Experimental production of clinical-grade dendritic cell vaccine for acute myeloid leukemia.

Dendritic cells (DC) are professional antigen presenting cells of the immune system. Through the use of DC vaccines (DC after exposure to tumour antigens), cryopreserved in single-use aliquots, an attractive and novel immunotherapeutic strategy is available as an option for treatment. In this paper we describe an in vitro attempt to scale-up production of clinical-grade DC vaccines from leukemic cells. Blast cells of two relapsed AML patients were harvested for DC generation in serum-free culture medium containing clinical-grade cytokines GM-CSF, IL-4 and TNF-alpha. Cells from patient 1 were cultured in a bag and those from patient 2 were cultured in a flask. The numbers of seeding cells were 2.24 x 10(8) and 0.8 x 10(8), respectively. DC yields were 10 x 10(6) and 29.8 x 10(6) cells, giving a conversion rate of 4.7% and 37%, respectively. These DC vaccines were then cryopreserved in approximately one million cells per vial with 20% fresh frozen group AB plasma and 10% DMSO. At 12 months and 21 months post cryopreservation, these DC vaccines were thawed, and their sterility, viability, phenotype and functionality were studied. DC vaccines remained sterile up to 21 months of storage. Viability of the cryopreserved DC in the culture bag and flask was found to be 50% and 70% at 12 months post cryopreservation respectively; and 48% and 67% at 21 months post cryopreservation respectively. These DC vaccines exhibited mature DC surface phenotypic markers of CD83, CD86 and HLA-DR, and negative for haemopoietic markers. Mixed lymphocyte reaction (MLR) study showed functional DC vaccines. These experiments demonstrated that it is possible to produce clinical-grade DC vaccines in vitro from blast cells of leukemic patients, which could be cryopreserved up to 21 months for use if repeated vaccinations are required in the course of therapy.

Defective STAT1 activation associated with impaired IFN-γ production in NK and T lymphocytes from metastatic melanoma patients treated with IL-2.

High dose (HD) IL-2 therapy has been used for almost two decades as an immunotherapy for metastatic melanoma. IL-2 promotes the proliferation and effector function of T and NK cells through the tyrosine phosphorylation and activation of signal transducer and activator of transcription factors (STAT), especially STAT5. However, whether any defects in STAT activation exist in T and NK lymphocytes from melanoma patients are under debate. Here, we measured the extent of HD IL-2-induced phosphorylation of STAT5 and STAT1 in lymphocyte subsets from metastatic melanoma patients and healthy controls at a single cell level using flow cytometry. We found no defects in IL-2-induced STAT5 phosphorylation and induction of proliferation in T and NK cell subsets in vitro. This was confirmed by measuring ex vivo STAT5 activation in whole blood collected from patients during their first bolus HD IL-2 infusion. IL-2 also induced STAT1 phosphorylation via IFN-γ receptors in T and NK cell subsets through the release of IFN-γ by CD56hi and CD56lo NK cells. Further analysis revealed that melanoma patients had a sub-optimal STAT1 activation response linked to lower IL-2-induced IFN-γ secretion in both CD56hi and CD56low NK cell subsets. STAT1 activation in response to IL-2 also showed an age-related decline in melanoma patients not linked to tumor burden indicating a premature loss of NK cell function. Taken together, these findings indicate that, although STAT5 activation is normal in metastatic melanoma patients in response to IL-2, indirect STAT1 activation is defective owing to deficiencies in the NK cell response to IL-2.

IL2 Variant Circumvents ICOS+ Regulatory T-cell Expansion and Promotes NK Cell Activation.

Clinical responses to high-dose IL2 therapy are limited due to selective expansion of CD4+CD25+Foxp3+ T-regulatory cells (Treg), especially ICOS+ Tregs, rather than natural killer (NK) cells and effector T cells. These ICOS+ Tregs are highly suppressive and constitutively express high levels of IL2Rα (CD25) and CD39. Here, we characterized the effect of a mutant form of IL2 (F42K), which preferentially binds to the lower affinity IL2Rßγ with reduced binding to CD25, on Tregs, effector NK cells, and T-cell subsets. Unlike wild-type (WT) IL2, F42K did not efficiently induce the expansion of highly suppressive ICOS+ Tregs in peripheral blood mononuclear cells (PBMC) from healthy controls and melanoma patients. Instead, it promoted the expansion of CD16+CD56+ NK cells and CD56hiCD16- NK cell subsets in both short- and long-term cultures, with enhanced Bcl-2 expression. Stimulation of PBMCs with F42K induced expression of more NK cell activation molecules, such as NKp30, NKp44, DNAM-1, NKG2D, 4-1BB/CD137, and Tim-3, than WT IL2. F42K induced greater upregulation of TRAIL, and NK-mediated cytolytic activity was increased against both autologous and HLA-mismatched melanoma cells compared with WT IL2. Gene expression analysis revealed distinct gene expression profiles stimulated by F42K, WT IL2, and IL15. F42K therapy in vivo also induced a dramatic reduction in the expansion of ICOS+ Tregs, promoted NK cell expansion, and inhibited melanoma tumor growth more efficiently than WT IL2 and more effectively than anti-CTLA-4. Our findings suggest that F42K could be a potential substitute for WT IL2 as a cytokine therapy for cancer. Cancer Immunol Res; 4(11); 983-94. ©2016 AACR.

