292 Ex vivo profiling of PD-1 blockade using an organotypic tissue slice model in solid tumors

Background

Tumor explant models provide a powerful ex vivo tool to evaluate complex biological mechanisms in a controlled environment. Ex vivo models retain much of the original tumor biology, heterogeneity, and tumor microenvironment, and therefore provide a useful preclinical platform and functional approach to assess drug responses rapidly and directly.

Methods

To explore mechanisms of resistance to cancer immunotherapy, we established an organotypic tissue slice Air-Liquid Interface (ALI) ex vivo system utilizing surgical tumor specimens from patients to assess the impact of the clinically utilized anti-PD-1 antibody nivolumab (OPDIVO). In the present study, we built a real-world patient cohort comprised of six tumor types: non-small cell lung cancer, melanoma, pancreatic ductal adenocarcinoma, breast cancer, prostate cancer, and colorectal cancer. We assessed tissue morphology, histology, PD-L1 IHC (CPS and TPS), CD8 T cell topology, proliferation in the tumor and stromal compartments, and secretome profiling.

Results

Our tumor slice model highly recapitulated features of the original tumor, including tumor architecture, immune phenotypes, and the prognostic markers. To identify responses to aPD-1 treatment, we compared baseline values for the cultured tumor slices with values at different timepoints post treatment. Secretome profiling of tissue explant supernatants using a panel of 94 analytes, revealed alterations to cytokines produced in the tumor microenvironment in response to aPD-1 treatment. We found that soluble expression patterns were associated with T-cell patterns (inflamed, excluded and desert) and PD-L1 score (CPS and TPS) in tumor tissues. These cytokines mediate critical functions across the immune cell cycle. Ongoing efforts to characterize T cell activation, exhaustion, tumor intrinsic responses and microenvironment composition using Imaging Mass Cytometry will be presented.

Conclusions

In this study, we demonstrated the feasibility of using fresh, surgically resected human tumors to test aPD-1 responses in an ex vivo system. Further, this model system has the potential to drive discovery and translational efforts by evaluating mechanisms of resistance to cancer immunotherapy and evaluate new single agent or combination therapies in the ex vivo setting.

387 The utility of AI-powered spatial classification of intratumoral CD8+ immune-cell distribution in predicting overall survival in patients with melanoma as part of the checkMate 067 clinical trial

Background

Spatial patterns of CD8+ T cells in the tumor microenvironment are associated with clinical outcomes in patients with advanced solid tumors. However, attempts to quantify spatial topology are hindered by challenges in manual scoring, heterogeneous immune-cell infiltrates, and interpathologist variability. Artificial intelligence (AI)–powered analysis can quantify CD8 topology in a biologically meaningful, reproducible, and scalable way. Using an AI-driven algorithm, we retrospectively assessed CD8 topology as a biomarker of response to immunotherapy in patients with advanced melanoma.

Methods

We trained a random forest classifier to predict CD8 topology using parenchymal and stromal CD8+ immune-cell measurements derived from a deep-learning platform (PathAI, Boston, MA). For model validation, pathologists manually classified CD8 immunohistochemistry (C8/144B, Agilent, Santa Clara, CA) in melanoma samples into inflamed (CD8+ cells in tumor parenchyma), excluded (CD8+ cells restricted to stroma), and desert (deficient in CD8+ cells) patterns. We explored the association with overall survival (OS) in a subset of patients with previously untreated metastatic melanoma who received nivolumab + ipilimumab (NIVO+IPI, n=102) or NIVO alone (n=107) in the CheckMate 067 phase 3 trial. Retrospective analysis of baseline AI-defined CD8 topology was performed alone and combined with manually scored programmed death ligand 1 (PD-L1) expression on tumor cells.

Results

Classifier model predictions were concordant with manual scoring (determined by a consensus of pathologists) and non-inferior to the agreement between 2 pathologists, via Cohen’s kappa coefficient k=0.79 and k=0.65, respectively. No statistically meaningful differences in outcomes were observed between CD8-excluded and CD8-inflamed phenotypes within the PD-L1 ≥1% population. However, patients with PD-L1 <1%/CD8-excluded tumors exhibited longer median OS compared with those with PD-L1 <1%/CD8-inflamed (table 1). 38% (40/104) of PD-L1 <1% tumors were CD8-excluded. Within PD-L1 <1%, patients with an excluded phenotype also exhibited lower frequency of severe adverse events (grade ≥3) than patients with inflamed phenotype following treatment: NIVO+IPI, 75% (n=20) vs 91% (n=11); NIVO, 61% (n=18) vs 80% (n=15). Compared with PD-L1 status, the composite biomarker (AI-classified CD8-excluded plus PD-L1 ≥1%) identified a larger group of patients who had greater survival benefit with NIVO+IPI or NIVO alone (table 2).

Abstract 387 Table 1

Immunotherapy outcomes by CD8+ topology in PD-L1<1% melanoma

In a subset of patients with melanoma and tumor cell PD-L1 expression <1% in the CheckMate 067 clinical trial, those with a CD8-excluded phenotype demonstrated longer overall survival compared with those with a CD8-inflamed phenotype when treated with NIVO±IPI.

