Tumor-derived prostaglandin E2 programs cDC1 dysfunction to impair intratumoral orchestration of anti-cancer T cell responses

Type 1 conventional dendritic cells (cDC1s) are critical for anti-cancer immunity. Protective anti-cancer immunity is thought to require cDC1s to sustain T cell responses within tumors, but it is poorly understood how this function is regulated and whether its subversion contributes to immune evasion. Here, we show that tumor-derived prostaglandin E2 (PGE₂) programmed a dysfunctional state in intratumoral cDC1s, disabling their ability to locally orchestrate anti-cancer CD8⁺ T cell responses. Mechanistically, cAMP signaling downstream of the PGE₂-receptors EP2 and EP4 was responsible for the programming of cDC1 dysfunction, which depended on the loss of the transcription factor IRF8. Blockade of the PGE₂-EP2/EP4-cDC1 axis prevented cDC1 dysfunction in tumors, locally reinvigorated anti-cancer CD8⁺ T cell responses, and achieved cancer immune control. In human cDC1s, PGE₂-induced dysfunction is conserved and associated with poor cancer patient prognosis. Our findings reveal a cDC1-dependent intratumoral checkpoint for anti-cancer immunity that is targeted by PGE₂ for immune evasion.

Antigen shedding into the circulation contributes to tumor immune escape

Tumors employ various mechanisms to escape elimination by the immune system. In addition to the local induction of immunosuppressive cell types such as regulatory T cells or myeloid derived suppressor cells, tumor antigen shedding into the circulation may suppress antitumor CD8⁺ T-cell function via tolerogenic liver sinusoidal endothelial cells.

Age-Related Gliosis Promotes Central Nervous System Lymphoma through CCL19-Mediated Tumor Cell Retention

How lymphoma cells (LCs) invade the brain during the development of central nervous system lymphoma (CNSL) is unclear. We found that NF-κB-induced gliosis promotes CNSL in immunocompetent mice. Gliosis elevated cell-adhesion molecules, which increased LCs in the brain but was insufficient to induce CNSL. Astrocyte-derived CCL19 was required for gliosis-induced CNSL. Deleting CCL19 in mice or CCR7 from LCs abrogated CNSL development. Two-photon microscopy revealed LCs transiently entering normal brain parenchyma. Astrocytic CCL19 enhanced parenchymal CNS retention of LCs, thereby promoting CNSL formation. Aged, gliotic wild-type mice were more susceptible to forming CNSL than young wild-type mice, and astrocytic CCL19 was observed in both human gliosis and CNSL. Therefore, CCL19-CCR7 interactions may underlie an increased age-related risk for CNSL.

Myeloid-derived suppressor cells control B cell accumulation in the central nervous system during autoimmunity

Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) have been characterized in the context of malignancies. Here we show that PMN-MDSCs can restrain B cell accumulation during central nervous system (CNS) autoimmunity. Ly6G⁺ cells were recruited to the CNS during experimental autoimmune encephalomyelitis (EAE), interacted with B cells that produced the cytokines GM-CSF and interleukin-6 (IL-6), and acquired properties of PMN-MDSCs in the CNS in a manner dependent on the signal transducer STAT3. Depletion of Ly6G⁺ cells or dysfunction of Ly6G⁺ cells through conditional ablation of STAT3 led to the selective accumulation of GM-CSF-producing B cells in the CNS compartment, which in turn promoted an activated microglial phenotype and lack of recovery from EAE. The frequency of CD138⁺ B cells in the cerebrospinal fluid (CSF) of human subjects with multiple sclerosis was negatively correlated with the frequency of PMN-MDSCs in the CSF. Thus PMN-MDSCs might selectively control the accumulation and cytokine secretion of B cells in the inflamed CNS.

Targeting myeloid derived suppressor cells with all-trans retinoic acid is highly time-dependent in therapeutic tumor vaccination

