Nathan Reticker-Flynn, PhD

All Publications

• Lymph nodes: at the intersection of cancer treatment and progression. Trends in cell biology Reticker-Flynn, N. E., Engleman, E. G. 2023

  Abstract

  Metastasis to lymph nodes (LNs) is a common feature of disease progression in most solid organ malignancies. Consequently, LN biopsy and lymphadenectomy are common clinical practices, not only because of their diagnostic utility but also as a means of deterring further metastatic spread. LN metastases have the potential to seed additional tissues and can induce metastatic tolerance, a process by which tumor-specific immune tolerance in LNs promotes further disease progression. Nonetheless, phylogenetic studies have revealed that distant metastases are not necessarily derived from nodal metastases. Furthermore, immunotherapy efficacy is increasingly being attributed to initiation of systemic immune responses within LNs. We argue that lymphadenectomy and nodal irradiation should be approached with caution, particularly in patients receiving immunotherapy.

  View details for DOI 10.1016/j.tcb.2023.04.001

  View details for PubMedID 37149414

• Lymph node colonization induces tumor-immune tolerance to promote distant metastasis. Cell Reticker-Flynn, N. E., Zhang, W., Belk, J. A., Basto, P. A., Escalante, N. K., Pilarowski, G. O., Bejnood, A., Martins, M. M., Kenkel, J. A., Linde, I. L., Bagchi, S., Yuan, R., Chang, S., Spitzer, M. H., Carmi, Y., Cheng, J., Tolentino, L. L., Choi, O., Wu, N., Kong, C. S., Gentles, A. J., Sunwoo, J. B., Satpathy, A. T., Plevritis, S. K., Engleman, E. G. 2022

  Abstract

  For many solid malignancies, lymph node (LN) involvement represents a harbinger of distant metastatic disease and, therefore, an important prognostic factor. Beyond its utility as a biomarker, whether and how LN metastasis plays an active role in shaping distant metastasis remains an open question. Here, we develop a syngeneic melanoma mouse model of LN metastasis to investigate how tumors spread to LNs and whether LN colonization influences metastasis to distant tissues. We show that an epigenetically instilled tumor-intrinsic interferon response program confers enhanced LN metastatic potential by enabling the evasion of NK cells and promoting LN colonization. LN metastases resist T cell-mediated cytotoxicity, induce antigen-specific regulatory T cells, and generate tumor-specific immune tolerance that subsequently facilitates distant tumor colonization. These effects extend to human cancers and other murine cancer models, implicating a conserved systemic mechanism by which malignancies spread to distant organs.

  View details for DOI 10.1016/j.cell.2022.04.019

  View details for PubMedID 35525247

• Cancer systems immunology. eLife Reticker-Flynn, N. E., Engleman, E. G. 2020; 9

  Abstract

  Tumor immunology is undergoing a renaissance due to the recent profound clinical successes of tumor immunotherapy. These advances have coincided with an exponential growth in the development of -omics technologies. Armed with these technologies and their associated computational and modeling toolsets, systems biologists have turned their attention to tumor immunology in an effort to understand the precise nature and consequences of interactions between tumors and the immune system. Such interactions are inherently multivariate, spanning multiple time and size scales, cell types, and organ systems, rendering systems biology approaches particularly amenable to their interrogation. While in its infancy, the field of 'Cancer Systems Immunology' has already influenced our understanding of tumor immunology and immunotherapy. As the field matures, studies will move beyond descriptive characterizations toward functional investigations of the emergent behavior that govern tumor-immune responses. Thus, Cancer Systems Immunology holds incredible promise to advance our ability to fight this disease.

