Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity

Cancer-Associated Myeloid Regulatory Cells

Myeloid cells are critically involved in the pathophysiology of cancers. In the tumor microenvironment (TME), they comprise tumor-associated macrophages (TAMs), neutrophils (TANs), dendritic cells, and myeloid-derived suppressor cells, which are further subdivided into a monocytic subset and a granulocytic subset. Some of these myeloid cells, in particular TAMs and TANs, are divided into type 1 or type 2 cells, according to the paradigm of T helper type 1 or type 2 cells. Type 1-activated cells are generally characterized as cells that aid tumor rejection, while all other myeloid cells are shown to favor tumor progression. Moreover, these cells are often at the basis of resistance to various therapies. Much research has been devoted to study the biology of myeloid cells. This endeavor has proven to be challenging, as the markers used to categorize myeloid cells in the TME are not restricted to particular subsets. Also from a functional and metabolic point of view, myeloid cells share many features. Finally, myeloid cells are endowed with a certain level of plasticity, which further complicates studying them outside their environment. In this article, we challenge the exclusive use of cell markers to unambiguously identify myeloid cell subsets in the TME. We further propose to divide myeloid cells into myeloid regulatory or stimulatory cells according to their pro- or antitumor function, because we contend that for therapeutic purposes it is not targeting the cell subsets but rather targeting their protumor traits; hence, myeloid regulatory cells will push antitumor immunotherapy to the next level.

IL15 Agonists Overcome the Immunosuppressive Effects of MEK Inhibitors

Many signal transduction inhibitors are being developed for cancer therapy target pathways that are also important for the proper function of antitumor lymphocytes, possibly weakening their therapeutic effects. Here we show that most inhibitors targeting multiple signaling pathways have especially strong negative effects on T-cell activation at their active doses on cancer cells. In particular, we found that recently approved MEK inhibitors displayed potent suppressive effects on T cells in vitro However, these effects could be attenuated by certain cytokines that can be administered to cancer patients. Among them, clinically available IL15 superagonists, which can activate PI3K selectively in T lymphocytes, synergized with MEK inhibitors in vivo to elicit potent and durable antitumor responses, including by a vaccine-like effect that generated resistance to tumor rechallenge. Our work identifies a clinically actionable approach to overcome the T-cell-suppressive effects of MEK inhibitors and illustrates how to reconcile the deficiencies of signal transduction inhibitors, which impede desired immunologic effects in vivo Cancer Res; 76(9); 2561-72. ©2016 AACR.

Multifunctional nanoparticles for cancer immunotherapy

During the last decades significant progress has been made in the field of cancer immunotherapy. However, cancer vaccines have not been successful in clinical trials due to poor immunogenicity of antigen, limitations of safety associated with traditional systemic delivery as well as the complex regulation of the immune system in tumor microenvironment. In recent years, nanotechnology-based delivery systems have attracted great interest in the field of immunotherapy since they provide new opportunities to fight the cancer. In particular, for delivery of cancer vaccines, multifunctional nanoparticles present many advantages such as targeted delivery to immune cells, co-delivery of therapeutic agents, reduced adverse outcomes, blocked immune checkpoint molecules, and amplify immune activation via the use of stimuli-responsive or immunostimulatory materials. In this review article, we highlight recent progress and future promise of multifunctional nanoparticles that have been applied to enhance the efficiency of cancer vaccines.

Activation of the MDA-5-IPS-1 Viral Sensing Pathway Induces Cancer Cell Death and Type I IFN-Dependent Antitumor Immunity

Melanoma differentiation-associated gene 5 (MDA-5, IFIH1), a cytosolic innate pattern recognition receptor, functions as a first line of defense against viral infection by sensing double-stranded RNA. Ectopic expression of MDA-5 has been shown to induce cancer cell death, but the mechanism of action by which MDA-5 exerts these cytotoxic effects is unclear. Here, we demonstrate that ectopic expression of MDA-5 via replication-incompetent adenovirus (Ad.Mda-5) initiates multiple signaling cascades, culminating in cytotoxicity and type I IFN production in mouse and human prostate cancer cells. This intrinsic dual activity of MDA-5 required the adaptor protein IFNβ promoter stimulator 1 (IPS-1, MAVS) and could be functionally uncoupled. MDA-5 lacking N-terminal caspase recruitment domains (CARD) engaged an intracellular death program in cancer cells but was unable to efficiently stimulate the expression of IFNβ. In contrast to cancer cells susceptible to MDA-5-mediated cytotoxicity, normal cells were highly resistant and instead developed a robust type I IFN response. Strikingly, intratumoral delivery of Ad.Mda-5 led to regression of preestablished prostate cancers and development of long-lasting antitumor immune memory, which was primarily attributed to the activation of tumor-reactive cytotoxic T lymphocytes and/or natural killer cells. Using the CARD-truncated MDA-5 mutant, silencing of IPS-1, and antibody blockade of the IFNα/β receptor, we further demonstrate that type I IFN signaling was crucial for in situ MDA-5-induced protective antitumor immunity. Therefore, deliberately targeting the evolutionarily conserved MDA-5-IPS-1 antiviral pathway in tumors can provoke parallel tumoricidal and immunostimulatory effects that bridge innate and adaptive immune responses for the therapeutic treatment of cancer. Cancer Res; 76(8); 2166-76. ©2016 AACR.

Satb1 Overexpression Drives Tumor-Promoting Activities in Cancer-Associated Dendritic Cells

Special AT-rich sequence-binding protein 1 (Satb1) governs genome-wide transcriptional programs. Using a conditional knockout mouse, we find that Satb1 is required for normal differentiation of conventional dendritic cells (DCs). Furthermore, Satb1 governs the differentiation of inflammatory DCs by regulating major histocompatibility complex class II (MHC II) expression through Notch1 signaling. Mechanistically, Satb1 binds to the Notch1 promoter, activating Notch expression and driving RBPJ occupancy of the H2-Ab1 promoter, which activates MHC II transcription. However, tumor-driven, unremitting expression of Satb1 in activated Zbtb46(+) inflammatory DCs that infiltrate ovarian tumors results in an immunosuppressive phenotype characterized by increased secretion of tumor-promoting Galectin-1 and IL-6. In vivo silencing of Satb1 in tumor-associated DCs reverses their tumorigenic activity and boosts protective immunity. Therefore, dynamic fluctuations in Satb1 expression govern the generation and immunostimulatory activity of steady-state and inflammatory DCs, but continuous Satb1 overexpression in differentiated DCs converts them into tolerogenic/pro-inflammatory cells that contribute to malignant progression.

Targeting of cancer‑associated fibroblasts enhances the efficacy of cancer chemotherapy by regulating the tumor microenvironment

Cancer-associated fibroblasts (CAFs), key components of the tumor stroma, can regulate tumorigenesis by altering the tumor microenvironment in variety of ways to promote angiogenesis, recruit inflammatory immune cells and remodel the extracellular matrix. Using a murine xenograft model of colon carcinoma, the present study observed that oxaliplatin increased the accumulation of CAFs and stimulated the production of cytokines associated with CAFs. When oxaliplatin was combined with the small-molecule dipeptidyl peptidase inhibitor PT-100, which inhibits CAFs by targeting fibroblast activation protein (FAP), the accumulation of CAFs was markedly reduced, xenograft tumor growth was significantly suppressed and the survival of the mice increased, compared to those of mice treated with oxaliplatin or PT-100 alone. Furthermore, the xenograft tumor tissues of mice treated with oxaliplatin and PT-100 contained lower numbers of tumor-associated macrophages and dendritic cells, expressed lower levels of cytokines associated with CAFs and had a lower density of CD31+ endothelial cells. The present study demonstrated that pharmacological inhibition of CAFs improved the response to chemotherapy, reduced the recruitment of immune tumor-promoting cells and inhibited angiogenesis. Combining chemotherapy with agents which target CAFs may represent a novel strategy for improving the efficacy of chemotherapy and reducing chemoresistance.

