum stress, and stimulates DC maturation via the Toll-like receptor 4 activation by primary amine. In vivo studies indicate that the smart nanovaccine dramatically inhibits tumor growth with a long-term immune memory response in both the B16-OVA and EG7-OVA tumor models. After combination with programmed death ligand-1 antibody (aPD-L1), mice survival rate is notably prolonged. In addition, DIPNP forms a personalized nanovaccine after resected autologous primary tumor cell membranes decoration with a high antitumor activity in a homologous distant tumor model. The rational design provides inspiration for personalized nanovaccine construction via immunofunctional nanocarriers.

Extrahepatic cholangiocarcinoma (eCCA) is a rare but refractory cancer with dense desmoplasia. Prognosis-associated stromal cells in eCCA remain poorly characterized. Here, we profiled the tumor cellular composition and identified prognosis-related stromal signatures by single-cell RNA sequencing (scRNA-seq) in eCCA. ECCA patients were further stratified into different categories based on identified stromal signatures. Using scRNA-seq, we profiled the transcriptomes of 37,498 individual cells from eight eCCA biopsies, including five tumor tissues and three paired adjacent normal tissues. Bulk RNA sequencing (bRNA-seq) was also performed on 43 eCCA tumor tissues. Stromal cell composition and heterogeneity were examined through differential gene expression and gene set enrichment analyses. By assessing the expression levels of marker genes in bRNA-seq data, the correlation of stromal cell clusters with survival was explored. The GSVA scores of the cell-specific signature genes of the prognosis-related stromal cell subtypes were calculated and used to stratify eCCA patients. The results revealed that tumor stroma in eCCA were composed of hematopoietic progenitor-like cells (HPLCs), fibroblasts (Fb), Schwann cells (Sch), endothelial cells and immune cells. Prognosis-associated stromal cell subpopulations included MKI67 + HPLC, TMEM158 + C3-Fb, FOXP3 + regulatory T cells (Treg), SLIT2 + Sch, TPSD1 + C2-mast cells (MC) and CTSG + C3-MC. Based on these stromal signatures, the eCCA tumors were categorized into three classes: proliferative Group 1 with enrichment of MKI67 + HPLC, inflammatory and fibrotic Group 2 with enrichment of TPSD1 + C2- MC, FOXP3 + Treg and TMEM158 + C3-Fb, and neuronal Group 3 with enrichment of SLIT2 + Sch and CTSG + C3-MC. ECCA patients in Group 3 had a better prognosis when compared to Group 1 and 2, reflecting different impact of stromal subtypes on tumor progression. Single-cell transcriptomic analysis reveals prognosis-related stromal signatures that potentiate the stratification of eCCA into proliferative, inflammatory and fibrotic, and neuronal phenotypes, which has important implications on molecular classification and exploring therapeutic targets in eCCA.

Chemotherapy resistance is still a great challenge for clinical treatment of lung cancer. Here, we found that doxorubicin (DOX) induced an increase of labile Zn2+ in lung cancer cells, and these labile Zn2+ protected tumor cells against DOX cytotoxicity. Nanoparticles encapsulating N,N,N',N'-Tetrakis (2-pyridylmethyl)-ethylenediamine (TPEN) were then constructed to chelate labile Zn2+ for tumor therapy. Application of nanoparticle-encapsulated TPEN at low dose not only avoided severe side effects caused by removing physiological Zn2+ but also effectively chelated drug-induced labile Zn2+, and thereby enhanced DOX cytotoxicity. Mechanistically, nanosized TPEN inhibits ABCB1-mediated drug export potentiated by drug-induced labile Zn2+. Finally, the results unraveled that nanosized TPEN at low dose endowed DOX with the killing ability on resistant tumor cells. Taken together, our results demonstrate that chelating drug-induced labile Zn2+ by nanosized TPEN at low dose enhances lung cancer chemotherapy by inhibiting ABCB1, providing a feasible strategy to overcome chemoresistance in lung cancer.

