Lessons for the Next Generation of Scientists from the Second Annual Arthur and Sandra Irving Cancer Immunology Symposium

The Arthur and Sandra Irving Cancer Immunology Symposium has been created as a platform for established cancer immunologists to mentor trainees and young investigators as they launch their research career in the field. By sharing their different paths to success, the senior faculty mentors provide an invaluable resource to support the development of the next generation of leaders in the cancer immunology community. This Commentary describes some of the key topics that were discussed during the 2022 symposium: scientific and career trajectory, leadership, mentoring, collaborations, and publishing. For each of these topics, established investigators discussed the elements that facilitate success in these areas as well as mistakes that can hinder progress. Herein, we outline the critical points raised in these discussions for establishing a successful independent research career. These points are highly relevant for the broader scientific community.

Sequential Chromogenic IHC: Spatial Analysis of Lymph Nodes Identifies Contact Interactions between Plasmacytoid Dendritic Cells and Plasmablasts

Recent clinical observations have emphasized the critical role that the spatial organization of immune cells in lymphoid structures plays in the success of cancer immunotherapy and patient survival. However, implementing sequential chromogenic IHC (scIHC) to analyze multiple biomarkers on a single tissue section has been limited because of a lack of a standardized, rigorous guide to the development of customized biomarker panels and a need for user-friendly analysis pipelines that can extract meaningful data. In this context, we provide a comprehensive guide for the development of novel biomarker panels for scIHC, using practical examples and illustrations to highlight the most common complications that can arise during the setup of a new biomarker panel, and provide detailed instructions on how to prevent and detect cross-reactivity between secondary reagents and carryover between detection antibodies. We also developed a novel analysis pipeline based on non-rigid tissue deformation correction, Cellpose-inspired automated cell segmentation, and computational network masking of low-quality data. We applied this biomarker panel and pipeline to study regional lymph nodes from patients with head and neck cancer, identifying novel contact interactions between plasmablasts and plasmacytoid dendritic cells in vivo. Given that Toll-like receptors, which are highly expressed in plasmacytoid dendritic cells, play a key role in vaccine efficacy, the significance of this cell-cell interaction decisively warrants further studies. In summary, this work provides a streamlined approach to the development of customized biomarker panels for scIHC that will ultimately improve our understanding of immune responses in cancer.

Significance

We present a comprehensive guide for developing customized biomarker panels to investigate cell-cell interactions in the context of immune responses in cancer. This approach revealed novel contact interactions between plasmablasts and plasmacytoid dendritic cells in lymph nodes from patients with head and neck cancer.

Secular equilibrium assessment in a CaWO4 target crystal from the dark matter experiment CRESST using Bayesian likelihood normalisation

CRESST is a leading direct detection sub-GeVc^-2 dark matter experiment. During its second phase, cryogenic bolometers were used to detect nuclear recoils off the CaWO₄ target crystal nuclei. The previously established electromagnetic background model relies on Secular Equilibrium (SE) assumptions. In this work, a validation of SE is attempted by comparing two likelihood-based normalisation results using a recently developed spectral template normalisation method based on Bayesian likelihood. Albeit we find deviations from SE in some cases we conclude that these deviations are artefacts of the fit and that the assumptions of SE is physically meaningful.

Exosomes, microvesicles, and other extracellular vesicles-a Keystone Symposia report

Extracellular vesicles (EVs) are small, lipid-bilayer-bound particles released by cells that can contain important bioactive molecules, including lipids, RNAs, and proteins. Once released in the extracellular environment, EVs can act as messengers locally as well as to distant tissues to coordinate tissue homeostasis and systemic responses. There is a growing interest in not only understanding the physiology of EVs as signaling particles but also leveraging them as minimally invasive diagnostic and prognostic biomarkers (e.g., they can be found in biofluids) and drug-delivery vehicles. On October 30-November 2, 2022, researchers in the EV field convened for the Keystone symposium "Exosomes, Microvesicles, and Other Extracellular Vesicles" to discuss developing standardized language and methodology, new data on the basic biology of EVs and potential clinical utility, as well as novel technologies to isolate and characterize EVs.

Cancer stem cell-derived extracellular vesicles preferentially target MHC-II-macrophages and PD1+ T cells in the tumor microenvironment

Immunotherapy is an approved treatment option for head and neck squamous cell carcinoma (HNSCC). However, the response rate to immune checkpoint blockade is only 13% for recurrent HNSCC, highlighting the urgent need to better understand tumor-immune interplay, with the ultimate goal of improving patient outcomes. HNSCC present high local recurrence rates and therapy resistance that can be attributed to the presence of cancer stem cells (CSC) within tumors. CSC exhibit singular properties that enable them to avoid immune detection and eradication. How CSC communicate with immune cells and which immune cell types are preferentially found within the CSC niche are still open questions. Here, we used genetic approaches to specifically label CSC-derived extracellular vesicles (EVs) and to perform Sortase-mediated in vivo proximity labeling of CSC niche cells. We identified specific immune cell subsets that were selectively targeted by EVCSC and that were found in the CSC niche. Native EVCSC preferentially targeted MHC-II-macrophages and PD1+ T cells in the tumor microenvironment, which were the same immune cell subsets enriched within the CSC niche. These observations indicate that the use of genetic technologies able to track EVs without in vitro isolation are a valuable tool to unveil the biology of native EVCSC.

Towards an automated data cleaning with deep learning in CRESST

The CRESST experiment employs cryogenic calorimeters for the sensitive measurement of nuclear recoils induced by dark matter particles. The recorded signals need to undergo a careful cleaning process to avoid wrongly reconstructed recoil energies caused by pile-up and read-out artefacts. We frame this process as a time series classification task and propose to automate it with neural networks. With a data set of over one million labeled records from 68 detectors, recorded between 2013 and 2019 by CRESST, we test the capability of four commonly used neural network architectures to learn the data cleaning task. Our best performing model achieves a balanced accuracy of 0.932 on our test set. We show on an exemplary detector that about half of the wrongly predicted events are in fact wrongly labeled events, and a large share of the remaining ones have a context-dependent ground truth. We furthermore evaluate the recall and selectivity of our classifiers with simulated data. The results confirm that the trained classifiers are well suited for the data cleaning task.