Targeting abnormal ER stress responses in tumors: A new approach to cancer immunotherapy

Cancers thrive under adverse conditions and simultaneously inhibit antitumor immunity. We recently found that endoplasmic reticulum (ER) stress responses driven by the IRE1α-XBP1 pathway not only promote cancer cell survival, but also provoke severe dendritic cell (DC) dysfunction in tumors. Targeting IRE1α-XBP1 represents a two-pronged approach to restrain malignant cells while eliciting concomitant antitumor immunity.

Dendritic cells are stressed out in tumor

A recently paper published in Cell reports that dendritic cells (DCs) are dysfunctional in the tumor environment. Tumor impairs DC function through induction of endoplasmic reticulum stress response and subsequent disruption of lipid metabolic homeostasis.

Combined Trabectedin and anti-PD1 antibody produces a synergistic antitumor effect in a murine model of ovarian cancer

BACKGROUND

Monoclonal antibodies (mAb) that block programmed death (PD)-1 signaling pathway hold great potential as a novel cancer immunotherapy. Recent evidence suggests that combining with conventional, targeted or other immunotherapies, these mAb can induce synergistic antitumor responses. In this study, we investigated whether Trabectedin (ET-743), a novel anticancer agent currently used for treating relapsed ovarian cancer, can synergize with anti (α)-PD-1 mAb to increase antitumor activity in the murine ID8 ovarian cancer model.

METHODS

Mice with established peritoneal ID8 tumor were treated with either single or combined Trabectedin and α-PD-1 mAb, their overall survival was recorded; tumor-associated immune cells and immune gene expression in tumors from treated mice were analyzed by flow cytometry and quantitative RT-PCR, respectively, and antigen-specific immunity of effector CD8(+) T cells was evaluated by ELISA and cytotoxicity assay. In addition, the effect of Trabectedin on tumoral PD-L1 expression was analyzed by both flow cytometry and immunofluorescence staining.

RESULTS

Though single treatment showed a modest antitumor effect in mice bearing 10-day-established ID8 tumor, combined Trabectedin and α-PD-1 mAb treatment induced a strong antitumor immune response, leading to a significant tumor regression with half of mice tumor-free 90 days after tumor inoculation. Mechanistic investigation revealed that combination treatment induces a systemic tumor-specific immunity with an indispensable role of both CD4(+) and CD8(+) T cells, and effector CD8(+) T cells exhibited the antigen-specific cytokine secretion and cytotoxicity upon tumor antigen stimulation; additionally, combination treatment increased the IFN-γ-producing effector T cells and decreased the immunosuppressive cells in peritoneal cavity; accordingly, it enhanced the expression of Th1-associated immune-stimulating genes while reducing the transcription of regulatory/suppressive immune genes, reshaping tumor microenvironment from a immunosuppressive to a stimulatory state. Finally, in vivo Trabectedin treatment has been shown to induce IFN-γ-dependent PD-L1 expression within tumor, possibly constituting a mechanistic basis for its synergistic antitumor effect with α-PD-1 mAb therapy.

CONCLUSION

This study provides the evidence that α-PD-1 mAb can produce a synergistic antitumor efficacy when combined with Trabectedin, a clinically available anticancer agent, supporting a direct translation of this combination strategy in clinic for the treatment of ovarian cancer.

ER Stress Sensor XBP1 Controls Anti-tumor Immunity by Disrupting Dendritic Cell Homeostasis

Dendritic cells (DCs) are required to initiate and sustain T cell-dependent anti-cancer immunity. However, tumors often evade immune control by crippling normal DC function. The endoplasmic reticulum (ER) stress response factor XBP1 promotes intrinsic tumor growth directly, but whether it also regulates the host anti-tumor immune response is not known. Here we show that constitutive activation of XBP1 in tumor-associated DCs (tDCs) drives ovarian cancer (OvCa) progression by blunting anti-tumor immunity. XBP1 activation, fueled by lipid peroxidation byproducts, induced a triglyceride biosynthetic program in tDCs leading to abnormal lipid accumulation and subsequent inhibition of tDC capacity to support anti-tumor T cells. Accordingly, DC-specific XBP1 deletion or selective nanoparticle-mediated XBP1 silencing in tDCs restored their immunostimulatory activity in situ and extended survival by evoking protective type 1 anti-tumor responses. Targeting the ER stress response should concomitantly inhibit tumor growth and enhance anti-cancer immunity, thus offering a unique approach to cancer immunotherapy.

Toxicity profiling of several common RNAi-based nanomedicines: a comparative study

RNAi-based nanomedicine platforms (RNPs) have progressed from tools to study gene expression in vitro into clinical trials. Numerous RNPs strategies have been documented with an efficient ability to condense RNAi payloads and induce potent gene silencing. Moreover, some of these RNPs have been explored in various animal models, and some have even made it to the clinic. Still, there is lack of a clinically approved RNAi-based delivery strategy most probably due to unpredicted clinical toxicity. In this study, we prepared common RNPs such as cationic liposomes, polyamines, and hyaluronan-coated lipid-based nanoparticles and tested these strategies for global toxicity parameters such as changes in bodyweight, liver enzyme release, and hematological profiling. We found that polyamines such as polyethyleneimine and Poly-L-lysine released high levels of liver enzymes into the serum and reduced C57BL/6 mice bodyweight upon three intravenous injections. In addition, these polyamines dramatically reduced the total number of leukocytes, suggesting an immune suppression mechanism, while cationic liposomes, which also increased liver enzymes levels in the serum, elevated the total number of leukocytes probably by activation of Toll-like receptors 2 and 4. Coating the liposomes with hyaluronan, a hydrophilic glycosaminoglycan, provided a protective layer and did not induce adverse effects upon multiple intravenous injections. These findings suggest that there is an urgent need to develop gold standards for nanotoxicity in the field of RNAi that will be embraced by the RNAi community.

Biodegradable nanoparticles sequentially decorated with Polyethyleneimine and Hyaluronan for the targeted delivery of docetaxel to airway cancer cells

Background

Novel polymeric nanoparticles (NPs) specifically designed for delivering chemotherapeutics in the body and aimed at improving treatment activity and selectivity, cover a very relevant area in the field of nanomedicine.

Here, we describe how to build a polymer shell of Hyaluronan (HA) and Polyethyleneimine (PEI) on biodegradable NPs of poly(lactic-co-glycolic) acid (PLGA) through electrostatic interactions and to achieve NPs with unique features of sustained delivery of a docetaxel (DTX) drug cargo as well as improved intracellular uptake.

Results

A stable PEI or HA/PEI shell could be obtained by careful selection of layering conditions. NPs with exquisite stability in salt and protein-rich media, with size and surface charge matching biological requirements for intravenous injection and endowed with sustained DTX release could be obtained. Cytotoxicity, uptake and activity of both PLGA/PEI/HA and PLGA/PEI NPs were evaluated in CD44(+) (A549) and CD44(−) (Calu-3) lung cancer cells. In fact, PEI-coated NPs can be formed after degradation/dissociation of the surface HA because of the excess hyaluronidases overexpressed in tumour interstitium. There was no statistically significant cytotoxic effect of PLGA/PEI/HA and PLGA/PEI NPs in both cell lines, thus suggesting that introduction of PEI in NP shell was not hampered by its intrinsic toxicity. Intracellular trafficking of NPs fluorescently labeled with Rhodamine (RHO) (RHO-PLGA/PEI/HA and RHO-PLGA/PEI NPs) demonstrated an increased time-dependent uptake only for RHO-PLGA/PEI/HA NPs in A549 cells as compared to Calu-3 cells. As expected, RHO-PLGA/PEI NP uptake in A549 cells was comparable to that observed in Calu-3 cells. RHO-PLGA/PEI/HA NPs internalized into A549 cells showed a preferential perinuclear localization. Cytotoxicity data in A549 cells suggested that DTX delivered through PLGA/PEI/HA NPs exerted a more potent antiproliferative activity than free DTX. Furthermore, DTX-PLGA/PEI NPs, as hypothetical result of hyaluronidase-mediated degradation in tumor interstitium, were still able to improve the cytotoxic activity of free DTX.

