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Melanoma is the deadliest form of skin cancer showing rising incidence over the past years. New insights into the mechanisms of melanoma progression contributed to the development of novel treatment options, such as immunotherapies. However, acquiring resistance to treatment poses a big problem to therapy success. Therefore, understanding the mechanisms underlying resistance could improve therapy efficacy. Correlating expression levels in tissue samples of primary melanoma and metastases revealed that secretogranin 2 (SCG2) is highly expressed in advanced melanoma patients with poor overall survival (OS) rates. By conducting transcriptional analysis between SCG2-overexpressing (OE) and control melanoma cells, we detected a downregulation of components of the antigen presenting machinery (APM), which is important for the assembly of the MHC class I complex. Flow cytometry analysis revealed a downregulation of surface MHC class I expression on melanoma cells that showed resistance towards the cytotoxic activity of melanoma-specific T cells. IFNγ treatment partially reversed these effects. Based on our findings, we suggest that SCG2 might stimulate mechanisms of immune evasion and therefore be associated with resistance to checkpoint blockade and adoptive immunotherapy.

Recent clinical and preclinical advances have highlighted the existence of a previously hypothesized lymphogenous route of metastasis. However, due to a lack of suitable preclinical modeling tools, its contribution to long-term disease outcome and relevance for therapy remain controversial. Here, we established a genetically engineered mouse model (GEMM) fragment–based tumor model uniquely sustaining a functional network of intratumoral lymphatics that facilitates seeding of fatal peripheral metastases. Multiregimen survival studies and correlative patient data identified primary tumor–derived Angiopoietin-2 (Ang2) as a potent therapeutic target to restrict lymphogenous tumor cell dissemination. Mechanistically, tumor-associated lymphatic endothelial cells (EC), in contrast to blood vascular EC, were found to be critically addicted to the Angiopoietin–Tie pathway. Genetic manipulation experiments in combination with single-cell mapping revealed agonistically acting Ang2–Tie2 signaling as key regulator of lymphatic maintenance. Correspondingly, acute presurgical Ang2 neutralization was sufficient to prolong survival by regressing established intratumoral lymphatics, hence identifying a therapeutic regimen that warrants further clinical evaluation. Significance: Exploiting multiple mouse tumor models including a unique GEMM-derived allograft system in combination with preclinical therapy designs closely matching the human situation, this study provides fundamental insight into the biology of tumor-associated lymphatic EC and defines an innovative presurgical therapeutic window of migrastatic Ang2 neutralization to restrict lymphogenous metastasis. This article is highlighted in the In This Issue feature, p. 211

While for photon radiation hypofractionation has been reported to induce enhanced immunomodulatory effects, little is known about the immunomodulatory potential of carbon ion radiotherapy (CIRT). We thus compared the radio-immunogenic effects of photon and carbon ion irradiation on two murine cancer cell lines of different tumor entities. We first calculated the biological equivalent doses of carbon ions corresponding to photon doses of 1, 3, 5, and 10 Gy of the murine breast cancer cell line EO771 and the OVA-expressing pancreatic cancer cell line PDA30364/OVA by clonogenic survival assays. We compared the potential of photon and carbon ion radiation to induce cell cycle arrest, altered surface expression of immunomodulatory molecules and changes in the susceptibility of cancer cells to cytotoxic T cell (CTL) mediated killing. Irradiation induced a dose-dependent G2/M arrest in both cell lines irrespective from the irradiation source applied. Likewise, surface expression of the immunomodulatory molecules PD-L1, CD73, H2-Db and H2-Kb was increased in a dose-dependent manner. Both radiation modalities enhanced the susceptibility of tumor cells to CTL lysis, which was more pronounced in EO771/Luci/OVA cells than in PDA30364/OVA cells. Overall, compared to photon radiation, the effects of carbon ion radiation appeared to be enhanced at higher dose range for EO771 cells and extenuated at lower dose range for PDA30364/OVA cells. Our data show for the first time that equivalent doses of carbon ion and photon irradiation exert similar immunomodulating effects on the cell lines of both tumor entities, highlighted by an enhanced susceptibility to CTL mediated cytolysis in vitro.

The widespread application of immune-checkpoint blockade (ICB) has resulted in unprecedented response rates in patients with immunogenic cancers, such as melanoma and lung cancer. However, sub-groups of patients with these indications do not respond to ICB, and the same applies to patients with other cancer types. Mechanisms of resistance to ICB include low tumor immunogenicity associated with low T cell infiltration (‘cold’ tumors), suppression of anti-tumor immunity by immunosuppressive cells in the tumor microenvironment (TME), lack of antigen-presentation and immune escape (e.g. by downregulation of MHC-I on tumor cells) as well as oncologic pathways that suppress immune responses. Combination strategies, involving cytostatic drugs, harbor the potential to overcome refractoriness to immunotherapy. However, suppression of immune cell function by cytostatic drugs may limit the efficacy. In our study, we show that combination treatment of targeted inhibition of mitogen-activated protein kinase (MAPK) kinase (MEK) and agonist immunostimulatory anti-CD40 antibody (Ab) is particularly suitable in counteracting aforementioned ICB resistance mechanisms (Fig. 1).

Purpose: During our efforts to develop tumor-infiltrating lymphocyte (TIL) therapy to counter the devastating recurrence rate in patients with primary resectable pancreatic ductal adenocarcinoma (PDA), we found that PDA TILs can readily be expanded in vitro and that the majority of resulting TIL cultures show reactivity against the autologous tumor. However, the fraction of tumor-reactive T cells is low. We investigated to which extent this was related to the in vitro expansion. Experimental Design: We compared the clonal composition of TIL preparations before and after in vitro expansion using T-cell receptor (TCR) deep sequencing. Our findings for PDA were benchmarked to experiments with melanoma TILs. Results: We found that the TIL TCR repertoire changes dramatically during in vitro expansion, leading to loss of tumor- dominant T-cell clones and overgrowth by newly emerging T-cell clones that are barely detectable in the tumor. These changes are primarily driven by differences in the intrinsic in vitro expansion capacity of T-cell clones. Single-cell experiments showed an association between poor proliferative capacity and expression of markers related to antigen experience and dysfunction. Furthermore, we found that spatial heterogeneity of the TIL repertoire resulted in TCR repertoires that are greatly divergent between TIL cultures derived from distant tumor samples of the same patient. Conclusions: Culture-induced changes in clonal composition are likely to affect tumor reactivity of TIL preparations. TCR deep sequencing provides important insights into the factors that govern the outcome of in vitro TIL expansion and thereby a path toward optimization of the production of TIL preparations with high therapeutic efficacy. See related commentary by Lozano-Rabella and Gros, p. 4177

Cancer types with lower mutational load and a non-permissive tumor microenvironment are intrinsically resistant to immune checkpoint blockade. While the combination of cytostatic drugs and immunostimulatory antibodies constitutes an attractive concept for overcoming this refractoriness, suppression of immune cell function by cytostatic drugs may limit therapeutic efficacy. Here we show that targeted inhibition of mitogen-activated protein kinase (MAPK) kinase (MEK) does not impair dendritic cell-mediated T cell priming and activation. Accordingly, combining MEK inhibitors (MEKi) with agonist antibodies (Abs) targeting the immunostimulatory CD40 receptor results in potent synergistic antitumor efficacy. Detailed analysis of the mechanism of action of MEKi shows that this drug exerts multiple pro-immunogenic effects, including the suppression of M2-type macrophages, myeloid derived suppressor cells and T-regulatory cells. The combination of MEK inhibition with agonist anti-CD40 Ab is therefore a promising therapeutic concept, especially for the treatment of mutant Kras-driven tumors such as pancreatic ductal adenocarcinoma., Immune checkpoint inhibitors have limited efficacy in tumors with lower mutational burden and non-permissive microenvironment. Here, the authors show that combining MEK inhibition with an agonist anti-CD40 immunostimulatory antibody improves antitumor treatment by inducing immunogenic changes in the tumor microenvironment.

N6-methyladenosine (m6A) has an important epitranscriptomic modification that controls cancer self-renewal and cell fate. The addition of m6A to mRNA is a reversible modification. The deposition of m6A is encoded by a methyltransferase complex involving three homologous factors, jargonized as "writers," "erasers," and "readers." However, their roles in pancreatic adenocarcinoma (PAAD) are underexploited. With the use of The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases, we provided an mRNA signature that may improve the prognostic prediction of PAAD patients based on the genetic status of m6A regulators. PAAD patients with genetic alteration of m6A regulators had worse disease-free and overall survival. After comparing PAAD groups with/without genetic alteration of m6A regulators, we identified 196 differentially expressed genes (DEGs). Then, we generated a 16-mRNA signature score system through least absolute shrinkage and selection operator (LASSO) Cox regression analysis. Multivariate cox regression analysis demonstrated that a high-risk score significantly correlates with poor prognosis. Moreover, time-dependent receiver operating characteristic (ROC) curves revealed it was effective in predicting the overall survival in both training and validation sets. PAH, ZPLD1, PPFIA3, and TNNT1 from our signature also exhibited an independent prognostic value. Collectively, these findings can improve the understanding of m6A modifications in PAAD and potentially guide therapies in PAAD patients.