Abstract 387 Table 2

Composite biomarker outcomes in Checkmate 067

In patients with melanoma in the CheckMate 067 clinical trial, the composite biomarker (AI-classified CD8-excluded phenotype plus PD-L1 expression ≥1%) identified more biomarker-positive patients and demonstrated increased overall survival benefit vs PD-L1 status alone for patients treated with NIVO±IPI. Hazard ratios represent patients with a PD-L1 expression of ≥1% compared with PD-L1 <1% or patients with a PD-L1 expression of ≥1% and CD8-excluded phenotype compared with PD-L1 expression <1% and not CD8-excluded.

Conclusions

This study explores the utility of combining AI-powered CD8 topology classifications with PD-L1 expression as a composite biomarker associated with immunotherapy response. In patients with PD-L1 <1% melanoma, median OS with NIVO+IPI was significantly longer in patients with CD8-excluded tumors than with an inflamed phenotype. Further studies are underway to identify mechanisms underlying responses to NIVO+IPI.

Acknowledgements

We would like to thank the team at PathAI for development of the AI classifier, and Dako, an Agilent Technologies, Inc. company, for collaborative development of the PD-L1 IHC 28-8 pharmDx assay. Editorial support was provided by Emily Motola, PharmD, and Matthew Weddig of Spark Medica Inc.

Trial Registration

Clinicaltrials

gov number NCT01844505

Ethics Approval

The study protocol and all amendments were approved by local institutional review boards, and the protocol was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice Guidelines, as defined by the International Conference on Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. All patients provided written informed consent before enrollment.

The inhibitory receptor TIM-3 limits activation of the cGAS-STING pathway in intra-tumoral dendritic cells by suppressing extracellular DNA uptake

Blockade of the inhibitory receptor TIM-3 shows efficacy in cancer immunotherapy clinical trials. TIM-3 inhibits production of the chemokine CXCL9 by XCR1⁺ classical dendritic cells (cDC1), thereby limiting antitumor immunity in mammary carcinomas. We found that increased CXCL9 expression by splenic cDC1s upon TIM-3 blockade required type I interferons and extracellular DNA. Chemokine expression as well as combinatorial efficacy of TIM-3 blockade and paclitaxel chemotherapy were impaired by deletion of Cgas and Sting. TIM-3 blockade increased uptake of extracellular DNA by cDC1 through an endocytic process that resulted in cytoplasmic localization. DNA uptake and efficacy of TIM-3 blockade required DNA binding by HMGB1, while galectin-9-induced cell surface clustering of TIM-3 was necessary for its suppressive function. Human peripheral blood cDC1s also took up extracellular DNA upon TIM-3 blockade. Thus, TIM-3 regulates endocytosis of extracellular DNA and activation of the cytoplasmic DNA sensing cGAS-STING pathway in cDC1s, with implications for understanding the mechanisms underlying TIM-3 immunotherapy.

IgA transcytosis and antigen recognition govern ovarian cancer immunity

Most ovarian cancers are infiltrated by prognostically relevant activated T cells^1–3, yet exhibit low response rates to immune checkpoint inhibitors⁴. Memory B cell and plasma cell infiltrates have previously been associated with better outcomes in ovarian cancer^5,6, but the nature and functional relevance of these responses are controversial. Here, using 3 independent cohorts that in total comprise 534 patients with high-grade serous ovarian cancer, we show that robust, protective humoral responses are dominated by the production of polyclonal IgA, which binds to polymeric IgA receptors that are universally expressed on ovarian cancer cells. Notably, tumour B-cell-derived IgA redirects myeloid cells against extracellular oncogenic drivers, which causes tumour cell death. In addition, IgA transcytosis through malignant epithelial cells elicits transcriptional changes that antagonize the RAS pathway and sensitize tumour cells to cytolytic killing by T cells, which also contributes to hindering malignant progression. Thus, tumour-antigen-specific and -antigen-independent IgA responses antagonize the growth of ovarian cancer by governing coordinated tumour cell, T cell and B cell responses. These findings provide a platform for identifying targets that are spontaneously recognized by intratumoural B-cell-derived antibodies, and suggest that immunotherapies that augment B cell responses may be more effective than approaches that focus on T cells, particularly for malignancies that are resistant to checkpoint inhibitors.

In patients with high-grade serous ovarian cancer, robust and protective humoral responses are dominated by B-cell-derived polyclonal IgA that binds to polymeric IgA receptors that are universally expressed on ovarian cancer cells.

