Sharon Merims

MHC Class I-Independent Recognition of NK-Activating Receptor KIR2DS4

Natural killer cells are capable of killing tumor and virus-infected cells. This killing is mediated primarily via the natural cytotoxicity receptors, including NKp46, NKp44, NKp30, and by the NKG2D receptor. Killer cell Ig-like receptors (KIRs) are mainly involved in inhibiting NK killing (inhibitory KIRs) via interaction with MHC class I molecules. Some KIRs, however, have been found to enhance NK killing when interacting with MHC class I molecules (activating KIRs). We have previously demonstrated that KIR2DS4, an activating KIR, recognizes the HLA-Cw4 protein. The interaction observed was weak and highly restricted to HLA-Cw4 only. These findings prompted us to check whether KIR2DS4 might have additional ligand(s). In this study, we show that KIR2DS4 is able to also interact with a non-class I MHC protein expressed on melanoma cell lines and on a primary melanoma. This interaction is shown to be both specific and functional. Importantly, site-directed mutagenesis analysis reveals that the amino acid residues involved in the recognition of this novel ligand are different from those interacting with HLA-Cw4. These results may shed new light on the function of activating KIRs and their relevance in NK biology.

Imprinting of Lymphocytes with Melanoma Antigens Acquired by Trogocytosis Facilitates Identification of Tumor-Reactive T Cells

Trogocytosis is a contact-dependent intercellular transfer of membrane fragments and associated molecules from APCs to effector lymphocytes. We previously demonstrated that trogocytosis also occurs between tumor target and cognate melanoma Ag-specific cytotoxic T cells (CTL). In this study, we show that, following trogocytosis, immune effector cells acquire molecular components of the tumor, including surface Ags, which are detectable by specific mAbs. We demonstrate that CD8+ and CD4+ T cells from melanoma patients’ PBMC and tumor-infiltrating lymphocytes (TIL) capture melanoma Ags, enabling identification of trogocytosing lymphocytes by staining with Ag-specific Abs. This finding circumvents the necessity of tumor prelabeling, which in the past was mandatory to detect membrane-capturing T cells. Through the detection of melanoma Ags on TIL, we sorted trogocytosing T cells and verified their preferential reactivity and cytotoxicity. Furthermore, tumor Ag–imprinted T cells were detected at low frequency in fresh TIL cultures shortly after extraction from the tumor. Thus, T cell imprinting by tumor Ags may allow the enrichment of melanoma Ag-specific T cells for research and potentially even for the adoptive immunotherapy of patients with cancer.

Trogocytosis Is a Gateway to Characterize Functional Diversity in Melanoma-Specific CD8 + T Cell Clones

Trogocytosis, the transfer of membrane patches from target to immune effector cells, is a signature of tumor–T cell interaction. In this study, we used the trogocytosis phenomenon to study functional diversity within tumor-specific T cell clones with identical TCR specificity. MART-126–35–specific CD8 T cell clones, which differed in their trogocytosis capacity (low [2D11], intermediate [2G1], high [2E2]), were generated from melanoma patients. Functional evaluation of the clones showed that the percentage of trogocytosis-capable T cells closely paralleled each clone’s IFN-γ and TNF-α production, lysosome degranulation, and lysis of peptide-pulsed targets and unmodified melanoma. The highly cytotoxic 2E2 clone displayed the highest TCR peptide binding affinity, whereas the low-activity 2D11 clone showed TCR binding to peptide-MHC in a CD8-dependent manner. TCR analysis revealed Vβ16 for clones 2E2 and 2G1 and Vβ14 for 2D11. When peptide-affinity differences were bypassed by nonspecific TCR stimulation, clones 2E2 and 2D11 still manifested distinctive signaling patterns. The high-activity 2E2 clone displayed prolonged phosphorylation of ribosomal protein S6, an integrator of MAPK and AKT activation, whereas the low-activity 2D11 clone generated shorter and weaker phosphorylation. Screening the two clones with identical TCR Vβ by immunoreceptor array showed higher phosphorylation of NK, T, and B cell Ag (NTB-A), a SLAM family homophilic receptor, in clone 2E2 compared with 2G1. Specific blocking of NTB-A on APCs markedly reduced cytokine production by CD8 lymphocytes, pointing to a possible contribution of NTB-A costimulation to T cell functional diversity. This finding identifies NTB-A as a potential target for improving anti-cancer immunotherapy.

Adjuvant Autologous Melanoma Vaccine for Macroscopic Stage III Disease: Survival, Biomarkers, and Improved Response to CTLA-4 Blockade

Background. There is not yet an agreed adjuvant treatment for melanoma patients with American Joint Committee on Cancer stages III B and C. We report administration of an autologous melanoma vaccine to prevent disease recurrence. Patients and Methods. 126 patients received eight doses of irradiated autologous melanoma cells conjugated to dinitrophenyl and mixed with BCG. Delayed type hypersensitivity (DTH) response to unmodified melanoma cells was determined on the vaccine days 5 and 8. Gene expression analysis was performed on 35 tumors from patients with good or poor survival. Results. Median overall survival was 88 months with a 5-year survival of 54%. Patients attaining a strong DTH response had a significantly better (p = 0.0001) 5-year overall survival of 75% compared with 44% in patients without a strong response. Gene expression array linked a 50-gene signature to prognosis, including a cluster of four cancer testis antigens: CTAG2 (NY-ESO-2), MAGEA1, SSX1, and SSX4. Thirty-five patients, who received an autologous vaccine, followed by ipilimumab for progressive disease, had a significantly improved 3-year survival of 46% compared with 19% in nonvaccinated patients treated with ipilimumab alone (p = 0.007). Conclusion. Improved survival in patients attaining a strong DTH and increased response rate with subsequent ipilimumab suggests that the autologous vaccine confers protective immunity.