Tumor immune escape is a critical problem which frequently accounts for the failure of therapeutic tumor vaccines. Among the most potent suppressors of tumor immunity are myeloid derived suppressor cells (MDSCs). MDSCs can be targeted by all-trans-retinoic-acid (atRA), which reduced their numbers and increased response rates in several vaccination studies. However, not much is known about the optimal administration interval between atRA and the vaccine as well as about its mode of action. Here we demonstrate in 2 different murine tumor models that mice unresponsive to a therapeutic vaccine harbored higher MDSC numbers than did responders. Application of atRA overcame MDSC-mediated immunosuppression and restored tumor control. Importantly, atRA was protective only when administered 3 d after vaccination (delayed treatment), whereas simultaneous administration even decreased the anti-tumor immune response and reduced survival. When analyzing the underlying mechanisms, we found that delayed, but not simultaneous atRA treatment with vaccination abrogated the suppressive capacity in monocytic MDSCs and instead caused them to upregulate MHC-class-II. Consistently, MDSCs from patients with colorectal carcinoma also failed to upregulate HLA-DR after ex vivo treatment with TLR-ligation. Overall, we demonstrate that atRA can convert non-responders to responders to vaccination by suppressing MDSCs function and not only by reducing their number. Moreover, we identify a novel, strictly time-dependent mode of action of atRA to be considered during immunotherapeutic protocols in the future.

Kupffer Cell-Derived Tnf Triggers Cholangiocellular Tumorigenesis through JNK due to Chronic Mitochondrial Dysfunction and ROS

Intrahepatic cholangiocarcinoma (ICC) is a highly malignant, heterogeneous cancer with poor treatment options. We found that mitochondrial dysfunction and oxidative stress trigger a niche favoring cholangiocellular overgrowth and tumorigenesis. Liver damage, reactive oxygen species (ROS) and paracrine tumor necrosis factor (Tnf) from Kupffer cells caused JNK-mediated cholangiocellular proliferation and oncogenic transformation. Anti-oxidant treatment, Kupffer cell depletion, Tnfr1 deletion, or JNK inhibition reduced cholangiocellular pre-neoplastic lesions. Liver-specific JNK1/2 deletion led to tumor reduction and enhanced survival in Akt/Notch- or p53/Kras-induced ICC models. In human ICC, high Tnf expression near ICC lesions, cholangiocellular JNK-phosphorylation, and ROS accumulation in surrounding hepatocytes are present. Thus, Kupffer cell-derived Tnf favors cholangiocellular proliferation/differentiation and carcinogenesis. Targeting the ROS/Tnf/JNK axis may provide opportunities for ICC therapy.

Checkpoint Inhibition in Head and Neck Cancer: Immune Therapeutic Options, Limitations, and Beyond

The immune system functions to defend the organism against infectious microorganisms but also against transformed cells. This key role of the immune system, in particular cancer-specific T cells, in eliminating cancer cells is compromised by various immune escape strategies employed by cancer cells and the cancer microenvironment. Here, we review the current knowledge about the immune escape mechanisms of cancer and the attempts to reconstitute cancer-specific immunity by using checkpoint inhibitors in head and neck squamous cell carcinoma. We discuss the different options of immune therapy based on a mechanistic understanding of the relevance of co-inhibitory signaling, regulatory T cells, and myeloid-derived suppressor cells. A thorough mechanistic understanding of cancer immune escape mechanisms and their presence in the individual patient is required in order to design effective multicomponent immune therapies in the future.

Impact of NKT Cells and LFA-1 on Liver Regeneration under Subseptic Conditions

Background

Activation of the immune system in terms of subseptic conditions during liver regeneration is of paramount clinical importance. However, little is known about molecular mechanisms and their mediators that control hepatocyte proliferation. We sought to determine the functional role of immune cells, especially NKT cells, in response to partial hepatectomy (PH), and to uncover the impact of the integrin lymphocyte function-associated antigen-1 (LFA-1) on liver regeneration in a subseptic setting.

Methods

Wild-type (WT) and LFA-1^-/- mice underwent a 2/3 PH and low-dose lipopolysaccharid (LPS) application. Hepatocyte proliferation, immune cell infiltration, and cytokine profile in the liver parenchyma were determined.

Results

Low-dose LPS application after PH results in a significant delay of liver regeneration between 48h and 72h, which is associated with a reduced number of CD3⁺ cells within the regenerating liver. In absence of LFA-1, an impaired regenerative capacity was observed under low-dose LPS application. Analysis of different leukocyte subpopulations showed less CD3⁺NK1.1⁺ NKT cells in the liver parenchyma of LFA-1^-/- mice after PH and LPS application compared to WT controls, while CD3^-NK1.1⁺ NK cells markedly increased. Concordantly with this observation, lower levels of NKT cell related cytokines IL-12 and IL-23 were expressed in the regenerating liver of LFA-1^-/- mice, while the expression of NK cell-associated CCL5 and IL-10 was increased compared to WT mice.