The Unfolded Protein Response Mediator PERK Governs Myeloid Cell-Driven Immunosuppression in Tumors through Inhibition of STING Signaling

The primary mechanisms supporting immunoregulatory polarization of myeloid cells upon infiltration into tumors remain largely unexplored. Elucidation of these signals could enable better strategies to restore protective anti-tumor immunity. Here, we investigated the role of the intrinsic activation of the PKR-like endoplasmic reticulum (ER) kinase (PERK) in the immunoinhibitory actions of tumor-associated myeloid-derived suppressor cells (tumor-MDSCs). PERK signaling increased in tumor-MDSCs, and its deletion transformed MDSCs into myeloid cells that activated CD8⁺ T cell-mediated immunity against cancer. Tumor-MDSCs lacking PERK exhibited disrupted NRF2-driven antioxidant capacity and impaired mitochondrial respiratory homeostasis. Moreover, reduced NRF2 signaling in PERK-deficient MDSCs elicited cytosolic mitochondrial DNA elevation and, consequently, STING-dependent expression of anti-tumor type I interferon. Reactivation of NRF2 signaling, conditional deletion of STING, or blockade of type I interferon receptor I restored the immunoinhibitory potential of PERK-ablated MDSCs. Our findings demonstrate the pivotal role of PERK in tumor-MDSC functionality and unveil strategies to reprogram immunosuppressive myelopoiesis in tumors to boost cancer immunotherapy.

Expression of cancer cell-associated Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) regulates protective anti-tumor immunity in melanoma

Activation of moderated endoplasmic reticulum (ER) stress in cancer cells promotes cellular adaptation and survival in response to the adverse conditions of the tumor microenvironment (TME). However, how modulation of ER stress in cancer cells culminates in the development of an immunosuppressive TME remains poorly understood and therapeutically unexploited. Upon disruption of ER homeostasis, mediator proteins IRE1a, ATF6 and PERK induce activation of the unfolded protein response (UPR). Although maladaptive priming of UPR mediators in immune cells deactivates their capacity for anti-tumor immunity, the immunosuppressive potential of UPR mediators in cancer cells, in particular PERK, remains unknown. Thus, in this study, we hypothesized that activation of PERK in tumor cells shapes the formation of the immunosuppressive TME and impairs the development of anti-tumor immunity. Elimination of PERK in cancer cells impaired survival upon chemically-induced ER stress and promoted caspase-independent cell death. Interestingly, in vivo ablation of PERK in melanoma impaired tumor growth, which surprisingly occurred in a T cell-dependent manner. Additionally we observed that ablation of PERK shifted the TME from an immunosuppressive to immunostimulatory environment, enhanced accumulation of effector T cells and directed reprogramming of myeloid derived suppressor cells (MDSCs) into immunostimulatory cells. Additional experiments indicated that ablation of PERK induced expression of mediators associated with immunogenic cell death. Collectively, our findings demonstrate the immunoregulatory role of PERK in tumor cells and highlight the therapeutic potential of targeting UPR mediators and tumor adaptive processes.

Polyphenol-rich extract induces apoptosis with immunogenic markers in melanoma cells through the ER stress-associated kinase PERK

Polyphenols elicit antitumor activities, in part, through the induction of anti- or pro-oxidant effects in cancer cells which promote priming of protective anti-tumor immunity. We recently characterized a polyphenol-rich extract from Caesalpinia spinosa (P2Et) that stimulates in vivo antitumor responses against breast and melanoma tumor models via the promotion of immunogenic cancer cell death (ICD). However, the primary mediators whereby P2Et promotes ICD remained unknown. Here, we sought to elucidate the role that severe endoplasmic reticulum (ER) stress plays in mediating P2Et-induced apoptosis and ICD in murine melanoma cells. Our findings demonstrate a substantial selective induction of specific ER-stress mediators in B16-F10 melanoma cells treated with P2Et. While knockout of the ER stress-associated PKR-like ER kinase (PERK) prevented induction of apoptosis and expression of ICD markers in P2Et-treated cells, deletion of X-box binding protein 1 (Xbp1) did not. P2Et-driven activation of PERK in melanoma cells was found to promote ER-calcium release, disrupt mitochondrial membrane potential, and trigger upregulation of ICD drivers, surface calreticulin expression, and extracellular release of ATP and HMGB1. Notably, calcium release inhibition, but not targeting of PERK-driven integrated stress responses, prevented P2Et-induced apoptosis. Collectively, these results underline the central role of PERK-directed calcium release in mediating the antitumor and immunogenic actions of P2Et in melanoma cells.

