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Sialic acids cap the glycans of cell surface glycoproteins and glycolipids. They are involved in a multitude of biological processes, and aberrant sialic acid expression is associated with several pathologies, such as cancer. Strategies to interfere with the sialic acid biosynthesis can potentially be used for anticancer therapy. One well-known class of sialylation inhibitors is peracetylated 3-fluorosialic acids. We synthesized 3-fluorosialic acid derivatives modified at the C-4, C-5, C-8, and C-9 position and tested their inhibitory potency in vitro. Modifications at C-5 lead to increased inhibition, compared to the natural acetamide at this position. These structure-activity relationships could also be applied to improve the efficiency of sialic acid metabolic labeling reagents by modification of the C-5 position. Hence, these results improve our understanding of the structure-activity relationships of sialic acid glycomimetics and their metabolic processing.

Cytotoxic T lymphocytes (CTL) are antigen-specific effector cells with the ability to eradicate cancer cells in a contact-dependent manner. Metabolic perturbation compromises the CTL effector response in tumor subregions, resulting in failed cancer cell elimination despite the infiltration of tumor-specific CTLs. Restoring the functionality of these tumor-infiltrating CTLs is key to improve immunotherapy. Extracellular adenosine is an immunosuppressive metabolite produced within the tumor microenvironment. Here, by applying single-cell reporter strategies in 3D collagen cocultures in vitro and progressing tumors in vivo, we show that adenosine weakens one-to-one pairing of activated effector CTLs with target cells, thereby dampening serial cytotoxic hit delivery and cumulative death induction. Adenosine also severely compromised CTL effector restimulation and expansion. Antagonization of adenosine A2a receptor (ADORA2a) signaling stabilized and prolonged CTL–target cell conjugation and accelerated lethal hit delivery by both individual contacts and CTL swarms. Because adenosine signaling is a near-constitutive confounding parameter in metabolically perturbed tumors, ADORA2a targeting represents an orthogonal adjuvant strategy to enhance immunotherapy efficacy.

Supplementary Figure from Adenosine A2a Receptor Antagonism Restores Additive Cytotoxicity by Cytotoxic T Cells in Metabolically Perturbed Tumors

Supplementary Data from Adenosine A2a Receptor Antagonism Restores Additive Cytotoxicity by Cytotoxic T Cells in Metabolically Perturbed Tumors

PDF file, 1359K, Vaccine characteristics of first cycle of all patients. (A) Expression of HLA-ABC, HLA-DR/DP, HLA-DQ, CD80, CD86, CD83, and CCR7 was analyzed by flow cytometry. (B) Tumor antigen expression by DCs 2-4 hrs after electroporation with mRNA encoding gp100 and tyrosinase. Data are shown as percentage of positive DCs used for the first vaccination. The graphs represent mean � SD of all patients.

PDF file - 41K, Clinical protocol and immunization schedule.

Purpose: Regulatory T cells (Tregs) are thought to inhibit antitumor immune responses, and their depletion could therefore have a synergistic effect with therapeutic cancer vaccines. We investigated the impact of three medications on blood Treg frequency in vaccinated cancer patients.Experimental Design: To date, the most specific marker for human Tregs is demethylation in the DNA that encodes the transcription factor FOXP3. Thus, we used a FOXP3 methylation-specific quantitative PCR assay (MS-qPCR) to measure Treg frequencies in the peripheral blood mononuclear cells (PBMCs) of melanoma patients. The patients participated in three clinical trials that combined tumor vaccines with potential Treg-depleting agents: low-dose cyclophosphamide, anti-CD25 monoclonal antibody daclizumab, and the IL-2/diphtheria toxin fusion protein denileukin diftitox.Results: In the nine control patients, blood Treg frequencies varied over time; there was a 46% reduction in one patient. In treated patients, a more than 2-fold decrease in Tregs was observed in one out of 11 patients receiving cyclophosphamide and in four out of 13 receiving daclizumab, but there was no such Treg decrease in any of the six patients who received denileukin diftitox. As a positive control, a more than 2-fold increase in blood Tregs was detected in four out of nine patients who were treated with interleukin-2.Conclusions: We used a MS-qPCR method that detects Tregs but not other activated T lymphocytes; however, none of the Treg-depleting strategies that we tested led, in the majority of patients, to a conservative 50% reduction in blood Tregs. Clin Cancer Res; 17(4); 1–8. ©2010 AACR.

