The immunosuppressive tumour network: myeloid-derived suppressor cells, regulatory T cells and natural killer T cells

Myeloid-derived suppressor cells (MDSC): an important partner in cellular/tissue senescence

The aging process is associated with a low-grade chronic inflammation and the accumulation of senescent cells into tissues. Diverse stresses can trigger cellular senescence, a cell fate characterized by cell-cycle arrest and flat morphology. Oncogenic signaling can also induce cellular senescence which has been termed oncogene-induced senescence (OIS). Senescent cells display a pro-inflammatory phenotype which has been called the senescence-associated secretory phenotype (SASP). The secretomes associated with SASP contain colony-stimulating factors and chemokines which stimulate the generation of myeloid-derived suppressor cells (MDSC) by enhancing myelopoiesis in bone marrow and spleen. Enhanced myelopoiesis and increased level of MDSCs have been observed in bone marrow, spleen, and blood in both tumor-bearing and aged mice. Immunosuppressive MDSCs are recruited via chemotaxis into inflamed tissues where they proliferate and consequently suppress acute inflammatory reactions by inhibiting the functions of distinct components of innate and adaptive immunity. For instance, MDSCs stimulate the activity of immunosuppressive regulatory T-cells (Tregs). They also increase the expression of amino acid catabolizing enzymes and the secretion of anti-inflammatory cytokines, e.g. IL-10 and TGF-β, and reactive oxygen species (ROS). On the other hand, the accumulation of MDSCs into tissues exerts harmful effects in chronic pathological disorders, e.g. tumors and many age-related diseases, since the immunosuppression induced by MDSCs impairs the clearance of senescent and cancer cells and also disturbs the maintenance of energy metabolism and tissue proteostasis. The co-operation between senescent cells and immunosuppressive MDSCs regulates not only tumorigenesis and chronic inflammatory disorders but it also might promote inflammaging during the aging process.

The Role of Invariant NKT in Autoimmune Liver Disease: Can Vitamin D Act as an Immunomodulator?

Natural killer T (NKT) cells are a distinct lineage of T cells which express both the T cell receptor (TCR) and natural killer (NK) cell markers. Invariant NKT (iNKT) cells bear an invariant TCR and recognize a small variety of glycolipid antigens presented by CD1d (nonclassical MHC-I). CD1d-restricted iNKT cells are regulators of immune responses and produce cytokines that may be proinflammatory (such as interferon-gamma (IFN-γ)) or anti-inflammatory (such as IL-4). iNKT cells also appear to play a role in B cell regulation and antibody production. Alpha-galactosylceramide (α-GalCer), a derivative of the marine sponge, is a potent stimulator of iNKT cells and has been proposed as a therapeutic iNKT cell activator. Invariant NKT cells have been implicated in the development and perpetuation of several autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus (SLE). Animal models of SLE have shown abnormalities in iNKT cells numbers and function, and an inverse correlation between the frequency of NKT cells and IgG levels has also been observed. The role of iNKT cells in autoimmune liver disease (AiLD) has not been extensively studied. This review discusses the current data with regard to iNKT cells function in AiLD, in addition to providing an overview of iNKT cells function in other autoimmune conditions and animal models. We also discuss data regarding the immunomodulatory effects of vitamin D on iNKT cells, which may serve as a potential therapeutic target, given that deficiencies in vitamin D have been reported in various autoimmune disorders.

Granulocyte-Colony Stimulating Factor-Overexpressing Mesenchymal Stem Cells Exhibit Enhanced Immunomodulatory Actions Through the Recruitment of Suppressor Cells in Experimental Chagas Disease Cardiomyopathy

Genetic modification of mesenchymal stem cells (MSCs) is a promising strategy to improve their therapeutic effects. Granulocyte-colony stimulating factor (G-CSF) is a growth factor widely used in the clinical practice with known regenerative and immunomodulatory actions, including the mobilization of regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Here we evaluated the therapeutic potential of MSCs overexpressing G-CSF (MSC_G-CSF) in a model of inflammatory cardiomyopathy due to chronic Chagas disease. C57BL/6 mice were treated with wild-type MSCs, MSC_G-CSF, or vehicle (saline) 6 months after infection with Trypanosoma cruzi. Transplantation of MSC_G-CSF caused an increase in the number of circulating leukocytes compared to wild-type MSCs. Moreover, G-CSF overexpression caused an increase in migration capacity of MSCs to the hearts of infected mice. Transplantation of either MSCs or MSC_G-CSF improved exercise capacity, when compared to saline-treated chagasic mice. MSC_G-CSF mice, however, were more potent than MSCs in reducing the number of infiltrating leukocytes and fibrosis in the heart. Similarly, MSC_G-CSF-treated mice presented significantly lower levels of inflammatory mediators, such as IFNγ, TNFα, and Tbet, with increased IL-10 production. A marked increase in the percentage of Tregs and MDSCs in the hearts of infected mice was seen after administration of MSC_G-CSF, but not MSCs. Moreover, Tregs were positive for IL-10 in the hearts of T. cruzi-infected mice. In vitro analysis showed that recombinant hG-CSF and conditioned medium of MSC_G-CSF, but not wild-type MSCs, induce chemoattraction of MDSCs in a transwell assay. Finally, MDSCs purified from hearts of MSC_G-CSF transplanted mice inhibited the proliferation of activated splenocytes in a co-culture assay. Our results demonstrate that G-CSF overexpression by MSCs potentiates their immunomodulatory effects in our model of Chagas disease and suggest that mobilization of suppressor cell populations such as Tregs and MDSCs as a promising strategy for the treatment of chronic Chagas disease. Finally, our results reinforce the therapeutic potential of genetic modification of MSCs, aiming at increasing their paracrine actions.

Advances in NKT cell Immunotherapy for Glioblastoma

Type I or invariant natural killer T cells belong to a unique lineage of innate T cells, which express markers of both T lymphocytes and NK cells, namely T cell receptor (TCR) and NK1.1 (CD161C), respectively. Thus, apart from direct killing of target cells like NK cells, and they also produce a myriad of cytokines which modulate the adaptive immune responses. Unlike traditional T cells which carry a conventional αβ TCR, NKT cells express semi-invariant TCR - Vα14-Jα18, coupled with Vβ8, Vβ7 and Vβ2 in mice. In humans, the invariant TCR is composed of Vα24-Jα18, coupled with Vβ11.

LncRNA MALAT1 negatively regulates MDSCs in patients with lung cancer

Myeloid-derived suppressor cells (MDSCs) have strong immunosuppressive functions and contribute to the formation of the tumor microenvironment. Long non-coding (Lnc) RNAs are highly important factors associated with tumors and may be used as markers for tumor diagnosis, which is valuable for targeted therapy. LncRNA MALAT1 is expressed in various tissues and plays a critical role in cell proliferation, including tumorigenesis and metastasis. However, the role of MALAT1 in MDSCs is unclear. In this study, we observed an increased proportion of MDSCs and elevated levels of the related molecule arginase-1 (ARG-1) in peripheral blood mononuclear cells (PBMCs) obtained from lung cancer patients. The proportion of CD8⁺ cytotoxic T lymphocyte (CTL) was significantly decreased in PBMCs from lung cancer patients. Moreover, the proportion of CTL cells was negatively correlated with the proportion of MDSCs. Furthermore, MALAT1 levels were decreased in PBMCs from lung cancer patients. The relative expression of MALAT1 was moderate negatively correlated with the proportion of MDSCs. In vitro results indicate that the knockdown of MALAT1 significantly increased the proportion of MDSCs. Our data provide the first evidence that lncRNA MALAT1 negatively regulates MDSCs and is decreased in PBMCs from lung cancer patients.