Conclusions

Taken together, results lead us to hypothesize that biodegradable NPs coated with a PEI/HA shell represent a very promising system to treat CD44 overexpressing lung cancer. In principle, this novel nanocarrier can be extended to different single drugs and drug combinations taking advantage of the shell and core properties.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-015-0088-2) contains supplementary material, which is available to authorized users.

Microbially driven TLR5-dependent signaling governs distal malignant progression through tumor-promoting inflammation

The dominant TLR5(R392X) polymorphism abrogates flagellin responses in >7% of humans. We report that TLR5-dependent commensal bacteria drive malignant progression at extramucosal locations by increasing systemic IL-6, which drives mobilization of myeloid-derived suppressor cells (MDSCs). Mechanistically, expanded granulocytic MDSCs cause γδ lymphocytes in TLR5-responsive tumors to secrete galectin-1, dampening antitumor immunity and accelerating malignant progression. In contrast, IL-17 is consistently upregulated in TLR5-unresponsive tumor-bearing mice but only accelerates malignant progression in IL-6-unresponsive tumors. Importantly, depletion of commensal bacteria abrogates TLR5-dependent differences in tumor growth. Contrasting differences in inflammatory cytokines and malignant evolution are recapitulated in TLR5-responsive/unresponsive ovarian and breast cancer patients. Therefore, inflammation, antitumor immunity, and the clinical outcome of cancer patients are influenced by a common TLR5 polymorphism.

Safety of Nanoparticles in Medicine

Nanomedicine involves the use of nanoparticles for therapeutic and diagnostic purposes. During the past two decades, a growing number of nanomedicines have received regulatory approval and many more show promise for future clinical translation. In this context, it is important to evaluate the safety of nanoparticles in order to achieve biocompatibility and desired activity. However, it is unwarranted to make generalized statements regarding the safety of nanoparticles, since the field of nanomedicine comprises a multitude of different manufactured nanoparticles made from various materials. Indeed, several nanotherapeutics that are currently approved, such as Doxil and Abraxane, exhibit fewer side effects than their small molecule counterparts, while other nanoparticles (e.g. metallic and carbon-based particles) tend to display toxicity. However, the hazardous nature of certain nanomedicines could be exploited for the ablation of diseased tissue, if selective targeting can be achieved. This review discusses the mechanisms for molecular, cellular, organ, and immune system toxicity, which can be observed with a subset of nanoparticles. Strategies for improving the safety of nanoparticles by surface modification and pretreatment with immunomodulators are also discussed. Additionally, important considerations for nanoparticle safety assessment are reviewed. In regards to clinical application, stricter regulations for the approval of nanomedicines might not be required. Rather, safety evaluation assays should be adjusted to be more appropriate for engineered nanoparticles.

Transforming growth factor β-mediated suppression of antitumor T cells requires FoxP1 transcription factor expression

Tumor-reactive T cells become unresponsive in advanced tumors. Here we have characterized a common mechanism of T cell unresponsiveness in cancer driven by the upregulation of the transcription factor Forkhead box protein P1 (Foxp1), which prevents CD8⁺ T cells from proliferating and upregulating Granzyme-B and interferon-γ in response to tumor antigens. Accordingly, Foxp1-deficient lymphocytes induced rejection of incurable tumors and promoted protection against tumor rechallenge. Mechanistically, Foxp1 interacted with the transcription factors Smad2 and Smad3 in preactivated CD8⁺ T cells in response to microenvironmental transforming growth factor-β (TGF-β), and was essential for its suppressive activity. Therefore, Smad2 and Smad3-mediated c-Myc repression requires Foxp1 expression in T cells. Furthermore, Foxp1 directly mediated TGF-β-induced c-Jun transcriptional repression, which abrogated T cell activity. Our results unveil a fundamental mechanism of T cell unresponsiveness different from anergy or exhaustion, driven by TGF-β signaling on tumor-associated lymphocytes undergoing Foxp1-dependent transcriptional regulation.

Development of nanoscale approaches for ovarian cancer therapeutics and diagnostics

Ovarian cancer is the deadliest of all gynecological cancers and the fifth leading cause of death due to cancer in women. This is largely due to late-stage diagnosis, poor prognosis related to advanced-stage disease, and the high recurrence rate associated with development of chemoresistance. Survival statistics have not improved significantly over the last three decades, highlighting the fact that improved therapeutic strategies and early detection require substantial improvements. Here, we review and highlight nanotechnology-based approaches that seek to address this need. The success of Doxil, a PEGylated liposomal nanoencapsulation of doxorubicin, which was approved by the FDA for use on recurrent ovarian cancer, has paved the way for the current wave of nanoparticle formulations in drug discovery and clinical trials. We discuss and summarize new nanoformulations that are currently moving into clinical trials and highlight novel nanotherapeutic strategies that have shown promising results in preclinical in vivo studies. Further, the potential for nanomaterials in diagnostic imaging techniques and the ability to leverage nanotechnology for early detection of ovarian cancer are also discussed.

Good things come in small packages: Therapeutic anti-tumor immunity induced by microRNA nanoparticles

Current ovarian cancer treatments based on surgery/chemotherapy show limited efficacy. Targeting immunosuppression is a requirement for the effectiveness of novel promising anti-tumor immunotherapies. Our latest work in preclinical models shows that nanoparticle-mediated delivery of immunostimulatory microRNAs specifically to tumor-associated leukocytes is sufficient to re-program immunological control of metastatic ovarian cancers.

Contribution of TLR signaling to the pathogenesis of colitis-associated cancer in inflammatory bowel disease

In the intestine a balance between proinflammatory and repair signals of the immune system is essential for the maintenance of intestinal homeostasis. The innate immunity ensures a primary host response to microbial invasion, which induces an inflammatory process to localize the infection and prevent systemic dissemination of pathogens. The key elements of this process are the germline encoded pattern recognition receptors including Toll-like receptors (TLRs). If pathogens cannot be eliminated, they may elicit chronic inflammation, which may be partly mediated via TLRs. Additionally, chronic inflammation has long been suggested to trigger tissue tumorous transformation. Inflammation, the seventh hallmark of cancer, may affect all phases of tumor development, and evade the immune system. Inflammation acts as a cellular stressor and may trigger DNA damage or genetic instability. Furthermore, chronic inflammation can provoke genetic mutations and epigenetic mechanisms that promote malignant cell transformation. Colorectal cancers in inflammatory bowel disease patients are considered typical examples of inflammation-related cancers. Although data regarding the role of TLRs in the pathomechanism of cancer-associated colitis are rather conflicting, functionally these molecules can be classified as ”largely antitumorigenic” and ”largely pro-tumorigenic” with the caveat that the underlying signaling pathways are mainly context (i.e., organ-, tissue-, cell-) and ligand-dependent.

Transforming growth factor β-mediated suppression of antitumor T cells requires FoxP1 transcription factor expression

Tumor-reactive T cells become unresponsive in advanced tumors. Here we have characterized a common mechanism of T cell unresponsiveness in cancer driven by the upregulation of the transcription factor Forkhead box protein P1 (Foxp1), which prevents CD8⁺ T cells from proliferating and upregulating Granzyme-B and interferon-γ in response to tumor antigens. Accordingly, Foxp1-deficient lymphocytes induced rejection of incurable tumors and promoted protection against tumor rechallenge. Mechanistically, Foxp1 interacted with the transcription factors Smad2 and Smad3 in preactivated CD8⁺ T cells in response to microenvironmental transforming growth factor-β (TGF-β), and was essential for its suppressive activity. Therefore, Smad2 and Smad3-mediated c-Myc repression requires Foxp1 expression in T cells. Furthermore, Foxp1 directly mediated TGF-β-induced c-Jun transcriptional repression, which abrogated T cell activity. Our results unveil a fundamental mechanism of T cell unresponsiveness different from anergy or exhaustion, driven by TGF-β signaling on tumor-associated lymphocytes undergoing Foxp1-dependent transcriptional regulation.

