Comparing the MRI appearance of the lymph nodes and spleen in wild-type and immuno-deficient mouse strains

Adoptive cell transfer therapy with ex vivo primed peripheral lymphocytes in combination with anti-PDL1 therapy effectively inhibits triple-negative breast cancer growth and metastasis

BACKGROUND

Adoptive cell transfer cancer immunotherapy holds promise for treating disseminated disease, yet generating sufficient numbers of lymphocytes with anti-cancer activity against diverse specificities remains a major challenge. We recently developed a novel procedure (ALECSAT) for selecting, expanding and maturating polyclonal lymphocytes from peripheral blood with the capacity to target malignant cells.

METHODS

Immunodeficient mice were challenged with triple-negative breast cancer cell lines or patient-derived xenografts (PDX) and treated with allogeneic or autologous ALECSAT cells with and without anti-PDL1 therapy to assess the capacity of ALECSAT cells to inhibit primary tumor growth and metastasis.

RESULTS

ALECSAT mono therapy inhibited metastasis, but did not inhibit primary tumor growth or prolong survival of tumor-bearing mice. In contrast, combined ALECSAT and anti-PDL1 therapy significantly inhibited primary tumor growth, nearly completely blocked metastasis, and prolonged survival of tumor-bearing mice.

CONCLUSIONS

Combined ALECSAT and anti-PDL1 therapy results in favorable anti-cancer responses in both cell line-derived xenograft and autologous PDX models of advanced triple-negative breast cancer.

Tolerogenic Lipid Nanoparticles for Delivering Self-Antigen mRNA for the Treatment of Experimental Autoimmune Encephalomyelitis

Multiple sclerosis is a disease caused by autoantigen-responsive immune cells that disrupt the myelin in the central nervous system (CNS). Although immunosuppressive drugs are used to suppress symptoms, no definitive therapy exists. As in the experimental autoimmune encephalitis (EAE) model of multiple sclerosis, a partial sequence of the myelin oligodendrocyte glycoprotein (MOG35-55) was identified as a causative autoantigen. This suggests that the induction of immune tolerance that is specific to MOG35-55 would be a fundamental treatment for EAE. We previously reported that lipid nanoparticles (LNPs) containing an anionic phospholipid, phosphatidylserine (PS), in their lipid composition, can be used to deliver mRNA and that this leads to proteins of interest to be expressed in the spleen. In addition to the targeting capability of PS, PS molecules avoid activating the immune system. Physiologically, the recognition of PS on apoptotic cells suppresses immune activation against these cells by releasing cytokines, such as interleukin-10 (IL-10) and transforming growth factor (TGF)-β that negatively regulate immunity. In this study, we tested whether mRNA delivery of autoantigens to the spleen by PS-LNPs causes the expression of MOG35-55 antigens with minimal immune stimulation and whether this could be used to treat an EAE model by inducing immune tolerance.

Evaluation of Candidate Theranostics for 227Th/89Zr Paired Radioimmunotherapy of Lymphoma

