Salvage therapy expands highly cytotoxic and metabolically fit resilient CD8+ T cells via ME1 up-regulation

Patients with advanced cancers who either do not experience initial response to or progress while on immune checkpoint inhibitors (ICIs) receive salvage radiotherapy to reduce tumor burden and tumor-related symptoms. Occasionally, some patients experience substantial global tumor regression with a rebound of cytotoxic CD8+ T cells. We have termed the rebound of cytotoxic CD8+ T cells in response to salvage therapy as T cell resilience and examined the underlying mechanisms of resilience. Resilient T cells are enriched for CX3CR1+ CD8+ T cells with low mitochondrial membrane potential, accumulate less reactive oxygen species (ROS), and express more malic enzyme 1 (ME1). ME1 overexpression enhanced the cytotoxicity and expansion of effector CD8+ T cells partially via the type I interferon pathway. ME1 also increased mitochondrial respiration while maintaining the redox state balance. ME1 increased the cytotoxicity of peripheral lymphocytes from patients with advanced cancers. Thus, preserved resilient T cells in patients rebound after salvage therapy and ME1 enhances their resiliency.

A Novel Humanized PD-1/PD-L1 Mouse Model Permits Direct Comparison of Antitumor Immunity Generated by Food and Drug Administration-Approved PD-1 and PD-L1 Inhibitors

Seven different anti-PD-1 and PD-L1 mAbs are now widely used in the United States to treat a variety of cancer types, but no clinical trials have compared them directly. Furthermore, because many of these Abs do not cross-react between mouse and human proteins, no preclinical models exist in which to consider these types of questions. Thus, we produced humanized PD-1 and PD-L1 mice in which the extracellular domains of both mouse PD-1 and PD-L1 were replaced with the corresponding human sequences. Using this new model, we sought to compare the strength of the immune response generated by Food and Drug Administration-approved Abs. To do this, we performed an in vivo T cell priming assay in which anti-PD-1/L1 therapies were given at the time of T cell priming against surrogate tumor Ag (OVA), followed by subsequent B16-OVA tumor challenge. Surprisingly, both control and Ab-treated mice formed an equally robust OVA-specific T cell response at the time of priming. Despite this, anti-PD-1/L1-treated mice exhibited significantly better tumor rejection versus controls, with avelumab generating the best protection. To determine what could be mediating this, we identified the increased production of CX3CR1+PD-1+CD8+ cytotoxic T cells in the avelumab-treated mice, the same phenotype of effector T cells known to increase in clinical responders to PD-1/L1 therapy. Thus, our model permits the direct comparison of Food and Drug Administration-approved anti-PD-1/L1 mAbs and further correlates successful tumor rejection with the level of CX3CR1+PD-1+CD8 + T cells, making this model a critical tool for optimizing and better utilizing anti-PD-1/L1 therapeutics.

NKG7 Is a T-cell-Intrinsic Therapeutic Target for Improving Antitumor Cytotoxicity and Cancer Immunotherapy

Cytotoxic CD8⁺ T cells (CTL) are a crucial component of the immune system notable for their ability to eliminate rapidly proliferating malignant cells. However, the T-cell intrinsic factors required for human CTLs to accomplish highly efficient antitumor cytotoxicity are not well defined. By evaluating human CD8⁺ T cells from responders versus nonresponders to treatment with immune checkpoint inhibitors, we sought to identify key factors associated with effective CTL function. Single-cell RNA-sequencing analysis of peripheral CD8⁺ T cells from patients treated with anti-PD-1 therapy showed that cells from nonresponders exhibited decreased expression of the cytolytic granule-associated molecule natural killer cell granule protein-7 (NKG7). Functional assays revealed that reduced NKG7 expression altered cytolytic granule number, trafficking, and calcium release, resulting in decreased CD8⁺ T-cell-mediated killing of tumor cells. Transfection of T cells with NKG7 mRNA was sufficient to improve the tumor-cell killing ability of human T cells isolated from nonresponders and increase their response to anti-PD-1 or anti-PD-L1 therapy in vitro. NKG7 mRNA therapy also improved the antitumor activity of murine tumor antigen-specific CD8⁺ T cells in an in vivo model of adoptive cell therapy. Finally, we showed that the transcription factor ETS1 played a role in regulating NKG7 expression. Together, our results identify NKG7 as a necessary component for the cytotoxic function of CD8⁺ T cells and establish NKG7 as a T-cell-intrinsic therapeutic target for enhancing cancer immunotherapy.See related article by Li et al., p. 154.

Case Report: Simultaneous Hyperprogression and Fulminant Myocarditis in a Patient With Advanced Melanoma Following Treatment With Immune Checkpoint Inhibitor Therapy

We report here a patient with stage IV mucosal melanoma treated with dual immune checkpoint inhibitor (ICI) therapy (Nivolumab/Ipilimumab) who experienced rapid disease progression and metastatic spread within three weeks of first infusion. Surprisingly, this patient also developed fulminant myocarditis within the same time frame. Immunohistochemical staining of the primary tumor and a metastatic omental lesion revealed robust CD8⁺ PD-1⁺ T cell infiltration after ICI treatment, as would be expected following immune activation. However, the CD8⁺ T cell infiltrate was largely negative for both Granzyme B and TIA-1, suggesting these T cells were not capable of effective tumor lysis. We discuss the possibility that heightened pro-inflammatory T cell activity (rather than tumor-directed cytolytic activity) was induced by anti-PD-1 and anti-CTLA-4, which could have provoked both rapid tumor resistance mechanisms and myocarditis. This case highlights the fact that the mere presence of tumor infiltrating lymphocytes (TILs) does not necessarily correlate to ICI response and that additional functional markers are necessary to differentiate between inflammatory and cytolytic CD8⁺ TILs.

Genomic and Epigenomic Landscaping Defines New Therapeutic Targets for Adenosquamous Carcinoma of the Pancreas

Adenosquamous cancer of the pancreas (ASCP) is a subtype of pancreatic cancer that has a worse prognosis and greater metastatic potential than the more common pancreatic ductal adenocarcinoma (PDAC) subtype. To distinguish the genomic landscape of ASCP and identify actionable targets for this lethal cancer, we applied DNA content flow cytometry to a series of 15 tumor samples including five patient-derived xenografts (PDX). We interrogated purified sorted tumor fractions from these samples with whole-genome copy-number variant (CNV), whole-exome sequencing, and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) analyses. These identified a variety of somatic genomic lesions targeting chromatin regulators in ASCP genomes that were superimposed on well-characterized genomic lesions including mutations in TP53 (87%) and KRAS (73%), amplification of MYC (47%), and homozygous deletion of CDKN2A (40%) that are common in PDACs. Furthermore, a comparison of ATAC-seq profiles of three ASCP and three PDAC genomes using flow-sorted PDX models identified genes with accessible chromatin unique to the ASCP genomes, including the lysine methyltransferase SMYD2 and the pancreatic cancer stem cell regulator RORC in all three ASCPs, and a FGFR1-ERLIN2 fusion associated with focal CNVs in both genes in a single ASCP. Finally, we demonstrate significant activity of a pan FGFR inhibitor against organoids derived from the FGFR1-ERLIN2 fusion-positive ASCP PDX model. Our results suggest that the genomic and epigenomic landscape of ASCP provide new strategies for targeting this aggressive subtype of pancreatic cancer. SIGNIFICANCE: These data provide a unique description of the ASCP genomic and epigenomic landscape and identify candidate therapeutic targets for this dismal cancer.