Conclusion

A subseptic situation negatively alters hepatocyte proliferation. Within this scenario, we suggest an important impact of NKT cells and postulate a critical function for LFA-1 during processes of liver regeneration.

Pancreatic Premalignant Lesions Secrete Tissue Inhibitor of Metalloproteinases-1, Which Activates Hepatic Stellate Cells Via CD63 Signaling to Create a Premetastatic Niche in the Liver

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) metastasizes to liver at early stages, making this disease highly lethal. Tissue inhibitor of metalloproteinases-1 (TIMP1) creates a metastasis-susceptible environment in the liver. We investigated the role of TIMP1 and its receptor CD63 in metastasis of early-stage pancreatic tumors using mice and human cell lines and tissue samples.

METHODS

We obtained liver and plasma samples from patients in Germany with chronic pancreatitis, pancreatic intra-epithelial neoplasia, or PDAC, as well as hepatic stellate cells (HSCs). We performed studies with Ptf1a⁺/Cre;Kras⁺/LSL-G12D;Trp53loxP/loxP (CPK) mice, Pdx-1⁺/Cre;Kras⁺/LSL-G12D;Trp53⁺/LSL-R172H (KPC) mice, and their respective healthy littermates as control, and Cd63^-/- mice with their wild-type littermates. KPC mice were bred with Timp1^-/- mice to produce KPCxTimp1^-/- mice. TIMP1 was overexpressed and CD63 was knocked down in mice using adenoviral vectors AdTIMP1 or AdshCD63, respectively. Hepatic susceptibility to metastases was determined after intravenous inoculation of syngeneic 9801L pancreas carcinoma cells. Pancreata and liver tissues were collected and analyzed by histology, immunohistochemical, immunoblot, enzyme-linked immunosorbent assay, and quantitative polymerase chain reaction analyses. We analyzed the effects of TIMP1 overexpression or knockdown and CD63 knockdown in transduced human primary HSCs and HSC cell lines.

RESULTS

Chronic pancreatitis, pancreatic intra-epithelial neoplasia, and PDAC tissues from patients expressed higher levels of TIMP1 protein than normal pancreas. The premalignant pancreatic lesions that developed in KPC and CPK mice expressed TIMP1 and secreted it into the circulation. In vitro and in vivo, TIMP1 activated human or mouse HSCs, which required interaction between TIMP1 and CD63 and signaling via phosphatidylinositol 3-kinase, but not TIMP1 protease inhibitor activity. This signaling pathway induced expression of endogenous TIMP1. TIMP1 knockdown in HSCs reduced their activation. Cultured TIMP1-activated human and mouse HSCs began to express stromal-derived factor-1, which induced neutrophil migration, a marker of the premetastatic niche. Mice with pancreatic intra-epithelial neoplasia-derived systemic increases in TIMP1 developed more liver metastases after injections of pancreatic cancer cells than mice without increased levels of TIMP1. This increase in formation of liver metastases from injected pancreatic cancer cells was not observed in TIMP1 or CD63 knockout mice.

CONCLUSIONS

Expression of TIMP1 is increased in chronic pancreatitis, pancreatic intra-epithelial neoplasia, and PDAC tissues from patients. TIMP1 signaling via CD63 leads to activation of HSCs, which create an environment in the liver that increases its susceptibility to pancreatic tumor cells. Strategies to block TIMP1 signaling via CD63 might be developed to prevent PDAC metastasis to the liver.

The induction of human myeloid derived suppressor cells through hepatic stellate cells is dose-dependently inhibited by the tyrosine kinase inhibitors nilotinib, dasatinib and sorafenib, but not sunitinib

