Syngeneic Hosts Research Articles

Abstract 1017: Lipid metabolic reprogramming drives resistance to PD1 blockage

Abstract The mechanisms underlying immunosuppression and resistance to PD1 inhibitors in cancer are not well understood. We attempted to fill this gap with an integrated analysis of mRNA, microRNA, and protein expression in an anti-PD1-resistant lung adenocarcinoma mouse model. The model was created by in vivo passage of 344SQ murine lung cancer cells (p53R172HΔg/+K-rasLA1/+) in a syngeneic host repeatedly dosed with anti-mouse PD1 antibodies. Anti-PD1-resistant 344SQ (344SQ_R) and 344SQ parental (344SQ_P) cells were then inoculated into syngeneic 129Sv/ev mice, which were then dosed twice with anti-PD1 or control IgG antibodies. Tumor tissues were collected and analyzed as follows: transcriptome with Affymetrix; protein levels by reverse phase protein array analysis; signature enrichment by gene set enrichment analysis; metabolome by mass spectrometry; and lipid content with fluorescent probes Oil O rad and BODIPY. We also isolated tumor-infiltrating immune cells for flow cytometry and gene expression analyses. We identified lipid-related metabolic pathways as being the most highly enriched in anti-PD1-resistant tumors (344SQ_R) vs. their 344SQ_P counterparts; the resistant cells also had more lipid droplets than the 344SQ_P cells. The anti-PD1-resistant tumors overexpressed several genes involved in lipogenesis and fatty acid pathways (e.g., fatty acid binding proteins [FABPs], fatty acid synthase, acetyl-coA-acyltransferase 2, fatty acid elongases). Specifically, FABP overexpression promoted fatty acid uptake and lipid-droplet accumulation in resistant tumors. Lipid-sensitive targets linked to inflammation and insulin signaling (e.g,. stress-activated kinases such as JNK and NFκB) were altered in 344SQ_R vs. 344SQ_P tumors. Mechanistically, JNK downregulation by NFκB-regulated microRNAs protected PD1-resistant tumors from lipotoxicity caused by FABPs upregulation and fatty acid uptake. FABP levels were higher in plasma from 344SQ_R than from 344SQ_P tumors. Tumor-infiltrating macrophages from 344SQ_R tumors had 4 times the amount of FABP mRNA than parental tumors and a correspondingly higher percentage of M2-like macrophages. 344SQ_R tumors promoted immune suppressive cells by upregulating FABPs expression in M2-like macrophages, marked by increased fatty acid intake and fatty acid oxidation. Conversely, percentages of CD4+ and CD8+ tumor-infiltrating lymphocytes were reduced in the resistant tumors. These results suggest that lipid metabolic rewiring drives resistance PD1 inhibitors supporting the accumulation of immunosuppressive cells, including M2-like macrophages, preventing type I immune responses elicited by T cells. Collectively, these findings reveal new potential lipid-related targets for drug development or new treatments combining inhibitors of these targets with anti-PD1 therapy. Citation Format: Maria A. Cortez, Sharareh Niknam, Efrosini Cuko, Jonathan E. Schoenhals, Hampartsoum Barsoumian, Ahmed I. Younes, Ailin Li, Jody V. Vykoukal, Cristina Ivan, George A. Calin, Patrick Hwu, James W. Welsh. Lipid metabolic reprogramming drives resistance to PD1 blockage [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1017. doi:10.1158/1538-7445.AM2017-1017

Fatty-acid-binding proteins as a novel target for the treatment of anti-PD-1-resistant tumors.

11562 Background: The mechanisms underlying immunosuppression and resistance to PD1 inhibitors in cancer are not well understood. We attempted to fill this gap with an integrated transcriptome analysis in an anti-PD1-resistant lung adenocarcinoma mouse model. The model was created by in vivo passage of 344SQ murine lung cancer cells (p53R172HΔg/+K-rasLA1/+) in a syngeneic host repeatedly dosed with anti-mouse PD1 antibodies. Anti-PD1-resistant 344SQ (344SQ_R) and 344SQ parental (344SQ_P) cells were then inoculated into syngeneic 129Sv/ev mice, which were then dosed twice with anti-PD1 or control IgG antibodies. Methods: Tumor tissues were collected and analyzed as follows: transcriptome with Affymetrix; protein levels by reverse phase protein array analysis; signature enrichment by gene set enrichment analysis; metabolome by mass spectrometry; and lipid content with fluorescent probes Oil O and BODIPY. We also isolated tumor-infiltrating immune cells for flow cytometry and gene expression analyses. Results: We identified lipid-related metabolic pathways as being the most highly enriched in anti-PD1-resistant tumors (344SQ_R) vs. their 344SQ_P counterparts; the resistant cells also had more lipid droplets than the 344SQ_P cells. The anti-PD1-resistant tumors overexpressed several genes involved in lipogenesis and fatty acid pathways, including fatty acid binding proteins (FABPs). Specifically, FABP overexpression promoted fatty acid uptake and lipid-droplet accumulation in resistant tumors. 344SQ_R tumors promoted immune suppressive cells by upregulating FABPs expression in M2-like macrophages, marked by increased fatty acid intake and fatty acid oxidation. Conversely, percentages of CD4+ and CD8+ tumor-infiltrating lymphocytes were reduced in the resistant tumors. Conclusions: These results suggest that lipid metabolic rewiring drives resistance PD1 inhibitors supporting the accumulation of immunosuppressive cells, including M2-like macrophages, preventing type I immune responses elicited by T cells. Collectively, these findings reveal new potential lipid-related targets for drug development or new treatments combining inhibitors of these targets with anti-PD1 therapy.

Tbet is a critical modulator of FoxP3 expression in autoimmune graft-versus-host disease.

