Enhancement of antitumor response of staphylococcal enterotoxin C2 mutant 2M-118 by promoting cell-mediated antitumor immunity.

BACKGROUND: Staphylococcal enterotoxin C2 (SEC2) is used as an immunotherapeutic drug in China. However, SEC2 are limited due to its immunosuppressive and toxic effects. A SEC2 2M-118 (H118A/T20L/G22E) mutant generated by site-directed mutagenesis was studied to elucidate the underlying antitumor mechanism. METHODS: The effects of 2M-118 on mouse fibrosarcoma (Meth-A) cells and cytokine responses were tested in vitro using a transwell assay and ELISA, respectively. 2M-118 effect on immune function in tumor-bearing mice was tested. Cytokine levels and antitumor responses were measured using ELISA and flow cytometry, respectively. TUNEL staining and immunohistochemistry were employed to detect the tumor apoptosis and CD4+ and CD8+ tumor infiltrating lymphocytes (TILs) in tumor tissue. RESULTS: 2M-118 demonstrated the growth inhibition on tumor cells, increase of cytokines production (IL-2, IFN-γ, and TNF-α) and splenocyte proliferation in vitro. 2M-118 effectively inhibited tumor development and increased lymphocytes and cytokines in a tumor-bearing mouse model. Additionally, 2M-118 regulated the tumormicroenvironment by reducing the number of myeloid-derived suppressor cells (MDSCs), increasing the number of TILs, and inducing tumorcell apoptosis. CONCLUSION: 2M-118 promotes immune function and enhances antitumor response. This indicates that 2M-118 could potentially be developed as a novel anti-tumor drug with-highefficiencyandlowtoxicity.

PD1/PDL1 expression is associated with increased TIM3 expression and tumor-infiltrating T lymphocytes in fibroblastic tumors

PurposeThe combined therapy of inhibiting T cell immunoglobulin domain and mucin domain 3 (TIM3) and programmed cell death 1/programmed death-ligand 1 (PD1/PDL1) has shown encouraging therapeutic effects in some solid tumors. However, the expression of PD1/PDL1 and TIM3 in fibroblastic tumors is ill defined, which has limited the application of these immune checkpoint inhibitors in such tumors.MethodsImmunostaining of 68 tissue microarray cores of fibroblastic tumors, including intermediate dermatofibrosarcoma protuberans and malignant myxofibrosarcoma and adult-type fibrosarcoma, was used to determine the expression of PD1, PDL1 and TIM3, as well as their relationship with the accumulation of tumor-infiltrating T lymphocytes (TILs).ResultsBoth PD1 and PDL1 expression was only observed in a small proportion of fibroblastic tumors, whereas TIM3 was expressed in almost all tumors. However, only the positive expression of PDL1 was related to tumors with high grade and staging. A considerable number of TILs, including CD4- and CD8A-positive T cells and a small group of FoxP3-positive T cells, was also observed in most tumors. The density of TIM3 was positively correlated with that of TILs. Furthermore, higher densities of TIM3, CD4, CD8A and FoxP3 were observed in PD1 and PDL1 double-positive fibroblastic tumors.ConclusionsThis study indicates that TILs with high expression of TIM3 may contribute to immunosuppression in the tumor microenvironment of fibroblastic tumors. Patients with fibroblastic tumors with high expression of PD1/PDL1 and TIM3 may therefore benefit from combination therapy with PD1/PDL1 and TIM3 inhibitors.

PD1/PDL1 expression is associated with increased TIM3 expression and tumor-infiltrating T lymphocytes in fibroblastic tumors.

