Cutting Edge: First Lung Infection Permanently Enlarges Lymph Nodes and Enhances New T Cell Responses

Humans experience frequent respiratory infections. Immunology and vaccinology studies in mice are typically performed in naive specific pathogen-free animals responding to their very first respiratory challenge. We found that the first respiratory infection induces lifelong enlargement of the lung-draining mediastinal lymph nodes (medLNs). Furthermore, infection-experienced medLNs supported better naive T cell surveillance and effector responses to new unrelated infections that exhibited more biased accumulation and memory establishment within the lung. Moreover, we observed that weight loss induced by influenza infection was substantially reduced in mice that had recovered from a previous unrelated respiratory viral challenge. These data show that the lack of infectious history and corresponding medLN hypoplasia in specific pathogen-free mice alter their immune response to lung infections. Preclinical vaccination and immunology studies should consider the previous infectious experience of the model organism.

Depleting CD103+ resident memory T cells in vivo reveals immunostimulatory functions in oral mucosa

The oral mucosa is a frontline for microbial exposure and juxtaposes several unique tissues and mechanical structures. Based on parabiotic surgery of mice receiving systemic viral infections or co-housing with microbially diverse pet shop mice, we report that the oral mucosa harbors CD8+ CD103+ resident memory T cells (TRM), which locally survey tissues without recirculating. Oral antigen re-encounter during the effector phase of immune responses potentiated TRM establishment within tongue, gums, palate, and cheek. Upon reactivation, oral TRM triggered changes in somatosensory and innate immune gene expression. We developed in vivo methods for depleting CD103+ TRM while sparing CD103neg TRM and recirculating cells. This revealed that CD103+ TRM were responsible for inducing local gene expression changes. Oral TRM putatively protected against local viral infection. This study provides methods for generating, assessing, and in vivo depleting oral TRM, documents their distribution throughout the oral mucosa, and provides evidence that TRM confer protection and trigger responses in oral physiology and innate immunity.

Chronic antigen in solid tumors drives a distinct program of T cell residence

Analyses of healthy tissue reveal signatures that identify resident memory CD8+ T cells (TRM), which survey tissues without recirculating. The density of TRM phenotype cells within solid tumors correlates favorably with prognosis, suggesting that intratumoral residents control cancer. However, residence has not been directly tested, and intratumoral TRM phenotype cells could instead reflect aspects of the microenvironment that correlate with prognosis. Using a breast cancer model in mice, we found that conventional TRM markers do not inform the tumor residence of either bystander or tumor-specific cells, which exhibit further distinct phenotypes in the tumor microenvironment and healthy mammary tissue. Rather, tumor-specific, stem progenitor CD8+ T cells migrate to tumors and become resident while acquiring select markers of exhaustion. These data indicate that tonic antigen stimulation and the tumor environment drive distinct programs of residence compared with healthy tissues and that tumor immunity is sustained by continued migration of tumor-specific stem cells.

Novel Lymphocytic Choriomeningitis Virus Strain Sustains Abundant Exhausted Progenitor CD8 T Cells without Systemic Viremia

Lymphocytic choriomeningitis virus (LCMV) is the prototypic arenavirus and a natural mouse pathogen. LCMV-Armstrong, an acutely resolved strain, and LCMV-clone 13, a mutant that establishes chronic infection, have provided contrasting infection models that continue to inform the fundamental biology of T cell differentiation, regulation of exhaustion, and response to checkpoint blockade. In this study, we report the isolation and characterization of LCMV-Minnesota (LCMV-MN), which was naturally transmitted to laboratory mice upon cohousing with pet shop mice and shares 80-95% amino acid homology with previously characterized LCMV strains. Infection of laboratory mice with purified LCMV-MN resulted in viral persistence that was intermediate between LCMV-Armstrong and -clone 13, with widely disseminated viral replication and viremia that was controlled within 15-30 d, unless CD4 T cells were depleted prior to infection. LCMV-MN-responding CD8+ T cells biased differentiation toward the recently described programmed death-1 (PD-1)+CXCR5+Tim-3lo stemlike CD8+ T cell population (also referred to as progenitor exhausted T cells) that effectuates responses to PD-1 blockade checkpoint inhibition, a therapy that rejuvenates responses against chronic infections and cancer. This subset resembled previously characterized PD-1+TCF1+ stemlike CD8+ T cells by transcriptional, phenotypic, and functional assays, yet was atypically abundant. LCMV-MN may provide a tool to better understand the breadth of immune responses in different settings of chronic Ag stimulation as well as the ontogeny of progenitor exhausted T cells and the regulation of responsiveness to PD-1 blockade.

