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Supplementary Figure 7-Efficacy of anti-tumor treatment with CpG is dependent on an CD8+ T cell response.

Supplementary Figure 1-Treatment with CpG causes a reduction of Treg within the CD4 T cell population and an increase of CD8+ tumor-infiltrating cells.

Supplementary Figure 6-Type I interferon is a key mediator in the process of CCL22 suppression and tumor regression.

Supplementary Figure 3-Correlation (corr) of intratumoral FoxP3+ cells and CCL22 levels in CT26 tumors from untreated mice.

Supplementary Figure 2-CpG-induced suppression of Treg infiltration in different mouse tumor models.

The chemokine CCL22 is abundantly expressed in many types of cancer and is instrumental for intratumoral recruitment of regulatory T cells (Treg), an important subset of immunosuppressive and tumor-promoting lymphocytes. In this study, we offer evidence for a generalized strategy to blunt Treg activity that can limit immune escape and promote tumor rejection. Activation of innate immunity with Toll-like receptor (TLR) or RIG-I–like receptor (RLR) ligands prevented accumulation of Treg in tumors by blocking their immigration. Mechanistic investigations indicated that Treg blockade was a consequence of reduced intratumoral CCL22 levels caused by type I IFN. Notably, stable expression of CCL22 abrogated the antitumor effects of treatment with RLR or TLR ligands. Taken together, our findings argue that type I IFN blocks the Treg-attracting chemokine CCL22 and thus helps limit the recruitment of Treg to tumors, a finding with implications for cancer immunotherapy. Cancer Res; 75(21); 4483–93. ©2015 AACR.

Supplementary Figure 4-Inducible secretion of CCL22 by CT26-CCL22dox cells.

Supplementary Figure 5-CCL22 secretion of human tumor cell lines upon IFN-γ stimulation.

CAR therapy is efficacious in relapsed/refractory CD19-positive malignancies including B-ALL. In AML, conventional 2nd-generation CAR therapies are being evaluated clinically. Some of the potential obstacles are antigen-low leukemia escape and on-target toxicities due to widespread CAR target expression in normal hematopoietic cells. We hypothesized that novel targets and fine-tuned combinatorial CAR approaches may enable distinctive target elimination based on differential antigen co-expression patterns in AML vs normal cells, thereby maintaining anti-leukemic efficacy while limiting toxicity on normal cells. Here, we present our target phenotypic profiling of primary AML (n>30 r/r AML patients) and normal hematopoietic cells, and link it with CAR efficacy and changes in normal hematopoiesis. Using spectral flow cytometry on bone marrow and peripheral blood from AML patients and healthy controls, we quantified differential target co-expression of several AML targets, including CD33, CD123, CLEC12A and the novel target ADGRE2. We estimated the numbers of surface molecules per cell and created two-dimensional maps of combinatorial target densities in AML vs normal. In this analysis, the combination of ADGRE2+CLEC12A offered the best therapeutic window. We developed a combinatorial CAR+CCR platform, ADCLEC.syn1, consisting of an ADGRE2-targeting 28z1XX-CAR and a CLEC12A-targeting chimeric costimulatory receptor (CCR) providing additional 4-1BB costimulation. This CAR+CCR configuration triggers killing of cells with high CAR target density alone, whereas cells with low CAR target density are only killed if the CCR target is co-expressed (IF-BETTER gate). Both in vitro and in vivo, we used MOLM13 AML cell line variants matching a variety of different ADGRE2 and CLEC12A target density combinations found in AML or normal hematopoietic cells. The observed target density thresholds for ADCLEC.syn1-mediated cell lysis demonstrated potential for sparing vital normal hematopoietic cells. In addition, we evaluated ADCLEC.syn1 in several molecularly distinct AML PDX models with clinically representative target phenotypes, achieving long-term AML remissions in all studied PDX models. In a humanized mouse model co-engrafted with MOLM13 AML cells, ADCLEC.syn1 T cells rapidly induced complete and durable AML remissions in all mice, with minimal toxicity of normal hematopoietic cells compared to control CARs. Overall, we profiled antigen densities of several CAR target combinations in AML and normal hematopoietic cells, which informed the development of the ADCLEC.syn1 platform. Pre-clinical in vivo models based on AML with clinically representative target densities demonstrated high anti-leukemic efficacy of ADCLEC.syn1 and established killing thresholds with potential for sparing normal hematopoietic cells. A first-in-human phase 1 clinical trial evaluating ADCLEC.syn1 T cells is anticipated to be initiated at MSKCC in 2023. Citation Format: Sascha Haubner, Jorge Mansilla-Soto, Sarah Nataraj, Friederike Kogel, Qing Chang, Elisa De Stanchina, Kathryn Fraser, Jae H. Park, Xiuyan Wang, Isabelle Rivière, Michel Sadelain. ADCLEC.syn1 CAR T cells detect combinatorial target signatures to safely prevent antigen-low AML escape [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr PR03.

