The roles of exosomal immune checkpoint proteins in tumors

Exosome-mediated communication between T cells and dendritic cells: Implications for therapeutic strategies

Cell communication is crucial for coordinating physiological functions in multicellular organisms, with exosomes playing a significant role. Exosomes mediate intercellular communication by transporting proteins, lipids, and nucleic acids between cells. These small, membrane-bound vesicles, derived from the endosomal pathway, are integral to various biological processes, including signal transmission and cellular behavior modulation. Recent advances highlight the potential of exosomes, especially dendritic cell-derived exosomes (DEXs), for diagnostic and therapeutic applications, particularly in cancer immunotherapy. DEXs are distinguished by their ability to present antigens and stimulate immune responses more effectively than exosomes from other cell types. They carry a cargo rich in immunostimulatory molecules and MHC-peptide complexes, which facilitate robust T-cell activation and enhance tumor-specific immune responses. The unique properties of DEXs, such as their ability to cross biological barriers and resist tumor-induced immunosuppression, position them as promising candidates for therapeutic applications. Here, I review the reports on the bidirectional interaction between dendritic cells and T cells through exosomes and their role in medicine.

Engineered Immunomodulatory Extracellular Vesicles from Epithelial Cells with the Capacity for Stimulation of Innate and Adaptive Immunity in Cancer and Autoimmunity

Extracellular vesicles (EVs) are generated in all cells. Systemic administration of allogenic EVs derived from epithelial and mesenchymal cells has been shown to be safe, despite carrying an array of functional molecules, including thousands of proteins. To address whether epithelial cell-derived EVs can be modified to acquire the capacity to induce an immune response, we engineered 293T EVs to harbor the immunomodulatory molecules CD80, OX40L, and PD-L1. We demonstrated abundant levels of these proteins in the engineered cells and EVs. Functionally, the engineered EVs efficiently elicited positive and negative costimulation of human and murine T cells. In the setting of cancer and autoimmune hepatitis, the engineered EVs modulated T cell functions and altered disease progression. OX40L EVs also provided enhanced antitumor activity in combination with anti-CTLA-4 in melanoma-bearing mice. In addition, we added multiple immunomodulatory proteins in EVs (EVmIM), attempting to elicit an immune response in both lymphoid and myeloid compartments. The EVmIM containing CD80, 4-1BBL, CD40L, CD2, and CD32 engaged both T cells and antigen presenting cells (APCs) in melanoma tumors, demonstrating the capacity for EVmIM to elicit antitumor activity. Our work provides evidence that EVs can be engineered to induce specific immune responses with translational potential to modulate immune cell functions in pathological settings.

Influencing immunity: role of extracellular vesicles in tumor immune checkpoint dynamics

Immune checkpoint proteins (ICPs) serve as critical regulators of the immune system, ensuring protection against damage due to overly activated immune responses. However, within the tumor environment, excessive ICP activation weakens antitumor immunity. Despite the development of numerous immune checkpoint blockade (ICB) drugs in recent years, their broad application has been inhibited by uncertainties about their clinical efficacy. A thorough understanding of ICP regulation in the tumor microenvironment is essential for advancing the development of more effective and safer ICB therapies. Extracellular vesicles (EVs), which are pivotal mediators of cell-cell communication, have been extensively studied and found to play key roles in the functionality of ICPs. Nonetheless, a comprehensive review summarizing the current knowledge about the crosstalk between EVs and ICPs in the tumor environment is lacking. In this review, we summarize the interactions between EVs and several widely studied ICPs as well as their potential clinical implications, providing a theoretical basis for further investigation of EV-related ICB therapeutic approaches.