CD4+ T-helper subsets drive autoimmune chronic graft-versus-host disease, a major complication after allogeneic bone marrow transplantation. However, it remains unclear how specific T-helper subsets contribute to chronic graft-versus-host disease. T-helper type 1 cells are one of the major disease-mediating T-cell subsets and require interferon-γ signaling and Tbet expression for their function. Regulatory T cells on the other hand can inhibit T-helper type 1 cell-mediated responses. Using an established murine model that isolates the autoimmune component of graft-versus-host disease, we hypothesized that T-helper type 1 cells would restrict FoxP3-driven regulatory T cells. Upon transfer into immune-deficient syngeneic hosts, alloreactive Tbx21−/−CD4+ T cells led to marked increases in FoxP3+ cells and reduced clinical evidence of autoimmunity. To evaluate whether peripheral induction contributed to regulatory T-cell predominance, we adoptively transferred Tbx21−/− T cells that consisted of fate mapping for FoxP3: recipients of flow-purified effector cells that were Foxp3− and Tbx21−/− had enhanced T-regulatory-cell predominance during autoimmune graft-versus-host disease. These data directly demonstrated that peripheral T-regulatory-cell induction was inhibited by Tbet. Finally, Tbx21−/− T-regulatory cells cross-regulated autoimmune wild-type T-effector-cell cytokine production in vivo. The Tbet pathway therefore directly impairs T-regulatory-cell reconstitution and is consequently a feasible target in efforts to prevent autoimmune graft-versus-host disease.

Immunocompetent mouse allograft models for development of therapies to target breast cancer metastasis.

Effective drug development to combat metastatic disease in breast cancer would be aided by the availability of well-characterized preclinical animal models that (a) metastasize with high efficiency, (b) metastasize in a reasonable time-frame, (c) have an intact immune system, and (d) capture some of the heterogeneity of the human disease. To address these issues, we have assembled a panel of twelve mouse mammary cancer cell lines that can metastasize efficiently on implantation into syngeneic immunocompetent hosts. Genomic characterization shows that more than half of the 30 most commonly mutated genes in human breast cancer are represented within the panel. Transcriptomically, most of the models fall into the luminal A or B intrinsic molecular subtypes, despite the predominance of an aggressive, poorly-differentiated or spindled histopathology in all models. Patterns of immune cell infiltration, proliferation rates, apoptosis and angiogenesis differed significantly among models. Inherent within-model variability of the metastatic phenotype mandates large cohort sizes for intervention studies but may also capture some relevant non-genetic sources of variability. The varied molecular and phenotypic characteristics of this expanded panel of models should aid in model selection for development of antimetastatic therapies in vivo, and serve as a useful platform for predictive biomarker identification.

Abstract P6-10-02: MHC-II positive breast tumors are more immunogenic and may preferentially select for LAG-3-positive tumor immune infiltrates

Abstract Background: Lymphocyte-activation gene 3 (LAG-3) is a T-cell checkpoint regulator and a current target in immunotherapy trials. LAG-3's main ligand is MHC class II (MHC-II), to which it binds with higher affinity than CD4. Binding of LAG3 to MHC-II antigen-presenting cells negatively regulates cellular proliferation, activation, and homeostasis of T cells, similarly to CTLA-4 and PD-1, suggesting that antibodies targeting LAG-3 may demonstrate similar anti-tumor immune effects. Hypothesis: We recently reported an association of MHC-II on tumor cells and its involvement in mediating sensitivity to PD-1/PD-L1 monoclonal antibodies. MHC-II demonstrates a strong bimodal expression pattern on tumor cells from a variety of tissues, including those of the breast. In breast cancer patients, tumor-specific MHC-II expression on TNBCs is correlated with a 'hot' immune environment. We hypothesized that 1) MHC-II expression may drive potent anti-tumor immune responses and 2) MHC-II-positive tumors that generate immunotolerance may develop a specific immune checkpoint dependency on LAG-3, since LAG-3 is the inhibitory receptor for MHC-II-mediated antigen presentation. Methods: To determine the functionality of MHC-II in driving anti-tumor immune responses, we constitutively expressed the MHC-II master regulator CIITA in MMTV-neu mouse tumor cells and determined their ability to form tumors in immunocompetent syngeneic hosts. To evaluate the association of MHC-II+ tumors with LAG-3 expression, we evaluated LAG-3-positivity by immunohistochemistry (IHC) in lymphocytic infiltrates in a series of 111 post-NAC TNBC specimens from patients with residual disease remaining after presurgical chemotherapy. Tumor-infiltrating lymphocytes (TILs) were scored by H&E, PD-L1 and MHC-II (HLA-DR) were scored in the stroma and tumor compartments using automated quantitative immunofluorescence (AQUA). Results: Enforced expression of MHC-II via constitutive expression of CIITA caused rejection in 60% of mice, while only 11% of mice rejected MMTV-neu tumors expressing the vector control (Fisher's exact p=0.04). All rejecting mice were immune to rechallenge with parental (non-CIITA-expressing) MMTV-neu cells, suggesting a memory effector response. Clinically, 11/102 patients (10.8%) had LAG-3+ immune cells in their tumor. LAG-3+ tumors were strongly correlated with MHC-II positivity in tumor cells (p<0.0001). Presence of LAG-3+ cells also correlated strongly with overall TILs (p<0.0001), and PD-L1 expression on TILs (p<0.02). Since the likelihood of identifying LAG3+ lymphocytes is confounded by the inclusion of poorly-infiltrated tumors, we performed a subset analysis on only those tumors with substantial TILs (>20%). When this subset was analyzed, LAG-3 positivity retained its association with tumor MHC-II expression (p=0.0001), while the association of LAG-3 with stromal PD-L1 was reduced below the level of significance (p=0.052). Conclusions: MHC-II expression causes increased immune activation in breast cancers, consistent with our previous findings. MHC-II positivity in breast tumors may identify a population with preferential dependence on the LAG-3 checkpoint, which may be important for future immunotherapy trials. Citation Format: Balko JM, Loi S, Giltnane JM, Combs S, Estrada MV, Sanchez V, Rimm D, Sanders ME, Salgado R, Gomez H, Johnson DB. MHC-II positive breast tumors are more immunogenic and may preferentially select for LAG-3-positive tumor immune infiltrates [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-10-02.

Suppression of Type I IFN Signaling in Tumors Mediates Resistance to Anti-PD-1 Treatment That Can Be Overcome by Radiotherapy.