AMPK Alpha-1 Intrinsically Regulates the Function and Differentiation of Tumor Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSC) represent a primary mechanism of immune evasion in tumors and have emerged as a major obstacle for cancer immunotherapy. The immunoinhibitory activity of MDSC is tightly regulated by the tumor microenvironment and occurs through mechanistic mediators that remain unclear. Here, we elucidated the intrinsic interaction between the expression of AMP-activated protein kinase alpha (AMPKα) and the immunoregulatory activity of MDSC in tumors. AMPKα signaling was increased in tumor-MDSC from tumor-bearing mice and patients with ovarian cancer. Transcription of the Ampkα1-coding gene, Prkaa1, in tumor-MDSC was induced by cancer cell-derived granulocyte-monocyte colony-stimulating factor (GM-CSF) and occurred in a Stat5-dependent manner. Conditional deletion of Prkaa1 in myeloid cells, or therapeutic inhibition of Ampkα in tumor-bearing mice, delayed tumor growth, inhibited the immunosuppressive potential of MDSC, triggered antitumor CD8⁺ T-cell immunity, and boosted the efficacy of T-cell immunotherapy. Complementarily, therapeutic stimulation of AMPKα signaling intrinsically promoted MDSC immunoregulatory activity. In addition, Prkaa1 deletion antagonized the differentiation of monocytic-MDSC (M-MDSC) to macrophages and re-routed M-MDSC, but not granulocytic-MDSC (PMN-MDSC), into cells that elicited direct antitumor cytotoxic effects through nitric oxide synthase 2-mediated actions. Thus, our results demonstrate the primary role of AMPKα1 in the immunosuppressive effects induced by tumor-MDSC and support the therapeutic use of AMPK inhibitors to overcome MDSC-induced T-cell dysfunction in cancer. SIGNIFICANCE: AMPKα1 regulates the immunosuppressive activity and differentiation of tumor-MDSC, suggesting AMPK inhibition as a potential therapeutic strategy to restore protective myelopoiesis in cancer.

Differential expression of miRNA-146a and miRNA-155 in gastritis induced by Helicobacter pylori infection in paediatric patients, adults, and an animal model

Background

Helicobacter pylori is a major aetiologic agent associated with gastritis. H. pylori infections increase the expression of the Toll-like receptor (TLR), which in turn modulates the expression of microRNA (miRNA)-146a and miRNA-155. The objective of this study was to compare the expression of miRNA-146a and miRNA-155 in gastric lesions of paediatric and adult patients with different pathologies and in Mongolian gerbils (Meriones unguiculatus) infected with H. pylori 26,695.

Methods

Quantification of miRNA expression was performed by quantitative real-time polymerase chain reaction (qRT-PCR) of paraffin-embedded gastric lesions of children with or without an infection (n = 25), adults with follicular gastritis and metaplasia (n = 32) and eight-week-old M. unguiculatus males (Hsd:MON) infected with H. pylori 26,695 for 0, 3, 6, 12 and 18 months (n = 25). The genes RNU48 and RNU6 were used as endogenous controls for data normalization. Statistical analyses were performed using Kruskal-Wallis, Mann-Whitney, ANOVA and Student’s t-test.

Results

The expression of miRNA-146a and miRNA-155 in infected children increased by 247.6- and 79.4-fold (on average), respectively, compared to that observed in the control group. However, these results were not significant (p = 0.12 and p = 0.07 respectively). In some children a gradual increase in expression was observed, while in others, expression was very high. Additionally, the expression levels of miRNA-146a and miRNA-155 increased by an average of 21.7- and 62-fold, respectively, in adult patients with follicular gastritis when compared to those of the controls. In M. unguiculatus infected with H. pylori 26,695, the expression of both miRNAs increased as the infection progressed.

Conclusion

This is the first report to show differences in the expression of miRNA-146a and miRNA-155 in paediatric and adult patients with gastritis who were infected with H. pylori. In addition, in M. unguiculatus infected with H. pylori, miRNA expression was associated with the progression of infection and the ability of the bacteria to adapt to the host.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3368-2) contains supplementary material, which is available to authorized users.

Anti-Jagged Immunotherapy Inhibits MDSCs and Overcomes Tumor-Induced Tolerance

Myeloid-derived suppressor cells (MDSC) are a major obstacle to promising forms of cancer immunotherapy, but tools to broadly limit their immunoregulatory effects remain lacking. In this study, we assessed the therapeutic effect of the humanized anti-Jagged1/2-blocking antibody CTX014 on MDSC-mediated T-cell suppression in tumor-bearing mice. CTX014 decreased tumor growth, affected the accumulation and tolerogenic activity of MDSCs in tumors, and inhibited the expression of immunosuppressive factors arginase I and iNOS. Consequently, anti-Jagged therapy overcame tumor-induced T-cell tolerance, increased the infiltration of reactive CD8⁺ T cells into tumors, and enhanced the efficacy of T-cell-based immunotherapy. Depletion of MDSC-like cells restored tumor growth in mice treated with anti-Jagged, whereas coinjection of MDSC-like cells from anti-Jagged-treated mice with cancer cells delayed tumor growth. Jagged1/2 was induced in MDSCs by tumor-derived factors via NFkB-p65 signaling, and conditional deletion of NFkB-p65 blocked MDSC function. Collectively, our results offer a preclinical proof of concept for the use of anti-Jagged1/2 to reprogram MDSC-mediated T-cell suppression in tumors, with implications to broadly improve the efficacy of cancer therapy. Cancer Res; 77(20); 5628-38. ©2017 AACR.