M2 macrophages promote tumor progression and therapy resistance, whereas proimmunogenic M1 macrophages can contribute to the efficacy of cytostatic and immunotherapeutic strategies. The abundance of M2 macrophages in the immune infiltrate of many cancer types has prompted the search for strategies to target and eliminate this subset. From our prior experiments in syngeneic mouse tumor models, we learned that pharmacological inhibition of mitogen-activated protein kinase kinase (MEK) did not merely result in tumor cell death, but also in the modulation of the tumor immune infiltrate. This included a prominent decrease in the numbers of macrophages as well as an increase in the M1/M2 macrophage ratio. Investigation of the mechanism underlying this finding in primary murine macrophage cultures revealed that M2 macrophages are significantly more sensitive to MEK inhibition-induced cell death than their M1 counterparts. Further analyses showed that the p38 MAPK pathway, which is activated in M1 macrophages only, renders these cells resistant to death by MEK inhibition. In conclusion, the dependency of M2 macrophages on the MEK/extracellular-signal regulated kinase (ERK) pathway empowers MEK inhibitors to selectively eliminate this subset from the tumor microenvironment.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor entity with dismal prognosis. PDAC is characterized by an extensive desmoplastic stroma and the tumor microenvironment (TME) has been recognized to play crucial roles in tumor development, therapy resistance, progression and metastasis. Although different cell types of the TME have been molecularly analyzed, tumor-infiltrating neurons could not be considered so far, because their cell bodies are located in adjacent ganglia of the peripheral nervous system and thus they are not part of the tumor mass (Demir, Thiel et al, Nature Cancer 2020; Demir, Thiel et al. Cancer Cell 2020). One of the unique features of PDAC is the strong infiltration by nerve fibers which correlates directly with tumor malignancy. In recent years it has been shown that either neurotransmitters secreted by neurons, or modulators of neuronal infiltration secreted by cancer cells can influence tumor growth. Here we use 3D light sheet fluorescence microscopy imaging (LSFM) of full tissue cleared PDAC specimen of tumors growing in genetically engineered mouse models or patient-derived xenograft models. Our data showthat these PDACs are innervated by a complex array of sensory and sympathetic neurons. To molecularly analyse neurons innervating the tumor mass, we have developed a novel approach we termed Trace’n’seq. This combines retrograde axonal tracing and FACS analysis with single cell RNA sequencing with the aim to identify, isolate and analyse hundreds of traced neurons infiltrating tumors or their respective healthy organs. Thereby, we have identified previously undescribed neuronal cell types and provide a landscape of sympathetic and sensory nerves innervating the healthy pancreas as well as PDAC. Our single cell transcriptomic analysis revealed signs of reprogramming of neuronal behaviour orchestrated by the tumor cells. These datasets combined with single cell profiling of PDAC cells and its associated stroma provide a first complete, unbiased insight into neurons infiltrating both healthy pancreas and PDAC. Based on a comprehensive interactome analysis of the interplay between tumor cells, stroma and the neurons, we have identified various candidate genes involved in tumor-nerve signalling. We are currently performing gain-and loss- of function approaches to dissect the role of individual factors. In summary, with Trace'n'seq, we have developed a novel technology pipeline to isolate tissue innervating neurons to investigate the role of neuronal infiltration in the development and progression of PDAC. Citation Format: Vera Thiel, Simon Renders, Jasper Panten, Julian Mochayedi, Rienk Offringa, Martin Sprick, Andreas Trumpp. Trace'n'Seq: Assessing neuronal infiltration and its impact in pancreatic ductal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3650.

BackgroundCancer immunotherapeutic strategies showed unprecedented results in the clinic. However, many patients do not respond to immuno-oncological treatments due to the occurrence of a plethora of immunological obstacles, including tumor intrinsic mechanisms of resistance to cytotoxic T-cell (TC) attack. Thus, a deeper understanding of these mechanisms is needed to develop successful immunotherapies.MethodsTo identify novel genes that protect tumor cells from effective TC-mediated cytotoxicity, we performed a genetic screening in pancreatic cancer cells challenged with tumor-infiltrating lymphocytes and antigen-specific TCs.ResultsThe screening revealed 108 potential genes that protected tumor cells from TC attack. Among them, salt-inducible kinase 3 (SIK3) was one of the strongest hits identified in the screening. Both genetic and pharmacological inhibitions of SIK3 in tumor cells dramatically increased TC-mediated cytotoxicity in several in vitro coculture models, using different sources of tumor and TCs. Consistently, adoptive TC transfer of TILs led to tumor growth inhibition of SIK3-depleted cancer cells in vivo. Mechanistic analysis revealed that SIK3 rendered tumor cells susceptible to tumor necrosis factor (TNF) secreted by tumor-activated TCs. SIK3 promoted nuclear factor kappa B (NF-κB)nuclear translocation and inhibited caspase-8 and caspase-9 after TNF stimulation. Chromatin accessibility and transcriptome analyses showed that SIK3 knockdown profoundly impaired the expression of prosurvival genes under the TNF–NF-κBaxis. TNF stimulation led to SIK3-dependent phosphorylation of the NF-κB upstream regulators inhibitory-κB kinase and NF-kappa-B inhibitor alpha on the one side, and to inhibition of histone deacetylase 4 on the other side, thus sustaining NF-κB activation and nuclear stabilization. A SIK3-dependent gene signature of TNF-mediated NF-κB activation was found in a majority of pancreatic cancers where it correlated with increased cytotoxic TC activity and poor prognosis.ConclusionOur data reveal an abundant molecular mechanism that protects tumor cells from cytotoxic TC attack and demonstrate that pharmacological inhibition of this pathway is feasible.

Immune checkpoint blockade using antibodies targeting the cell surface expressed proteins CTLA-4, PD-1 and PD-L1 has revolutionized cancer care and its clinical impact in several indications has prompted a search for complementary immunostimulatory approaches that can further increase the efficacy of these drugs. Mitogen-activated protein kinase kinase kinase kinase 1 (MAP4K1; HPK1), a serine/threonine kinase expressed exclusively in hematopoietic cell lineages, mediates a negative feedback signal downstream of T-cell receptor stimulation. Its activity is enhanced by PGE2 and TGFβ, factors commonly present in the tumor microenvironment. Mice deficient for MAP4K1 or expressing a kinase-dead variant of MAP4K1 exhibit enhanced T-cell function, including increased anti-tumor immunity. We developed the small molecule inhibitor BAY-405 that displays potent nanomolar MAP4K1 inhibition in biochemical and cellular assays, good kinase selectivity, and in vivo exposure after oral dosing. Pharmacological inhibition of MAP4K1 enhances T-cell immunity and overcomes the suppressive impact of PGE2, TGFβ and CD4+ T-regulatory cells. Single agent treatment of tumor-bearing mice results in suppression of tumor outgrowth in several syngeneic models. This is accompanied by an increase in the anti-tumor T-cell response, dependent on an intact T-cell compartment, while not involving direct anti-tumor cytotoxicity. Inhibition of MAP4K1 in conjunction with PD-L1 blockade results in further suppression of tumor outgrowth. Moreover, we found that MAP4K1 is expressed in both PD-L1-high and PD-L1-low human cancers. In summary, our data show that selective inhibition of MAP4K1 by means of small molecule drugs may be used to expand the patient population responding to immune checkpoint inhibition. Citation Format: Gabriele Leder, Rafael Carretero, Jeffrey Mowat, Sandra Berndt, Roland Neuhaus, Nuria Aiguabella Font, Ulf Boemer, Oliver von Ahsen, Uwe Eberspaecher, Judith Guenther, Mareike Grees, Corinna Link, Barbara Nicke, Daniel Baumann, Martina Schaefer, Mine Oezcan-Wahlbrink, Nicolas D. Werbeck, Ingo Hartung, Bertolt Kreft, Rienk Offringa. Enhancement of anti-tumor T-cell immunity by means of an oral small molecule targeting the intracellular immune checkpoint MAP4K1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1722.

Tumor-infiltrating lymphocytes (TIL) are considered enriched for T cells recognizing shared tumor antigens or mutation-derived neoepitopes. We performed exome sequencing and HLA-A*02:01 epitope prediction from tumor cell lines from two HLA-A2-positive melanoma patients whose TIL displayed strong tumor reactivity. The potential neoepitopes were screened for recognition using autologous TIL by immunological assays and presentation on tumor major histocompatibility complex class I (MHC-I) molecules by Poisson detection mass spectrometry (MS). TIL from the patients recognized 5/181 and 3/49 of the predicted neoepitopes, respectively. MS screening detected 3/181 neoepitopes on tumor MHC-I from the first patient but only one was also among those recognized by TIL. Consequently, TIL enriched for neoepitope specificity failed to recognize tumor cells, despite being activated by peptides. For the second patient, only after IFN-gamma treatment of the tumor cells was one of 49 predicted neoepitopes detected by MS, and this coincided with recognition by TIL sorted for the same specificity. Importantly, specific T cells could be expanded from patient and donor peripheral blood mononuclear cells (PBMC) for all neoepitopes recognized by TIL and/or detected on tumor MHC-I. In summary, stimulating the appropriate inflammatory environment within tumors may promote neoepitope MHC presentation while expanding T cells in blood may circumvent lack of specific TIL. The discordance in detection between physical and functional methods revealed here can be rationalized and used to improve neoantigen-targeted T cell immunotherapy.