ANT2 (SLC25A5) balances the pro-apoptotic vs. effector signals of Bim in CD8 T cells

The immune response to anti-PD-1 therapy in cancer patients is not completely defined due to lack of reliable biomarkers that can determine T cell function. Bim, a member of the Bcl-2 family, was recently identified as a downstream signaling molecule in the PD-1 pathway. Within CD8 T cells, Bim appears to have a dual function, and can be pro-apoptotic or promote effector activity. Our clinical data has shown that high levels of Bim in CD8 T cells are predictive of response to anti-PD-1 therapy in metastatic melanoma whereas in colorectal cancer, a low level of Bim is associated with treatment response. Thus, we sought to determine what molecular partners might influence the role of Bim. Using co-immunoprecipitation, high resolution microscopy and FRET we identified ANT2 (Adenine Nucleotide Translocase 2), an inner membrane protein of mitochondria, as a protein that interacts with Bim. Accordingly, we found CD8 T cells with low and high mitochondrial potential demonstrated different ANT2/Bim ratios, and a low ANT2/Bim ratio was present in effector T cells with low mitochondrial potential but high cytotoxic activity. Given the pro-survival function of ANT2, our results indicate that ANT2 may balance the pro-apoptotic and effector roles of Bim in mitochondria in order to preserve effector T cells before contraction. Understanding the molecular mechanism of Bim and ANT2 interactions in CD8 T cells may provide a novel marker to predict clinical response to anti-PD-1 therapy.

Abstract 4711: Modulation of NFκ-B signaling to optimize antitumor characteristics in macrophages

While it is known that nuclear factor κ-B (NF-κB) signaling within macrophages regulates expression of downstream targets that can mediate either pro- or antitumor functions, the mechanisms that define predominant characteristics are not well understood. As macrophages are present in the tumor microenvironment of diverse tumor types, their characteristics have the potential to either support or hinder tumor growth and metastatic spread. Therefore, a method to shift the balance of tumor associated macrophages from pro- to antitumor functions could potentially target tumor cells directly and also recruit and activate other immune cells, resulting in significant therapeutic benefit. Our studies are designed to gain an understanding of how to use modulation of NF-κB signaling as the “pinch point” to generate antitumor phenotypes and determine how to achieve this modulation in a patient. We are using immortalized bone marrow-derived macrophages or ex vivo tumor-associated macrophages in cell culture approaches and inducible transgenic mice in in vivo approaches to investigate the mechanisms by which NF-κB defines macrophage characteristics. Interactions with tumor cells are also being investigated using co-culture and murine models. Our data suggests that high levels of NFκ-B activity in macrophages induce both direct tumor cell killing and immune stimulating responses. We are testing two different translational approaches. The first is liposomal muramyl tripeptide ethanolamine that acts as an immune stimulant by increasing NF-κB activity in macrophages. The second is preferential delivery of siRNA against the inhibitor of NFκ-B (IκB-alpha) to tumor-associated macrophages using polymeric nanoparticles. We hope to better understand the mechanisms by which NFκ-B regulates macrophage functions to inform development of a novel macrophage-based immunotherapy that could be effective across a wide spectrum of solid tumors and metastatic disease.

Citation Format: Esther Liu, Alyssa A. Hoover, Whitney R. Harris, Whitney Barham, Oleg Tikhomirov, Dineo Khabele, Zahra Mirafzahli, Todd D. Giorgio, Andrew J. Wilson, Fiona E. Yull. Modulation of NFκ-B signaling to optimize antitumor characteristics in macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4711.

Immunity drives TET1 regulation in cancer through NF-κB

Ten-eleven translocation enzymes (TET1, TET2, and TET3), which induce DNA demethylation and gene regulation by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), are often down-regulated in cancer. We uncover, in basal-like breast cancer (BLBC), genome-wide 5hmC changes related to TET1 regulation. We further demonstrate that TET1 repression is associated with high expression of immune markers and high infiltration by immune cells. We identify in BLBC tissues an anticorrelation between TET1 expression and the major immunoregulator family nuclear factor κB (NF-κB). In vitro and in mice, TET1 is down-regulated in breast cancer cells upon NF-κB activation through binding of p65 to its consensus sequence in the TET1 promoter. We lastly show that these findings extend to other cancer types, including melanoma, lung, and thyroid cancers. Together, our data suggest a novel mode of regulation for TET1 in cancer and highlight a new paradigm in which the immune system can influence cancer cell epigenetics.

Targeting Epigenetic Aberrations in Pancreatic Cancer, a New Path to Improve Patient Outcomes?

Pancreatic cancer has one of the highest mortality rates among all types of cancers. The disease is highly aggressive and typically diagnosed in late stage making it difficult to treat. Currently, the vast majority of therapeutic regimens have only modest curative effects, and most of them are in the surgical/neo-adjuvant setting. There is a great need for new and more effective treatment strategies in common clinical practice. Previously, pathogenesis of pancreatic cancer was attributed solely to genetic mutations; however, recent advancements in the field have demonstrated that aberrant activation of epigenetic pathways contributes significantly to the pathogenesis of the disease. The identification of these aberrant activated epigenetic pathways has revealed enticing targets for the use of epigenetic inhibitors to mitigate the phenotypic changes driven by these cascades. These pathways have been found to be responsible for overactivation of growth signaling pathways and silencing of tumor suppressors and other cell cycle checkpoints. Furthermore, new miRNA signatures have been uncovered in pancreatic ductal adenocarcinoma (PDAC) patients, further widening the window for therapeutic opportunity. There has been success in preclinical settings using both epigenetic inhibitors as well as miRNAs to slow disease progression and eliminate diseased tissues. In addition to their utility as anti-proliferative agents, the pharmacological inhibitors that target epigenetic regulators (referred to here as readers, writers, and erasers for their ability to recognize, deposit, and remove post-translational modifications) have the potential to reconfigure the epigenetic landscape of diseased cells and disrupt the cancerous phenotype. The potential to “reprogram” cancer cells to revert them to a healthy state presents great promise and merits further investigation.