PURPOSE: The combined therapy of inhibiting T cell immunoglobulin domain and mucin domain 3 (TIM3) and programmed cell death 1/programmed death-ligand 1 (PD1/PDL1) has shown encouraging therapeutic effects in some solid tumors. However, the expression of PD1/PDL1 and TIM3 in fibroblastic tumors is ill defined, which has limited the application of these immune checkpoint inhibitors in such tumors. METHODS: Immunostaining of 68 tissue microarray cores of fibroblastic tumors, including intermediate dermatofibrosarcoma protuberans and malignant myxofibrosarcoma and adult-type fibrosarcoma, was used to determine the expression of PD1, PDL1 and TIM3, as well as their relationship with the accumulation of tumor-infiltrating T lymphocytes (TILs). RESULTS: Both PD1 and PDL1 expression was only observed in a small proportion of fibroblastic tumors, whereas TIM3 was expressed in almost all tumors. However, only the positive expression of PDL1 was related to tumors with high grade and staging. A considerable number of TILs, including CD4- and CD8A-positive T cells and a small group of FoxP3-positive T cells, was also observed in most tumors. The density of TIM3 was positively correlated with that of TILs. Furthermore, higher densities of TIM3, CD4, CD8A and FoxP3 were observed in PD1 and PDL1 double-positive fibroblastic tumors. CONCLUSIONS: This study indicates that TILs with high expression of TIM3 may contribute to immunosuppression in the tumor microenvironment of fibroblastic tumors. Patients with fibroblastic tumors with high expression of PD1/PDL1 and TIM3 may therefore benefit from combination therapy with PD1/PDL1 and TIM3 inhibitors.

Regulatory T cell differentiation is controlled by αKG-induced alterations in mitochondrial metabolism and lipid homeostasis.

Suppressive regulatory T cell (Treg) differentiation is controlled by diverse immunometabolic signaling pathways and intracellular metabolites. Here we show that cell-permeable α-ketoglutarate (αKG) alters the DNA methylation profile of naive CD4 T cells activated under Treg polarizing conditions, markedly attenuating FoxP3+ Treg differentiation and increasing inflammatory cytokines. Adoptive transfer of these T cells into tumor-bearing mice results in enhanced tumor infiltration, decreased FoxP3 expression, and delayed tumor growth. Mechanistically, αKG leads to an energetic state that is reprogrammed toward a mitochondrial metabolism, with increased oxidative phosphorylation and expression of mitochondrial complex enzymes. Furthermore, carbons from ectopic αKG are directly utilized in the generation of fatty acids, associated with lipidome remodeling and increased triacylglyceride stores. Notably, inhibition of either mitochondrial complex II or DGAT2-mediated triacylglyceride synthesis restores Treg differentiation and decreases the αKG-induced inflammatory phenotype. Thus, we identify a crosstalk between αKG, mitochondrial metabolism and triacylglyceride synthesis that controls Treg fate.

Inhibition of tumor-associated macrophages by trabectedin improves the antitumor adaptive immunity in response to anti-PD-1 therapy.

A considerable proportion of cancer patients are resistant or only partially responsive to immune checkpoint blockade immunotherapy. Tumor-Associated Macrophages (TAMs) infiltrating the tumor stroma suppress the adaptive immune responses and, hence, promote tumor immune evasion. Depletion of TAMs or modulation of their protumoral functions is actively pursued, with the purpose of relieving this state of immunesuppression. We previously reported that trabectedin, a registered antitumor compound, selectively reduces monocytes and TAMs in treated tumors. However, its putative effects on the adaptive immunity are still unclear. In this study, we investigated whether treatment of tumor-bearing mice with trabectedin modulates the presence and functional activity of T-lymphocytes. In treated tumors, there was a significant upregulation of T cell-associated genes, including CD3, CD8, perforin, granzyme B, and IFN-responsive genes (MX1, CXCL10, and PD-1), indicating that T lymphocytes were activated after treatment. Notably, the mRNA levels of the Pdcd1 gene, coding for PD-1, were strongly increased. Using a fibrosarcoma model poorly responsive to PD-1-immunotherapy, treatment with trabectedin prior to anti-PD-1 resulted in improved antitumor efficacy. In conclusion, pretreatment with trabectedin enhances the therapeutic response to checkpoint inhibitor-based immunotherapy. These findings provide a good rational for the combination of trabectedin with immunotherapy regimens.

T-regulatory cells predict clinical outcome in soft tissue sarcoma patients: a clinico-pathological study.