BackgroundChimeric antigen receptors (CARs) engage antigen independently of HLA and enable sustained T cell proliferation when they are endowed with both activating and costimulatory functions. While remission rates have been noticeably elevated in numerous clinical trials targeting CD19, CD22 or BCMA, relapses are common. One of the several underlying relapse mechanisms is antigen escape, which refers to a relapsing tumor that is either negative for the targeted antigen or expresses the latter at a low level. Failure to eliminate antigen-low tumors raises questions about the sensitivity of CARs and the minimum antigen density that is required for effective tumor eradication. Unlike CARs, TCRs engage antigen in an HLA-dependent manner, and they do so with high sensitivity. We hypothesized that a TCR/CD3 complex containing the same heavy and light immunoglobulin chains as a CAR will display increased sensitivity to the target antigen.MethodsWe edited the TRAC locus in human primary T cells to establish a novel antigen receptor structure, termed HLA-independent TCR or HIT receptor, by incorporating into the TCR/CD3 complex the same heavy and light chains as those of a corresponding CAR. We assessed their antigen sensitivity against a panel of cell lines expressing different antigen levels, analyzing their cytotoxicity, cytokine secretion, signaling response and degranulation activity. HIT and CAR T cells were further evaluated for their anti-tumor response using established ALL and AML mouse models.ResultsCD19-TRAC-HIT and CD19-TRAC-CAR T cells lysed wild-type NALM6 (~27,000 CD19 molecules) and NALM6 variants with 100-fold less CD19. As CD19 levels decreased further, CAR T cells no longer killed their target, in contrast to HIT T cells. HIT T cells showed increased expression of IFN-gamma, IL-2 and TNF-alpha upon exposure to NALM6 cells expressing ~20 CD19 molecules per cell, compared to CAR T cells. This increased sensitivity of HIT receptors correlated to their greater signaling response, upon exposure to the low-antigen-density NALM6. Phospho-proteomic analyses further confirmed this increased response of HIT T cells to low antigen levels. Altogether, these results confirm that HIT receptors endow T cells with greater antigen sensitivity than canonical CARs. We further showed that HIT T cells have higher in vivo anti-tumor activity compared to CAR T cells in mice bearing low-antigen-density ALL or AML.ConclusionsHIT receptors consistently afford high antigen sensitivity and mediate tumor recognition beyond what current CARs can provide. HIT receptors open new prospects for targeting cell surface antigens of low abundance.Ethics ApprovalEight- to 12-week-old NOD/SCID/IL-2Rgamma-null (NSG) male mice (Jackson Laboratory) were used under a protocol approved by the MSKCC Institutional Animal Care and Use Committee.

Chimeric antigen receptors (CARs) are receptors for antigen that direct potent immune responses. Tumor escape associated with low target antigen expression is emerging as one potential limitation of their efficacy. Here we edit the TRAC locus in human peripheral blood T cells to engage cell-surface targets through their T cell receptor-CD3 complex reconfigured to utilize the same immunoglobulin heavy and light chains as a matched CAR. We demonstrate that these HLA-independent T cell receptors (HIT receptors) consistently afford high antigen sensitivity and mediate tumor recognition beyond what CD28-based CARs, the most sensitive design to date, can provide. We demonstrate that the functional persistence of HIT T cells can be augmented by constitutive coexpression of CD80 and 4-1BBL. Finally, we validate the increased antigen sensitivity afforded by HIT receptors in xenograft mouse models of B cell leukemia and acute myeloid leukemia, targeting CD19 and CD70, respectively. Overall, HIT receptors are well suited for targeting cell surface antigens of low abundance.