During the ageing process, TNF-α can promote the expansion of myeloid-derived suppressor cells (MDSCs). However, it remains unclear which receptor(s) of TNF-α are involved in and how they modulate this process. Here, we report that TNFR2 hyperexpression induced by either TNF-α or IL-6, two proinflammatory factors of senescence-associated secretory phenotype (SASP), causes cellular apolarity and differentiation inhibition in aged MDSCs. Ex vivo overexpression of TNFR2 in young MDSCs inhibited their polarity and differentiation, whereas in vivo depletion of Tnfr2 in aged MDSCs promotes their differentiation. Consequently, the age-dependent increase of TNFR2 versus unaltered TNFR1 expression in aged MDSCs significantly shifts the balance of TNF-α signaling toward the TNFR2–JNK axis, which accounts for JNK-induced impairment of cell polarity and differentiation failure of aged MDSCs. Consistently, inhibiting JNK attenuates apolarity and partially restores the differentiation capacity of aged MDSCs, suggesting that upregulated TNFR2/JNK signaling is a key factor limiting MDSC differentiation during organismal ageing. Therefore, abnormal hyperexpression of TNFR2 represents a general mechanism by which extrinsic SASP signals disrupt intrinsic cell polarity behavior, thereby arresting mature differentiation of MDSCs with ageing, suggesting that TNFR2 could be a potential therapeutic target for intervention of ageing through rejuvenation of aged MDSCs.

BACKGROUND:PTEN loss has been identified in various tumor types and is linked to unfavorable clinical outcomes. In addition to PTEN mutation, multiple mechanisms contribute to PTEN loss during tumor development. However, the natural selection process of PTEN-deficient tumor cells remains unclear. Here, we aimed at further elucidating the role of PTEN-L in tumor progression.METHODS:PTEN knockout cell lines were generated using CRISPR/Cas9 technology. Ni-NTA affinity column chromatography was employed for PTEN-L purification. Tumor cell metastasis was evaluated in murine models and observed using the IVIS Spectrum Imaging System. RNA-sequencing, western blotting, PCR, flow cytometry, and cell proliferation assays were employed to investigate tumor cell dormancy and related mechanisms.RESULTS:The chemotherapeutic drugs, cisplatin, paclitaxel, and doxorubicin, induced tumor cells to secrete PTEN-long (PTEN-L), which shields PTEN-deficient tumor cells from chemotherapy-induced apoptosis better than it shields PTEN-intact cells. Further investigation revealed that PTEN-L treatment induced dormancy in PTEN-null tumor cells, characterized by an increase in p16 and p27 levels, cell-cycle arrest, reduced cell proliferation, and enhanced DNA repair. Furthermore, PTEN-L treatment selectively promoted the accumulation and growth of PTEN-null tumor cells in the lungs of C57BL/6J mice, while evading immune surveillance. Mechanistically, PTEN-L induced dormancy in PTEN-null tumor cells by activating the p38 signaling pathway. Addition of a p38 inhibitor effectively reversed dormancy and growth of PTEN-deficient tumor cells in the lungs. We also demonstrated that PTEN expression played a pivotal role in determining the outcome of PTEN-L-mediated antitumor therapy.CONCLUSIONS:In summary, PTEN-L was identified as a potent inducer of dormancy in PTEN-deficient tumor cells, which increased their efficient selection within the tumor microenvironment.