Pancreatic ductal adenocarcinoma (PDA) is highlighted by resistance to radiotherapy with the possible exception of hypofractionated irradiation. As single photon doses were reported to increase immunogenicity, we investigated dose-dependent irradiation effects on clonogenic survival, expression of immunologically relevant cell surface molecules and susceptibility to cytotoxic T cell (CTL) mediated killing using a murine PDA cell line. Clonogenicity decreased in a dose-responsive manner showing enhanced radioresistance at single photon doses below 5 Gy. Cell cycle analysis revealed a predominant G2/M arrest, being most pronounced 12 h after irradiation. Polyploidy increased in a dose- and time-dependent manner reaching a maximum frequency 60 h following irradiation with 10 Gy. Irradiation increased surface expression of MHC class I molecules and of immunological checkpoint molecules PDL-1 and CD73, especially at doses ≥ 5 Gy, but not of MHC class II molecules and CXCR4 receptors. Cytotoxicity assays revealed increased CTL lysis of PDA cells at doses ≥ 5 Gy. For the PDA cell line investigated, our data show for the first time that single photon doses ≥ 5 Gy effectively inhibit colony formation and induce a G2/M cell cycle arrest. Furthermore, expression levels of immunomodulatory cell surface molecules became altered possibly enhancing the susceptibility of tumour cells to CTL lysis.

Anti-tumor immunity is limited by a number of factors including the lack of fully activated T-cells, insufficient antigenic stimulation and the immune-suppressive tumor microenvironment. We addressed these hurdles by developing a novel class of immunoconjugates, Antibody-Targeted Pathogen-derived Peptides (ATPPs), which were designed to efficiently deliver viral T-cell epitopes to tumors with the aim of redirecting virus-specific memory T-cells against the tumor. ATPPs were generated through covalent binding of mature MHC class I peptides to antibodies specific for cell surface-expressed tumor antigens that mediate immunoconjugate internalization. By means of a cleavable linker, the peptides are released in the endosomal compartment, from which they are loaded into MHC class I without the need for further processing. Pulsing of tumor cells with ATPPs was found to sensitize these for recognition by virus-specific CD8+ T-cells with much greater efficiency than exogenous loading with free peptides. Systemic injection of ATPPs into tumor-bearing mice enhanced the recruitment of virus-specific T-cells into the tumor and, when combined with immune checkpoint blockade, suppressed tumor growth. Our data thereby demonstrate the potential of ATPPs as a means of kick-starting the immune response against ‘cold’ tumors and increasing the efficacy of checkpoint inhibitors.

Despite melanoma immunogenicity and remarkable therapeutic effects of negative immune checkpoint inhibitors, a significant fraction of patients does not respond to current treatments. This could be due to limitations in tumor immunogenicity and profound immunosuppression in the melanoma microenvironment. Moreover, insufficient tumor antigen processing and presentation by dendritic cells (DC) may hamper the development of tumor-specific T cells. Using two genetically engineered mouse melanoma models (RET and BRAF(V600E) transgenic mice), in which checkpoint inhibitor therapy alone is not efficacious, we performed proof-of-concept studies with an improved, multivalent DC vaccination strategy based on our recently developed genetic mRNA cancer vaccines. The in vivo expression of multiple chimeric MHC class I receptors allows a simultaneous presentation of several melanoma-associated shared antigens tyrosinase related protein (TRP)-1, tyrosinase, human glycoprotein 100 and TRP-2. The DC vaccine induced a significantly improved survival in both transgenic mouse models. Vaccinated melanoma-bearing mice displayed an increased CD8 T cell reactivity indicated by a higher IFN-γ production and an upregulation of activation marker expression along with an attenuated immunosuppressive pattern of myeloid-derived suppressor cells (MDSC) and regulatory T cells (Treg). The combination of DC vaccination with ultra-low doses of paclitaxel or anti-PD-1 antibodies resulted in further prolongation of mouse survival associated with a stronger reduction of MDSC and Treg immunosuppressive phenotype. Our data suggest that an improved multivalent DC vaccine based on shared tumor antigens induces potent anti-tumor effects and could be combined with checkpoint inhibitors or targeting immunosuppressive cells to further improve their therapeutic efficiency.

The success of T cell-based cancer immunotherapy is limited by tumor's resistance against killing by cytotoxic T lymphocytes (CTLs). Tumor-immune resistance is mediated by cell surface ligands that engage immune-inhibitory receptors on T cells. These ligands represent potent targets for therapeutic inhibition. So far, only few immune-suppressive ligands have been identified. We here describe a rapid high-throughput siRNA-based screening approach that allows a comprehensive identification of ligands on human cancer cells that inhibit CTL-mediated tumor cell killing. We exemplarily demonstrate that CCR9, which is expressed in many cancers, exerts strong immune-regulatory effects on T cell responses in multiple tumors. Unlike PDL1, which inhibits TCR signaling, CCR9 regulates STAT signaling in T cells, resulting in reduced T-helper-1 cytokine secretion and reduced cytotoxic capacity. Moreover, inhibition of CCR9 expression on tumor cells facilitated immunotherapy of human tumors by tumor-specific T cells in vivo. Taken together, this method allows a rapid and comprehensive determination of immune-modulatory genes in human tumors which, as an entity, represent the ‘immune modulatome’ of cancer.

CEACAM6 (CD66c) is a novel immune checkpoint regulator suppressing the activity of effector T cells against tumors. CEACAM6 is expressed on tumor cells of multiple malignancies e.g.adenocarcinomas of the lung, colon, pancreas and stomach. In these tumor types higher CEACAM6 expression is associated with advanced stages and a poor prognosis. In immunohistochemistry analyses on primary tumor tissue slides and tissue microarrays the tumor cell expression of CEACAM6 was found to be independent from that of programmed death ligand 1 (PD-L1). BAY 1834942 is a humanized monoclonal antibody selectively blocking CEACAM6-mediated suppression of human T cells. Because there is no rodent orthologue of CEACAM6, BAY 1834942 was fully characterized in in vitro studies as reported earlier (AACR 2018, abstract nr. 1771). Benchmarking and combination studies showed that CEACAM6-mediated inhibition of T cell activation is apparently non-redundant with the programmed death-receptor 1 (PD-1)/ PD-L1 axis. Combination experiments were performed in co-cultures of PD-1, T cell immunoglobulin and mucin domain 3 (TIM3) and CEACAM1 (CD66a) positive virus antigen-specific T cells and virus peptide-loaded CEACAM6-expressing tumor cells (HCC2935, HCT116-C6 cells). When BAY 1834942 was combined with antibody inhibitors of either PD-1 or PD-L1, we consistently observed enhanced secretion of proinflammatory cytokines by T cells in the presence of PD-L1 positive tumor cells (HCC2935). Unexpectedly, combination of BAY 1834942 with an anti-TIM3 antibody resulted in an even more pronounced, synergistic increase of cytokine secretion. The combined effect of CEACAM6 and TIM-3 blockade was confirmed using survivin peptide-specific T cells as alternative T cell source. In contrast, combination of BAY 1834942 with an anti-CEACAM1 function blocking antibody was not superior to anti-CEACAM1 treatment alone, which is in line with our hypothesis that CEACAM1 is the main T cell receptor for CEACAM6 in our functional assays. In summary, BAY 1834942 is a novel immune checkpoint inhibitor with monotherapy potential for the treatment of patients with CEACAM6-expressing cancers. The data shown here provide a rationale for examining its combination potential with immune checkpoint inhibitors targeting either PD-1, PD-L1 or TIM-3. BAY 1834942 is currently under investigation in Ph1 clinical trials (NCT03596372). Citation Format: Joerg Willuda, Hans-Henning Boehm, Jessica Pinkert, Mark Trautwein, Wolf-Dietrich Doecke, Oliver von Ahsen, Karl Ziegelbauer, Rienk Offringa, Bertolt Kreft, Philipp Beckhove. Increased T cell- activation resulting from the combination of the anti-CEACAM6 function-blocking antibody BAY 1834942 with checkpoint inhibitors targeting either PD-1/PD-L1 or TIM-3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-075.

Germline genetic variability might contribute, at least partially, to the survival of pancreatic ductal adenocarcinoma (PDAC) patients. Two recently performed genome-wide association studies (GWAS) on PDAC overall survival (OS) suggested (P < 10(-5)) the association between 30 genomic regions and PDAC OS. With the aim to highlight the true associations within these regions, we analyzed 44 single-nucleotide polymorphisms (SNPs) in the 30 candidate regions in 1722 PDAC patients within the PANcreatic Disease ReseArch (PANDoRA) consortium. We observed statistically significant associations for five of the selected regions. One association in the CTNNA2 gene on chromosome 2p12 [rs1567532, hazard ratio (HR) = 1.75, 95% confidence interval (CI) 1.19-2.58, P = 0.005 for homozygotes for the minor allele] and one in the last intron of the RUNX2 gene on chromosome 6p21 (rs12209785, HR = 0.88, 95% CI 0.80-0.98, P = 0.014 for heterozygotes) are of particular relevance. These loci do not coincide with those that showed the strongest associations in the previous GWAS. In silico analysis strongly suggested a possible mechanistic link between these two SNPs and pancreatic cancer survival. Functional studies are warranted to confirm the link between these genes (or other genes mapping in those regions) and PDAC prognosis in order to understand whether these variants may have the potential to impact treatment decisions and design of clinical trials.