Targeted immunotherapy in acute myeloid leukemia (AML) is challenged by the lack of AML-specific target antigens and clonal heterogeneity, leading to unwanted on-target off-leukemia toxicity and risk of relapse from minor clones. We hypothesize that combinatorial targeting of AML cells can enhance therapeutic efficacy without increasing toxicity. To identify target antigen combinations specific for AML and leukemic stem cells, we generated a detailed protein expression profile based on flow cytometry of primary AML (n = 356) and normal bone marrow samples (n = 34), and a recently reported integrated normal tissue proteomic data set. We analyzed antigen expression levels of CD33, CD123, CLL1, TIM3, CD244 and CD7 on AML bulk and leukemic stem cells at initial diagnosis (n = 302) and relapse (n = 54). CD33, CD123, CLL1, TIM3 and CD244 were ubiquitously expressed on AML bulk cells at initial diagnosis and relapse, irrespective of genetic characteristics. For each analyzed target, we found additional expression in different populations of normal hematopoiesis. Analyzing the coexpression of our six targets in all dual combinations (n = 15), we found CD33/TIM3 and CLL1/TIM3 to be highly positive in AML compared with normal hematopoiesis and non-hematopoietic tissues. Our findings indicate that combinatorial targeting of CD33/TIM3 or CLL1/TIM3 may enhance therapeutic efficacy without aggravating toxicity in immunotherapy of AML.