Immune checkpoint therapies exhibit impressive efficacy in some patients with melanoma or lung cancer, but the lack of response in most cases presses the question of how general efficacy can be improved. In addressing this question, we generated a preclinical tumor model to study anti-PD-1 resistance by in vivo passaging of Kras-mutated, p53-deficient murine lung cancer cells (p53R172HΔg/+K-rasLA1/+ ) in a syngeneic host exposed to repetitive dosing with anti-mouse PD-1 antibodies. PD-L1 (CD274) expression did not differ between the resistant and parental tumor cells. However, the expression of important molecules in the antigen presentation pathway, including MHC class I and II, as well as β2-microglobulin, were significantly downregulated in the anti-PD-1-resistant tumors compared with parental tumors. Resistant tumors also contained fewer CD8+ (CD8α) and CD4+ tumor-infiltrating lymphocytes and reduced production of IFNγ. Localized radiotherapy induced IFNβ production, thereby elevating MHC class I expression on both parental and resistant tumor cells and restoring the responsiveness of resistant tumors to anti-PD-1 therapy. Conversely, blockade of type I IFN signaling abolished the effect of radiosensitization in this setting. Collectively, these results identify a mechanism of PD-1 resistance and demonstrate that adjuvant radiotherapy can overcome resistance. These findings have immediate clinical implications for extending the efficacy of anti-PD-1 immune checkpoint therapy in patients. Cancer Res; 77(4); 839-50. ©2016 AACR.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Transduction-Transplantation Mouse Model of Myeloproliferative Neoplasm.

Transduction-transplantation is a quick and efficient way to model human hematologic malignancies in mice. This technique results in expression of the gene of interest in hematopoietic cells and can be used to study the gene's role in normal and/or malignant hematopoiesis. This protocol provides a detailed description on how to perform transduction-transplantation using calreticulin (CALR) mutations recently identified in myeloproliferative neoplasm (MPN) as an example. In this protocol whole bone marrow cells from 5-flurouracil (5-FU) treated donor mice are transduced with a retrovirus encoding mutant CALR and transplanted into lethally irradiated syngeneic hosts. Donor cells expressing mutant CALR are marked with green fluorescent protein (GFP). Transplanted mice develop an MPN phenotype including elevated platelets in the peripheral blood, expansion of megakaryocytes in the bone marrow, and bone marrow fibrosis. We provide a step-by-step account of how to generate retrovirus, calculate viral titer, transduce whole bone marrow cells, and transplant into irradiated recipient mice.

Abstract 4114: Blocking Ezrin can inhibit HGF/Met signaling-induced metastasis

Abstract Hepatocyte Growth Factor (HGF) binds its receptor Met and induces autophosphorylation of MET, which in turn activate appropriate signaling pathways. Aberrant HGF/Met signaling promotes tumor progression by facilitating cell proliferation, migration, invasion, and metastasis. Previously, we found that constitutive HGF/Met signaling promotes melanoma metastasis through a nonautocrine mechanism in engineered mouse models (Cancer Res, 2002); however, the molecular mechanisms by downstream of HGF/Met signaling that induce metastasis are not known. We recently identified the cytoskeletal organizer Ezrin as a key metastatic regulator using an HGF transgenic mouse model (Nature Medicine, 2004), implicating Ezrin is in HGF/Met signaling-induced metastasis. We hypothesize that HGF/Met signaling promotes metastasis by regulating expression of Ezrin. To test hypothesis, we are: 1) evaluating the relationship between ezrin expression and HGF/Met signaling; 2) validating the role of Ezrin in HGF/Met signaling -induced metastasis; 3) elaborating mechanisms underlying this HGF/Met signaling-mediated regulation of Ezrin expression; 4) evaluating the clinical therapeutic utility of blockage of Ezrin function in preclinical mouse models. We found that HGF is able to stimulate the expression of Ezrin. Moreover, analysis of the established model systems with HGF and Met alone or HGF with Met demonstrated that Ezrin expression correlated with activated HGF/Met signaling, suggesting that HGF/Met signaling regulates the expression of Ezrin. Interestingly, we showed that HGF/Met signaling could activate transcription factor Sp1 through the MAPK pathway. We further found that activated Sp1 could directly bind to the promoter of the Ezrin gene and regulate the transcription of Ezrin. Notably, knockdown of Ezrin expression by shRNAs inhibited the metastasis induced by both HGF/Met autocrine and notautocrine signaling in syngeneic host and HGF GEM hosts. We also used small molecule drugs in preclinical mouse models to confirm that Ezrin is at least one of downstream molecules mediating HGF/Met signaling-induced metastasis in melanoma. We conclude that Ezrin is a key downstream substrate involved in the regulation of HGF/Met signaling-induced metastasis. We demonstrate a link between Ezrin and HGF/Met/MAPK/Sp1 activation in the metastatic process. Our data indicate that Ezrin represents a promising therapeutic target for patients with activated HGF/Met signaling. Citation Format: Yanlin Yu, Liping Huang, Glenn Merlino. Blocking Ezrin can inhibit HGF/Met signaling-induced metastasis. [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 4114.

Abstract 2827: PD0332991-induced stromal senescence promotes melanoma growth in vivo