Senescent cell-derived extracellular vesicles are critical elements in senescence surveillance by recruiting antigen-presenting cells

Cellular senescence is a tumor suppressor mechanism that arrests cell cycle and initiates immune-mediated removal of senescent cells, a process known as senescence surveillance (SS). Senescent cells interact with their microenvironment through senescence-associated secretory phenotype (SASP). Current knowledge about the SASP has focused on soluble elements like cytokines. Extracellular vesicles (EVs) are membrane-bound, nanometer-sized particles that are emerging as a novel class of SASP factors. Whether EVs play a role in SS is unknown. Elucidating the role of EVs in SS will open new avenues for therapeutically targeting cellular senescence. In order to study if and how EVs contribute to SS, we inhibited EV release from senescent cells using dominant-negative mutant Rab35. This approach preserved secretion of soluble SASP elements while decreasing >95% the release of EVs from senescent cells. C57BL6 mice were challenged with EV-inhibited senescent cells and their numbers at the site of injection as well as immune infiltrates were quantified. Interfering with EV release led to the reduction of antigen-presenting cells including dendritic cells, macrophages, and B cells, which may contribute to the observed persistence of senescent cells. Interestingly, EV-inhibition reverted cellular senescence, promoted proliferation and tumor formation. Proteomic analysis revealed 35 proteins that were exclusively present on senescent cell-derived EVs, compared to those from their non-senescence counterparts. These results suggest that EVs have critical role in SS possibly via signaling to immune cells. Future work will explore whether T cells respond to EV-bound senescent cell antigens.

Integrated Training in Quantitative and Experimental Cancer Systems Biology, 5T32CA254888-02 and  CRUK/OHSU A29681

Class Switching is Required for Antigen-Dependent B cell Anti-Tumor Activity

Recent clinical studies demonstrated a positive correlation between B cell parameters and response to immune checkpoint blockade therapy. However, the potential mechanisms underlying B cell anti-tumor activities are still unclear. A better understanding of B cell-mediated immune responses in cancer will highlight novel vantage points to exploit therapeutically. To this end, we engineered tumor cells to express the B cell model antigen hen egg lysozyme (HEL). Adoptive transfer of CD45.1+ HEL-specific B cells (SWHEL B cells) into wild-type mice bearing HEL+ tumors significantly delayed tumor growth. SWHEL B cells from tumor-draining lymph nodes showed higher levels of MHCII expression, germinal center (GC) formation and class switch rate than non-tumor specific B cells. Of note, MD4 B cells, which recognize HEL but cannot class switch, were unable to control tumor growth, suggesting that immunoglobulin class M are not required for B cell anti-tumor activities. Accordingly, depletion of CD4 T cells (which are required for class switch) in mice bearing HEL+ tumors reverted the anti-tumor activity of SWHEL B cells. GC SWHEL B cells class switched to immunoglobulin G1 with a frequency between 20 and 80%, and resulted in a 10-fold increase of plasmablast (CD19+CD138+) and memory B cell (CD19+IgD-CD38+CCR6+) generation, as compared to non-tumor specific B cells. Collectively, these data point to a role for class-switched B cells and CD4 T cells in tumor immunosurveillance. Future studies will assess the ability of tumor antigen-specific B cells in priming naïve CD4 T cells and the role of other immunoglobulin classes in tumor control and escape.

Supported by V Foundation for Cancer Research V2019-012

An adjuvant strategy enabled by modulation of the physical properties of microbial ligands expands antigen immunogenicity

Activation of the innate immune system via pattern recognition receptors (PRRs) is key to generate lasting adaptive immunity. PRRs detect unique chemical patterns associated with invading microorganisms, but whether and how the physical properties of PRR ligands influence the development of the immune response remains unknown. Through the study of fungal mannans, we show that the physical form of PRR ligands dictates the immune response. Soluble mannans are immunosilent in the periphery but elicit a potent pro-inflammatory response in the draining lymph node (dLN). By modulating the physical form of mannans, we developed a formulation that targets both the periphery and the dLN. When combined with viral glycoprotein antigens, this mannan formulation broadens epitope recognition, elicits potent antigen-specific neutralizing antibodies, and confers protection against viral infections of the lung. Thus, the physical properties of microbial ligands determine the outcome of the immune response and can be harnessed for vaccine development.

Characterization of the tumor immune microenvironment of sinonasal squamous-cell carcinoma

BACKGROUND

Treatment and prognosis of sinonasal squamous-cell carcinoma (SNSCC) have not significantly improved despite improvements in radical therapy. Characterization of the tumor immune microenvironment (TiME) may identify patient subgroups associated with disease recurrence, and provide new biomarkers for improved patient stratification and treatment.

METHODS

The TiME was quantitatively evaluated by multiplex immunohistochemistry (mIHC) in archived tissue sections from 38 patients with SNSCC, and were assessed for differences between recurrent (n = 20) and nonrecurrent (n = 18) groups. Hierarchical clustering analyses were performed to identify phenotypic TiME subgroups within the cohort and were used to compare survival outcomes.

RESULTS

Our mIHC analysis revealed increased T-cell populations and decreased myeloid-cell populations in SNSCC patients without recurrent disease, as compared with patients with recurrent disease. Within T-cell subsets, there was a significantly higher percentage of granzyme B⁺ , T-bet⁺ , Eomes⁺ T cells, as well as higher proliferation of CD8⁺ T cells within the nonrecurrent group relative to the recurrent group. Furthermore, immune-cell complexity profiles of SNSCC revealed hyper- and hypo-T-cell-inflamed, myeloid-inflamed, B-cell-inflamed, and broadly hypoinflamed subtypes not previously identified by gene expression analyses. Our study revealed that presence of either hyper- or hypo-T-cell-inflamed TiME subtypes were associated with increased survival outcomes as compared with broadly hypoinflamed TiME subtypes (p = 0.035 and 0.0376, respectively).

CONCLUSIONS

The TiME of SNSCC reveals distinct subtypes, which may correlate with recurrence and survival outcomes.

