Modified method for differentiation of myeloid-derived suppressor cells in vitro enhances immunosuppressive ability via glutathione metabolism

Myeloid-derived suppressor cells (MDSCs), which accumulate in tumor bearers, are known to suppress anti-tumor immunity and thus promote tumor progression. MDSCs are considered a major cause of resistance against immune checkpoint inhibitors in patients with cancer. Therefore, MDSCs are potential targets in cancer immunotherapy. In this study, we modified an in vitro method of MDSC differentiation. Upon stimulating bone marrow (BM) cells with granulocyte-macrophage colony-stimulating factor in vitro, we obtained both lymphocyte antigen 6G positive (Ly-6G⁺) and negative (Ly-6G^-) MDSCs (collectively, hereafter referred to as conventional MDSCs), which were non-immunosuppressive and immunosuppressive, respectively. We then found that MDSCs differentiated from Ly-6G^- BM (hereafter called 6G^- BM-MDSC) suppressed T-cell proliferation more strongly than conventional MDSCs, whereas the cells differentiated from Ly-6G⁺ BM (hereafter called 6G⁺ BM-MDSC) were non-immunosuppressive. In line with this, conventional MDSCs or 6G^- BM-MDSC, but not 6G⁺ BM-MDSC, promoted tumor progression in tumor-bearing mice. Moreover, we identified that activated glutathione metabolism was responsible for the enhanced immunosuppressive ability of 6G^- BM-MDSC. Finally, we showed that Ly-6G⁺ cells in 6G^- BM-MDSC, which exhibited weak immunosuppression, expressed higher levels of Cybb mRNA, an immunosuppressive gene of MDSCs, than 6G⁺ BM-MDSC. Together, these data suggest that the depletion of Ly-6G⁺ cells from the BM cells leads to differentiation of immunosuppressive Ly-6G⁺ MDSCs. In summary, we propose a better method for MDSC differentiation in vitro. Moreover, our findings contribute to the understanding of MDSC subpopulations and provide a basis for further research on MDSCs.

Emerging role of natural products in cancer immunotherapy

Cancer immunotherapy has become a new generation of anti-tumor treatment, but its indications still focus on several types of tumors that are sensitive to the immune system. Therefore, effective strategies that can expand its indications and enhance its efficiency become the key element for the further development of cancer immunotherapy. Natural products are reported to have this effect on cancer immunotherapy, including cancer vaccines, immune-check points inhibitors, and adoptive immune-cells therapy. And the mechanism of that is mainly attributed to the remodeling of the tumor-immunosuppressive microenvironment, which is the key factor that assists tumor to avoid the recognition and attack from immune system and cancer immunotherapy. Therefore, this review summarizes and concludes the natural products that reportedly improve cancer immunotherapy and investigates the mechanism. And we found that saponins, polysaccharides, and flavonoids are mainly three categories of natural products, which reflected significant effects combined with cancer immunotherapy through reversing the tumor-immunosuppressive microenvironment. Besides, this review also collected the studies about nano-technology used to improve the disadvantages of natural products. All of these studies showed the great potential of natural products in cancer immunotherapy.

Tubeimoside-1 induces TFEB-dependent lysosomal degradation of PD-L1 and promotes antitumor immunity by targeting mTOR

Programmed cell death ligand 1 (PD-L1)/programmed cell death protein 1 (PD-1) cascade is an effective therapeutic target for immune checkpoint blockade (ICB) therapy. Targeting PD-L1/PD-1 axis by small-molecule drug is an attractive approach to enhance antitumor immunity. Using flow cytometry-based assay, we identify tubeimoside-1 (TBM-1) as a promising antitumor immune modulator that negatively regulates PD-L1 level. TBM-1 disrupts PD-1/PD-L1 interaction and enhances the cytotoxicity of T cells toward cancer cells through decreasing the abundance of PD-L1. Furthermore, TBM-1 exerts its antitumor effect in mice bearing Lewis lung carcinoma (LLC) and B16 melanoma tumor xenograft via activating tumor-infiltrating T-cell immunity. Mechanistically, TBM-1 triggers PD-L1 lysosomal degradation in a TFEB-dependent, autophagy-independent pathway. TBM-1 selectively binds to the mammalian target of rapamycin (mTOR) kinase and suppresses the activation of mTORC1, leading to the nuclear translocation of TFEB and lysosome biogenesis. Moreover, the combination of TBM-1 and anti-CTLA-4 effectively enhances antitumor T-cell immunity and reduces immunosuppressive infiltration of myeloid-derived suppressor cells (MDSCs) and regulatory T (Treg) cells. Our findings reveal a previously unrecognized antitumor mechanism of TBM-1 and represent an alternative ICB therapeutic strategy to enhance the efficacy of cancer immunotherapy.