Abstract Cellular senescence, a process in which cells permanently exit the cell cycle, has pleiotropic biological effects. Several lines of evidence suggest that senescent cells within the tumor microenvironment can elicit a pro-inflammatory secretome that promotes cancer initiation and progression. This proinflammatory phenotype differs amongst senescent cells triggered by distinct stimuli; therefore, multiple forms of senescent cells likely exist within the tumor stroma during cancer evolution and treatment. Here, we sought to determine how stromal senescence initiated by clinically relevant treatments would influence melanoma growth. To generate senescent stromal populations, we treated presenescent MEFs (p4) with ultraviolet light (UV), Mitomycin C (MMC), or a CDK4/6 inhibitor (CDK4/6i). In contrast to p4 fibroblasts, cells treated with UV, MMC or CDK4/6i exhibited cell cycle arrest, increased SA-β-gal positivity and elevated p16INK4a expression. Pronounced 53BP1 and γH2AX foci were only observed in the UV and MMC treated cells, suggesting the CDK4/6i treatment did not induce DNA damage. Profiling of gene expression using a TaqMan mouse inflammation expression panel revealed distinctions amongst the 4 fibroblast lines. Of the senescent cell populations, CDK4/6i fibroblasts showed the highest number of elevated pro-inflammatory transcripts. To define the in vitro paracrine growth effects induced by stromal senescence, melanoma cell lines harboring either Braf600E, Ras, or unknown (wild-type) driver were co-cultured with each fibroblast population. In general, melanoma cells grew similarly on senescent and non-senescent fibroblasts; however, tumor cell growth was genotype-dependent. Notably, CDK4/6i fibroblasts never stimulated additional tumor cell growth in vitro. In contrast, syngeneic transplantations of fibroblasts and tumor cells into immune competent mice revealed that all senescent fibroblasts stimulated tumor growth in vivo. However, whether senescent and non-senescent fibroblasts promoted tumor growth at the same rate was genotype-dependent. Since this is the first study to examine the paracrine effects of senescent stromal cells using an immune competent mouse, we performed IHC for CD45 to assess whether immune cell recruitment differs in the presence of senescent stromal fibroblasts. No increase in CD45 positive infiltrates was observed in the melanoma lines co-injected with CDK4/6i fibroblasts. Together, this work reveals that melanoma growth in response to senescent stromal fibroblasts is genotype dependent, and that this stromal promotion of cancer growth can be accurately assessed only in the context of an immune competent, syngeneic host. Moreover, these data suggest that stromal senescence induced by emerging CDK4/6 inhibitor therapies and/or regimens combining chemotherapy/radiation with immune checkpoint blockade may also promote tumor growth through the paracrine effects of senescent bystanders. Citation Format: Xiangnan Guan, Kyle Lapak, Rebecca Hennessey, Christin Burd. PD0332991-induced stromal senescence promotes melanoma growth in vivo. [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 2827.

Abstract 5101: Tumor-secreted acids alter macrophage phenotype

Abstract Within tumors, tumor-associated macrophages (TAMs) usually adopt an M2 phenotype with tumor-promoting characteristics, as opposed to the M1 phenotype responsible for host protection. As acidic pH can affect the characteristics of immune cells, we aimed to test whether low pH as a common stress factor in the tumor microenvironment could be partially responsible for the phenotypic characteristics and/or functional activity of macrophages in prostate cancer. To test this hypothesis, we allowed TRAMP (TRansgenic Adenocarcinoma of the Mouse Prostate) mice to develop neoplastic lesions of variable histologic severity. Thereafter, we isolated tumor-associated macrophages from control tumors and analyzed their expression of the M1 and M2 markers; iNos, Il-6, Cd206 and Arg1. Gene expression analysis confirms previous studies which reported higher expression of both M1 and M2 markers in TAMs compared with peritoneal macrophages. Treatment of TRAMP mice with sodium bicarbonate to continuously buffer acids secreted by neoplastic cells, decreased TAMs infiltration into the stromal compartment of prostate. In addition, sodium bicarbonate decreased iNos, Arg1, and Cd206 but not Il-6 expression in TAMs isolated from subcutaneously growing TRAMP-C2 tumors, a TRAMP-derived prostate tumor cell line injected into syngeneic male hosts. Since decreased expression of Arg1 and iNos has been shown to mediate the suppressive activity of myeloid cells, tumor acidity might promote the suppressive microenvironment by upregulating both enzymes. In conclusion, extracellular acidosis increases the density of macrophages and their L-arginine metabolic potential; coincident with delayed tumor progression in prostate tumors. Citation Format: Asmaa El-Kenawi, Arig Ibrahim-Hashim, Kimberly Luddy, Brian Ruffell, Shari Pilon-Thomas, Robert Gatenby, Robert Gillies. Tumor-secreted acids alter macrophage phenotype. [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 5101.

Analysis of Conformational Stability of Abnormal Prion Protein Aggregates across the Spectrum of Creutzfeldt-Jakob Disease Prions.

The wide phenotypic variability of prion diseases is thought to depend on the interaction of a host genotype with prion strains that have self-perpetuating biological properties enciphered in distinct conformations of the misfolded prion protein PrP(Sc) This concept is largely based on indirect approaches studying the effect of proteases or denaturing agents on the physicochemical properties of PrP(Sc) aggregates. Furthermore, most data come from studies on rodent-adapted prion strains, making current understanding of the molecular basis of strains and phenotypic variability in naturally occurring diseases, especially in humans, more limited. To fill this gap, we studied the effects of guanidine hydrochloride (GdnHCl) and heating on PrP(Sc) aggregates extracted from 60 sporadic Creutzfeldt-Jakob disease (CJD) and 6 variant CJD brains. While denaturation curves obtained after exposure of PrP(Sc) to increasing GdnHCl concentrations showed similar profiles among the 7 CJD types analyzed, PrP(Sc) exposure to increasing temperature revealed significantly different and type-specific responses. In particular, MM1 and VV2, the most prevalent and fast-replicating CJD types, showed stable and highly resistant PrP(Sc) aggregates, whereas VV1, a rare and slowly propagating type, revealed unstable aggregates that easily dissolved at low temperature. Taken together, our results indicate that the molecular interactions mediating the aggregation state of PrP(Sc), possibly enciphering strain diversity, are differently targeted by GdnHCl, temperature, and proteases. Furthermore, the detected positive correlation between the thermostability of PrP(Sc) aggregates and disease transmission efficiency makes inconsistent the proposed hypothesis that a decrease in conformational stability of prions results in an increase in their replication efficiency. Prion strains are defined as infectious isolates propagating distinctive phenotypic traits after transmission to syngeneic hosts. Although the molecular basis of prion strains is not fully understood, it is largely accepted that variations in prion protein conformation drive the molecular changes leading to the different phenotypes. In this study, we exposed abnormal prion protein aggregates encompassing the spectrum of human prion strains to both guanidine hydrochloride and thermal unfolding. Remarkably, while exposure to increasing temperature revealed significant strain-specific differences in the denaturation profile of the protein, treatment with guanidine hydrochloride did not. The findings suggest that thermal and chemical denaturation perturb the structure of prion protein aggregates differently. Moreover, since the most thermostable prion protein types were those associated with the most prevalent phenotypes and most rapidly and efficiently transmitting strains, the results suggest a direct correlation between strain replication efficiency and the thermostability of prion protein aggregates.