  View details for DOI 10.7554/eLife.53839

  View details for PubMedID 32657757

• Systemic Immunity Is Required for Effective Cancer Immunotherapy. Cell Spitzer, M. H., Carmi, Y., Reticker-Flynn, N. E., Kwek, S. S., Madhireddy, D., Martins, M. M., Gherardini, P. F., Prestwood, T. R., Chabon, J., Bendall, S. C., Fong, L., Nolan, G. P., Engleman, E. G. 2017; 168 (3): 487-502 e15

  Abstract

  Immune responses involve coordination across cell types and tissues. However, studies in cancer immunotherapy have focused heavily on local immune responses in the tumor microenvironment. To investigate immune activity more broadly, we performed an organism-wide study in genetically engineered cancer models using mass cytometry. We analyzed immune responses in several tissues after immunotherapy by developing intuitive models for visualizing single-cell data with statistical inference. Immune activation was evident in the tumor and systemically shortly after effective therapy was administered. However, during tumor rejection, only peripheral immune cells sustained their proliferation. This systemic response was coordinated across tissues and required for tumor eradication in several immunotherapy models. An emergent population of peripheral CD4 T cells conferred protection against new tumors and was significantly expanded in patients responding to immunotherapy. These studies demonstrate the critical impact of systemic immune responses that drive tumor rejection.

  View details for DOI 10.1016/j.cell.2016.12.022

  View details for PubMedID 28111070

• Aberrant Glycosylation Promotes Lung Cancer Metastasis through Adhesion to Galectins in the Metastatic Niche CANCER DISCOVERY Reticker-Flynn, N. E., Bhatia, S. N. 2015; 5 (2): 168-181

  Abstract

  Metastasis is the leading cause of cancer-associated deaths. Although dissemination of tumor cells likely occurs early in tumorigenesis, the constituents of the microenvironment play essential rate-limiting roles in determining whether these cells will form clinically relevant tumors. Recent studies have uncovered many molecular factors that contribute to the establishment of a protumorigenic metastatic niche. Here, we demonstrate that galectin-3, whose expression has clinical associations with advanced malignancy and poor outcome, contributes to metastatic niche formation by binding to carbohydrates on metastatic cells. We show that galectin-3 is expressed early during tumorigenesis by both CD11b(+)Gr-1(+) and CD11b(+)Ly-6C(hi) leukocytes. Tumors mobilize these myeloid populations through secretion of soluble factors, including IL6. We find that metastatic cancer cells exhibit elevated presentation of the oncofetal galectin-3 carbohydrate ligand, the Thomsen-Friedenreich antigen, on their surfaces as a result of altered C2GnT2 and St6GalNAc4 glycosyltransferase activity that inhibits further glycosylation of this carbohydrate motif and promotes metastasis.Although clinical observations of elevated serum galectin-3 levels and altered glycosylation have been associated with malignancy, we identify novel roles for glycosyltransferases in promoting adhesion to galectins in the metastatic niche. This identification of a cytokine-leukocyte-glycosylation axis in metastasis provides mechanistic explanations for clinical associations between malignancy and aberrant glycosylation.

  View details for DOI 10.1158/2159-8290.CD-13-0760

  View details for Web of Science ID 000349393600025

  View details for PubMedID 25421439

  View details for PubMedCentralID PMC4367955

• A combinatorial extracellular matrix platform identifies cell-extracellular matrix interactions that correlate with metastasis NATURE COMMUNICATIONS Reticker-Flynn, N. E., Malta, D. F., Winslow, M. M., Lamar, J. M., Xu, M. J., Underhill, G. H., Hynes, R. O., Jacks, T. E., Bhatia, S. N. 2012; 3

  Abstract

  Extracellular matrix interactions have essential roles in normal physiology and many pathological processes. Although the importance of extracellular matrix interactions in metastasis is well documented, systematic approaches to identify their roles in distinct stages of tumorigenesis have not been described. Here we report a novel-screening platform capable of measuring phenotypic responses to combinations of extracellular matrix molecules. Using a genetic mouse model of lung adenocarcinoma, we measure the extracellular matrix-dependent adhesion of tumour-derived cells. Hierarchical clustering of the adhesion profiles differentiates metastatic cell lines from primary tumour lines. Furthermore, we uncovered that metastatic cells selectively associate with fibronectin when in combination with galectin-3, galectin-8 or laminin. We show that these molecules correlate with human disease and that their interactions are mediated in part by α3β1 integrin. Thus, our platform allowed us to interrogate interactions between metastatic cells and their microenvironments, and identified extracellular matrix and integrin interactions that could serve as therapeutic targets.