PDF file, 96K, Detection of tumor-specific T cells in SKIL cultures does not require challenge with defined epitopes. Tetramer analysis of SKILs cultured from biopsies of DTH reactions to DCs pulsed with tumor peptides (upper plots) or DCs electroporated with mRNA encoding tumor proteins (lower plots) of patients II-E-09 (A), II-E-03 (B), and II-E-10 (C). This figure shows that sampling DTH biopsy cultures with tetramers yields similar results when the patient is challenged with intradermal injections with DC pulsed with defined epitopes or DC electroporated with mRNA encoding the full tumor antigen.

Supplementary Figure S1; Supplementary Tables S1-S2.

Purpose: Electroporation of dendritic cells (DC) with mRNA encoding tumor-associated antigens (TAA) has multiple advantages compared to peptide loading. We investigated the immunologic and clinical responses to vaccination with mRNA-electroporated DC in stage III and IV melanoma patients.Experimental design: Twenty-six stage III HLA*02:01 melanoma patients scheduled for radical lymph node dissection (stage III) and 19 melanoma patients with irresectable locoregional or distant metastatic disease (referred to as stage IV) were included. Monocyte-derived DC, electroporated with mRNA encoding gp100 and tyrosinase, were pulsed with keyhole limpet hemocyanin and administered intranodally. TAA-specific T-cell responses were monitored in blood and skin-test infiltrating lymphocyte (SKIL) cultures.Results: Comparable numbers of vaccine-induced CD8+ and/or CD4+ TAA-specific T-cell responses were detected in SKIL cultures; 17/26 stage III patients and 11/19 stage IV patients. Strikingly, in this population, TAA-specific CD8+ T cells that recognize multiple epitopes and produce elevated levels of IFNγ upon antigenic challenge in vitro, were significantly more often observed in stage III patients; 15/17 versus 3/11 stage IV patients, P = 0.0033. In stage IV patients, one mixed and one partial response were documented. The presence or absence of IFNγ-producing TAA-specific CD8+ T cells in stage IV patients was associated with marked difference in median overall survival of 24.1 months versus 11.0 months, respectively.Conclusion: Vaccination with mRNA-electroporated DC induces a broad repertoire of IFNγ producing TAA-specific CD8+ and CD4+ T-cell responses, particularly in stage III melanoma patients. Clin Cancer Res; 18(19); 5460–70. ©2012 AACR.

PDF file - 55K, Consort flow chart.

PDF file, 149K, CONSORT flow chart.

PDF file - 62K, This table describes patient details, including disease state and prior treatments.

Purpose: It is unknown whether the route of administration influences dendritic cell (DC)-based immunotherapy. We compared the effect of intradermal versus intranodal administration of a DC vaccine on induction of immunologic responses in melanoma patients and examined whether concomitant administration of interleukin (IL)-2 increases the efficacy of the DC vaccine.Experimental Design: HLA-A2.1+ melanoma patients scheduled for regional lymph node dissection were vaccinated four times biweekly via intradermal or intranodal injection with 12 × 106 to 17 × 106 mature DCs loaded with tyrosinase and gp100 peptides together with keyhole limpet hemocyanin (KLH). Half of the patients also received low-dose IL-2 (9 MIU daily for 7 days starting 3 days after each vaccination). KLH-specific B- and T-cell responses were monitored in blood. gp100- and tyrosinase-specific T-cell responses were monitored in blood by tetramer analysis and in biopsies from delayed-type hypersensitivity (DTH) skin tests by tetramer and functional analyses with 51Cr release assays or IFNγ release, following coculture with peptide-pulsed T2 cells or gp100- or tyrosinase-expressing tumor cells.Results: In 19 of 43 vaccinated patients, functional tumor antigen–specific T cells could be detected. Although significantly more DCs migrated to adjacent lymph nodes upon intranodal vaccination, this was also highly variable with a complete absence of migration in 7 of 24 intranodally vaccinated patients. Intradermal vaccinations proved superior in inducing functional tumor antigen–specific T cells. Coadministration of IL-2 did not further augment the antigen-specific T-cell response but did result in higher regulatory T-cell frequencies.Conclusion: Intradermal vaccination resulted in superior antitumor T-cell induction when compared with intranodal vaccination. No advantage of additional IL-2 treatment could be shown. Clin Cancer Res; 17(17); 5725–35. ©2011 AACR.