104 Melanoma associated antigen A3 (MAGE-A3) influences proliferation of metastatic squamous cell carcinoma (SCC) in vitro

104 Melanoma associated antigen A3 (MAGE-A3) influences proliferation of metastatic squamous cell carcinoma (SCC) in vitro A Santana, N Roudiani, J Therrien, JH Lee, D Felsen and J Carucci 1 Dept. of Derm., NYU Langone Med. Ctr., New York, NY, 2 Stiefel Laboratories, Research Triangle Park, NC and 3 Inst. for Ped. Urol., Weill Cornell Medicine, New York, NY In order to identify novel targets for cancer immune therapy, our lab has profiled the expression of cancer testis antigens (CTA) in primary human SCC. CTAs are immunogenic and may be suitable targets for immunotherapy, or as biomarkers for aggressive biological behavior. We recently showed that MAGE-A3 is highly expressed in aggressive SCC with poor prognosis. We hypothesized that MAGE-A3 may be a novel target for immunotherapy and/or a biomarker for metastatic SCCs. In this study we determined MAGE-A3 expression in and the effect of antibody treatment on growth of human (A431) and murine (Pam 212 and LY2, BALB/c) SCC cell lines. Pam 212 cells develop locally invasive SCC in syngeneic hosts and LY2 were isolated from a rare Pam 212 metastasis (Yuspa et al., JID, 1983; Dong et al., J Cell Biochem 1997). A431, Pam 212, and LY2 cell lines express MAGE-A3 at the transcript and protein level as measured by qRT-PCR and immunoblot, respectively. Moreover, A431 SCC growth and proliferation was significantly inhibited after MAGE-A3 antibody treatment measured by MTT (P 0.001) and crystal violet (P 0.001). We found that cell growth and proliferation of locally invasive Pam 212 cells was unaffected by anti-MAGE-A3 treatment. However, metastatic tumor derived LY2 cell growth and proliferation was significantly inhibited after MAGE-A3 antibody treatment measured by MTT (P 0.01) and crystal violet (P 0.01). MAGE-A3 expression could potentially serve both as a cancer biomarker and vaccine candidate due to its expression by SCC cells in vitro. Interestingly, MAGE-A3 antibody treatment inhibited the growth of A431 and LY2, SCCs that metastasize in vivo. These results suggest that metastatic SCC may rely on signaling events downstream of MAGE-A3 to support proliferation. Ongoing studies focus on elucidation of pathways involved in MAGE driven SCC proliferation in vivo using immune competent BALB/c mice. 105 Keratinocyte p38a loss results in increased tumor initiation, decreased malignant progression, and altered tumor type specification during two-stage chemical carcinogenesis in murine skin A Kiss, AC Koppel, C Cataisson, J Anders, S Yuspa, P Bible, M Kellett, MI Morasso and T Efimova 1 Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington, DC, 2 Laboratory of Cancer Biology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD and 3 Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD The p38a signaling pathway not only regulates the inflammation and stress responses, but also controls, in a context-specific manner, the homeostatic balance of cell proliferation, differentiation and survival, deregulation of which is known to contribute to tumor development. Studies in mouse models revealed both tumor-suppressing and tumor-promoting roles of p38a, depending on tissue and tumor type, and tumor stage. However, the in vivo functional contributions of p38a to the skin carcinogenesis remain incompletely understood. We explored the in vivo role of p38a in two-stage chemical skin carcinogenesis using mice with conditional epidermal keratinocyte-specific genetic ablation of p38a (p38a-cKO). Mutant mice exhibited a significantly increased tumor multiplicity, and, in addition to characteristic benign and malignant squamous tumors, developed benign well-differentiated sebaceous adenomas containing a signature activating Hras mutation. Only 4% of tumors in p38a-cKO mice underwent malignant conversion to squamous cell carcinomas (SCCs), compared with 38% of tumors in wild-type (WT) mice (p<0.0001). p38a deficiency resulted in a significantly reduced size and a more differentiated morphology of p38a-cKO SCCs, relative to WT SCCs. RNA sequencing revealed p38a-dependent transcriptional changes in genes involved in cell differentiation, development, proliferation, cell death, and inflammation, both in control and in v-ras-transformed keratinocytes. Altogether, our data reveal novel roles for p38a signaling in control of tumor initiation, malignant progression, and tumor type specification.

MP29-03 SUCCESSFUL LAPAROSCOPIC ALLOTRANSPLANTATION OF EMBRYONIC KIDNEYS ENHANCED BY ADIPOSE-DERIVED STEM CELLS SUSPENSION