Sildenafil Suppresses Inflammation-Driven Colorectal Cancer in Mice

Intestinal cyclic guanosine monophosphate (cGMP) signaling regulates epithelial homeostasis and has been implicated in the suppression of colitis and colon cancer. In this study, we investigated the cGMP-elevating ability of the phosphodiesterase-5 (PDE5) inhibitor sildenafil to prevent disease in the azoxymethane/dextran sulfate sodium (AOM/DSS) inflammation-driven colorectal cancer model. Treatment of mice with sildenafil activated cGMP signaling in the colon mucosa and protected against dextran-sulfate sodium (DSS)-induced barrier dysfunction. In mice treated with AOM/DSS, oral administration of sildenafil throughout the disease course reduced polyp multiplicity by 50% compared with untreated controls. Polyps that did form in sildenafil treated mice were less proliferative and more differentiated compared with polyps from untreated mice, but apoptosis was unaffected. Polyps in sildenafil treated mice were also less inflamed; they exhibited reduced myeloid-cell infiltration and reduced expression of iNOS, IFNγ, and IL6 compared with untreated controls. Most of the protection conferred by sildenafil was during the initiation stage of carcinogenesis (38% reduction in multiplicity). Administration of sildenafil during the later promotion stages did not affect multiplicity but had a similar effect on the polyp phenotype, including increased mucus production, and reduced proliferation and inflammation. In summary, the results demonstrate that oral administration of sildenafil suppresses polyp formation and inflammation in mice treated with AOM/DSS. This validation of PDE5 as a target highlights the potential therapeutic value of PDE5 inhibitors for the prevention of colitis-driven colon cancer in humans. Cancer Prev Res; 10(7); 377-88. ©2017 AACRSee related editorial by Piazza, p. 373.

CD147 and downstream ADAMTSs promote the tumorigenicity of Kaposi's sarcoma-associated herpesvirus infected endothelial cells

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi's sarcoma (KS), which preferentially arise in immunocompromised patients and lack effective therapeutic options. We have previously shown that KSHV or viral protein LANA up-regulates the glycoprotein CD147, thereby inducing primary endothelial cell invasiveness. In the current study, we identify the global network controlled by CD147 in KSHV-infected endothelial cells using Illumina microarray analysis. Among downstream genes, two specific metalloproteases, ADAMTS1 and 9, are strongly expressed in AIDS-KS tissues and contribute to KSHV-infected endothelial cell invasiveness through up-regulation of IL-6 and VEGF. By using a KS-like nude mouse model, we found that targeting CD147 and downstream ADAMTSs significantly suppressed KSHV-induced tumorigenesis in vivo. Taken together, targeting CD147 and associated proteins may represent a promising therapeutic strategy against these KSHV-related malignancies.

Retinoblastoma-binding protein 2 (RBP2) is frequently expressed in neuroendocrine tumors and promotes the neoplastic phenotype

Neuroendocrine tumors (NETs), which can have survival rates as low as 4%, currently have limited therapeutic interventions available highlighting the dire need for the identification of novel biological targets for use as new potential drug targets. One such potential target is retinoblastoma-binding protein 2 (RBP2), an H3K4 demethylase whose overexpression has been linked to cancer formation and metastasis in non-endocrine tumor types. We measured RBP2 mRNA and protein levels in enteropancreatic NETs by measuring RBP2 in matched human normal and NET tissue samples. Further, proliferation, migration, invasion and colony formation assays were performed in the physiologically relevant NET cell lines βlox5, H727 and QGP-1 to understand the role of RBP2 and its demethylase activity on end points of tumorigenesis. Our data indicate a strong correlation between RBP2 mRNA and protein expression in NET specimens. RBP2 was overexpressed relative to tissue-matched normal controls in 80% of the human tumors measured. In vitro studies showed RBP2 overexpression significantly increased proliferation, migration, invasion and colony formation, whereas knockdown significantly decreases the same parameters in a demethylase-independent manner. The cell cycle inhibitors p21 and p57 decreased with RBP2 overexpression and increased upon its depletion, suggesting a regulatory role for RBP2 in cellular proliferation. Taken together, our results support the hypothesis that the aberrant overexpression of RBP2 is a frequent contributing factor to tumor formation and metastasis in enteropancreatic NETs.

Ceramides promote apoptosis for virus-infected lymphoma cells through induction of ceramide synthases and viral lytic gene expression

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent for several human cancers including primary effusion lymphoma (PEL), a rapidly progressive malignancy arising preferentially in immunocompromised patients. With conventional chemotherapy, PEL continues to portend high mortality, dictating the development of novel therapeutic strategies. Sphingosine kinase 2 (SphK2) represents a key gatekeeper for sphingolipid metabolism, responsible for conversion of ceramides to sphingosine-1-phosphate (S1P). We have previously demonstrated that targeting SphK2 using a novel selective inhibitor, ABC294640, leads to intracellular accumulation of ceramides and induces apoptosis for KSHV-infected PEL cells, while suppressing tumor progression in vivo. In the current study, we sought to determine whether specific ceramide/dh-ceramide species and related ceramide synthases (CerS) impact viability for KSHV-infected PEL cells during targeting of SphK2. We found that several specific ceramide and dihydro(dh)-ceramide species and their associated CerS reduce PEL survival and tumor expansion in vitro and in vivo. Moreover, we found that dhC16-Cer induces PEL apoptosis in part through activation of KSHV lytic gene expression. These data further implicate bioactive sphingolipids in regulation of PEL survival, and provide justification for future studies evaluating clinically relevant ceramide analogs or mimetics for their potential as therapeutic agents for PEL.