The role of microRNAs in ovarian cancer

Ovarian cancer is the most lethal of malignant gynecological tumors. Its lethality may be due to difficulties in detecting it at an early stage and lack of effective treatments for patients with an advanced or recurrent status. Therefore, there is a strong need for prognostic and predictive markers to diagnose it early and to help optimize and personalize treatment. MicroRNAs are noncoding RNAs that regulate target genes posttranscriptionally. They are involved in carcinogenesis, cell cycle, apoptosis, proliferation, invasion, metastasis, and chemoresistance. The dysregulation of microRNAs is involved in the initiation and progression of human cancers including ovarian cancer, and strong evidence that microRNAs can act as oncogenes or tumor suppressor genes has emerged. Several microRNA signatures that are unique to ovarian cancer have been proposed, and serum-circulating microRNAs have the potential to be useful diagnostic and prognostic biomarkers. Various microRNAs such as those in the miR-200 family, the miR-199/214 cluster, or the let-7 paralogs have potential as therapeutic targets for disseminated or chemoresistant ovarian tumors. Although many obstacles need to be overcome, microRNA therapy could be a powerful tool for ovarian cancer prevention and treatment. In this review, we discuss the emerging roles of microRNAs in various aspects of ovarian cancer.

Selective uptake of single-walled carbon nanotubes by circulating monocytes for enhanced tumour delivery

In cancer imaging, nanoparticle biodistribution is typically visualized in living subjects using 'bulk' imaging modalities such as magnetic resonance imaging, computerized tomography and whole-body fluorescence. Accordingly, nanoparticle influx is observed only macroscopically, and the mechanisms by which they target cancer remain elusive. Nanoparticles are assumed to accumulate via several targeting mechanisms, particularly extravasation (leakage into tumour). Here, we show that, in addition to conventional nanoparticle-uptake mechanisms, single-walled carbon nanotubes are almost exclusively taken up by a single immune cell subset, Ly-6C(hi) monocytes (almost 100% uptake in Ly-6C(hi) monocytes, below 3% in all other circulating cells), and delivered to the tumour in mice. We also demonstrate that a targeting ligand (RGD) conjugated to nanotubes significantly enhances the number of single-walled carbon nanotube-loaded monocytes reaching the tumour (P < 0.001, day 7 post-injection). The remarkable selectivity of this tumour-targeting mechanism demonstrates an advanced immune-based delivery strategy for enhancing specific tumour delivery with substantial penetration.

Stimulating antitumor immunity with nanoparticles

A variety of strategies, have been applied to cancer treatment and the most recent one to become prominent is immunotherapy. This interest has been fostered by the demonstration that the immune system does recognize and often eliminate small tumors but tumors that become clinical problems block antitumor immune responses with immunosuppression orchestrated by the tumor cells. Methods to reverse this tumor-mediated immunosuppression will improve cancer immunotherapy outcomes. The immunostimulatory potential of nanoparticles (NPs), holds promise for cancer treatment. Phagocytes of various types are an important component of both immunosuppression and immunostimulation and phagocytes actively take up NPs of various sorts, so NPs are a natural system to manipulate these key immune regulatory cells. NPs can be engineered with multiple useful therapeutic features, such as various payloads such as antigens and/or immunomodulatory agents including cytokines, ligands for immunostimulatory receptors or antagonists for immunosuppressive receptors. As more is learned about how tumors suppress antitumor immune responses the payload options expand further. Here we review multiple approaches of NP-based cancer therapies to modify the tumor microenvironment and stimulate innate and adaptive immune systems to obtain effective antitumor immune responses.

Perspectives on reprograming cancer-associated dendritic cells for anti-tumor therapies

In recent years, the relevance of the tumor microenvironment (TME) in the progression of cancer has gained considerable attention. It has been shown that the TME is capable of inactivating various components of the immune system responsible for tumor clearance, thus favoring cancer cell growth and tumor metastasis. In particular, effects of the TME on antigen-presenting cells, such as dendritic cells (DCs) include rendering these cells unable to promote specific immune responses or transform them into suppressive cells capable of inducing regulatory T cells. In addition, under the influence of the TME, DCs can produce growth factors that induce neovascularization, therefore further contributing to tumor development. Interestingly, cancer-associated DCs harbor tumor antigens and thus have the potential to become anti-tumor vaccines in situ if properly reactivated. This perspective article provides an overview of the scientific background and experimental basis for reprograming cancer-associated DCs in situ to generate anti-tumor immune responses.

PD-1 blockade and OX40 triggering synergistically protects against tumor growth in a murine model of ovarian cancer

The co-inhibitory receptor Programmed Death-1 (PD-1) curtails immune responses and prevent autoimmunity, however, tumors exploit this pathway to escape from immune destruction. The co-stimulatory receptor OX40 is upregulated on T cells following activation and increases their clonal expansion, survival and cytokine production when engaged. Although antagonistic anti-PD-1 or agonistic anti-OX40 antibodies can promote the rejection of several murine tumors, some poorly immunogenic tumors were refractory to this treatment. In the present study, we evaluated the antitumor effects and mechanisms of combinatorial PD-1 blockade and OX40 triggering in a murine ID8 ovarian cancer model. Although individual anti-PD-1 or OX40 mAb treatment was ineffective in tumor protection against 10-day established ID8 tumor, combined anti-PD-1/OX40 mAb treatment markedly inhibited tumor outgrowth with 60% of mice tumor free 90 days after tumor inoculation. Tumor protection was associated with a systemic immune response with memory and antigen specificity and required CD4(+) cells and CD8(+) T cells. The anti-PD-1/OX40 mAb treatment increased CD4(+) and CD8(+) cells and decreased immunosuppressive CD4(+)FoxP3(+) regulatory T (Treg) cells and CD11b(+)Gr-1(+) myeloid suppressor cells (MDSC), giving rise to significantly higher ratios of both effector CD4(+) and CD8(+) cells to Treg and MDSC in peritoneal cavity; Quantitative RT-PCR data further demonstrated the induction of a local immunostimulatory milieu by anti-PD-1/OX40 mAb treatment. The splenic CD8(+) T cells from combined mAb treated mice produced high levels of IFN-γ upon tumor antigen stimulation and exhibited antigen-specific cytolytic activity. To our knowledge, this is the first study testing the antitumor effects of combined anti-PD-1/OX40 mAb in a murine ovarian cancer model, and our results provide a rationale for clinical trials evaluating ovarian cancer immunotherapy using this combination of mAb.

Combined PD-1 blockade and GITR triggering induce a potent antitumor immunity in murine cancer models and synergizes with chemotherapeutic drugs

BACKGROUND

The coinhibitory receptor Programmed Death-1 (PD-1) inhibits effector functions of activated T cells and prevents autoimmunity, however, cancer hijack this pathway to escape from immune attack. The costimulatory receptor glucocorticoid-induced TNFR related protein (GITR) is up-regulated on activated T cells and increases their proliferation, activation and cytokine production. We hypothesize that concomitant PD-1 blockade and GITR triggering would synergistically improve the effector functions of tumor-infiltrating T cells and increase the antitumor immunity. In present study, we evaluated the antitumor effects and mechanisms of combined PD-1 blockade and GITR triggering in a clinically highly relevant murine ID8 ovarian cancer model.

METHODS

Mice with 7 days-established peritoneal ID8 ovarian cancer were treated intraperitoneally (i.p.) with either control, anti-PD-1, anti-GITR or anti-PD-1/GITR monoclonal antibody (mAb) and their survival was evaluated; the phenotype and function of tumor-associated immune cells in peritoneal cavity of treated mice was analyzed by flow cytometry, and systemic antigen-specific immune response was evaluated by ELISA and cytotoxicity assay.

