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.

Non-invasive immunoPET imaging of PD-L1 using anti-PD-L1-B11 in breast cancer and melanoma tumor model.

INTRODUCTION: Immunotherapy targeting PD-1/PD-L1 immune checkpoint inhibition (ICI) is efficacious in various solid and hematologic malignancies. However, the response rate to PD-1/PD-L1 therapy is only 15-35%. To obtain optimal clinical response to ICI therapies, a reliable assessment of tumor PD-L1 expression is needed to select appropriate patients, and a non-invasive imaging-based assessment of PD-L1 expression is critically needed. Although radiolabeled PET probes based on PD-L1 targeted therapeutic antibodies (e.g. atezolizumab) have shown encouraging results, there is concern that residual therapeutic antibody may compete for binding with the radiotracer thereby compromising imaging studies that follow treatment. METHODS AND RESULTS: In this study, we used novel anti-PD-L1-B11 clone antibody known to bind to a different epitope of PD-L1 than the therapeutic antibodies to avoid potential saturation effects. The anti-PD-L1-B11 clone was radiolabeled with zirconium-89 and evaluated to detect PD-L1 expression in various in vitro and in vivo cancer model systems in comparison with [89Zr]Zr-DFO-NCS-atezolizumab. In vitro binding parameters of anti-PD-L1-B11 were like those of atezolizumab. [89Zr]Zr-DFO-NCS-anti-PD-L1-B11 clone showed favorable properties to [89Zr]Zr-DFO-NCS-atezolizumab in an in vivo breast cancer tumor model system with higher uptake in PD-L1 expressing tumors. CONCLUSION: Our data demonstrates that [89Zr]Zr-DFO-NCS-anti-PD-L1-B11 exhibits excellent imaging properties for the assessment PD-L1 expression. The independent binding site of anti-PD-L1-B11 relative to therapeutic anti-PD-L1 antibodies may be advantageous for anti-PD-L1 therapy monitoring.

Increased canonical NF-kappaB signaling specifically in macrophages is sufficient to limit tumor progression in syngeneic murine models of ovarian cancer.

BACKGROUND: New treatment options for ovarian cancer are urgently required. Tumor-associated macrophages (TAMs) are an attractive target for therapy; repolarizing TAMs from M2 (pro-tumor) to M1 (anti-tumor) phenotypes represents an important therapeutic goal. We have previously shown that upregulated NF-kappaB (NF-κB) signaling in macrophages promotes M1 polarization, but effects in the context of ovarian cancer are unknown. Therefore, we aimed to investigate the therapeutic potential of increasing macrophage NF-κB activity in immunocompetent mouse models of ovarian cancer. METHODS: We have generated a transgenic mouse model, termed IKFM, which allows doxycycline-inducible overexpression of a constitutively active form of IKK2 (cIKK2) specifically within macrophages. The IKFM model was used to evaluate effects of increasing macrophage NF-κB activity in syngeneic murine TBR5 and ID8-Luc models of ovarian cancer in two temporal windows: 1) in established tumors, and 2) during tumor implantation and early tumor growth. Tumor weight, ascites volume, ascites supernatant and cells, and solid tumor were collected at sacrifice. Populations of macrophages and T cells within solid tumor and/or ascites were analyzed by immunofluorescent staining and qPCR, and soluble factors in ascitic fluid were analyzed by ELISA. Comparisons of control versus IKFM groups were performed by 2-tailed Mann-Whitney test, and a P-value < 0.05 was considered statistically significant. RESULTS: Increased expression of the cIKK2 transgene in TAMs from IKFM mice was confirmed at the mRNA and protein levels. Tumors from IKFM mice, regardless of the timing of doxycycline (dox) administration, demonstrated greater necrosis and immune infiltration than control tumors. Analysis of IKFM ascites and tumors showed sustained shifts in macrophage populations away from the M2 and towards the anti-tumor M1 phenotype. There were also increased tumor-infiltrating CD3+/CD8+ T cells in IKFM mice, accompanied by higher levels of CXCL9, a T cell activating factor secreted by macrophages, in IKFM ascitic fluid. CONCLUSIONS: In syngeneic ovarian cancer models, increased canonical NF-κB signaling in macrophages promoted anti-tumor TAM phenotypes and increased cytotoxic T cell infiltration, which was sufficient to limit tumor progression. This may present a novel translational approach for ovarian cancer treatment, with the potential to increase responses to T cell-directed therapy in future studies.

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.

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.

Paradox-driven adventures in the development of cancer immunology and immunotherapy.

After more than one hundred years of documented trials, immunotherapy has become a standard of care in the treatment of human cancer. Much of the knowledge that led to recent breakthroughs seems quite logical from today's point of view. However, what we now cite as facts were originally considered paradoxes, meaning something contrary to expectations or perceived opinion at the time. In order to make gains in the field of immunotherapy, one had to be willing to confront ideas and concepts that seemed to contradict one another, and reconcile how each could be true. This is what led to new knowledge and advances. Here, we highlight some of these paradoxes and the milestone discoveries that followed, each one critical for our understanding of immune checkpoint pathways. By outlining some of the steps that we took and the challenges that we overcame, we hope to inspire and encourage future generations of researchers to confront the paradoxes that still permeate the field.

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.

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.

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.

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.

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 IKKß 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.

NF-κB-dependent airway inflammation triggers systemic insulin resistance.