Manipulating the NF-κB pathway in macrophages using mannosylated, siRNA-delivering nanoparticles can induce immunostimulatory and tumor cytotoxic functions

Tumor-associated macrophages (TAMs) are critically important in the context of solid tumor progression. Counterintuitively, these host immune cells can often support tumor cells along the path from primary tumor to metastatic colonization and growth. Thus, the ability to transform protumor TAMs into antitumor, immune-reactive macrophages would have significant therapeutic potential. However, in order to achieve these effects, two major hurdles would need to be overcome: development of a methodology to specifically target macrophages and increased knowledge of the optimal targets for cell-signaling modulation. This study addresses both of these obstacles and furthers the development of a therapeutic agent based on this strategy. Using ex vivo macrophages in culture, the efficacy of mannosylated nanoparticles to deliver small interfering RNA specifically to TAMs and modify signaling pathways is characterized. Then, selective small interfering RNA delivery is tested for the ability to inhibit gene targets within the canonical or alternative nuclear factor-kappaB pathways and result in antitumor phenotypes. Results confirm that the mannosylated nanoparticle approach can be used to modulate signaling within macrophages. We also identify appropriate gene targets in critical regulatory pathways. These findings represent an important advance toward the development of a novel cancer therapy that would minimize side effects because of the targeted nature of the intervention and that has rapid translational potential.

Abstract A06: Novel NF-kB reporter murine model of spontaneous, metastatic breast cancer for spatiotemporal monitoring of local and systemic therapeutic response

Characterization of therapeutic response in primary and metastatic tumors is limited by endpoint studies and tissue collection. We have successfully developed a unique double-transgenic mouse model, which combines the polyoma virus middle T oncogene (PyVT), a model of human breast cancer, with a nuclear factor-kappaB (NF-kB) reporter model (NGL). PyVT mice spontaneously form primary mammary fat pad tumors, with 80% of mice developing metastatic lesions in the lungs. The reporter is luciferase, driven by NF-kB activation, to provide quantitative bioluminescent measurements of spatially-specific NF-kB activity. The resulting double transgenic (PyNGL) mice were monitored using in vivo imaging systems (IVIS) multiple times, before and after treatment, to quantitatively and spatially characterize NF-kB therapeutic response, both locally and systemically.

High intensity focused ultrasound (HIFU) was guided by magnetic resonance (MR) thermometry for tumor-localized hyperthermia which was dosage-controlled by the thermal feedback MR guided HIFU (MRgHIFU) system. A single primary mammary tumor in each PyNGL was treated with sub-ablative hyperthermia of 42⁰ for up to 25 minutes. Pre-treatment IVIS measurements were collected to determine baseline NF-kB activity within each mouse, followed by IVIS imaging every twelve hours after treatment until tissue collection. Treated tumor, contralateral (untreated) tumors, and spleens were collected for immunophenotyping and cytokine analysis using flow cytometry. PyNGL mice exhibited decreased NF-kB activity, spatially correlated with HIFU treatment, as early as 12 hours. In contrast, NF-kB increased in contralateral tumors as early as 24 hours following treatment. Immunophenotyping reveals changes in tumor infiltrating leukocyte populations in HIFU-treated and contralateral tumors, including quantity and phenotype of T cells.

The unique murine model developed allowed quantitative, temporal characterization of local and distant tumor response to MFgHIFU. The spontaneous, metastatic nature of PyVT tumor formation in concert with the non-destructive, spatiotemporal imaging capabilities of the NF-kB reporter transgene make the PyNGL model an unparalleled tool for research in metastatic disease.

Citation Format: Mary Dockery, Megan Poorman, Stephanie Dudzinski, Whitney Barham, Vandiver Chaplin, Ryan Spears, Jiro Kusunose, Fiona Yull, Charles Caskey, William Grissom, Todd Giorgio. Novel NF-kB reporter murine model of spontaneous, metastatic breast cancer for spatiotemporal monitoring of local and systemic therapeutic response. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A06.

Epithelial NF-κB signaling promotes EGFR-driven lung carcinogenesis via macrophage recruitment

Several studies have demonstrated that NF-κB activation is common in lung cancer; however, the mechanistic links between NF-κB signaling and tumorigenesis remain to be fully elucidated. We investigated the function of NF-κB signaling in epidermal growth factor receptor (EGFR)-mutant lung tumors using a transgenic mouse model with doxycycline (dox)-inducible expression of oncogenic EGFR in the lung epithelium with or without a dominant inhibitor of NF-κB signaling. NF-κB inhibition resulted in a significant reduction in tumor burden in both EGFR tyrosine kinase inhibitor (TKI)-sensitive and resistant tumors. However, NF-κB inhibition did not alter epithelial cell survival in vitro or in vivo, and no changes were detected in activation of EGFR downstream signaling pathways. Instead, we observed an influx of inflammatory cells (macrophages and neutrophils) in the lungs of mice with oncogenic EGFR expression that was blocked in the setting of NF-κB inhibition. To investigate whether inflammatory cells play a role in promoting EGFR-mutant lung tumors, we depleted macrophages and neutrophils during tumorigenesis and found that neutrophil depletion had no effect on tumor formation, but macrophage depletion caused a significant reduction in tumor burden. Together, these data suggest that epithelial NF-κB signaling supports carcinogenesis in a non-cell autonomous manner in EGFR-mutant tumors through recruitment of pro-tumorigenic macrophages.

p52 Overexpression Increases Epithelial Apoptosis, Enhances Lung Injury, and Reduces Survival after Lipopolysaccharide Treatment

Although numerous studies have demonstrated a critical role for canonical NF-κB signaling in inflammation and disease, the function of the noncanonical NF-κB pathway remains ill-defined. In lung tissue from patients with acute respiratory distress syndrome, we identified increased expression of the noncanonical pathway component p100/p52. To investigate the effects of p52 expression in vivo, we generated a novel transgenic mouse model with inducible expression of p52 in Clara cell secretory protein-expressing airway epithelial cells. Although p52 overexpression alone did not cause significant inflammation, p52 overexpression caused increased lung inflammation, injury, and mortality following intratracheal delivery of Escherichia coli LPS. No differences in cytokine/chemokine expression were measured between p52-overexpressing mice and controls, but increased apoptosis of Clara cell secretory protein-positive airway epithelial cells was observed in transgenic mice after LPS stimulation. In vitro studies in lung epithelial cells showed that p52 overexpression reduced cell survival and increased the expression of several proapoptotic genes during cellular stress. Collectively, these studies demonstrate a novel role for p52 in cell survival/apoptosis of airway epithelial cells and implicate noncanonical NF-κB signaling in the pathogenesis of acute respiratory distress syndrome.

Microenvironmental effects limit efficacy of thymoquinone treatment in a mouse model of ovarian cancer

Background

Ovarian cancer is the most lethal gynecologic malignancy, with limited treatment options for chemoresistant disease. An important link between inflammation and peritoneal spread of ovarian cancer is NF-κB signaling. Thymoquinone (TQ) exerts multiple anti-tumorigenic cellular effects, including NF-κB inhibition. We aimed to investigate the therapeutic potential of TQ in an established murine syngeneic model of ovarian cancer.