Comparative analysis of genome-wide DNA methylation identifies patterns that associate with conserved transcriptional programs in osteosarcoma

Osteosarcoma is an aggressive tumor of the bone that primarily affects young adults and adolescents. Osteosarcoma is characterized by genomic chaos and heterogeneity. While inactivation of tumor protein p53 (TP53) is nearly universal other high frequency mutations or structural variations have not been identified. Despite this genomic heterogeneity, key conserved transcriptional programs associated with survival have been identified across human, canine and induced murine osteosarcoma. The epigenomic landscape, including DNA methylation, plays a key role in establishing transcriptional programs in all cell types. The role of epigenetic dysregulation has been studied in a variety of cancers but has yet to be explored at scale in osteosarcoma. Here we examined genome-wide DNA methylation patterns in 24 human and 44 canine osteosarcoma samples identifying groups of highly correlated DNA methylation marks in human and canine osteosarcoma samples. We also link specific DNA methylation patterns to key transcriptional programs in both human and canine osteosarcoma. Building on previous work, we built a DNA methylation-based measure for the presence and abundance of various immune cell types in osteosarcoma. Finally, we determined that the underlying state of the tumor, and not changes in cell composition, were the main driver of differences in DNA methylation across the human and canine samples. SIGNIFICANCE: Genome wide comparison of DNA methylation patterns in osteosarcoma across two species lays the ground work for the exploration of DNA methylation programs that help establish conserved transcriptional programs in the context of varied mutational landscapes.

Development of an exosomal gene signature to detect residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning

Osteosarcoma has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, their clinical application is precluded by challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma in mouse xenografts to distinguish tumor-derived from host-response exosomal messenger RNAs (mRNAs). The model allows for the identification of canine osteosarcoma-specific gene signatures by RNA sequencing and a species-differentiating bioinformatics pipeline. An osteosarcoma-associated signature consisting of five gene transcripts (SKA2, NEU1, PAF1, PSMG2, and NOB1) was validated in dogs with spontaneous osteosarcoma by real-time quantitative reverse transcription PCR (qRT-PCR), while a machine learning model assigned dogs into healthy or disease groups. Serum/plasma exosomes were isolated from 53 dogs in distinct clinical groups ("healthy", "osteosarcoma", "other bone tumor", or "non-neoplastic disease"). Pre-treatment samples from osteosarcoma cases were used as the training set, and a validation set from post-treatment samples was used for testing, classifying as "osteosarcoma detected" or "osteosarcoma-NOT detected". Dogs in a validation set whose post-treatment samples were classified as "osteosarcoma-NOT detected" had longer remissions, up to 15 months after treatment. In conclusion, we identified a gene signature predictive of molecular remissions with potential applications in the early detection and minimal residual disease settings. These results provide proof of concept for our discovery platform and its utilization in future studies to inform cancer risk, diagnosis, prognosis, and therapeutic response.

Abstract 671: Development of an exosomal biomarker signature to detect minimal residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning

Osteosarcoma, the most common primary bone tumor in humans and dogs, has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, the wide clinical use of exosomes is precluded by the challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma xenografts to distinguish tumor-derived exosome mRNAs and host-response mRNAs, allowing for identification of osteosarcoma-specific gene signatures, which were then validated in samples from dogs with osteosarcoma. A canine osteosarcoma-associated gene signature was developed using exosomes from mouse xenograft experiments and a species-aware bioinformatics pipeline. Validation of the gene signature in canine serum exosomes was done by qRT-PCR analysis. Machine learning algorithms assigned dogs into healthy or disease groups based on the qRT-PCR data. Dogs in a validation set of clinical osteosarcoma cases with post-treatment samples were classified as “osteosarcoma -detected” or “osteosarcoma - NOT detected”, and clinical outcome measures were compared. An osteosarcoma-associated signature consisting of five mRNAs (SKA2, NEU1, PAF1, PSMG2, and NOB1) was identified using our canine osteosarcoma xenograft model. Serum exosomes were isolated from 53 dogs in distinct clinical groups, including “healthy”, “osteosarcoma”, “other bone tumor”, or “non-neoplastic disease”. Dogs in a validation set whose post-treatment samples were classified as “osteosarcoma - NOT detected” had longer remissions than dogs classified as “osteosarcoma - detected” for up to 15 months after treatment. In conclusion, we identified a gene signature associated with canine osteosarcoma for the detection of minimal residual disease. This gene signature was validated by qRT-PCR with serum exosomes from canine patients with osteosarcoma, and used to train artificial intelligence. The test results were predictive of molecular remissions in dogs up to 15 months after initiating therapy, suggesting it will have applications in the early detection and minimal residual disease settings. This study combines a bioinformatics approach to biomarker discovery with machine learning to correctly identify osteosarcoma in canine patients. These results set the stage for future discoveries to inform cancer risk, diagnosis, prognosis, and response to therapy.

Citation Format: Kelly M. Makielski, Alicia J. Donnelly, Ali Khammanivong, Milcah C. Scott, Hirotaka Tomiyasu, John Garbe, Lauren J. Mills, Gary R. Cutter, Andrea Ortiz, Dana C. Galvan, Kristi Ward, Alexa N. Montoya, Brad A. Bryan, Joelle M. Fenger, William C. Kisseberth, Subbaya Subramanian, Jaime F. Modiano. Development of an exosomal biomarker signature to detect minimal residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 671.

Decoupling electron and phonon transport in single-nanowire hybrid materials for high-performance thermoelectrics

Organic-inorganic hybrids have recently emerged as a class of high-performing thermoelectric materials that are lightweight and mechanically flexible. However, the fundamental electrical and thermal transport in these materials has remained elusive due to the heterogeneity of bulk, polycrystalline, thin films reported thus far. Here, we systematically investigate a model hybrid comprising a single core/shell nanowire of Te-PEDOT:PSS. We show that as the nanowire diameter is reduced, the electrical conductivity increases and the thermal conductivity decreases, while the Seebeck coefficient remains nearly constant-this collectively results in a figure of merit, ZT, of 0.54 at 400 K. The origin of the decoupling of charge and heat transport lies in the fact that electrical transport occurs through the organic shell, while thermal transport is driven by the inorganic core. This study establishes design principles for high-performing thermoelectrics that leverage the unique interactions occurring at the interfaces of hybrid nanowires.

Tumor-infiltrating CD8+ T cells can be resident, but exhaustion markers rather than CD69 correlate with residence and tumor specificity

Tumor infiltrating lymphocytes (TILs) represent a heterogeneous population of both pathogen-specific bystander and tumor-specific CD8+ T cells. Within select solid tumors, the expression of exhaustion markers PD-1 and CD39 has been used to discriminate between pathogen-specific and tumor-specific cells. Independent studies across numerous types of solid tumors have also shown that CD8+ TILs can exhibit distinct signatures that imply residence, however, the migrational properties of TILs have not been fully elucidated. In this study, we employed parabiosis migration assays in a mouse model of breast cancer and demonstrated that both virus-specific bystander and tumor-specific CD8+ T cells within the tumor microenvironment (TME) can be resident. Canonical markers of resident-memory T cells (TRM), including CD69, failed to discriminate between resident cells and recent migrants. However, the expression of markers associated with T cell dysfunction (PD-1, CD39, Tim-3, Lag-3) identified a population of tumor-specific cells and was tightly correlated with residence within the TME. Thus, TRM exist within tumors, durable intratumoral residence was not well informed by common markers associated with TRM in healthy tissues, and the expression of exhaustion markers correlated with both tumor specificity and durable residence.