Nano-delivery of fraxinellone remodels tumor microenvironment and facilitates therapeutic vaccination in desmoplastic melanoma

Rationale: Tumor-associated fibroblasts (TAFs) play a critical role in the suppressive immune tumor microenvironment (TME), compromising the efficacy of immunotherapy. To overcome this therapeutic hurdle, we developed a nanoemulsion (NE) formulation to deliver fraxinellone (Frax), an anti-fibrotic medicine, to TAFs, as an approach to reverse immunosuppressive TME of desmoplastic melanoma. Methods: Frax NE was prepared by an ultrasonic emulsification method. The tumor inhibition effect was evaluated by immunofluorescence staining, masson trichrome staining and western blot analysis. Immune cell populations in tumor and LNs were detected by flow cytometry. Results: This Frax NE, with a particle size of around 145 nm, can efficiently accumulate in the tumor site after systemic administration and was taken up by TAFs and tumor cells. A significant decrease in TAFs and stroma deposition was observed after intravenous administration of Frax NE, and Frax NE treatment also remolded the tumor immune microenvironment, as was reflected by an increase of natural-killer cells, cytotoxic T cells (CTLs) as well as a decrease of regulatory B cells, and myeloid-derived suppressor cells in the TME. In addition, after treatment by Frax NEs, T helper 1 (Th1) cytokines of interferon gamma (IFN-γ), which effectively elicit anti-tumor immunity, were enhanced. Transforming growth factor-β (TGF-β), chemokine (C-C motif) ligand 2 (CCL2) and interleukin 6 (IL6), which inhibit the development of anti-tumor immunity, were reduced. Although Frax NE demonstrated an inhibitory effect on tumor growth, this mono-therapy could only achieve partial antitumor efficacy, and the tumor growth effect was not maintained long-term after dosing stopped. Therefore, a tumor-specific peptide vaccine was combined with Frax NEs. The combination led to enhanced tumor-specific T-cell infiltration, activated death receptors on the tumor cell surface, and induced increased apoptotic tumor cell death. Conclusion: Collectively, Frax NE combined with tumor-specific peptide vaccine might be an effective and safe strategy to remodel fibrotic TME, thereby enhancing immune response activation, resulting in a prolonged efficiency for advanced desmoplastic melanoma.

Microarray analysis of long non-coding RNA expression profiles in monocytic myeloid-derived suppressor cells in Echinococcus granulosus-infected mice

Background

Cystic echinococcosis is a worldwide chronic zoonotic disease caused by infection with the larval stage of Echinococcus granulosus. Previously, we found significant accumulation of myeloid-derived suppressor cells (MDSCs) in E. granulosus infection mouse models and that they play a key role in immunosuppressing T lymphocytes. Here, we compared the long non-coding RNA (lncRNA) and mRNA expression patterns between the splenic monocytic MDSCs (M-MDSCs) of E. granulosus protoscoleces-infected mice and normal mice using microarray analysis.

Methods

LncRNA functions were predicted using Gene Ontology enrichment and the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Cis- and trans-regulation analyses revealed potential relationships between the lncRNAs and their target genes or related transcription factors.

Results

We found that 649 lncRNAs were differentially expressed (fold change ≥ 2, P < 0.05): 582 lncRNAs were upregulated and 67 lncRNAs were downregulated; respectively, 28 upregulated mRNAs and 1043 downregulated mRNAs were differentially expressed. The microarray data was validated by quantitative reverse transcription-PCR. The results indicated that mRNAs co-expressed with the lncRNAs are mainly involved in regulating the actin cytoskeleton, Salmonella infection, leishmaniasis, and the vascular endothelial growth factor (VEGF) signaling pathway. The lncRNA NONMMUT021591 was predicted to cis-regulate the retinoblastoma gene (Rb1), whose expression is associated with abnormal M-MDSCs differentiation. We found that 372 lncRNAs were predicted to interact with 60 transcription factors; among these, C/EBPβ (CCAAT/enhancer binding protein beta) was previously demonstrated to be a transcription factor of MDSCs.

Conclusions

Our study identified dysregulated lncRNAs in the M-MDSCs of E. granulosus infection mouse models; they might be involved in M-MDSC-derived immunosuppression in related diseases.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2905-6) contains supplementary material, which is available to authorized users.

Elevated peripheral blood B lymphocytes and CD3+CD4-CD8- T lymphocytes in patients with non-small cell lung cancer: A preliminary study on peripheral immune profile

It has been established that the tumor microenvironment (TME) has a crucial role in enabling tumors to evade from host immune responses. Previous studies demonstrated that tumor cells are not only able to reshape immune milieu at the tumor site, but also exert systemic effects, which has been demonstrated to be important for metastasis. At present, how the peripheral immune environment change in the tumor-bearing host is unclear. The present study identified a number of changes in the proportions of lymphocyte subpopulations and the levels of cytokines in patients with NSCLC, which may provide a preliminary profile of the immune environment in the peripheral blood of patients harboring a tumor. These findings expand on the present knowledge on how tumors can alter the immune system to benefit its growth and metastasis, which may provide a potential novel strategy for immunotherapy.

Antitumor Immunity Is Controlled by Tetraspanin Proteins

Antitumor immunity is shaped by the different types of immune cells that are present in the tumor microenvironment (TME). In particular, environmental signals (for instance, soluble factors or cell–cell contact) transmitted through the plasma membrane determine whether immune cells are activated or inhibited. Tetraspanin proteins are emerging as central building blocks of the plasma membrane by their capacity to cluster immune receptors, enzymes, and signaling molecules into the tetraspanin web. Whereas some tetraspanins (CD81, CD151, CD9) are widely and broadly expressed, others (CD53, CD37, Tssc6) have an expression pattern restricted to hematopoietic cells. Studies using genetic mouse models have identified important immunological functions of these tetraspanins on different leukocyte subsets, and as such, may be involved in the immune response against tumors. While multiple studies have been performed with regards to deciphering the function of tetraspanins on cancer cells, the effect of tetraspanins on immune cells in the antitumor response remains understudied. In this review, we will focus on tetraspanins expressed by immune cells and discuss their potential role in antitumor immunity. New insights in tetraspanin function in the TME and possible prognostic and therapeutic roles of tetraspanins will be discussed.

Non-Cell Autonomous Effects of the Senescence-Associated Secretory Phenotype in Cancer Therapy

In addition to promoting various forms of cell death, most conventional anti-tumor therapies also promote senescence. There is now extensive evidence that therapy-induced senescence (TIS) might be transient, raising the concern that TIS could represent an undesirable outcome of therapy by providing a mechanism for tumor dormancy and eventual disease recurrence. The senescence-associated secretory phenotype (SASP) is a hallmark of TIS and may contribute to aberrant effects of cancer therapy. Here, we propose that the SASP may also serve as a major driver of escape from senescence and the re-emergence of proliferating tumor cells, wherein factors secreted from the senescent cells contribute to the restoration of tumor growth in a non-cell autonomous fashion. Accordingly, anti-SASP therapies might serve to mitigate the deleterious outcomes of TIS. In addition to providing an overview of the putative actions of the SASP, we discuss recent efforts to identify and eliminate senescent tumor cells.

Extracellular vesicles: important collaborators in cancer progression

Extracellular vesicles (EVs) are membrane vesicles that are released from cells and mediate cell-cell communication. EVs carry protein, lipid, and nucleic acid cargoes that interact with recipient cells to alter their phenotypes. Evidence is accumulating that tumor-derived EVs can play important roles in all steps of cancer progression. Here, we review recent studies reporting critical roles for EVs in four major areas of cancer progression: promotion of cancer invasiveness and motility, enhancement of angiogenesis and vessel permeability, conditioning premetastatic niches, and immune suppression.