BACKGROUND: Soft tissue sarcomas (STS) are generally considered non-immunogenic, although specific subtypes respond to immunotherapy. Antitumour response within the tumour microenvironment relies on a balance between inhibitory and activating signals for tumour-infiltrating lymphocytes (TILs). This study analysed TILs and immune checkpoint molecules in STS, and assessed their prognostic impact regarding local recurrence (LR), distant metastasis (DM), and overall survival (OS). METHODS: One-hundred and ninety-two surgically treated STS patients (median age: 63.5 years; 103 males [53.6%]) were retrospectively included. Tissue microarrays were constructed, immunohistochemistry for PD-1, PD-L1, FOXP3, CD3, CD4, and CD8 performed, and staining assessed with multispectral imaging. TIL phenotype abundance and immune checkpoint markers were correlated with clinical and outcome parameters (LR, DM, and OS). RESULTS: Significant differences between histology and all immune checkpoint markers except for FOXP3+ and CD3-PD-L1+ cell subpopulations were found. Higher levels of PD-L1, PD-1, and any TIL phenotype were found in myxofibrosarcoma as compared to leiomyosarcoma (all p < 0.05). The presence of regulatory T cells (Tregs) was associated with increased LR risk (p = 0.006), irrespective of margins. Other TILs or immune checkpoint markers had no significant impact on outcome parameters. CONCLUSIONS: TIL and immune checkpoint marker levels are most abundant in myxofibrosarcoma. High Treg levels are independently associated with increased LR risk, irrespective of margins.

Isoginkgetin derivative IP2 enhances the adaptive immune response against tumor antigens.

The success of cancer immunotherapy relies on the induction of an immunoprotective response targeting tumor antigens (TAs) presented on MHC-I molecules. We demonstrated that the splicing inhibitor isoginkgetin and its water-soluble and non-toxic derivative IP2 act at the production stage of the pioneer translation products (PTPs). We showed that IP2 increases PTP-derived antigen presentation in cancer cells in vitro and impairs tumor growth in vivo. IP2 action is long-lasting and dependent on the CD8+ T cell response against TAs. We observed that the antigen repertoire displayed on MHC-I molecules at the surface of MCA205 fibrosarcoma is modified upon treatment with IP2. In particular, IP2 enhances the presentation of an exon-derived epitope from the tumor suppressor nischarin. The combination of IP2 with a peptide vaccine targeting the nischarin-derived epitope showed a synergistic antitumor effect in vivo. These findings identify the spliceosome as a druggable target for the development of epitope-based immunotherapies.

TGF-ßR inhibitor SB431542 restores immune suppression induced by regulatory B-T cell axis and decreases tumour burden in murine fibrosarcoma.

The contribution of immune cells in soft tissue sarcomas (STS) is not completely known and understanding their role is very essential for employing immunotherapy strategies. Here, we show that murine fibrosarcoma-conditioned medium promoted total spleen cell proliferation but inhibited T cell responses to mitogenic and allo-antigen-mediated stimulation. This increased proliferation was found to be in B cells resulting in generation of Breg further leading to Treg population. This was found to be the same in vitro and in vivo. The phenotype of these B cells was CD19+CD81+CD27+CD25+PD-L1hi and they secreted both IL-10 and TGF-ß. These tumor evoked Bregs (tBreg), when co-cultured with B depleted T cells, suppressed their proliferation in response to anti-CD3/CD28 stimulation. tBreg-induced suppression of T cell responses was not abrogated by the inhibition or neutralization of IL-10 but by the small molecule inhibitor of TGFß Receptor type I, SB431542. While SB531542 per se was not cytotoxic to tumor cells, administration of SB431542 in tumor-bearing mice (TBM) significantly reduced the tumor burden. In addition, the treatment significantly reduced Treg cells and rescued proliferation of T cells in response to mitogen and allo-antigen. Collectively, our results identify that tumor evoked Breg cells mediate T cell immune suppression through TGFß-mediated pathway and that targeting the Breg-Treg axis can be potentially used as an immunotherapy agent.