Validating cell surface markers as accurate predictors of tissue residency

Tissue resident memory T cells (TRM) represent the dominant antigen-experienced T cell subset that mediate local immunosurveillance in non-lymphoid tissues (NLT). Most accurately defined using migration assays, including parabiosis surgery and tissue grafting, TRM remain situated within NLT without recirculating through the blood. Such migration assays are challenging and often impossible to perform given animal-use approval or experimental constraints. These limitations have necessitated the use of cell surface markers such as CD69 and CD103 as surrogates for residency in the absence of more stringent approaches. Yet reliance on these cell surface markers alone often fails to accurately predict residency in tissues. As such, we performed a systematic interrogation of the correlation between flow cytometric staining profiles and the property of durable residence as assessed using parabiosis. In multiple infection models, we found that no consistent marker combination accurately identifies and captures the abundance and heterogeneity of TRM in diverse NLT. By evaluating the usefulness of cell surface markers as diagnostic of residency on a tissue- and infection-specific basis, we identified tissue specific phenotypes that reproducibly predicted residency in three infection models. These findings are important because refined analyses of TRM populations is key to addressing deficiencies in our understanding of how TRM mediate immunosurveillance. Ongoing work will further validate these tissue-specific phenotypes in additional infection models and ‘dirty mice’ that contain CD69+ T cells within the equilibrating T cell populations.

Abstract B59: Validation of an exosomal osteosarcoma-associated gene signature in dogs with osteosarcoma

Introduction: Osteosarcoma, the most common primary bone tumor in dogs, has a guarded prognosis. A major hurdle in developing more effective therapies is the lack of osteosarcoma-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted microvesicles emerging as powerful diagnostic tools. However, wide clinical use of exosomes is precluded by the difficulty in identifying diseased cargo from the vastly larger background of normal cargo. We developed a method to distinguish tumor-derived exosome cargo from normal background, allowing for identification of an osteosarcoma-specific gene signature.

Methods: Serum exosomes were enriched from osteosarcoma xenografts and control mice. Enriched genes associated with canine osteosarcoma were identified with RNA-sequencing. From identified candidates, we defined an osteosarcoma-associated gene signature. qRT-PCR amplification validated the gene signature in serum exosomes from clinical canine cases. Machine learning algorithms classified patients into disease groups based on this gene signature.

Results: We identified an osteosarcoma-associated signature consisting of five mRNAs (SKA2, NEU1, PAF1, PSMG2, and NOB1). Serum exosomes were isolated from dogs in clinical groups, including “healthy,” “osteosarcoma,” “other bone tumor,” or “non-neoplastic disease.” Machine learning classified samples, with 82% and 86% of untrained samples predicted as osteosarcoma by CN2 and RF models, respectively. Post-treatment samples “misclassified” as non-osteosarcoma were associated with longer remissions, potentially from a lack of remaining osteosarcoma cells.

Conclusions: We identified a gene signature associated with canine osteosarcoma. This gene signature was validated by qRT-PCR with serum exosomes from patients with osteosarcoma, as well as used to train artificial intelligence to correctly classify canine patients according to disease group with up to 93.8% accuracy.

Clinical Significance: This study combines a bioinformatics approach to biomarker discovery with machine learning to correctly identify osteosarcoma in canine patients. These results set the stage for future discoveries to inform cancer risk, diagnosis, prognosis, and response to therapy.

Citation Format: Kelly M. Makielski, Alicia J. Donnelly, Milcah C. Scott, Hirotaka Tomiyasu, Ali Khammanivong, William C. Kisseberth, Jaime F. Modiano. Validation of an exosomal osteosarcoma-associated gene signature in dogs with osteosarcoma [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B59.