Fig. S1 Effect of intratumoral injections with 20 mg/kg S1 Ac53FaxNeu5Ac on B16-F10WT tumor growth. Fig. S2 Responsiveness of melanoma and neuroblastoma cells to Ac53FaxNeu5Ac. S2 Fig. S3 10 mg/kg Ac53FaxNeu5Ac injections are well tolerated. S3 Fig. S4 Immune cell infiltration of tumors injected S4 with Ac53FaxNeu5Ac. Fig. S5 Effect of intratumoral Ac53FaxNeu5Ac injections on S5 systemic sialylation. Fig. S6 Effect of intratumoral Ac53FaxNeu5Ac injections on tumor-infiltrating S6 immune cells and immune cell populations in (tumor-draining) lymph nodes and spleen. Fig. S7 Effect of intratumoral Ac53FaxNeu5Ac injections on S7 immune cell populations in (tumor-draining) lymph nodes and spleen. Fig. S8 Depletion of NK cells and CD8+ T cells prior to of B16-F10WT S8 tumor inoculation. Fig. S9 Combination of sialic acid blockade with clodronate liposomes S9 and anti-Gr-1 antibodies. Fig. S10 In vitro killing of Ac53FaxNeu5Ac-treated tumor cells and expression of S10 Siglecs on OT-I T cells Fig. S11 B16-F10OVA cell surface molecule expression and purification S11 and sialylation of OT-I CD8+ T cells. Fig. S12 Systemic effect of sialic acid blockade on CpG-induced S12 dendritic cell maturation. Fig. S13 Systemic effect of sialic acid blockade on CD8+ T cell numbers. S13

Purpose: Anticancer dendritic cell (DC) vaccines require the DCs to relocate to lymph nodes (LN) to trigger immune responses. However, these migration rates are typically very poor. Improving the targeting of ex vivo generated DCs to LNs might increase vaccine efficacy and reduce costs. We investigated DC migration in vivo in humans under different conditions.Experimental Design:HLA-A*02:01 patients with melanoma were vaccinated with mature DCs loaded with tyrosinase and gp100 peptides together with keyhole limpet hemocyanin (NCT00243594). For this study, patients received an additional intradermal vaccination with 111In-labeled mature DCs. The injection site was pretreated with nonloaded, activated DCs, TNFα, or Imiquimod; granulocyte macrophage colony-stimulating factor was coinjected or smaller numbers of DCs were injected. Migration was measured by scintigraphy and compared with an intrapatient control vaccination. In an ex vivo tissue model, we measured CCL21-directed migration of 19F-labeled DCs over a period of up to 12 hours using 19F MRI to supplement our patient data.Results: Pretreatment of the injection site induced local inflammatory reactions but did not improve migration rates. Both in vitro and in vivo, reduction of cell numbers to 5 × 106 or less cells per injection improved migration. Furthermore, scintigraphy is insufficient to study migration of such small numbers of 111In-labeled DCs in vivo.Conclusion: Reduction of cell density, not pretreatment of the injection site, is crucial for improved migration of DCs to LNs in vivo. Clin Cancer Res; 19(6); 1525–33. ©2013 AACR.