MicroRNA-regulated transcriptome analysis identifies four major subtypes with prognostic and therapeutic implications in prostate cancer

MicroRNA (miRNA) deregulation plays a critical role in the heterogeneous development of prostate cancer (PCa) by tuning mRNA levels. Herein, we aimed to characterize the molecular features of PCa by clustering the miRNA-regulated transcriptome with non-negative matrix factorization. Using 478 PCa samples from The Cancer Genome Atlas, four molecular subtypes (S-I, S-II, S-III, and S-IV) were identified and validated in two merged microarray and RNAseq datasets with 656 and 252 samples, respectively. Interestingly, the four subtypes showed distinct clinical and biological features after comprehensive analyses of clinical features, multiomic profiles, immune infiltration, and drug sensitivity. S-I is basal/stem/mesenchymal-like and immune-excluded with marked transforming growth factor β, epithelial-mesenchymal transition and hypoxia signals, increased sensitivity to olaparib, and intermediate prognosis. S-II is luminal/metabolism-active and responsive to androgen deprivation therapy with frequent TMPRSS2-ERG fusion and a good prognosis. S-III is characterized by moderate proliferative and metabolic activity, sensitivity to taxane-based chemotherapy, and intermediate prognosis. S-IV is highly proliferative with moderate EMT and stemness, frequent deletions of TP53, PTEN and RB, and the poorest prognosis; it is also immune-inflamed and sensitive to anti-PD-L1 therapy. Overall, based on miRNA-regulated gene profiles, this study identified four distinct PCa subtypes that could improve risk stratification at diagnosis and provide therapeutic guidance.

The biology, function, and applications of exosomes in cancer

Exosomes are cell-derived nanovesicles with diameters from 30 to 150 nm, released upon fusion of multivesicular bodies with the cell surface. They can transport nucleic acids, proteins, and lipids for intercellular communication and activate signaling pathways in target cells. In cancers, exosomes may participate in growth and metastasis of tumors by regulating the immune response, blocking the epithelial-mesenchymal transition, and promoting angiogenesis. They are also involved in the development of resistance to chemotherapeutic drugs. Exosomes in liquid biopsies can be used as non-invasive biomarkers for early detection and diagnosis of cancers. Because of their amphipathic structure, exosomes are natural drug delivery vehicles for cancer therapy.

Hedgehog signaling in gastrointestinal carcinogenesis and the gastrointestinal tumor microenvironment

The Hedgehog (HH) signaling pathway plays important roles in gastrointestinal carcinogenesis and the gastrointestinal tumor microenvironment (TME). Aberrant HH signaling activation may accelerate the growth of gastrointestinal tumors and lead to tumor immune tolerance and drug resistance. The interaction between HH signaling and the TME is intimately involved in these processes, for example, tumor growth, tumor immune tolerance, inflammation, and drug resistance. Evidence indicates that inflammatory factors in the TME, such as interleukin 6 (IL-6) and interferon-γ (IFN-γ), macrophages, and T cell-dependent immune responses, play a vital role in tumor growth by affecting the HH signaling pathway. Moreover, inhibition of proliferating cancer-associated fibroblasts (CAFs) and inflammatory factors can normalize the TME by suppressing HH signaling. Furthermore, aberrant HH signaling activation is favorable to both the proliferation of cancer stem cells (CSCs) and the drug resistance of gastrointestinal tumors. This review discusses the current understanding of the role and mechanism of aberrant HH signaling activation in gastrointestinal carcinogenesis, the gastrointestinal TME, tumor immune tolerance and drug resistance and highlights the underlying therapeutic opportunities.