Composition, functions, and applications of exosomal membrane proteins

Exosomes play a crucial role in various biological processes, such as human development, immune responses, and disease occurrence. The membrane proteins on exosomes are pivotal factors for their biological functionality. Currently, numerous membrane proteins have been identified on exosome membranes, participating in intercellular communication, mediating target cell recognition, and regulating immune processes. Furthermore, membrane proteins from exosomes derived from cancer cells can serve as relevant biomarkers for early cancer diagnosis. This article provides a comprehensive review of the composition of exosome membrane proteins and their diverse functions in the organism's biological processes. Through in-depth exploration of exosome membrane proteins, it is expected to offer essential foundations for the future development of novel biomedical diagnostics and therapies.

The Role of Intracellular and Extracellular Vesicles in the Development of Therapy Resistance in Cancer

Cancer is the second leading cause of global mortality and claims approximately 10 million lives annually. Despite advances in treatments such as surgery, chemotherapy, and immunotherapy, resistance to these methods has emerged. Multidrug resistance (MDR), where cancer cells resist diverse treatments, undermines therapy effectiveness, escalating mortality rates. MDR mechanisms include, among others, drug inactivation, reduced drug uptake, enhanced DNA repair, and activation of survival pathways such as autophagy. Moreover, MDR mechanisms can confer resistance to other therapies like radiotherapy. Understanding these mechanisms is crucial for improving treatment efficacy and identifying new therapeutic targets. Extracellular vesicles (EVs) have gathered attention for their role in cancer progression, including MDR development through protein transfer and genetic reprogramming. Autophagy, a process balancing cellular resources, also influences MDR. The intersection of EVs and autophagy further complicates the understanding of MDR. Both extracellular (exosomes, microvesicles) and intracellular (autophagic) vesicles contribute to therapy resistance by regulating the tumor microenvironment, facilitating cell communication, and modulating drug processing. While much is known about these pathways, there is still a need to explore their potential for predicting treatment responses and understanding tumor heterogeneity.

The role of immune checkpoints in antitumor response: a potential antitumor immunotherapy

Immunotherapy aims to stimulate the immune system to inhibit tumor growth or prevent metastases. Tumor cells primarily employ altered expression of human leukocyte antigen (HLA) as a mechanism to avoid immune recognition and antitumor immune response. The antitumor immune response is primarily mediated by CD8+ cytotoxic T cells (CTLs) and natural killer (NK) cells, which plays a key role in the overall anti-tumor immune response. It is crucial to comprehend the molecular events occurring during the activation and subsequent regulation of these cell populations. The interaction between antigenic peptides presented on HLA-I molecules and the T-cell receptor (TCR) constitutes the initial signal required for T cell activation. Once activated, in physiologic circumstances, immune checkpoint expression by T cells suppress T cell effector functions when the antigen is removed, to ensures the maintenance of self-tolerance, immune homeostasis, and prevention of autoimmunity. However, in cancer, the overexpression of these molecules represents a common method through which tumor cells evade immune surveillance. Numerous therapeutic antibodies have been developed to inhibit immune checkpoints, demonstrating antitumor activity with fewer side effects compared to traditional chemotherapy. Nevertheless, it's worth noting that many immune checkpoint expressions occur after T cell activation and consequently, altered HLA expression on tumor cells could diminish the clinical efficacy of these antibodies. This review provides an in-depth exploration of immune checkpoint molecules, their corresponding blocking antibodies, and their clinical applications.

Targeting the epigenome to reinvigorate T cells for cancer immunotherapy

Cancer immunotherapy using immune-checkpoint inhibitors (ICIs) has revolutionized the field of cancer treatment; however, ICI efficacy is constrained by progressive dysfunction of CD8+ tumor-infiltrating lymphocytes (TILs), which is termed T cell exhaustion. This process is driven by diverse extrinsic factors across heterogeneous tumor immune microenvironment (TIME). Simultaneously, tumorigenesis entails robust reshaping of the epigenetic landscape, potentially instigating T cell exhaustion. In this review, we summarize the epigenetic mechanisms governing tumor microenvironmental cues leading to T cell exhaustion, and discuss therapeutic potential of targeting epigenetic regulators for immunotherapies. Finally, we outline conceptual and technical advances in developing potential treatment paradigms involving immunostimulatory agents and epigenetic therapies.