Redirecting tumor macrophage activity to fight cancer: Make room for the next era of anti-cancer drugs

Functionally significant proteins expressed by tumor macrophages have emerged as promising anti-cancer targets. In this issue of Cancer Cell, Sun et al. identify two FDA-approved agents that together safely reprogram tumor macrophages into potent anti-tumor effectors, demonstrating the power of engaging both immune system arms to fight cancer.

Gene Expression Profiling of Lymph Node Sub-Capsular Sinus Macrophages in Cancer

Lymph nodes are key lymphoid organs collecting lymph fluid and migratory cells from the tissue area they survey. When cancerous cells arise within a tissue, the sentinel lymph node is the first immunological organ to mount an immune response. Sub-capsular sinus macrophages (SSMs) are specialized macrophages residing in the lymph nodes that play important roles as gatekeepers against particulate antigenic material. In the context of cancer, SSMs capture tumor-derived extracellular vesicles (tEVs), a form of particulate antigen released in high amounts by tumor cells. We and others have recently demonstrated that SSMs possess anti-tumor activity because in their absence tumors progress faster. A comprehensive profiling of SSMs represents an important first step to identify the cellular and molecular mechanisms responsible for SSM anti-tumor activity. Unfortunately, the isolation of SSMs for molecular analyses is very challenging. Here, we combined an optimized dissociation protocol, careful marker selection and stringent gating strategies to highly purify SSMs. We provide evidence of decreased T and B cell contamination, which allowed us to reveal the gene expression profile of this elusive macrophage subset. Squamous cell carcinomas induced an increase in the expression of Fc receptors, lysosomal and proteasomal enzymes in SSMs. Imaging of mouse and patient lymph nodes confirmed the presence of the top differentially expressed genes. These results suggest that SSMs respond to tumor formation by upregulating the machinery necessary for presentation of tumor particulate antigens to B cells.

An adjuvant strategy enabled by modulation of the physical properties of fungal mannans elicits pan-coronavirus reactive anti-SARS-CoV-2 Spike antibodies

Activation of the innate immune system via pattern recognition receptors (PRRs) is key to generate long-lasting adaptive immunity. While it is known that PRRs detect unique chemical patterns associated with invading microorganism, if and how the physical properties of PRR ligands influence development of the immune response is largely overlooked. Through the study of fungal mannans we present data that put the physical form of PRR ligands at the center of the process that determines the outcome of the immune response. Soluble mannans are immunosilent in the periphery but elicit a potent pro-inflammatory response in the draining lymph node (dLN). By modulating the physical form of mannans, we developed a formulation that targets both periphery and dLN. When combined with SARS-CoV-2 Spike, this formulation elicits neutralizing anti-SARS-CoV-2 antibodies that cross-react with pathogenic coronaviruses. Thus, the physical properties of fungal ligands can be harnessed for rational adjuvant design and vaccine development.

Abstract PO007: Tumor-immune communication via extracellular vesicles

Emerging evidence suggests that tumor-derived extracellular vesicles (tEVs) can influence immune cell behavior both locally within the tumor microenvironment and remotely by accessing the lymphatic and systemic circulation. The in vivo effects of such interactions before and after immunotherapy remain largely unappreciated. In this study, we aimed to develop a sensitive but stringent approach to identify host cells that interact with tEVs, with the ultimate goal of studying how tEV influence immune cells in their native microenvironment. Investigation of tEVs’ roles in cancer has been hampered by the need to isolate them before intravenous reinfusion in animals, which can introduce biases such as homogenization of tEV diversity, judgement of amount to reinfuse and assumptions on blood vs lymph biodistribution. To circumvent these issues, we and others pioneered the use of genetically engineered tumor cells to express membrane-bound reporters, which allow to label untouched, endogenously released tEVs and follow their interactions with immune cells. Still, the amount of reporter proteins that tEVs can carry is relatively small and thus the sensitivity of the approach is suboptimal. Here we addressed this issue by engineering tEVs to display a membrane-bound form of Sortase A, a bacterial transpeptidase that catalyzes the transfer of reporter proteins on the much bigger surface of tEV-binding cells. SrtA catalyzes the formation of a peptide bond between a consensus peptide and an N-terminal glycine of a nearby cell surface proteins (e.g. MHC-I, MHC-II, VE-Cadherin, CD19, integrins). We tested 4 different SrtA protein designs and selected the best performing construct for tEV studies. We genetically encoded SrtA in parental tumor cell lines, which then release SrtA as a tEV-bound transmembrane protein. Once a SrtA+ tEV interacts with a target cell in the presence of the consensus peptide (conjugated to a fluorescent reporter), SrtA catalyzes the formation of a covalent bond between the reporter and surface proteins of the tEV-binding cell. As expected, we observed significant increase in labeling when target cells were engineered to express a surface protein carrying 5 N-terminal glycine residues, which confirms that labeling of tEV-binding cells is due to actual transfer of fluorescent reporter – and not due to acyl intermediate formation. As compared to indirect labeling of EV-binding cells (e.g. using the EV marker CD63 fused to GFP), SrtA-based approach shows 1-2 log increase in sensitivity, depending on the EV-producing cell type. Overall, the catalytic nature of our EV reporter system lowers the amount of tEVs a host cell needs to bind before being detectable, thereby increasing sensitivity. We are currently testing our SrtA-based approach in vivo, where endogenous tEVs mainly accumulate in sentinel lymph nodes. We expect to unearth the full set of lymph node immune cells interacting with native tEVs and to identify whether immunecheckpoint blockade therapy affects tEV tropism toward immune cells.

Citation Format: Ferdinando Pucci, Nicklas Hamilton, Natalie Claudio, Randall Armstrong. Tumor-immune communication via extracellular vesicles [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO007.

