Hypoxia-mediated repression of pyruvate carboxylase drives immunosuppression.

BACKGROUND: Metabolic plasticity mediates breast cancer survival, growth, and immune evasion during metastasis. However, how tumor cell metabolism is influenced by and feeds back to regulate breast cancer progression are not fully understood. We identify hypoxia-mediated suppression of pyruvate carboxylase (PC), and subsequent induction of lactate production, as a metabolic regulator of immunosuppression. METHODS: We used qPCR, immunoblot, and reporter assays to characterize repression of PC in hypoxic primary tumors. Steady state metabolomics were used to identify changes in metabolite pools upon PC depletion. In vivo tumor growth and metastasis assays were used to evaluate the impact of PC manipulation and pharmacologic inhibition of lactate transporters. Immunohistochemistry, flow cytometry, and global gene expression analyzes of tumor tissue were employed to characterize the impact of PC depletion on tumor immunity. RESULTS: PC is essential for metastatic colonization of the lungs. In contrast, depletion of PC in tumor cells promotes primary tumor growth. This effect was only observed in immune competent animals, supporting the hypothesis that repression of PC can suppress anti-tumor immunity. Exploring key differences between the pulmonary and mammary environments, we demonstrate that hypoxia potently downregulated PC. In the absence of PC, tumor cells produce more lactate and undergo less oxidative phosphorylation. Inhibition of lactate metabolism was sufficient to restore T cell populations to PC-depleted mammary tumors. CONCLUSIONS: We present a dimorphic role for PC in primary mammary tumors vs. pulmonary metastases. These findings highlight a key contextual role for PC-directed lactate production as a metabolic nexus connecting hypoxia and antitumor immunity.

Cereblon harnesses Myc-dependent bioenergetics and activity of CD8+ T lymphocytes.

Immunomodulatory drugs, such as thalidomide and related compounds, potentiate T-cell effector functions. Cereblon (CRBN), a substrate receptor of the DDB1-cullin-RING E3 ubiquitin ligase complex, is the only molecular target for this drug class, where drug-induced, ubiquitin-dependent degradation of known "neosubstrates," such as IKAROS, AIOLOS, and CK1α, accounts for their biological activity. Far less clear is whether these CRBN E3 ligase-modulating compounds disrupt the endogenous functions of CRBN. We report that CRBN functions in a feedback loop that harnesses antigen-specific CD8+ T-cell effector responses. Specifically, Crbn deficiency in murine CD8+ T cells augments their central metabolism manifested as elevated bioenergetics, with supraphysiological levels of polyamines, secondary to enhanced glucose and amino acid transport, and with increased expression of metabolic enzymes, including the polyamine biosynthetic enzyme ornithine decarboxylase. Treatment with CRBN-modulating compounds similarly augments central metabolism of human CD8+ T cells. Notably, the metabolic control of CD8+ T cells by modulating compounds or Crbn deficiency is linked to increased and sustained expression of the master metabolic regulator MYC. Finally, Crbn-deficient T cells have augmented antigen-specific cytolytic activity vs melanoma tumor cells, ex vivo and in vivo, and drive accelerated and highly aggressive graft-versus-host disease. Therefore, CRBN functions to harness the activation of CD8+ T cells, and this phenotype can be exploited by treatment with drugs.

GM-CSF-dependent pSTAT5 sensitivity is a feature with therapeutic potential in chronic myelomonocytic leukemia.

Granulocyte-macrophage-colony-stimulating factor (GM-CSF) hypersensitivity is a hallmark of juvenile myelomonocytic leukemia (JMML) but has not been systematically shown in the related human disease chronic myelomonocytic leukemia (CMML). We find that primary CMML samples demonstrate GM-CSF-dependent hypersensitivity by hematopoietic colony formation assays and phospho-STAT5 (pSTAT5) flow cytometry compared with healthy donors. Among CMML patients, the pSTAT5 hypersensitive response positively correlated with high-risk disease, peripheral leukocytes, monocytes, and signaling-associated mutations. When compared with IL-3 and G-CSF, GM-CSF hypersensitivity was cytokine specific and thus a possible target for intervention in CMML. To explore this possibility, we treated primary CMML cells with KB003, a novel monoclonal anti-GM-CSF antibody, and JAK2 inhibitors. We found that an elevated proportion of immature GM-CSF receptor-α(R) subunit-expressing cells were present in the bone marrow myeloid compartment of CMML. In survival assays, we found that myeloid and monocytic progenitors were sensitive to GM-CSF signal inhibition. Our data indicate that a committed myeloid precursor expressing CD38 may represent the progenitor population with enhanced GM-CSF dependence in CMML, consistent with results in JMML. These preclinical data indicate that GM-CSF signaling inhibitors merit further investigation in CMML and that GM-CSFR expression on myeloid progenitors may be a biomarker for this therapy.