Optimized Dose of Dendritic Cell-based Vaccination in Experimental Model of Tumor Using Artificial Neural Network.

Previous studies have demonstrated that maturation of dendritic cells (DCs) by pathogenic components through pathogen-associated molecular patterns (PAMPs) such as Listeria monocytogenes lysate (LML) or CpG DNA can improve cancer vaccination in experimental models. In this study, a mathematical model based on an artificial neural network (ANN) was used to predict several patterns and dosage of matured DC administration for improved vaccination. The ANN model predicted that repeated co-injection of tumor antigen (TA)-loaded DCs matured with CpG (CpG-DC) and LML (List-DC) results in improved antitumor immune response as well as a reduction of immunosuppression in the tumor microenvironment. In the present study, we evaluated the ANN prediction accuracy about DC-based cancer vaccines pattern in the treatment of Wehi164 fibrosarcoma cancer-bearing mice. Our results showed that the administration of the DC vaccine according to ANN predicted pattern, leads to a decrease in the rate of tumor growth and size and augments CTL effector function. Furthermore, gene expression analysis confirmed an augmented immune response in the tumor microenvironment. Experimentations justified the validity of the ANN model forecast in the tumor growth and novel optimal dosage that led to more effective treatment.

NKTR-214 immunotherapy synergizes with radiotherapy to stimulate systemic CD8+ T cell responses capable of curing multi-focal cancer.

BACKGROUND: High-dose radiotherapy (RT) is known to be immunogenic, but is rarely capable of driving clinically relevant abscopal antitumor immunity as monotherapy. RT is known to increase antigen presentation, type I/II interferon responses, and immune cell trafficking to irradiated tumors. Bempegaldesleukin (NKTR-214) is a CD122-preferential interleukin 2 (IL-2) pathway agonist that has been shown to increase tumor-infiltrating lymphocytes, T cell clonality, and increase PD-1 expression. NKTR-214 has increased drug half-life, decreased toxicity, and increased CD8+ T cell and natural killer cell stimulation compared with IL-2. METHODS: Animals bearing bilateral subcutaneous MCA-205 fibrosarcoma or CT26 colorectal tumors were treated with NKTR-214, RT, or combination therapy, and tumor growth of irradiated and abscopal lesions was assessed. Focal RT was delivered using a small animal radiation research platform. Peripheral and tumor-infiltrating immune phenotype and functional analyses were performed by flow cytometry. RNA expression profiling from both irradiated and abscopal lesions was performed using microarray. RESULTS: We demonstrate synergy between RT of a single tumor and NKTR-214 systemic therapy resulting in dramatically increased cure rates of mice bearing bilateral tumors compared with RT or NKTR-214 therapy alone. Combination therapy resulted in increased magnitude and effector function of tumor-specific CD8+ T cell responses and increased trafficking of these T cells to both irradiated and distant, unirradiated, tumors. CONCLUSIONS: Given the increasing role of hypofractionated and stereotactic body RT as standard of care treatments in the management of locally advanced and metastatic cancer, these data have important implications for future clinical trial development. The combination of RT and NKTR-214 therapy potently stimulates systemic antitumor immunity and should be evaluated for the treatment of patients with locally advanced and metastatic solid tumors.

The role of regulatory T lymphocytes in immune control of MC-2 fibrosarcoma.

The role of T regulatory lymphocytes (Treg) particularly in cancer is well known. The goal of the present study was to determine the contribution of these lymphocytes in the regulation of anti-tumor immunity of CBA/HZgr mice against MC-2 fibrosarcoma (4th generation of methylcholanthrene induced tumor). The levels of T lymphocytes (CD4+, CD8+ and CD4+CD25+) were determined 8 and 20 days after tumor transplantation. Further, the role of CD4+CD25+ (Tregs) in tumor-host interaction was evaluated in vitro and in vivo by using specific monoclonal antibodies. We found that splenocytes of both control and Treg depleted tumor bearing mice strongly but differently inhibited growth of tumor cells in vitro. While splenocytes of untreated mice exhibited significant decrease of this activity (from 74.4% to 62.6% and 32.95%), the splenocytes of Treg depleted mice showed increase of this activity (from 79.5% to 84.3% and 86.2%) from day 6 to day 13 and day 21 after tumor grafting, respectively. Further, upon i.v. injecting specific monoclonal anti-Treg antibody tumor immediately prior to tumor cell intracutaneous transplantation, the tumor was rejected after initial growth. In treated mice, the incidence of Treg cells was very low initially, reaching normal values two weeks later. These animals were shown to be resistant to tumor transplantation four months later.