Myeloid-Derived Suppressor Cells Impair B Cell Responses in Lung Cancer through IL-7 and STAT5

Myeloid-derived suppressor cells (MDSCs) are known suppressors of antitumor immunity, affecting amino acid metabolism and T cell function in the tumor microenvironment. However, it is unknown whether MDSCs regulate B cell responses during tumor progression. Using a syngeneic mouse model of lung cancer, we show reduction in percentages and absolute numbers of B cell subsets including pro-, pre-, and mature B cells in the bone marrow (BM) of tumor-bearing mice. The kinetics of this impaired B cell response correlated with the progressive infiltration of MDSCs. We identified that IL-7 and downstream STAT5 signaling that play a critical role in B cell development and differentiation were also impaired during tumor progression. Global impairment of B cell function was indicated by reduced serum IgG levels. Importantly, we show that anti-Gr-1 Ab-mediated depletion of MDSCs not only rescued serum IgG and IL-7 levels but also reduced TGF-β1, a known regulator of stromal IL-7, suggesting MDSC-mediated regulation of B cell responses. Furthermore, blockade of IL-7 resulted in reduced phosphorylation of downstream STAT5 and B cell differentiation in tumor-bearing mice and administration of TGF-β-blocking Ab rescued these IL-7-dependent B cell responses. Adoptive transfer of BM-derived MDSCs from tumor-bearing mice into congenic recipients resulted in significant reductions of B cell subsets in the BM and in circulation. MDSCs also suppressed B cell proliferation in vitro in an arginase-dependent manner that required cell-to-cell contact. Our results indicate that tumor-infiltrating MDSCs may suppress humoral immune responses and promote tumor escape from immune surveillance.

A new prognostic model using the NCCN-IPI and neutrophil-to-lymphocyte ratio in diffuse large B-cell lymphoma

BACKGROUND

The neutrophil-to-lymphocyte ratio (NLR) has been known to predict the prognosis in diffuse large B-cell lymphoma (DLBCL). We planned to design a new prognostic model in DLBCL using well-known prognostic index and NLR.

METHODS

The data of 232 DLBCL patients treated with first-line R-CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) from 2004 to 2017 were retrospectively reviewed. Patients with NLR ≥6 and <6 were determined as the high and low NLR groups, respectively. Treatment response and survival were compared according to NLR status. Nomograms for predicting 5-year progression-free survival (PFS) and overall survival (OS) rates were constructed using NLR and other prognostic factors based on the National Comprehensive Cancer Network-International Prognostic Index (NCCN-IPI) NCCN-IPI.

RESULTS

The high NLR group had a low complete response (CR) rate compared to low NLR group (51.6% vs. 83.5%; p<0.001). The 5-year PFS and OS rates were 27.4% and 30% in the high NLR group and 61.1% and 63.7% in the low NLR group, respectively (both p<0.001). Multivariate analyses confirmed that NLR is one of the independent risk factors for failure to achieve CR and for worse PFS and OS. The nomogram showed superior discrimination ability for predicting 5-year PFS and OS rates compared with NCCN-IPI (c index 0.78 vs. 0.75 and 0.79 vs. 0.75, respectively).

CONCLUSIONS

High NLR was associated with poor treatment response and worse PFS and OS in DLBCL. The nomogram developed from NCCN-IPI-based variables and NLR may help the clinicians to predict the prognosis individually in DLBCL patients, although it needs to be validated in the independent cohort.

Immune system augmentation via humanization using stem/progenitor cells and bioengineering in a breast cancer model study

Despite significant advances, most current in vivo models fail to fully recapitulate the biological processes that occur in humans. Here we aimed to develop an advanced humanized model with features of an organ bone by providing different bone tissue cellular compartments including preosteoblasts, mesenchymal stem/stromal (MSCs), endothelial and hematopoietic cells in an engineered microenvironment. The bone compartment was generated by culturing the human MSCs, umbilical vein endothelial cells with gelatin methacryloyl hydrogels in the center of a melt-electrospun polycaprolactone tubular scaffolds, which were seeded with human preosteoblasts. The tissue engineered bone (TEB) was subcutaneously implanted into the NSG mice and formed a morphologically and functionally organ bone. Mice were further humanized through the tail vein injection of human cord blood derived CD34+ cells, which then populated in the mouse bone marrow, spleen and humanized TEB (hTEB). 11 weeks after CD34+ transplantation, metastatic breast cancer cells (MDA-MB-231BO) were orthotopically injected. Cancer cell injection resulted in the formation of a primary tumor and metastasis to the hTEB and mouse organs. Less frequent metastasis and lower tumor burden were observed in hematochimeric mice, suggesting an immune-mediated response against the breast cancer cells. Overall, our results demonstrate the efficacy of tissue engineering approaches to study species-specific cancer-bone interactions. Further studies using genetically modified hematopoietic stem cells and bioengineered microenvironments will enable us to address the specific roles of signaling molecules regulating hematopoietic niches and cancer metastasis in vivo.

Intratumoral depletion of regulatory T cells using CD25-targeted photodynamic therapy in a mouse melanoma model induces antitumoral immune responses

Tumor immunotherapy aims to overcome the immunosuppressive microenvironment within tumors, and various approaches have been developed. Tumor-associated T regulatory cells (Tregs) suppress the activation and expansion of tumor antigen-specific effector T cells, thus, providing a permissive environment for tumor growth. Therefore, optimal strategies need to be established to deplete tumor-infiltrated Tregs because systemic depletion of Tregs can result in reduced anti-tumor effector cells and autoimmunity. Here, to selectively deplete Tregs in tumors, we intratumorally injected anti-CD25 antibodies conjugated to Chlorin e6 (Ce6), a photosensitizer that absorbs light to generate reactive oxygen species. Local depletion of tumor-associated Tregs with photodynamic therapy (PDT) inhibited tumor growth, which was likely due to the altered tumor immune microenvironment that was characterized by increased infiltration of CD8+ effector T cells and the expression of IFN-γ and CD107a, which is a cytolytic granule exocytosis marker in tumor tissues. Furthermore, PDT-induced intratumoral Treg depletion did not influence adaptive immune responses in a murine influenza infection model. Thus, our results show that intratumoral Treg-targeted PDT could specifically modulate tumor microenvironments by depleting Tregs and could be used as a novel cancer immunotherapy technique.

Redirecting tumor-associated macrophages to become tumoricidal effectors as a novel strategy for cancer therapy

Cancer research in recent decades has highlighted the potential influence of the tumor microenvironment on the progression and metastasis of most known cancer types. Within the established microenvironment, tumor-associated macrophages (TAMs) are one of the most abundant and crucial non-neoplastic cell types. The polarization of macrophages into tumor-suppressive M1 or tumor-promoting M2 types is a fundamental event in the establishment of the tumor microenvironment. Although ample evidence indicates that TAMs are primarily M2 polarized, the mechanisms responsible for the regulation and maintenance of M1 and M2 polarization imbalance remain unclear. The manipulation of this critical axis through three main approaches may provide new strategies for cancer therapy - (I) specific interference with M2-like TAM survival or inhibiting their signaling cascades, (II) repression of macrophage recruitment to tumors, and (III) repolarization of tumor-promoting M2-like TAMs to a tumoricidal M1-like phenotype. This review summarizes current strategies for cancer intervention via manipulation of macrophage polarization, with particular focus on composition of the tumor microenvironment and its influence on cancer progression and metastasis. It is clear that additional fundamental and preclinical research is required to confirm the efficacy and practicality of this novel and promising strategy for treating cancer.

mTOR co-targeting strategies for head and neck cancer therapy

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy worldwide. There is an urgent need to develop effective therapeutic approaches to prevent and treat HNSCC. Recent deep sequencing of the HNSCC genomic landscape revealed a multiplicity and diversity of genetic alterations in this malignancy. Although a large variety of specific molecules were found altered in each individual tumor, they all participate in only a handful of driver signaling pathways. Among them, the PI3K/mTOR pathway is the most frequently activated, which plays a central role in cancer initiation and progression. In turn, targeting of mTOR may represent a precision therapeutic approach for HNSCC. Indeed, mTOR inhibition exerts potent anti-tumor activity in HNSCC experimental systems, and mTOR targeting clinical trials show encouraging results. However, advanced HNSCC patients may exhibit unpredictable drug resistance, and the analysis of its molecular basis suggests that co-targeting strategies may provide a more effective option. In addition, although counterintuitive, emerging evidence suggests that mTOR inhibition may enhance the anti-tumor immune response. These new findings raise the possibility that the combination of mTOR inhibitors and immune oncology agents may provide novel precision therapeutic options for HNSCC.