Human T cell crosstalk is induced by tumor membrane transfer.

Trogocytosis is a contact-dependent unidirectional transfer of membrane fragments between immune effector cells and their targets, initially detected in T cells following interaction with professional antigen presenting cells (APC). Previously, we have demonstrated that trogocytosis also takes place between melanoma-specific cytotoxic T lymphocytes (CTLs) and their cognate tumors. In the present study, we took this finding a step further, focusing on the ability of melanoma membrane-imprinted CD8+ T cells to act as APCs (CD8+T-APCs). We demonstrate that, following trogocytosis, CD8+T-APCs directly present a variety of melanoma derived peptides to fraternal T cells with the same TCR specificity or to T cells with different TCRs. The resulting T cell-T cell immune synapse leads to (1) Activation of effector CTLs, as determined by proliferation, cytokine secretion and degranulation; (2) Fratricide (killing) of CD8+T-APCs by the activated CTLs. Thus, trogocytosis enables cross-reactivity among CD8+ T cells with interchanging roles of effectors and APCs. This dual function of tumor-reactive CTLs may hint at their ability to amplify or restrict reactivity against the tumor and participate in modulation of the anti-cancer immune response.

Adoptive cell therapy: past, present and future

The immune system is a potent inhibitor of tumor growth with curative potential, constituting in many eyes the future of antineoplastic therapy. Adoptive cell therapy (ACT) is a form of immunotherapy in which autologous cancer-cognate lymphocytes are expanded and modified ex vivo and re-infused to combat the tumor. This review follows the evolvement of ACT and treatment protocols, focusing on unresolved dilemmas regarding this treatment while providing evidence for its effectiveness in refractory patients. Future directions of ACT are discussed, in particular with regard to genetic engineering of autologous cells, and the role of ACT in the era of checkpoint inhibitors is addressed.

Immune Monitoring of Patients Treated With a Whole-Cell Melanoma Vaccine Engineered to Express 4-1BBL.

CD8 lymphocytes are mandatory mediators of tumor regression. To enhance their specific antitumor activity, we aimed to improve a melanoma cell-based vaccine by transfecting it with 4-1BB ligand, a costimulatory and immune modulatory molecule. Thirty-four American Joint Committee on Cancer (AJCC) stage IIB–IV patients were vaccinated with a melanoma antigen-rich cell line engineered to express HLA-A2 and 4-1BBL (M20/A2/BBL). Twelve serially recruited patients were monitored for interferon &ggr; expression and CD107a mobilization before and after vaccination. Thirty-three patients remained alive, with an estimated mean overall survival of 26.2 months. No grade 3–4 adverse events were encountered. Immune monitoring detected an increase in circulating antimelanoma CD8 T cells in 9 of 12 patients, which were significantly stimulated by the parental melanoma, reflecting a relevant antitumor response. The results from this study show that the costimulatory 4-1BB ligand fortifies an antigen-rich melanoma cell line with enhanced antigen-specific stimulation of CD8 T cells. The use of a costimulatory molecule as part of a vaccine confers a selective increase of T-cell subsets with antimelanoma reactivity, which in some cases were characterized for their epitope specificity.

Exploring the potential of mucin 13 (MUC13) as a biomarker for carcinomas and other diseases

Abstract Background: Mucin 13 (MUC13) is a cell surface glycoprotein aberrantly expressed in a variety of epithelial carcinomas. Thus far, the role of MUC13 in various diseases remains elusive. To the best of our knowledge, this is the first study to examine the potential of MUC13 as a serum biomarker in a variety of carcinomas and other conditions. Methods: We developed a recombinant MUC13 protein, mouse monoclonal antibodies and enzyme immunoassay (ELISA) for MUC13. We used this assay to measure MUC13 levels in the supernatants of cancer cell lines and a large cohort of serum samples from healthy and diseased individuals. Results: MUC13 is secreted from cancer cell lines, with highest levels found in ovarian cancer cell lines. MUC13 levels in human sera were significantly increased in patients with renal failure and 20%–30% of patients with ovarian, liver, lung and other cancers. MUC13 was also elevated in 70% of patients with active cutaneous melanoma, but not uveal melanoma. Furthermore, we identified significant MUC13 elevations in the serum of patients with vasculitis (ANCA-positive) autoantibodies, but not in those with inflammatory bowel disease. Conclusions: Serum MUC13 is frequently elevated not only in a variety of malignant cases but also in some benign pathologies, thus appearing to be a non-specific disease biomarker. Nonetheless, serum MUC13 is clearly highly elevated in some carcinoma patients, and its relationship with tumor progression in this context warrant further research. Future studies that examine the correlation between serum MUC13 levels to stage of cancer could elucidate prognostic potential.