Multicystic dedifferentiated retroperitoneal liposarcoma: tumour cyst fluid analysis and implications for management.

Liposarcomas are soft tissue sarcomas of adipocyte origin. We describe a case of a dedifferentiated retroperitoneal liposarcoma with an unusual presentation on recurrence as a large, multicystic tumour. The patient was a 72-year-old woman who had undergone multiple treatments including two prior resections. For her most recent locoregional disease recurrence, the patient was offered surgical debulking for symptom palliation. At this operation, performed after two cycles of chemotherapy, the tumour cyst fluid was analysed and found to have a predominance of immune cells with no identifiable malignant cells. This case and the results of our tumour cyst fluid analysis raise several interesting considerations for the management of this unique situation in a rare disease.

Analysis of the intratumoral adaptive immune response in well differentiated and dedifferentiated retroperitoneal liposarcoma.

Treatment options are limited in well differentiated (WD) and dedifferentiated (DD) retroperitoneal liposarcoma. We sought to study the intratumoral adaptive immune response and explore the potential feasibility of immunotherapy in this disease. Tumor-infiltrating lymphocytes (TILs) were isolated from fresh surgical specimens and analyzed by flow cytometry for surface marker expression. Previously reported immune cell aggregates known as tertiary lymphoid structures (TLS) were further characterized by immunohistochemistry. In all fresh tumors, TILs were found. The majority of TILs were CD4 T cells; however cytotoxic CD8 T cells were also seen (average: 20% of CD3 T cells). Among CD8 T cells, 65% expressed the immune checkpoint molecule PD-1. Intratumoral TLS may be sites of antigen presentation as DC-LAMP positive, mature dendritic cells were found juxtaposed next to CD4 T cells. Clinicopathologic correlation, however, demonstrated that presence of TLS was associated with worse recurrence-free survival in WD disease and worse overall survival in DD disease. Our data suggest that an adaptive immune response is present in WD/DD retroperitoneal liposarcoma but may be hindered by TLS, among other possible microenvironmental factors; further investigation is needed. Immunotherapy, including immune checkpoint blockade, should be evaluated as a treatment option in this disease.

The IL-2 cytokine family in cancer immunotherapy.

The use of cytokines from the IL-2 family (also called the common γ chain cytokine family) such as interleukin (IL)-2, IL-7, IL-15, and IL-21 to activate the immune system of cancer patients is one of the most important areas of current cancer immunotherapy research. The infusion of IL-2 at low or high doses for multiple cycles in patients with metastatic melanoma and renal cell carcinoma was the first successful immunotherapy for cancer proving that the immune system could completely eradicate tumor cells under certain conditions. The initial clinical success observed in some IL-2-treated patients encouraged further efforts focused on developing and improving the application of other IL-2 family cytokines (IL-4, IL-7, IL-9, IL-15, and IL-21) that have unique biological effects playing important roles in the development, proliferation, and function of specific subsets of lymphocytes at different stages of differentiation with some overlapping effects with IL-2. IL-7, IL-15, and IL-21, as well as mutant forms or variants of IL-2, are now also being actively pursued in the clinic with some measured early successes. In this review, we summarize the current knowledge on the biology of the IL-2 cytokine family focusing on IL-2, IL-15 and IL-21. We discuss the similarities and differences between the signaling pathways mediated by these cytokines and their immunomodulatory effects on different subsets of immune cells. Current clinical application of IL-2, IL-15 and IL-21 either as single agents or in combination with other biological agents and the limitation and potential drawbacks of these cytokines for cancer immunotherapy are also described. Lastly, we discuss the future direction of research on these cytokines, such as the development of new cytokine mutants and variants for improving cytokine-based immunotherapy through differential binding to specific receptor subunits.

Tumor-infiltrating lymphocyte therapy for melanoma: rationale and issues for further clinical development.

Cancer immunotherapy has become an important area for the future development of cancer therapy; this includes T-cell-based therapies that involve adoptive transfer of autologous T cells derived from the tumors or peripheral blood of cancer patients, vaccines, oncolytic virus therapy, and immunomodulatory antibodies and ligands. Here, we summarize the current approaches and clinical data in the field of adoptive T-cell transfer therapy using tumor-infiltrating lymphocytes (TILs) for metastatic melanoma. We also discuss current knowledge on the mechanism of transferred TILs in mediating tumor regression and the growing need for and recent advances in the identification of predictive biomarkers to better select patients for TIL therapy. The current technical limitations of current TIL expansion methods for out-scaling are discussed as well as how these are being addressed in order to further "industrialize" this form of cell therapy. Lastly, how TIL adoptive transfer can be incorporated into the current melanoma treatment continuum, especially as combination therapy with other immunomodulators and targeted drugs, is discussed.