Induction of enhanced immunogenic cell death through ultrasound-controlled release of doxorubicin by liposome-microbubble complexes

Immunogenic cell death (ICD) is a specific kind of cell death that stimulates the immune system to combat cancer cells. Ultrasound (US)-controlled targeted release of drugs by liposome-microbubble complexes is a promising approach due to its non-invasive nature and visibility through ultrasound imaging. However, it is not known whether this approach can enhance ICD induced by drugs, such as doxorubicin. Herein, we prepared a doxorubicin-liposome-microbubble complex (MbDox), and the resultant MbDox was then characterized and tested for US-controlled release of Dox (MbDox+US treatment) to enhance the induction of ICD in LL/2 and CT26 cancer cells and in syngeneic murine models. We found that MbDox+US treatment caused more cellular uptake and nuclear accumulation of Dox in tumor cells, and more accumulation of Dox in tumor tissues. Enhanced induction of ICD occurred both in vitro and in vivo. MbDox+US treatment induced more apoptosis, stronger membrane exposure and the release of ER stress proteins and DAMPs in tumor cells, and increased DC maturation in vitro. In addition, MbDox+US treatment also resulted in stronger therapeutic effects in immunocompetent mice than in immunodeficient mice. Moreover, MbDox+US enhancement of ICD was also evidenced by a higher proportion of activated CD8⁺ T-lymphocytes but lower Treg in tumor tissues. Taken together, our results demonstrate that US-controlled release of ICD inducers into nuclei using liposome-microbubble complexes may be an effective approach to enhance the induction of ICD for tumor treatment.

Deregulated Mucosal Immune Surveillance through Gut-Associated Regulatory T Cells and PD-1+ T Cells in Human Colorectal Cancer

Disturbed balance between immune surveillance and tolerance may lead to poor clinical outcomes in some malignancies. In paired analyses of adenocarcinoma and normal mucosa from 142 patients, we found a significant increase of the CD4/CD8 ratio and accumulation of regulatory T cells (Tregs) within the adenocarcinoma. The increased frequency of Tregs correlated with the local infiltration and extension of the tumor. There was concurrent maturation arrest, upregulation of programmed death-1 expression, and functional impairment in CD8⁺ T cells (CTLs) isolated from the adenocarcinoma. Adenocarcinoma-associated Tregs directly inhibit the function of normal human CTLs in vitro. With histopathological analysis, Foxp3⁺ Tregs were preferentially located in stroma. Concurrent transcriptome analysis of epithelial cells, stromal cells, and T cell subsets obtained from carcinomatous and normal intestinal samples from patients revealed a distinct gene expression signature in colorectal adenocarcinoma-associated Tregs, with overexpression of CCR1, CCR8, and TNFRSF9, whereas their ligands CCL4 and TNFSF9 were found upregulated in cancerous epithelium. Overexpression of WNT2 and CADM1, associated with carcinogenesis and metastasis, in cancer-associated stromal cells suggests that both cancer cells and stromal cells play important roles in the development and progression of colorectal cancer through the formation of a tumor microenvironment. The identification of CTL anergy by Tregs and the unique gene expression signature of human Tregs and stromal cells in colorectal cancer patients may facilitate the development of new therapeutics against malignancies.

Factors Influencing the Differentiation of Human Monocytic Myeloid-Derived Suppressor Cells Into Inflammatory Macrophages

Monocytic myeloid-derived suppressor cells (mMDSC) accumulate within tumors where they create an immunosuppressive milieu that inhibits the activity of cytotoxic T and NK cells thereby allowing cancers to evade immune elimination. The toll-like receptors 7/8 agonist R848 induces human mMDSC to mature into inflammatory macrophage (MAC_inflam). This work demonstrates that TNFα, IL-6, and IL-10 produced by maturing mMDSC are critical to the generation of MAC_inflam. Neutralizing any one of these cytokines significantly inhibits R848-dependent mMDSC differentiation. mMDSC cultured in pro-inflammatory cytokine IFNγ or the combination of TNFα plus IL-6 differentiate into MAC_inflam more efficiently than those treated with R848. These mMDSC-derived macrophages exert anti-tumor activity by killing cancer cells. RNA-Seq analysis of the genes expressed when mMDSC differentiate into MAC_inflam indicates that TNFα and the transcription factors NF-κB and STAT4 are major hubs regulating this process. These findings support the clinical evaluation of R848, IFNγ, and/or TNFα plus IL-6 for intratumoral therapy of established cancers.

The Role of Immune and Inflammatory Cells in Idiopathic Pulmonary Fibrosis

The contribution of the immune system to idiopathic pulmonary fibrosis (IPF) remains poorly understood. While most sources agree that IPF does not result from a primary immunopathogenic mechanism, evidence gleaned from animal modeling and human studies suggests that innate and adaptive immune processes can orchestrate existing fibrotic responses. This review will synthesize the available data regarding the complex role of professional immune cells in IPF. The role of innate immune populations such as monocytes, macrophages, myeloid suppressor cells, and innate lymphoid cells will be discussed, as will the activation of these cells via pathogen-associated molecular patterns derived from invading or commensural microbes, and danger-associated molecular patterns derived from injured cells and tissues. The contribution of adaptive immune responses driven by T-helper cells and B cells will be reviewed as well. Each form of immune activation will be discussed in the context of its relationship to environmental and genetic factors, disease outcomes, and potential therapies. We conclude with discussion of unanswered questions and opportunities for future study in this area.

Characterization of Multiple Cytokine Combinations and TGF-β on Differentiation and Functions of Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) regulate T cell immunity, and this population is a new therapeutic target for immune regulation. A previous study showed that transforming growth factor-β (TGF-β) is involved in controlling MDSC differentiation and immunoregulatory function in vivo. However, the direct effect of TGF-β on MDSCs with various cytokines has not previously been tested. Thus, we examined the effect of various cytokine combinations with TGF-β on MDSCs derived from bone marrow cells. The data show that different cytokine combinations affect the differentiation and immunosuppressive functions of MDSCs in different ways. In the presence of TGF-β, interleukin-6 (IL-6) was the most potent enhancer of MDSC function, whereas granulocyte colony-stimulating factors (G-CSF) was the most potent in the absence of TGF-β. In addition, IL-4 maintained MDSCs in an immature state with an increased expression of arginase 1 (Arg1). However, regardless of the cytokine combinations, TGF-β increased expansion of the monocytic MDSC (Mo-MDSC) population, expression of immunosuppressive molecules by MDSCs, and the ability of MDSCs to suppress CD4⁺ T cell proliferation. Thus, although different cytokine combinations affected the MDSCs in different ways, TGF-β directly affects monocytic-MDSCs (Mo-MDSCs) expansion and MDSCs functions.

Sepsis increases perioperative metastases in a murine model

Background

Cancer surgery can promote tumour metastases and worsen prognosis, however, the effect of perioperative complications on metastatic disease remains unclear. In this study we sought to evaluate the effect of common perioperative complications including perioperative blood loss, hypothermia, and sepsis on tumour metastases in a murine model.