Developmental plasticity allows outside-in immune responses by resident memory T cells

Central memory T (TCM) cells patrol lymph nodes and perform conventional memory responses upon re-stimulation: proliferation, migration, and differentiation into diverse T cell subsets while also self-renewing. Resident memory T (TRM) cells are parked within single organs, share properties with terminal effectors, and contribute to rapid host protection. We observed that reactivated TRM cells rejoined the circulating pool. Epigenetic analyses revealed that TRM cells align closely with conventional memory T cell populations, bearing little resemblance to recently activated effectors. Fully differentiated TRM cells isolated from small intestine epithelium exhibited the potential to differentiate into TCM, TEM, and TRM cells upon recall. Ex-TRM cells, former intestinal TRM that rejoined the circulating pool, heritably maintained a predilection for homing back to their tissue of origin upon subsequent reactivation and a heightened capacity to re-differentiate into TRM cells. Thus, TRM cells can rejoin the circulation but are advantaged to re-form local TRM when called upon.

S100A4 mRNA-protein relationship uncovered by measurement noise reduction

Intrinsic biological fluctuation and/or measurement error can obscure the association of gene expression patterns between RNA and protein levels. Appropriate normalization of reverse-transcription quantitative PCR (RT-qPCR) data can reduce technical noise in transcript measurement, thus uncovering such relationships. The accuracy of gene expression measurement is often challenged in the context of cancer due to the genetic instability and "splicing weakness" involved. Here, we sequenced the poly(A) cancer transcriptome of canine osteosarcoma using mRNA-Seq. Expressed sequences were resolved at the level of two consecutive exons to enable the design of exon-border spanning RT-qPCR assays and ranked for stability based on the coefficient of variation (CV). Using the same template type for RT-qPCR validation, i.e. poly(A) RNA, avoided skewing of stability assessment by circular RNAs (circRNAs) and/or rRNA deregulation. The strength of the relationship between mRNA expression of the tumour marker S100A4 and its proportion score of quantitative immunohistochemistry (qIHC) was introduced as an experimental readout to fine-tune the normalization choice. Together with the essential logit transformation of qIHC scores, this approach reduced the noise of measurement as demonstrated by uncovering a highly significant, strong association between mRNA and protein expressions of S100A4 (Spearman's coefficient ρ = 0.72 (p = 0.006)). KEY MESSAGES: • RNA-seq identifies stable pairs of consecutive exons in a heterogeneous tumour. • Poly(A) RNA templates for RT-qPCR avoid bias from circRNA and rRNA deregulation. • HNRNPL is stably expressed across various cancer tissues and osteosarcoma. • Logit transformed qIHC score better associates with mRNA amount. • Quantification of minor S100A4 mRNA species requires poly(A) RNA templates and dPCR.

Pet shop mice are infected with a novel lymphocytic choriomeningitis virus strain that sustains an abundance of stem-like PD-1+ CD8 T cells

Lymphocytic choriomeningitis virus (LCMV) is a natural mouse pathogen. LCMV Armstrong, an acutely resolved strain, and LCMV Clone13, a mutant that establishes chronic infection, have provided contrasting infection models that continue to inform the fundamental biology of T cell differentiation, regulation of exhaustion, and response to checkpoint blockade. Here, we describe LCMV Minnesota (LCMV-MN), which was transmitted to laboratory mice upon cohousing with pet shop mice and shares 80–95% amino acid homology with previously characterized LCMV strains. Infection of laboratory mice with purified LCMV-MN resulted in widely disseminated viral replication and viremia that was controlled within 15–30 days; which is of intermediate duration between LCMV Armstrong and Clone13. The magnitude of the LCMV-MN specific CD8+ T cell was maintained at much higher levels than that observed after LCMV Armstrong or Clone13 infections. LCMV-MN responding CD8+ T cells were further associated with significantly biased differentiation towards the recently described PD1+ CXCR5+ Tim-3lo stem-like CD8+ T cell population that was previously shown to be largely responsible for responsiveness to PD-1 inhibitory checkpoint blockade. In contrast to LCMV Clone13-induced responses, this subset persisted after resolution of LCMV-MN viremia, yet transcriptionally, phenotypically and functionally resembled PD1+ TCF1+ stem-like CD8+ T cells maintained by LCMV Clone13 infection. Together with existing models, LCMV-MN may contribute to a better understanding of the breadth of immune response in different chronic infections or tumor settings as well as the regulation of responsiveness to PD-1 blockade.