CAR T cell therapy provides a potent therapeutic option in various B cell-related hematologic malignancies. One of the major efficacy challenges is escape of tumor cells with low antigen density, which has been clinically observed in several malignancies treated with CAR therapy. Novel concepts of CAR design are needed to address phenotypic heterogeneity including clonal variability of target antigen expression. In the study presented here, we focused on AML and selected ADGRE2 as CAR target due to its high rate of positivity on AML bulk and leukemic stem cells (LSC) in a molecularly heterogeneous AML patient population. We chose an ADGRE2-CAR with optimized scFv affinity and fine-tuned CD3zeta signaling to achieve an ideal killing threshold that would allow for sparing of ADGRE2-low normal cells. We hypothesized that co-targeting of a second AML-related antigen may mitigate potential CAR target antigen-low AML escape and we identified CLEC12A as preferential co-target due to its non-overlapping expression profiles in normal hematopoiesis and other vital tissues. We developed ADCLEC.syn1, a novel combinatorial CAR construct consisting of an ADGRE2-targeting 28z1XX-CAR and a CLEC12A-targeting chimeric costimulatory receptor (CCR). ADCLEC.syn1 operates based on what we describe as "IF-BETTER" gate: High CAR target expression alone triggers killing, whereas low CAR target expression does not, unless a CCR target is present. Additional CCR interaction lowers the threshold for CAR-mediated killing through increased avidity and costimulation, allowing for higher CAR sensitivity that is purposefully limited to target cells expressing both antigens. In the context of ADCLEC.syn1, ADGRE2-high/CLEC12A-negative AML cells can trigger cell lysis while ADGRE2-low/CLEC12A-negative normal cells are spared. Importantly, ADGRE2-low/CLEC12A-high AML cells are also potently eliminated, preventing ADGRE2-low AML escape. Using NSG in-vivo xenograft models of engineered MOLM13 AML cell line variants with low levels of ADGRE2 to model antigen escape, we found that ADCLEC.syn1 outperforms a single-ADGRE2-CAR lacking assistance via CLEC12A-CCR. Importantly, ADCLEC.syn1 also outperformed an otherwise identical alternative dual-CAR version (OR-gated ADGRE2-CAR+CLEC12A-CAR) in the setting of both ADGRE2-high and ADGRE2-low MOLM13, further underlining the importance of fine-tuned overall signaling. We confirmed high in-vivo potency against diverse AML cell lines with a wide range of ADGRE2 and CLEC12A levels reflecting population-wide AML heterogeneity. At clinically relevant CAR T cell doses, ADCLEC.syn1 induced complete and durable remissions in xenograft models of MOLM13 (ADGRE2-high/CLEC12A-low) and U937 (ADGRE2-low/CLEC12A-high). ADCLEC.syn1 CAR T cells were found to be functionally persistent for >70 days, with a single CAR T cell dose potently averting relapse modeled via AML re-challenges. In summary, we provide pre-clinical evidence that an "IF-BETTER"-gated CAR+CCR T cell (ADCLEC.syn1) can outperform a single-CAR T cell (ADGRE2-CAR) and a dual-CAR T cell (ADGRE2-CAR+CLEC12A-CAR). ADCLEC.syn1 enhances antileukemic efficacy and prevents antigen-low AML escape via detection of a rationally selected combinatorial target antigen signature that is commonly found in AML but limited in vital normal cells. Using phenotypically representative AML xenograft models and clinically relevant T cell doses, we demonstrate high therapeutic potential of ADCLEC.syn1 CAR T cells, further supporting clinical translation of an "IF-BETTER"-gated CAR concept into a phase 1 trial. Disclosures Haubner: Takeda Pharmaceuticals Company Ltd.: Patents & Royalties: Co-inventor of IP that MSK licensed to Takeda, Research Funding. Mansilla-Soto: Takeda Pharmaceuticals Company Ltd.: Patents & Royalties; Atara Biotherapeutics: Patents & Royalties; Fate Therapeutics: Patents & Royalties; Mnemo Therapeutics: Patents & Royalties. He: Takeda Pharmaceuticals Company Ltd.: Ended employment in the past 24 months, Patents & Royalties. Park: Curocel: Consultancy; BMS: Consultancy; Innate Pharma: Consultancy; Autolus: Consultancy; Servier: Consultancy; Kite Pharma: Consultancy; Affyimmune: Consultancy; Intellia: Consultancy; Minerva: Consultancy; PrecisionBio: Consultancy; Amgen: Consultancy; Kura Oncology: Consultancy; Artiva: Consultancy; Novartis: Consultancy. Rivière: Juno Therapeutics: Patents & Royalties; Fate Therapeutics: Other: Provision of Services, Patents & Royalties; Centre for Commercialization of Cancer Immunotherapy: Other: Provision of Services; The Georgia Tech Research Corporation (GTRC): Other: Provision of Services (uncompensated); FloDesign Sonics: Other: Provision of Services. Sadelain: NHLBI Gene Therapy Resource Program: Other: Provision of Services (uncompensated); St. Jude Children's Research Hospital: Other: Provision of Services; Minerva Biotechnologies: Patents & Royalties; Mnemo Therapeutics: Patents & Royalties; Juno Therapeutics: Patents & Royalties; Fate Therapeutics: Other: Provision of Services (uncompensated), Patents & Royalties; Ceramedix: Patents & Royalties; Takeda Pharmaceuticals: Other: Provision of Services, Patents & Royalties; Atara Biotherapeutics: Patents & Royalties.

Im August 2017 ist in den USA die erste Immuntherapie fur die Behandlung der rezidivierten/refraktaren akuten lymphatischen Leukamie zugelassen worden, die auf T-Zellen mit chimarem Antigenrezeptor (CAR-T-Zellen) basiert; bei weiteren akuten Leukamien wird das Konzept derzeit gepruft bzw. entwickelt. Daneben spielen vor allem Wirkstoff-konjugierte und bispezifische Antikorper eine wichtige Rolle fur die immunonkologische Therapie von akuten Leukamien.