BACKGROUND:T cells play a pivotal role in chemotherapy-triggered anti-tumor effects. Emerging evidence underscores the link between impaired anti-tumor immune responses and resistance to paclitaxel therapy in triple-negative breast cancer (TNBC). Tumor-related endothelial cells (ECs) have potential immunoregulatory activity. However, how ECs regulate T cell activity during TNBC chemotherapy remains poorly understood. METHODS:Single-cell analysis of ECs in patients with TNBC receiving paclitaxel therapy was performed using an accessible single-cell RNA sequencing (scRNA-seq) dataset to identify key EC subtypes and their immune characteristics. An integrated analysis of a tumor-bearing mouse model, immunofluorescence, and a spatial transcriptome dataset revealed the spatial relationship between ECs, especially Tumor necrosis factor receptor (TNFR) 2+ ECs, and CD8+ T cells. RNA sequencing, CD8+ T cell proliferation assays, flow cytometry, and bioinformatic analyses were performed to explore the immunosuppressive function of TNFR2 in ECs. The downstream metabolic mechanism of TNFR2 was further investigated using RNA sequencing, cellular glycolysis assays, and western blotting. RESULTS:In this study, we identified an immunoregulatory EC subtype, characterized by enhanced TNFR2 expression in non-responders. By a mouse model of TNBC, we revealed a dynamic reduction in the proportion of the CD8+ T cell-contacting tumor vessels that could co-localize spatially with CD8+ T cells during chemotherapy and an increased expression of TNFR2 by ECs. TNFR2 suppresses glycolytic activity in ECs by activating NF-κB signaling in vitro. Tuning endothelial glycolysis enhances programmed death-ligand (PD-L) 1-dependent inhibitory capacity, thereby inducing CD8+ T cell suppression. In addition, TNFR2+ ECs showed a greater spatial affinity for exhausted CD8+ T cells than for non-exhausted CD8+ T cells. TNFR2 blockade restores impaired anti-tumor immunity in vivo, leading to the loss of PD-L1 expression by ECs and enhancement of CD8+ T cell infiltration into the tumors. CONCLUSIONS:These findings reveal the suppression of CD8+ T cells by ECs in chemoresistance and indicate the critical role of TNFR2 in driving the immunosuppressive capacity of ECs via tuning glycolysis. Targeting endothelial TNFR2 may serve as a potent strategy for treating TNBC with paclitaxel.

PURPOSE:MicroRNAs (miRNAs) are dominant cargo in exosomes and act as master regulators of cell function, inhibiting mRNA translation and affecting gene silencing. Some aspects of tissue-specific miRNA transport in bladder cancer (BC) and its role in cancer progression are not fully understood. MATERIALS AND METHODS:A microarray was used to identify miRNAs in mouse bladder carcinoma cell line MB49 exosomes. Real-time reverse transcription polymerase chain reaction was used to examine the expression of miRNAs in BC and healthy donor serum. Western blotting and immunohistochemical staining were used to examine the expression of dexamethasone-induced protein (DEXI) in patients with BC. CRISPR-Cas 9 was used to knock out Dexi in MB49, and flow cytometry was performed to test cell proliferation ability and apoptosis under chemotherapy. Human BC organoid culture, miR-3960 transfection, and 293T-exosome-loaded miR-3960 delivery were used to analyze the effect of miR-3960 on BC progression. RESULTS:The results showed that miR-3960 levels in BC tissue were positively correlated with patient survival time. Dexi was a major target of miR-3960. Dexi knockout inhibited MB49 cell proliferation and promoted cisplatin- and gemcitabine-induced apoptosis. Transfection of miR-3960 mimic inhibited DEXI expression and organoid growth. In parallel, 293T-exosome-loaded miR-3960 delivery and Dexi knockout significantly inhibited subcutaneous growth of MB49 cells in vivo. CONCLUSION:Our results demonstrate the potential role of miR-3960-mediated inhibition of DEXI as a therapeutic strategy against BC.

The clinical application of ferroptosis, characterized by iron-dependent lipid peroxidation, is limited because of the serious side effects of using toxic-dose iron. Herein, a polyvalent ferroptosis agonist-a hypoxia responsive polymer bearing 18-crown-6 ring (hPPAA18C6) is developed. In contrast to the natural ferroptosis agonists (erastin, RSL3, and sorafenib), hPPAA18C6 stimulates the ferroptosis by releasing endogenous iron stored in the natural "iron pools" of cellular organelles and depleting glutathione (GSH) via the benzoquinone generated from the cascade decaging reactions in hypoxia. hPPAA18C6 nanoparticle is loaded with photosensitizer-chlorine e6 (Ce6) (hPPAA18C6@Ce6) due to the inhomogeneous hypoxia microenvironment. Moreover, the exposed positively charged primary amine (NH2) from hPPAA18C6 acts as an immune adjuvant, facilitating dendritic cells maturation, antigen presentation, and cytotoxic T lymphocyte activation. hPPAA18C6@Ce6 induces anti-tumor responses that are dependent on ferroptosis, photodynamics therapy (PDT), and CD8(+) T-cell activity. In addition, the combination of hPPAA18C6 and Ce6 leads to combined therapeutic outcomes in primary, distant, and metastatic tumors. The activation of the ferroptosis pathway through functional polymer-hijacking endogenous iron and GSH may offer new therapeutic opportunities.