You have accessJournal of UrologyTransplantation & Vascular Surgery: Renal Transplantation & Vascular Surgery I1 Apr 2016MP29-03 SUCCESSFUL LAPAROSCOPIC ALLOTRANSPLANTATION OF EMBRYONIC KIDNEYS ENHANCED BY ADIPOSE-DERIVED STEM CELLS SUSPENSION César Vera-Donoso, Ximo García-Domínguez, Victoria Moreno-Manzano, Luís García-Valero, José Salvador Vicente-Antón, and Francisco Marco-Jiménez César Vera-DonosoCésar Vera-Donoso More articles by this author , Ximo García-DomínguezXimo García-Domínguez More articles by this author , Victoria Moreno-ManzanoVictoria Moreno-Manzano More articles by this author , Luís García-ValeroLuís García-Valero More articles by this author , José Salvador Vicente-AntónJosé Salvador Vicente-Antón More articles by this author , and Francisco Marco-JiménezFrancisco Marco-Jiménez More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.1087AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The use of xenotransplants has been considered for years as a possible solution to the organ shortage, but the risks of xenograft loss rejection and zoonoses have limited the clinical application of this kind of treatments. There have been several recent attempts to generate, de novo, a functional whole kidney from embryonic kidney (metanephroi) avoided rejection from non-immunosuppressed hosts. We recently generated a functional kidney de novo using a minimally invasive laparoscopic procedure to trasplant metanephroi. Allowing the kidney to grow large is another important issue; therefore, we evaluated the addition of adipose-derived stromal vascular fraction cells (SVF) or adipose derived stem cells (ASC) during trasplantation METHODS Briefly, biopsy of subcutaneous adipose tissue was collected from adult male rabbits. Manually cut into small pieces, the fat was then digested overnight, washed and centrifuge several times to constituted the SVF. For ASC amplification, the SVF was then resuspended in growth medium and kept under standard cell culture conditions for at least one week. We transplanted laparoscopically metanephroi from rabbit embryos in 3 groups: a) combined treatment with 105 cells of either mononuclear cells from the SVF or b) combined with ASC and c) control suspended in 5 µl of growth medium to test in vivo host integration and function. Then we transplant every metanephros by a laparoscopic procedure and documented the growth (weight, morphologically and histomorphometric of glomeruli) and the renin and erythropoietin transcript expression by qRT-PCR RESULTS Four weeks after transplantation, kidney graft explants were recovered and examined. In total, 3/6 SVF metanephroi, 4/6 ASC metanephroi and 3/6 control metanephroi were successfully grown. However, in the ASC group, the organ weights increased significantly (0.5±0.06 g vs 0.2±0.08 g and 0.3±0.08 g for ASC vs SVF and control group, respectively p < 0.05). In all of groups, kidney graft explants developed mature glomeruli whose histomorphometry analysis showed a similar area and perimeter of renal corpuscle and glomerulus and glomerular tuft cellularity. In addition, the expression profile of renin and erythropoietin transcript, and consistent with the expression in host kidneys CONCLUSIONS Taken together, our results demonstrated that embryonic kidney in combined treatment with adipose derived stem cells, enable the generation of kidney graft explants with higher weights after laparoscopic transplantation into syngeneic non-immunosuppressed host © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e380-e381 Advertisement Copyright & Permissions© 2016MetricsAuthor Information César Vera-Donoso More articles by this author Ximo García-Domínguez More articles by this author Victoria Moreno-Manzano More articles by this author Luís García-Valero More articles by this author José Salvador Vicente-Antón More articles by this author Francisco Marco-Jiménez More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Abstract B37: Overcoming resistance to chemotherapy using ZNF217 as a predictive marker and therapeutic target of breast cancer

Abstract When metastatic breast tumors do not respond to treatment (e.g., chemotherapy, endocrine therapy, and targeted therapies), ultimately the patient dies. Understanding the molecular events that cause metastatic recurrence after treatment and identifying effective second and third line therapies to treat recurrent tumors will significantly improve patient outcomes. We previously identified the transcription factor ZNF217 (human)/Zfp217 (mouse) as a prognostic marker of poor outcome in breast cancer patients. ZNF217 is overexpressed in breast and other cancers, and this overexpression promotes reduced survival, increased metastasis, and reduced response to therapy in patients and in our animal models. We found that Zfp217 overexpression promotes an increase in self-renewal capacity, invasion, and metastasis, as well as expansion of a progenitor cell population during both normal mammary development and breast cancer progression. We hypothesized that Zfp217 overexpression promotes resistance to therapies by expanding a progenitor cell population that can metastasize and remain resistant to chemotherapy. To determine experimentally if Zfp217 overexpression in vivo caused chemotherapy resistance, we used mouse orthotopic transplants of mouse breast cancer cells ± Zfp217 in syngeneic hosts. After treatment with combination chemotherapies (i.e., microtubule inhibitor epothilone B, adriamycin, and cyclophosphamide (EAC)), the mice overexpressing Znf217 developed chemoresistance with increased tumor volume and decreased percent survival compared to control mice. Treated mice that overexpressed Znf217 in their tumors had increased tumor burden compared to control animals. These data suggested that mice overexpressing Znf217 developed resistance to the EAC chemotherapy. Interestingly, the chemoresistant tumors that overexpress Zfp217 had increased numbers of progenitor cells that expressed markers of both luminal and myoepithelial cells (K8+K14+). In addition, chemotherapy treatment reduced but did not eliminate lung metastases compared to controls. Because ZNF217 is expressed at the highest levels in breast cancer patients with the worst prognosis, we aimed to identify treatments that kill chemoresistant cancer cells that overexpress ZNF217. To overcome breast cancer chemoresistance caused by ZNF217 overexpression, we identified triciribine, a nucleoside analog and AKT inhibitor, as a drug that kills cells that overexpress ZNF217. Currently triciribine is in a Phase I-II clinical trial using triciribine monophosphate in combination with the microtubule inhibitor paclitaxel in patients with breast and other cancers. The Phase I trial is completed, and the Phase II trial is recruiting patients. To model the Phase II clinical trial and to determine if Zfp217 overexpression is predictive of response to triciribine in breast cancer, we tested the efficacy of triciribine with paclitaxel and tested the order of treatment with paclitaxel and triciribine combination therapy by in vivo transplantation of mammary cancer cells ±Zfp217 overexpression. We found that the treatment order significantly impacted triciribine's therapeutic efficacy. This study directly influenced the design of the Phase II clinical trials with triciribine and paclitaxel in metastatic breast cancer patients. In addition, our animal models of chemoresistance after Zfp217 overexpression will be used to study the mechanisms of therapeutic resistance by the expansion of a progenitor cell population. Citation Format: Christopher Suarez, Joseph Sparano, Sunil S. Badve, Laurie E. Littlepage. Overcoming resistance to chemotherapy using ZNF217 as a predictive marker and therapeutic target of breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B37.

The Sphingosine Kinase 2 Inhibitor ABC294640 Reduces the Growth of Prostate Cancer Cells and Results in Accumulation of Dihydroceramides In Vitro and In Vivo.