RESULTS

Combined anti-PD-1/GITR mAb treatment remarkably inhibited peritoneal ID8 tumor growth with 20% of mice tumor free 90 days after tumor challenge while treatment with either anti-PD-1 or anti-GITR mAb alone exhibited little antitumor effect. The durable antitumor effect was associated with a memory immune response and conferred by CD4⁺ cells and CD8⁺ T cells. The treatment of anti-PD-1/GITR mAb increased the frequencies of interferon-γ-producing effector T cells and decreased immunosuppressive regulatory T cells and myeloid-derived suppressor cells, shifting an immunosuppressive tumor milieu to an immunostimulatory state in peritoneal cavity. In addition, combined treatment of anti-PD-1/GITR mAb mounted an antigen-specific immune response as evidenced by antigen-specific IFN-γ production and cytolytic activity of spleen cells from treated mice. More importantly, combined treatment of anti-PD-1/GITR mAb and chemotherapeutic drugs (cisplatin or paclitaxel) further increased the antitumor efficacy with 80% of mice obtaining tumor-free long-term survival in murine ID8 ovarian cancer and 4 T1 breast cancer models.

CONCLUSIONS

Combined anti-PD-1/GITR mAb treatment induces a potent antitumor immunity, which can be further promoted by chemotherapeutic drugs. A combined strategy of anti-PD-1/GITR mAb plus cisplatin or paclitaxel should be considered translation into clinic.

Modulating the tumor immune microenvironment as an ovarian cancer treatment strategy

After more than 30 years of iterations of surgical debulking plus chemotherapy, the need for complementary ovarian cancer treatments has become clear. In the ovarian cancer microenvironment, myeloid immunosuppressive leukocytes, lymphocytes, fibroblasts and endothelial cells, as well as their secreted products, surface molecules and paracrine survival factors, all provide opportunities for novel interventions. The potential of targeting microenvironmental elements in ovarian cancer patients is underscored by recently successful anti-angiogenic therapies. The compartmentalized nature of ovarian cancer, its immunogenicity and its accessibility make it an ideal disease for targeting non-tumor host cells. This review discusses the 'state-of-the-art' of the field, with an emphasis on the potential of modulating the activity of abundant microenvironmental immune cells, which govern both angiogenesis and immunosuppression.

Reprogramming immune responses via microRNA modulation

It is becoming increasingly clear that there are unique sets of miRNAs that have distinct governing roles in several aspects of both innate and adaptive immune responses. In addition, new tools allow selective modulation of the expression of individual miRNAs, both in vitro and in vivo. Here, we summarize recent advances in our understanding of how miRNAs drive the activity of immune cells, and how their modulation in vivo opens new avenues for diagnostic and therapeutic interventions in multiple diseases, from immunodeficiency to cancer.

Combinatorial PD-1 blockade and CD137 activation has therapeutic efficacy in murine cancer models and synergizes with cisplatin

There is an urgent need for improved therapy for advanced ovarian carcinoma, which may be met by administering immune-modulatory monoclonal antibodies (mAbs) to generate a tumor-destructive immune response. Using the ID8 mouse ovarian cancer model, we investigated the therapeutic efficacy of various mAb combinations in mice with intraperitoneal (i.p.) tumor established by transplanting 3 × 10⁶ ID8 cells 10 days previously. While most of the tested mAbs were ineffective when given individually or together, the data confirm our previous finding that 2 i.p. injections of a combination of anti-CD137 with anti-PD-1 mAbs doubles overall survival. Mice treated with this mAb combination have a significantly increased frequency and total number of CD8⁺ T cells both in the peritoneal lavage and spleens, and these cells are functional as demonstrated by antigen-specific cytolytic activity and IFN-γ production. While administration of anti-CD137 mAb as a single agent similarly increases CD8⁺ T cells, these have no functional activity, which may be attributed to up-regulation of co-inhibitory PD-1 and TIM-3 molecules induced by CD137. Addition of the anti-cancer drug cisplatin to the 2 mAb combination increased overall survival >90 days (and was probably curative) by a mechanism which included a systemic CD8⁺ T cell response with tumor specificity and immunological memory. Strikingly, combined treatment of cisplatin and CD137/PD-1 mAb also gave rise to the long-term survival of mice with established TC1 lung tumors. A similar combination of the 2 mAbs and cisplatin should be considered for clinical ‘translation’.

Pathological mobilization and activities of dendritic cells in tumor-bearing hosts: challenges and opportunities for immunotherapy of cancer

A common characteristic of solid tumors is the pathological recruitment of immunosuppressive myeloid cells, which in certain tumors includes dendritic cells (DCs). DCs are of particular interest in the field of cancer immunotherapy because they induce potent and highly specific anti-tumor immune responses, particularly in the early phase of tumorigenesis. However, as tumors progress, these cells can be transformed into regulatory cells that contribute to an immunosuppressive microenvironment favoring tumor growth. Therefore, controlling DC phenotype has the potential to elicit effective anti-tumor responses while simultaneously weakening the tumor’s ability to protect itself from immune attack. This review focuses on the dual nature of DCs in the tumor microenvironment, the regulation of DC phenotype, and the prospect of modifying DCs in situ as a novel immunotherapeutic approach.

A role for the chemokine receptor CCR6 in mammalian sperm motility and chemotaxis

Although recent evidence indicates that several chemokines and defensins, well-known as inflammatory mediators, are expressed in the male and female reproductive tracts, the location and functional significance of chemokine networks in sperm physiology and sperm reproductive tract interactions are poorly understood. To address this deficiency in our knowledge, we examined the expression and function in sperm of CCR6, a receptor common to several chemoattractant peptides, and screened several reproductive tract fluids for the presence of specific ligands. CCR6 protein is present in mouse and human sperm and mainly localized in the sperm tail with other minor patterns in sperm from mice (neck and acrosomal region) and men (neck and midpiece regions). As expected from the protein immunoblotting and immunofluorescence results, mouse Ccr6 mRNA is expressed in the testis. Furthermore, the Defb29 mRNA encoding the CCR6 ligand, β-defensin DEFB29, is expressed at high levels in the epididymis. As determined by protein chip analysis, several chemokines (including some that act through CCR6, such as CCL20/MIP-3α (formerly macrophage inflammatory protein 3α) and protein hormones were present in human follicular fluid, endometrial secretions, and seminal plasma. In functional chemotaxis assays, capacitated human sperm exhibited a directional movement towards CCL20, and displayed modifications in motility parameters. Our data indicate that chemokine ligand/receptor interactions in the male and female genital tracts promote sperm motility and chemotaxis under non-inflammatory conditions. Therefore, some of the physiological reactions mediated by CCR6 ligands in male reproduction extend beyond a pro-inflammatory response and might find application in clinical reproduction and/or contraception.

Human TLR8 is activated upon recognition of Borrelia burgdorferi RNA in the phagosome of human monocytes

Phagocytosed Borrelia burgdorferi (Bb), the Lyme disease spirochete, induces a robust and complex innate immune response in human monocytes, in which TLR8 cooperates with TLR2 in the induction of NF-κB-mediated cytokine production, whereas TLR8 is solely responsible for transcription of IFN-β through IRF7. We now establish the role of Bb RNA in TLR8-mediated induction of IFN-β. First, using TLR2-transfected HEK.293 cells, which were unable to phagocytose intact Bb, we observed TLR2 activation by lipoprotein-rich borrelial lysates and TLR2 synthetic ligands but not in response to live spirochetes. Purified Bb RNA, but not borrelial DNA, triggered TLR8 activation. Neither of these 2 ligands induced activation of TLR7. Using purified human monocytes we then show that phagocytosed live Bb, as well as equivalent amounts of borrelial RNA delivered into the phagosome by polyethylenimine (PEI), induces transcription of IFN-β and secretion of TNF-α. The cytokine response to purified Bb RNA was markedly impaired in human monocytes naturally deficient in IRAK-4 and in cells with knockdown TLR8 expression by small interfering RNA. Using confocal microscopy we provide evidence that TLR8 colocalizes with internalized Bb RNA in both early (EEA1) and late endosomes (LAMP1). Live bacterial RNA staining indicates that spirochetal RNA does not transfer from the phagosome into the cytosol. Using fluorescent dextran particles we show that phagosomal integrity in Bb-infected monocytes is not affected. We demonstrate, for the first time, that Bb RNA is a TLR8 ligand in human monocytes and that transcription of IFN-β in response to the spirochete is induced from within the phagosomal vacuole through the TLR8-MyD88 pathway.