Developmental plasticity allows outside-in immune responses by resident memory T cells

Central memory T (TCM) cells patrol lymph nodes and perform conventional memory responses on restimulation: proliferation, migration and differentiation into diverse T cell subsets while also self-renewing. Resident memory T (TRM) cells are parked within single organs, share properties with terminal effectors and contribute to rapid host protection. We observed that reactivated TRM cells rejoined the circulating pool. Epigenetic analyses revealed that TRM cells align closely with conventional memory T cell populations, bearing little resemblance to recently activated effectors. Fully differentiated TRM cells isolated from small intestine epithelium exhibited the potential to differentiate into TCM cells, effector memory T cells and TRM cells on recall. Ex-TRM cells, former intestinal TRM cells that rejoined the circulating pool, heritably maintained a predilection for homing back to their tissue of origin on subsequent reactivation and a heightened capacity to redifferentiate into TRM cells. Thus, TRM cells can rejoin the circulation but are advantaged to re-form local TRM when called on.

Comparative Genomics Reveals Shared Mutational Landscape in Canine Hemangiosarcoma and Human Angiosarcoma

Angiosarcoma is a highly aggressive cancer of blood vessel-forming cells with few effective treatment options and high patient mortality. It is both rare and heterogenous, making large, well-powered genomic studies nearly impossible. Dogs commonly suffer from a similar cancer, called hemangiosarcoma, with breeds like the golden retriever carrying heritable genetic factors that put them at high risk. If the clinical similarity of canine hemangiosarcoma and human angiosarcoma reflects shared genomic etiology, dogs could be a critically needed model for advancing angiosarcoma research. We assessed the genomic landscape of canine hemangiosarcoma via whole-exome sequencing (47 golden retriever hemangiosarcomas) and RNA sequencing (74 hemangiosarcomas from multiple breeds). Somatic coding mutations occurred most frequently in the tumor suppressor TP53 (59.6% of cases) as well as two genes in the PI3K pathway: the oncogene PIK3CA (29.8%) and its regulatory subunit PIK3R1 (8.5%). The predominant mutational signature was the age-associated deamination of cytosine to thymine. As reported in human angiosarcoma, CDKN2A/B was recurrently deleted and VEGFA, KDR, and KIT recurrently gained. We compared the canine data to human data recently released by The Angiosarcoma Project, and found many of the same genes and pathways significantly enriched for somatic mutations, particularly in breast and visceral angiosarcomas. Canine hemangiosarcoma closely models the genomic landscape of human angiosarcoma of the breast and viscera, and is a powerful tool for investigating the pathogenesis of this devastating disease. IMPLICATIONS: We characterize the genomic landscape of canine hemangiosarcoma and demonstrate its similarity to human angiosarcoma.

CD4+ resident memory T cells dominate immunosurveillance and orchestrate local recall responses

This study examines the extent to which memory CD4+ T cells share immunosurveillance strategies with CD8+ resident memory T cells (TRM). After acute viral infection, memory CD4+ T cells predominantly used residence to survey nonlymphoid tissues, albeit not as stringently as observed for CD8+ T cells. In contrast, memory CD4+ T cells were more likely to be resident within lymphoid organs than CD8+ T cells. Migration properties of memory-phenotype CD4+ T cells in non-SPF parabionts were similar, generalizing these results to diverse infections and conditions. CD4+ and CD8+ TRM shared overlapping transcriptional signatures and location-specific features, such as granzyme B expression in the small intestine, revealing tissue-specific and migration property-specific, in addition to lineage-specific, differentiation programs. Functionally, mucosal CD4+ TRM reactivation locally triggered both chemokine expression and broad immune cell activation. Thus, residence provides a dominant mechanism for regionalizing CD4+ T cell immunity, and location enforces shared transcriptional, phenotypic, and functional properties with CD8+ T cells.