The homing receptor CD44 is involved in the progression of precancerous gastric lesions in patients infected with Helicobacter pylori and in development of mucous metaplasia in mice

Infection with Helicobacter pylori (H. pylori) leads to inflammatory events that can promote gastric cancer development. Immune cells transition from the circulation into the infected mucosa through the interaction of their receptors and ligands in the endothelial compartment. CD44 expression is increased in advanced gastric lesions. However, the association of this molecule with the progression of these lesions over time has not been investigated. In addition, there is a lack of understanding of the CD44-dependent cellular processes that lead to gastritis, and possibly to gastric cancer. Here we studied H. pylori-positive subjects with gastric lesions that ranged from multifocal atrophic gastritis to dysplasia to determine gene expression changes associated with disease progression over a period of 6 years. We report that CD44 expression is significantly increased in individuals whose gastric lesions progressed along the gastric precancerous cascade. We also show that CD44-/- mice develop less severe and less extensive H. pylori-induced metaplasia, and show fewer infiltrating Gr1+ cells compared to wild type mice. We present data suggesting that CD44 is associated with disease progression. Mechanisms associated with these effects include induction of interferon gamma responses.

Inhibition of Fatty Acid Oxidation Modulates Immunosuppressive Functions of Myeloid-Derived Suppressor Cells and Enhances Cancer Therapies

Myeloid-derived suppressor cells (MDSC) promote tumor growth by inhibiting T-cell immunity and promoting malignant cell proliferation and migration. The therapeutic potential of blocking MDSC in tumors has been limited by their heterogeneity, plasticity, and resistance to various chemotherapy agents. Recent studies have highlighted the role of energy metabolic pathways in the differentiation and function of immune cells; however, the metabolic characteristics regulating MDSC remain unclear. We aimed to determine the energy metabolic pathway(s) used by MDSC, establish its impact on their immunosuppressive function, and test whether its inhibition blocks MDSC and enhances antitumor therapies. Using several murine tumor models, we found that tumor-infiltrating MDSC (T-MDSC) increased fatty acid uptake and activated fatty acid oxidation (FAO). This was accompanied by an increased mitochondrial mass, upregulation of key FAO enzymes, and increased oxygen consumption rate. Pharmacologic inhibition of FAO blocked immune inhibitory pathways and functions in T-MDSC and decreased their production of inhibitory cytokines. FAO inhibition alone significantly delayed tumor growth in a T-cell-dependent manner and enhanced the antitumor effect of adoptive T-cell therapy. Furthermore, FAO inhibition combined with low-dose chemotherapy completely inhibited T-MDSC immunosuppressive effects and induced a significant antitumor effect. Interestingly, a similar increase in fatty acid uptake and expression of FAO-related enzymes was found in human MDSC in peripheral blood and tumors. These results support the possibility of testing FAO inhibition as a novel approach to block MDSC and enhance various cancer therapies.

Inhibition of fatty acid oxidation blocks asthma in mice (HYP2P.340)

Background: There has been a growing appreciation for the role of energy metabolic pathways in the differentiation and function of immune cells. Unpublished findings from our laboratory suggest that inhibiting fatty acid oxidation (FAO) modulates the activation and function of tumor-infiltrating myeloid cells, indicating a potentially important role for FAO in inflammation and thus inflammatory diseases such as asthma. Objective: We sought to test the hypothesis that FAO plays an important role in asthma manifestation. Methods: Etomoxir, an inhibitor of the FAO rate-limiting enzyme carnithine palmitoyltransferase-1, was used to test our hypothesis in an ovalbumin-based murine model of asthma. Results: Etomoxir treatment thirty minutes after ovalbumin challenge resulted in a significant reduction in the recruitment of eosinophils and macrophages into the lungs without a prominent effect on the total number of lymphocytes. Etomoxir treatment also prevented ovalbumin-induced hyperresponsiveness. The protective effects of etomoxir were associated with a decrease in Th2 cytokines and ovalbumin-specific IgE production. Additionally, the frequency of splenic macrophages was lower in etomoxir-treated mice, compared with control. Conclusions: Our preliminary data suggest the inhibition of FAO as a likely strategy to block asthma traits. As such, we are currently uncovering the mechanisms by which FAO inhibition reduces the pathogenesis of asthma.