Methods

Prior to surgery, pulmonary metastases were established by intravenous challenge of CT26LacZ colon cancer cells in BALB/c mice. Surgical stress was generated through partial hepatectomy (PH) or left nephrectomy (LN). Sepsis was induced by puncturing the cecum to express stool into the abdomen. Hemorrhagic shock was induced by removal of 30% of total blood volume (i.e. stage 3 hemorrhage) via the saphenous vein. Hypothermia was induced by removing the heating apparatus during surgery and lowering core body temperatures to 30 °C. Lung tumour burden was quantified 3 days following surgery.

Results

Surgically stressed mice subjected to stage 3 hemorrhage or hypothermia did not show an additional increase in lung tumour burden. In contrast, surgically stressed mice subjected to intraoperative sepsis demonstrated an additional 2-fold increase in the number of tumour metastases. Furthermore, natural killer (NK) cell function, as assessed by YAC-1 tumour cell lysis, was significantly attenuated in surgically stressed mice subjected to intraoperative sepsis. Both NK cell-mediated cytotoxic function and lung tumour burden were improved with perioperative administration of polyI:C, which is a toll-like receptor (TLR)-3 ligand.

Conclusions

Perioperative sepsis alone, but not hemorrhage or hypothermia, enhances the prometastatic effect of surgery in murine models of cancer. Understanding the cellular mechanisms underlying perioperative immune suppression will facilitate the development of immunomodulation strategies that can attenuate metastatic disease.

Tumor associated macrophages support the growth of FGF9-induced lung adenocarcinoma by multiple mechanisms

OBJECTIVES

Tumor-associated macrophages (TAMs) are known to promote tumorigenesis but the mechanism(s) remain elusive. We have developed a mouse model of lung cancer that is initiated through an inducible overexpression of fibroblast growth factor 9 (FGF9) in type-2 pneumocytes. Expression of FGF9 in adult lungs resulted in a rapid development of multiple adenocarcinoma-like tumor nodules, and is associated with an intense immunological reaction. The purpose of this study is to characterize the immune response to the FGF9-induced lung adenocarcinoma and to determine the contribution of TAMs to growth and survival of these tumors.

MATERIALS AND METHODS

We used flow cytometry, immunostaining, RT-PCR and in vitro culture system on various cell populations isolated from the FGF9-induced adenocarcinoma mouse lungs.

RESULTS

Immunostaining demonstrated that the majority of the inflammatory cells recruited to FGF9-induced lung tumors were macrophages. These TAMs were enriched for the alternatively activated (M2) macrophage subtype. TAMs performed a significantly high immune suppressive function on T-cells and displayed high levels of arginase-1 expression and activity. The growth and colony forming potential of tumor cells was induced by co-culture with TAMs. Additionally, TAMs were shown to promote fibroblast proliferation and angiogenesis. TAMs had high expression of Tgf-β, Vegf, Fgf2, Fgf10, Fgfr2 and several matrix metalloproteinases; factors that play multiple roles in supporting tumor growth, immune protection, fibroblast activation and angiogenesis.

CONCLUSION

Our results provide evidence that the Fgf9-induced lung adenocarcinoma is associated with recruitment and activation of M2-biased TAMs, which provided multiple means of support to the tumor. This model represents an excellent means to further study the complex interactions between TAMs, their related chemokines, and progression of lung adenocarcinoma, and adds further evidence to support the importance of TAMs in tumorigenesis.

Prophylactic DNA vaccine targeting Foxp3+ regulatory T cells depletes myeloid-derived suppressor cells and improves anti-melanoma immune responses in a murine model

Regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSC) are the two important and interactive immunosuppressive components of the tumor microenvironment that hamper anti-tumor immune responses. Therefore, targeting these two populations together might be beneficial for overcoming immune suppression in the tumor microenvironment. We have recently shown that prophylactic Foxp3 DNA/recombinant protein vaccine (Foxp3 vaccine) promotes immunity against Treg in tumor-free conditions. In the present study, we investigated the immune modulatory effects of a prophylactic regimen of the redesigned Foxp3 vaccine in the B16F10 melanoma model. Our results indicate that Foxp3 vaccination continuously reduces Treg population in both the tumor site and the spleen. Surprisingly, Treg reduction was associated with a significant decrease in the frequency of MDSC, both in the spleen and in the tumor environment. Furthermore, Foxp3 vaccination resulted in a significant reduction of arginase-1(Arg-1)-induced nitric oxide synthase (iNOS), reactive oxygen species (ROS) and suppressed MDSC activity. Moreover, this concurrent depletion restored production of inflammatory cytokine IFN-γ and enhanced tumor-specific CTL response, which subsequently resulted in the reduction of tumor growth and the improved survival rate of vaccinated mice. In conclusion, our results revealed that Foxp3 vaccine promotes an immune response against tumor by targeting both Treg and MDSC, which could be exploited as a potential immunotherapy approach.

Targeting tumour microenvironment by tyrosine kinase inhibitor

Tumour microenvironment (TME) is a key determinant of tumour growth and metastasis. TME could be very different for each type and location of tumour and TME may change constantly during tumour growth. Multiple counterparts in surrounding microenvironment including mesenchymal-, hematopoietic-originated cells as well as non-cellular components affect TME. Thus, therapeutics that can disrupt the tumour-favouring microenvironment should be further explored for cancer therapy. Previous efforts in unravelling the dysregulated mechanisms of TME components has identified numerous protein tyrosine kinases, while its corresponding inhibitors have demonstrated potent modulatory effect on TME. Recent works have demonstrated that beyond the direct action on cancer cells, tyrosine kinase inhibitors (TKIs) have been implicated in inactivation or normalization of dysregulated TME components leading to cancer regression. Either through re-sensitizing the tumour cells or reversing the immunological tolerance microenvironment, the emergence of these TME modulatory mechanism of TKIs supports the combinatory use of TKIs with current chemotherapy or immunotherapy for cancer therapy. Therefore, an appropriate understanding on TME modulation by TKIs may offer another mode of action of TKIs for cancer treatment. This review highlights mode of kinase activation or paracrine ligand production from TME components and summarises the findings on the potential use of various TKIs on regulating TME components. At last, the combination use of current TKIs with immunotherapy in the perspectives of efficacy and safety are discussed.

Human neutrophils can mimic myeloid-derived suppressor cells (PMN-MDSC) and suppress microbead or lectin-induced T cell proliferation through artefactual mechanisms

We report that human conventional CD15⁺ neutrophils can be isolated in the peripheral blood mononuclear cell (PBMC) layer during Ficoll gradient separation, and that they can impair T cell proliferation in vitro without concomitant neutrophil activation and killing. This effect was observed in a total of 92 patients with organ transplants, lung cancer or anxiety/depression, and in 18 healthy donors. Although such features are typically associated in the literature with the presence of certain myeloid-derived suppressor cell (PMN-MDSC) populations, we found that commercial centrifuge tubes that contained membranes or gels for PBMC isolation led to up to 70% PBMC contamination by CD15⁺ neutrophils, with subsequent suppressive effects in certain cellular assays. In particular, the suppressive activity of human MDSC should not be evaluated using lectin or microbead stimulation, whereas assays involving soluble or plate-bound antibodies or MLR are unaffected. We conclude that CD15⁺ neutrophil contamination, and associated effects on suppressor assays, can lead to significant artefacts in studies of human PMN-MDSC.

The enhanced antitumor-specific immune response with mannose- and CpG-ODN-coated liposomes delivering TRP2 peptide

PURPOSE

Dendritic cell (DC)-based cancer vaccines is a newly emerging and potent form of immune therapy. As for any new technology, there are still considerable challenges that need to be addressed. Here, we investigate the antitumor potential of a novel liposomal vaccine, M/CpG-ODN-TRP2-Lipo.

METHODS

We developed a vaccination strategy by assembling the DC-targeting mannose and immune adjuvant CpG-ODN on the surface of liposomes, which were loaded with melanoma-specific TRP2_180-188 peptide as liposomal vaccine. M/CpG-ODN-TRP2-Lipo treatment was used to intendedly induce activation of DCs and antitumor- specific immune response in vivo.