Despite advances in the treatment of acute myeloid leukemia (AML), novel therapies are needed to induce deeper and more durable clinical response. Bispecific T-cell Engager (BiTE) molecules, which redirect patient T cells to lyse tumor cells, are a clinically validated modality for hematologic malignancies. Due to broad AML expression and limited normal tissue expression, fms-related tyrosine kinase 3 (FLT3) is proposed to be an optimal BiTE molecule target. Expression profiling of FLT3 was performed in primary AML patient samples and normal hematopoietic cells and nonhematopoietic tissues. Two novel FLT3 BiTE molecules, one with a half-life extending (HLE) Fc moiety and one without, were assessed for T-cell–dependent cellular cytotoxicity (TDCC) of FLT3-positive cell lines in vitro, in vivo, and ex vivo. FLT3 protein was detected on the surface of most primary AML bulk and leukemic stem cells but only a fraction of normal hematopoietic stem and progenitor cells. FLT3 protein detected in nonhematopoietic cells was cytoplasmic. FLT3 BiTE molecules induced TDCC of FLT3-positive cells in vitro, reduced tumor growth and increased survival in AML mouse models in vivo. Both molecules exhibited reproducible pharmacokinetic and pharmacodynamic profiles in cynomolgus monkeys in vivo, including elimination of FLT3-positive cells in blood and bone marrow. In ex vivo cultures of primary AML samples, patient T cells induced TDCC of FLT3-positive target cells. Combination with PD-1 blockade increased BiTE activity. These data support the clinical development of an FLT3 targeting BiTE molecule for the treatment of AML.

Rapp et al. demonstrate that dendritic cells in the lymph node secrete CCL22 to build cell–cell contacts with CCR4-expressing regulatory T cells, leading to immune suppression. Conversely, CCL22 deficiency results in enhanced T cell immunity, shown here in the setting of vaccination, cancer, and inflammatory disease., Chemokines have crucial roles in organ development and orchestration of leukocyte migration. The chemokine CCL22 is expressed constitutively at high levels in the lymph node, but the functional significance of this expression is so far unknown. Studying a newly established CCL22-deficient mouse, we demonstrate that CCL22 expression by dendritic cells (DCs) promotes the formation of cell–cell contacts and interaction with regulatory T cells (T reg) through their CCR4 receptor. Vaccination of CCL22-deficient mice led to excessive T cell responses that were also observed when wild-type mice were vaccinated using CCL22-deficient DCs. Tumor-bearing mice with CCL22 deficiency showed prolonged survival upon vaccination, and further, CCL22-deficient mice had increased susceptibility to inflammatory disease. In conclusion, we identify the CCL22–CCR4 axis as an immune checkpoint that is crucial for the control of T cell immunity., Graphical Abstract