CD4+ resident memory T cells dominate immunosurveillance and orchestrate local recall responses

Migratory dynamics of T cells influence outcomes of infections and cancer. This study addresses how CD4+ T cell immunosurveillance strategies compare to CD8+ T cells by analyzing migration, transcriptome, phenotype, and function. After acute viral infection, memory CD4+ T cells predominantly utilized residence to survey nonlymphoid tissues, albeit not as stringently as observed for CD8+ T cells. In contrast, memory CD4+ T cells were more likely to be resident within lymphoid organs than CD8+ T cells. Migration properties of memory-phenotype CD4+ T cells in non-SPF parabionts were similar, generalizing these results to diverse infections and conditions. CD4+ and CD8+ resident memory T cells (TRM) shared overlapping transcriptional signatures and location-specific features, such as granzyme B expression in the small intestine, revealing tissue-specific and migration property-specific, in addition to lineage-specific, differentiation programs. Functionally, mucosal CD4+ TRM reactivation locally triggered both chemokine expression and broad immune cell activation. Thus, residence provides a dominant mechanism for regionalizing CD4+ T cell immunity, and location enforces shared transcriptional, phenotypic, and functional properties with CD8+ T cells.

The purinergic receptor P2RX7 directs metabolic fitness of long-lived memory CD8+ T cells

Extracellular ATP (eATP) is an ancient 'danger signal' used by eukaryotes to detect cellular damage¹. In mice and humans, the release of eATP during inflammation or injury stimulates both innate immune activation and chronic pain through the purinergic receptor P2RX7^2-4. It is unclear, however, whether this pathway influences the generation of immunological memory, a hallmark of the adaptive immune system that constitutes the basis of vaccines and protective immunity against re-infection^5,6. Here we show that P2RX7 is required for the establishment, maintenance and functionality of long-lived central and tissue-resident memory CD8⁺ T cell populations in mice. By contrast, P2RX7 is not required for the generation of short-lived effector CD8⁺ T cells. Mechanistically, P2RX7 promotes mitochondrial homeostasis and metabolic function in differentiating memory CD8⁺ T cells, at least in part by inducing AMP-activated protein kinase. Pharmacological inhibitors of P2RX7 provoked dysregulated metabolism and differentiation of activated mouse and human CD8⁺ T cells in vitro, and transient P2RX7 blockade in vivo ameliorated neuropathic pain but also compromised production of CD8⁺ memory T cells. These findings show that activation of P2RX7 by eATP provides a common currency that both alerts the nervous and immune system to tissue damage, and promotes the metabolic fitness and survival of the most durable and functionally relevant memory CD8⁺ T cell populations.

Abstract 2264: RNA sequencing based analysis of transposon-induced tumors reveals novel insights into cancer pathogenesis and progression

Current challenges in oncology include the discovery of drivers suitable for targeting using small molecules or antibodies and predictive animal models. We're addressing these challenges in several ways. We have developed mouse models using the Sleeping Beauty (SB) transposon system to perform unbiased, forward genetic screens to define strong candidate cancer genes. Further, our studies and others have utilized transposon mutagenesis to derive cancers from all three germ layers including carcinomas, sarcomas, neuroectodermal tumors, and hematopoietic malignancies. We hypothesize that data from these screens will help to identify genetic drivers of human cancer that are altered at the gene copy number or epigenetic levels. Our T2/Onc SB transposons create fusions with endogenous gene transcripts and RNA sequencing (RNA-seq) reveals the genes targeted in the tumor. From these results, correlations can be drawn between the alteration of specific genes and changes in tumor gene expression patterns. Thus, the goals of our recent research have been to discover novel associations between SB-induced tumor phenotypes and specific driver gene alterations (i.e. the tumor genotype). Moreover, RNA-seq has also revealed tumor molecular subtypes, in many cases with correlating transposon insertion mutations. Several examples will be described: mammary tumors, osteosarcoma (OS), medulloblastoma and central nervous system primitive neuro-ectodermal tumors. In each case, RNA-seq has revealed novel genotype-phenotype correlations including drivers of high cell cycle activity, metastasis, white blood cell exclusion from the tumor, SHH pathway activation, and hormone receptor signaling. These models provide a source of genetically heterogenous tumors with the same initiating mutation useful for identifying cooperating pathways and drivers of specific tumor phenotypes. Secondly, we are using SB transposon mutagenesis to understand the genetic basis of chemotherapy resistance in cancer including OS. In our OS model, SB mutagenesis is an ongoing process due to the constitutive expression of SB transposase, which permits the continued mobilization of transposons. We hypothesize that in vivo treatment with chemotherapy agents will allow tumor cells that contain transposon mutations in chemoresistance genes to persist. Preliminary studies with primary tumor cells derived from SB-enhanced OS tumors demonstrate resistance to combination chemotherapy treatment in vivo. Further analysis to identify candidate chemotherapy resistance genes are currently underway.