Inflammatory lung diseases (e.g., pneumonia and acute respiratory distress syndrome) are associated with hyperglycemia, even in patients without a prior diagnosis of Type 2 diabetes. It is unknown whether the lung inflammation itself or the accompanying comorbidities contribute to the increased risk of hyperglycemia and insulin resistance. To investigate whether inflammatory signaling by airway epithelial cells can induce systemic insulin resistance, we used a line of doxycycline-inducible transgenic mice that express a constitutive activator of the NF-κB in airway epithelial cells. Airway inflammation with accompanying neutrophilic infiltration was induced with doxycycline over 5 days. Then, hyperinsulinemic-euglycemic clamps were performed in chronically catheterized, conscious mice to assess insulin action. Lung inflammation decreased the whole body glucose requirements and was associated with secondary activation of inflammation in multiple tissues. Metabolic changes occurred in the absence of hypoxemia. Lung inflammation markedly attenuated insulin-induced suppression of hepatic glucose production and moderately impaired insulin action in peripheral tissues. The hepatic Akt signaling pathway was intact, while hepatic markers of inflammation and plasma lactate were increased. As insulin signaling was intact, the inability of insulin to suppress glucose production in the liver could have been driven by the increase in lactate, which is a substrate for gluconeogenesis, or due to an inflammation-driven signal that is independent of Akt. Thus, localized airway inflammation that is observed during inflammatory lung diseases can contribute to systemic inflammation and insulin resistance.

Thymoquinone enhances cisplatin-response through direct tumor effects in a syngeneic mouse model of ovarian cancer.

BACKGROUND: Ovarian cancer is the most lethal gynecologic malignancy characterized by the frequent development of resistance to platinum chemotherapy. Finding new drug combinations to overcome platinum resistance is a key clinical challenge. Thymoquinone (TQ) is a component of black seed oil that exerts multiple anti-tumorigenic effects on cells, including inhibition of NF-κB and promotion of DNA damage. We aimed to determine whether TQ enhances cisplatin cytotoxicity in cultured ovarian cancer cells and in an established murine syngeneic model of ovarian cancer. METHODS: Ovarian cancer cell viability in vitro was measured by sulforhodamine B (SRB) assays, and drug interactions tested for synergism by isobologram analysis. ID8-NGL mouse ovarian cancer cells stably expressing an NF-κB reporter transgene were injected intra-peritoneally into C57BL/6 mice. After 30 day TQ and/or cisplatin treatment, we measured the following indices: tumor burden (ascites volume, number of peritoneal implants and mesenteric tumor mass); NF-κB reporter activity (luciferase assay); protein expression of the double-strand DNA break marker, pH2AX(ser139), the proliferation markers, Ki67/mib-1 and PCNA, and the apoptosis markers, cleaved caspase-3, cleaved PARP and Bax; and mRNA expression of NF-κB targets, TNF-α and IL-1ß. Two-tailed Mann-Whitney tests were used for measuring differences between groups in mouse experiments. RESULTS: In SRB assays, TQ and cisplatin synergized in ID8-NGL cells. In mice, cisplatin significantly reduced cell proliferation and increased apoptosis in tumors, resulting in decreased overall tumor burden. Combining TQ with cisplatin further decreased these indices, indicating co-operative effects between the drugs. TQ treatment promoted cisplatin-induced pH2AX expression in cultured cells and in tumors. While NF-κB inhibition by TQ induced anti-tumor effects in vitro, we made the unexpected observation that TQ alone increased both tumor NF-κB activity and formation of ascites in vivo. CONCLUSIONS: TQ enhanced cisplatin-mediated cytoxicity in ovarian cancer cells in vitro and in a mouse syngeneic model, effects associated with increased DNA damage. However, our results strongly caution that TQ treatment alone may have an overall deleterious effect in the immunocompetent host through stimulation of ascites. Since TQ is a potential candidate for future clinical trials in ovarian cancer patients, this finding has considerable potential relevance to the clinic.

Biocompatible mannosylated endosomal-escape nanoparticles enhance selective delivery of short nucleotide sequences to tumor associated macrophages.

Tumor associated macrophages (TAMs) can modify the tumor microenvironment to create a pro-tumor niche. Manipulation of the TAM phenotype is a novel, potential therapeutic approach to engage anti-cancer immunity. siRNA is a molecular tool for knockdown of specific mRNAs that is tunable in both strength and duration. The use of siRNA to reprogram TAMs to adopt an immunogenic, anti-tumor phenotype is an attractive alternative to ablation of this cell population. One current difficulty with this approach is that TAMs are difficult to specifically target and transfect. We report here successful utilization of novel mannosylated polymer nanoparticles (MnNP) that are capable of escaping the endosomal compartment to deliver siRNA to TAMs in vitro and in vivo. Transfection with MnNP-siRNA complexes did not significantly decrease TAM cell membrane integrity in culture, nor did it create adverse kidney or liver function in mice, even at repeated doses of 5 mg kg(-1). Furthermore, MnNP effectively delivers labeled nucleotides to TAMs in mice with primary mammary tumors. We also confirmed TAM targeting in the solid tumors disseminated throughout the peritoneum of ovarian tumor bearing mice following injection of fluorescently labeled MnNP-nucleotide complexes into the peritoneum. Finally, we show enhanced uptake of MnNP in lung metastasis associated macrophages compared to untargeted particles when using an intubation delivery method. In summary, we have shown that MnNP specifically and effectively deliver siRNA to TAMs in vivo.

Myeloid IKKß 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 IKKß exhibit more rapid growth of cutaneous and lung melanoma tumors. In a BRAF(V600E/PTEN(-/-)) allograft model, IKKß 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 IKKß 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 IKKß were compromised in tumor cell lysis, based on their reduced ability to phagocytize and digest tumor cells. Thus, mice with continuous IKKß signaling in myeloid-lineage cells (IKKß(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.