Reactive oxygen species (ROS)-mediated tumor catalytic therapy is typically hindered by gap junction proteins that form cell-to-cell channels to remove cytotoxic ROS, thereby protecting tumor cells from oxidative damage. In this work, a multifunctional nanozyme, FePGOGA, is designed and prepared by Fe(III)-mediated oxidative polymerization (FeP), followed by glucose oxidase (GOx) and GAP19 peptides co-loading through electrostatic and π-π interactions. The FePGOGA nanozyme exhibits excellent cascade peroxidase- and glutathione-oxidase-like activities that efficiently catalyze hydrogen peroxide conversion to hydroxyl radicals and convert reduced glutathione to oxidized glutathione disulfide. The loaded GOx starves the tumors and aggravates tumor oxidative stress through glucose decomposition, while GAP19 peptides block the hemichannels by inducing degradation of Cx43, thus increasing the accumulation of intracellular ROS, and decreasing the transport of intracellular glucose. Furthermore, the ROS reacts with primary amines of heat shock proteins to destroy their structure and function, enabling tumor photothermal therapy at the widely sought-after mild temperature (mildPTT, ≤45 °C). In vivo experiments demonstrate the significant antitumor effectof FePGOGA on cal27 xenograft tumors under near-infrared light irradiation. This study demonstrates the successful ablation of gap junction proteins to overcome resistance to ROS-mediated therapy, providing a regulator to suppress tumor self-preservation during tumor starvation, catalytic therapy, and mildPTT.

Tumour–stroma cell interactions impact cancer progression and therapy responses. Intercellular communication between fibroblasts and cancer cells using various soluble mediators has often been reported. In this study, we find that a zinc-transporter (ZIP1) positive tumour-associated fibroblast subset is enriched after chemotherapy and directly interconnects lung cancer cells with gap junctions. Using single-cell RNA sequencing, we identify several fibroblast subpopulations, among which Zip1 + fibroblasts are highly enriched in mouse lung tumours after doxorubicin treatment. ZIP1 expression on fibroblasts enhances gap junction formation in cancer cells by upregulating connexin-43. Acting as a Zn 2+ reservoir, ZIP1 + fibroblasts absorb and transfer Zn 2+ to cancer cells, leading to ABCB1-mediated chemoresistance. Clinically, ZIP1 high stromal fibroblasts are also associated with chemoresistance in human lung cancers. Taken together, our results reveal a mechanism by which fibroblasts interact directly with tumour cells via gap junctions and contribute to chemoresistance in lung cancer.

IFNγ has long been recognised as a key mediator of tumour immunity and angiostasis. However, IFNγ modulation for cancer therapy is still unsuccessful due to its complex effects on various host cells. In this study, we found that treatment of Lewis lung carcinoma transplants with cisplatin often caused IFNγ-dependent tumour vascular damage. IFNγ induced endothelial glycolysis and lactate production, leading to enhanced endocytosis of vascular endothelial (VE)-cadherin and vessel leakage. We have also developed anti-IFNγ nanoparticles coated with a clot-binding peptide CREKA (CREKA-lipo-anti-IFNγ), which targets the fibrin-fibronectin complex that appears in the leaky site of damaged tumour blood vessels. Blocking IFNγ activity in the leakage site of capillaries using nanoparticles rescued VE-cadherin distribution on the endothelial cellular surface, promoted blood vessel integrity, and improved drug delivery. In conclusion, IFNγ blockade in capillary leak site protected tumour blood vessels from lactate-dependent VE-cadherin loss and enhanced drug delivery during chemotherapy, which provides a basis for tissue-specific IFNγ blockade for tumour therapy.