Esophageal cancer cell-derived small extracellular vesicles decrease circulating Tfh/Tfr via sEV-PDL1 to promote immunosuppression

Esophageal cancer (EC) is a deadly malignancy. Small extracellular vesicles (sEVs) with programmed death ligand 1 (sEV-PDL1) induce immune escape to promote tumor progression. Furthermore, the imbalance between circulating follicular helper T (Tfh) and circulating follicular regulatory T (Tfr) cells is related to the progression of many malignant tumors. However, the role of the EC-derived sEV-PDL1 in circulating Tfh/Tfr is unknown. Circulating Tfh and Tfr cells were detected by flow cytometry. sEVs were isolated through differential centrifugation and cultured for cell expansion assays. Naïve CD4+ T cells were isolated, stimulated, and cultured with sEVs to evaluate the frequencies, phenotypes, and functions of Tfh and Tfr cells. The proportion of circulating Tfh in patients with EC was lower than that in healthy donors (HDs), whereas that of circulating Tfr was higher. The EC group showed significantly lower circulating Tfh/Tfr and a higher level of sEV-PDL1 than HDs. Notably, sEV-PDL1 was negatively correlated with circulating Tfh/Tfr in the EC group. In vitro assays, sEV-PDL1 inhibited Tfh expansion, enhanced the cytotoxic T lymphocyte-associated antigen 4+ (CTLA4+) Tfh cell percentage, decreased the levels of interleukin (IL)-21 and interferon-γ, and increased IL-10. sEV-PDL1 promoted the expansion and immunosuppressive functions of circulating Tfr; the increased percentages of CTLA4+ Tfr and inducible T cell co-stimulator+ Tfr were accompanied with high IL-10. However, applying an anti-PDL1 antibody significantly reversed this. Our results suggest a novel mechanism of sEV-PDL1-mediated immunosuppression in EC. Inhibiting sEV-PDL1 to restore circulating Tfh/Tfr balance provides a novel therapeutic approach for EC.

Engineered immunomodulatory extracellular vesicles derived from epithelial cells acquire capacity for positive and negative T cell co-stimulation in cancer and autoimmunity

Extracellular vesicles (EVs) are generated by all cells and systemic administration of allogenic EVs derived from epithelial and mesenchymal cells have been shown to be safe, despite carrying an array of functional molecules, including thousands of proteins. To address whether epithelial cells derived EVs can be modified to acquire the capacity to induce immune response, we engineered 293T EVs to harbor the immunomodulatory CD80, OX40L and PD-L1 molecules. We demonstrated abundant levels of these proteins on the engineered cells and EVs. Functionally, the engineered EVs efficiently elicit positive and negative co-stimulation in human and murine T cells. In the setting of cancer and auto-immune hepatitis, the engineered EVs modulate T cell functions and alter disease progression. Moreover, OX40L EVs provide additional benefit to anti-CTLA-4 treatment in melanoma-bearing mice. Our work provides evidence that epithelial cell derived EVs can be engineered to induce immune responses with translational potential to modulate T cell functions in distinct pathological settings.

Exosome-mediated crosstalk between tumor cells and innate immune cells: implications for cancer progression and therapeutic strategies

The increasing number of cancer-associated deaths despite the substantial improvement in diagnosis and treatment has sparked discussions on the need for novel biomarkers and therapeutic strategies for cancer. Exosomes have become crucial players in tumor development and progression, largely due to the diverse nature of their cargo content released to recipient cells. Importantly, exosome-mediated crosstalk between tumor and stromal cells is essential in reprogramming the tumor microenvironment to facilitate tumor progression. As a result, exosomes have gradually become a marker for the early diagnosis of many diseases and an important tool in drug delivery systems. However, the precise mechanisms by which exosomes participate in tumor progression remain elusive, multifaceted, and a double-edged sword, thus requiring further clarification. The available evidence suggests that exosomes can facilitate communication between innate immune cells and tumor cells to either support or inhibit tumor progression. Herein, this review focused on exosome-mediated intercellular communication between tumor cells and macrophages, neutrophils, mast cells, monocytes, dendritic cells, and natural killer cells. Specifically, how such intercellular communication affects tumor progression has been described. It has also been discussed that, depending on their cargo, exosomes can suppress or promote tumor cell progression. In addition, the potential application of exosomes and strategies to target exosomes in cancer treatment has been comprehensively discussed.