Surface charges and shell crosslinks each play significant roles in mediating degradation, biofouling, cytotoxicity and immunotoxicity for polyphosphoester-based nanoparticles

The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications.

Combined TIM-3 blockade and CD137 activation affords the long-term protection in a murine model of ovarian cancer

Background

T-cell immunoglobulin and mucin domain 3 (TIM-3) is known as a negative immune regulator and emerging data have implicated TIM-3 a pivotal role in suppressing antitumor immunity. The co-stimulatory receptor CD137 is transiently upregulated on T-cells following activation and increases their proliferation and survival when engaged. Although antagonistic anti-TIM-3 or agonistic anti-CD137 antibodies can promote the rejection of several murine tumors, some poorly immunogenic tumors were refractory to this treatment. In this study, we sought to evaluate whether combined TIM-3 blockade and CD137 activation would significantly improve the immunotherapy in the murine ID8 ovarian cancer model.

Methods

Mice with established ID8 tumor were intraperitoneally injected with single or combined anti-TIM-3/CD137 monoclonal antibody (mAb); mice survival was recorded, the composition and gene expression of tumor-infiltrating immune cells in these mice was analyzed by flow cytometry and quantitative RT-PCR respectively, and the function of CD8⁺ cells was evaluated by ELISA and cytotoxicity assay.

Results

Either anti-TIM-3 or CD137 mAb alone, although effective in 3 days established tumor, was unable to prevent tumor progression in mice bearing 10 days established tumor, however, combined anti-TIM-3/CD137 mAb significantly inhibited the growth of these tumors with 60% of mice tumor free 90 days after tumor inoculation. Therapeutic efficacy was associated with a systemic immune response with memory and antigen specificity, required CD4⁺ cells and CD8⁺ cells. The 2 mAb combination increased CD4⁺ and CD8⁺ cells and decreased immunosuppressive CD4⁺FoxP3⁺ regulatory T (Treg) cells and CD11b⁺Gr-1⁺ myeloid suppressor cells (MDSC) at tumor sites, giving rise to significantly elevated ratios of CD4⁺ and CD8⁺ cells to Treg and MDSC; This is consistent with biasing local immune response towards an immunostimulatory Th1 type and is further supported by quantitative RT-PCR data showing the increased Th1-associated genes by anti-TIM-3/CD137 treatment. The increased CD8⁺ T cells produced high level of IFN-γ upon tumor antigen stimulation and displayed antigen-specific cytotoxic activity.

Conclusions

To our knowledge, this is the first report investigating the effects of anti-TIM-3/CD137 combined mAb in a murine ovarian cancer model, and our results may aid the design of future trials for ovarian cancer immunotherapy.

The Yin and Yang of Toll-like receptors in cancer

Recognition of non-self molecular patterns by pattern recognition receptors is a cornerstone of innate immunity. Toll-like receptors (TLRs) exert a key role in recognizing pathogen-associated molecular patterns (PAMPs) but have also been implicated in the recognition of damage-associated molecular patterns (DAMPs). As such, TLRs regulate a wide range of biological responses including inflammatory and immune responses during carcinogenesis. The high expression of TLRs by antigen-presenting cells, including dendritic cells, and their ability to induce antitumor mediators such as type I interferon has led to efforts to utilize TLR agonists in tumor therapy in order to convert the often tolerant immune response toward antitumor responses. However, TLRs are also increasingly recognized as regulators of tumor-promoting inflammation and promoters of tumor survival signals. Here, we will review in detail the dichotomous role of TLRs in tumor biology, focusing on relevant TLR-dependent pro- and antitumor pathways, and discuss clinical applications of TLR-targeted therapies for tumor prevention and treatment.

Targeting tumors with nonreplicating Toxoplasma gondii uracil auxotroph vaccines

Toxoplasma gondii is an intracellular parasite that has evolved to actively control its invaded host cells. Toxoplasma triggers then actively regulates host innate interleukin-12 (IL-12) and interferon-γ (IFN-γ) responses that elicit T cell control of infection. A live, nonreplicating avirulent uracil auxotroph vaccine strain (cps) of Toxoplasma triggers novel innate immune responses that stimulate amplified CD8(+) T cell responses and life-long immunity in vaccinated mice. Here, we review recent reports showing that intratumoral treatment with cps activated immune-mediated regression of established solid tumors in mice. We speculate that a better understanding of host-parasite interaction at the molecular level and applying improved genetic models based on Δku80 Toxoplasma strains will stimulate development of highly effective immunotherapeutic cancer vaccine strategies using engineered uracil auxotrophs.

Phagocytes mediate targeting of iron oxide nanoparticles to tumors for cancer therapy

Nanotechnology has great potential to produce novel therapeutic strategies that target malignant cells through the ability of nanoparticles to get access to and be ingested by living cells. However its specificity for accumulation in tumors, which is the key factor that determines its efficacy, has always been a challenge. Here we tested a novel strategy to target and treat ovarian cancer, a representative peritoneal cancer, using iron oxide nanoparticles (IONPs) and an alternating magnetic field (AMF). Peritoneal tumors in general are directly accessible to nanoparticles administered intraperitoneally (IP), as opposed to the more commonly attempted intravenous (IV) administration. In addition, tumor-associated immunosuppressive phagocytes, a predominant cell population in the tumor microenvironment of almost all solid tumors, and cells that are critical for tumor progression, are constantly recruited to the tumor, and therefore could possibly function to bring nanoparticles to tumors. Here we demonstrate that tumor-associated peritoneal phagocytes ingest and carry IONPs specifically to tumors and that these specifically delivered nanoparticles can damage tumor cells after IONP-mediated hyperthermia generated by AMF. This illustrates therapeutic possibilities of intraperitoneal (IP) injection of nanoparticles and subsequent ingestion by tumor-associated phagocytes, to directly impact tumors or stimulate antitumor immune responses. This approach could use IONPs combined with AMF as done here, or other nanoparticles with cytotoxic potential. Overall, the data presented here support IP injection of nanoparticles to utilize peritoneal phagocytes as a delivery vehicle in association with IONP-mediated hyperthermia as therapeutic strategies for ovarian and other peritoneal cancers.

Cytokines as biomarkers of nanoparticle immunotoxicity

Nanoscale objects, whether of biologic origin or synthetically created, are being developed into devices for a variety of bionanotechnology diagnostic and pharmaceutical applications. However, the potential immunotoxicity of these nanomaterials and mechanisms by which they may induce adverse reactions have not received sufficient attention. Nanomaterials, depending on their characteristics and compositions, can interact with the immune system in several ways and either enhance or suppress immune system function. Cytokines perform pleiotropic functions to mediate and regulate the immune response and are generally recognized as biomarkers of immunotoxicity. While the specificity and validity of certain cytokines as markers of adverse immune response has been established for chemicals, small and macromolecular drugs, research on their applicability for predicting and monitoring the immunotoxicity of engineered nanomaterials is still ongoing. The goal of this review is to provide guidelines as to important cytokines that can be utilized for evaluating the immunotoxicity of nanomaterials and to highlight the role of those cytokines in mediating adverse reactions, which is of particular importance for the clinical development of nanopharmaceuticals and other nanotechnology-based products. Importantly, the rational design of nanomaterials of low immunotoxicity will be discussed, focusing on synthetic nanodevices, with emphasis on both the nanoparticle-forming materials and the embedded cargoes.