SummaryAntibodies to cell-surface antigens trigger activatory Fcγ receptor (FcγR)-mediated retrograde signals in leukocytes to control immune effector functions. Here, we uncover an FcγR mechanism that drives antibody-dependent forward signaling in target cells. Agonistic antibodies to death receptor 5 (DR5) induce cancer-cell apoptosis and are in clinical trials; however, their mechanism of action in vivo is not fully defined. Interaction of the DR5-agonistic antibody drozitumab with leukocyte FcγRs promoted DR5-mediated tumor-cell apoptosis. Whereas the anti-CD20 antibody rituximab required activatory FcγRs for tumoricidal function, drozitumab was effective in the context of either activatory or inhibitory FcγRs. A CD40-agonistic antibody required similar FcγR interactions to stimulate nuclear factor-κB activity in B cells. Thus, FcγRs can drive antibody-mediated receptor signaling in target cells.

CEACAM6 (CD66c) was previously shown to act as a novel immune checkpoint regulator suppressing the activity of effector T cells against tumors (Witzens-Harig et al., Blood 2013). CEACAM6 is a GPI-linked protein that is strongly expressed at the tumor cell surface in multiple cancer indications such as non-small cell lung adenocarcinoma (NSCLC), colorectal carcinoma (CRC), gastric adenocarcinoma and pancreatic cancer. In general, elevated CEACAM6 expression is associated with advanced tumor stages and poor prognosis. In vitro experiments showed that engagement of T-cells with CEACAM6, either expressed on tumor cells or presented on beads, resulted in suppression of TCR-mediated T-cell activation and ZAP70 phosphorylation. Based on these findings, we hypothesized that antibodies targeting CEACAM6 may be employed to enhance T-cell responses against CEACAM6-expressing cancers. Here we report the generation and characterization of BAY 1834942, a humanized monoclonal antibody selectively blocking the inhibitory impact of CEACAM6 on human T cells. There is no rodent ortholog of CEACAM6 precluding in vivo efficacy studies. In tumor cell / T cell co-culture systems, BAY 1834942 increased secretion of T-cell cytokines and effector molecules (e.g. IFNγ, TNFα, IL-2, granzyme B) and resulted in improved tumor cell killing. The effects of BAY 1834942 were dose-dependent, only observed in the context of CEACAM6-expressing tumor cells and could be reproduced in experiments using tumor cell lines and T-cell preparations from different sources, including T cells derived from tumor infiltrating lymphocytes from pancreatic cancer. BAY 1834942 is cross-reactive with the cynomolgus CEACAM6 ortholog and was well-tolerated in monkey toxicology studies. In summary, BAY 1834942 is a novel checkpoint inhibitor with potential for the treatment of patients with CEACAM6 expressing cancers, both as single agent and in combination with other checkpoint inhibitors. First-in-man trials are expected to commence in 2018. Citation Format: Joerg Willuda, Mark Trautwein, Jessica Pinkert, Wolf-Dietrich Doecke, Hans-Henning Boehm, Florian Wessel, Yingzi Ge, Eva Maria Gutierrez, Joerg Weiske, Christoph Freiberg, Uwe Gritzan, Julian Glueck, Dieter Zopf, Sven Golfier, Oliver von Ahsen, Ruprecht Zierz, Sabine Wittemer-Rump, Heiner Apeler, Ziegelbauer Karl, Rienk Offringa, Bertolt Kreft, Beckhove Philipp. BAY 1834942 is an immunotherapeutic antibody blocking the novel immune checkpoint regulator CEACAM6 (CD66c) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1771.

Microsatellite instable (MSI) cancers express frameshift-mutated antigens, the C-terminal polypeptides of which are foreign to the immune system. Consequently, these antigens constitute a unique pool of tumor-specific antigens that can be exploited for patient diagnosis and selective, immune-mediated targeting of cancers. However, other than their sequence, very little is known about the characteristics of the majority of these proteins. We therefore developed a methodology for predicting their immunogenic behavior that is based on a gene-expression system, in which each of the proteins was fused to a short C-terminal polypeptide comprising two epitopes that can be readily detected by T-cells and antibodies, respectively. In this manner, accumulation of the antigens and processing of peptides derived thereof into MHC can be monitored systematically. The antigens, which accumulate in the cells in which they are synthesized, are of primary interest for cancer immunotherapy, because peptide epitopes derived thereof can be presented by dendritic cells in addition to the tumor cells themselves. As a result, these antigens constitute the best targets for a coordinated immune response by both CD8+ and CD4+ T-cells, which increases the likelihood that tumor-induced immunity would be detectable against these antigens in cancer patients, as well as the potential value of these antigens as components of anticancer vaccines. Our data indicate that, of 15 frameshift-mutated antigens examined in our study, 4 (TGFbetaR2-1, MARCKS-1, MARCKS-2 and CDX2-2) are of primary interest, and 4 additional antigens (TAF1B-1, PCNXL2-2, TCF7L2-2 and Baxalpha+1) are of moderate interest for further tumor immunological research.

Human papillomavirus (HPV)-induced malignancies are frequently infiltrated by lymphocytes. To comprehend the contribution of HPV-specific T cells in this anti-tumor response we developed a method that allowed the analysis of the presence and specificity of cervix-infiltrating and draining lymph node resident T cells in a group of 74 patients with cervical malignancies, 54 of which were induced by HPV16 or HPV18. We detected the presence of HPV16 or HPV18-specific T cells in at least 23 of the 54 HPV-16 or -18 positive patients, and not in the 20 controls. Detailed studies resulted in the identification of 17 novel CD4+ and CD8+ T cell epitopes and their HLA-restriction elements, and also revealed that the HPV-specific immune response was aimed at both E6 and E7 and showed no preferential recognition of immunodominant regions. Unexpectedly, the vast majority of the CD4+ T cell epitopes were presented in the context of the less abundantly expressed HLA-DQ and HLA-DP molecules. Since the identified T cell epitopes constitute physiological targets in the immune response to HPV16 and HPV18 positive tumors they will be valuable for detailed studies on the interactions between the tumor and the immune system. This is crucial for the optimization of cancer immunotherapy in patients with pre-existing tumor-immunity.

Despite intensive treatment, 70% of the ovarian cancer patients will develop recurrent disease, emphasizing the need for new approaches such as immunotherapy. A promising antigenic target for immunotherapy in ovarian cancer is the frequently overexpressed p53 protein. The aim of the study was to evaluate the nature and magnitude of the baseline anti-p53 immune response in ovarian cancer patients. P53-specific T cell responses were detected in both half of the ovarian cancer patients as in the group of control subjects, consisting of women with benign ovarian tumors and healthy controls. Importantly, while in the control group p53-specific immunity was detected among the CD45RA(+) naive subset of T cells only, the p53-specific T-cell responses in ovarian cancer patients were also present in the CD45RO(+) memory T-cell subset, suggesting that in the cancer patients sufficient amounts of cancer-derived p53 was presented to induce the formation of a p53-specific memory T-cell response. Further characterization of the p53-specific memory T-cell responses revealed that in addition to the type 1 cytokine IFN-gamma also the type 2 cytokines IL4 and IL-5, as well as the immunosuppressive cytokine IL-10 were produced. Notably, p53-specific T cells were not only detected in the peripheral blood, but also among tumor infiltrating lymphocytes and in tumor-draining lymph nodes. In conclusion, the existence of a weak mixed T-helper type 1 and 2 p53-specific T-cell repertoire supports the rationale of using p53 long peptides in vaccination strategies aiming at the induction of p53-specific Thl/ CTL immunity. (c) 2007 Wiley-Liss, Inc.