  View details for DOI 10.1038/ncomms2128

  View details for Web of Science ID 000313514100032

  View details for PubMedID 23047680

• Interrogating the roles of lymph node metastasis in systemic immune surveillance. Clinical & experimental metastasis Basto, P. A., Reticker-Flynn, N. E. 2024

  Abstract

  Lymph nodes (LNs) are principal orchestrators of the adaptive immune response, yet in the context of malignancy, they are typically the first sites of metastasis. When tumors spread to LNs, they alter the immune repertoire, ultimately reconditioning it in a manner that suppresses anti-tumor immunity and promotes further metastatic dissemination. Conversely, activation of anti-tumor immunity within LNs is essential for immunotherapy, suggesting clinical approaches to radiotherapy in LNs and lymphadenectomy may need to be reconsidered in the context of immune checkpoint blockade (ICB). Herein, we discuss our understanding of the immune remodeling that coincides with LN metastasis as well as recent clinical studies exploring neoadjuvant immunotherapy and the roles of LNs in treatment of solid organ malignancies.

  View details for DOI 10.1007/s10585-023-10261-3

  View details for PubMedID 38315348

  View details for PubMedCentralID 5998822

• Neutrophil-activating therapy for the treatment of cancer. Cancer cell Linde, I. L., Prestwood, T. R., Qiu, J., Pilarowski, G., Linde, M. H., Zhang, X., Shen, L., Reticker-Flynn, N. E., Chiu, D. K., Sheu, L. Y., Van Deursen, S., Tolentino, L. L., Song, W., Engleman, E. G. 2023

  Abstract

  Despite their cytotoxic capacity, neutrophils are often co-opted by cancers to promote immunosuppression, tumor growth, and metastasis. Consequently, these cells have received little attention as potential cancer immunotherapeutic agents. Here, we demonstrate in mouse models that neutrophils can be harnessed to induce eradication of tumors and reduce metastatic seeding through the combined actions of tumor necrosis factor, CD40 agonist, and tumor-binding antibody. The same combination activates human neutrophils invitro, enabling their lysis of human tumor cells. Mechanistically, this therapy induces rapid mobilization and tumor infiltration of neutrophils along with complement activation in tumors. Complement component C5a activates neutrophils to produce leukotriene B4, which stimulates reactive oxygen species production via xanthine oxidase, resulting in oxidative damage and Tcell-independent clearance of multiple tumor types. These data establish neutrophils as potent anti-tumor immune mediators and define an inflammatory pathway that can be harnessed to drive neutrophil-mediated eradication of cancer.

  View details for DOI 10.1016/j.ccell.2023.01.002

  View details for PubMedID 36706760

• Transient cell-in-cell formation underlies tumor relapse and resistance to immunotherapy. eLife Gutwillig, A., Santana-Magal, N., Farhat-Younis, L., Rasoulouniriana, D., Madi, A., Luxenburg, C., Cohen, J., Padmanabhan, K., Shomron, N., Shapira, G., Gleiberman, A., Parikh, R., Levy, C., Feinmesser, M., Hershkovitz, D., Zemser-Werner, V., Zlotnik, O., Kroon, S., Hardt, W., Debets, R., Reticker-Flynn, N. E., Rider, P., Carmi, Y. 2022; 11

  Abstract

  Despite the remarkable successes of cancer immunotherapies, the majority of patients will experience only partial response followed by relapse of resistant tumors. While treatment resistance has frequently been attributed to clonal selection and immunoediting, comparisons of paired primary and relapsed tumors in melanoma and breast cancers indicate that they share the majority of clones. Here, we demonstrate in both mouse models and clinical human samples that tumor cells evade immunotherapy by generating unique transient cell-in-cell structures, which are resistant to killing by T cells and chemotherapies. While the outer cells in this cell-in-cell formation are often killed by reactive T cells, the inner cells remain intact and disseminate into single tumor cells once T cells are no longer present. This formation is mediated predominantly by IFNgamma-activated T cells, which subsequently induce phosphorylation of the transcription factors signal transducer and activator of transcription 3 (STAT3) and early growth response-1 (EGR-1) in tumor cells. Indeed, inhibiting these factors prior to immunotherapy significantly improves its therapeutic efficacy. Overall, this work highlights a currently insurmountable limitation of immunotherapy and reveals a previously unknown resistance mechanism which enables tumor cells to survive immune-mediated killing without altering their immunogenicity.