Exosome nanovesicles as potential biomarkers and immune checkpoint signaling modulators in lung cancer microenvironment: recent advances and emerging concepts

Lung cancer remains the leading cause of cancer-related deaths globally, and the survival rate remains low despite advances in diagnosis and treatment. The progression of lung cancer is a multifaceted and dynamic phenomenon that encompasses interplays among cancerous cells and their microenvironment, which incorporates immune cells. Exosomes, which are small membrane-bound vesicles, are released by numerous cell types in normal and stressful situations to allow communication between cells. Tumor-derived exosomes (TEXs) possess diverse neo-antigens and cargoes such as proteins, RNA, and DNA and have a unique molecular makeup reflecting tumor genetic complexity. TEXs contain both immunosuppressive and immunostimulatory factors and may play a role in immunomodulation by influencing innate and adaptive immune components. Moreover, they transmit signals that contribute to the progression of lung cancer by promoting metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, and immunosuppression. This makes them a valuable resource for investigating the immune environment of tumors, which could pave the way for the development of non-invasive biomarkers that could aid in the prognosis, diagnosis, and immunotherapy of lung cancer. While immune checkpoint inhibitor (ICI) immunotherapy has shown promising results in treating initial-stage cancers, most patients eventually develop adaptive resistance over time. Emerging evidence demonstrates that TEXs could serve as a prognostic biomarker for immunotherapeutic response and have a significant impact on both systemic immune suppression and tumor advancement. Therefore, understanding TEXs and their role in lung cancer tumorigenesis and their response to immunotherapies is an exciting research area and needs further investigation. This review highlights the role of TEXs as key contributors to the advancement of lung cancer and their clinical significance in lung immune-oncology, including their possible use as biomarkers for monitoring disease progression and prognosis, as well as emerging shreds of evidence regarding the possibility of using exosomes as targets to improve lung cancer therapy.

Immune checkpoint inhibition mediated with liposomal nanomedicine for cancer therapy

Immune checkpoint blockade (ICB) therapy for cancer has achieved great success both in clinical results and on the market. At the same time, success drives more attention from scientists to improve it. However, only a small portion of patients are responsive to this therapy, and it comes with a unique spectrum of side effects termed immune-related adverse events (irAEs). The use of nanotechnology could improve ICBs' delivery to the tumor, assist them in penetrating deeper into tumor tissues and alleviate their irAEs. Liposomal nanomedicine has been investigated and used for decades, and is well-recognized as the most successful nano-drug delivery system. The successful combination of ICB with liposomal nanomedicine could help improve the efficacy of ICB therapy. In this review, we highlighted recent studies using liposomal nanomedicine (including new emerging exosomes and their inspired nano-vesicles) in associating ICB therapy.

Circulating exosomal immuno-oncological checkpoints and cytokines are potential biomarkers to monitor tumor response to anti-PD-1/PD-L1 therapy in non-small cell lung cancer patients