Abstract CT183: CD5+ B-cell count is a favorable prognostic factor associated with progression-free survival in glioblastoma patients receiving chemoradiation and pembrolizumab

The exploratory endpoint for our prospective single-arm study (NCT 03347617) evaluated longitudinal changes in immune cell sub-populations (B-cells, T-cells, NK cells, monocytes, and myeloid cells) in 25 newly diagnosed glioblastoma patients who received standard of care chemoradiation with concurrent pembrolizumab after maximal safe resection. Patient demographics included the following: 15 males, 10 females, age range 25-72 years old, mean age 52 years old, 8 MGMT unmethylated, 17 MGMT methylated, 7 IDH1 mutant, and 18 IDH1 wild-type. Flow cytometry was performed on blood collected at predetermined timepoints (pre-treatment, post-radiation, suspected progression, and confirmed progression) and immune cell sub-populations were evaluated as covariates in survival analysis using Cox proportional hazards regression in R. CD5+ CD19+ B-cell count was significantly associated with progression-free survival at pre-treatment (hazard ratio (HR)= 0.76; likelihood ratio test (LRT) p=0.029) and post-radiation (HR = 0.16; LRT p=0.004) timepoints. No association with progression-free survival was found in 25 other immune cell sub-populations evaluated. The study will continue to monitor for progression. Results of imaging, tissue histology, overall survival analysis and functional studies in animal models are pending. Investigations of the immunological mechanisms underlying the potential anti-tumor activity of CD5+ B-cells are ongoing and include detection and characterization of anti-tumor antibodies, T cell-dependence of the response, and whether it is triggered by pembrolizumab. Modulating CD5+ B-cells, or the antibodies they produce, may have therapeutic implications in improving checkpoint inhibition in glioblastoma.

Citation Format: Cheryl J. Claunch, Claire Diaz, Riley A. Roth-Carter, Lauren Popp, Rochelle Fu, Amy E. Huddleston, Dana L. Moussalli, Julie Peterson, Kutluay Uluc, Laszlo Szidonya, Guang Fan, Ferdinando Pucci, Ramon F. Barajas, Leslie L. Muldoon, Edward A. Neuwelt, Prakash Ambady. CD5+ B-cell count is a favorable prognostic factor associated with progression-free survival in glioblastoma patients receiving chemoradiation and pembrolizumab [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT183.

Cell Surface Labeling by Engineered Extracellular Vesicles

Extracellular vesicles (EVs) can mediate local and long-range intercellular communication via cell surface signaling. In order to perform in vivo studies of unmanipulated, endogenously released EVs, sensitive but stringent approaches able to detect EV-cell surface interactions are needed. However, isolation and reinfusion of EVs can introduce biases. A rigorous way to study EVs in vivo is by genetically engineering membrane-bound reporters into parental cells. Still, the amount of reporter molecules that EVs can carry is relatively small, and thus, the sensitivity of the approach is suboptimal. This work addresses this issue by engineering EVs to display a membrane-bound form of Sortase A (SrtA), a bacterial transpeptidase that can catalyze the transfer of reporter molecules on the much bigger surface of EV-binding cells. SrtA design and reaction requirements are optimized and validated. Efficient in vitro labeling of EV-binding cells is achieved, even in the presence of only one N-terminal glycine on cell surface proteins. As compared to indirect labeling of EV-binding cells (e.g., using CD63-GFP fusion), the SrtA-based approach shows 1-2 log increase in sensitivity, depending on the EV source. This novel approach will be useful to identify and study the full set of host cells interacting with native EVs in vivo.

Bimodal CD40/Fas-Dependent Crosstalk between iNKT Cells and Tumor-Associated Macrophages Impairs Prostate Cancer Progression

Heterotypic cellular and molecular interactions in the tumor microenvironment (TME) control cancer progression. Here, we show that CD1d-restricted invariant natural killer (iNKT) cells control prostate cancer (PCa) progression by sculpting the TME. In a mouse PCa model, iNKT cells restrained the pro-angiogenic and immunosuppressive capabilities of tumor-infiltrating immune cells by reducing pro-angiogenic TIE2⁺, M2-like macrophages (TEMs), and sustaining pro-inflammatory M1-like macrophages. iNKT cells directly contacted macrophages in the PCa stroma, and iNKT cell transfer into tumor-bearing mice abated TEMs, delaying tumor progression. iNKT cells modulated macrophages through the cooperative engagement of CD1d, Fas, and CD40, which promoted selective killing of M2-like and survival of M1-like macrophages. Human PCa aggressiveness associate with reduced intra-tumoral iNKT cells, increased TEMs, and expression of pro-angiogenic genes, underscoring the clinical significance of this crosstalk. Therefore, iNKT cells may control PCa through mechanisms involving differential macrophage modulation, which may be harnessed for therapeutically reprogramming the TME.

Osteoblasts remotely supply lung tumors with cancer-promoting SiglecFhigh neutrophils

Bone marrow-derived myeloid cells can accumulate within tumors and foster cancer outgrowth. Local immune-neoplastic interactions have been intensively investigated, but the contribution of the systemic host environment to tumor growth remains poorly understood. Here, we show in mice and cancer patients (n = 70) that lung adenocarcinomas increase bone stromal activity in the absence of bone metastasis. Animal studies reveal that the cancer-induced bone phenotype involves bone-resident osteocalcin-expressing (Ocn⁺) osteoblastic cells. These cells promote cancer by remotely supplying a distinct subset of tumor-infiltrating SiglecF^high neutrophils, which exhibit cancer-promoting properties. Experimentally reducing Ocn⁺ cell numbers suppresses the neutrophil response and lung tumor outgrowth. These observations posit osteoblasts as remote regulators of lung cancer and identify SiglecF^high neutrophils as myeloid cell effectors of the osteoblast-driven protumoral response.

PF4 Promotes Platelet Production and Lung Cancer Growth

Co-option of host components by solid tumors facilitates cancer progression and can occur in both local tumor microenvironments and remote locations. At present, the signals involved in long-distance communication remain insufficiently understood. Here, we identify platelet factor 4 (PF4, CXCL4) as an endocrine factor whose overexpression in tumors correlates with decreased overall patient survival. Furthermore, engineered PF4 over-production in a Kras-driven lung adenocarcinoma genetic mouse model expanded megakaryopoiesis in bone marrow, augmented platelet accumulation in lungs, and accelerated de novo adenocarcinogenesis. Additionally, anti-platelet treatment controlled mouse lung cancer progression, further suggesting that platelets can modulate the tumor microenvironment to accelerate tumor outgrowth. These findings support PF4 as a cancer-enhancing endocrine signal that controls discrete aspects of bone marrow hematopoiesis and tumor microenvironment and that should be considered as a molecular target in anticancer therapy.