The application of nanoparticles in cancer immunotherapy: Targeting tumor microenvironment

The tumor development and metastasis are closely related to the structure and function of the tumor microenvironment (TME). Recently, TME modulation strategies have attracted much attention in cancer immunotherapy. Despite the preliminary success of immunotherapeutic agents, their therapeutic effects have been restricted by the limited retention time of drugs in TME. Compared with traditional delivery systems, nanoparticles with unique physical properties and elaborate design can efficiently penetrate TME and specifically deliver to the major components in TME. In this review, we briefly introduce the substitutes of TME including dendritic cells, macrophages, fibroblasts, tumor vasculature, tumor-draining lymph nodes and hypoxic state, then review various nanoparticles targeting these components and their applications in tumor therapy. In addition, nanoparticles could be combined with other therapies, including chemotherapy, radiotherapy, and photodynamic therapy, however, the nanoplatform delivery system may not be effective in all types of tumors due to the heterogeneity of different tumors and individuals. The changes of TME at various stages during tumor development are required to be further elucidated so that more individualized nanoplatforms could be designed.

Berberine diminishes cancer cell PD-L1 expression and facilitates antitumor immunity via inhibiting the deubiquitination activity of CSN5

Programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blocking therapy has become a major pillar of cancer immunotherapy. Compared with antibodies targeting, small-molecule checkpoint inhibitors which have favorable pharmacokinetics are urgently needed. Here we identified berberine (BBR), a proven anti-inflammation drug, as a negative regulator of PD-L1 from a set of traditional Chinese medicine (TCM) chemical monomers. BBR enhanced the sensitivity of tumour cells to co-cultured T-cells by decreasing the level of PD-L1 in cancer cells. In addition, BBR exerted its antitumor effect in Lewis tumor xenograft mice through enhancing tumor-infiltrating T-cell immunity and attenuating the activation of immunosuppressive myeloid-derived suppressor cells (MDSCs) and regulatory T-cells (Tregs). BBR triggered PD-L1 degradation through ubiquitin (Ub)/proteasome-dependent pathway. Remarkably, BBR selectively bound to the glutamic acid 76 of constitutive photomorphogenic-9 signalosome 5 (CSN5) and inhibited PD-1/PD-L1 axis through its deubiquitination activity, resulting in ubiquitination and degradation of PD-L1. Our data reveals a previously unrecognized antitumor mechanism of BBR, suggesting BBR is small-molecule immune checkpoint inhibitor for cancer treatment.

Epigenetic strategies synergize with PD-L1/PD-1 targeted cancer immunotherapies to enhance antitumor responses

Immunotherapy strategies targeting the programmed cell death ligand 1 (PD-L1)/programmed cell death 1 (PD-1) pathway in clinical treatments have achieved remarkable success in treating multiple types of cancer. However, owing to the heterogeneity of tumors and individual immune systems, PD-L1/PD-1 blockade still shows slow response rates in controlling malignancies in many patients. Accumulating evidence has shown that an effective response to anti-PD-L1/anti-PD-1 therapy requires establishing an integrated immune cycle. Damage in any step of the immune cycle is one of the most important causes of immunotherapy failure. Impairments in the immune cycle can be restored by epigenetic modification, including reprogramming the environment of tumor-associated immunity, eliciting an immune response by increasing the presentation of tumor antigens, and by regulating T cell trafficking and reactivation. Thus, a rational combination of PD-L1/PD-1 blockade and epigenetic agents may offer great potential to retrain the immune system and to improve clinical outcomes of checkpoint blockade therapy.

Adding fuel to the fire: immunogenic intensification

The durable long term clinical benefits seen for certain patients treated with immunotherapy agents has suggested there is significant therapeutic potential to be derived from these agents, as shown by the increasing prominence of this treatment strategy in upcoming clinical trials. There has been a renewed interest and focus on the drivers of tumoral antigen recognition, and the pathways by which various cells of the immune system can stimulate, propagate and execute an effective anti-tumor response. Various challenges lie ahead in the further development of these treatments, including induction of an endogenous anti-tumor response, tumor microenvironment modulation, and T-cell response amplification. Novel treatment combinations may prove of significant added benefit by immunogenic intensification.