Methods

ID8-NGL mouse ovarian cancer cells stably expressing an NF-κB reporter transgene were injected intra-peritoneally into C57BL/6 mice, and mice were treated with TQ or vehicle for 10 or 30 days. TQ was combined with the macrophage depleting drug, liposomal clodronate, in selected experiments. Effects on peritoneal tumor burden were measured by volume of ascites, number of peritoneal implants and mesenteric tumor mass. NF-κB reporter activity and markers of proliferation and apoptosis were measured in tumors and in confirmatory in vitro experiments. Protein or mRNA expression of M1 (anti-tumor) and M2 (pro-tumor) macrophage markers, and soluble cytokine profiles, were examined from harvested ascites fluid, peritoneal lavages and/or tumor sections. 2-tailed Mann–Whitney tests were used for measuring differences between groups in in vivo experiments.

Results

Consistent with its effects in vitro, TQ reduced proliferation and increased apoptosis in ID8-NGL tumors after 10 and 30 day treatment. Prolonged TQ treatment did not significantly alter tumor number or mass compared to vehicle, but rather exerted an overall deleterious effect by stimulating ascites formation. Increased ascites was accompanied by elevated NF-κB activity in tumors and macrophages, increased pro-tumor M2 macrophages and expression of pro-tumorigenic soluble factors such as VEGF in ascites fluid, and increased tumor infiltration of M2 macrophages. In contrast, a 10 day exposure to TQ produced no ascites, and reduced tumor NF-κB activity, M2 macrophages and soluble VEGF levels. Peritoneal macrophage depletion by clodronate significantly reduced tumor burden. However, TQ-stimulated ascites was further enhanced by co-treatment with clodronate, with macrophages present overwhelmingly of the M2 phenotype.

Conclusions

Our findings show that pro-tumorigenic microenvironmental effects limited the efficacy of TQ in a syngeneic mouse model of ovarian cancer, and provide caution regarding its potential use in clinical trials in ovarian cancer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0463-5) contains supplementary material, which is available to authorized users.

Aberrant activation of NF-κB signaling in mammary epithelium leads to abnormal growth and ductal carcinoma in situ

BACKGROUND

Approximately 1 in 5 women diagnosed with breast cancer are considered to have in situ disease, most often termed ductal carcinoma in situ (DCIS). Though recognized as a risk factor for the development of more invasive cancer, it remains unclear what factors contribute to DCIS development. It has been shown that inflammation contributes to the progression of a variety of tumor types, and nuclear factor kappa B (NF-κB) is recognized as a master-regulator of inflammatory signaling. However, the contributions of NF-κB signaling to tumor initiation are less well understood. Aberrant up-regulation of NF-κB activity, either systemically or locally within the breast, could occur due to a variety of commonly experienced stimuli such as acute infection, obesity, or psychological stress. In this study, we seek to determine if activation of NF-κB in mammary epithelium could play a role in the formation of hyperplastic ductal lesions.

METHODS

Our studies utilize a doxycycline-inducible transgenic mouse model in which constitutively active IKKβ is expressed specifically in mammary epithelium. All previously published models of NF-κB modulation in the virgin mammary gland have been constitutive models, with transgene or knock-out present throughout the life and development of the animal. For the first time, we will induce activation at later time points after normal ducts have formed, thus being able to determine if NF-κB activation can promote pre-malignant changes in previously normal mammary epithelium.

RESULTS

We found that even a short pulse of NF-κB activation could induce profound remodeling of mammary ductal structures. Short-term activation created hyperproliferative, enlarged ducts with filled lumens. Increased expression of inflammatory markers was concurrent with the down-regulation of hormone receptors and markers of epithelial differentiation. Furthermore, the oncoprotein mucin 1, known to be up-regulated in human and mouse DCIS, was over-expressed and mislocalized in the activated ductal tissue.

CONCLUSIONS

These results indicate that aberrant NF-κB activation within mammary epithelium can lead to molecular and morphological changes consistent with the earliest stages of breast cancer. Thus, inhibition of NF-κB signaling following acute inflammation or the initial signs of hyperplastic ductal growth could represent an important opportunity for breast cancer prevention.

Abstract 294: A novel cancer therapeutic strategy: inducing cytotoxic functions in tumor-associated macrophages

Macrophages are recognized as an important component of the tumor microenvironment. Previous studies have shown that they promote tumor growth and participate in the initiation and progression of metastatic spread. Methods are being developed to eliminate macrophages from the tumor, thereby inhibiting their negative effects. However, we believe that the best approach would be to transform the tumor-helping macrophages into tumor-killing macrophages that would both eliminate tumor cells directly and re-invigorate other immune cells around them to better fight the tumor. Our data indicates that we have found a way to induce this transformation.

We utilized a novel transgenic mouse model to determine the effects of activating Nuclear Factor Kappa-B (NF-κB) signaling specifically in macrophages in vivo during different stages of tumor progression. Our data shows that activated macrophages not only inhibit primary tumor growth but also reduce tumor cell seeding and colonization of distant organs, such as the lung. This is accomplished at least in part through direct tumor cell killing by the macrophages. We have further modeled this mechanism in vitro through co-culture assays of macrophages and a variety of tumor cell lines, including breast, ovarian, and melanoma. In each case, activation of NF-κB in macrophages induces a tumoricidal phenotype, in which macrophages directly attack the tumor cells significantly depleting them by three days of co-culture. Having established macrophage NF-κB activation as a promising strategy, we have turned our focus to translating these findings into a therapy that can be delivered to patients in the clinic. We are testing two different approaches. The first is liposomal-encapsulated mifamurtide, a synthetic peptide that mimics a component of bacterial cell walls and thus activates NF-κB in macrophages. This drug is approved for use in osteosarcoma patients, and could be rapidly moved into clinical trials if our studies prove its efficacy in other tumor models. We are currently determining the most advantageous liposome formulation and delivery method in the setting of breast and ovarian cancer. The second strategy is to employ novel, polymeric nanoparticles to deliver siRNA against the inhibitor of kappa-B alpha (IκBα) to tumor associated macrophages (TAMs). We have synthesized these particles and determined that they can be safely delivered to mice in vivo. Furthermore, our studies indicate that the nanoparticles are preferentially taken-up by TAMs and that siRNA inhibition of IκBα induces an anti-tumor macrophage phenotype. Taken together, we have generated convincing evidence that activation of NF-κB in macrophages is a promising strategy to convert TAMs into cytotoxic macrophages. We are actively developing novel tools to translate this approach into immunotherapy that could be effective across a wide spectrum of solid tumors and metastatic disease.