SCS macrophages suppress melanoma by restricting tumor-derived vesicle-B cell interactions

Tumor-derived extracellular vesicles (tEVs) are important signals in tumor-host cell communication, yet it remains unclear how endogenously produced tEVs affect the host in different areas of the body. We combined imaging and genetic analysis to track melanoma-derived vesicles at organismal, cellular, and molecular scales to show that endogenous tEVs efficiently disseminate via lymphatics and preferentially bind subcapsular sinus (SCS) CD169(+) macrophages in tumor-draining lymph nodes (tdLNs) in mice and humans. The CD169(+) macrophage layer physically blocks tEV dissemination but is undermined during tumor progression and by therapeutic agents. A disrupted SCS macrophage barrier enables tEVs to enter the lymph node cortex, interact with B cells, and foster tumor-promoting humoral immunity. Thus, CD169(+) macrophages may act as tumor suppressors by containing tEV spread and ensuing cancer-enhancing immunity.

Immunogenic Chemotherapy Sensitizes Tumors to Checkpoint Blockade Therapy

Checkpoint blockade immunotherapies can be extraordinarily effective, but might benefit only the minority of patients whose tumors are pre-infiltrated by T cells. Here, using lung adenocarcinoma mouse models, including genetic models, we show that autochthonous tumors that lacked T cell infiltration and resisted current treatment options could be successfully sensitized to host antitumor T cell immunity when appropriately selected immunogenic drugs (e.g., oxaliplatin combined with cyclophosphamide for treatment against tumors expressing oncogenic Kras and lacking Trp53) were used. The antitumor response was triggered by direct drug actions on tumor cells, relied on innate immune sensing through toll-like receptor 4 signaling, and ultimately depended on CD8(+) T cell antitumor immunity. Furthermore, instigating tumor infiltration by T cells sensitized tumors to checkpoint inhibition and controlled cancer durably. These findings indicate that the proportion of cancers responding to checkpoint therapy can be feasibly and substantially expanded by combining checkpoint blockade with immunogenic drugs.

Models of coronal heating, turbulence and fast reconnection

Coronal heating is at the origin of the EUV and X-ray emission and mass loss from the sun and many other stars. While different scenarios have been proposed to explain the heating of magnetically confined and open regions of the corona, they must all rely on the transfer, storage and dissipation of the abundant energy present in photospheric motions, which, coupled to magnetic fields, give rise to the complex phenomenology seen at the chromosphere and transition region (i.e. spicules, jets, 'tornadoes'). Here we discuss models and numerical simulations which rely on magnetic fields and electric currents both for energy transfer and for storage in the corona. We will revisit the sources and frequency spectrum of kinetic and electromagnetic energies, the role of boundary conditions, and the routes to small scales required for effective dissipation. Because reconnection in current sheets has been, and still is, one of the most important processes for coronal heating, we will also discuss recent aspects concerning the triggering of reconnection instabilities and the transition to fast reconnection.

PHD2 regulates arteriogenic macrophages through TIE2 signalling

Occlusion of the main arterial route redirects blood flow to the collateral circulation. We previously reported that macrophages genetically modified to express low levels of prolyl hydroxylase domain protein 2 (PHD2) display an arteriogenic phenotype, which promotes the formation of collateral vessels and protects the skeletal muscle from ischaemic necrosis. However, the molecular mechanisms underlying this process are unknown. Here, we demonstrate that femoral artery occlusion induces a switch in macrophage phenotype through angiopoietin-1 (ANG1)-mediated Phd2 repression. ANG blockade by a soluble trap prevented the downregulation of Phd2 expression in macrophages and their phenotypic switch, thus inhibiting collateral growth. ANG1-dependent Phd2 repression initiated a feed-forward loop mediated by the induction of the ANG receptor TIE2 in macrophages. Gene silencing and cell depletion strategies demonstrate that TIE2 induction in macrophages is required to promote their proarteriogenic functions, enabling collateral vessel formation following arterial obstruction. These results indicate an indispensable role for TIE2 in sustaining in situ programming of macrophages to a proarteriogenic, M2-like phenotype, suggesting possible new venues for the treatment of ischaemic disorders.

Molecular pathways: tumor-derived microvesicles and their interactions with immune cells in vivo

Cancer is not merely a cell-intrinsic genetic disease but also the result of complex cell-extrinsic interactions with host components, including immune cells. For example, effector T lymphocytes and natural killer cells are thought to participate in an immunosurveillance process, which eliminates neoplastic cells, whereas regulatory T lymphocytes and some myeloid cells, including macrophages, can create a milieu that prevents antitumor activity, supports tumor growth, and reduces survival of the host. Increasing evidence supports the notion that carcinoma cells communicate with immune cells directly, both within and away from the tumor stroma, and that this process fosters suppression of immunosurveillance and promotes tumor outgrowth. An important mode of communication between carcinoma cells and immune cells may involve tumor-derived microvesicles (tMV), also known as exosomes, ectosomes, or microparticles. These microvesicles carry lipids, proteins, mRNAs and microRNAs and travel short or long distances to deliver undegraded and undiluted material to other cells. Here, we consider the capacity of tMVs to control tumor-associated immune responses and highlight the known and unknown actions of tMVs in vivo. We also discuss why microvesicles may play a role in cancer diagnostics and prognostics and how they could be harnessed for anticancer therapy.