In a prospective study, we have examined the tumor-specific immune response in a group of 59 patients with human papillomavirus (HPV) 16-positive (HPV16+)–induced or HPV18+-induced cervical cancer. Local antitumor immunity was analyzed by the enumeration of tumor-infiltrating dendritic cells and CD4+, CD8+, and regulatory T cells as well as by calculation of the ratio of CD8+/CD4+ T cells and CD8+/regulatory T cells. Systemic tumor-specific immunity was assessed by determination of the HPV E6- and/or E7-specific T-cell response in the blood of these patients. Finally, these variables were evaluated with respect to known histopathologic prognostic variables, including the absence (LN−) or presence (LN+) of lymph node metastases. Stratification according to the lymph node status of patients revealed a significantly stronger CD8+ T-cell tumor infiltration, a higher CD8+/CD4+ T-cell ratio, and higher CD8+/regulatory T-cell ratio in the group of patients in which the tumor failed to metastasize to the tumor-draining lymph node. Subdivision according to the presence (IR+) or absence (IR−) of circulating HPV-specific T cells disclosed that the highest number of tumor-infiltrating CD8+ T cells was found in the group of LN− patients displaying a concomitant systemic tumor-specific immune response (LN−IR+). CD8+ T-cell infiltration in LN−IR− patients was comparable with that of LN+ patients. In cervical cancer, the absence of lymph node metastases is strongly associated with a better prognosis. Our data indicate that, especially in a subgroup of LN− patients, a strong and effective interaction between immune system and tumor exists. This subgroup of cervical cancer patients may have the best prognosis. [Cancer Res 2007;67(1):354–61]

Modulation of the immune response by established tumors may contribute to the limited success of therapeutic vaccination for the treatment of cancer compared with vaccination in a preventive setting. We analyzed the contribution of the CD4+ T-cell population to the induction or suppression of tumor-specific CD8+ T cells in a tumor model in which eradication of tumors crucially depends on CD8+ T cell–mediated immunity. Vaccine-mediated induction of protective antitumor immunity in the preventive setting (i.e., before tumor challenge) was CD4+ T cell dependent because depletion of this T-cell subset prevented CD8+ T-cell induction. In contrast, depletion of CD4+ cells in mice bearing established E1A+ tumors empowered the mice to raise strong CD8+ T-cell immunity capable of tumor eradication without the need for tumor-specific vaccination. Spontaneous eradication of tumors, which had initially grown out, was similarly observed in MHC class II–deficient mice, supporting the notion that the tumor-bearing mice harbor a class II MHC–restricted CD4+ T-cell subset capable of suppressing a tumor-specific CD8+ T-cell immune response. The deleterious effects of the presence of CD4+ T cells in tumor-bearing hosts could be overcome by CD40-triggering or injection of CpG. Together these results show that CD4+ T cells with a suppressive activity are rapidly induced following tumor development and that their suppressive effect can be overcome by agents that activate professional antigen-presenting cells. These observations are important for the development of immune interventions aiming at treatment of cancer.

The clinical significance of tumor-infiltrating dendritic cells has been reported in a variety of human solid tumors as shown by the correlations found between the presence of tumor-infiltrating dendritic cells and clinical prognosis. In this study, we evaluated whether there is an association between the presence and maturation status of tumor-infiltrating dendritic cells, T lymphocytes, and clinical course in 104 primary tumor samples of patients with colorectal cancer. Dendritic cells were identified with four different markers (S-100, HLA class II, CD208, and CD1a) in double immunohistochemistry, with laminin as second marker to support the exact localization. Tumor-infiltrating dendritic cells showed a distinct infiltration pattern based on their maturation status. CD1a-positive dendritic cells resided in the advancing tumor margins in relatively high numbers, whereas mature CD208-positive dendritic cells were sparsely present in the tumor epithelium but mainly distributed in the tumor stroma and advancing tumor margin. Furthermore, high infiltration of CD1a-positive dendritic cells in the tumor epithelium was significantly correlated to the infiltration of CD4 lymphocytes (P = 0.006). Patients with relatively high numbers of mature CD208-positive infiltrating dendritic cells in the tumor epithelium had a shorter overall survival (P = 0.004). In addition, patients with relatively high numbers of CD1a-positive dendritic cells in the advancing margin of the tumor had a shorter disease-free survival (P = 0.03). We found that tumor-infiltrating dendritic cells had preferential infiltration sites within a tumor, affected local tumor cell-immune cell interactions, and correlated to the clinical prognosis of colorectal cancer patients.

The majority of cervical cancers are caused by human papillomavirus type 16 (HPV16). Cervical cancer is associated with an ineffective host immune response against the HPV16 oncoproteins, characterized by the lack of the strong E6-specific T-helper type 1 (Th1) immunity that is generally present in healthy individuals, the presence of improperly polarized HPV16E6- and E7-specific CD4(+) T cells and increased numbers of regulatory T cells. Therefore, immunotherapeutic intervention is likely to require a modality that deletes the regulatory T cell component and enhances the HPV16-specific Type 1 T cell response. HLA-matched allogeneic stem cell transplantation may offer such a modality, because it involves the eradication of host immune cells and enables the transfer of donor derived tumor-specific T cells to the patient. As a first step in the development of such a treatment, we evaluated the success rate of a protocol for enrichment of HPV16E6-specific CD4(+) T cells from healthy donor PBMC on the basis of their IFNgamma secretion. After a short in vitro stimulation with overlapping 30 amino acid long HPV16E6 peptides, we enriched the IFNgamma secreting cells by magnetic cell sorting. The obtained polyclonal CD4(+) T cell populations recognized distinct epitopes within HPV16E6, as well as E6 protein, processed and presented by autologous professional antigen presenting cells. The described protocol proved successful in PBMC from more than half of the healthy adult blood donors. These HPV16E6-specific CD4(+) T cells may turn out to be an essential component of future adoptive T cell therapy for advanced cervical cancer, by orchestrating CTL dependent and independent tumoricidal mechanisms.

Cervical cancer is the possible outcome of genital infection with high-risk human papillomavirus (HPV) and is preceded by a phase of persistent HPV infection during which the host immune system fails to eliminate the virus. Fortunately, the majority of genital HPV infections are cleared before the development of (pre)malignant lesions. Analysis of CD4+ T-helper (Th) immunity against the E2, E6, and E7 antigens of HPV16 in healthy women revealed strong proliferative E2- and E6-specific responses associated with prominent IFN-γ and interleukin 5 secretion. This indicates that the naturally arising virus-induced immune response displays a mixed Th1/Th2 cytokine profile. Of all HPV16+ cervical cancer patients, approximately half failed to mount a detectable immune response against the HPV16-derived peptides. The other half of the patients showed impaired HPV16-specific proliferative responses, which generally lacked both IFN-γ and interleukin 5. This indicates that the HPV16-specific CD4+ T-cell response in cervical cancer patients is either absent or severely impaired, despite a relatively good immune status of the patients, as indicated by intact responses against recall antigens. It is highly conceivable that proper CD4+ T-cell help is important for launching an effective immune attack against HPV because infection of cervical epithelia by this virus is, at least initially, not accompanied by gross disturbance of this tissue and/or strong proinflammatory stimuli. Therefore, our observations concerning the lack of functional HPV16-specific CD4+ T-cell immunity in patients with cervical cancer offer a possible explanation for the development of this disease.

Purpose: The purpose is to study the immunogenicity of heterologous prime-boost human papillomavirus (HPV) oncogene vaccination in patients with anogenital intraepithelial neoplasia (AGIN). Experimental Design: Twenty-nine women with high-grade AGIN received three i.m. doses of TA-CIN (HPV-16 L2/E6/E7 protein) at four weekly intervals followed by a single dermal scarification of vaccinia HPV-16/18 E6/E7 and were followed up for 12 weeks. Immunity to HPV-16 was assessed by lymphoproliferation, IFN-γ enzyme-linked immunospot (ELISPOT), and ELISA. Results: The patient group significantly responded to TA-CIN and not to the control antigen HPV-6 L2/E7 at all postvaccination time points when compared with baseline responses (P ≤ 0.05). Ten of the patients showed at least a 3-fold increase in TA-CIN-specific proliferation at one or more time points after vaccination. Comparison of stimulation with HPV-16 E6- or E7-GST fusion proteins showed that proliferative responses were biased to HPV-16 E6. This bias was also seen by IFN-γ ELISPOT using overlapping peptides, with HPV-16 E6- or E7-specific T cells being detected in 9 and 2 patients, respectively. In addition, vaccination resulted in the induction of antibodies against the HPV-16 oncoproteins. Of the 6 clinical responders, 2 patients showed both a proliferative TA-CIN-specific response and an E6-specific IFN-γ response, whereas 3 other patients displayed E6-specific reactivity only. Stable disease was recorded in 19 patients, 8 of whom showed a concomitant TA-CIN-specific proliferative and/or E6-specific T-cell response. Of the 4 progressors, 2 failed to make a T-cell response and 2 responded by either proliferation or E6 ELISPOT alone. Conclusions: The prime-boost regimen is immunogenic in AGIN patients (humoral and cellular immunity), but there is no simple relationship between induction of systemic HPV-16-specific immunity and clinical outcome. Other factors that may play a role in the eradication of long-term established AGIN lesions need to be determined to identify the patient group that would benefit from immunotherapy with the vaccines used in this study.

Overexpression of p53 occurs in more than 50% of colorectal cancers. Therefore, p53 represents an attractive target antigen for immunotherapy. We assessed the safety of a canarypox virus encoding the human wild-type p53 gene given intravenously to end-stage colorectal cancer patients in a three-step dose escalation study aimed at inducing p53 immune responses. Patients with metastatic disease of p53-overexpressing colorectal cancers were vaccinated three times at 3-week intervals, each time with 10(6.5) CCID(50) (CCID(50)=cell culture infectious dose 50%; group 1, n=5), 10(7.0) CCID(50) (group 2, n=5) or 10(7.5) CCID(50) (group 3, n=6). Vital signs and the occurrence of adverse events were monitored and blood was analyzed for biochemical and hematological parameters as well as signs of auto-immune safety. In all, 16 patients were enrolled and 15 patients completed three vaccinations. No anaphylactic reaction or unwanted auto-immune reactions were observed. A total of 16 serious adverse events (SAEs) occurred: 10 in group 1, three in group 2 and three in group 3. All SAEs were tumor-related complications. There was no difference in the frequency of adverse events between the three groups, except for fever. Fever was the only vaccination-related adverse event consistently observed and was most frequent and outspoken in the group 3 patients. The majority was a grade 1 or 2 fever (93%) and grade 3 fever (7%) was observed in three patients of group 3. Some patients showed humoral and cellular responses against p53, following vaccinations. After having completed his initial treatment cycle, one patient (group 2) received a second treatment cycle of three doses of 10(7.5) CCID(50) and subsequently showed stable disease. All other patients showed progressive disease. We conclude that ALVAC-p53 can be administered intravenously to colorectal cancer patients without serious toxicity or pathological autoimmunity and can induce immune responses against p53.