Fibrosis and subsequent cytopenias are associated with basic fibroblast growth factor-deficient pluripotent mesenchymal stromal cells in large granular lymphocyte leukemia.

Cytopenias occur frequently in systemic lupus erythematosus, rheumatoid arthritis, Felty's syndrome, and large granular lymphocyte (LGL) leukemia, but the bone marrow microenvironment has not been systematically studied. In LGL leukemia (n = 24), retrospective analysis of bone marrow (BM) histopathology revealed severe fibrosis in 15 of 24 patients (63%) in association with the presence of cytopenias, occurrence of autoimmune diseases, and splenomegaly, but was undetectable in control cases with B cell malignancies (n = 11). Fibrosis severity correlated with T cell LGL cell numbers in the BM, but not in the periphery, suggesting deregulation is limited to the BM microenvironment. To identify fibrosis-initiating populations, primary mesenchymal stromal cultures (MSCs) from patients were characterized and found to display proliferation kinetics and overabundant collagen deposition, but displayed normal telomere lengths and osteoblastogenic, chondrogenic, and adipogenic differentiation potentials. To determine the effect of fibrosis on healthy hematopoietic progenitor cells (HPCs), bioartificial matrixes from rat tail or purified human collagen were found to suppress HPC differentiation and proliferation. The ability of patient MSCs to support healthy HSC proliferation was significantly impaired, but could be rescued with collagenase pretreatment. Clustering analysis confirmed the undifferentiated state of patient MSCs, and pathway analysis revealed an inverse relationship between cell division and profibrotic ontologies associated with reduced basic fibroblast growth factor production, which was confirmed by ELISA. Reconstitution with exogenous basic fibroblast growth factor normalized patient MSC proliferation, collagen deposition, and HPC supportive function, suggesting LGL BM infiltration and secondary accumulation of MSC-derived collagen is responsible for hematopoietic failure in autoimmune-associated cytopenias in LGL leukemia.

Overexpression of TCL1 activates the endoplasmic reticulum stress response: a novel mechanism of leukemic progression in mice.

Chronic lymphocytic leukemia (CLL) represents 30% of adult leukemia. TCL1 is expressed in ~ 90% of human CLL. Transgenic expression of TCL1 in murine B cells (Eµ-TCL1) results in mouse CLL. Here we show for the first time that the previously unexplored endoplasmic reticulum (ER) stress response is aberrantly activated in Eµ-TCL1 mouse and human CLL. This includes activation of the IRE-1/XBP-1 pathway and the transcriptionally up-regulated expression of Derlin-1, Derlin-2, BiP, GRP94, and PDI. TCL1 associates with the XBP-1 transcription factor, and causes the dysregulated expression of the transcription factors, Pax5, IRF4, and Blimp-1, and of the activation-induced cytidine deaminase. In addition, TCL1-overexpressing CLL cells manufacture a distinctly different BCR, as we detected increased expression of membrane-bound IgM and altered N-linked glycosylation of Igα and Igß, which account for the hyperactive BCR in malignant CLL. To demonstrate that the ER stress-response pathway is a novel molecular target for the treatment of CLL, we blocked the IRE-1/XBP-1 pathway using a novel inhibitor, and observed apoptosis and significantly stalled growth of CLL cells in vitro and in mice. These studies reveal an important role of TCL1 in activating the ER stress response in support for malignant progression of CLL.

A phase II multicenter rabbit anti-thymocyte globulin trial in patients with myelodysplastic syndromes identifying a novel model for response prediction.