Angiotensin II drives the production of tumor-promoting macrophages

Macrophages frequently infiltrate tumors and can enhance cancer growth, yet the origins of the macrophage response are not well understood. Here we address molecular mechanisms of macrophage production in a conditional mouse model of lung adenocarcinoma. We report that overproduction of the peptide hormone Angiotensin II (AngII) in tumor-bearing mice amplifies self-renewing hematopoietic stem cells (HSCs) and macrophage progenitors. The process occurred in the spleen but not the bone marrow, and was independent of hemodynamic changes. The effects of AngII required direct hormone ligation on HSCs, depended on S1P(1) signaling, and allowed the extramedullary tissue to supply new tumor-associated macrophages throughout cancer progression. Conversely, blocking AngII production prevented cancer-induced HSC and macrophage progenitor amplification and thus restrained the macrophage response at its source. These findings indicate that AngII acts upstream of a potent macrophage amplification program and that tumors can remotely exploit the hormone's pathway to stimulate cancer-promoting immunity.

miR-511-3p modulates genetic programs of tumor-associated macrophages

Expression of the mannose receptor (MRC1/CD206) identifies macrophage subtypes, such as alternatively activated macrophages (AAMs) and M2-polarized tumor-associated macrophages (TAMs), which are endowed with tissue-remodeling, proangiogenic, and protumoral activity. However, the significance of MRC1 expression for TAM's protumoral activity is unclear. Here, we describe and characterize miR-511-3p, an intronic microRNA (miRNA) encoded by both mouse and human MRC1 genes. By using sensitive miRNA reporter vectors, we demonstrate robust expression and bioactivity of miR-511-3p in MRC1(+) AAMs and TAMs. Unexpectedly, enforced expression of miR-511-3p tuned down the protumoral gene signature of MRC1(+) TAMs and inhibited tumor growth. Our findings suggest that transcriptional activation of Mrc1 in TAMs evokes a genetic program orchestrated by miR-511-3p, which limits rather than enhances their protumoral functions. Besides uncovering a role for MRC1 as gatekeeper of TAM's protumoral genetic programs, these observations suggest that endogenous miRNAs may operate to establish thresholds for inflammatory cell activation in tumors.

Transplanted neural stem/precursor cells instruct phagocytes and reduce secondary tissue damage in the injured spinal cord

Transplanted neural stem/precursor cells possess peculiar therapeutic plasticity and can simultaneously instruct several therapeutic mechanisms in addition to cell replacement. Here, we interrogated the therapeutic plasticity of neural stem/precursor cells after their focal implantation in the severely contused spinal cord. We injected syngeneic neural stem/precursor cells at the proximal and distal ends of the contused mouse spinal cord and analysed locomotor functions and relevant secondary pathological events in the mice, cell fate of transplanted neural stem/precursor cells, and gene expression and inflammatory cell infiltration at the injured site. We used two different doses of neural stem/precursor cells and two treatment schedules, either subacute (7 days) or early chronic (21 days) neural stem/precursor cell transplantation after the induction of experimental thoracic severe spinal cord injury. Only the subacute transplant of neural stem/precursor cells enhanced the recovery of locomotor functions of mice with spinal cord injury. Transplanted neural stem/precursor cells survived undifferentiated at the level of the peri-lesion environment and established contacts with endogenous phagocytes via cellular-junctional coupling. This was associated with significant modulation of the expression levels of important inflammatory cell transcripts in vivo. Transplanted neural stem/precursor cells skewed the inflammatory cell infiltrate at the injured site by reducing the proportion of 'classically-activated' (M1-like) macrophages, while promoting the healing of the injured cord. We here identify a precise window of opportunity for the treatment of complex spinal cord injuries with therapeutically plastic somatic stem cells, and suggest that neural stem/precursor cells have the ability to re-programme the local inflammatory cell microenvironment from a 'hostile' to an 'instructive' role, thus facilitating the healing or regeneration past the lesion.

Abstract 2849: Tie2-expressing macrophages (TEM) depletion may enhance the clinical efficacy of combretastatin A-4-phosphate (CA-4-P)

Rationale & Hypothesis: Combretastatin A-4-phosphate (CA-4-P), a tubulin-binding, vascular-disrupting agent (VDA), induces rapid and selective tumor vascular shutdown and secondary tumor cell death. However, acute revascularization contributes to treatment resistance. A group of myeloid cells in tumors, tumor associated macrophages (TAMs) are known to drive angiogenesis and tumor progression. A potently pro-angiogenic subpopulation of TAMs has also been identified – Tie2 expressing monocytes (TEMs). We hypothesize that TAMs and/or TEMs infiltrate CA-4-P-treated tumors and promote tumor recovery.

Methodology, Results & Conclusions: Late-stage Polyoma Middle T (PyMT) spontaneous murine breast adenocarcinomas were excised from CA-4-P- and saline-treated mice. Significant tumor necrosis was evident 24h following a single injection of 50mg/kg CA-4-P (19.37 ± 4.60%) compared with saline controls (1.76 ± 0.34%). This was accompanied by tumor infiltration of F4/80+ TAMs (5.61 ± 0.46% of tumor volume w.r.t. 0.71± 0.08% in controls). Significant increases in the number of MMP-9 expressing macrophages, primarily TEMs, were evident following CA-4-P treatment (5.72 ± 0.34% compared with 2.66 ± 0.25% in controls).

TEMs were constitutive expressers of hypoxia-regulated CXCR4, which interacts via CXCL12 as a monocyte/macrophage chemoattractant. AMD3100, a chemical antagonist of CXCR4, was employed in combination with CA-4-P to prevent TEM recruitment into drug-treated tumors. TEM numbers were significantly depleted, which corresponded to heightened vascular damage (27% tumor necrosis w.r.t. 8% in CA-4-P alone). These results were replicated in a subcutaneous N202 murine mammary carcinoma model following 3 daily doses of 50mg/kg CA-4-P. Tumor growth was also significantly reduced at 72h in the combined treatment group (mean tumor volume ∼200mm3 w.r.t. ∼300mm3 in CA-4-P alone).

In addition, specific TEM depletion was achieved in the N202 carcinoma model via genetic manipulation and bone marrow transplantation. Tumor necrosis was increased significantly when CA-4-P was administered in combination with TEM depletion (22.45%), compared to saline controls (0.37%) and CA-4-P therapy alone (12.89%). This was attributed to a significant reduction in MMP-9 positive TEMs (0.08 ± 0.18% compared with 1.37 ± 0.21% in saline controls and 3.67± 0.11% in CA-4-P treated tumors).