²²⁷Th is a promising radioisotope for targeted α-particle therapy. It produces 5 α-particles through its decay, with the clinically approved ²²³Ra as its first daughter. There is an ample supply of ²²⁷Th, allowing for clinical use; however, the chemical challenges of chelating this large tetravalent f-block cation are considerable. Using the CD20-targeting antibody ofatumumab, we evaluated chelation of ²²⁷Th⁴⁺ for α-particle-emitting and radiotheranostic applications. Methods: We compared 4 bifunctional chelators for thorium radiopharmaceutical preparation: S-2-(4-Isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA), 2-(4-isothicyanatobenzyl)-1,2,7,10,13-hexaazacyclooctadecane-1,4,7,10,13,16-hexaacetic acid (p-SCN-Bn-HEHA), p-isothiacyanatophenyl-1-hydroxy-2-oxopiperidine-desferrioxamine (DFOcyclo*-p-Phe-NCS), and macrocyclic 1,2-HOPO N-hydroxysuccinimide (L804-NHS). Immunoconstructs were evaluated for yield, purity, and stability in vitro and in vivo. Tumor targeting of the lead ²²⁷Th-labeled compound in vivo was performed in CD20-expressing models and compared with a companion ⁸⁹Zr-labeled PET agent. Results: ²²⁷Th-labeled ofatumumab-chelator constructs were synthesized to a radiochemical purity of more than 95%, excepting HEHA. ²²⁷Th-HEHA-ofatumumab showed moderate in vitro stability. ²²⁷Th-DFOcyclo*-ofatumumab presented excellent ²²⁷Th labeling efficiency; however, high liver and spleen uptake was revealed in vivo, indicative of aggregation. ²²⁷Th-DOTA-ofatumumab labeled poorly, yielding no more than 5%, with low specific activity (0.08 GBq/g) and modest long-term in vitro stability (<80%). ²²⁷Th-L804-ofatumumab coordinated ²²⁷Th rapidly and efficiently at high yields, purity, and specific activity (8 GBq/g) and demonstrated extended stability. In vivo tumor targeting confirmed the utility of this chelator, and the diagnostic analog, ⁸⁹Zr-L804-ofatumumab, showed organ distribution matching that of ²²⁷Th to delineate SU-DHL-6 tumors. Conclusion: Commercially available and novel chelators for ²²⁷Th showed a range of performances. The L804 chelator can be used with potent radiotheranostic capabilities for ⁸⁹Zr/²²⁷Th quantitative imaging and α-particle therapy.

Preclinical PET and MR Evaluation of 89Zr- and 68Ga-Labeled Nanodiamonds in Mice over Different Time Scales

Nanodiamonds (NDs) have high potential as a drug carrier and in combination with nitrogen vacancies (NV centers) for highly sensitive MR-imaging after hyperpolarization. However, little remains known about their physiological properties in vivo. PET imaging allows further evaluation due to its quantitative properties and high sensitivity. Thus, we aimed to create a preclinical platform for PET and MR evaluation of surface-modified NDs by radiolabeling with both short- and long-lived radiotracers. Serum albumin coated NDs, functionalized with PEG groups and the chelator deferoxamine, were labeled either with zirconium-89 or gallium-68. Their biodistribution was assessed in two different mouse strains. PET scans were performed at various time points up to 7 d after i.v. injection. Anatomical correlation was provided by additional MRI in a subset of animals. PET results were validated by ex vivo quantification of the excised organs using a gamma counter. Radiolabeled NDs accumulated rapidly in the liver and spleen with a slight increase over time, while rapid washout from the blood pool was observed. Significant differences between the investigated radionuclides were only observed for the spleen (1 h). In summary, we successfully created a preclinical PET and MR imaging platform for the evaluation of the biodistribution of NDs over different time scales.

Subcutaneous delivery of a dendrimer-BH3 mimetic improves lymphatic uptake and survival in lymphoma

As a malignant tumour of lymphatic origin, B-cell lymphoma represents a significant challenge for drug delivery, where effective therapies must access malignant cells in the blood, organs and lymphatics while avoiding off-target toxicity. Subcutaneous (SC) administration of nanomedicines allows preferential access to both the lymphatic and blood systems and may therefore provide a route to enhanced drug exposure to lymphomas. Here we examine the impact of SC dosing on lymphatic exposure, pharmacokinetics (PK), and efficacy of AZD0466, a small molecule dual Bcl-2/Bcl-xL inhibitor conjugated to a 'DEP®' G5 poly-l-lysine dendrimer. PK studies reveal that the plasma half-life of the dendrimer-drug conjugate is 8-times longer than that of drug alone, providing evidence of slow release from the circulating dendrimer nanocarrier. The SC dosed construct also shows preferential lymphatic transport, with over 50% of the bioavailable dose recovered in thoracic lymph. Increases in dose (up to 400 mg/kg) are well tolerated after SC administration and studies in a model of disseminated lymphoma in mice show that high dose SC treatment outperforms IV administration using doses that lead to similar total plasma exposure (lower peak concentrations but extended exposure after SC). These data show that the DEP® dendrimer can act as a circulating drug depot accessing both the lymphatic and blood circulatory systems. SC administration improves lymphatic exposure and facilitates higher dose administration due to improved tolerability. Higher dose SC administration also results in improved efficacy, suggesting that drug delivery systems that access both plasma and lymph hold significant potential for the treatment of haematological cancers where lymphatic and extranodal dissemination are poor prognostic factors.