RESULTS

Our results demonstrated in vitro that the prepared liposomal particles were efficiently taken up by DCs. This uptake led to an enhanced activation of DCs, as measured by the upregulation of MHC II, CD80, and CD86. Furthermore, M/CpG-ODN-TRP2-Lipo effectively inhibited the growth of implanted B16 melanoma and prolonged the survival of mice. This therapy significantly reduced the number of myeloid-derived suppressor cells (MDSCs) and regulatory T cells, while simultaneously increasing the number of activated T cells, tumor antigen-specific CD8⁺ cytotoxic T cells, and interferon-γ-producing cells. At the same time, it was found to suppress tumor angiogenesis and tumor cell proliferation, as well as up-regulate their apoptosis. Interestingly, MyD88-knockout mice had significantly shorter median survival times compared to wild-type mice following the administration of M/CpG-ODN-TRP2-Lipo.

CONCLUSIONS

The results suggested that the antitumor activities of the vaccine partially rely on the Myd88 signaling pathway. Interestingly, compared to whole tumor cell lysate-based vaccine, M/CpG-ODN-TRP2-Lipo, tumor specific antigen peptide-based vaccine, improved survival of tumor-bearing mice as well as enhanced their antitumor responses. All in all, we describe a novel vaccine formulation, M/CpG-ODN-TRP2-Lipo, with the aim of improving antitumor responses by alleviating the immunosuppressive environment in tumors.

RPN13/ADRM1 inhibitor reverses immunosuppression by myeloid-derived suppressor cells

Myeloid-derived-suppressor cells (MDSCs) are key mediators of immune suppression in the ovarian tumor microenvironment. Modulation of MDSC function to relieve immunosuppression may enhance the immunologic clearance of tumors. The bis-benzylidine piperidone RA190 binds to the ubiquitin receptor RPN13/ADRM1 on the 19S regulatory particle of the proteasome and directly kills ovarian cancer cells by triggering proteotoxic stress. Here we examine the effect of RA190 treatment on the immunosuppression induced by MDSCs in the tumor microenvironment, specifically on the immunosuppression induced by MDSCs. We show that RA190 reduces the expression of Stat3 and the levels of key immunosuppressive enzymes and cytokines arginase, iNOS, and IL-10 in MDSCs, while boosting expression of the immunostimulatory cytokine IL-12. Furthermore, we show that the RA190-treated MDSCs lost their capacity to suppress CD8+ T cell function. Finally, we show that RA190 treatment of mice bearing syngeneic ovarian tumor elicits potent CD8+ T cell antitumor immune responses and improves tumor control and survival. These data suggest the potential of RA190 for ovarian cancer treatment by both direct killing of tumor cells via proteasome inhibition and relief of MDSC-mediated suppression of CD8 T cell-dependent antitumor immunity elicited by the apoptotic tumor cells.

CD33+ HLA-DR- Myeloid-Derived Suppressor Cells Are Increased in Frequency in the Peripheral Blood of Type1 Diabetes Patients with Predominance of CD14+ Subset

INTRODUCTION:

Type 1 Diabetes Mellitus (T1D) is an autoimmune disease that results from the destruction of insulin-producing beta cells of the pancreas by autoreactive T cells. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that can potently suppress T cell responses.

AIM:

To detect the presence of MDSCs in T1D and compare their percentage in T1D versus healthy individuals.

METHOD:

Thirty T1D patients were included in the study. Diabetic patients with nephropathy (n = 18) and diabetic patients without nephropathy (n = 12). A control group of healthy individuals (n = 30) were also included. CD33⁺ and HLA-DR– markers were used to identify MDSCs by flow cytometry. CD14 positive and negative MDSCs subsets were also identified.

RESULTS:

MDSCs was significantly increased in T1D than the control group and diabetic patient with nephropathy compared to diabetic patients without nephropathy. M-MDSCs (CD14⁺ CD33⁺ HLA–DR⁻) were the most abundant MDSCs subpopulation in all groups, however their percentage decrease in T1D than the control group.

CONCLUSION:

MDSCs are increased in the peripheral blood of T1D with a predominance of the CD14⁺ MDSCs subset. Future studies are needed to test the immune suppression function of MDSCs in T1D.

Immuno-oncology-101: overview of major concepts and translational perspectives

Cancer immunotherapy is demonstrating impressive clinical benefit in different malignancies and clinical oncologists are increasingly turning their attention to immune-oncology. It is now well recognized that innate and adaptive immune cells infiltrating tumors are associated with clinical outcomes and responses to treatments, and can be harnessed to patients' benefit. Considerable advances have also been made in understanding how cancers escape from immune attack. Targeting of immunological escape processes regulated by the expression of immune checkpoint receptors and ligands and the down-modulation of tumor antigen presentation is the basis of immuno-oncology treatments. Despite recent achievements, there remain a number of unresolved issues in order to successfully implement cancer immunotherapy in many cancers. Importantly, clinical biomarkers are still needed for better optimization of emerging combination immunotherapies and better treatment tailoring. In this review, we summarize the function of innate and adaptive immune cells in anti-tumor immunity and the general mechanisms exploited by tumor cells to escape and inhibit immune responses as well as therapeutic strategies developed to overcome these mechanisms and discuss emerging biomarkers in immuno-oncology.

Current state and future prospects of immunotherapy for glioma

There is a large unmet need for effective therapeutic approaches for glioma, the most malignant brain tumor. Clinical and preclinical studies have enormously expanded our knowledge about the molecular aspects of this deadly disease and its interaction with the host immune system. In this review we highlight the wide array of immunotherapeutic interventions that are currently being tested in glioma patients. Given the molecular heterogeneity, tumor immunoediting and the profound immunosuppression that characterize glioma, it has become clear that combinatorial approaches targeting multiple pathways tailored to the genetic signature of the tumor will be required in order to achieve optimal therapeutic efficacy.

Radiation and Anti-Cancer Vaccines: A Winning Combination

The emerging combination of radiation therapy with vaccines is a promising new treatment plan in the fight against cancer. While many cancer vaccines such as MUC1, p53 CpG oligodeoxynucleotide, and SOX2 may be great candidates for antitumor vaccination, there still remain many investigations to be done into possible vaccine combinations. One fruitful partnership that has emerged are anti-tumor vaccines in combination with radiation. Radiation therapy was previously thought to be only a tool for directly or indirectly damaging DNA and therefore causing cancer cell death. Now, with much preclinical and clinical data, radiation has taken on the role of an in situ vaccine. With both cancer vaccines and radiation at our disposal, more and more studies are looking to combining vaccine types such as toll-like receptors, viral components, dendritic-cell-based, and subunit vaccines with radiation. While the outcomes of these combinatory efforts are promising, there is still much work to be covered. This review sheds light on the current state of affairs in cancer vaccines and how radiation will bring its story into the future.

Prognostic Roles of mRNA Expression of S100 in Non-Small-Cell Lung Cancer

The S100 protein family is involved in cancer cell invasion and metastasis, but its prognostic value in non-small-cell lung cancer (NSCLC) has not been elucidated. In the present study we investigated the prognostic role of mRNA expression of each individual S100 in NSCLC patients through the Kaplan-Meier plotter (KM plotter) database. Expression of 14 members of the S100 family correlated with overall survival (OS) for all NSCLC patients; 18 members were associated with OS in adenocarcinoma, but none were associated with OS in squamous cell carcinoma. In particular, high mRNA expression level of S100B was associated with better OS in NSCLC patients. The prognostic value of S100 according to smoking status, pathological grades, clinical stages, and chemotherapeutic treatment of NSCLC was further assessed. Although the results should be further verified in clinical trials our findings provide new insights into the prognostic roles of S100 proteins in NSCLC and might promote development of S100-targeted inhibitors for the treatment of NSCLC.