Peptide vaccinations elicited strong immune responses that were reboosted by anti-PD1 therapy in a patient with myxofibrosarcoma.

Peptide-based immunotherapy does not usually elicit strong immunological and clinical responses in patients with end-stage cancer, including sarcoma. Here we report a myxofibrosarcoma patient who showed a strong clinical response to peptide vaccinations and whose immune responses were reboosted by anti-PD1 therapy combined with peptide vaccinations. The 46-year-old man showed a strong response to the peptide vaccinations (papillomavirus binding factor peptide, survivin-2B peptide, incomplete Freund's adjuvant, and polyethylene glycol-conjugated interferon-alpha 2a) and subsequent wide necrosis and massive infiltration of CD8+ T cells in a recurrent tumor. The patient's immune responses weakened after surgical resection; however, they were reboosted following the administration of nivolumab combined with peptide vaccinations. Thus, anti-PD1 therapy combined with peptide vaccinations might be beneficial, as suggested by the observations in this sarcoma patient.

Effects of Dendritic Cell Vaccine Activated with Components of Lieshmania Major on Tumor Specific Response.

BACKGROUND: Dendritic cells (DCs) contribute essentially to the outset and course of immune responses. So in patients with malignancy, there have been considerable interests in use of these cells in different interventions. OBJECTIVE: To evaluate the impact of Leishmania major's components on DC maturation and their use as a therapeutic agent against tumor cells. METHODS: The cancer model was induced by injection of WEHI-164 cells (BALB/c derived fibrosarcoma cell line) subcutaneously in the right flank of animals. Bone-marrow derived DCs (BMDCs) were cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4. After 5 days, tumor lysate, Leishmania major's lysate, and Lipopolysaccharide (LPS) were added to the culture and incubated for 2 days. IL-12 production in DCs was measured by ELISA. For Immunotherapy, Mice received DCs subcutaneously around the tumor site. Two weeks after DCs injection, cytotoxicity assay and infiltration of CD8+ lymphocytes were evaluated. RESULTS: Our results showed that immunotherapy with dendritic cells exposed to Leishmania extract led to producing a higher amount of IL-12, compare to the control group. A considerable increment in specific cytotoxic T cells activity, diminished tumor growth rate and improved survival of immunized animals were seen. CONCLUSION: This study indicates that the use of Leishmania major extract, as well as LPS, can enhance the efficiency of DC-based vaccines and provides a basis for the use of Leishmania major in DC-targeted clinical therapies.

Batf3-Dependent Genes Control Tumor Rejection Induced by Dendritic Cells Independently of Cross-Presentation.

The BATF3-dependent cDC1 lineage of conventional dendritic cells (cDC) is required for rejection of immunogenic sarcomas and for rejection of progressive sarcomas during checkpoint blockade therapy. One unique function of the cDC1 lineage is the efficient cross-presentation of tumor-derived neoantigens to CD8+ T cells, but it is not clear that this is the only unique function of cDC1 required for tumor rejection. We previously showed that BATF3 functions during cDC1 lineage commitment to maintain IRF8 expression in the specified cDC1 progenitor. However, since cDC1 progenitors do not develop into mature cDC1s in Batf3 -/- mice, it is still unclear whether BATF3 has additional functions in mature cDC1 cells. A transgenic Irf8-Venus reporter allele increases IRF8 protein concentration sufficiently to allow autonomous cDC1 development in spleens of Batf3 -/- mice. These restored Batf3 -/- cDC1s are transcriptionally similar to control wild-type cDC1s but have reduced expression of a restricted set of cDC1-specific genes. Restored Batf3 -/- cDC1s are able to cross-present cell-associated antigens both in vitro and in vivo However, Batf3 -/- cDC1 exhibit altered characteristics in vivo and are unable to mediate tumor rejection. These results show that BATF3, in addition to regulating Irf8 expression to stabilize cDC1 lineage commitment, also controls expression of a small set of genes required for cDC1-mediated tumor rejection. These BATF3-regulated genes may be useful targets in immunotherapies aimed at promoting tumor rejection.