Collectively, these data suggest that TEMs protect against CA-4-P or promote recovery of tumors following CA-4-P treatment. Therefore, targeting TEMs, in combination with vascular-disrupting agents such as CA-4-P may provide a novel therapeutic strategy for solid tumors.

A.F. Welford was funded by a Cancer Research UK PhD studentship.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2849. doi:10.1158/1538-7445.AM2011-2849

Targeting the ANG2/TIE2 axis inhibits tumor growth and metastasis by impairing angiogenesis and disabling rebounds of proangiogenic myeloid cells

Tumor-infiltrating myeloid cells convey proangiogenic programs that counteract the efficacy of antiangiogenic therapy. Here, we show that blocking angiopoietin-2 (ANG2), a TIE2 ligand and angiogenic factor expressed by activated endothelial cells (ECs), regresses the tumor vasculature and inhibits progression of late-stage, metastatic MMTV-PyMT mammary carcinomas and RIP1-Tag2 pancreatic insulinomas. ANG2 blockade did not inhibit recruitment of MRC1(+) TIE2-expressing macrophages (TEMs) but impeded their upregulation of Tie2, association with blood vessels, and ability to restore angiogenesis in tumors. Conditional Tie2 gene knockdown in TEMs was sufficient to decrease tumor angiogenesis. Our findings support a model wherein the ANG2-TIE2 axis mediates cell-to-cell interactions between TEMs and ECs that are important for tumor angiogenesis and can be targeted to induce effective antitumor responses.

TIE2-expressing macrophages limit the therapeutic efficacy of the vascular-disrupting agent combretastatin A4 phosphate in mice

Vascular-disrupting agents (VDAs) such as combretastatin A4 phosphate (CA4P) selectively disrupt blood vessels in tumors and induce tumor necrosis. However, tumors rapidly repopulate after treatment with such compounds. Here, we show that CA4P-induced vessel narrowing, hypoxia, and hemorrhagic necrosis in murine mammary tumors were accompanied by elevated tumor levels of the chemokine CXCL12 and infiltration by proangiogenic TIE2-expressing macrophages (TEMs). Inhibiting TEM recruitment to CA4P-treated tumors either by interfering pharmacologically with the CXCL12/CXCR4 axis or by genetically depleting TEMs in tumor-bearing mice markedly increased the efficacy of CA4P treatment. These data suggest that TEMs limit VDA-induced tumor injury and represent a potential target for improving the clinical efficacy of VDA-based therapies.

FcRgamma activation regulates inflammation-associated squamous carcinogenesis

Chronically activated leukocytes recruited to premalignant tissues functionally contribute to cancer development; however, mechanisms underlying pro- versus anti-tumor programming of neoplastic tissues by immune cells remain obscure. Using the K14-HPV16 mouse model of squamous carcinogenesis, we report that B cells and humoral immunity foster cancer development by activating Fcgamma receptors (FcgammaRs) on resident and recruited myeloid cells. Stromal accumulation of autoantibodies in premalignant skin, through their interaction with activating FcgammaRs, regulate recruitment, composition, and bioeffector functions of leukocytes in neoplastic tissue, which in turn promote neoplastic progression and subsequent carcinoma development. These findings support a model in which B cells, humoral immunity, and activating FcgammaRs are required for establishing chronic inflammatory programs that promote de novo carcinogenesis.

Survival of benthic foraminifera under hypoxic conditions: results of an experimental study using the CellTracker Green method

We present results of an experimental study, in which benthic foraminiferal faunas have been kept under strongly hypoxic conditions. Sixteen short sediment cores from a 35m deep site in the Adriatic Sea were incubated for a maximum of 69days. Some of the cores were air-bubbled and remained well oxygenated throughout the experiment. The other cores were bubbled with nitrogen; the overlying waters of these cores became strongly hypoxic, whereas the sediment remained virtually without oxygen. Live foraminifera have been inventoried with the CellTracker Green method. Our results show that all dominant taxa survive strongly hypoxic conditions. Nouria polymorphinoides and Nonionella turgida show a clear tendency to move to the sediment surface in the nitrogen-bubbled cores, whereas Bulimina spp. and Eggerella scabra do not show such a migrational response. We suggest that this is a response to the concentration of nutritional resources at the sediment-water interface.

Regulated and multiple miRNA and siRNA delivery into primary cells by a lentiviral platform

RNA interference (RNAi) has tremendous potential for investigating gene function and developing new therapies. However, the design and validation of proficient vehicles for stable and safe microRNA (miR) and small interfering RNA (siRNA) delivery into relevant target cells remains an active area of investigation. Here, we developed a lentiviral platform to efficiently coexpress one or more natural/artificial miR together with a gene of interest from constitutive or regulated polymerase-II (Pol-II) promoters. By swapping the stem-loop (sl) sequence of a selected primary transcript (pri-miR) with that of other miR or replacing the stem with an siRNA of choice, we consistently obtained robust expression of the chimeric/artificial miR in several cell types. We validated our platform transducing a panel of engineered cells stably expressing sensitive reporters for miR activity and on a natural target. This approach allowed us to quantitatively assess at steady state the target suppression activity and expression level of each delivered miR and to compare it to those of endogenous miR. Exogenous/artificial miR reached the concentration and activity typical of highly expressed natural miR without perturbing endogenous miR maturation or regulation. Finally, we demonstrate the robust performance of the platform reversing the anergic/suppressive phenotype of human primary regulatory T cells (Treg) by knocking-down their master gene Forkhead Transcription Factor P3 (FOXP3).

Tumor-targeted interferon-alpha delivery by Tie2-expressing monocytes inhibits tumor growth and metastasis

The use of type I interferons (IFNs) in cancer therapy has been limited by ineffective dosing and significant toxicity. Here, we exploited the tumor-homing ability of proangiogenic Tie2-expressing monocytes (TEMs) to deliver IFN-alpha to tumors. By transplanting hematopoietic progenitors transduced with a Tie2 promoter/enhancer-driven Ifna1 gene, we turned TEMs into IFN-alpha cell vehicles that efficiently targeted the IFN response to orthotopic human gliomas and spontaneous mouse mammary carcinomas and obtained significant antitumor responses and near complete abrogation of metastasis. TEM-mediated IFN-alpha delivery inhibited tumor angiogenesis and activated innate and adaptive immune cells but did not impair myelopoiesis and wound healing detectably. These results illustrate the therapeutic potential of gene- and cell-based IFN-alpha delivery and should allow the development of IFN treatments that more effectively treat cancer.

