Melanoma patients' plasma contains exosomes produced by malignant and normal cells. Plasma exosomes were isolated and separated by immunocapture into two fractions: melanoma cell-derived exosomes ...(MTEX) and normal cell-derived exosomes (non-MTEX). Immunosuppressive effects of MTEX on primary human immune cells were evaluated. Exosomes were isolated from plasma of 12 melanoma patients and six healthy donors (HDs). Expression levels of 19 immunoregulatory proteins in MTEX, non-MTEX and HDs exosomes were evaluated by on-bead flow cytometry. Functional/phenotypic changes induced in CD8
T or natural killer (NK) cells by MTEX or non-MTEX were compared. Plasma protein levels were higher in patients than HDs (P < 0.0009). In patients, MTEX accounted for 23-66% of total exosomes. MTEX were enriched in immunosuppressive proteins (P = 0.03). MTEX, but not HDs exosomes, inhibited CD69 expression (P ≤ 0.0008), induced apoptosis (P ≤ 0.0009) and suppressed proliferation (P ≤ 0.002) in CD8
T cells and downregulated NKG2D expression in NK cells (P = 0.001). Non-MTEX were enriched in immunostimulatory proteins (P = 0.002) and were only weakly immunosuppressive. Elevated MTEX/total exosome ratios and, surprisingly, non-MTEX ability to induce apoptosis of CD8
T cells emerged as positive correlates of disease stage. MTEX emerge as the major mechanism of tumor-induced immune suppression and as an underestimated barrier to successful melanoma immunotherapy.
The recent impressive clinical responses to antibody-based immunotherapy have prompted the identification of clinically relevant tumor antigens that can serve as targets in solid tumors. Among them, ...B7-H3, a member of the B7 ligand family, represents an attractive target for antibody-based immunotherapy, it is overexpressed on differentiated malignant cells and cancer-initiating cells, with limited heterogeneity, and high frequency (60% of 25,000 tumor samples) in many different cancer types, but has a limited expression at low level in normal tissues. In nonmalignant tissues, B7-H3 has a predominantly inhibitory role in adaptive immunity, suppressing T-cell activation and proliferation. In malignant tissues, B7-H3 inhibits tumor antigen-specific immune responses, leading to a protumorigenic effect. B7-H3 also has nonimmunologic protumorigenic functions, such as promoting migration and invasion, angiogenesis, chemoresistance, and endothelial-to-mesenchymal transition, as well as affecting tumor cell metabolism. As a result, B7-H3 expression in tumors is associated with poor prognosis. Although experimental B7-H3 silencing reduces cancer cell malignant potential, there has been limited emphasis on the development of B7-H3-blocking antibodies, most likely because the B7-H3 receptor remains unknown. Instead, many antibody-based strategies utilizing distinct effector mechanisms to target B7-H3-expressing cancer cells have been developed. These strategies have demonstrated potent antitumor activity and acceptable safety profiles in preclinical models. Ongoing clinical trials are assessing their safety and efficacy in patients. Identification of the B7-H3 receptor will improve our understanding of its role in tumor immunity, and will suggest rational strategies to develop blocking antibodies, which may enhance the therapeutic efficacy of tumor immunity.
Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary brain tumor in adults. Current treatment options typically consist of surgery followed by chemotherapy or more ...frequently radiotherapy, however, median patient survival remains at just over 1 year. Therefore, the need for novel curative therapies for GBM is vital. Characterization of GBM cells has contributed to identify several molecules as targets for immunotherapy-based treatments such as EGFR/EGFRvIII, IL13Rα2, B7-H3, and CSPG4. Cytotoxic T lymphocytes collected from a patient can be genetically modified to express a chimeric antigen receptor (CAR) specific for an identified tumor antigen (TA). These CAR T cells can then be re-administered to the patient to identify and eliminate cancer cells. The impressive clinical responses to TA-specific CAR T cell-based therapies in patients with hematological malignancies have generated a lot of interest in the application of this strategy with solid tumors including GBM. Several clinical trials are evaluating TA-specific CAR T cells to treat GBM. Unfortunately, the efficacy of CAR T cells against solid tumors has been limited due to several factors. These include the immunosuppressive tumor microenvironment, inadequate trafficking and infiltration of CAR T cells and their lack of persistence and activity. In particular, GBM has specific limitations to overcome including acquired resistance to therapy, limited diffusion across the blood brain barrier and risks of central nervous system toxicity. Here we review current CAR T cell-based approaches for the treatment of GBM and summarize the mechanisms being explored in pre-clinical, as well as clinical studies to improve their anti-tumor activity.
Immunotherapy of cancer in 2012 Kirkwood, John M.; Butterfield, Lisa H.; Tarhini, Ahmad A. ...