A modular, injectable, non-covalently assembled hydrogel system features widescale tunable degradability for controlled release and tissue integration

Biomaterials with attenuated adverse host tissue reactions, and meanwhile, combining biocompatibility with mimicry of mechanical and biochemical cues of native extracellular matrices (ECM) to promote integration and regeneration of tissues are important for many biomedical applications. Further, the materials should also be tailorable to feature desired application-related functions, like tunable degradability, injectability, or controlled release of bioactive molecules. Herein, a non-covalently assembled, injectable hydrogel system based on oligopeptides interacting with sulphated polysaccharides is reported, showing high tolerability and biocompatibility in immunocompetent hairless mice. Altering the peptide or polysaccharide component considerably varies the in vivo degradation rate of the hydrogels, ranging from a half-life of three weeks to no detectable degradation after three months. The hydrogel with sulphated low molecular weight hyaluronic acid exhibits sustained degradation-mediated release of heparin-binding molecules in vivo, as shown by small animal magnetic resonance imaging and fluorescence imaging, and enhances the expression of vascular endothelial growth factor in hydrogel surrounding. In vitro investigations indicate that M2-macrophages could be responsible for the moderate difference in pro-angiogenic effects. The ECM-mimetic and injectable hydrogels represent tunable bioactive scaffolds for tissue engineering, also enabling controlled release of heparin-binding signalling molecules including many growth factors.

T-cells produce acidic niches in lymph nodes to suppress their own effector functions

The acidic pH of tumors profoundly inhibits effector functions of activated CD8 + T-cells. We hypothesize that this is a physiological process in immune regulation, and that it occurs within lymph nodes (LNs), which are likely acidic because of low convective flow and high glucose metabolism. Here we show by in vivo fluorescence and MR imaging, that LN paracortical zones are profoundly acidic. These acidic niches are absent in athymic Nu/Nu and lymphodepleted mice, implicating T-cells in the acidifying process. T-cell glycolysis is inhibited at the low pH observed in LNs. We show that this is due to acid inhibition of monocarboxylate transporters (MCTs), resulting in a negative feedback on glycolytic rate. Importantly, we demonstrate that this acid pH does not hinder initial activation of naïve T-cells by dendritic cells. Thus, we describe an acidic niche within the immune system, and demonstrate its physiological role in regulating T-cell activation.

An in silico model of cytotoxic T-lymphocyte activation in the lymph node following short peptide vaccination

Tumour immunotherapy is dependent upon activation and expansion of tumour-targetting immune cells, known as cytotoxic T-lymphocytes (CTLs). Cancer vaccines developed in the past have had limited success and the mechanisms resulting in failure are not well characterized. To elucidate these mechanisms, we developed a human-parametrized, in silico, agent-based model of vaccination-driven CTL activation within a clinical short-peptide vaccination context. The simulations predict a sharp transition in the probability of CTL activation, which occurs with variation in the separation rate (or off-rate) of tumour-specific immune response-inducing peptides (cognate antigen) from the major histocompatibility class I (MHC-I) receptors of dendritic cells (DCs) originally at the vaccination site. For peptides with MHC-I off-rates beyond this transition, it is predicted that no vaccination strategy will lead to successful expansion of CTLs. For slower off-rates, below the transition, the probability of CTL activation becomes sensitive to the numbers of DCs and T cells that interact subsequent to DC migration to the draining lymph node of the vaccination site. Thus, the off-rate is a key determinant of vaccine design.