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PDF file - 34K, KLH specific responses

PDF file - 233K, Definition of criteria for SKIL culture evaluation: Three examples are shown to illustrate the definition of SKIL culture criteria. (A) Criterion III, one patient (IV-B-16-St) with a clear population of TAA-specific CD8+ T cells in SKIL cultures, which produce high levels of IFNg upon encounter of both the defined gp100 peptides and naturally processed gp100 presented by a HLA-A*02:01 positive melanoma cell line (Mel624). Moderate amounts of IL-2 are produced and minimal production of IL-5, representing a clear IFNg dominant cytokine profile. (B) Criterion II, a patient (IV-B-11-Ro) with TAA-specific CD8+ T cells in SKIL cultures which produce high levels of IFNg and IL-2 upon encounter of the gp100 peptide, but fail to recognize the naturally processed gp100. (C) Criterion I, a patient (IV-A-07-Th) with a population of TAA-specific CD8+ T cells in SKIL cultures, recognizing the g100-154 peptide, but not the naturally processed gp100. Furthermore, those TAA-specific CD8+ T cells do not produce IFNg but produce elevated levels of IL-5 instead, indicating that the immune system is skewed towards tumor tolerance

PDF file - 40K, Vaccine characteristics

PDF file - 73K, Patient selection based on SKIL criteria: SKIL criteria are applied to select patients with immune responses meeting increasingly stringent criteria

PDF file - 52K, Characteristics matched controls

PDF file - 51K, CONSORT flow chart

PDF file - 71K, KLH-specific T cell responses according to SKIL classification: Regardless of the number of epitopes or the increasingly stringent criteria for TAA-specific immune responses; the levels of KLH-specific T cell responses were similar and highly variable between individuals. One-way ANOVA was used for comparison of KLH-specific T cell responses in groups of patients with increasing breadth of TAA-specific CD8+ T cell responses. Student t-test was used for comparison of KLH-specific T cell responses in groups of patients as defined by different SKIL criteria

Immunostimulatory cytidyl guanosyl (CpG) motifs are of great interest as cancer vaccine adjuvants. They act as potent inducers of Th1 responses, including the activation of cytotoxic CD8+ T lymphocytes (CTL). Whereas animal models have provided clear evidence that CpG enhances antitumor immunity, clinical trials in humans have thus far been less successful. Applying cryosurgery as an instant in situ tumor destruction technique, we now show that timing of CpG administration crucially affects colocalization of antigen and CpG within EEA-1+ and LAMP-1+ compartments within dendritic cells in vivo. Moreover, antigen/CpG colocalization is directly correlated with antigen cross-presentation, the presence of CTL, and protective antitumor immunity. Thus, failure or success of CpG as a vaccine adjuvant may depend on colocalization of antigen/CpG inside DCs and hence on the timing of CpG administration. These data might aid in the design of future immunotherapeutic strategies for cancer patients. [Cancer Res 2008;68(13):5390–6]

Supplementary Figure 1 from In vivo Colocalization of Antigen and CpG within Dendritic Cells Is Associated with the Efficacy of Cancer Immunotherapy

PDF file - 30K, Levels of induration according to SKIL classification: Regardless of the number of epitopes or the increasingly stringent criteria for TAA-specific immune responses; the maximum induration at the injection site was similar in all groups. One-way ANOVA was used for comparison of induration in groups of patients with increasing breadth of TAA-specific CD8+ T cell responses. Student t-test was used for comparison of induration in groups of patients as defined by different SKIL criteria

PDF file - 34K, Schedule of treatment and monitoring:Patients received 3 vaccinations a biweekly interval, followed a delayed type hypersensitivity (DTH) skin test. After completing one cycle and if no progression of disease was confirmed on CT-scan, patients were eligible to receive a maximum of two more cycles and were followed up to 5 years. Abbreviations: Vx = visit x; M = month, D = day, W = week, Y = year, vacx = vaccination x; FU = follow-up; * follow-up visits were planned every 3 months; # CT-scans were planned every 6 months