TRIM21 mediates antibody inhibition of adenovirus-based gene delivery and vaccination.

Adenovirus has enormous potential as a gene-therapy vector, but preexisting immunity limits its widespread application. What is responsible for this immune block is unclear because antibodies potently inhibit transgene expression without impeding gene transfer into target cells. Here we show that antibody prevention of adenoviral gene delivery in vivo is mediated by the cytosolic antibody receptor TRIM21. Genetic KO of TRIM21 or a single-antibody point mutation is sufficient to restore transgene expression to near-naïve immune levels. TRIM21 is also responsible for blocking cytotoxic T cell induction by vaccine vectors, preventing a protective response against subsequent influenza infection and an engrafted tumor. Furthermore, adenoviral preexisting immunity can lead to an augmented immune response upon i.v. administration of the vector. Transcriptomic analysis of vector-transduced tissue reveals that TRIM21 is responsible for the specific up-regulation of hundreds of immune genes, the majority of which are components of the intrinsic or innate response. Together, these data define a major mechanism underlying the preimmune block to adenovirus gene therapy and demonstrate that TRIM21 efficiently blocks gene delivery in vivo while simultaneously inducing a rapid program of immune transcription.

CD11c+ MHCIIlo GM-CSF-bone marrow-derived dendritic cells act as antigen donor cells and as antigen presenting cells in neoepitope-elicited tumor immunity against a mouse fibrosarcoma.

Dendritic cells play a critical role in initiating T-cell responses. In spite of this recognition, they have not been used widely as adjuvants, nor is the mechanism of their adjuvanticity fully understood. Here, using a mutated neoepitope of a mouse fibrosarcoma as the antigen, and tumor rejection as the end point, we show that dendritic cells but not macrophages possess superior adjuvanticity. Several types of dendritic cells, such as bone marrow-derived dendritic cells (GM-CSF cultured or FLT3-ligand induced) or monocyte-derived ones, are powerful adjuvants, although GM-CSF-cultured cells show the highest activity. Among these, the CD11c+ MHCIIlo sub-set, distinguishable by a distinct transcriptional profile including a higher expression of heat shock protein receptors CD91 and LOX1, mannose receptors and TLRs, is significantly superior to the CD11c+ MHCIIhi sub-set. Finally, dendritic cells exert their adjuvanticity by acting as both antigen donor cells (i.e., antigen reservoirs) as well as antigen presenting cells.

Disodium Cromolyn and Anti-podoplanin Antibodies Strongly Inhibit Growth of BHK 21/C13-derived Fibrosarcoma in a Chick Embryo Chorioallantoic Membrane Model.

AIM: To characterize baby hamster kidney fibroblast (BHK 21/C13) cells and test the effects of antibodies against podoplanin and disodium cromolyn on BHK 21/C13 cell line-derived tumors grown on chick embryo chorioallantoic membrane (CAM). MATERIAL AND METHODS: BHK 21/C13 cell-derived fibrosarcomas developed in hamsters were implanted on CAM and treated with anti-podoplanin antibodies and disodium cromolyn. BHK 21/C13 cell immunophenotype was assessed. RESULTS: Fibrosarcoma cells were positive for vimentin, CD117, smooth muscle actin, vascular endothelial growth factor epidermal growth factor receptor, homebox prospero gene 1 and negative for platelet-derived growth factor B, neuron-specific enolase, S100, CD34, Ewing sarcoma and podoplanin. CAM-grown fibrosarcomas were highly sensitive to disodium cromolyn and anti-podoplanin antibodies. CONCLUSION: Immunophenotyping BHK 21/C13 cells and their response to drugs represent the first step in revealing cell line utility and a reliable tool for experimental cancer research.