Despite recent advances in the development of novel therapies against castration-resistant prostate cancer, the advanced form of the disease remains a major treatment challenge. Aberrant sphingolipid signaling through sphingosine kinases and their product, sphingosine-1-phosphate, can promote proliferation, drug resistance, angiogenesis, and inflammation. The sphingosine kinase 2 inhibitor ABC294640 is undergoing clinical testing in cancer patients, and in this study we investigated the effects this first-in-class inhibitor in castration-resistant prostate cancer. In vitro, ABC294640 decreased prostate cancer cell viability as well as the expression of c-Myc and the androgen receptor, while lysosomal acidification increased. ABC294640 also induced a greater than 3-fold increase in dihydroceramides that inversely correlated with inhibition of dihydroceramide desaturase (DEGS) activity. Expression of sphingosine kinase 2 was dispensable for the ABC294640-mediated increase in dihydroceramides. In vivo, ABC294640 diminished the growth rate of TRAMP-C2 xenografts in syngeneic hosts and elevated dihydroceramides within tumors as visualized by MALDI imaging mass spectroscopy. The plasma of ABC294640-treated mice contained significantly higher levels of C16- and C24:1-ceramides (but not dihydro-C16-ceramide) compared with vehicle-treated mice. In summary, our results suggest that ABC294640 may reduce the proliferative capacity of castration-resistant prostate cancer cells through inhibition of both sphingosine kinase 2 and dihydroceramide desaturase, thereby providing a foundation for future exploration of this small-molecule inhibitor for the treatment of advanced disease.

IMPS-39IDO1: MORE THAN JUST AN ENZYME IN MALIGNANT GLIOMA

The upregulation of indoleamine 2,3 dioxygenase 1 (IDO1) in glioblastoma (GBM) is associated with significantly decreased survival in patients. Coincidently, a GL261 glioma model genetically deficient (ie. knocked down) for tumor-derived IDO1 fails to accumulate significant levels of immunosuppressive regulatory T cells (Treg; CD4+CD25+FoxP3+), which is commensurate with a substantial survival advantage. Paradoxically, mice bearing malignant glioma and administered L1-MT, an enzymatic inhibitor of IDO1, fail to demonstrate any survival advantage. To further understand the role of IDO1 in brain tumors, my laboratory recently crossed the tamoxifen-inducible model of malignant glioma [tGBM; GFAP(ERT2)Cre+/-;p53fl/fl;Rbfl/fl;pTENfl/fl] (Chow et al., 2011; Cancer Cell) with IDO1fl/fl or IDO1−/- mice to conditionally- or globally-delete IDO1, respectively. In contrast to previous findings, the loss of tumor-derived IDO1 did not increase overall survival, with a median of 153.5 ±7.0-, 136 ±4.3- and 144.5 ±5.9-days post-tamoxifen administration for tGBM-IDO1wt/wt, tGBM-IDO1fl/fl and tGBM-IDO1−/- mice, respectively (11-12 mice/group). Concordantly, Treg accumulated in the tGBM brain tumors, regardless of IDO1 status. Unexpectedly, when tGBM-WT and tGBM-IDO1−/- tumors were isolated, followed by intracranial re-implantation (ic.) into immunocompetent syngeneic hosts, mice bearing IDO1−/- glioma survived 45.4 ±4.3 days post-ic., which was significantly longer than mice bearing WT glioma at 30.4 ±2.6 days post-ic (P = 0.0069; n = 5-9/group). These data, in combination with recent work from my laboratory demonstrating that, IDO1 in glioma cells fail to metabolize tryptophan into kynurenine, led us to search for a novel and/or contextual function. Here, we present bioinformatics analysis, Western blotting of nuclear and cytoplasmic extracts, as well as immunofluorescence showing that, IDO1 is detectable in the nucleus of glioma cells, in vivo. Strikingly, Chip-Seq. analysis confirms that IDO1 binds to- and enriches-specific DNA sites. This work identifies a novel and previously unappreciated role for IDO1-mediated immune-evasion and introduces new targets for therapeutic discovery and intervention against malignant brain tumors.

Abstract 4469: A novel class of inhibitors of the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) with potential for the treatment of cancer

Abstract A broad range of cancers express the tryptophan catabolising enzyme indoleamine 2,3-dioxygenase 1 (IDO1) as a mechanism of suppressing the endogenous anti-tumour immunity. High IDO1 expression by their tumours is associated with poor patient prognosis and has prompted the discovery of small molecule inhibitors of the enzyme for development as anti-cancer agents. Towards this end, we carried out a high throughput screen of 42,000 small molecules in the Walter and Eliza Hall Institute for Medical Research compound library and retrieved over 30 good hits with diverse structures that inhibited recombinant human IDO1 with potencies in the low μM range. Initial structure activity relationship studies of the best hits led us to focus on one chemical class, which, although less potent than some of the other hits on the list, exhibited a number of features that make it more favourable for development as a therapeutic agent. SN35837, the non-optimised hit from the high throughput screen is highly cell permeable and displays improved potency in inhibiting cytoplasmic hIDO1 in cell-based assays, compared to that for enzymatic assays. Complete inhibition of IDO1 function is seen at concentrations that has no measurable effects on cell viability. The imidazole lead from New Links Genetics, NLG919 has decreased activity in cells, whilst Incyte's hydroxyamidine inhibitor INCB024360 has similar potency in cellular and enzymatic assays. The maximum tolerated dose SN35837 in C57Bl/6 mice given as a single intraperitoneal bolus dose was 500 mg/kg. Mice tolerated daily intraperitoneal or subcutaneous administrations of SN35837 at 150 mg/kg. Statistically significant inhibition of growth of subcutaneously implanted GL261 gliomas and Lewis Lung carcinomas in syngeneic hosts were achieved after daily administration of 75 mg/kg SN35837. Preliminary studies indicate that the non-optimised hit also synergises when given in combination with anti-PD1 and anti-CTLA-4 antibodies. We conclude that derivatives of SN35837 may provide effective and potent inhibitors of IDO1 suitable for development as anti-cancer agents. Citation Format: Lai-Ming Ching, Brian D. Palmer, Petr Tomek, Jack U. Flanagan, Kimiora Henare. A novel class of inhibitors of the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) with potential for the treatment of cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4469. doi:10.1158/1538-7445.AM2015-4469