Increased numbers of immunosuppressive myeloid derived suppressor cells (MDSCs) correlate with a poor prognosis in cancer patients. Tyrosine kinase inhibitors (TKIs) are used as standard therapy for the treatment of several neoplastic diseases. However, TKIs not only exert effects on the malignant cell clone itself but also affect immune cells. Here, we investigate the effect of TKIs on the induction of MDSCs that differentiate from mature human monocytes using a new in vitro model of MDSC induction through activated hepatic stellate cells (HSCs). We show that frequencies of monocytic CD14(+)HLA-DR(-/low) MDSCs derived from mature monocytes were significantly and dose-dependently reduced in the presence of dasatinib, nilotinib and sorafenib, whereas sunitinib had no effect. These regulatory effects were only observed when TKIs were present during the early induction phase of MDSCs through activated HSCs, whereas already differentiated MDSCs were not further influenced by TKIs. Neither the MAPK nor the NFκB pathway was modulated in MDSCs when any of the TKIs was applied. When functional analyses were performed, we found that myeloid cells treated with sorafenib, nilotinib or dasatinib, but not sunitinib, displayed decreased suppressive capacity with regard to CD8+ T cell proliferation. Our results indicate that sorafenib, nilotinib and dasatinib, but not sunitinib, decrease the HSC-mediated differentiation of monocytes into functional MDSCs. Therefore, treatment of cancer patients with these TKIs may in addition to having a direct effect on cancer cells also prevent the differentiation of monocytes into MDSCs and thereby differentially modulate the success of immunotherapeutic or other anti-cancer approaches.

Differential induction of Ly6G and Ly6C positive myeloid derived suppressor cells in chronic kidney and liver inflammation and fibrosis

CD11b⁺Gr1⁺ myeloid derived suppressor cells (MDSC) are known to be very potent suppressors of T cell immunity and can be further stratified into granulocytic MDSC and monocytic MDSC in mice based on expression of Ly6G or Ly6C, respectively. Here, using these markers and functional assays, we aimed to identify whether MDSC are induced during chronic inflammation leading to fibrosis in both kidney and liver and whether additional markers could more specifically identify these MDSC subsets. In an adenine-induced model of kidney inflammation/fibrosis suppressive Ly6G^pos MDSC were induced. The suppressive function within the Ly6G⁺ MDSC population was exclusively present in IFNγRβ expressing cells. In contrast, in chronic inflammation in the liver induced by bile duct ligation, suppressive capacity was exclusively present in the Ly6C^pos MDSC subset. Gene expression analyses confirmed the differential origins and regulation of those MDSC subsets. Additionally, depletion of MDSC in either kidney or liver fibrosis enhanced fibrosis markers, indicating a protective role for MDSC in organ fibrosis. Thus, our data demonstrate that during liver inflammation and kidney fibrosis MDSC with similar function arise bearing a distinct marker profile and arising from different cell populations.

The NTPase/helicase domain of hepatitis C virus nonstructural protein 3 inhibits protein kinase C independently of its NTPase activity

Helicase motif VI is a short arginine-rich motif within the NTPase/helicase domain of the non-structural protein 3 (NS3) of the hepatitis C virus (HCV). We previously demonstrated that it reduces the catalytic activity and intracellular shuttling of protein kinase C (PKC). Thus, NS3-mediated PKC inhibition may be involved in HCV-associated hepatocellular carcinoma (HCC). In this study, we expand on our earlier results, which were obtained in experiments with short fragments of NS3, to show for the first time that the catalytically active, longer C-terminal NTPase/helicase of NS3 acts as a potent PKC inhibitor in vitro. PKC inhibition assays with the NTPase-inactive mutant NS3h-D1316A revealed a mixed type kinetic inhibition pattern. A broad range of 11 PKC isotypes was tested and all of the PKC isotypes were inhibited with IC₅₀-values in the low micromolar range. These findings were confirmed for the wild-type NTPase/helicase domain in a non-radiometric PKC inhibition assay with ATP regeneration to rule out any effect of ATP hydrolysis caused by its NTPase activity. PKCα was inhibited with a micromolar IC₅₀ in this assay, which compares well with our result for NS3h-D1316A (IC₅₀ = 0.7 μM). In summary, these results confirm that catalytically active NS3 NTPase/helicase can act in an analogous manner to shorter NS3 fragments as a pseudosubstrate inhibitor of PKC.

Liver sinusoidal endothelial cells contribute to CD8 T cell tolerance toward circulating carcinoembryonic antigen in mice