Immune-relevant aspects of murine models of head and neck cancer

Head and neck cancers (HNCs) cause significant mortality and morbidity. There have been few advances in therapeutic management of HNC in the past 4 to 5 decades, which support the need for studies focusing on HNC biology. In recent years, increased recognition of the relevance of the host response in cancer progression has led to novel therapeutic strategies and putative biomarkers of tumor aggressiveness. However, tumor-immune interactions are highly complex and vary with cancer type. Pre-clinical, in vivo models represent an important and necessary step in understanding biological processes involved in development, progression and treatment of HNC. Rodents (mice, rats, hamsters) are the most frequently used animal models in HNC research. The relevance and utility of information generated by studies in murine models is unquestionable, but it is also limited in application to tumor-immune interactions. In this review, we present information regarding the immune-specific characteristics of the murine models most commonly used in HNC research, including immunocompromised and immunocompetent animals. The particular characteristics of xenograft, chemically induced, syngeneic, transgenic, and humanized models are discussed in order to provide context and insight for researchers interested in the in vivo study of tumor-immune interactions in HNC.

ImmunoPET of Malignant and Normal B Cells with 89Zr- and 124I-Labeled Obinutuzumab Antibody Fragments Reveals Differential CD20 Internalization In Vivo

Purpose: The B-cell antigen CD20 provides a target for antibody-based positron emission tomography (immunoPET). We engineered antibody fragments targeting human CD20 and studied their potential as immunoPET tracers in transgenic mice (huCD20TM) and in a murine lymphoma model expressing human CD20.Experimental Design: Anti-CD20 cys-diabody (cDb) and cys-minibody (cMb) based on rituximab and obinutuzumab (GA101) were radioiodinated and used for immunoPET imaging of a murine lymphoma model. Pairwise comparison of obinutuzumab-based antibody fragments labeled with residualizing (⁸⁹Zr) versus non-residualizing (¹²⁴I) radionuclides by region of interest analysis of serial PET images was conducted both in the murine lymphoma model and in huCD20TM to assess antigen modulation in vivoResults:¹²⁴I-GAcDb and ¹²⁴I-GAcMb produced high-contrast immunoPET images of B-cell lymphoma and outperformed the respective rituximab-based tracers. ImmunoPET imaging of huCD20TM showed specific uptake in lymphoid tissues. The use of the radiometal ⁸⁹Zr as alternative label for GAcDb and GAcMb yielded greater target-specific uptake and retention compared with ¹²⁴I-labeled tracers. Pairwise comparison of ⁸⁹Zr- and ¹²⁴I-labeled GAcDb and GAcMb allowed assessment of in vivo internalization of CD20/antibody complexes and revealed that CD20 internalization differs between malignant and endogenous B cells.Conclusions: These obinutuzumab-based PET tracers have the ability to noninvasively and quantitatively monitor CD20-expression and have revealed insights into CD20 internalization upon antibody binding in vivo Because they are based on a humanized mAb they have the potential for direct clinical translation and could improve patient selection for targeted therapy, dosimetry prior to radioimmunotherapy, and prediction of response to therapy. Clin Cancer Res; 23(23); 7242-52. ©2017 AACR.

A longitudinal MRI study on lymph nodes histiocytosis of a xenograft cancer model

BACKGROUND

Efforts are continuously made to detect and investigate the pivotal processes and interplay between the response of sentinel lymph node and malignant cells from a primary tumor. Conversely, some frequently used tumor animal models, such as human cancer xenografts, rarely feature metastasis. Therefore, lymph node alterations are seldom assessed. We consider that studying lymph node response could contribute to the understanding of host reaction to cancer. In the present study, we explored the presence of regional lymph node alterations in parallel with tumor growth using a pancreatic tumor xenograft model which does not develop metastasis.

METHODS AND FINDINGS

We established an animal cancer model by the subcutaneous inoculation of PANC-1 (a metastatic human pancreatic cancer cell line) in the left upper flank of athymic nude mice. Tumor animals, along with controls (n = 7 / group) were subjected to Magnetic Resonance Imaging (MRI) in order to follow tumor growth and brachial and axillary lymph nodes alterations over several weeks. Further histological analyses were performed at the end of the study. The individual average of the different lymph nodes sizes was 15-40% larger in the tumor animals compared to control animals at week 8 to week 20. The tumor size and lymph node size were not correlated. Histological analysis of the lymph nodes showed paracortical histiocytosis. No metastasis to lymph nodes could be detected by histology. In tumor bearing animals, histiocytosis was associated with isolated apoptotic bodies and migration of human tumoral cells was confirmed by specific immunostaining of human origin markers.