Immune dysregulation is a mechanism contributing to ineffective hematopoiesis in a subset of myelodysplastic syndrome patients. We report the first US multicenter non-randomized, phase II trial examining the efficacy of rabbit(r)-anti-thymocyte globulin using 2.5 mg/kg/day administered daily for 4 doses. The primary end point was hematologic response; secondary end points included duration of response, time to response, time to progression, and tolerance. Nine (33%;95% confidence interval=17%-54%) of the 27 patients treated experienced durable hematologic improvement in an intent-to-treat analysis with a median time to response and median response duration of 75 and 245 days, respectively. While younger age is the most significant factor favoring equine(e)-anti-thymocyte globulin response, treatment outcome on this study was independent of age (P=0.499). A shorter duration between diagnosis and treatment showed a positive trend (P=0.18), but International Prognostic Scoring System score (P=0.150), karyotype (P=0.319), and age-adjusted bone marrow cellularity (P=0.369) were not associated with response classification. Since activated T-lymphocytes are the primary cellular target of anti-thymocyte globulin, a T-cell expression profiling was conducted in a cohort of 38 patients consisting of rabbit and equine-antithymocyte globulin-treated patients. A model containing disease duration, CD8 terminal memory T cells and T-cell proliferation-associated-antigen expression predicted response with the greatest accuracy using a leave-one-out cross validation approach. This profile categorized patients independent of other covariates, including treatment type and age using a leave-one-out-cross-validation approach (75.7%). Therefore, rabbit-anti-thymocyte globulin has hematologic remitting activity in myelodysplastic syndrome and a T-cell activation profile has potential utility classifying those who are more likely to respond (NCT00466843 clinicaltrials.gov).

Expansion of effector memory regulatory T cells represents a novel prognostic factor in lower risk myelodysplastic syndrome.

Myelodysplastic syndromes are premalignant diseases characterized by cytopenias, myeloid dysplasia, immune dysregulation with association to autoimmunity, and variable risk for acute myeloid leukemia transformation. Studies of FOXP3(+) regulatory T cells (Tregs) indicate that the number and/or activation state may influence cancer progression in these patients. Focusing on patients with a lower risk for leukemia transformation, 18 (34.6%) of 52 patients studied displayed an altered Treg compartment compared with age-matched controls. Delineation of unique Treg subsets revealed that an increase in the absolute number of CD4(+)FOXP3(+)CD25(+)CD127(low)CD45RA(-)CD27(-) Tregs (effector memory Tregs [Treg(EM)]) was significantly associated with anemia (p = 0.046), reduced hemoglobin (p = 0.038), and blast counts ≥5% (p = 0.006). In healthy donors, this Treg(EM) population constitutes only 2% of all Tregs (one to six Tregs per microliter) in peripheral blood but, when isolated, exhibit greater suppressive activity in vitro. With a median follow-up of 3.1 y (range 2.7-4.9 y) from sample acquisition, increased numbers of Treg(EM) cells proved to have independent prognostic importance in survival estimates, suggesting that enumeration of this Treg subset may be a more reliable indicator of immunological escape than FOXP3(+) T cells as a whole. Based on multivariate analyses, Treg(EM) impacted survival independently from myeloblast characteristics, cytopenias, karyotype, and comorbidities. Based on these findings, Treg(EM) cell expansion may be synonymous with human Treg activation and indicate microenvironmental changes conducive to transformation in myelodysplastic syndromes.

Low-Cost, High-Pressure-Synthesized Oxygen-Entrapping Materials to Improve Treatment of Solid Tumors.

Tumor hypoxia drives resistance to many cancer therapies, including radiotherapy and chemotherapy. Methods that increase tumor oxygen pressures, such as hyperbaric oxygen therapy and microbubble infusion, are utilized to improve the responses to current standard-of-care therapies. However, key obstacles remain, in particular delivery of oxygen at the appropriate dose and with optimal pharmacokinetics. Toward overcoming these hurdles, gas-entrapping materials (GeMs) that are capable of tunable oxygen release are formulated. It is shown that injection or implantation of these materials into tumors can mitigate tumor hypoxia by delivering oxygen locally and that these GeMs enhance responsiveness to radiation and chemotherapy in multiple tumor types. This paper also demonstrates, by comparing an oxygen (O2 )-GeM to a sham GeM, that the former generates an antitumorigenic and immunogenic tumor microenvironment in malignant peripheral nerve sheath tumors. Collectively the results indicate that the use of O2 -GeMs is promising as an adjunctive strategy for the treatment of solid tumors.

Regulatory T-cell trafficking: from thymic development to tumor-induced immune suppression.

Regulatory T cells (Tregs) have become a priority for many investigators in immunology due to their potent immunosuppressive and tolerogenic effects. While Treg activity is required for normal immune homeostasis, dysregulation of their numbers can induce autoimmunity or aid in the pathogenesis of disease. Therefore, great effort has been made to understand the mechanisms by which Tregs accumulate in different areas of the body. Like other lymphocytes, Tregs migrate in response to a network of chemotactic stimuli involving chemokines, chemokine receptors, integrins, and their corresponding ligands. However, many of these stimuli are exclusive to Tregs, inducing their migration while leaving conventional populations unaffected. It is these selective stimuli that result in increased ratios of Tregs among conventional effector populations, leading to changes in immune suppression and homeostasis. This review explores selective Treg trafficking during thymic Treg development, migration to secondary lymphoid tissues and emigration into the periphery during homeostatic conditions, inflammation, and the tumor microenvironment, placing emphasis on stimuli that selectively recruits Tregs to target locations.