Cytotoxic T lymphocytes (CTL) are antigen-specific effector cells with the ability to eradicate cancer cells in a contact-dependent manner. Metabolic perturbation compromises the CTL effector response in tumor subregions, resulting in failed cancer cell elimination despite the infiltration of tumor-specific CTLs. Restoring the functionality of these tumor-infiltrating CTLs is key to improve immunotherapy. Extracellular adenosine is an immunosuppressive metabolite produced within the tumor microenvironment. Here, by applying single-cell reporter strategies in 3D collagen cocultures in vitro and progressing tumors in vivo, we show that adenosine weakens one-to-one pairing of activated effector CTLs with target cells, thereby dampening serial cytotoxic hit delivery and cumulative death induction. Adenosine also severely compromised CTL effector restimulation and expansion. Antagonization of adenosine A2a receptor (ADORA2a) signaling stabilized and prolonged CTL–target cell conjugation and accelerated lethal hit delivery by both individual contacts and CTL swarms. Because adenosine signaling is a near-constitutive confounding parameter in metabolically perturbed tumors, ADORA2a targeting represents an orthogonal adjuvant strategy to enhance immunotherapy efficacy.

Saponin-based adjuvants (SBAs) are promising new adjuvants that stand out as they not only enforce CD4 + T cell-mediated immunity and antibody responses, but also induce an unprecedented level of antigen cross-presentation by dendritic cells (DC) and subsequent CD8 + T cell activation. We discovered that SBA's ability to boost cross-presentation depends on the induction of lipid bodies (LBs). Moreover, the MHCII

IntroductionIn situ tumor ablation releases a unique repertoire of antigens from a heterogeneous population of tumor cells. High-intensity focused ultrasound (HIFU) is a completely noninvasive ablation therapy that can be used to ablate tumors either by heating (thermal (T)-HIFU) or by mechanical disruption (mechanical (M)-HIFU). How different HIFU ablation techniques compare with respect to their antigen release profile, their activation of responder T cells, and their ability to synergize with immune stimuli remains to be elucidated.Methods and resultsHere, we compare the immunomodulatory effects of T-HIFU and M-HIFU ablation with or without the TLR9 agonist CpG in the ovalbumin-expressing lymphoma model EG7. M-HIFU ablation alone, but much less so T-HIFU, significantly increased dendritic cell (DC) activation in draining lymph nodes (LNs). Administration of CpG following T- or M-HIFU ablation increased DC activation in draining LNs to a similar extend. Interestingly, ex vivo co-cultures of draining LN suspensions from HIFU plus CpG treated mice with CD8+ OT-I T cells demonstrate that LN cells from M-HIFU treated mice most potently induced OT-I proliferation. To delineate the mechanism for the enhanced anti-tumor immune response induced by M-HIFU, we characterized the RNA, DNA and protein content of tumor debris generated by both HIFU methods. M-HIFU induced a uniquely altered RNA, DNA and protein profile, all showing clear signs of fragmentation, whereas T-HIFU did not. Moreover, western blot analysis showed decreased levels of the immunosuppressive cytokines IL-10 and TGF-β in M-HIFU generated tumor debris compared to untreated tumor tissue or T-HIFU.ConclusionCollectively, these results imply that M-HIFU induces a unique context of the ablated tumor material, enhancing DC-mediated T cell responses when combined with CpG.

Synthetic sugar analogs are widely applied in metabolic oligosaccharide engineering (MOE) and as novel drugs to interfere with glycoconjugate biosynthesis. However, mechanistic insights on their exact cellular metabolism over time are mostly lacking. We combined ion-pair UHPLC-QqQ mass spectrometry using tributyl- and triethylamine buffers for sensitive analysis of sugar metabolites in cells and organisms and identified low abundant nucleotide sugars, such as UDP-arabinose in human cell lines and CMP-sialic acid (CMP-NeuNAc) in Drosophila. Furthermore, MOE revealed that propargyloxycarbonyl (Poc) labeled ManNPoc was metabolized to both CMP-NeuNPoc and UDP-GlcNPoc. Finally, time-course analysis of the effect of antitumor compound 3Fax-NeuNAc by incubation of B16-F10 melanoma cells with N-acetyl-D-[UL-13C6]glucosamine revealed full depletion of endogenous ManNAc 6-phosphate and CMP-NeuNAc within 24 hour. Thus, dynamic tracing of sugar metabolic pathways provides a general approach to reveal time-dependent insights into the metabolism of synthetic sugars, which is important for the rational design of analogs with optimized effects., Glycobiology, 32 (3), ISSN:0959-6658