Immunity against cancer is impeded by local mechanisms promoting development of tumor-specific T cell tolerance, such as regulatory T cells, myeloid-derived suppressor cells, or immunosuppressive factors in the tumor microenvironment. The release of soluble antigens, such as carcinoembryonic antigen (CEA) from colorectal carcinoma (CRC) cells, has been investigated for diagnostic purposes, but not for its immunological consequences. Here, we address the question of whether soluble CEA influences tumor-specific immunity. Mice were injected with soluble CEA protein, and CEA-specific CD8 T cells were analyzed for their phenotype and functionality by means of restimulation ex vivo or antitumor efficacy in vivo. We furthermore characterized the CD8 T cell population in peripheral blood mononuclear cell (PBMCs) from healthy donors and colorectal carcinoma patients. In mice, circulating CEA was preferentially taken up in a mannose receptor-dependent manner and cross-presented by liver sinusoidal endothelial cells, but not dendritic cells, to CD8 T cells. Such systemically circulating CEA promoted tolerization of CEA-specific CD8 T cells in the endogenous T cell repertoire through the coinhibitory molecule B7H1. These CD8 T cells were not deleted but were rendered nonresponsive to antigen-specific stimulation and failed to control growth of CEA-expressing tumor cells. These nonresponsive CD8 T cells were phenotypically similar to central memory T cells being CD44(high) CD62L(high) CD25(neg) . We found T cells with a similar phenotype in PBMCs of healthy donors and at increased frequency also in patients with colorectal carcinoma.

CONCLUSION

Our results provide evidence for the existence of an unrecognized tumor immune escape involving cross-presentation of systemically circulating tumor antigens that may influence immunotherapy of cancer.

Immunotherapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the third most common cause of cancer-related death worldwide and efficient treatment options are urgently needed. Based on its pathogenesis, in addition to a number of correlative studies, immunotherapy represents a potential therapeutic option for patients with HCC. However, tumors have also evolved numerous immune escape mechanisms, including the generation of cells with immune suppressor functions, such as Tregs and myeloid-derived suppressor cells. It has been shown that these suppressor cells mask tumor-specific immune responses in patients with HCC. Different immunotherapeutic approaches including peptide- and dendritic cell-based therapies have demonstrated promising results in patients with HCC. However, we propose that any of these immunotherapeutic approaches needs to be combined with a therapy specifically targeting suppressor cells in HCC.

Immune responses in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the third most common cause of cancer-related deaths worldwide and efficient treatment options are urgently needed. Based on its pathogenesis as well as a number of correlative studies, immunotherapy represents a potential therapeutic option for patients with HCC. However, tumors have also evolved numerous immune escape mechanisms, such as the generation of cells with immune suppressor functions, including regulatory T cells and myeloid-derived suppressor cells. It has been shown that these suppressor cells mask tumor-specific immune responses in patients with HCC. We propose that targeting suppressor cells either alone or in combination with conventional immunotherapy should be further evaluated in HCC patients.

Long-term results of Rehbein's procedure: a retrospective study in German-speaking countries

AIM

In contrast to other countries, no collective study of Rehbein's procedure in German-speaking nations has been performed. Therefore, our intention was, analogously to Goto and Ikeda's (10) Japanese study in 1984, Kleinhaus's (13) study on Swenson's procedure in 1979, Bourdelat's (2) French-Canadian investigation into Duhamel's technique in 1997 and Martuciello's (11) and Teitelbaum's (16) follow-up in the year 2000, to perform a follow-up study of Rehbein's technique of deep anterior resection.

METHODS

The data of 200 patients from 22 German-speaking centers in Switzerland, Austria and Germany were collected. These data were gathered by questionnaire and the children were followed up in the individual participating hospitals for at least 3.5 years after the procedure. The procedure was performed between 1993 and 1997, over a 5-year period. The questionnaire contained 74 items including anamnestic data, diagnostic postoperative treatment and reoperations.

RESULTS

Concerning the incidence of anastomotic leaks and resolving anastomotic strictures there was no significant difference between the results in our series and those of the collective analyses made by Hofmann von Kap-herr (7), Holschneider (9) and Sherman (18). In 6.6 % of the 191 patients an anastomotic leak and in 9.9 % a rectal stricture, which had to be dilated, was observed. Concerning late complications, 22.8 % of the children suffered from constipation, 4.3 % from encopresis, 10.6 % from enterocolitis and only 0.5 % from enuresis. The frequency of constipation diminishes over the years. A comparison of the different large series in the literature clearly shows that the incidence of constipation is higher after Rehbein's procedure and the frequency of urinary incontinence and encopresis higher following Swenson's, Soave's and Duhamel's techniques. The incidence of enterocolitis is less after Rehbein's procedure than after Swenson's, Soave's and Duhamel's techniques.

CONCLUSIONS

The different results in the literature are due to the individual experience of the author, the very different follow-up methods and the date of follow-up. Therefore, the different results are hard to compare with our study. Nevertheless, Rehbein's anterior resection still could be presented as an adequate and important method to treat Hirschsprung's disease.