Dendritic cell defects in the colorectal cancer

Colorectal cancer (CRC) results from the accumulation of both genetic and epigenetic alterations of the genome. However, also the formation of an inflammatory milieu plays a pivotal role in tumor development and progression. Dendritic cells (DCs) play a relevant role in tumor by exerting differential pro-tumorigenic and anti-tumorigenic functions, depending on the local milieu. Quantitative and functional impairments of DCs have been widely observed in several types of cancer, including CRC, representing a tumor-escape mechanism employed by cancer cells to elude host immunosurveillance.

Understanding the interactions between DCs and tumors is important for comprehending the mechanisms of tumor immune surveillance and escape, and provides novel approaches to therapy of cancer. This review summarizes updated information on the role of the DCs in colon cancer development and/or progression.

The tumoral and stromal immune microenvironment in malignant pleural mesothelioma: A comprehensive analysis reveals prognostic immune markers

Antitumor immune responses against solid malignancies correlate with improved patient survival. We conducted a comprehensive investigation of immune responses in tumor and tumor-associated stroma in epithelioid malignant pleural mesothelioma with the goal of characterizing the tumor immune microenvironment and identifying prognostic immune markers. We investigated 8 types of tumor-infiltrating immune cells within the tumor nest and tumor-associated stroma, as well as tumor expression of 5 cytokine/chemokine receptors in 230 patients. According to univariate analyses, high densities of tumoral CD4- and CD20-expressing lymphocytes were associated with better outcomes. High expression of tumor interleukin-7 (IL-7) receptor was associated with worse outcomes. According to multivariate analyses, stage and tumoral CD20 detection were independently associated with survival. Analysis of single immune cell infiltration for CD163+ tumor-associated macrophages did not correlate with survival. However, analysis of immunologically relevant cell combinations identified that: (1) high CD163+ tumor-associated macrophages and low CD8+ lymphocyte infiltration had worse prognosis than other groups and (2) low CD163+ tumor associated macrophages and high CD20+ lymphocyte infiltration had better prognosis than other groups. Multivariate analyses demonstrated that CD163/CD8 and CD163/CD20 were independent prognostic factors of survival. With a recent increase in immunotherapy investigations and clinical trials for malignant pleural mesothelioma patients, our observations that CD20+ B lymphocytes and tumor-associated macrophages are prognostic markers provide important information about the tumor microenvironment of malignant pleural mesothelioma.

Myeloid derived suppressor cells-An overview of combat strategies to increase immunotherapy efficacy

Myeloid-derived suppressor cells (MDSCs) contribute to tumor-mediated immune escape and negatively correlate with overall survival of cancer patients. Nowadays, a variety of methods to target MDSCs are being investigated. Based on the intervention stage of MDSCs, namely development, expansion and activation, function and turnover, these methods can be divided into: (I) prevention or differentiation to mature cells, (II) blockade of MDSC expansion and activation, (III) inhibition of MDSC suppressive activity or (IV) depletion of intratumoral MDSCs. This review describes effective mono- or multimodal-therapies that target MDSCs for the benefit of cancer treatment.

Intratumoral delivery of mRNA: Overcoming obstacles for effective immunotherapy

The immunosuppressive tumor microenvironment (TME) is a major obstacle in cancer immunotherapy. Therefore, it has gained attention as a target site. mRNA emerged as a versatile drug class for cancer therapy. We reported that intratumoral administration of mRNA encoding the fusokine Fβ² supports tumor-specific T-cell immunity. This study provides proof of concept of the use of mRNA to modulate the TME.