Citation Format: Emily T. Camilleri, Pauli J. Beckmann, Jon D. Larson, Morito Kurata, Jingmin Shu, Emily Pope, Wendy A. Hudson, Nuri A. Temiz, Susan K. Rathe, Rebecca S. LaRue, Anne E. Sarver, Milcah C. Scott, Jyotika Varshney, Jaime F. Modiano, Branden S. Moriarity, Aaron L. Sarver, Somasekar Seshagiri, David A. Largaespada. RNA sequencing based analysis of transposon-induced tumors reveals novel insights into cancer pathogenesis and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2264.

Comparative Transcriptome Analysis Quantifies Immune Cell Transcript Levels, Metastatic Progression, and Survival in Osteosarcoma

Overall survival of patients with osteosarcoma (OS) has improved little in the past three decades, and better models for study are needed. OS is common in large dog breeds and is genetically inducible in mice, making the disease ideal for comparative genomic analyses across species. Understanding the level of conservation of intertumor transcriptional variation across species and how it is associated with progression to metastasis will enable us to more efficiently develop effective strategies to manage OS and to improve therapy. In this study, transcriptional profiles of OS tumors and cell lines derived from humans (n = 49), mice (n = 103), and dogs (n = 34) were generated using RNA sequencing. Conserved intertumor transcriptional variation was present in tumor sets from all three species and comprised gene clusters associated with cell cycle and mitosis and with the presence or absence of immune cells. Further, we developed a novel gene cluster expression summary score (GCESS) to quantify intertumor transcriptional variation and demonstrated that these GCESS values associated with patient outcome. Human OS tumors with GCESS values suggesting decreased immune cell presence were associated with metastasis and poor survival. We validated these results in an independent human OS tumor cohort and in 15 different tumor data sets obtained from The Cancer Genome Atlas. Our results suggest that quantification of immune cell absence and tumor cell proliferation may better inform therapeutic decisions and improve overall survival for OS patients.Significance: This study offers new tools to quantify tumor heterogeneity in osteosarcoma, identifying potentially useful prognostic biomarkers for metastatic progression and survival in patients. Cancer Res; 78(2); 326-37. ©2017 AACR.

Atomically Altered Hematite for Highly Efficient Perovskite Tandem Water-Splitting Devices

Photoelectrochemical (PEC) cells are attractive for storing solar energy in chemical bonds through cleaving of water into oxygen and hydrogen. Although hematite (α-Fe₂ O₃ ) is a promising photoanode material owing to its chemical stability, suitable band gap, low cost, and environmental friendliness, its performance is limited by short carrier lifetimes, poor conductivity, and sluggish kinetics leading to low (solar-to-hydrogen) STH efficiency. Herein, we combine solution-based hydrothermal growth and a post-growth surface exposure through atomic layer deposition (ALD) to show a dramatic enhancement of the efficiency for water photolysis. These modified photoanodes show a high photocurrent of 3.12 mA cm^-2 at 1.23 V versus RHE, (>5 times higher than Fe₂ O₃ ) and a plateau photocurrent of 4.5 mA cm^-2 at 1.5 V versus RHE. We demonstrate that these photoanodes in tandem with a CH₃ NH₃ PbI₃ perovskite solar cell achieves overall unassisted water splitting with an STH conversion efficiency of 3.4 %, constituting a new benchmark for hematite-based tandem systems.