Abstract 469: mPGES1 deletion and the mechanisms of tumor growth suppression

Abstract The pro-tumor contributions of prostaglandin (PG) E2 are established, as is the clinical efficacy of pharmacological inhibition of COX-2, the rate-limiting enzyme in PGE2 synthesis. In addition to the desired suppression of tumor PGE2, collateral loss of endothelial COX-2-derived PGI2 imposes a cardiovascular hazard that limits clinical use of COX-2 inhibitors. mPGES1, the terminal enzyme in the PGE2 synthesis pathway, is an alternative target to interrupt COX-2-driven events in tumors without elevating cardiovascular risk. We engineered mice transgenic for an activated HER2/neu oncogene to lack mPGES1 globally (mPGES1 KOgl) or only in mammary epithelial cells (mPGES1 KOepi). Abdominal mammary glands from wild type (WT), heterozygous (het), mPGES1 KOgl, and mPGES1 KOepi mice were harvested at 22 weeks of age, paraffin embedded, H&amp;E stained and scanned for whole slide imaging (WSI). Tumor multiplicity was calculated based on the number of lesions on WSI. Adjacent sections were immunostained for Ki67, caspase 3, Factor VIII, CD3, and F4/80, to assess proliferation, apoptosis, angiogenesis, and tumor lymphocyte and macrophage infiltration. Tumor multiplicity was significantly higher in WT compared to either mPGES1 KOgl or mPGES1 KOepi mice. Concordantly, shRNA knock down (KD) of mPGES1 in mammary tumor cells dramatically suppressed their growth as orthotopic tumors in syngeneic immune competent WT hosts: 4 weeks after the injections, 6 out of 6 non-target shRNA control tumors grew successfully while 6 out of 10 mPGES1 KD cells failed to grow. In separate experiments, 14 of 14 non-target shRNA cells formed tumors after 2 weeks while 12 out of 18 mPGES1 KD tumors failed. By immunohistochemistry, no difference was observed in proliferation and apoptosis markers, as well as in the number of tumor infiltrating macrophages and lymphocytes, between WT, mPGES1 KOgl, and mPGES1 KOepi tumors. In contrast to our previous study in mice lacking epithelial COX-2 (COX-2 KOepi), vascularization was not different between mPEGS-1 KOepi and WT tumors suggesting divergence in the anti-tumorigenic mechanisms in mPEGS-1 KOepi and COX-2 KOepi tumors. By flow cytometry there was no difference in infiltrating macrophage and lymphocyte density or functional phenotypes, between WT, mPGES1 KOepi, and mPGES1 KD orthotopic tumors. Similarly, no difference was observed in the number of macrophages and myeloid derived suppressor cells in spleens from mPGES1 sufficient and mPGES1 KD orthotopic tumor bearing mice. In contrast, decreased co-inhibitory molecule PD-1 expressing CD4+ and CD8+ lymphocyte numbers were evident in draining lymph nodes in mice injected with mPGES1 KD cells compared to WT. This finding indicates that the absence of mPGES1-derived PGE2 renders tumor cells less efficient in creating and maintaining an immunosuppressive tumor microenvironment and that targeting mPGES1 may enhance anti-tumor immune mechanisms. Citation Format: Nune Markosyan, Andrew Rech, Robert H. Vonderheide, Garret A. FitzGerald, Emer M. Smyth. mPGES1 deletion and the mechanisms of tumor growth suppression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 469. doi:10.1158/1538-7445.AM2015-469

Abstract 427: Host and tumoral CXCR2 signaling contributes to tumor growth

Abstract Chemokines are essential mediators of leukocyte migration and inflammation. Additionally they play an important role in tumour growth. The G-protein coupled receptor, CXCR2, and its ligands (CXCL 1,2,3,5,6,7 and IL8) have been shown to promote tumour initiation and growth, chemo-resistance, angiogenesis and immune cell infiltration (neutrophil, myeloid derived suppressor cells (MDSCs) and macrophages) into the tumour microenvironment. However the contribution of host and tumour CXCR2 has not been elucidated. We have developed both murine and human specific anti-CXCR2 antibodies alongside a humanised CXCR2 transgenic mouse to address the contribution of host and tumour CXCR2 signalling to tumour growth and maintenance. In pre-clinical tumours, granulocytic cells (neutrophils and MDSCs) within the tumour increase with size, in parallel with alteration in cell numbers observed within the spleen, peripheral blood and bone marrow. Inhibition of host CXCR2 has a dramatic impact on peripheral neutrophil levels, as well as their ability to become activated. In pre-clinical tumour models, inhibition of CXCR2 results in tumour growth inhibition. Contribution of host or tumour cells to the effect of CXCR2 blockade was model dependent. In the EL4 murine lymphoma model, only inhibition of host/peripheral CXCR2 was able to impact tumour growth. Whereas, in other murine syngeneic models (CT26 and B16), both host and tumour CXCR2 play a role in tumour growth. This was further demonstrated in an NSCLC patient derived xenograft, where the contribution of tumour CXCR2 was stronger than the host. Collectively our data show that CXCR2 inhibition (alone or in combination) has potential to influence growth of a number of tumour types. Future work is focused on understanding the mechanisms underlying the effects of CXCR2 inhibition, which remain key to developing it as an effective anti-cancer therapeutic. Citation Format: Danielle Carroll, James Harper, Karen McDaid, Ruth Franks, Catherine Eberline, Jane Kendrew, Richard Sainson, Judith Anderton, Chris Rossant, Karen Coffman, Ching Ching Leow, Ivan Inigo, Mitchell Reville, Jacintha Shenton, Lesley Young, Simon Barry. Host and tumoral CXCR2 signaling contributes to tumor growth. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 427. doi:10.1158/1538-7445.AM2015-427