Citation Format: Whitney Barham, Oleg Tikhomirov, Ryan Ortega, Jeannette Saskowski, Courtney S. Thompson, Andrew Wilson, Timothy Blackwell, Zahra Mirafzali, Dineo Khabele, Todd Giorgio, Fiona E. Yull. A novel cancer therapeutic strategy: inducing cytotoxic functions in tumor-associated macrophages. [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 294. doi:10.1158/1538-7445.AM2015-294

Myeloid IKKβ promotes antitumor immunity by modulating CCL11 and the innate immune response

Myeloid cells are capable of promoting or eradicating tumor cells and the nodal functions that contribute to their different roles are still obscure. Here, we show that mice with myeloid-specific genetic loss of the NF-κB pathway regulatory kinase IKKβ exhibit more rapid growth of cutaneous and lung melanoma tumors. In a BRAF(V600E/PTEN(-/-)) allograft model, IKKβ loss in macrophages reduced recruitment of myeloid cells into the tumor, lowered expression of MHC class II molecules, and enhanced production of the chemokine CCL11, thereby negatively regulating dendritic-cell maturation. Elevated serum and tissue levels of CCL11 mediated suppression of dendritic-cell differentiation/maturation within the tumor microenvironment, skewing it toward a Th2 immune response and impairing CD8(+) T cell-mediated tumor cell lysis. Depleting macrophages or CD8(+) T cells in mice with wild-type IKKβ myeloid cells enhanced tumor growth, where the myeloid cell response was used to mediate antitumor immunity against melanoma tumors (with less dependency on a CD8(+) T-cell response). In contrast, myeloid cells deficient in IKKβ were compromised in tumor cell lysis, based on their reduced ability to phagocytize and digest tumor cells. Thus, mice with continuous IKKβ signaling in myeloid-lineage cells (IKKβ(CA)) exhibited enhanced antitumor immunity and reduced melanoma outgrowth. Collectively, our results illuminate new mechanisms through which NF-κB signaling in myeloid cells promotes innate tumor surveillance.

Abstract 3010: The role of NF-kappaB in mammary tumor initiation

Nuclear factor kappa B signaling is accepted as a major component of pro-survival signaling within breast cancer cells. However, less is known about how NF-kappaB could contribute to breast tumor initiation. Inflammatory signaling can be activated within the breast by such common factors as obesity, involution following lactation, aging, and psychological stress. Thus, understanding how activated NF-kappaB could lead to the initiation of breast tumors would provide opportunities to develop prevention strategies. We generated a doxycycline-inducible mouse model to study the effects of constitutively active IKK2 on ductal morphogenesis. In this model, Tet-o-cIKK2 mice are crossed with MMTV-rtTA transgenics to target inducible expression specifically to the mammary epithelium. Expression of cIKK2 in transplanted mammary tissue results in enlarged terminal end-buds, increased lateral branching, and intraductal hyperplasia. Transgene induction for only 3 days in a 6 week old female induces filling of ductal lumens, hypercellularity and loss of strict basal/luminal structure. Quantitative PCR of mammary tissue reveals up-regulated markers of macrophage infiltration such as CCL2 and F4/80 and markers of inflammation including Cox-2, TNF-alpha, and CXCL1. Interestingly, constitutive IKK2 activation also results in a decrease in hormone receptor levels (ERα and PR). Immunofluorescent staining shows that activation of classical NF-kappaB increases nuclear p65, as expected. However, nuclear p52 is also increased in transgene positive cells, suggesting that a subset of the effects resulting from activation of classical NF-kappaB are mediated by cross talk with the alternative pathway. Taken together, we find that activation of NF-kappaB in mammary epithelium is sufficient to induce hyperplastic growth and loss of ductal structure. Ongoing studies seek to define what additional factors, such as the right hormonal context, will cause the lesions to progress to malignancy.

Citation Format: Whitney Barham, Oleg Tikhomirov, Lianyi Chen, Ryan Ortega, Halina Onishko, Linda Connelly, Fiona E. Yull. The role of NF-kappaB in mammary tumor initiation. [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 3010. doi:10.1158/1538-7445.AM2014-3010

Abstract 3630: Immunoengineering of tumor associated macrophages using targeted, siRNA delivering nanoparticles

Tumor associated macrophages (TAMs) can modify the tumor microenvironment to create a pro-tumor niche. Dysregulation of NF-κB signaling is implicated in creating a pro-tumor phenotype in TAMs. NF-κB signaling consists of a classical pathway and a less understood alternative pathway. Suppression of NF-κB activation in TAMs is predicted to decrease local smoldering inflammation and inhibit the pro-tumor TAM phenotype. However, recent studies have reported anti-tumor macrophage behavior induced by activation of the classical NF-κB pathway. We have successfully used mannosylated polymer nanoparticles (Mn-NP) to deliver siRNA for RNAi of NF-κB proteins in bone marrow derived macrophages (BMDMs) and mouse TAMs in vivo. Mannose serves as a macrophage targeting ligand via the mannose receptor (CD206). This work aims to characterize these nanomaterials for targeted delivery of functional nucleic acid sequences into macrophages in vitro and in vivo. These studies will also use the Mn-NP to investigate the effects of specific manipulation of NF-κB activation on macrophage phenotype.

Mn-NPs are micelles formed by self-assembly of triblock polymers with a poly(BMA-co-PAA-co-DMAEMA) core, a DMAEMA siRNA condensing block, and an azide-containing outer block for further functionalization. Alkyne functionalized mannose is then “clicked” on the end of the polymer and presented on the micellar surface. In vitro cell studies carried out with BMDMs from mice that express luciferase as a reporter of total NF-κB activity. Mn-NP delivery of siRNA (50 nM for 24 hrs) against each of several NF-κB pathway proteins confirms efficacious knockdown of total NF-κB activity, comparable to transfection with the commercial agent Lipofectamine. Mn-NPs are also highly biocompatible in vitro and exhibit no significant liver or kidney toxicity in mice at doses of 5 mg/kg. The mannosylated carrier effectively delivers cy3 fluorescently labeled nucleotides to TAMs in multiple model systems, including in primary mammary tumors arising spontaneously in polyoma mice and an implanted ovarian tumor model, . Currently, studies are focused on a potential therapeutic strategy that involves RNAi of an inhibitor of the classical NF-κB pathway, IκBα, in order to strategically activate the classical pathway in TAMs. Quantitative RT-PCR analysis of macrophages treated with Mn-NP formulated with siRNA against IκBα show a decrease in M2 markers, a decrease in smoldering inflammation associated cytokines, and an increase in immune cell recruiting chemokines.

Citation Format: Ryan Ortega, Whitney Barham, Oleg Tikhomirov, Kavya Sharman, Fiona Yull, Todd Giorgio. Immunoengineering of tumor associated macrophages using targeted, siRNA delivering nanoparticles. [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 3630. doi:10.1158/1538-7445.AM2014-3630

Tracking NF-κB activity in tumor cells during ovarian cancer progression in a syngeneic mouse model

Background

Nuclear factor-kappa B (NF-kappaB) signaling is an important link between inflammation and peritoneal carcinomatosis in human ovarian cancer. Our objective was to track NF-kappaB signaling during ovarian cancer progression in a syngeneic mouse model using tumor cells stably expressing an NF-kappaB reporter.

Methods

ID8 mouse ovarian cancer cells stably expressing an NF-kappaB-dependent GFP/luciferase (NGL) fusion reporter transgene (ID8-NGL) were generated, and injected intra-peritoneally into C57BL/6 mice. NGL reporter activity in tumors was non-invasively monitored by bioluminescence imaging and measured in luciferase assays in harvested tumors. Ascites fluid or peritoneal lavages were analyzed for inflammatory cell and macrophage content, and for mRNA expression of M1 and M2 macrophage markers by quantitative real-time RT-PCR. 2-tailed Mann-Whitney tests were used for measuring differences between groups in in vivo experiments.