  View details for DOI 10.7554/eLife.80315

  View details for PubMedID 36124553

• Identification of cell types in multiplexed in situ images by combining protein expression and spatial information using CELESTA. Nature methods Zhang, W., Li, I., Reticker-Flynn, N. E., Good, Z., Chang, S., Samusik, N., Saumyaa, S., Li, Y., Zhou, X., Liang, R., Kong, C. S., Le, Q., Gentles, A. J., Sunwoo, J. B., Nolan, G. P., Engleman, E. G., Plevritis, S. K. 2022

  Abstract

  Advances in multiplexed in situ imaging are revealing important insights in spatial biology. However, cell type identification remains a major challenge in imaging analysis, with most existing methods involving substantial manual assessment and subjective decisions for thousands of cells. We developed an unsupervised machine learning algorithm, CELESTA, which identifies the cell type of each cell, individually, using the cell's marker expression profile and, when needed, its spatial information. We demonstrate the performance of CELESTA on multiplexed immunofluorescence images of colorectal cancer and head and neck squamous cell carcinoma (HNSCC). Using the cell types identified by CELESTA, we identify tissue architecture associated with lymph node metastasis in HNSCC, and validate our findings in an independent cohort. By coupling our spatial analysis with single-cell RNA-sequencing data on proximal sections of the same specimens, we identify cell-cell crosstalk associated with lymph node metastasis, demonstrating the power of CELESTA to facilitate identification of clinically relevant interactions.

  View details for DOI 10.1038/s41592-022-01498-z

  View details for PubMedID 35654951

• Skip metastasis in mediastinal lymph node is a favorable prognostic factor in N2 lung cancer patients: a meta-analysis ANNALS OF TRANSLATIONAL MEDICINE Wang, Z., Cheng, J., Huang, W., Cheng, D., Liu, Y., Pu, Q., Reticker-Flynn, N. E., Liu, L. 2021; 9 (3): 218

  Abstract

  Skip metastasis is a common lymph node metastatic pattern in non-small cell lung cancer (NSCLC). The relationship between skip metastasis and specific clinicopathologic factors and the prognostic value of skip metastasis are controversial.A systematic search and analysis of skip metastasis in NSCLC was conducted in the databases of PubMed, EMBASE, and Web of Science up to Dec 2019. Summarized hazard ratio (HR), mean difference (MD), and odds ratio (OR) with associated 95% confidence intervals (CI) were evaluated to investigating the relationship between skip metastasis and overall survival (OS), disease-free survival (DFS), recurrence-free survival (RFS) and clinicopathological features in NSCLC.29 studies with a total of 1,806 skip and 4,670 non-skip N2 patients were included. The upper lobe tumor showed a higher rate of skip metastasis compared with lower lobe one (RR =1.16, 95% CI: 1.00-1.34, P=0.044, I2=39.8%). The presence of skip metastasis correlated with superior overall survival (HR =0.74, 95% CI: 0.66-0.83, P<0.001, I2=48.2%) and DFS or RFS (HR =0.71, 95% CI: 0.61-0.84, P<0.001, I2=18.2%). Further subgroup analyses indicated similar results in articles that reported intrapulmonary lymph node dissection (HR =0.67, 95% CI: 0.57-0.77, P<0.001, I2=0).The results indicate that the presence of skip metastasis is associated with a marked increase in survival of NSCLC patients compared to patients with non-skip N2 metastasis. These results suggest that skip metastasis might be a distinct subgroup for purposes of N staging of NSCLC patients, and intrapulmonary lymph node assessment is needed.