Cancer-associated fibroblasts (CAFs), the principal constituent of the heterogenous tumor microenvironment, have been shown to promote tumor progression; however, the underlying mechanism is still less clear. Here, we find that transgelin (TAGLN) protein levels increased in primary CAFs isolated from human lung cancer, compared with those in paired normal fibroblasts. Tumor microarrays (TMAs) revealed that increased stromal TAGLN levels correlates with more lymphatic metastasis of tumor cells. In a subcutaneous tumor transplantation model, overexpression of Tagln in fibroblasts also increased tumor cell spread in mice. Further experiments show that Tagln overexpression promoted fibroblast activation and mobility in vitro. And TAGLN facilitates p-p65 entry into the nucleus, thereby activating the NF-κB signaling pathway in fibroblasts. Activated fibroblasts promote lung cancer progression via enhancing the release of pro-inflammatory cytokines, especially interleukine-6 (IL-6). Our study revealed that the high levels of stromal TAGLN is a predictive risk factor for patients with lung cancer. Targeting stromal TAGLN may present an alternative therapeutic strategy against lung cancer progression.

Chemotherapeutic drugs have been successfully used to treat several cancers, including melanoma.However, metastasis occasionally occurs after chemotherapy.Here, we reported that paclitaxel (PTX) treatment for B16F10 tumour in mice led to an enhanced lymphatic metastasis of the melanoma cells, although a significant inhibition of tumour growth at the injection site was observed.Further study demonstrated that PTX upregulated the expression of C-C chemokine receptor type 7 (CCR7) in B16F10 cells, enhancing their migration through the activation of JNK and p38 signalling pathways.Loss of CCR7 or blockade of C-C motif chemokine ligand 21 (CCL21)/CCR7 axis abolished the pro-migration effect of PTX on B16F10 melanoma cells.Importantly, combination of PTX and CCR7 mAb could simultaneously delay the tumour growth and reduce the lymphatic metastasis in B16F10 melanoma.The blockade of CCL21/CCR7 axis may collectively serve as a strategy for lymphatic metastasis in some melanoma after chemotherapy.

Liver metastasis is common in patients with pancreatic cancer (PC) and is the leading cause of death associated with PC. Liver fibrosis induced by activated hepatic stellate cells (HSCs) creates a favorable metastatic microenvironment that promotes metastasis growth. B7‐33, a therapeutic peptide (relaxin analog) that targets relaxin family peptide receptors on activated HSCs, inhibits the pSMAD2/3 signaling pathway and weakens the fibrogenic properties of activated HSCs. However, the short half‐life and highly conserved nature of the B7‐33 sequence limit its application in vivo. Here, B7‐33 is modified with the cRGD sequence, which does not affect the efficacy of B7‐33 and allows B7‐33 to assemble into vascular endothelial cell membrane‐derived vesicles by specifically interacting with integrin α v β 3 . These rationally designed vesicles (B7‐33‐HNPs) are able to prolong the half‐life of B7‐33 in vivo and accumulate in the liver to reverse HSCs activation. Moreover, B7‐33‐HNPs prevent the formation and growth of liver metastases in a mouse model of metastatic PC. This study proposes a feasible strategy for building a therapeutic peptide delivery system through specific interactions, serving as a reference for preventing liver metastasis of PC through the regulation of HSCs.

Migration of myeloid-derived suppressor cells (MDSCs) out of the circulation, across vascular walls, and into tumor is crucial for their immunosuppressive activity. A deeper understanding of critical junctional molecules and the regulatory mechanisms that mediate the extravasation of MDSCs could identify approaches to overcome cancer immunosuppression. In this study we used mice deficient in tight-junction protein Claudin-12 (Cldn12) compared to wild-type mice and found that loss of host Cldn12 inhibited the growth of transplanted tumors, reduced intratumoral accumulation of MDSCs, increased anti-tumor immune responses, and decreased tumor vescular density. Further studies revealed that Cldn12 expression on the cell surface of both MDSCs and endothelial cells is required for MDSCs transit across tumor vascular endothelial cells (ECs). Importantly, expression of Cldn12 in MDSCs was modulated by granulocyte-macrophage colony-stimulating factor (GM-CSF) in an AKT-dependent manner. Therefore, our results indicate that Cldn12 could serve as a promising target for restoring the anti-tumor response by interfering with MDSCs transendothelial migration.