A combination of gefitinib and FOLFOX-4 as first-line treatment in advanced colorectal cancer patients. A GISCAD multicentre phase II study including a biological analysis of EGFR overexpression, amplification and NF-kB activation

Interesting activity has been reported by combining chemotherapy with cetuximab. An alternative approach for blocking EGFR function has been the development of small-molecule inhibitors of tyrosine kinase domain such as gefitinib. We designed a multicentre phase II study in advanced colorectal cancer combining gefitinib+FOLFOX in order to determine the activity and to relate EGFR expression and gene amplification and NF-kB activation to therapeutic results. Patients received FOLFOX-4 regimen plus gefitinib as first-line treatment. Tumour samples were analysed for EGFR protein expression by immunohistochemical analysis and for EGFR gene amplification by fluorescence in situ hybridisation (FISH), chromogenic in situ hybridisation (CISH) and NF-kB activation. Forty-three patients were enrolled into this study; 15 patients experienced a partial response (response rate=34.9%), whereas other 12 (27.9%) had a stable disease. Median progression-free survival (PFS) was 7.8 months and median overall survival (OS) was 13.9 months. We did not find any relationship with EGFR overexpression, gene amplification, while NF-kB activation was associated with a resistance to therapy. Gefitinib does not seem to increase the activity of FOLFOX in advanced colorectal cancer even in patients overexpressing EGFR or with EGFR amplification. Furthermore, while NF-kB activation seems to predict resistance to chemotherapy as demonstrated ‘in vitro’ models, gefitinib does not overcome this mechanism of resistance, as reported for cetuximab.

Identification of proangiogenic TIE2-expressing monocytes (TEMs) in human peripheral blood and cancer

Tumor-infiltrating myeloid cells, including tumor-associated macrophages (TAMs), have been implicated in tumor progression. We recently described a lineage of mouse monocytes characterized by expression of the Tie2 angiopoietin receptor and required for the vascularization and growth of several tumor models. Here, we report that TIE2 expression in human blood identifies a subset of monocytes distinct from classical inflammatory monocytes and comprised within the less abundant "resident" population. These TIE2-expressing monocytes (TEMs) accounted for 2% to 7% of blood mononuclear cells in healthy donors and were distinct from rare circulating endothelial cells and progenitors. In human cancer patients, TEMs were observed in the blood and, intriguingly, within the tumors, where they represented the main monocyte population distinct from TAMs. Conversely, TEMs were hardly detected in nonneoplastic tissues. In vitro, TEMs migrated toward angiopoietin-2, a TIE2 ligand released by activated endothelial cells and angiogenic vessels, suggesting a homing mechanism for TEMs to tumors. Purified human TEMs, but not TEM-depleted monocytes, markedly promoted angiogenesis in xenotransplanted human tumors, suggesting a potentially critical role of TEMs in human cancer progression. Human TEMs may provide a novel, biologically relevant marker of angiogenesis and represent a previously unrecognized target of cancer therapy.

Cisplatin, epirubicin, leucovorin and 5-fluorouracil (PELF) is more active than 5-fluorouracil, doxorubicin and methotrexate (FAMTX) in advanced gastric carcinoma

BACKGROUND

5-Fluorouracil (5-FU), doxorubicin and methotrexate (FAMTX) and cisplatin, epirubicin, leucovorin and 5-FU (PELF) have both been reported to be superior to the combination 5-FU, doxorubicin and mitomycin C (FAM) in advanced gastric carcinoma. On the basis of the presence and dose intensity of the included agents, we hypothesised that PELF would be superior to FAMTX.

PATIENTS AND METHODS

Two hundred patients with untreated advanced gastric carcinoma were randomised to receive PELF or FAMTX for a maximum of six cycles or until disease progression.

RESULTS

The complete response (CR) rates to PELF and FAMTX were, respectively, 13% [95% confidence intervals (CI) 6% to 20%] and 2% (95% CI 0% to 5%; P = 0.003), and the objective response rates [CR plus partial response (PR) rates] 39% (95% CI 29% to 49%) and 22% (95% CI 13% to 30%; P = 0.009), thus significantly favouring the PELF combination. The survival rates after 12 months (30.8% versus 22.4%) and 24 months (15.7% versus 9.5%) were also higher among patients receiving PELF, but these differences were not statistically significant. The toxicities were qualitatively different but quantitatively similar. Both regimens seem to be feasible provided that careful patient monitoring is assured.

CONCLUSIONS

PELF is significantly more active than FAMTX and deserves further research in the adjuvant setting.

Factors influencing hospital infection control policies in Italian hospitals

A study was undertaken to determine the resources available in Italian hospitals for the control of nosocomial infections and the factors favouring a successful approach. During January-May 2000 a questionnaire about infection control was sent to the hospital health director of all Italian National Health System hospitals treating acute patients and with more than 3500 admissions in 1999. An active programme was defined as a hospital infection control committee (HICC) meeting at least four times in 1999, the presence of a doctor with infection control responsibilities, a nurse employed in infection control and at least one surveillance activity and one infection control guideline issued or updated in the past two years. There was a response rate of 87.5% (463/529). Almost fifteen percent (69/463) of hospitals had an active programme for Infection Control and 76.2% (353/463) had a HICC. Seventy-one percent (330/463) of the hospitals had a hospital infection control physician and 53% (250/463) had infection control nurses. Fifty-two percent (242/463) reported at least one surveillance activity and 70.8% (328/463) had issued or updated at least one guidance document in the last two years. The presence of regional policies [odds ratio (OR) 8.7], operative groups (OR 4.2), at least one full-time nurse (OR 4.6) and a hospital annual plan which specified infection control (OR 2.1) were statistically associated with an active programme in the multivariate analysis.