Cytokines as biomarkers of nanoparticle immunotoxicity

Nanoscale objects, whether of biologic origin or synthetically created, are being developed into devices for a variety of bionanotechnology diagnostic and pharmaceutical applications. However, the potential immunotoxicity of these nanomaterials and mechanisms by which they may induce adverse reactions have not received sufficient attention. Nanomaterials, depending on their characteristics and compositions, can interact with the immune system in several ways and either enhance or suppress immune system function. Cytokines perform pleiotropic functions to mediate and regulate the immune response and are generally recognized as biomarkers of immunotoxicity. While the specificity and validity of certain cytokines as markers of adverse immune response has been established for chemicals, small and macromolecular drugs, research on their applicability for predicting and monitoring the immunotoxicity of engineered nanomaterials is still ongoing. The goal of this review is to provide guidelines as to important cytokines that can be utilized for evaluating the immunotoxicity of nanomaterials and to highlight the role of those cytokines in mediating adverse reactions, which is of particular importance for the clinical development of nanopharmaceuticals and other nanotechnology-based products. Importantly, the rational design of nanomaterials of low immunotoxicity will be discussed, focusing on synthetic nanodevices, with emphasis on both the nanoparticle-forming materials and the embedded cargoes.

Avirulent Toxoplasma gondii generates therapeutic antitumor immunity by reversing immunosuppression in the ovarian cancer microenvironment

Reversing tumor-associated immunosuppression seems necessary to stimulate effective therapeutic immunity against lethal epithelial tumors. Here, we show this goal can be addressed using cps, an avirulent, nonreplicating uracil auxotroph strain of the parasite Toxoplasma gondii (T. gondii), which preferentially invades immunosuppressive CD11c(+) antigen-presenting cells in the ovarian carcinoma microenvironment. Tumor-associated CD11c(+) cells invaded by cps were converted to immunostimulatory phenotypes, which expressed increased levels of the T-cell receptor costimulatory molecules CD80 and CD86. In response to cps treatment of the immunosuppressive ovarian tumor environment, CD11c(+) cells regained the ability to efficiently cross-present antigen and prime CD8(+) T-cell responses. Correspondingly, cps treatment markedly increased tumor antigen-specific responses by CD8(+) T cells. Adoptive transfer experiments showed that these antitumor T-cell responses were effective in suppressing solid tumor development. Indeed, intraperitoneal cps treatment triggered rejection of established ID8-VegfA tumors, an aggressive xenograft model of ovarian carcinoma, also conferring a survival benefit in a related aggressive model (ID8-Defb29/Vegf-A). The therapeutic benefit of cps treatment relied on expression of IL-12, but it was unexpectedly independent of MyD88 signaling as well as immune experience with T. gondii. Taken together, our results establish that cps preferentially invades tumor-associated antigen-presenting cells and restores their ability to trigger potent antitumor CD8(+) T-cell responses. Immunochemotherapeutic applications of cps might be broadly useful to reawaken natural immunity in the highly immunosuppressive microenvironment of most solid tumors.

Gold nanoparticle delivery of modified CpG stimulates macrophages and inhibits tumor growth for enhanced immunotherapy

Gold nanoparticle accumulation in immune cells has commonly been viewed as a side effect for cancer therapeutic delivery; however, this phenomenon can be utilized for developing gold nanoparticle mediated immunotherapy. Here, we conjugated a modified CpG oligodeoxynucleotide immune stimulant to gold nanoparticles using a simple and scalable self-assembled monolayer scheme that enhanced the functionality of CpG in vitro and in vivo. Nanoparticles can attenuate systemic side effects by enhancing CpG delivery passively to innate effector cells. The use of a triethylene glycol (TEG) spacer on top of the traditional poly-thymidine spacer increased CpG macrophage stimulatory effects without sacrificing DNA content on the nanoparticle, which directly correlates to particle uptake. In addition, the immune effects of modified CpG-AuNPs were altered by the core particle size, with smaller 15 nm AuNPs generating maximum immune response. These TEG modified CpG-AuNP complexes induced macrophage and dendritic cell tumor infiltration, significantly inhibited tumor growth, and promoted survival in mice when compared to treatments with free CpG.

Delivery of gene silencing agents for breast cancer therapy

The discovery of RNA interference has opened the door for the development of a new class of cancer therapeutics. Small inhibitory RNA oligos are being designed to specifically suppress expression of proteins that are traditionally considered nondruggable, and microRNAs are being evaluated to exert broad control of gene expression for inhibition of tumor growth. Since most naked molecules are not optimized for in vivo applications, the gene silencing agents need to be packaged into delivery vehicles in order to reach the target tissues as their destinations. Thus, the selection of the right delivery vehicles serves as a crucial step in the development of cancer therapeutics. The current review summarizes the status of gene silencing agents in breast cancer and recent development of candidate cancer drugs in clinical trials. Nanotechnology-based delivery vectors for the formulation and packaging of gene silencing agents are also described.

IL12B expression is sustained by a heterogenous population of myeloid lineages during tuberculosis

IL12B is required for resistance to Mycobacterium tuberculosis (Mtb) infection, promoting the initiation and maintenance of Mtb-specific effector responses. While this makes the IL12-pathway an attractive target for experimental tuberculosis (TB) therapies, data regarding what lineages express IL12B after infection is established are limited. This is not obvious in the lung, an organ in which both hematopoietic and non-hematopoietic lineages produce IL12p40 upon pathogen encounter. Here, we use radiation bone marrow chimeras and Yet40 reporter mice to determine what lineages produce IL12p40 during experimental TB. We observed that hematopoietic IL12p40-production was sufficient to control Mtb, with no contribution by non-hematopoietic lineages. Furthermore, rather than being produced by a single subset, IL12p40 was produced by cells that were heterogenous in their size, granularity, autofluorescence and expression of CD11c, CD11b and CD8α. While depending on the timepoint and tissue examined, the surface phenotype of IL12p40-producers most closely resembled macrophages based on previous surveys of lung myeloid lineages. Importantly, depletion of CD11c(hi) cells during infection had no affect on lung IL12p40-concentrations. Collectively, our data demonstrate that IL12p40 production is sustained by a heterogenous population of myeloid lineages during experimental TB, and that redundant mechanisms of IL12p40-production exist when CD11c(hi) lineages are absent.

Anti-radiation damage effect of polyethylenimine as a toll-like receptor 5 targeted agonist

A number of agents are now available for use in protecting against ionizing radiation. These radiation-protective agents, however, have many adverse effects. Efforts have been made to develop new radiation-protective agents for medical application. Here, we investigated whether a compound, polyethylenimine (PEI), which activates Toll-like receptor 5 (TLR5)-mediated NF-kB signaling pathways, could have an anti-radiation effect on a mouse model. First, a cell-based screening model for an agonist of TLR5-mediated NF-kB pathway was established and then validated by activation of TLR5-mediated NF-kB luciferase reporter activity with a known TLR5 agonist, flagellin. We found that PEI induced dose-dependent activation of the TLR5-mediated NF-kB pathway, indicating that PEI is indeed a TLR5 agonist. Furthermore, the anti-radiation effect of polyethylenimine was assessed using a γ-ray total body irradiation (TBI) mouse model. Compared with the irradiation control, both survival time and survival rate were significantly improved in mice that received either a low dose of polyethylenimine (P= 0.019) or a high dose of polyethylenimine (P< 0.001). We also observed a positive correlation between animal body weight and survival time in mice that received a low dose of polyethylenimine, a high dose of polyethylenimine and amifostine, over a period of 30 days, r= 0.42 (P< 0.02), 0.72 (P< 0.0001) and 0.95 (P< 0.0001), respectively, while a negative correlation between animal body weight and survival time was observed in the irradiation control (r= -0.89; P< 0.0001). These results indicate that polyethylenimine is a new TLR5 agonist with potential application in offering protection for patients receiving radiotherapy or in radiation-related accidents.