CONCLUSIONS

The lack of metastasis as well as the pathological manifestation of the lymph node alteration in this pre-clinical model established here parallels findings in patients with sinus histiocytosis that is correlated with improved survival.

A Tunable Diffusion-Consumption Mechanism of Cytokine Propagation Enables Plasticity in Cell-to-Cell Communication in the Immune System

Immune cells communicate by exchanging cytokines to achieve a context-appropriate response, but the distances over which such communication happens are not known. Here, we used theoretical considerations and experimental models of immune responses in vitro and in vivo to quantify the spatial extent of cytokine communications in dense tissues. We established that competition between cytokine diffusion and consumption generated spatial niches of high cytokine concentrations with sharp boundaries. The size of these self-assembled niches scaled with the density of cytokine-consuming cells, a parameter that gets tuned during immune responses. In vivo, we measured interactions on length scales of 80-120 μm, which resulted in a high degree of cell-to-cell variance in cytokine exposure. Such heterogeneous distributions of cytokines were a source of non-genetic cell-to-cell variability that is often overlooked in single-cell studies. Our findings thus provide a basis for understanding variability in the patterning of immune responses by diffusible factors.

Mapping Sentinel Lymph Node Metastasis by Dual-probe Optical Imaging

Purpose: Sentinel lymph node biopsy (SLNB) has emerged as the preferred standard procedure in patients with breast cancer, melanoma and other types of cancer. Herein, we developed a method to intra-operatively map SLNs and differentiate tumor metastases within SLNs at the same time, with the aim to provide more accurate and real-time intraoperative guidance. Experimental Design: Hyaluronic acid (HA), a ligand of lymphatic vessel endothelial hyaluronan receptor (LYVE)-1, is employed as a SLN mapping agent after being conjugated with a near-infrared fluorophore (Cy5.5). Different sized HAs (5, 10 and 20K) were tested in normal mice and mice with localized inflammation to optimize LN retention time and signal to background ratio. Cetuximab, an antibody against epidermal growth factor receptor (EGFR), and trastuzumab, an antibody against human epidermal growth factor receptor 2 (HER2), were labeled with near-infrared fluorophore (IRDye800) for detecting metastatic tumors. LN metastasis model was developed by hock injection of firefly luciferase engineered human head neck squamous carcinoma cancer UM-SCC-22B cells or human ovarian cancer SKOV-3 cells. The metastases within LNs were confirmed by bioluminescence imaging (BLI). IRDye800-Antibodies were intravenously administered 24 h before local administration of Cy5.5-HA. Optical imaging was then performed to identify nodal metastases. Results: Binding of HA with LYVE-1 was confirmed by ELISA and fluorescence staining. HA with a size of 10K was chosen based on the favorable migration and retention profile. After sequential administration of IRDye800-antibodies intravenously and Cy5.5-HA locally to a mouse model with LN metastases and fluorescence optical imaging, partially metastasized LNs were successfully distinguished from un-metastasized LNs and fully tumor occupied LNs, based on the different signal patterns. Conclusions: Fluorophore conjugated HA is a potential lymphatic mapping agent for SLNB. Dual-tracer imaging with the combination of lymphatic mapping agents and tumor targeting agents can identify tumor metastases within SLNs, thus may provide accurate and real-time intra-operative guidance to spare the time spent waiting for a biopsy result.

Metastatic breast cancer cells in lymph nodes increase nodal collagen density

The most life-threatening aspect of breast cancer is the occurrence of metastatic disease. The tumor draining lymph nodes typically are the first sites of metastasis in breast cancer. Collagen I fibers and the extracellular matrix have been implicated in breast cancer to form avenues for metastasis. In this study, we have investigated extracellular matrix molecules such as collagen I fibers in the lymph nodes of mice bearing orthotopic human breast cancer xenografts. The lymph nodes in mice with metastatic MDA-MB-231 and SUM159 tumor xenografts and tumor xenografts grown from circulating tumor cell lines displayed an increased collagen I density compared to mice with no tumor and mice with non-metastatic T-47D and MCF-7 tumor xenografts. These results suggest that cancer cells that have metastasized to the lymph nodes can modify the extracellular matrix components of these lymph nodes. Clinically, collagen density in the lymph nodes may be a good marker for identifying lymph nodes that have been invaded by breast cancer cells.