  View details for DOI 10.21037/atm-20-3513

  View details for Web of Science ID 000618856600006

  View details for PubMedID 33708845

  View details for PubMedCentralID PMC7940896

• Lymph node colonization promotes distant tumor metastasis through the induction of tumor-specific immunosuppression Reticker-Flynn, N. E., Basto, P. A., Zhang, W., Martins, M. M., Chang, S., Gentles, A. J., Sunwoo, J. B., Plevritis, S. K., Engleman, E. G. AMER ASSOC CANCER RESEARCH. 2020

  View details for DOI 10.1158/1538-7445.AM2020-3419

  View details for Web of Science ID 000590059301099

• Lymph node colonization promotes distant tumor metastasis through the induction of tumor-specific immunosuppression. Reticker-Flynn, N. E., Basto, P. A., Zhang, W., Bejnood, A., Kenkel, J. A., Martins, M. M., Chang, S., Gentles, A. J., Sunwoo, J. B., Plevritis, S. K., Engleman, E. G. AMER ASSOC CANCER RESEARCH. 2020: 25–26

  View details for Web of Science ID 000537844900026

• Melanoma-secreted lysosomes trigger monocyte-derived dendritic cell apoptosis and limit cancer immunotherapy. Cancer research Santana-Magal, N. n., Farhat-Younis, L. n., Gutwillig, A. n., Gleiberman, A. n., Rasoulouniriana, D. n., Tal, L. n., Netanely, D. n., Shamir, R. n., Blau, R. n., Feinmesser, M. n., Zlotnik, O. n., Gutman, H. n., Linde, I. L., Reticker-Flynn, N. E., Rider, P. n., Carmi, Y. n. 2020

  Abstract

  The recent success of checkpoint blockade therapies has established immunotherapy as one of the most promising treatments for melanoma. Nonetheless, a complete curative response following immunotherapy is observed only in a fraction of patients. To identify what factors limit the efficacy of immunotherapies, we established mouse models that cease to respond to immunotherapies once their tumors exceed a certain stage. Analysis of the immune systems of the organisms revealed that the numbers of tumor-infiltrating dendritic cells (TIDC) drastically decreased with time. Further, in contrast to the current paradigm, once melanoma was established, TIDC did not migrate into sentinel lymph nodes. Instead, they underwent local cell death due to excessive phagocytosis of lysosomes. Importantly, TIDC were required to license the cytotoxic activity of tumor CD8+ T cells, and in their absence, T cells did not lyse melanoma cells. Our results offer a paradigm shift regarding the role of TIDC and a framework to increase the efficacy of immunotherapies.

  View details for DOI 10.1158/0008-5472.CAN-19-2944

  View details for PubMedID 32127354

• A distinct subset of FcgammaRI-expressing Th1 cells exert antibody-mediated cytotoxic activity. The Journal of clinical investigation Rasoulouniriana, D., Santana-Magal, N., Gutwillig, A., Farhat-Younis, L., Wine, Y., Saperia, C., Tal, L., Gutman, H., Tsivian, A., Brenner, R., Bandora, E. A., Reticker-Flynn, N. E., Rider, P., Carmi, Y. 2019

  Abstract

  While a high frequency of Th1 cells in tumors is associated with improved cancer prognosis, this benefit has been attributed mainly to support of cytotoxic activity of CD8+ T cells. By attempting to potentiate antibody-driven immunity, we found a remarkable synergy between CD4+ T cells and tumor-binding antibodies. This surprising synergy was mediated by a small subset of tumor-infiltrating CD4+ T cells that express the high-affinity Fcgamma receptor for IgG (FcgammaRI) in both mouse and human patients. These cells efficiently lyse tumor cells coated with antibodies through concomitant crosslinking of their T cell receptor (TCR) and FcgammaRI. By expressing FcgammaRI and its signaling chain in conventional CD4+ T cells, we successfully employed this mechanism to treat established solid cancers. Overall, this discovery sheds new light on the biology of this T cell subset, their function during tumor immunity, and the means to utilize their unique killing signals in immunotherapy.