Immune checkpoint inhibitors (ICIs) including anti-PD-1 and anti-PD-L1 antibodies, have significantly changed the treatment outcomes of NSCLC patients with better overall survival. However, 15-40% of the patients still fail to respond to ICIs therapy. Identification of biomarkers associated with responses are mandated in order to increase the efficacy of such therapy. In this study we evaluated 27 serum-derived exosomal immuno-oncological proteins and 44 cytokines/chemokines before and after ICIs therapy in 17 NSCLC patients to identify surrogate biomarkers for treatment/monitoring patient stratification for maximum therapeutic benefit. We first confirmed the identity of the isolated exosomes to have their specific markers (CD63, CD81, HSP70 and CD91). We have demonstrated that baseline concentration of exosomal-PD-L1 (p<0.0001), exosomal-PD-L2 (p=0.0413) and exosomal-PD-1 (p=0.0131) from NSCLC patients were significantly higher than their soluble-free forms. Furthermore, the exosomal-PD-L1 was present in all the patients (100%), while only 71% of patients expressed tissue PD-L1. This indicates that exosomal-PD-L1 is a more reliable diagnostic biomarker. Interestingly, exosomal-PD-L2 expression was significantly higher (p=0.0193) in tissue PD-L1-negative patients compared to tissue PD-L1-positive patients. We have also shown that immuno-oncological proteins isolated from pre-ICIs treated patients were significantly higher in exosomes compared to their soluble-free counterparts (CD152, p=0.0008; CD80, p=0.0182; IDO, p=0.0443; Arginase, p<0.0001; Nectin-2, p<0.0001; NT5E, p<0.0001; Siglec-7, p<0.0001; Siglec-9, p=0.0335; CD28, p=0.0092; GITR, p<0.0001; MICA, p<0.0001). Finally, the changes in the expression levels of exosomal immuno-oncological proteins/cytokines and their correlation with tumor response to ICIs treatment were assessed. There was a significant downregulation of exosomal PD-L1 (p=0.0156), E-Cadherin (p=0.0312), ULBP1 (p=0.0156), ULBP3 (p=0.0391), MICA (p=0.0391), MICB (p=0.0469), Siglec7 (p=0.0078) and significant upregulation of exosomal PD-1 (p=0.0156) and IFN- γ (p=0.0156) in responding patients. Non-responding patients showed a significant increase in exosomal-PD-L1 (p=0.0078). Furthermore, responding-patients without liver-metastasis showed significant-upregulation of PD-1 (p=0.0070), and downregulation of ULBP1 (p=0.0137) and Siglec-7 (p=0.0037). Non-responding patients had significant-downregulation of ULBP3 (p=0.0317) in patient without brain-metastasis and significant-upregulation/downregulation of PD-L1 and ULBP3 (p=0.0262/0.0286) in patients with pulmonary-metastasis. We demonstrated for the first time that exosomal immuno-oncological proteins/cytokines are potential biomarkers to monitor response to ICIs therapy and can predict the clinical outcomes in NSCLC patients.

Nanomedicine-boosting icaritin-based immunotherapy of advanced hepatocellular carcinoma

Traditional treatments for advanced hepatocellular carcinoma (HCC), such as surgical resection, transplantation, radiofrequency ablation, and chemotherapy are unsatisfactory, and therefore the exploration of powerful therapeutic strategies is urgently needed. Immunotherapy has emerged as a promising strategy for advanced HCC treatment due to its minimal side effects and long-lasting therapeutic memory effects. Recent studies have demonstrated that icaritin could serve as an immunomodulator for effective immunotherapy of advanced HCC. Encouragingly, in 2022, icaritin soft capsules were approved by the National Medical Products Administration (NMPA) of China for the immunotherapy of advanced HCC. However, the therapeutic efficacy of icaritin in clinical practice is impaired by its poor bioavailability and unfavorable in vivo delivery efficiency. Recently, functionalized drug delivery systems including stimuli-responsive nanocarriers, cell membrane-coated nanocarriers, and living cell-nanocarrier systems have been designed to overcome the shortcomings of drugs, including the low bioavailability and limited delivery efficiency as well as side effects. Taken together, the development of icaritin-based nanomedicines is expected to further improve the immunotherapy of advanced HCC. Herein, we compared the different preparation methods for icaritin, interpreted the HCC immune microenvironment and the mechanisms underlying icaritin for treatment of advanced HCC, and discussed both the design of icaritin-based nanomedicines with high icaritin loading and the latest progress in icaritin-based nanomedicines for advanced HCC immunotherapy. Finally, the prospects to promote further clinical translation of icaritin-based nanomedicines for the immunotherapy of advanced HCC were proposed.