Noninvasive photoacoustic and fluorescent tracking of optical dye labeled T cellular activities of diseased sites at new depth.

The migration of immune cells is crucial to the immune response. Visualization of these processes has previously been limited because of the imaging depth. We developed a deep-penetrating, sensitive and high-resolution method to use fast photoacoustic tomography (PAT) to image the dynamic changes of T cells in lymph node and diseases at new depth (up to 9.5 mm). T cells labeled with NIR-797-isothiocyanate, an excellent near-infrared photoacoustic and fluorescent agent, were intravenously injected to the mice. We used fluorescence imaging to determine the location of T cells roughly and photoacoustic imaging is used to observe T-cell responses in diseased sites deeply and carefully. The dynamic changes of T cells in lymph node, acute disease (bacterial infection) and chronic disease (tumor) were observed noninvasively by photoacoustic and fluorescence imaging at different time points. T cells accumulated gradually and reached a maximum at 4 hours and declined afterwards in lymph node and bacterial infection site. At tumor model, T cells immigrated to the tumor with a maximum at 12 hours. Our study can not only provide a new observing method for immune activities tracking, but also enable continuous monitoring for therapeutic interventions.

Gold­manganese oxide nanocomposite suppresses hypoxia and augments pro-inflammatory cytokines in tumor associated macrophages.

The tumor microenvironment, essentially hypoxic, is sustained by the hypoxia inducing factor (HIF), released from the pro-tumorigenic tumor associated macrophages (TAMs), functionally identical to the M2 phenotype macrophages. Stability of HIF mainly depends on molecular oxygen and an iron-dependent enzyme prolyl hydroxylase, while its activity may be inhibited by high levels of reactive oxygen species and nitric oxide. The present work showcases a novel approach utilizing the anti-tumorigenic potential of a gold-manganese oxide nanocomposite material in the tumor microenvironment that affects tumor hypoxia, exploring the possibility of restoring the immunoregulatory nature of TAMs from their pro-tumorigenic state. Along with the biochemical markers, ELISA and FACS analyses have also confirmed the potential of these nanoparticles in reverting back the M2 phenotype of TAMs to their classically activated M1 phenotype.

Endoglin based in vivo near-infrared fluorescence imaging of tumor models in mice using activatable liposomes.

BACKGROUND: Endoglin (CD105) is overexpressed on tumor cells and tumor vasculatures, making it a potential target for diagnostic imaging and therapy of different neoplasms. Therefore, studies on nanocarrier systems designed for endoglin-directed diagnostic and drug delivery purposes would expose the feasibility of targeting endoglin with therapeutics. METHODS: Liposomes carrying high concentrations of a near-infrared fluorescent dye in the aqueous interior were prepared by the lipid film hydration and extrusion procedure, then conjugated to single chain antibody fragments either selective for murine endoglin (termed mEnd-IL) or directed towards human endoglin (termed hEnd-IL). A combination of Dynamic Light Scattering, electron microscopy, cell binding and uptake assays, confocal microscopy and in vivo fluorescence imaging of mice bearing xenografted human breast cancer and human fibrosarcoma models were implemented to elucidate the potentials of the liposomes. RESULTS: The mEnd-IL and hEnd-IL were highly selective for the respective murine- and human endoglin expressing cells in vitro and in vivo. Hence, the hEnd-IL bound distinctly to the tumor cells and enabled suitable fluorescence imaging of the tumors, whereas the mEnd-IL bound the tumor vasculature, but also to the liver, kidney and lung vasculature of mice. CONCLUSIONS: The work highlights key differences between targeting vascular (murine) and neoplastic (human) endoglin in animal studies, and suggests that the hEnd-IL can serve as a delivery system that targets human endoglin overexpressed in pathological conditions. GENERAL SIGNIFICANCE: The endoglin-targeting liposomes presented herewith represent strategic tools for the future implementation of endoglin-directed neoplastic and anti-angiogenic therapies.