Notch1 signaling in melanoma cells promoted tumor-induced immunosuppression via upregulation of TGF-β1

Background

The receptors of Notch family play an important role in controlling the development, differentiation, and function of multiple cell types. The aim of this study is to investigate the role of Notch1 signaling upon immune suppression induced by melanoma cells.

Methods

Melanoma cell line B16 cells were transfected by lentivirus containing mouse Notch1 gene or Notch1 shRNA to generate B16 cell line that highly or lowly expressed Notch1. Notch1 in anti-tumor immune response was comprehensively appraised in murine B16 melanoma tumor model in immunocompetent and immunodeficient mice. The ratios of CD3⁺CD8⁺ cytotoxic T cells, CD49b⁺NK cells, CD4⁺CD25⁺FoxP3⁺ Tregs and Gr1⁺CD11b⁺ MDSCs in tumor-DLN or spleen were examined by flow cytometry. After the co-culture of B16 cells and CD8⁺ T cells, the effects of Notch1 on the proliferation and activation of T cells were assessed by CCK8 assay, CFSE dilution and Chromium-release test. The mRNA expression and supernatant secretion of immunosuppressive cytokines, TGF-β1, VEGF, IL-10 and IFN-γ were measured by RT-PCR and ELISA, respectively.

Results

Downregulation or overexpression of Notch1 in B16 melanoma cells inhibited or promoted tumor growth in immunocompetent mice, respectively. Notch1 expression in B16 melanoma cells inhibited the infiltration of CD8+ cytotoxic T lymphocytes and NK cells and reduced IFN-γ release in tumor tissue. It could also enhance B16 cell-mediated inhibition of T cell proliferation and activation, and upregulate PD-1 expression on CD4⁺ and CD8⁺ T cells. The percentage of CD4⁺CD25⁺FoxP3⁺ Tregs and Gr1⁺CD11b⁺MDSCs were significantly increased in tumor microenvironment, and all these were attributed to the upregulation of TGF-β1.

Conclusion

These findings suggested that Notch1 signaling in B16 melanoma cells might inhibit antitumor immunity by upregulation of TGF-β1.

Phenotypic and Functional Properties of Tumor-Infiltrating Regulatory T Cells

Regulatory T (Treg) cells maintain immune homeostasis by suppressing excessive immune responses. Treg cells induce tolerance against self- and foreign antigens, thus preventing autoimmunity, allergy, graft rejection, and fetus rejection during pregnancy. However, Treg cells also infiltrate into tumors and inhibit antitumor immune responses, thus inhibiting anticancer therapy. Depleting whole Treg cell populations in the body to enhance anticancer treatments will produce deleterious autoimmune diseases. Therefore, understanding the precise nature of tumor-infiltrating Treg cells is essential for effectively targeting Treg cells in tumors. This review summarizes recent results relating to Treg cells in the tumor microenvironment, with particular emphasis on their accumulation, phenotypic, and functional properties, and targeting to enhance the efficacy of anticancer treatment.

Resistance to anticancer immunity in cancer patients: potential strategies to reverse resistance

In the 1990s, the application of immunotherapy approaches to target cancer cells resulted in significant clinical responses in patients with advanced malignancies who were refractory to conventional therapies. While early immunotherapeutics were focused on T cell-mediated cytotoxic activity, subsequent efforts were centered on targeted antibody-mediated anticancer therapy. The initial success with antibody therapy encouraged further studies and, consequently, there are now more than 25 FDA-approved antibodies directed against a range of targets. Although both T cell and antibody therapies continue to result in significant clinical responses with minimal toxicity, a significant subset of patients does not respond to immunotherapy and another subset develops resistance following an initial response. This review is focused on describing examples showing that cancer resistance to immunotherapies indeed occurs. In addition, it reviews the mechanisms being used to overcome the resistance to immunotherapies by targeting the tumor cell directly and/or the tumor microenvironment.

Molecular Biomarkers of Primary and Acquired Resistance to T-Cell-Mediated Immunotherapy in Cancer: Landscape, Clinical Implications, and Future Directions

The emergence of immunotherapy has revolutionized cancer treatment in recent years. Inhibitors of immune checkpoints, including antibodies against cytotoxic T-lymphocyte-associated protein 4, programmed cell death protein 1, and programmed death ligand 1, have demonstrated notable efficacy in certain advanced cancers. Unfortunately, many patients do not benefit from these therapies and either exhibit primary resistance to treatment or develop acquired mechanisms of resistance after initially responding to therapy. Here, we review the genomic and immune traits that may promote resistance to T-cell-mediated immunotherapy, with a focus on identifying potential biomarkers that could eventually be used in the clinical setting to guide treatment selection. We summarize the clinical evidence for these markers and discuss how current understanding of resistance mechanisms can inform future studies and aid clinical decision-making in order to derive maximum benefit from immunotherapy.

IMPLICATIONS FOR PRACTICE

Immunotherapy has rapidly progressed as a treatment modality for multiple cancers, but it is still unclear which patients are likely to benefit from these therapies. Studies of resistance mechanisms have only recently started to identify biomarkers that can help predict patient outcomes. This review summarizes the available clinical data in regard to immunotherapy resistance, with a focus on molecular biomarkers that may be useful in guiding clinical decision-making. It discusses possible applications of these biomarkers and highlights opportunities for further clinical discovery.

Myeloid-derived suppressor cells accumulate among myeloid cells contributing to tumor growth in matrix metalloproteinase 12 knockout mice

Myeloid-derived suppressor cells (MDSCs) are found frequently in patients and mice bearing tumors, which derived from immature myeloid cells. In healthy individuals, immature myeloid cells formed in the bone marrow differentiating to dendritic cells, macrophages and neutrophils. However, it is unclear whether some gene deficiency will lead to MDSCs accumulation in mice without bearing tumor. Here, we observed that MDSCs accumulated in the bone marrow of matrix metalloproteinase 12 knockout mice (MMP12^-/- mice) compared with wild type mice (MMP12^+/+ mice). And the number of CD4⁺ cells dramatically decreased, regulatory T cells was up-regulation and MDSCs function were determined. The results suggested that immune surveillance have been impaired in MMP12^-/- transgenic mice. After intravenous administration of B16 murine melanoma cells, MMP12^-/- mice developed more metastatic pulmonary nodules than MMP12^+/+ mice. Meanwhile, more MDSCs appeared in the tumors of MMP12^-/- mice compared with those of MMP12^+/+ mice. Mechanistically, we performed a MDSC blocking assay, finding that blockade of MDSCs resulted in reducing growth of tumors in MMP12^-/- mice. Furthermore, we ascertained that macrophages in MMP12^-/- mice abundantly secrete IL-1β in bone marrow which induce the accumulation of MDSCs in the bone marrow. Together, these results demonstrated that the macrophages in MMP12^-/- mice could crosstalk with myeloid cells through IL-1β, inducing MDSCs accumulation, then contributing to tumor growth. It has revealed that the critical roles of macrophage in myeloid cells differentiation.

Carcinogenesis-relevant biological events in the pathophysiology of the efferocytosis phenomenon

The effective removal of cells undergoing programmed cell death, which is referred to as efferocytosis, prevents the leakage of intracellular contents into the surrounding tissue, which could lead to tissue damage and inflammation. Efferocytosis involves a coordinated orchestration of multiple steps that lead to a swift, coherent and immunologically silent removal of dying cells. The release of wound healing cytokines, which resolve inflammation and enhance tissue repair, is an important feature of efferocytosis. However, in addition to the healing cytokines released during efferocytosis, the immunosuppressive action of cytokines promotes the tumor microenvironment, enhances the motility of cancer cells and promotes the evasion of antitumor immunity. The aim of the present review was to comprehensively discuss the efferocytosis phenomenon, the important players associated with this process and their role in cancer-related biological events.