IL-2 therapy promotes suppressive ICOS+ Treg expansion in melanoma patients.

High-dose (HD) IL-2 therapy in patients with cancer increases the general population of Tregs, which are positive for CD4, CD25, and the Treg-specific marker Foxp3. It is unknown whether specific subsets of Tregs are activated and expanded during HD IL-2 therapy or whether activation of any particular Treg subset correlates with clinical outcome. Here, we evaluated Treg population subsets that were induced in patients with melanoma following HD IL-2 therapy. We identified a Treg population that was positive for CD4, CD25, Foxp3, and the inducible T cell costimulator (ICOS). This Treg population increased more than any other lymphocyte subset during HD IL-2 therapy and had an activated Treg phenotype, as indicated by high levels of CD39, CD73, and TGF-ß. ICOS(+) Tregs were the most proliferative lymphocyte population in the blood after IL-2 therapy. Patients with melanoma with enhanced expansion of ICOS(+) Tregs in blood following the first cycle of HD IL-2 therapy had worse clinical outcomes than patients with fewer ICOS(+) Tregs. However, there was no difference in total Treg expansion between HD IL-2 responders and nonresponders. These data suggest that increased expansion of the ICOS(+) Treg population following the first cycle of HD IL-2 therapy may be predictive of clinical outcome.

Comparing the ability of freshly generated and cryopreserved dendritic cell vaccines to inhibit growth of breast cancer in a mouse model.

Repetitive vaccinations with dendritic cell (DC)-based vaccines over long periods of time can break pre-existing tolerance to tumors and achieve clinically relevant immune response. This requires a large number of DCs to be generated under good manufacturing protocol, which is time- and cost intensive. Thus, producing a large numbers of DCs at one time point and cryopreserving these cells in ready-for-use aliquots for clinical application may overcome this constraint. This could also reduce batch-to-batch variations. In this study, we generated DCs from bone marrow obtained from BALB/c mice. Some of the generated DCs were cryopreserved before conducting various tests. There were no significant differences in the morphology and phenotype between cryopreserved and freshly generated DCs. Both types of DCs pulsed with tumor lysate (TL) from 4T1 murine mammary cancer cells (DC+TL) possessed a similar capacity to stimulate the proliferation of T-cells. In addition, cryopreserved and fresh DC pulsed with TL showed similar tumor growth inhibition patterns. Both DCs induced initial retardation of tumor growth (p<0.05) and prolonged the survival (p<0.05) of tumor-bearing mice treated with DC+TL as compared with nontreated control mice. Cryopreserved DCs shared similar therapeutic efficacy to fresh DCs, and this finding lends supports the routine use of cryopreserved DCs in future clinical trials.

Differential clinical significance of individual NKG2D ligands in melanoma: soluble ULBP2 as an indicator of poor prognosis superior to S100B.

PURPOSE: Cytotoxic lymphocytes interact with human tumor cells via the activating immunoreceptor NKG2D, recognizing a variety of stress-associated MIC and ULBP surface molecules. However, tumors can escape from this immunosurveillance by shedding NKG2D ligands (NKG2DL), rendering the soluble products detectable in patients' sera. EXPERIMENTAL DESIGN: To elucidate the clinical significance of NKG2DL diversity, we studied their expression on melanoma tissues and their presence as soluble molecules in sera from >200 melanoma patients and compared the latter with the well-established serum marker S100B. RESULTS: Immunohistochemistry revealed a heterogeneous expression of MIC and ULBP2 molecules between and within melanoma metastases. Compared with MIC, ULBP2 was less frequently expressed. Accordingly, elevated levels of soluble ULBP2 (sULBP2) were detected in sera of melanoma patients less frequently than elevated levels of soluble MICA (sMICA), although both soluble NKG2DL (sNKG2DL) were significantly increased compared with sera of healthy controls (P < 0.0001). Strikingly, elevated concentrations of sULBP2, but not of sMICA, were strongly associated with disease progression (P < 0.0001) and tumor load (P = 0.0003). Elevated serum levels of either sNKG2DL correlated with reduced overall survival, albeit considerably stronger for sULBP2 (P < 0.0001) than for sMICA (P = 0.011). In early-stage (I-III) melanoma patients, only sULBP2 (P < 0.0001) but neither sMICA nor S100B revealed prognostic significance. Multivariate analysis identified sULBP2 (P = 0.0015) and S100B (P = 0.013) but not sMICA as independent predictors of prognosis. CONCLUSION: Our data reveal marked differences in the clinical significance of individual sNKG2DL. Only sULBP2 is an independent predictor of prognosis, the significance of which is superior to the well-established and widely used melanoma serum marker S100B.