Comparative analysis of human ex vivo-generated platelets vs megakaryocyte-generated platelets in mice: a cautionary tale

Thrombopoiesis is the process by which megakaryocytes release platelets that circulate as uniform small, disc-shaped anucleate cytoplasmic fragments with critical roles in hemostasis and related biology. The exact mechanism of thrombopoiesis and the maturation pathways of platelets released into the circulation remain incompletely understood. We showed that ex vivo-generated murine megakaryocytes infused into mice release platelets within the pulmonary vasculature. Here we now show that infused human megakaryocytes also release platelets within the lungs of recipient mice. In addition, we observed a population of platelet-like particles (PLPs) in the infusate, which include platelets released during ex vivo growth conditions. By comparing these 2 platelet populations to human donor platelets, we found marked differences: platelets derived from infused megakaryocytes closely resembled infused donor platelets in morphology, size, and function. On the other hand, the PLP was a mixture of nonplatelet cellular fragments and nonuniform-sized, preactivated platelets mostly lacking surface CD42b that were rapidly cleared by macrophages. These data raise a cautionary note for the clinical use of human platelets released under standard ex vivo conditions. In contrast, human platelets released by intrapulmonary-entrapped megakaryocytes appear more physiologic in nature and nearly comparable to donor platelets for clinical application.

Anchoring dipalmitoyl phosphoethanolamine to nanoparticles boosts cellular uptake and fluorine-19 magnetic resonance signal

Magnetic resonance (MR) methods to detect and quantify fluorine (¹⁹F) nuclei provide the opportunity to study the fate of cellular transplants in vivo. Cells are typically labeled with ¹⁹F nanoparticles, introduced into living organisms and tracked by ¹⁹F MR methods. Background-free imaging and quantification of cell numbers are amongst the strengths of ¹⁹F MR-based cell tracking but challenges pertaining to signal sensitivity and cell detection exist. In this study we aimed to overcome these limitations by manipulating the aminophospholipid composition of ¹⁹F nanoparticles in order to promote their uptake by dendritic cells (DCs). As critical components of biological membranes, phosphatidylethanolamines (PE) were studied. Both microscopy and MR spectroscopy methods revealed a striking (at least one order of magnitude) increase in cytoplasmic uptake of ¹⁹F nanoparticles in DCs following enrichment with 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE). The impact of enriching ¹⁹F nanoparticles with PE on DC migration was also investigated. By manipulating the nanoparticle composition and as a result the cellular uptake we provide here one way of boosting ¹⁹F signal per cell in order to overcome some of the limitations related to ¹⁹F MR signal sensitivity. The boost in signal is ultimately necessary to detect and track cells in vivo.

Enhanced sonographic imaging to diagnose lymph node metastasis: importance of blood vessel volume and density

Lymph node size is an important variable in ultrasound diagnosis of lymph node metastasis. However, the size criterion often leads to oversight of tumor-positive lymph nodes within the range of "normal" size, such that more accurate diagnostic criteria for lymph node metastasis are required. In this study, we show how diagnosis of lymph node metastasis can be improved by evaluating changes in blood vessel volume and density using a novel contrast-enhanced high-frequency ultrasound (CE-HFUS) system with Sonazoid. An MRL/MpJ-lpr/lpr (MRL/lpr) mouse model of lymph node metastasis was used in which lymph nodes are similar in size to humans. Metastasis via lymphatic vessels to proper axillary lymph nodes (proper ALN) was induced by injection of tumor cells into the subiliac lymph nodes. Within 21 days of injection, significant increases in blood vessel volume and density, but no increases in the size of the proper ALNs, were observed. The increase in blood vessel density was confirmed with immunohistochemical analysis and was positively related to tumor cell proliferation as measured using bioluminescence imaging. Together, our results showed that alterations in blood vessel volume and density precede alterations in lymph node size in the early stages of lymph node metastasis. Detection of these changes by ultrasonography may offer new criteria for early diagnosis of lymph node metastasis.