  View details for DOI 10.1172/JCI127590

  View details for PubMedID 31449054

• Lymph node colonization promotes distant tumor metastasis through the induction of systemic immune tolerance Reticker-Flynn, N. E., Martins, M. M., Basto, P. A., Zhang, W., Bejnood, A., Gentles, A. J., Sunwoo, J. B., Plevritis, S. K., Engleman, E. G. AMER ASSOC CANCER RESEARCH. 2019

  View details for DOI 10.1158/1538-7445.AM2019-2703

  View details for Web of Science ID 000488279401153

• A gut punch fights cancer and infection NATURE Reticker-Flynn, N. E., Engleman, E. G. 2019; 565 (7741): 573–74

  View details for Web of Science ID 000457404000031

  View details for PubMedID 30683936

• An Immunosuppressive Dendritic Cell Subset Accumulates at Secondary Sites and Promotes Metastasis in Pancreatic Cancer. Cancer research Kenkel, J. A., Tseng, W. W., Davidson, M. G., Tolentino, L. L., Choi, O., Bhattacharya, N., Seeley, E. S., Winer, D. A., Reticker-Flynn, N. E., Engleman, E. G. 2017; 77 (15): 4158-4170

  Abstract

  Pancreatic ductal adenocarcinoma (PDAC) after complete surgical resection is often followed by distant metastatic relapse for reasons that remain unclear. In this study, we investigated how the immune response at secondary sites affects tumor spread in murine models of metastatic PDAC. Early metastases were associated with dense networks of CD11b+CD11c+MHC-II+CD24+CD64lowF4/80lowdendritic cells (DC), which developed from monocytes in response to tumor-released GM-CSF. These cells uniquely expressed MGL2 and PD-L2 in the metastatic microenvironment and preferentially induced the expansion of T regulatory cells (Treg)in vitroandin vivoTargeted depletion of this DC population inMgl2DTRhosts activated cytotoxic lymphocytes, reduced Tregs, and inhibited metastasis development. Moreover, blocking PD-L2 selectively activated CD8 T cells at secondary sites and suppressed metastasis, suggesting that the DCs use this particular pathway to inhibit CD8 T-cell-mediated tumor immunity. Phenotypically similar DCs accumulated at primary and secondary sites in other models and in human PDAC. These studies suggest that a discrete DC subset both expands Tregs and suppresses CD8 T cells to establish an immunosuppressive microenvironment conducive to metastasis formation. Therapeutic strategies to block the accumulation and immunosuppressive activity of such cells may help prevent PDAC progression and metastatic relapse after surgical resection.Cancer Res; 77(15); 4158-70. ©2017 AACR.

  View details for DOI 10.1158/0008-5472.CAN-16-2212

  View details for PubMedID 28611041

  View details for PubMedCentralID PMC5550516

• Akt and SHP-1 are DC-intrinsic checkpoints for tumor immunity. JCI insight Carmi, Y., Prestwood, T. R., Spitzer, M. H., Linde, I. L., Chabon, J., Reticker-Flynn, N. E., Bhattacharya, N., Zhang, H., Zhang, X., Basto, P. A., Burt, B. M., Alonso, M. N., Engleman, E. G. 2016; 1 (18)

  Abstract

  BM-derived DC (BMDC) are powerful antigen-presenting cells. When loaded with immune complexes (IC), consisting of tumor antigens bound to antitumor antibody, BMDC induce powerful antitumor immunity in mice. However, attempts to employ this strategy clinically with either tumor-associated DC (TADC) or monocyte-derived DC (MoDC) have been disappointing. To investigate the basis for this phenomenon, we compared the response of BMDC, TADC, and MoDC to tumor IgG-IC. Our findings revealed, in both mice and humans, that upon exposure to IgG-IC, BMDC internalized the IC, increased costimulatory molecule expression, and stimulated autologous T cells. In contrast, TADC and, surprisingly, MoDC remained inert upon contact with IC due to dysfunctional signaling following engagement of Fcγ receptors. Such dysfunction is associated with elevated levels of the Src homology region 2 domain-containing phosphatase-1 (SHP-1) and phosphatases regulating Akt activation. Indeed, concomitant inhibition of both SHP-1 and phosphatases that regulate Akt activation conferred upon TADC and MoDC the capacity to take up and process IC and induce antitumor immunity in vivo. This work identifies the molecular checkpoints that govern activation of MoDC and TADC and their capacity to elicit T cell immunity.