CA: a cancer journal for clinicians,
September/October 2012, Letnik:
62, Številka:
5
Journal Article
Tumor antigen (TA) -targeted monoclonal antibodies (mAb), rituximab, trastuzumab, and cetuximab, are clinically effective for some advanced malignancies, especially in conjunction with chemotherapy ...and/or radiotherapy. However, these results are only seen in a subset (20% to 30%) of patients. We discuss the immunologic mechanism(s) underlying these clinical findings and their potential role in the variability in patients' clinical response.
We reviewed the evidence indicating that the effects of TA-targeted mAb-based immunotherapy are mediated not only by inhibition of signaling pathways, but also by cell-mediated cytotoxicity triggered by the infused TA-targeted mAb. We analyzed the immunologic variables that can influence the outcome of antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro and in animal model systems. We also analyzed the correlation reported between these variables and the clinical response to mAb-based immunotherapy.
Of the variables that influence ADCC mediated by TA-targeted mAb, only polymorphisms of Fcγ receptors (FcγR) expressed by patients' lymphocytes were correlated with clinical efficacy. However, this correlation is not absolute and is not observed in all malignancies. Thus other variables may be responsible for the antitumor effects seen in mAb-treated patients. We discuss the evidence that triggering of TA-specific cellular immunity by TA-targeted mAb, in conjunction with immune escape mechanisms used by tumor cells, may contribute to the differential clinical responses to mAb-based immunotherapy.
Identification of the mechanism(s) underlying the clinical response of patients with cancer treated with TA-targeted mAb is crucial to optimizing their application in the clinic and to selecting the patients most likely to benefit from their use.
The human leukocyte antigen (HLA) class II antigen-processing machinery (APM) presents to cognate CD4
+
T-cells antigenic peptides mainly generated from exogeneous proteins in the endocytic ...compartment. These CD4
+
T cells exert helper function, but may also act as effector cells, thereby recognizing HLA class II antigen-expressing tumor cells. Thus, HLA class II antigen expression by tumor cells influences the tumor antigen (TA)-specific immune responses and, depending on the cancer type, the clinical course of the disease. Many types of human cancers express HLA class II antigens, although with marked differences in their frequency. Some types of cancer lack HLA class II antigen expression, which could be due to structural defects or deregulation affecting different components of the complex HLA class II APM and/or from lack of cytokine(s) in the tumor microenvironment. In this review, we have summarized the information about HLA class II antigen distribution in normal tissues, the structural organization of the HLA class II APM, their expression and regulation in malignant cells, the defects, which have been identified in malignant cells, and their functional and clinical relevance.
Tumour-derived exosomes (TEX) are a subset of extracellular vesicles (EVs) present in body fluids of patients with cancer. The role of this exosome subset in melanoma progression has been of interest ...ever since ex vivo studies of exosomes produced by melanoma cell lines were shown to suppress anti-melanoma immune responses. To study the impact of melanoma-derived exosomes (MTEX) present in patients' plasma on melanoma progression, isolation of MTEX from total plasma exosomes is necessary. We have developed an immunoaffinity-based method for MTEX capture from plasma of melanoma patients. Using mAb 763.74 specific for the CSPG4 epitope uniquely expressed on melanoma cells, we separated MTEX from non-tumour cell-derived exosomes and evaluated the protein cargo of both fractions by quantitative flow cytometry. Melanoma-associated antigens were carried by MTEX but were not detectable in exosomes produced by normal cells. Separation of plasma-derived MTEX from non-MTEX provides an opportunity for future evaluation of MTEX as potential biomarkers of melanoma progression and as surrogates of melanoma in tumour liquid biopsy studies.
Pancreatic ductal adenocarcinoma (PDAC) is usually detected late in the disease process. Clinical workup through imaging and tissue biopsies is often complex and expensive due to a paucity of ...reliable biomarkers. We used an advanced multiplexed plasmonic assay to analyze circulating tumor-derived extracellular vesicles (tEVs) in more than 100 clinical populations. Using EV-based protein marker profiling, we identified a signature of five markers (PDAC
signature) for PDAC detection. In our prospective cohort, the accuracy for the PDAC
signature was 84% 95% confidence interval (CI), 69 to 93% but only 63 to 72% for single-marker screening. One of the best markers, GPC1 alone, had a sensitivity of 82% (CI, 60 to 95%) and a specificity of 52% (CI, 30 to 74%), whereas the PDAC
signature showed a sensitivity of 86% (CI, 65 to 97%) and a specificity of 81% (CI, 58 to 95%). The PDAC
signature of tEVs offered higher sensitivity, specificity, and accuracy than the existing serum marker (CA 19-9) or single-tEV marker analyses. This approach should improve the diagnosis of pancreatic cancer.
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