Temsirolimus Enhances Anti-Cancer Immunity by Inducing Autophagy-Mediated Degradation of the Secretion of Small Extracellular Vesicle PD-L1

Simple Summary

Immune checkpoint blockade therapies (ICBT) have increasing importance in patient survival and prognosis because it enhances immune cell activation by inhibiting the binding of programmed death-ligand 1 (PD-L1) of tumor and programmed death-1 (PD-1) of T cells. However, tumor-derived small extracellular vesicle (sEV) PD-L1 trigger low reactivity in immunotherapy because it promotes tumor growth and metastasis and inhibits activation of immune cell. In this study, temsirolimus (TEM) which the Food and Drug Administration (FDA) approved as a targeted anti-cancer drug, inhibited tumor-derived sEV PD-L1 secretion by activating autophagy. In addition, TEM induced systemic anti-cancer immunity by increasing the number and activation of CD4⁺ and CD8⁺ T cells. Therefore, TEM showed that the anti-cancer effect was better in the breast cancer-bearing-immunocompetent mice than in the nude mice. In summary, we suggest that TEM can overcome sEV PD-L1-mediated immunosuppression in patients with cancer through activation of the immune system in the body by inhibiting tumor-derived sEV PD-L1.

Abstract

Tumor-derived small extracellular vesicle (sEV) programmed death-ligand 1 (PD-L1) contributes to the low reactivity of cells to immune checkpoint blockade therapy (ICBT), because sEV PD-L1 binds to programmed death 1 (PD-1) in immune cells. However, there are no commercially available anti-cancer drugs that activate immune cells by inhibiting tumor-derived sEV PD-L1 secretion and cellular PD-L1. Here, we aimed to investigate if temsirolimus (TEM) inhibits both sEV PD-L1 and cellular PD-L1 levels in MDA-MB-231 cells. In cancer cell autophagy activated by TEM, multivesicular bodies (MVBs) associated with the secretion of sEV are degraded through colocalization with autophagosomes or lysosomes. TEM promotes CD8⁺ T cell-mediated anti-cancer immunity in co-cultures of CD8⁺ T cells and tumor cells. Furthermore, the combination therapy of TEM and anti-PD-L1 antibodies enhanced anti-cancer immunity by increasing both the number and activity of CD4⁺ and CD8⁺ T cells in the tumor and draining lymph nodes (DLNs) of breast cancer-bearing immunocompetent mice. In contrast, the anti-cancer effect of the combination therapy with TEM and anti-PD-L1 antibodies was reversed by the injection of exogenous sEV PD-L1. These findings suggest that TEM, previously known as a targeted anti-cancer drug, can overcome the low reactivity of ICBT by inhibiting sEV PD-L1 and cellular PD-L1 levels.

Macrophage Differentiation and Polarization Regulate the Release of the Immune Checkpoint Protein V-Domain Ig Suppressor of T Cell Activation

Recently, the V-domain immunoglobulin suppressor of T-cell activation (VISTA) was identified as a negative immune checkpoint regulator (NCR) that is mainly expressed in hematopoietic cells. Preclinical studies have shown that VISTA blockade results in impeded tumor growth and improved survival. Nevertheless, little is known about the physiological role of VISTA expression in macrophages. This study focused on the differential expression of VISTA in human monocytes and macrophages in order to elucidate a putative role of VISTA regulation upon macrophage polarization and activation. We observed that human peripheral monocytes constitutively release soluble VISTA, which was regulated via matrix metalloproteinases. However, monocyte stimulation with cytokines that induce macrophage differentiation, such as granulocyte-macrophage colony–stimulating (GM-CSF) and macrophage colony-stimulating factor (M-CSF), substantially reduced soluble VISTA release. VISTA release was further affected by various pro- and anti-inflammatory stimuli that led to macrophage polarization, where activated M1 macrophages generally released more VISTA than M2 macrophages. Additionally, we observed that stimulation of activated macrophages with the toll-like receptor 4 ligand lipopolysaccharide (LPS) led to a further decrease of soluble VISTA release. Moreover, we found that soluble VISTA impairs T cell cytotoxic activity but did not induce their programmed death. Our results suggest that VISTA is constantly produced and released in the peripheral blood where it may contribute to peripheral tolerance.