Mutation and aberrant expression of the p53 tumour suppressor protein are the most frequent molecular alterations in human malignancy. Peptides derived from the p53 protein and presented by major histocompatibility complex molecules for T-cell recognition could serve as universal tumour-associated antigens for cancer immunotherapy. Because p53 normally functions as a ubiquitously expressed self-protein, controlling cell-cycle progression and apoptosis, it also represents a paradigm target molecule for tumour-reactive yet self-antigen-specific T cells. Tailoring p53-based cancer immunotherapy thus requires both interference with p53-specific self-tolerance and induction of the entire repertoire of p53-reactive T cells. Transferring selected T-cell receptor genes into human T cells offers a novel and appealing strategy to meet these requirements.

9570 Background: Tumor infiltrating lymphocytes (TIL) play a crucial role in the therapeutic impact of immune checkpoint blockers. Methods: We investigated metastases from 56 melanoma patients before and during treatment with immune checkpoint blockers (i) immunohistochemically, (ii) with TCR repertoire profiling and (iii) analysis of the transcriptome. The patients were treated with ipilimumab (n = 25) or pembrolizumab (n = 23) or ipilimumab/nivolumab (n = 7); half of them had a disease control, the other half progressed as best response to treatment. Results: In contrast to previous reports immunohistochemical analysis of the immune infiltrate revealed no significant difference in the number of CD8+ TILs in pretreatment samples of responders and non-responders. Instead, the number of CD4 + TILs including regulatory T cells (Treg) and the number of PD-1 + cells was higher in responders especially when receiving pembrolizumab. Samples taken at least 6 weeks after start of the immune checkpoint blocker showed a significant higher number of immune cells in responders through all T cell subsets (CD3,4,8,FoxP3, PD-1), B cells (CD20) as well as macrophages (CD68, CD163). TCR repertoire profiling by deep TCR sequencing demonstrated that responders develop a more diverse repertoire under treatment (p = 0.05). Pretreatment samples as well as the size of the top 10 TCR clones posttreatment did not differ significantly in responders and non-responders. By RNA sequencing no differential expression profiles between responders and non-responders was found pretreatment. Posttreatment samples expressed different genes compared to pretreatment samples in responders including MHC molecules, CDK2/4, Myc, TNF family members and different apoptosis-inducing genes. There was no differential gene expression in non-responders pre- and posttreatment. Conclusions: Pretreatment metastases from responders and non-responders do not differ much. With treatment responding patients have significant higher numbers of immune cells including T- and B- cells as well as macrophages and develop a more diverse TCR repertoire. RNA sequencing revealed a differential expression pre- versus posttreatment only in responding patients.

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive collagen-rich stroma. T cells that infiltrate pancreatic cancers frequently become trapped in the stroma and do not contact tumor cells. Here, we aimed to analyze how chemokines and extracellular matrix (ECM) collagen interact in mediating T-cell infiltration in PDAC. Experimental Design: T-cell distribution and ECM structure within tumors were analyzed. Chemokine concentrations in human PDAC were compared with the levels of immune cell infiltration. We assessed the influences of selected chemokines and collagen on directed and random T-cell movement using in vitro migration systems. Results: PDAC overproduced several T-cell-active chemokines, but their levels were not correlated with intratumoral T-cell infiltration. In the absence of collagen, directed migration of activated T cells was induced by chemokines. Interestingly, collagen itself promoted high migratory activity of T cells, but completely abolished chemokine-guided movement. This effect was not altered by a β1-integrin blocking antibody. Activated T cells actively migrated in low-density collagen matrices, but migration was inhibited in dense collagen. Accordingly, T cells were heterogeneously distributed in the pancreatic cancer stroma, with the majority residing in areas of low-density collagen far from tumor clusters. Conclusion: The excessive desmoplasia in PDAC promotes T-cell migration by contact guidance, which abrogates tumor cell–directed movement. Furthermore, dense collagen networks represent a physical barrier, additionally rearranging T-cell distribution to favor tumor stroma. These mechanisms are mainly responsible for intrastromal T-cell trapping in pancreatic cancer and may hinder the development of T-cell–based immunotherapies. Clin Cancer Res; 20(13); 3422–33. ©2014 AACR.

The human epithelial mucin MUC1 is over-expressed in more than 90% of carcinomas of the breast, ovary, and pancreas as well as in some other tumours, making it a potential target for tumour immunotherapy. We have identified several MUC1-derived peptides mapping outside the variable number tandem repeat region that comply with the peptide-binding motif for HLA-A*0201 and that become processed into stable major histocompatibility complex-peptide complexes as assessed by in vitro assays. In A2/K(b) transgenic mice, 3 peptides, namely MUC(79-87) (TLAPATEPA), MUC(167-175) (ALGSTAPPV) and MUC(264-272) (FLSFHISNL) elicit peptide-specific cytotoxic T lymphocyte (CTL) immunity, which protects these mice against a challenge with MUC1, A2/K(b)-expressing tumour cells. These peptides therefore represent naturally processed MUC1-derived CTL epitopes that could be used as components in peptide-based vaccines and for the analysis of anti-MUC1 CTL responses in A*0201-positive patients with MUC1-expressing tumours.

The tumor suppressor protein p53 is overexpressed in up to 50% of all human malignancies, both in solid tumors as well as hematological malignancies, and is therefore an attractive target for immunotherapy. We have recently shown that cytotoxic T lymphocytes (CTL), raised in p53 gene deficient (p53 -/-) mice and recognizing a murine wild-type (wt) p53 peptide, were able to eradicate a mutant p53-induced and overexpressing tumor in p53 +/+ nude mice. These CTL also prevented the outgrowth of a more aggressive p53-overexpressing tumor in immunocompetent C57BL/6 mice. Importantly, this occurred in the absence of demonstrable damage to normal tissue. Possibly due to the aggressive nature of the latter tumor, adoptive transfer of wtp53-specific CTL did not result in the eradication of established tumors, either in nude or immunocompetent mice. Therefore, we explored whether the cytotoxic drug cyclophosphamide (CY) could potentiate the therapeutic activity of wtp53-specific CTL. We show here that CY acts synergistically with adoptively transferred wtp53-specific CTL in controlling the growth of an aggressive mutant p53-induced and overexpressing tumor. Previously described mechanisms underlying the synergism between CY and immune T cells were evaluated, but were not found to be operational in this model.

Persistent infection of basal keratinocytes with high-risk human papillomavirus (hrHPV) may cause cancer. Keratinocytes are equipped with different pattern recognition receptors (PRRs) but hrHPV has developed ways to dampen their signals resulting in minimal inflammation and evasion of host immunity for sustained periods of time. To understand the mechanisms underlying hrHPV's capacity to evade immunity, we studied PRR signaling in non, newly, and persistently hrHPV-infected keratinocytes. We found that active infection with hrHPV hampered the relay of signals downstream of the PRRs to the nucleus, thereby affecting the production of type-I interferon and pro-inflammatory cytokines and chemokines. This suppression was shown to depend on hrHPV-induced expression of the cellular protein ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) in keratinocytes. UCHL1 accomplished this by inhibiting tumor necrosis factor receptor-associated factor 3 (TRAF3) K63 poly-ubiquitination which lead to lower levels of TRAF3 bound to TANK-binding kinase 1 and a reduced phosphorylation of interferon regulatory factor 3. Furthermore, UCHL1 mediated the degradation of the NF-kappa-B essential modulator with as result the suppression of p65 phosphorylation and canonical NF-κB signaling. We conclude that hrHPV exploits the cellular protein UCHL1 to evade host innate immunity by suppressing PRR-induced keratinocyte-mediated production of interferons, cytokines and chemokines, which normally results in the attraction and activation of an adaptive immune response. This identifies UCHL1 as a negative regulator of PRR-induced immune responses and consequently its virus-increased expression as a strategy for hrHPV to persist., Author Summary A persistent infection with high-risk human papillomavirus (hrHPV) may cause cancer. Whereas keratinocytes – the cells infected by hrHPV – are equipped with different receptors allowing them to recognize invading pathogens and to activate the immune system, hrHPV has developed ways to evade the host's immune response for sustained periods of time. We showed that hrHPV accomplishes this by interfering with the signaling of the pathogen receptors, thereby hampering the production of cytokines that are known to attract and activate the immune system. HrHPV accomplishes this by upregulating the expression of a cellular protein called ubiquitin carboxyl-terminal hydrolase L1 (UCHL1). This protein suppresses the activation of signals downstream of the pathogen receptor leading to reduced transcription factor activation and downstream gene expression, in particular that of type I interferon and pro-inflammatory cytokines. This lowers the attraction of immune cells and thereby the chance of hrHPV-infected cells to be recognized and eliminated and as such enables hrHPV to persist.