NK-dependent increases in CCL22 secretion selectively recruits regulatory T cells to the tumor microenvironment.

Tumor-induced immune suppression involves the accumulation of immune-suppressive infiltrates in the microenvironment. This study demonstrates increased numbers of CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) in the lungs of C57BL/6 mice bearing a metastatic Lewis lung carcinoma (LLC) variant. These Tregs suppressed the proliferation of endogenous CD4(+)CD25(-) cells and expressed higher levels of the chemokine receptor CCR4 than other types of T cells. LLC-bearing lungs secreted elevated levels of the CCR4-associated chemokine CCL22 compared with normal lungs. However, CCL22 was not secreted by LLC or normal epithelial controls, suggesting that CCL22 is secreted by a nonepithelial component of the microenvironment. Migration assays revealed that medium conditioned by LLC-bearing lungs selectively recruited Tregs at higher frequencies than did medium conditioned by normal lungs. Neutralization of CCL22 significantly reduced this selective recruitment toward both conditioned media. A series of immunomagnetic isolations, FACS, and flow cytometric analyses were used to isolate different cellular fractions from both normal and LLC-bearing lungs. When isolated, only the NK-containing fractions secreted CCL22, and the same fraction isolated from LLC-bearing lungs secreted higher levels. Depletion of NK cells from both normal and LLC-bearing lung tissue significantly reduced CCL22 secretion, suggesting that a large portion of secreted CCL22 is NK cell dependent. Flow cytometric analysis of the lung NK compartments revealed no significant increase in NK cell numbers across LLC-bearing lung tissue as a whole as compared with normal tissue. However, immunofluorescent staining revealed an increased frequency of NK cells at the tumor periphery that were closely associated with the elevated FoxP3(+) infiltrate.

Inducible Tertiary Lymphoid Structures: Promise and Challenges for Translating a New Class of Immunotherapy.

Tertiary lymphoid structures (TLS) are ectopically formed aggregates of organized lymphocytes and antigen-presenting cells that occur in solid tissues as part of a chronic inflammation response. Sharing structural and functional characteristics with conventional secondary lymphoid organs (SLO) including discrete T cell zones, B cell zones, marginal zones with antigen presenting cells, reticular stromal networks, and high endothelial venues (HEV), TLS are prominent centers of antigen presentation and adaptive immune activation within the periphery. TLS share many signaling axes and leukocyte recruitment schemes with SLO regarding their formation and function. In cancer, their presence confers positive prognostic value across a wide spectrum of indications, spurring interest in their artificial induction as either a new form of immunotherapy, or as a means to augment other cell or immunotherapies. Here, we review approaches for inducible (iTLS) that utilize chemokines, inflammatory factors, or cellular analogues vital to TLS formation and that often mirror conventional SLO organogenesis. This review also addresses biomaterials that have been or might be suitable for iTLS, and discusses remaining challenges facing iTLS manufacturing approaches for clinical translation.

High-Dimensional Flow Cytometry Analysis of Regulatory Receptors on Human T Cells, NK Cells, and NKT Cells.

The field of flow cytometry has witnessed rapid technological advancements in the last few decades. While the founding principles of fluorescent detection on cells (or particles) within a uniform fluid stream remains largely unchanged, the availability more sensitive cytometers with the ability to multiplex more and more florescent signals has resulted in very complex high-order assays. This results in the co-use of fluorophores with increased levels of emission overlap and/or spillover spreading than in years past and thus requires careful and well thought out planning for flow cytometry assay development. As an example, we present the development of a large 18-color (20 parameter) flow cytometry assay designed to take an in depth analysis of effector lymphocyte phenotypes, with careful attention to assay controls and panel design.

Checkpoint blockade accelerates a novel switch from an NKT-driven TNFα response toward a T cell driven IFN-γ response within the tumor microenvironment.