Estrogens, Cancer and Immunity

Sex hormones are included in many physiological and pathological pathways. Estrogens belong to steroid hormones active in female sex. Estradiol (E2) is the strongest female sex hormone and, with its receptors, contributes to oncogenesis, cancer progression and response to treatment. In recent years, a role of immunosurveillance and suppression of immune response in malignancy has been well defined, forming the basis for cancer immunotherapy. The interplay of sex hormones with cancer immunity, as well as the response to immune checkpoint inhibitors, is of interest. In this review, we investigate the impact of sex hormones on natural immune response with respect to main active elements in anticancer immune surveillance: dendritic cells, macrophages, lymphocytes and checkpoint molecules. We describe the main sex-dependent tumors and the contribution of estrogen in their progression, response to treatment and especially modulation of anticancer immune response.

Pan-Cancer Study on Protein Kinase C Family as a Potential Biomarker for the Tumors Immune Landscape and the Response to Immunotherapy

The protein kinase C (PKC) family has been described with its role in some cancers, either as a promoter or suppressor. PKC signaling also regulates a molecular switch between transactivation and transrepression activity of the peroxisome proliferator-activated receptor alpha (PPARalpha). However, the role of different PKC enzymes in tumor immunity remains poorly defined. This study aims to investigate the correlation between PKC genes and tumor immunity, in addition to studying the probability of their use as predictive biomarkers for tumor immunity and immunotherapeutic response. The ssGSEA and the ESTIMATE methods were used to assess 28 tumor-infiltrating lymphocytes (TILs) and the immune component of each cancer, then correlated with PKC levels. Prediction of PKC levels-dependent immunotherapeutic response was based on human leukocytic antigen (HLA) gene enrichment scores and programmed cell death 1 ligand (PD-L1) expression. Univariate and multivariate Cox analysis was performed to evaluate the prognostic role of PKC genes in cancers. Methylation level and CNAs could drive the expression levels of some PKC members, especially PRKCI, whose CNGs are predicted to elevate their level in many cancer types. The most crucial finding in this study was that PKC isoenzymes are robust biomarkers for the tumor immune status, PRKCB, PRKCH, and PRKCQ as stimulators, while PRKCI and PRKCZ as inhibitors in most cancers. Also, PKC family gene levels can be used as predictors for the response to immunotherapies, especially HLAs dependent and PD-L1 blockade-dependent ones. In addition to its prognostic function, all PKC family enzymes are promising tumor immunity biomarkers and can help select suitable immune therapy in different cancers.

Tumor-Derived Exosomes in Tumor-Induced Immune Suppression

Exosomes are a class of small membrane-bound extracellular vesicles released by almost all cell types and present in all body fluids. Based on the studies of exosome content and their interactions with recipient cells, exosomes are now thought to mediate "targeted" information transfer. Tumor-derived exosomes (TEX) carry a cargo of molecules different from that of normal cell-derived exosomes. TEX functions to mediate distinct biological effects such as receptor discharge and intercellular cross-talk. The immune system defenses, which may initially restrict tumor progression, are progressively blunted by the broad array of TEX molecules that activate suppressive pathways in different immune cells. Herein, we provide a review of the latest research progress on TEX in the context of tumor-mediated immune suppression and discuss the potential as well as challenges of TEX as a target of immunotherapy.