Results

In ID8-NGL cells, responsiveness of the reporter to NF-kappaB activators and inhibitors was confirmed in vitro and in vivo. ID8-NGL tumors in C57BL/6 mice bore histopathological resemblance to human high-grade serous ovarian cancer and exhibited similar peritoneal disease spread. Tumor NF-kappaB activity, measured by the NGL reporter and by western blot of nuclear p65 expression, was markedly elevated at late stages of ovarian cancer progression. In ascites fluid, macrophages were the predominant inflammatory cell population. There were elevated levels of the M2-like pro-tumor macrophage marker, mannose-receptor, during tumor progression, and reduced levels following NF-kappaB inhibition with thymoquinone.

Conclusions

Our ID8-NGL reporter syngeneic model is suitable for investigating changes in tumor NF-kappaB activity during ovarian cancer progression, how NF-kappaB activity influences immune cells in the tumor microenvironment, and effects of NF-kappaB-targeted treatments in future studies.

Targeting the Wnt pathway in synovial sarcoma models

Synovial sarcoma is an aggressive soft-tissue malignancy of children and young adults, with no effective systemic therapies. Its specific oncogene, SYT-SSX (SS18-SSX), drives sarcoma initiation and development. The exact mechanism of SYT-SSX oncogenic function remains unknown. In an SYT-SSX2 transgenic model, we show that a constitutive Wnt/β-catenin signal is aberrantly activated by SYT-SSX2, and inhibition of Wnt signaling through the genetic loss of β-catenin blocks synovial sarcoma tumor formation. In a combination of cell-based and synovial sarcoma tumor xenograft models, we show that inhibition of the Wnt cascade through coreceptor blockade and the use of small-molecule CK1α activators arrests synovial sarcoma tumor growth. We find that upregulation of the Wnt/β-catenin cascade by SYT-SSX2 correlates with its nuclear reprogramming function. These studies reveal the central role of Wnt/β-catenin signaling in SYT-SSX2-induced sarcoma genesis, and open new venues for the development of effective synovial sarcoma curative agents.

SIGNIFICANCE

Synovial sarcoma is an aggressive soft-tissue cancer that afflicts children and young adults, and for which there is no effective treatment. The current studies provide critical insight into our understanding of the pathogenesis of SYT–SSX-dependent synovial sarcoma and pave the way for the development of effective therapeutic agents for the treatment of the disease in humans.

Abstract 1545: Education of macrophages through modulation of NF-kappaB: an opportunity for targeted therapy

Macrophages are a plastic cell type, capable of adapting to numerous signals within their environment. As part of the innate immune system, macrophages were traditionally considered anti-tumor (M1), but it has been well established that macrophages can also help to create a pro-tumor, pro-metastatic tumor niche (M2). NF-κB transcription factors can regulate both pro- (MMP's, VEGF) and anti-tumor (iNOS) downstream targets within macrophages, suggesting that modulation of NF-κB may play a role in the two different macrophage phenotypes. However, our understanding of NF-κB signaling specifically within macrophages during tumor progression is limited. To this end, we have developed murine transgenic models that enable us to induce expression of an activator or dominant inhibitor of NF-κB in macrophages by adding doxycycline to the drinking water of mice. We have combined these novel transgenics with the polyoma model of mammary cancer for our studies.

We have recently shown that activation of NF-κB in macrophages significantly limits metastasis in a tail vein model of tumor progression. In this model, constitutive IKK2 activity within macrophages leads to an anti-tumor immune response including altered immune cell populations within the lung microenvironment, changes in chemokine and cytokine expression and rapid killing of tumor cells during the seeding phase mediated by reactive oxygen species. Our current work has extended these findings to an orthotopic mammary tumor model. Again, we find that activation of NF-κB in macrophages results in decreased primary tumor growth and decreased tumor seeding into the blood. To model this activation in vitro, we have utilized immortalized bone marrow derived macrophages from IκBα knock-out mice compared to a wild type line. IκBα KO macrophages display changes in morphology and adhesion relative to wild type macrophages. This correlates with increased cytotoxic behavior in co-culture with polyoma tumor cells, mirroring the in vivo phenotype of the cIKK2 expressing macrophages. Given these findings, we believe that targeted activation of NF-κB signaling in macrophages could be harnessed to overcome the education of macrophages by tumor cells, and could be exploited as a novel targeted therapy.

Citation Format: Whitney Barham, Oleg Tikhomirov, Lianyi Chen, Ryan Ortega, Linda Gleaves, Halina Onishko, Taylor Sherrill, Linda Connelly, Timothy S. Blackwell, Fiona E. Yull. Education of macrophages through modulation of NF-kappaB: an opportunity for targeted therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1545. doi:10.1158/1538-7445.AM2013-1545

Abstract 4954: Opposing effects of the NF-kappaB inhibitor thymoquinone in a syngeneic mouse model of ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy. Most women are diagnosed with advanced disease characterized by widespread peritoneal carcinomatosis and abdominal ascites. Activation of inflammatory processes via nuclear factor-kappa B (NF-κB) is involved in ovarian cancer progression and linked to chemotherapy resistance. The potential of NF-κB inhibitors to suppress tumor progression and sensitize tumor cells to platinum chemotherapy has led to their successful use in preclinical tumor models. One such inhibitor is thymoquinone (TQ), a component of black seed oil, widely used in traditional medicine. However, most NF-κB inhibitors including bortezomib have had disappointing clinical results in the treatment of solid tumors. It is possible that NF-κB inhibition in inflammatory cells such as macrophages in the peritoneal cavity may underlie the relatively poor efficacy and toxicity observed in patients. Therefore, this study aimed to determine the effects of TQ on ovarian cancer progression in the immunocompetent host. ID8 mouse ovarian cancer cells expressing the NF-κB-dependent GFP/luciferase (NGL) fusion reporter transgene (ID8-NGL) were injected intraperitoneally (IP) into C57BL/6 mice. Reporter activity was visualized by bioluminescence imaging. TQ or PBS vehicle (VEH) were injected IP thrice weekly from day 30-60 after tumor cell injection. Mice were then sacrificed, ascites collected and tumors harvested. In vitro studies confirmed that TQ inhibited NF-κB activity in ID8-NGL cells, inhibited cell growth, and exerted co-operative inhibitory effects with cisplatin on cell growth. Consistent with the observed in vitro growth inhibition, TQ induced approximately 30% reduction in tumor cells expressing the proliferation marker Ki67 compared to VEH tumors in vivo. However, there was no overall difference in tumor burden (peritoneal and mesenteric tumor nodules). Strikingly, the volume of ascites collected from TQ mice was 5-fold higher than VEH mice, and cytospin analysis of ascites showed that TQ induced a 4-fold increase in the number of macrophages, suggesting an elevated inflammatory response. TQ also increased NF-κB reporter activity by 50% compared to levels in VEH mice. These data suggest that TQ exerts both anti- and pro-tumorigenic effects, likely mediated through NF-κB inhibition in tumor cells and host inflammatory cells, respectively. However, the net effect of treatment is deleterious (increased ascites). These results caution that treating ovarian cancer patients with systemic NF-κB inhibitors may have unanticipated adverse effects, and that a greater understanding of the effects of NF-κB inhibition is necessary before performing combination studies with platinum agents such as cisplatin.