Tumor-specific cytotoxic T cells (CTLs) can play an important role against cancer as illustrated by the observation that adoptive transfer of tumor-specific CTLs can mediate potent anti-tumor effects. Although such CTLs can be detected at the tumor site, relatively little is known about the mechanisms by which they enter the tumor. In this study, the role of major histocompatibility complex (MHC) class 1 molecules on vascular endothelium in the tumor in entry of, and tumor eradication by, tumor-specific CTL was investigated. Two H-2Db-restricted CTL clones recognizing peptide VNIRNCCYI on human adenovirus type 5 early region 1-(Ad5E1)-induced tumors were used to test whether CTLs were able to cross the vascular endothelium lacking the restricting MHC molecule. One CTL clone recognizes peptide VNIRNCCYI in the context of both H-2Db and H-2Dbm14 molecules. The other CTL clone recognizes this peptide only in the context of H-2Db. Adoptive transfer of these CTLs leads to eradication of Ad5E 1-induced, H-2Db-expressing tumors in B6(H-2Db+) and Bm14(H-2Db-) nude mice. Our data show that presentation of tumor-derived peptides by MHC molecules on endothelial cells of blood vessels in a tumor do not play a major role in eradication of tumors by adoptively transferred CTL in combination with interleukin-2. Moreover, our data show that successful adoptive CTL immunotherapy is possible across allogeneic barriers, without inducing severe side effects, provided the tumor expresses the MHC class 1-peptide complex recognized by the CTLs.

BACKGROUND: Being one of the most treatment-resistant cancer types, pancreatic ductal adenocarcinoma (PDAC) is characterized by its ability to escape immune surveillance by developing many immunological obstacles. These include a plethora of mechanisms that either dampen immune cell functionality, or foster tumor cell resistance towards immune attack. Immunotherapeutic strategies, such as immune checkpoint blockade, have proven clinical success in many cancer entities, but showed little clinical benefit in PDAC patients, emphasizing the need to identify more key players that could radically improve immunotherapy. AIM: We aim to systematically identify the whole arsenal of tumor-associated immune modulators by performing a high-throughput RNAi screen and subsequently validate novel therapeutic targets, whose blockade could potentially enhance anti-tumor immune response in PDAC patients. METHODS: We generated a luciferase-expressing PANC-1 cell line and knocked down 2514 genes using a siRNA library. Our library includes G-protein coupled receptors, protein kinases and 1117 surface proteins. We co-cultured HLA-A201+ matched tumor infiltrating lymphocytes (TILs) derived from a PDAC patient with the transfected tumor cells. We then measured the remaining luciferase intensity of the tumor cells as an estimation of TIL-mediated cytotoxicity. In order to exclude genes whose knock-down affected cell viability per se, we cultivated tumor cells with the siRNA library in the absence of TILs. RESULTS: We identified 155 candidate genes whose knock-down enhances TIL-mediated killing more efficiently than PD-L1 down-regulation. 35% of these genes are surface molecules and are most likely to directly mediate tumor immune evasion. Beside novel undescribed genes, our list contains well characterized immune modulators, supporting the reliability of our approach. Of note 13 of our hits were also found in a related melanoma screen and might play a role in the regulation of immune surveillance of different tumor entities. Among our candidates, 4 hits were chosen for further validation. We confirmed the expression of our selected candidates in several tumor cell lines and assessed the siRNA on-target effect using several non-overlapping siRNA sequences targeting the same hit. Transfection of PANC-1 with different siRNA sequences showed knock-down of the target gene as assessed via qPCR. Additionally we observed increased T-cell mediated killing as measured via luciferase-based killing assay and Chromium release assay. CONCLUSION: We set up a robust and systematic method to unravel novel key players of pancreatic cancer immune surveillance. Further functional validation of our candidate genes will prove their potential to be used as relevant therapeutic targets in the clinic. Citation Format: Antonio Sorrentino, Ayse Nur Menevse, Tillmann Michels, Nisit Khandelwal, Marco Breinig, Isabel Poschke, Valentina Volpin, Sabrina Wagner, Rienk Offringa, Michael Boutros, Philipp Beckhove. RNAi discovery platform to identify novel genes that prevent immune surveillance in pancreatic ductal adenocarcinoma (PDAC). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2339.

Clinical trials with immune-checkpoint blockade antibodies have bolstered the importance of immune therapy as the standard of care for cancer patients, but it has also simultaneously highlighted the heterogeneity in patient responses to such treatment. These heterogeneities can be explained to a certain extent by the lack of tumor-specific expression of the targeted immune checkpoint molecules. But in many cases it can also be conceived that tumors either develop resistance to a targeted immune-checkpoint node by circumventing it or more than one player is involved in a concerted action to subvert the T cell response. In either scenario, we lack a holistic understanding of the putative genes in the tumor genome that could functionally suppress the immune response. To bridge this gap, we employed a high-throughput RNAi-mediated knockdown of upto 2800 genes (~50% associated with surface molecules) in MCF7 (breast), M579-A2 (melanoma) and PANC-1 (pancreatic) tumor cell lines and co-cultured them with either antigen-specific T cell clones or respective patient-derived and tumor-specific infiltrating lymphocytes (TILs) to assess the impact on anti-tumor immunity using a luciferase-based readout. Primary hit-list was further subjected to a secondary screen based on multi-cytokine profiling of the T cells. Our investigation revealed a few salient caveats of tumor-mediated immune suppression. Firstly, we discovered a family of orphan receptors, which were never attributed to the immune system before, to actively suppress the T cells in a manner comparable to the currently defined immune-checkpoint molecules, such as PD-L1. Secondly, the trans-versatility of these novel molecules across the tumor types was highly limited, with only 3-14 common molecules being involved in two or more tumor types. This leads us to our third observation that there exists a complex organ-specific orchestration of peripheral immune tolerance, which needs to be taken into account when devising immune-checkpoint blockade therapies. Amongst the key immunosuppressive candidate genes, CCR9 was validated to directly subvert T cell responses in melanoma, breast and pancreatic cancer in the in vitro and in vivo tumor models. Additionally we have verified TiMi1, an orphan G-protein coupled receptor, to mediate strong immunosuppression in melanoma and pancreatic cancer against the respective TILs. Knockdown of both CCR9 and TiMi1, either via siRNAs or shRNAs, in tumor cells significantly increased Th1 cytokine secretion by TILs along with elevated tumor lysis in vitro and in vivo xenotransplanted mouse models. Moreover, they both induce a highly immunosuppressive genetic signature in the encountering TILs. While TiMi1 appeared to modulate calcium-dependent signaling, CCR9 regulated STAT signaling in T cells leading to an immunosuppressed phenotype. Overall, these candidates represent attractive targets for cancer immunotherapy either through function blocking antibodies or small molecules. In conclusion, we here report an effective genetic screen strategy in multiple tumor types that has the potential to uncover novel modifiers of anti-tumor immunity. Extensively validated candidates from these screens are attractive targets for cancer immunotherapy that will allow us to further expand our limited arsenal of immune-checkpoint inhibitors, with the overall goal of increasing patient responses to such treatments. Citation Format: Nisit Khandelwal, Tillmann Michels, Marco Breinig, Antonio Sorrentino, Isabel Poschke, Rienk Offringa, Michal Lotem, Michael Boutros, Philipp Beckhove. Genetic knockdown screens across tumor types unravel a diverse tumor “immune-modulatome” landscape. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A070.

In contrast to the general belief that pancreatic ductal adenocarcinoma is a poorly immunogenic tumor, we found cumulative evidence for an adaptive immune response in this aggressive cancer type. Immunohistochemistry reveals prominent T-cell infiltrates in the majority (~ 70%) of tumor biopsies, and these tumor-infiltrating lymphocytes (TILs) can be isolated and expanded ex vivo with similar efficiency as those isolated from melanoma. Furthermore, comparison of the T-cell receptor repertoire between TIL and PBMC isolates from patients points at the selective expansion of T-cell subsets in the tumors. Finally, in ~ 50% of tumor specimen, T-cell infiltration is accompanied by the presence of tertiary lymphoid structures that comprise areas rich in CD3+ T-cells and CD208+ dendritic cells as well as areas rich in B-cells and follicular dendritic cells. Based on these findings, our current efforts aim at: - Evaluating neoadjuvant treatment with agonist immunostimulatory antibodies as a means to mobilize this pre-existing immune response in patients with primary resectable disease* - Analysis of the anti-tumor reactivity and antigen-specificity of TCR-species that are prominently enriched in the tumor as compared to PBMC. - Exploration of TIL therapy for treatment of recurrent disease. * Clinical trial in context of FP7 EU IACT program; Immunostimulatory Antibodies for Cancer Treatment Citation Format: Rienk Offringa, Isabel Poschke, Michael Volkmar, Oliver Strobel, Frank Bergmann, Niels Halama, Dirk Jäger, Ugur Sahin, Markus Büchler. Towards implementation of T-cell therapy in pancreatic cancer. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr IA46.