Lipidoid Nanoparticles Containing PD-L1 siRNA Delivered In Vivo Enter Kupffer Cells and Enhance NK and CD8(+) T Cell-mediated Hepatic Antiviral Immunity

Effective clinical application of antiviral immunotherapies necessitates enhancing the functional state of natural killer (NK) and CD8⁺ T cells. An important mechanism for the establishment of viral persistence in the liver is the activation of the PD-1/PD-L1 inhibitory pathway. To examine the role of hepatic myeloid PD-L1 expression during viral infection, we determined the magnitude and quality of antiviral immune responses by administering PD-L1 short-interfering RNA (siRNA) encapsulated in lipidoid nanoparticles (LNP) in mice. Our studies indicate that Kupffer cells (KC) preferentially engulfed PD-L1 LNP within a short period of time and silenced Pdl1 during adenovirus and MCMV infection leading to enhanced NK and CD8⁺ T cell intrahepatic accumulation, effector function (interferon (IFN)-γ and granzyme B (GrB) production), CD8⁺ T cell–mediated viral clearance, and memory. Our results demonstrate that PD-L1 knockdown on KCs is central in determining the outcome of liver viral infections, and they represent a new class of gene therapy.

Anti-tumor immunity: myeloid leukocytes control the immune landscape

The immune surveillance hypothesis proposed over 50 years ago that many precancerous lesions are eliminated without a histological trace due to immunological pressure. Since then, it has become apparent that both the tumor and the anti-cancer immune response evolve over a long period to allow the eventual escape of nascent precancerous lesions into full-blown tumors. Although primarily focusing on loss of antigenicity, the immunoediting hypothesis has gradually evolved to appreciate the role of active immunosuppression in tumor progression, where myeloid leukocytes are increasingly recognized as the major driving force. This review highlights recent studies implicating how myeloid cells with antigen-presenting capabilities are co-opted by tumors to promote malignant progression. Because at least some advanced tumors remain significantly immunogenic, these new studies add a tweak to the immunoediting hypothesis as well as a rationale to block immunosuppressive mechanisms as a first-line intervention in cancer patients.

Nanovector delivery of siRNA for cancer therapy

RNA interference holds the promise to knock down expression of every cancer gene. Both academic laboratories and pharmaceutical companies have committed heavily on manpower and financial resources to develop small interfering RNA (siRNA) cancer therapeutics over the last decade. Although significant advances have been made in the design of siRNA therapeutics and mechanism of action on cancer cell killing, there are still many hurdles to overcome including effective delivery of therapeutics in vivo. Nanotechnology has had an important role in the development of delivery vectors so far. This article summarizes current nanovectors for siRNA delivery, discusses technical challenges in overcoming biological barriers, and introduces the multistage vector system for tumor-specific delivery.

Dendritic cells the tumor microenvironment and the challenges for an effective antitumor vaccination

Many clinical trials have been carried out or are in progress to assess the therapeutic potential of dendritic-cell- (DC-) based vaccines on cancer patients, and recently the first DC-based vaccine for human cancer was approved by the FDA. Herewith, we describe the general characteristics of DCs and different strategies to generate effective antitumor DC vaccines. In recent years, the relevance of the tumor microenvironment in the progression of cancer has been highlighted. It has been shown that the tumor microenvironment is capable of inactivating various components of the immune system responsible for tumor clearance. In particular, the effect of the tumor microenvironment on antigen-presenting cells, such as DCs, does not only render these immune cells unable to induce specific immune responses, but also turns them into promoters of tumor growth. We also describe strategies likely to increase the efficacy of DC vaccines by reprogramming the immunosuppressive nature of the tumor microenvironment.

Toll-like receptors as novel therapeutic targets for ovarian cancer

Ovarian cancer (OC) is an aggressive disease that affects approximately 1 in 70 women and has a poor prognosis (<50%, 5-year survival rate), in part because it is often diagnosed at a late stage. There are three main types of OC: neoplasms of surface epithelial, germ cell, or stromal origin, with surface epithelial tumors comprising about 80% of all OCs. In addition to improving diagnostics, it is necessary to develop more effective treatments for epithelial-origin OC. Here, we describe the paradoxical roles of toll-like receptor (TLR) signaling in the progression of cancer and discuss how its modulation may result in decreased tumor growth and metastasis via the attenuation of proangiogenic cytokines and potentiation of proapoptotic factors. In particular, it has been found that TLR activity can behave like a “double-edged sword”, as its signaling pathways have been implicated as having both tumor-suppressive and tumor-promoting effects. With particular emphasis on OC, we discuss the need to consider the signaling details of TLRs and associated proteins in the multiple cell types present in the tumor milieu to achieve safe and effective design of TLR-based cancer therapies.

Adhesion to substrates induces dendritic cell endothelization and decreases immunological response

Dendritic cells (DCs) are antigen presenting cells capable of inducing specific immune responses against microbial infections, transplant antigens, or tumors. DCs have been shown to possess a high plasticity showing different phenotypes in response to their microenvironment. For example, tumor-associated DCs can acquire an angiogenic phenotype thus promoting tumor growth. Further, DCs cultured in vitro under different conditions are able to upregulate the expression of endothelial markers and to express angiogenic factors. Indeed, it has been shown that soluble factors such as VEGF of PGE-2, that are present in the microenvironment of several tumors, affect the biology of these cells. We hypothesize that in addition to soluble factors the adhesion to different substrates will also define the phenotype and function of DCs. Herewith we demonstrate that murine myeloid(m) DCs upregulate endothelial markers such as VE-Cadherin, and to a lesser extent TIE-2, and decrease their immune capabilities when cultured on solid surfaces as compared with the same cells cultured on ultra-low binding (ULB) surfaces. On the other hand, the expression of angiogenic molecules at the level of RNA was not different among these cultures. In order to further investigate this phenomenon we used the murine ID8 model of ovarian cancer which can generate solid tumors when cancer cells are injected subcutaneously or a malignant ascites when they are injected intraperitoneally. This model gave us the unique opportunity to investigate DCs in suspension or attached to solid surfaces under the influence of the same tumor cells. We were able to determine that DCs present in solid tumors showed higher levels of expression of endothelial markers and angiogenic molecules but were not able to respond to inflammatory stimuli at the same extent as DCs recovered from ascites. Moreover, mDCs cultured on ULB surfaces in the presence of tumor factors do not expressed endothelial markers. Taking into account all these data we consider that tumor factors might be responsible for inducing angiogenic properties in DCs, but that in some settings the expression of endothelial markers such as VE-Cadherin and TIE-2 might be a function of attachment to solid surfaces and independent of the angiogenic properties of these cells.

Reprogramming tumor-associated dendritic cells in vivo using miRNA mimetics triggers protective immunity against ovarian cancer

Modulating the activity of miRNAs provides opportunities for novel cancer interventions. However, low bioavailability and poor cellular uptake are major challenges for delivering miRNA mimetics specifically to tumor cells. Here, we took advantage of the spontaneous enhanced endocytic activity of ovarian cancer-associated dendritic cells (DC) to selectively supplement the immunostimulatory miRNA miR-155. In vivo processing of nanoparticles carrying oligonucleotide duplexes mimicking the bulged structure of endogenous pre-miRNA (but not siRNA-like oligonucleotides) dramatically augmented miR-155 activity without saturating the RNA-induced silencing complex. Endogenous processing of synthetic miR-155 favored Ago2 and, to a lesser extent, Ago4 loading, resulting in genome-wide transcriptional changes that included silencing of multiple immunosuppressive mediators. Correspondingly, tumor-infiltrating DCs were transformed from immunosuppressive to highly immunostimulatory cells capable of triggering potent antitumor responses that abrogated the progression of established ovarian cancers. Our results show both the feasibility and therapeutic potential of supplementing/replenishing miRNAs in vivo using nonviral approaches to boost protective immunity against lethal tumors. Thus, we provide a platform, an optimized design, and a mechanistic rationale for the clinical testing of nonviral miRNA mimetics.