Citation Format: Andrew J. Wilson, Jeanette Saskowski, Whitney Barham, Lianyi Chen, Dineo Khabele, Fiona Yull. Opposing effects of the NF-kappaB inhibitor thymoquinone in a syngeneic mouse model of ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4954. doi:10.1158/1538-7445.AM2013-4954

Abstract 3981: Reprogramming tumor associated macrophages toward an anti-tumor phenotype by targeting the NF-κB pathway using novel targeted nanotherapeutics

Tumor associated macrophages (TAMs) can modify the tumor microenvironment to create an inflammatory, pro-tumor niche. Activation of the NF-κB pathway has been implicated in creating a pro-tumor phenotype in TAMs. Manipulation of TAM phenotype is a new approach to engage anticancer immunity, but has been limited by a lack of methods capable of therapeutic delivery to TAMs in vivo. We have successfully utilized mannosylated polymer nanoparticles capable of disrupting the endosomal compartment to deliver siRNA for RNAi of NF-κB proteins into bone marrow derived macrophages (BMDMs) derived from transgenic mice with a GFP/Luciferase reporter of NF-κB activity (NGL). In in vitro studies, the nanoparticles are comparable to commercial transfection agents using both gene and protein level readouts for knockdown. The transfection protocol utilizing these novel vehicles has been optimized with respect to transfection time, siRNA dose, and siRNA:polymer ratio with the intent to inform in vivo experiments. The presence of serum does not significantly affect transfection efficiency in vitro, presumably due to an almost neutral particle surface charge. Preliminary in vivo studies have revealed no significant particle toxicity. Delivering siRNA specific to the p52/p100 protein in the alternative pathway achieves knockdown of total NF-κB activity by approximately 80% in NGL BMDMs stimulated by TNF-α. By targeting proteins in the classical pathway, we have decreased total NF-κB activity by approximately 50% in the same model. While inhibition of NF-κB activity may be desirable in some contexts, we recently reported that induced activation of NF-κB in macrophages can result in anti-tumor activity. We have delivered a liposomal formulation of muramyl tripeptide (Mifamurtide), a synthetic derivative of a bacterial cell wall peptide and an activator of macrophages, to NGL BMDMs. Mifamurtide delivery increases both NF-κB activity, and the production of reactive oxygen species, indicating a preliminary mechanistic explanation for the therapeutic potential of NF-κB activation. Mifamurtide is used clinically in the European Union to treat osteosarcoma, potentially providing an avenue for rapid clinical translation of NF-κB modulating therapy for other tumor types. However, Mifamurtide has the potential to activate multiple pathways simultaneously. A more elegant approach would be to target knockdown of an NF-κB inhibitor to macrophages to mediate pathway specific activation. In preliminary studies we have demonstrated the ability to increase total NF-κB activity by treating NGL macrophages with nanoparticles carrying siRNA against the IκBα inhibitor of NF-κB. Our data provides evidence that delivering siRNA specifically to macrophages to modulate their functions using nanoparticles has potential as a therapeutic approach to cancer treatment.

Citation Format: Ryan A. Ortega, Whitney Barham, Bharat Kumar, Shann S. Yu, Fiona Yull, Todd D. Giorgio. Reprogramming tumor associated macrophages toward an anti-tumor phenotype by targeting the NF-κB pathway using novel targeted nanotherapeutics. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3981. doi:10.1158/1538-7445.AM2013-3981

Intraductal injection of LPS as a mouse model of mastitis: signaling visualized via an NF-κB reporter transgenic

Animal models of human disease are necessary in order to rigorously study stages of disease progression and associated mechanisms, and ultimately, as pre-clinical models to test interventions. In these methods, we describe a technique in which lipopolysaccharide (LPS) is injected into the lactating mouse mammary gland via the nipple, effectively modeling mastitis, or inflammation, of the gland. This simulated infection results in increased nuclear factor kappa B (NF-κB) signaling, as visualized through bioluminescent imaging of an NF-κB luciferase reporter mouse. Our ultimate goal in developing these methods was to study the inflammation associated with mastitis in the lactating gland, which often includes redness, swelling, and immune cell infiltration. Therefore, we were keenly aware that incision or any type of wounding of the skin, the nipple, or the gland in order to introduce the LPS could not be utilized in our methods since the approach would likely confound the read-out of inflammation. We also desired a straight-forward method that did not require specially made hand-drawn pipettes or the use of micromanipulators to hold these specialized tools in place. Thus, we determined to use a commercially available insulin syringe and to inject the agent into the mammary duct of an intact nipple. This method was successful and allowed us to study the inflammation associated with LPS injection without any additional effects overlaid by the process of injection. In addition, this method also utilized an NF-κB luciferase reporter transgenic mouse and bioluminescent imaging technology to visually and quantitatively show increased NF-κB signaling within the LPS-injected gland. These methods are of interest to researchers of many disciplines who wish to model disease within the lactating mammary gland, as ultimately, the technique described here could be utilized for injection of a number of substances, and is not limited to only LPS.

Abstract 320: Investigating the patterns of nuclear factor-kappa B activity in the host-tumor microenvironment during ovarian cancer progression

Most women diagnosed with ovarian cancer initially present with metastatic disease characterized by peritoneal implants and ascites. Activation of inflammatory processes mediated by nuclear factor-kappa B (NF-κB) is thought to be critical to the distinct clinical pattern of spread of ovarian tumors. However, the relative contribution of NF-κB activity in tumor cells and host inflammatory cells to ovarian cancer progression remains unknown. Therefore, our goal was to develop and characterize model systems to investigate NF-κB activity in these cell populations during ovarian tumorigenesis. To study the host NF-κB response, ID8 mouse ovarian cancer cells were injected intra-peritoneally into C57BL/6 mice carrying an NF-κB-dependent green fluorescent protein (GFP)/luciferase fusion transgene (NGL). In a reciprocal approach, ID8 cells stably expressing the NGL reporter (ID8-NGL) were injected into wild-type C57BL/6 mice to investigate NF-κB activation in the developing tumor. Non-invasive imaging of the mice was performed by bioluminescence imaging (BLI) of the NGL reporter and by positron emission tomography (PET-CT) imaging of abdominal tumor burden. Preliminary experiments confirmed these models were highly reproducible, with peritoneal-wide tumor dissemination accompanied by the onset of late-stage, irreversible ascites. Mice injected with ID8-NGL cells showed greater than 100-fold increase in NF-κB reporter activity during tumor progression. There was a modest overall decrease in abdominal NF-κB activity over time in ID8-injected NGL mice, although the possibility of “masking” effects of the ascites fluid on bioluminescence, and NF-κB activity in specific host cell populations, need to be elaborated. These models will allow us to define the patterns of NF-κB activity in the host-tumor microenvironment during ovarian cancer progression, and will provide a powerful platform for future preclinical investigation of novel therapeutic agents targeting NF-κB in ovarian cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 320. doi:1538-7445.AM2012-320