Inhibiting fatty acid oxidation blocks the immunosuppressive functions of myeloid-derived suppressor cells and enhances cancer therapies (TUM6P.960)

Myeloid-derived suppressor cells (MDSC) promote tumor growth by inhibiting T cell immunity through various mechanisms including the depletion of arginine and the production of nitric oxide and peroxinitrites. Blocking of any single mechanism has only moderate therapeutic effects because MDSC show high adaptability and upregulate the remaining suppressive pathways. We studied whether disrupting the energy metabolic pathway(s) of MDSC would modulate their immunosuppressive functions and enhance antitumor effects. Using several murine tumor models, we found that tumor-infiltrating MDSC (T-MDSC) increased fatty acid uptake and activated fatty acid oxidation (FAO). This was accompanied by increased mitochondrial mass and function, key FAO enzymes, and oxygen consumption rate. These metabolic changes paralleled with the induction of immunosuppressive mechanisms. Inhibition of FAO blocked immunosuppressive mechanisms and functions in T-MDSC and decreased their production of immunosuppressive cytokines. Interestingly, it also diminished the number of regulatory T cells and resulted in a T cell-dependent decrease in tumor growth. FAO inhibition also significantly increased antitumor effects with low-dose chemotherapy or cellular immunotherapy. Human MDSC demonstrated similar characteristics. These data support the possibility of testing FAO inhibition as a novel approach to block MDSC and enhance various cancer therapies. *F. Hossain and A.A. Al-Khami contributed equally to this work.

The stress-response sensor chop regulates the function and accumulation of myeloid-derived suppressor cells in tumors

Adaptation of malignant cells to the hostile milieu present in tumors is an important determinant of their survival and growth. However, the interaction between tumor-linked stress and antitumor immunity remains poorly characterized. Here, we show the critical role of the cellular stress sensor C/EBP-homologous protein (Chop) in the accumulation and immune inhibitory activity of tumor-infiltrating myeloid-derived suppressor cells (MDSCs). MDSCs lacking Chop had decreased immune-regulatory functions and showed the ability to prime T cell function and induce antitumor responses. Chop expression in MDSCs was induced by tumor-linked reactive oxygen and nitrogen species and regulated by the activating-transcription factor-4. Chop-deficient MDSCs displayed reduced signaling through CCAAT/enhancer-binding protein-β, leading to a decreased production of interleukin-6 (IL-6) and low expression of phospho-STAT3. IL-6 overexpression restored immune-suppressive activity of Chop-deficient MDSCs. These findings suggest the role of Chop in tumor-induced tolerance and the therapeutic potential of targeting Chop in MDSCs for cancer immunotherapy.

Abstract LB-3: Apolipoprotein (E) is a determinant of colon carcinogenesis potentially by regulating inflammation and β-catenin independently of its role in lipid metabolism

Colorectal cancer is a leading cause of cancer-related mortality. Apolipoprotein E (ApoE) is a major player in cholesterol metabolism and has been suggested, through association studies, to play a role in colon homoeostasis and cancer. Genetic studies suggested that polymorphisms in the ApoE alleles constitute a risk factor for the development of colon cancer. Collectively, these studies explored the role of ApoE in colon cancer by narrowly focusing on its established function in lipid metabolism. In the current study, we utilized a genetic mouse model (ApcMin mouse) of colon cancer to test the hypothesis that ApoE is a determinant in the disease progression. We show that ApoE gene heterozygosity, which reduces the protein (∼50%) and minimally affects the lipid profile, significantly increased tumor burden in ApcMin mice both in the small intestine and the colon. Surprisingly, ApoE gene knockout, which completely eliminates the protein and drastically elevates the lipid profile, did not aggravate the tumor burden in ApcMin mice compared to that caused by gene heterozygosity, suggesting a novel and cholesterol-metabolism-independent function for ApoE in colon homeostasis. In vitro studies with primary colon epithelial cells, isolated using a novel technique developed by our laboratory, show that ApoE-deficiency achieved by ApoE heterozygosity, knockout, or knockdown increased the level of active β-catenin in the absence of any stimulation. It appears that such increase in β-catenin may be at an mRNA level. ApoE deficiency was also associated with an increase in inflammatory factors including VCAM-1, MCP-1, and COX-2 in TNF-treated colon epithelial cells. Altogether, our preliminary results suggest a major role of ApoE in colon homeostasis and that deficiency in ApoE levels may constitute a risk factor for colon cancer progression.

Citation Format: Ali I. Elbahrawy, Abdelmetalab Tarhuni, Amarjit S. Naura, Youssef Errami, Mohamed Alwan, Samar Hammad, Jimena Trillo-Tinoco, Ramadan Hemeida, Hassan Brim, Hassan Ashktorab, Luis Del Valle, Hamid A. Boulares. Apolipoprotein (E) is a determinant of colon carcinogenesis potentially by regulating inflammation and β-catenin independently of its role in lipid metabolism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-3. doi:10.1158/1538-7445.AM2014-LB-3

Rescue of notch-1 signaling in antigen-specific CD8+ T cells overcomes tumor-induced T-cell suppression and enhances immunotherapy in cancer