  View details for PubMedID 27812544

  View details for PubMedCentralID PMC5085602

• Normalizing Microbiota-Induced Retinoic Acid Deficiency Stimulates Protective CD8(+) T Cell-Mediated Immunity in Colorectal Cancer. Immunity Bhattacharya, N., Yuan, R., Prestwood, T. R., Penny, H. L., DiMaio, M. A., Reticker-Flynn, N. E., Krois, C. R., Kenkel, J. A., Pham, T. D., Carmi, Y., Tolentino, L., Choi, O., Hulett, R., Wang, J., Winer, D. A., Napoli, J. L., Engleman, E. G. 2016; 45 (3): 641-655

  Abstract

  Although all-trans-retinoic acid (atRA) is a key regulator of intestinal immunity, its role in colorectal cancer (CRC) is unknown. We found that mice with colitis-associated CRC had a marked deficiency in colonic atRA due to alterations in atRA metabolism mediated by microbiota-induced intestinal inflammation. Human ulcerative colitis (UC), UC-associated CRC, and sporadic CRC specimens have similar alterations in atRA metabolic enzymes, consistent with reduced colonic atRA. Inhibition of atRA signaling promoted tumorigenesis, whereas atRA supplementation reduced tumor burden. The benefit of atRA treatment was mediated by cytotoxic CD8(+) T cells, which were activated due to MHCI upregulation on tumor cells. Consistent with these findings, increased colonic expression of the atRA-catabolizing enzyme, CYP26A1, correlated with reduced frequencies of tumoral cytotoxic CD8(+) T cells and with worse disease prognosis in human CRC. These results reveal a mechanism by which microbiota drive colon carcinogenesis and highlight atRA metabolism as a therapeutic target for CRC.

  View details for DOI 10.1016/j.immuni.2016.08.008

  View details for PubMedID 27590114

  View details for PubMedCentralID PMC5132405

• Extracellular matrix microarrays to study inductive signaling for endoderm specification. Acta biomaterialia Malta, D. F., Reticker-Flynn, N. E., da Silva, C. L., Cabral, J. M., Fleming, H. E., Zaret, K. S., Bhatia, S. N., Underhill, G. H. 2016; 34: 30-40

  Abstract

  During tissue development, stem and progenitor cells are faced with fate decisions coordinated by microenvironmental cues. Although insights have been gained from in vitro and in vivo studies, the role of the microenvironment remains poorly understood due to the inability to systematically explore combinations of stimuli at a large scale. To overcome such restrictions, we implemented an extracellular matrix (ECM) array platform that facilitates the study of 741 distinct combinations of 38 different ECM components in a systematic, unbiased and high-throughput manner. Using embryonic stem cells as a model system, we derived definitive endoderm progenitors and applied them to the array platform to study the influence of ECM, including the interactions of ECM with growth factor signaling, on the specification of definitive endoderm cells towards the liver and pancreas fates. We identified ECM combinations that influence endoderm fate decisions towards these lineages, and demonstrated the utility of this platform for studying ECM-mediated modifications to signal activation during liver specification. In particular, defined combinations of fibronectin and laminin isoforms, as well as combinations of distinct collagen subtypes, were shown to influence SMAD pathway activation and the degree of hepatic differentiation. Overall, our systematic high-throughput approach suggests that ECM components of the microenvironment have modulatory effects on endoderm differentiation, including effects on lineage fate choice and cell adhesion and survival during the differentiation process. This platform represents a robust tool for analyzing effects of ECM composition towards the continued improvement of stem cell differentiation protocols and further elucidation of tissue development processes.Cellular microarrays can provide the capability to perform high-throughput investigations into the role of microenvironmental signals in a variety of cell functions. This study demonstrates the utility of a high-throughput cellular microarray approach for analyzing the effects of extracellular matrix (ECM) in liver and pancreas differentiation of endoderm progenitor cells. Despite an appreciation that ECM is likely involved in these processes, the influence of ECM, particularly combinations of matrix proteins, had not been systematically explored. In addition to the identification of relevant ECM compositions, this study illustrates the capability of the cellular microarray platform to be integrated with a diverse range of cell fate measurements, which could be broadly applied towards the investigation of cell fate regulation in other tissue development and disease contexts.