Abstract 5262: Disruption of alternative and classical NF-kappaB signaling patterns: Connections to branching morphogenesis and mammary tumorigenesis

NF-kappaB transcription factors including p65 (RelA), RelB, p105/p50, and p100/p52 play roles in mammary development and tumorigenesis. While most studies have focused on classical NF-kappaB signaling (p65/p50), alternative NF-kappaB signaling is elevated in human primary breast tumors and in human breast cancer cell lines. In addition, we have reported that overexpression of p100 within the mouse mammary epithelium during pregnancy and lactation led to ductal thickening and hyperplastic foci. To determine the contribution of alternative NF-kappaB signaling to mammary development and tumorigenesis, we have developed murine transgenic models that enable us to inducibly express activators or inhibitors of classical or alternative NF-kappaB signaling in the mammary epithelium by adding doxycycline to the drinking water of mice. Modulation of both the classical and alternative pathways will enable us to determine the roles that each arm plays independently or synergistically. Using immunoflourescent staining we have identified distinct patterns of expression of the alternative and classical pathways in mammary epithelium, a previously undescribed phenomenon. Classical p65 signaling was found within the luminal cell population and p100/p52 signaling was observed almost exclusively within the basal cell layer. Upon induction of constitutively activated IKK2 or a dominant negative IKBalpha, two regulators of the classical NF-κB pathway, alterations in branching morphogenesis were observed within the developing virgin gland. These branching phenotypes were associated with a break down in the previously observed classical/alternative signaling pattern, as luminal cells were now expressing low levels of p100/p52. Furthermore, this patterning is disrupted during the development of polyoma middle T oncogene induced tumors in which we also observe alternative signaling no longer confined to the basal layer. Ongoing experiments with our newest transgenic model are designed to determine the effects of inducing alternative signaling, through overexpression of p52, within the mammary epithelium. Our models may reveal novel roles for the alternative NF-kappaB pathway in maintaining the basal/luminal structure of mammary epithelial ducts and connect aberrant p100/p52 signaling to tumor progression, potentially identifying a novel therapeutic target.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5262. doi:1538-7445.AM2012-5262

Abstract 2841: Inducible modulation of NF-kappaB in macrophages reveals that timing of intervention may be critical to therapeutic outcome during mammary tumorigenesis

Elevated levels of NF-kappaB signaling are associated with multiple cancers. Therefore, it is not surprising that inhibitors of NF-kappaB are being investigated as potential therapeutics. While extensive efforts are being made to identify inhibitors there is less focus on investigating the effects of inhibition in specific cell types and during defined stages of tumor progression. We have developed murine transgenic models that enable us to induce expression of an activator or inhibitor of NF-kappaB in macrophages, by adding doxycycline to the drinking water of mice. We have combined these with the Polyoma model of mammary cancer to investigate the effects of modulation of NF-kappaB signaling specifically within macrophages. Given several recent publications we were predicting that activation of NF-kappaB would have pro-tumor effects. However, using a tail vein injection model, our data identifies a stage during progression in which activation of NF-kappaB in macrophages significantly limits metastasis. Activation of NF-kappaB alters immune cell populations and results in rapid killing of tumor cells during the seeding phase. In this model inhibition of NF-kappaB in macrophages during this critical stage of metastasis is pro-tumor. This suggests that while inhibition of NF-kappaB at later stages of tumor progression may have therapeutic benefit, inhibition during the seeding phase my lead to the opposite effect. Our studies highlight the importance of continued investigation into aspects of cell specificity and timing that may change the potential outcome of a clinical trial using NF-kappaB inhibitors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2841. doi:10.1158/1538-7445.AM2011-2841

Inhibition of NF-kappa B activity in mammary epithelium increases tumor latency and decreases tumor burden

The transcription factor nuclear factor kappa B (NF-κB) is activated in human breast cancer tissues and cell lines. However, it is unclear whether NF-κB activation is a consequence of tumor formation or a contributor to tumor development.

We developed a doxycycline-inducible mouse model, termed DNMP, to inhibit NF-κB activity specifically within the mammary epithelium during tumor development in the polyoma middle T oncogene (PyVT) mouse mammary tumor model. DNMP females and PyVT littermate controls were treated with doxycycline from 4 to 12 weeks of age. We observed an increase in tumor latency and a decrease in final tumor burden in DNMP mice compared to PyVT controls. A similar effect with treatment from 8 to 12 weeks indicates that outcome is independent of effects on postnatal virgin ductal development. In both cases, DNMP mice were less likely to develop lung metastases than controls. Treatment from 8 to 9 weeks was sufficient to impact primary tumor formation. Inhibition of NF-κB increases apoptosis in hyperplastic stages of tumor development and decreases proliferation at least in part by reducing CyclinD1 expression. To test the therapeutic potential of NF-κB inhibition, we generated palpable tumors by orthotopic injection of PyVT cells and then treated systemically with the NF-κB inhibitor thymoquinone (TQ). TQ treatment resulted in a reduction in tumor volume and weight as compared to vehicle-treated control. This data indicates that epithelial NF-κB is an active contributor to tumor progression and demonstrates that inhibition of NF-κB could have a significant therapeutic impact even at later stages of mammary tumor progression.

Activation of nuclear factor kappa B in mammary epithelium promotes milk loss during mammary development and infection

We investigated whether nuclear factor kappa B (NF-kappaB), which exhibits a regulated pattern of activity during murine mammary gland development, plays an important role during lactation and involution, when milk production ceases and the gland undergoes apoptosis and re-modeling. We generated a doxycycline inducible transgenic mouse model to activate NF-kappaB specifically in the mammary epithelium through expression of a constitutively active form of IKK2, the upstream kinase in the classical NF-kappaB signaling cascade. We found that activation of NF-kappaB during involution resulted in a more rapid reduction in milk levels and increased cleavage of caspase-3, an indicator of apoptosis. We also found that activation of NF-kappaB during lactation with no additional involution signals had a similar effect. The observation that NF-kappaB is a key regulator of milk production led us to investigate the role of NF-kappaB during mastitis, an infection of the mammary gland in which milk loss is observed. Mammary gland injection of E. coli LPS resulted in activation of NF-kappaB and milk loss during lactation. This milk loss was decreased by selective inhibition of NF-kappaB in mammary epithelium. Together, our data reveal that activation of NF-kappaB leads to milk clearance in the lactating mammary gland. Therefore, targeting of NF-kappaB signaling may prove therapeutic during mastitis in humans and could be beneficial for the dairy industry, where such infections have a major economic impact.