The primary function of B cells, critical components of the adaptive immune response, is to produce antibodies against foreign antigens, as well as to perform isotype class switching, which changes the heavy chain of an antibody so that it can interact with different repertoires of effector cells. CD40 is a member of the tumor necrosis factor superfamily of cell surface receptors that transmits survival signals to B cells. In contrast, in B cell cancers, stimulation of CD40 signaling results in a heterogeneous response in which cells can sometimes undergo cell death in response to treatment, depending on the system studied. We found an association between sensitivity to CD40 stimulation and mutation of the tumor suppressor p53 in a panel of non-Hodgkin's lymphoma cell lines. Consistent with p53's tumor suppressor role, we found that higher levels of intrinsic DNA damage and increased proliferation rates, as well as higher levels of BCL6, a transcriptional repressor proto-oncogene, were associated with sensitivity to CD40 stimulation. In addition, CD40 treatment-resistant cell lines were sensitized to CD40 stimulation after the introduction of DNA-damaging agents. Using gene expression analysis, we also showed that resistant cell lines exhibited a preexisting activated CD40 pathway and that an mRNA expression signature comprising CD40 target genes predicted sensitivity and resistance to CD40-activating agents in cell lines and mouse xenograft models. Finally, the gene signature predicted tumor shrinkage and progression-free survival in patients with diffuse large B cell lymphoma treated with dacetuzumab, a monoclonal antibody with partial CD40 agonist activity. These data show that CD40 pathway activation status may be useful in predicting the antitumor activity of CD40-stimulating therapeutic drugs.

Priming of naive CD8+ T cells by pathogens or vaccines generally involves their interaction with Ag-loaded dendritic cells (DCs) in the context of an inflamed lymph node. Lymph node activation fosters DC and T cell encounters and subsequently provides newly primed T cells with nurturing conditions. We dissected these two aspects by infusing in vitro primed CD8+ T cells into naive recipient mice harboring a single activated lymph node and comparing the fate of these T cells with those infused into control recipients. Brief (20 h) in vitro priming empowered the T cells to expand in vivo without further Ag stimulation. This primary response was not affected by the presence or absence of a nonspecifically activated lymph node. In contrast, in vivo antigenic challenge after contraction of the primary response resulted in significantly stronger secondary T cell responses in mice harboring activated lymph nodes, demonstrating that the availability of an activated lymph node supported the generation of T cell memory in an Ag-unrelated manner. The presence of an activated lymph node during the expansion and contraction phase of the primary response did not endow T cells with an instructional program for increased survival or secondary expansion, but primarily served to conserve increased numbers of T cells.

Immunogenicity of tumor-associated antigens (TAA) is often weak because many TAA are autoantigens for which the T-cell repertoire is sculpted by tolerance mechanisms. Substitutions at main anchor positions to increase the complementarity between the peptide and the MHC class I (MHC-I) binding cleft constitute a common procedure to improve binding capacity and immunogenicity of TAA. However, such alterations are tailored for each MHC-I allele and may recruit different CTL specificities through conformational changes in the targeted peptides. Comparative analysis of substituted melanoma-differentiation antigen gp100 in complex with H-2Db revealed that combined introduction of glycine and proline residues at the nonanchor positions 2 and 3, respectively, resulted in an agonistic altered peptide with dramatically enhanced binding affinity, stability, and immunogenicity of this TAA. Peptide vaccination using the p2Gp3P-altered peptide version of gp100 induced high frequencies of melanoma-specific CTL in the endogenous CD8+ repertoire. Crystal structure analysis of MHC/peptide complexes revealed that the conformation of the modified p2Gp3P-peptide was similar to the wild-type peptide, and indicated that this mimotope was stabilized through interactions between peptide residue p3P and the tyrosine residue Y159 that is conserved among most known MHC-I molecules throughout mammalian species. Our results may provide an alternative approach to enhance MHC stabilization capacity and immunogenicity of low-affinity peptides for induction of robust tumor-specific CTL. [Cancer Res 2009;69(19):7784–92]

Carcinoembryonic antigen (CEA) is intensively studied as a potential target for immunotherapy of colorectal cancers. Although overexpressed by tumors, CEA is also expressed in normal tissues, raising questions about the feasibility and safety of CEA-targeted immunotherapy. We investigated these issues in transgenic mice in which the expression of human CEA in normal tissues closely resembles that in man. Our data show that the T-cell response against CEA in these mice is blunted by both thymic and peripheral tolerance. Consequently, effective tumor targeting is only achieved by adoptive transfer of T cells from nontolerant donors in combination with interventions that eliminate peripheral immune regulatory mechanisms. However, such treatments can result in severe intestinal autoimmune pathology associated with weight loss and mortality. Interestingly, preconditioning of recipient mice by depletion of T-regulatory cells results in immune-mediated tumor control in the absence of toxicity. In this setting, CEA-specific T-cell responses are lower than those induced by toxic regimens and accompanied by additional T-cell responses against non-self antigen. These findings illustrate the importance of testing adoptive immunotherapies targeting self antigens such as CEA in preclinical in vivo models and show that the choice of immune intervention regimen critically determines the balance between therapeutic efficacy and toxicity. [Cancer Res 2008;68(20):8446–55]

Microsatellite repeats are frequently found to be mutated in microsatellite-instable colorectal tumours. This suggests that these mutations are important events during tumour development. We have observed frequent mutations in microsatellite-instable (MSI-H) tumours and cell lines of a conserved A14 repeat within the 3'-untranslated region of the interferon-gamma receptor 1 gene (IFNGR1). The repeat was mutated in 59% (41 of 70) of colon carcinomas and in all four MSI-H colon cancer cell lines tested. In-vitro analysis of these cell lines did not show a decreased responsiveness to standard IFNgamma concentrations when compared to microsatellite-stable colon cancer cell lines. A functional consequence of the frequently found microsatellite instability in IFNGR1 is therefore not evident.

We have tested the safety and feasibility of a synthetic long peptide-based HPV16-specific skin test to detect cellular immune responses to HPV16 E2, E6 and E7 in vivo. Women with cervical neoplasia (n = 11) and healthy individuals (n = 19) were intradermally challenged with 8 different pools of HPV16 E2, E6 and E7 peptides. The skin test was safe as the injections were perceived as mildly painful and no adverse events were observed. The majority of skin reactions appeared significantly earlier in HPV16+ patients (

Tumorigenesis is frequently associated with mutation and overexpression of p53, which makes it an attractive target antigen for T cell–mediated immunotherapy of cancer. However, the magnitude and breadth of the p53-specific T-cell repertoire may be restricted due to the ubiquitous expression of wild-type p53 in normal somatic tissues. In view of the importance of the CD4+ T-helper cell responses in effective antitumor immunity, we have analyzed and compared the p53-specific reactivity of this T cell subset in p53+/+ and p53−/− C57Bl/6 mice. This response was found to be directed against the same three immunodominant epitopes in both mouse types. Fine-specificity, magnitude, and avidity were not affected by self-tolerance. Immunization of p53−/− and p53+/+ mice with synthetic peptide vaccines comprising the identified epitopes induced equal levels of Th1 immunity. Our findings imply that the p53-specific CD4+ T-cell repertoire is not restricted by self-tolerance and is fully available for the targeting of cancer. [Cancer Res 2008;68(3):893–900]

Purpose: The study aims to evaluate the effect of a human papillomavirus type 16 (HPV16) E6 and E7 synthetic long peptides vaccine on the antigen-specific T-cell response in cervical cancer patients.Experimental Design: Patients with resected HPV16-positive cervical cancer were vaccinated with an overlapping set of long peptides comprising the sequences of the HPV16 E6 and E7 oncoproteins emulsified in Montanide ISA-51. HPV16-specific T-cell immune responses were analyzed by evaluating the magnitude, breadth, type, and polarization by proliferation assays, IFNγ-ELISPOT, and cytokine production and phenotyped by the T-cell markers CD4, CD8, CD25, and Foxp3.Results: Vaccine-induced T-cell responses against HPV16 E6 and E7 were detected in six of six and five of six patients, respectively. These responses were broad, involved both CD4+ and CD8+ T cells, and could be detected up to 12 months after the last vaccination. The vaccine-induced responses were dominated by effector type CD4+CD25+Foxp3− type 1 cytokine IFNγ-producing T cells but also included the expansion of T cells with a CD4+CD25+Foxp3+ phenotype.Conclusions: The HPV16 E6 and E7 synthetic long peptides vaccine is highly immunogenic, in that it increases the number and activity of HPV16-specific CD4+ and CD8+ T cells to a broad array of epitopes in all patients. The expansion of CD4+ and CD8+ tumor-specific T cells, both considered to be important in the antitumor response, indicates the immunotherapeutic potential of this vaccine. Notably, part of the vaccine-induced T cells display a CD4+CD25+Foxp3+ phenotype that is frequently associated with regulatory T-cell function, suggesting that strategies to disarm this subset of T cells should be considered as components of immunotherapeutic modalities against HPV-induced cancers.