Breast cancer genomics and immuno-oncological markers to guide immune therapies

There is an increasing awareness of the importance of tumor - immune cell interactions to the evolution and therapy responses of breast cancer (BC). Not surprisingly, numerous studies are currently assessing the clinical value of immune modulation for BC patients. However, till now durable clinical responses are only rarely observed. It is important to realize that BC is a heterogeneous disease comprising several histological and molecular subtypes, which cannot be expected to be equally immunogenic and therefore not equally sensitive to single immune therapies. Here we review the characteristics of infiltrating leukocytes in healthy and malignant breast tissue, the prognostic and predictive values of immune cell subsets across different BC subtypes and the various existing immune evasive mechanisms. Furthermore, we describe the presence of certain groups of antigens as putative targets for treatment, evaluate the outcomes of current clinical immunotherapy trials, and finally, we propose a strategy to better implement immuno-oncological markers to guide future immune therapies in BC.

Neutralization of IL-8 decreases tumor PMN-MDSCs and reduces mesenchymalization of claudin-low triple-negative breast cancer

The complex signaling networks of the tumor microenvironment that facilitate tumor growth and progression toward metastatic disease are becoming a focus of potential therapeutic options. The chemokine IL-8 is overexpressed in multiple cancer types, including triple-negative breast cancer (TNBC), where it promotes the acquisition of mesenchymal features, stemness, resistance to therapies, and the recruitment of immune-suppressive cells to the tumor site. The present study explores the utility of a clinical-stage monoclonal antibody that neutralizes IL-8 (HuMax-IL8) as a potential therapeutic option for TNBC. HuMax-IL8 was shown to revert mesenchymalization in claudin-low TNBC models both in vitro and in vivo as well as to significantly decrease the recruitment of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) at the tumor site, an effect substantiated when used in combination with docetaxel. In addition, HuMax-IL8 enhanced the susceptibility of claudin-low breast cancer cells to immune-mediated lysis with NK and antigen-specific T cells in vitro. These results demonstrate the multifaceted way in which neutralizing this single chemokine reverts mesenchymalization, decreases recruitment of MDSCs at the tumor site, assists in immune-mediated killing, and forms the rationale for using HuMax-IL8 in combination with chemotherapy or immune-based therapies for the treatment of TNBC.

Immunological effects of everolimus in patients with metastatic renal cell cancer

The mammalian target of rapamycin (mTOR) is a crucial kinase present in all cells. Besides its role in the regulation of cell-growth, proliferation, angiogenesis, and survival of malignant tumors, mTOR additionally plays an important role in immune regulation by controlling the balance between effector T cells and regulatory T cells (Tregs). This critically affects the suppressive state of the immune system. Here, the systemic immunological effects of everolimus treatment were comprehensively investigated in five patients with metastatic renal cell cancer. In this hypothesis generating study, the immunological alterations in circulating immune subsets induced by everolimus included a (non-significant) increase in the frequency of Tregs, a significant increase in monocytic myeloid-derived suppressor cells, a significant decrease in the frequency of immunoregulatory natural killer cells, classical CD141⁺ (cDC1) and CD1c⁺ (cDC2) dendritic cell subsets, as well as a decrease in the activation status of plasmacytoid dendritic cells and cDC1. These date indicate that the immunological effects of everolimus affect multiple immune cell subsets and altogether tip the balance in favor of immunosuppression, which can be considered a detrimental effect in the treatment of cancer, and may require combination treatment with agents able to negate immune suppression and boost T cell immunity.

CD45RA-Foxp3high regulatory T cells have a negative impact on the clinical outcome of head and neck squamous cell carcinoma

BACKGROUND

Although regulatory T cells (Tregs) are thought to play an important role in immune suppression, their clinical significance in head and neck squamous cell carcinoma (HNSCC) is unclear. A recent study reported Tregs could be divided into functional subsets based on the expression of CD45RA and Foxp3.

METHOD

The frequency of circulating Treg subsets was analyzed in patients with HNSCC and compared with the frequency in patients with benign tumors. The association of Treg subsets with the frequency of lymphocyte subsets, status of progression, clinical course, and prognosis were also examined.

RESULTS

The frequency of CD4+Foxp3+ Tregs was comparable between HNSCC patients and age-matched benign tumor patients; however, CD45RA-Foxp3high Tregs were significantly increased in HNSCC patients, in particular those with advanced stage tumors. The high frequency of CD45RA-Foxp3high Tregs correlated with a poor prognosis and the low frequency of CD45RA-Foxp3high Tregs before treatment showed a better clinical outcome, even in patients with advanced stage tumors. CD45RA-Foxp3high Treg numbers were decreased after intensive treatments; however, Treg numbers recovered in the early stages of recurrent cases, even before the clinical manifestation.

CONCLUSION

CD45RA-Foxp3high Tregs are associated with the clinical course of HNSCC and might be a new target for treatment and an early marker of tumor recurrence in HNSCC patients.

G protein-coupled receptor GPR55 promotes colorectal cancer and has opposing effects to cannabinoid receptor 1

The putative cannabinoid receptor GPR55 has been shown to play a tumor-promoting role in various cancers, and is involved in many physiological and pathological processes of the gastrointestinal (GI) tract. While the cannabinoid receptor 1 (CB₁ ) has been reported to suppress intestinal tumor growth, the role of GPR55 in the development of GI cancers is unclear. We, therefore, aimed at elucidating the role of GPR55 in colorectal cancer (CRC), the third most common cancer worldwide. Using azoxymethane (AOM)- and dextran sulfate sodium (DSS)-driven CRC mouse models, we found that GPR55 plays a tumor-promoting role that involves alterations of leukocyte populations, i.e. myeloid-derived suppressor cells and T lymphocytes, within the tumor tissues. Concomitantly, expression levels of COX-2 and STAT3 were reduced in tumor tissue of GPR55 knockout mice, indicating reduced presence of tumor-promoting factors. By employing the experimental CRC models to CB₁ knockout and CB₁ /GPR55 double knockout mice, we can further show that GPR55 plays an opposing role to CB₁ . We report that GPR55 and CB₁ mRNA expression are differentially regulated in the experimental models and in a cohort of 86 CRC patients. Epigenetic methylation of CNR1 and GPR55 was also differentially regulated in human CRC tissue compared to control samples. Collectively, our data suggest that GPR55 and CB₁ play differential roles in colon carcinogenesis where the former seems to act as oncogene and the latter as tumor suppressor.

Antitumor immunity induced by VE-cadherin modified DC vaccine

Dendritic cells (DCs) are the most potent antigen-presenting cells. A strong interest has been developed in DC vaccines for cancer immunotherapy. Besides, angiogenesis is essential for tumor growth. VE-cadherin has a crucial function in various aspects of vascular biological functions. Here, we produced the full VE-cadherin gene modified DC vaccine (DC-VEC). Its antitumor immunity and chief mechanism driving antitumor effect was evaluated. Analyses were performed including test of antitumor antibody, CTL-mediated cytotoxicity experiment, vascular density, evaluation of the variation of cells and cytokines in immunoregulation. Its damage to the major organs was also evaluated. DC-VEC vaccine resulted in retarded tumor progression and prolonged survival in mice. In DC-VEC group, large amount of immunoglobulin was generated, T cells exhibited greater cytotoxicity against VE-cadherin, and tumor angiogenesis was suppressed. Besides, a decrease of VEGF-A and TGF-β1, and an increase of IL-4 and IFN-γ were observed. CD4⁺ and CD8⁺ T cells were higher, with increased IFN-γ secretion. The percentage of myeloid-derived suppressor cells and regulatory T cells decreased mildly. Also, it had no pathologic changes in major organs. DC-VEC vaccine represents a promising antitumor immunotherapy. The main mechanism is associated with its anti-angiogenesis and immunoregulation response.