Angels and demons: Th17 cells represent a beneficial response, while neutrophil IL-17 is associated with poor prognosis in squamous cervical cancer

The role of interleukin (IL)-17 in cancer remains controversial. In view of the growing interest in the targeting of IL-17, knowing its cellular sources and clinical implications is crucial. In the present study, we unraveled the phenotype of IL-17 expressing cells in cervical cancer using immunohistochemical double and immunofluorescent triple stainings. In the tumor stroma, IL-17 was found to be predominantly expressed by neutrophils (66%), mast cells (23%), and innate lymphoid cells (8%). Remarkably, T-helper 17 (Th17) cells were a minor IL-17 expressing population (4%). A similar distribution was observed in the tumor epithelium. The Th17 and granulocyte fractions were confirmed in head and neck, ovarian, endometrial, prostate, breast, lung, and colon carcinoma. An above median number of total IL-17 expressing cells was an independent prognostic factor for poor disease-specific survival in early stage disease (p = 0.016). While a high number of neutrophils showed at trend toward poor survival, the lowest quartile of mast cells correlated with poor survival (p = 0.011). IL-17 expressing cells and neutrophils were also correlated with the absence of vaso-invasion (p < 0.01). IL-17 was found to increase cell growth or tightness of cervical cancer cell lines, which may be a mechanism for tumorigenesis in early stage disease. These data suggest that IL-17, primarily expressed by neutrophils, predominantly promotes tumor growth, correlated with poor prognosis in early stage disease. Strikingly, a high number of Th17 cells was an independent prognostic factor for improved survival (p = 0.026), suggesting Th17 cells are part of a tumor suppressing immune response.

Lymphocyte activation gene-3 (LAG-3, CD223) in plasmacytoid dendritic cells (pDCs): a molecular target for the restoration of active antitumor immunity

We have recently reported that lymphocyte activation gene-3 (LAG-3,CD223) mediates the alternative, IFNα-deficient activation of plasmacytoid dendritic cells (pDCs) at tumor sites. Our findings define a novel tumor-driven strategy that promotes immunosuppression by pDCs, and we have provided more detailed information regarding the immunomodulatory role of of LAG-3. The translational relevance of our results for the treatment of tumors and autoimmune diseases is discussed herein.

Location, location, location: functional and phenotypic heterogeneity between tumor-infiltrating and non-infiltrating myeloid-derived suppressor cells

An increasing number of studies is focusing on the role of myeloid-derived suppressor cells (MDSCs) in the suppression of antitumor immune responses. Although the main site of action for MDSCs is most likely the tumor microenvironment, the study of these cells has been largely restricted to MDSCs derived from peripheral lymphoid organs. Only in a minority of studies MDSCs isolated from the tumor microenvironment have been characterized. This review will give an overview of the data available on the phenotypical and functional differences between tumor-derived MDSCs and MDSCs isolated from the spleen of tumor-bearing mice or from the peripheral blood of cancer patients.

Core needle biopsy of breast cancer tumors increases distant metastases in a mouse model

INTRODUCTION: Incisional biopsies, including the diagnostic core needle biopsy (CNB), routinely performed before surgical excision of breast cancer tumors are hypothesized to increase the risk of metastatic disease. In this study, we experimentally determined whether CNB of breast cancer tumors results in increased distant metastases and examine important resultant changes in the primary tumor and tumor microenvironment associated with this outcome. METHOD: To evaluate the effect of CNB on metastasis development, we implanted murine mammary 4T1 tumor cells in BALB/c mice and performed CNB on palpable tumors in half the mice. Subsequently, emulating the human scenario, all mice underwent complete tumor excision and were allowed to recover, with attendant metastasis development. Tumor growth, lung metastasis, circulating tumor cell (CTC) levels, variation in gene expression, composition of the tumor microenvironment, and changes in immunologic markers were compared in biopsied and non-biopsied mice. RESULTS: Mice with biopsied tumors developed significantly more lung metastases compared to non-biopsied mice. Tumors from biopsied mice contained a higher frequency of myeloid-derived suppressor cells (MDSCs) accompanied by reduced CD4 + T cells, CD8 + T cells, and macrophages, suggesting biopsy-mediated development of an increasingly immunosuppressive tumor microenvironment. We also observed a CNB-dependent up-regulation in the expression of SOX4, Ezh2, and other key epithelial-mesenchymal transition (EMT) genes, as well as increased CTC levels among the biopsy group. CONCLUSION: CNB creates an immunosuppressive tumor microenvironment, increases EMT, and facilitates release of CTCs, all of which likely contribute to the observed increase in development of distant metastases.