BACKGROUND: The temporal response to checkpoint blockade (CB) is incompletely understood. Here, we profiled the tumor infiltrating lymphocyte (TIL) landscape in response to combination checkpoint blockade at two distinct timepoints of solid tumor growth. METHODS: C57BL/6 mice bearing subcutaneous MC38 tumors were treated with anti-PD-1 and/or anti-CTLA-4 antibodies. At 11 or 21 days, TIL phenotype and effector function were analyzed in excised tumor digests using high parameter flow cytometry. The contributions of major TIL populations toward overall response were then assessed using ex vivo cytotoxicity and in vivo tumor growth assays. RESULTS: The distribution and effector function among 37 distinct TIL populations shifted dramatically between early and late MC38 growth. At 11 days, the immune response was dominated by Tumor necrosis factor alpha (TNFα)-producing NKT, representing over half of all TIL. These were accompanied by modest frequencies of natural killer (NK), CD4+, or CD8+ T cells, producing low levels of IFN-γ. At 21 days, NKT populations were reduced to a combined 20% of TIL, giving way to increased NK, CD4+, and CD8+ T cells, with increased IFN-γ production. Treatment with CB accelerated this switch. At day 11, CB reduced NKT to less than 20% of all TIL, downregulated TNFα across NKT and CD4+ T cell populations, increased CD4+ and CD8+ TIL frequencies, and significantly upregulated IFN-γ production. Degranulation was largely associated with NK and NKT TIL. Blockade of H-2kb and/or CD1d during ex vivo cytotoxicity assays revealed NKT has limited direct cytotoxicity against parent MC38. However, forced CD1d overexpression in MC38 cells significantly diminished tumor growth, suggesting NKT TIL exerts indirect control over MC38 growth. CONCLUSIONS: Despite an indirect benefit of early NKT activity, CB accelerates a switch from TNFα, NKT-driven immune response toward an IFN-γ driven CD4+/CD8+ T cell response in MC38 tumors. These results uncover a novel NKT/T cell switch that may be a key feature of CB response in CD1d+ tumors.

NK depletion results in increased CCL22 secretion and Treg levels in Lewis lung carcinoma via the accumulation of CCL22-secreting CD11b+CD11c+ cells.

Tumor-induced immune suppression involves the accumulation of suppressive infiltrates in the tumor microenvironment such as regulatory T-cells (Tregs). Previous studies demonstrated that NK-dependant increases in CCL22 secretion selectively recruit Tregs toward murine lungs bearing Lewis Lung Carcinoma (LLC). To extend the in vitro studies, the present studies utilized in vivo depletion of NK cells to ascertain the contribution of NK-derived CCL22 toward total CCL22 and subsequent Treg levels in both normal and LLC-bearing lungs. However, NK depletion had the unexpected effect of increasing both CCL22 secretion and Treg levels in the lungs of NK-depleted LLC-bearing mice. This was concurrent with an increase in tumor burden. Flow cytometry and a series of both immunomagnetic and FACS isolations were used to identify the CCL22-producing cellular fractions in LLC-bearing lungs. A novel CD11b(+)CD11c(+) cell population was identified that accumulates in large numbers in NK-depleted LLC-bearing lung tissue. These CD11b(+)CD11c(+) cells secreted large amounts of CCL22 that may overcompensate for the loss of NK-derived CCL22 in the lungs of NK-depleted LLC-bearing mice. Taken together, these data suggest that NK cells play both a positive and negative role in the regulation of CCL22 secretion and, in turn, the recruitment of Tregs toward LLC-bearing lungs.

Multi-Dimensional Flow Cytometry Analyses Reveal a Dichotomous Role for Nitric Oxide in Melanoma Patients Receiving Immunotherapy.

Phenotyping of immune cell subsets in clinical trials is limited to well-defined phenotypes, due to technological limitations of reporting flow cytometry multi-dimensional phenotyping data. We developed a multi-dimensional phenotyping analysis tool and applied it to detect nitric oxide (NO) levels in peripheral blood immune cells before and after adjuvant ipilimumab co-administration with a peptide vaccine in melanoma patients. We analyzed inhibitory and stimulatory markers for immune cell phenotypes that were felt to be important in the NO analysis. The pipeline allows visualization of immune cell phenotypes without knowledge of clustering techniques and to categorize cells by association with relapse-free survival (RFS). Using this analysis, we uncovered the potential for a dichotomous role of NO as a pro- and anti-melanoma factor. NO was found in subsets of immune-suppressor cells associated with shorter-term (≤ 1 year) RFS, whereas NO was also present in immune-stimulatory effector cells obtained from patients with significant longer-term (> 1 year) RFS. These studies provide insights into the cell-specific immunomodulatory role of NO. The methods presented herein can be applied to monitor the pro- and anti-tumor effects of a variety of immune-based therapeutics in cancer patients. Clinical Trial Registration Number: NCT00084656 (https://clinicaltrials.gov/ct2/show/NCT00084656).