Background: The clinical course of follicular lymphoma (FL) is characterized by a slow progression over years with continuous relapses despite good response to initial treatment. The median overall survival is 10 to more than 15 years. Standard therapy for patients requiring treatment consists of an anti-CD 20 antibody combined with chemotherapy followed by antibody maintenance. With this combination a 1-year-PFS of 93% was seen in the GLSG-2000 trial (Hiddemann et al, Blood 2005). Because of the substantial side effects of chemotherapy such as infections, secondary malignancies and impairment of the stem cell reserve novel "chemotherapy-free" treatment approaches could substantially improve the treatment tolerability in FL. The BTK-inhibitor ibrutinib has demonstrated promising activity in patients with iNHL, CLL and MCL. Anticipating the recent reports on a superior activity of obinutuzumab as compared to rituximab in the GALLIUM trial (Marcus et al., NEJM 2017), the GLSG initiated a phase II study combining ibrutinib and obinutuzumab to explore the efficacy and safety of this "chemotherapy-free" alternative. Methods: ALTERNATIVE is a prospective multicenter single-arm phase 2 study of the combination of ibrutinib and obinutuzumab in 98 patients with previously untreated FL and a high tumor burden (defined by modified GELF criteria) in need of treatment. Induction comprises 6 cycles of obinutuzumab at a dose of 1000 mg by intravenous infusion on days 1, 8, 15 of cycle 1 and on day 1 of cycles 2-6 to be given every 21 days. Ibrutinib is administered orally at a dose of 560 mg once daily throughout all 6 cycles. In patients with at least partial response (defined by Cheson Response Criteria 2007) after the end of induction, maintenance with obinutuzumab (1000mg every 8 weeks) plus ibrutinib (560mg daily) is given for an additional 24 months. In patients remaining MRD positive at 30 months ibrutinib is continued for another 12 months in an extended maintenance setting without obinutuzumab. The primary efficacy endpoint is the rate of investigator-assessed PFS one year after registration. Response rates at end of induction, after one year and after end of maintenance, duration of response, percentage of progression during induction and maintenance, time to treatment failure, overall survival, duration of molecular remission in MRD negative patients and safety are key secondary endpoints. Results: 98 patients with advanced stage FL were included, The median age was 59 years (29-81), 60% were male and 40% had a high risk FLIPI, 90% stage III/IV disease and 10% were stage II with a high tumor burden. Response to in induction was 90% (87/97) with 85% (82/97) PR and 5% (5/97) CR. 5 patients (5%) progressed during induction. Of the 82 patients with PR after end of induction, 8 patients achieved a CR during the first 6 months of maintenance treatment. 95 patients were evaluable for the primary endpoint of 1-year-PFS and 76 patients (80%) remained alive and free of progression at this timepoint. 18 patients progressed in the first year, two of whom died due to progressive disease. One additional death was caused by a non-lymphoma related event. An MRD-marker was found in 65 patients. MRD at the end of induction was evaluable for 63 patients. 44 patients (70%) were MRD negative after induction treatment. Of the 42 patients with follow-up MRD peripheral blood or bone marrow samples, 35 (83%) were MRD negative one year after registration. Therapy was generally well tolerated. Most common adverse events were diarrhea in 30% of patients, rash in 25% and fatigue and nasopharyngitis (common cold) in 23% and 20%, respectively. Concerning hematotoxicity grade 3-4 neutropenia and thrombopenia were seen in 8% and 4% of patients, respectively. Severe (>=grade 3) infectious complications were rare (6% pneumonia/bronchitis, 2% sepsis, 7% other infections). Conclusions: The chemotherapy - free combination of ibrutinib and obinutuzumab showed high anti-lymyphoma activity with high overall response rates and a high proportion of MRD negativity at one year. While the combination of ibrutinib and obinutuzumab was associated with a low toxicity profile, the combination was inferior to the published results of conventional immunochemotherapies in terms of the primary efficacy endpoint (1-year-PFS). Further evaluations might demonstrate whether subgroups exist which particularly benefit clinically from this low toxicity regime. Figure Figure. Disclosures Schmidt: Celgene: Honoraria; Gilead: Honoraria, Other: Travel Grants; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grants. Buske:Bayer: Research Funding; Roche: Honoraria, Research Funding; Janssen: Honoraria, Research Funding. Viardot:Amgen: Consultancy; Gilead Kite: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Roche: Consultancy, Honoraria. Keller:BMS: Consultancy; Roche: Consultancy; Takeda: Consultancy, Research Funding; Janssen-Cilag: Consultancy, Equity Ownership; MSD: Consultancy; Celgene: Research Funding. Graeven:Roche: Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria. Marks:Merck: Honoraria; BMS: Honoraria; Servier: Honoraria. Hänel:Novartis: Honoraria; Roche: Honoraria; Amgen: Honoraria; Takeda: Honoraria. Liersch:Roche: Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria. Dürig:Celgene: Honoraria; Roche: Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria. Hoster:Roche Pharma AG: Other: Travel support, Research Funding; F. Hoffman-La Roche: Other: Travel support, Research Funding. Unterhalt:F. Hoffman-La Roche: Other: Travel support. Hiddemann:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffman-La Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Research Funding.