An impaired antitumor immunity is found in patients with cancer and represents a major obstacle in the successful development of different forms of immunotherapy. Signaling through Notch receptors regulates the differentiation and function of many cell types, including immune cells. However, the effect of Notch in CD8(+) T-cell responses in tumors remains unclear. Thus, we aimed to determine the role of Notch signaling in CD8(+) T cells in the induction of tumor-induced suppression. Our results using conditional knockout mice show that Notch-1 and Notch-2 were critical for the proliferation and IFNγ production of activated CD8(+) T cells and were significantly decreased in tumor-infiltrating T cells. Conditional transgenic expression of Notch-1 intracellular domain (N1IC) in antigen-specific CD8(+) T cells did not affect activation or proliferation of CD8(+) T cells, but induced a central memory phenotype and increased cytotoxicity effects and granzyme B levels. Consequently, a higher antitumor response and resistance to tumor-induced tolerance were found after adoptive transfer of N1IC-transgenic CD8(+) T cells into tumor-bearing mice. Additional results showed that myeloid-derived suppressor cells (MDSC) blocked the expression of Notch-1 and Notch-2 in T cells through nitric oxide-dependent mechanisms. Interestingly, N1IC overexpression rendered CD8(+) T cells resistant to the tolerogenic effect induced by MDSC in vivo. Together, the results suggest the key role of Notch in the suppression of CD8(+) T-cell responses in tumors and the therapeutic potential of N1IC in antigen-specific CD8(+) T cells to reverse T-cell suppression and increase the efficacy of T cell-based immunotherapies in cancer.

Targeting sphingosine kinase induces apoptosis and tumor regression for KSHV-associated primary effusion lymphoma

Sphingosine kinase (SPHK) is overexpressed by a variety of cancers, and its phosphorylation of sphingosine results in accumulation of sphingosine-1-phosphate (S1P) and activation of antiapoptotic signal transduction. Existing data indicate a role for S1P in viral pathogenesis, but roles for SPHK and S1P in virus-associated cancer progression have not been defined. Rare pathologic variants of diffuse large B-cell lymphoma arise preferentially in the setting of HIV infection, including primary effusion lymphoma (PEL), a highly mortal tumor etiologically linked to the Kaposi's sarcoma-associated herpesvirus (KSHV). We have found that ABC294640, a novel clinical-grade small molecule selectively targeting SPHK (SPHK2 >> SPHK1), induces dose-dependent caspase cleavage and apoptosis for KSHV(+) patient-derived PEL cells, in part through inhibition of constitutive signal transduction associated with PEL cell proliferation and survival. These results were validated with induction of PEL cell apoptosis using SPHK2-specific siRNA, as well as confirmation of drug-induced SPHK inhibition in PEL cells with dose-dependent accumulation of proapoptotic ceramides and reduction of intracellular S1P. Furthermore, we demonstrate that systemic administration of ABC294640 induces tumor regression in an established human PEL xenograft model. Complimentary ex vivo analyses revealed suppression of signal transduction and increased KSHV lytic gene expression within drug-treated tumors, with the latter validated in vitro through demonstration of dose-dependent viral lytic gene expression within PEL cells exposed to ABC294640. Collectively, these results implicate interrelated mechanisms and SPHK2 inhibition in the induction of PEL cell death by ABC294640 and rationalize evaluation of ABC294640 in clinical trials for the treatment of KSHV-associated lymphoma.

Association of human neurotropic JC virus with pediatric gangliogliomas

2085

Background: JC virus (JCV), a member of the Polyomaviridaefamily, is a widespread ubiquitous human pathogen found in greater than 80% of the adult population, where it persists in a latent state, most likely in the kidneys and bone marrow. JCV is tumorogenic in animals and is associated with a variety of human malignancies, including brain tumors where it infects glial cells. JCV exerts its oncogenic effects through the oncoprotein T-Antigen, which binds and inactivates tumor suppressor proteins p53 and Rb. In addition, T-Antigen can translocate IRS-1 to the nucleus, where it impedes faithful DNA repair. In this study, we will investigate the presence of JC virus and the oncoprotein T-Antigen and explore their role in pediatric gangliogliomas. Methods: Formalin-fixed paraffin-embedded tissue samples of pediatric gangliogliomas were obtained from the archives of the Pathology Department at Children’s Hospital in New Orleans. PCR amplification was performed with specific primers for the T-Antigen coding region of JCV. Immunohistochemistry for T-Antigen, p53, Rb, and IRS-1, the docking molecule of the IGF-1 pathway, was also performed. Results: Our study included 15 samples of pediatric gangliogliomas. JCV genomic sequences were amplified in 12 of the 15 samples (80%). T-Antigen expression was found in the nuclei of tumor cells in 7 of the 15 samples (47%) by immunohistochemistry. T-Antigen was present in both the glial and neuronal components of the tumors. Of the seven samples positive for T-Antigen, five were positive for both p53 and Rb, one was positive for p53, and one was negative for both p53 and Rb, but positive for nuclear IRS-1. Conclusions: The presence of JCV genomic sequences in pediatric tumors suggests that primary infection occurs early in life. The expression of T-Antigen in both the glial and neuronal components of gangliogliomas suggests that these mixed tumors most likely originate in a common primitive cell, which then differentiates into two different phenotypes. The co-localization of T-Antigen with p53 and Rb suggests that cell cycle deregulation is one oncogenic pathway in gangliogliomas. Nuclear IRS-1 suggests alterations on faithful DNA repair mechanisms. These findings warrant further investigation.