  View details for DOI 10.1016/j.actbio.2016.02.014

  View details for PubMedID 26883775

• Akt and SHP-1 are DC-intrinsic checkpoints for tumor immunity. JCI insight Carmi, Y. n., Prestwood, T. R., Spitzer, M. H., Linde, I. L., Chabon, J. n., Reticker-Flynn, N. E., Bhattacharya, N. n., Zhang, H. n., Zhang, X. n., Basto, P. A., Burt, B. M., Alonso, M. N., Engleman, E. G. 2016; 1 (18): e89020

  Abstract

  BM-derived DC (BMDC) are powerful antigen-presenting cells. When loaded with immune complexes (IC), consisting of tumor antigens bound to antitumor antibody, BMDC induce powerful antitumor immunity in mice. However, attempts to employ this strategy clinically with either tumor-associated DC (TADC) or monocyte-derived DC (MoDC) have been disappointing. To investigate the basis for this phenomenon, we compared the response of BMDC, TADC, and MoDC to tumor IgG-IC. Our findings revealed, in both mice and humans, that upon exposure to IgG-IC, BMDC internalized the IC, increased costimulatory molecule expression, and stimulated autologous T cells. In contrast, TADC and, surprisingly, MoDC remained inert upon contact with IC due to dysfunctional signaling following engagement of Fcγ receptors. Such dysfunction is associated with elevated levels of the Src homology region 2 domain-containing phosphatase-1 (SHP-1) and phosphatases regulating Akt activation. Indeed, concomitant inhibition of both SHP-1 and phosphatases that regulate Akt activation conferred upon TADC and MoDC the capacity to take up and process IC and induce antitumor immunity in vivo. This work identifies the molecular checkpoints that govern activation of MoDC and TADC and their capacity to elicit T cell immunity.

  View details for PubMedID 27812544

• Normalizing microbiota-induced retinoic acid deficiency stimulates protective CD8+ T-cell-mediated immunity in colorectal cancer Immunity Bhattacharya, N., Yuan, R., Prestwood, T., Penny, H., DiMaio, M., Reticker-Flynn, N., Krois, C., Kenkel, J., Pham, T., Carmi, Y., Tolentino, L., Choi, O., Hulett, R., Wang, J., Winer, D., Napoli, J., Engleman, E. 2016; 45: 641–55

  Abstract

  Although all-trans-retinoic acid (atRA) is a key regulator of intestinal immunity, its role in colorectal cancer (CRC) is unknown. We found that mice with colitis-associated CRC had a marked deficiency in colonic atRA due to alterations in atRA metabolism mediated by microbiota-induced intestinal inflammation. Human ulcerative colitis (UC), UC-associated CRC, and sporadic CRC specimens have similar alterations in atRA metabolic enzymes, consistent with reduced colonic atRA. Inhibition of atRA signaling promoted tumorigenesis, whereas atRA supplementation reduced tumor burden. The benefit of atRA treatment was mediated by cytotoxic CD8(+) T cells, which were activated due to MHCI upregulation on tumor cells. Consistent with these findings, increased colonic expression of the atRA-catabolizing enzyme, CYP26A1, correlated with reduced frequencies of tumoral cytotoxic CD8(+) T cells and with worse disease prognosis in human CRC. These results reveal a mechanism by which microbiota drive colon carcinogenesis and highlight atRA metabolism as a therapeutic target for CRC.

  View details for DOI 10.1016/j.immuni.2016.08.008

  View details for PubMedCentralID PMC5132405

• Adhesion of tumor cells to ECM microarrays identifies novel ECM interactions in metastasis Reticker-Flynn, N. E., Braga Malta, D. F., Winslow, M. M., Xu, M. J., Lamar, J. M., Hynes, R. O., Jacks, T. E., Bhatia, S. N. AMER ASSOC CANCER RESEARCH. 2012

  View details for DOI 10.1158/1538-7445.AM2012-2973

  View details for Web of Science ID 000209701504449