The advent of new immunotherapeutic agents in clinical practice has revolutionized cancer treatment in the past decade, both in oncology and hematology. The transfer of the immunotherapeutic concepts to the treatment of acute myeloid leukemia (AML) is hampered by various characteristics of the disease, including non-leukemia-restricted target antigen expression profile, low endogenous immune responses, and intrinsic resistance mechanisms of the leukemic blasts against immune responses. However, considerable progress has been made in this field in the past few years. Within this manuscript, we review the recent developments and the current status of the five currently most prominent immunotherapeutic concepts: (1) antibody-drug conjugates, (2) T cell-recruiting antibody constructs, (3) chimeric antigen receptor (CAR) T cells, (4) checkpoint inhibitors, and (5) dendritic cell vaccination. We focus on the clinical data that has been published so far, both for newly diagnosed and refractory/relapsed AML, but omitting immunotherapeutic concepts in conjunction with hematopoietic stem cell transplantation. Besides, we have included important clinical trials that are currently running or have recently been completed but are still lacking full publication of their results. While each of the concepts has its particular merits and inherent problems, the field of immunotherapy of AML seems to have taken some significant steps forward. Results of currently running trials will reveal the direction of further development including approaches combining two or more of these concepts.

Inhibitors of dipeptidylpeptidase IV (DPP-IV) represent a novel class of frequently used anti-diabetic drugs. In addition to its function in metabolic regulation, DPP-IV also plays a role in the immune system. Whether the DPP-IV inhibitors sitagliptin, vildagliptin or saxagliptin impair immune responses is, however, currently unknown. Here, we investigated the effect of these agents on both innate and adaptive immunity. We found that the DPP-IV inhibitors did not affect the innate immune response induced by Toll-like receptor (TLR) ligands, as cytokine secretion and induction of co-stimulatory molecules by human blood mononuclear cells was not impaired. Furthermore, proliferation of T cells and suppressive function of regulatory T cells was preserved. Mice treated with vildagliptin showed normal cytokine production, immune cell activation and lymphocyte trafficking upon TLR activation. Thus, crucial immunological parameters remain unaffected upon treatment with DPP-IV inhibitors, a fact that is reassuring with respect to safety of these drugs.

In cancer patients, immunosuppression through regulatory T cells (Treg) is a crucial component of tumor immune evasion and contributes to disease progression. Tumor-infiltrating Treg in particular suppress local effector T cell responses and are associated with poor prognosis in tumors such as human pancreatic cancer or hepatocellular carcinoma (HCC). The chemokine CCL22 is known to recruit Treg into the tumor tissue and many types of human tumors are known to express high levels of CCL22. The mechanisms leading to intratumoral secretion of CCL22 are so far unknown. We demonstrate here that intratumoral CCL22 is induced in tumor-infiltrating immune cells through cancer cell-derived interleukin-1 (IL-1α). In pancreatic cancer and HCC, CCL22 is produced by intratumoral dendritic cells, while the cancer cells themselves do not secrete CCL22 in vitro and in vivo. Incubation of human peripheral blood mononuclear cells (PBMC) or murine splenocytes with tumor cells or tumor cell supernatants strongly induced CCL22 secretion in vitro. Tumor cell supernatants contained IL-1 and CCL22 induction in PBMC could be specifically prevented by the IL-1 receptor antagonist anakinra or by transfection of tumor cell lines with IL-1 siRNA, leading to a suppression of Treg migration. In conclusion, we identify here tumor cell-derived IL-1α as a major inducer of the Treg attracting chemokine CCL22 in human cancer cells. Therapeutic blockade of the IL-1 pathway could represent a promising strategy to inhibit tumor-induced immunosuppression.

The chemokine CCL22 is abundantly expressed in many types of cancer and is instrumental for intratumoral recruitment of regulatory T cells (Treg), an important subset of immunosuppressive and tumor-promoting lymphocytes. In this study, we offer evidence for a generalized strategy to blunt Treg activity that can limit immune escape and promote tumor rejection. Activation of innate immunity with Toll-like receptor (TLR) or RIG-I–like receptor (RLR) ligands prevented accumulation of Treg in tumors by blocking their immigration. Mechanistic investigations indicated that Treg blockade was a consequence of reduced intratumoral CCL22 levels caused by type I IFN. Notably, stable expression of CCL22 abrogated the antitumor effects of treatment with RLR or TLR ligands. Taken together, our findings argue that type I IFN blocks the Treg-attracting chemokine CCL22 and thus helps limit the recruitment of Treg to tumors, a finding with implications for cancer immunotherapy. Cancer Res; 75(21); 4483–93. ©2015 AACR.