STING Signaling in Melanoma Cells Shapes Antigenicity and Can Promote Antitumor T-cell Activity.

STING (stimulator of IFN genes) signaling is an innate immune pathway for induction of a spontaneous antitumor T-cell response against certain immunogenic tumors. Although antigen-presenting cells are known to be involved in this process, insight into the participation of tumor cell-intrinsic STING signaling remains weak. In this study, we find diversity in the regulation of STING signaling across a panel of human melanoma cell lines. We show that intact activation of STING signaling in a subset of human melanoma cell lines enhances both their antigenicity and susceptibility to lysis by human melanoma tumor-infiltrating lymphocytes (TIL) through the augmentation of MHC class I expression. Conversely, defects in the STING signaling pathway protect melanoma cells from increased immune recognition by TILs and limit their sensitivity to TIL lysis. Based on these findings, we propose that defects in tumor cell-intrinsic STING signaling can mediate not only tumor immune evasion but also resistance to TIL-based immunotherapies.

A Phase II Study to Determine the Safety and Efficacy of the Oral Inhibitor of Indoleamine 2,3-Dioxygenase (IDO) Enzyme INCB024360 in Patients with Myelodysplastic Syndromes.

BACKGROUND: INCB024360 is an oral inhibitor of the enzyme indoleamine 2,3-dioxygenase (IDO), which catalyzes the degradation of tryptophan to kynurenine. Preclinical data suggest that IDO1 inhibition by INCB024360 will increase T cell proliferation, and decrease T regulatory cells and myeloid derived suppressor cells suppressive activity. We conducted a phase II study to explore activity and pharmacodynamics of INCB024360 in patients with myelodysplastic syndromes. PATIENTS AND METHODS: All patients were treated with INCB024360 600 mg orally twice a day for at least 16 weeks. Fifteen patients were enrolled. The median age was 72 years. The International Prognostic Scoring System risk was low in 27% (n = 4), intermediate-1 in 47% (n = 7), and intermediate-2 in 27% (n = 4). All patients had prior azacitidine. RESULTS: The best response was stable disease in 12 (80%) patients and progressive disease in 3 (20%) patients. The treatment was relatively well-tolerated. One patient developed hypothyroidism and adrenal insufficiency (grade 2), and 1 patient had low testosterone level. The mean IDO expression was 39% at baseline and 26% after treatment (n = 9; P = .4). The mean burst forming unit-erythroid changed from 72 to 191 colonies/106 (n = 5; P = .036), and the mean colony forming unit-granulocye, monocyte from 62 to 180 colonies/106 (n = 6; P = .5). The mean myeloid derived suppressor cell % (CD33Lin-HLA cells) was 29.5% at baseline compared with 27.6% after treatment (n = 9; P = .7). The mean T-regulatory effector memory cell % changed from 9.6% at screening to 7.4% at end of treatment (n = 14; P = .8). The mean kynurenine/tryptophan ratio decreased from 45 at baseline to 26 (42% reduction) at cycle 2, day 1 (P < .005). CONCLUSION: Future directions may include testing INCB024360 early in the course of the disease.

Induction of Tertiary Lymphoid Structures With Antitumor Function by a Lymph Node-Derived Stromal Cell Line.

Tertiary lymphoid structures (TLSs) associate with better prognosis in certain cancer types, but their underlying formation and immunological benefit remain to be determined. We established a mouse model of TLSs to study their contribution to antitumor immunity. Because the stroma in lymph nodes (sLN) participates in architectural support, lymphogenesis, and lymphocyte recruitment, we hypothesized that TLSs can be created by sLN. We selected a sLN line with fibroblast morphology that expressed sLN surface markers and lymphoid chemokines. The subcutaneous injection of the sLN line successfully induced TLSs that attracted infiltration of host immune cell subsets. Injection of MC38 tumor lysate-pulsed dendritic cells activated TLS-residing lymphocytes to demonstrate specific cytotoxicity. The presence of TLSs suppressed MC38 tumor growth in vivo by improving antitumor activity of tumor-infiltrating lymphocytes with downregulated immune checkpoint proteins (PD-1 and Tim-3). Future engineering of sLN lines may allow for further enhancements of TLS functions and immune cell compositions.