Inducible T-Cell Costimulator Ligand Plays a Dual Role in Melanoma Metastasis upon Binding to Osteopontin or Inducible T-Cell Costimulator

Recently, we demonstrated that inducible T-cell costimulator (ICOS) shares its unique ligand (ICOSL) with osteopontin (OPN), and OPN/ICOSL binding promotes tumor metastasis and angiogenesis in the 4T1 breast cancer model. Literature showed that OPN promotes melanoma metastasis by suppressing T-cell activation and recruiting myeloid suppressor cells (MDSC). On the opposite, ICOS/ICOSL interaction usually sustains an antitumor response. Here, we engineered murine B16F10 melanoma cells, by transfecting or silencing ICOSL. In vitro data showed that loss of ICOSL favors anchorage-independent growth and induces more metastases in vivo, compared to ICOSL expressing cells. To dissect individual roles of the three molecules, we compared data from C57BL/6 with those from OPN-KO, ICOS-KO, and ICOSL-KO mice, missing one partner at a time. We found that OPN produced by the tumor microenvironment (TME) favors the metastasis by interacting with stromal ICOSL. This activity is dominantly inhibited by ICOS expressed on TME by promoting Treg expansion. Importantly, we also show that OPN and ICOSL highly interact in human melanoma metastases compared to primary tumors. Interfering with this binding may be explored in immunotherapy either for nonresponding or patients resistant to conventional therapies.

Antibodies to ILT3 abrogate myeloid immunosuppression and enable tumor killing

Tumor myeloid suppressor cells impede response to T cell checkpoint immunotherapy. Immunoglobulin-like transcript 3 (ILT3, gene name, LILRB4) expressed on dendritic cells (DCs) promotes antigen-specific tolerance. Circulating monocytic MDSCs that express ILT3 have been linked to clinical outcomes and a soluble form of ILT3 is elevated in certain cancers. We find that LILRB4 expression is correlated with Gene Expression Profile of T-cell inflamed tumor microenvironment shown to be significantly associated with response to the anti-PD1 antibody pembrolizumab across several tumor types. A potent and selective anti-ILT3 mAb effectively antagonized IL-10 polarization of DCs and enabled T cell priming. In an MLR assay anti-ILT3 combined with pembrolizumab afforded greater CD8+ T cell activation compared to either agent alone. Anti-ILT3 antibodies impaired the acquisition of a suppressive phenotype of monocytes co-cultured with SK-MEL-5 cancer cells, accompanied by a reduction in surface detection of peptidase inhibitor 16, a cis interaction candidate for ILT3. Growth of myeloid cell-abundant SK-MEL-5 tumors was abrogated by ILT3 blockade and remodeling of the immune tumor microenvironment was evident by CyTOF. These data support the testing of anti-ILT3 antibodies for the treatment of a wide range of solid tumors replete with myeloid cells.

Role of pre-metastatic niche in organ specificity of breast cancer metastasis. Influence on metastatic potential as a basis for CDK4/6-inhibition efficacy in early therapy of disseminated hormone-receptor-positive disease

Influencing the pre-metastatic niche is a very perspective cancer treatment strategy in order of preventing metastases formation. It was found that bone marrow progenitor cells and tumor cells secreting biological compounds are key components in the formation of the pre-metastatic niche. Myeloid suppressor cells (MSCs) are the main type of bone marrow cells in pre-metastatic niches. At the same time, tumor-associated chronic inflammation induces the expression of proinflammatory cytokines triggering myeloid cells differentiation into myeloid suppressor cells. When circulating tumor cells enter the circulatory channel, their interaction with immune cells is observed, which additionally influences the pre-metastatic site preparation. Studies have shown that the entire spectrum of immune cells is capable of influencing the metastasis formation by circulating tumor cells. The epithelialmesenchymal transition with the tumor cell transporting form appearence was found to be related to the function of the ZEB1 protein. Its activity is regulated by numerous signaling mechanisms at the transcriptional level, including TGFβ, Wnt and Notch. This initiates epithelial-mesenchymal transition of breast cancer cells. Zhang Z.et al. proved that CDK4/6 blocking leads ZEB1 protein stability decreasing, preventing metastasis in breast cancer in vitro and in vivo. Moreover, USP51 deubiquitinase has been identified as a target of cyclin-dependent 4/6 kinases. At the molecular level, CDK4/6 phosphorylate and activates USP51, which then influences ZEB1 deubiquitination and stabilization. A positive correlation was demonstrated between the expression of p-RB (an indicator of CDK4/6 activity), p-USP51 and ZEB1 in breast cancer samples. Thus, the CDK4/6-USP51-ZEB1 axis may play a key role in the metastasis of breast cancer. In breast cancer cells, inhibition of CDK4/6 was shown to increase the expression of E-cadherin but decrease the expression of mesenchymal markers, reducing the migratory ability and invasiveness of breast cancer cell lines. This biological effect may also explain the clinical efficacy of the CDK4/6 inhibitor Abemaciclib in early-line therapy of metastatic breast cancer as well as in adjuvant combination hormone therapy for the prevention of metastatic lesions in patients at high risk of recurrence and progression in the MONARCH E study. Besides, there were no response predictors evaluated in trials investigating CDK4/6 in breast cancer treatment and it is unknown if there any differences in treatment response according to the metastatic site. The clinical cases demonstrate abemaciclib clinical efficacy in metastatic breast cancer treatment regardless of metastatic site.

Immune Profiles of Myeloma Tumor Microenvironment May Predict Sensitivity or Resistance to Elotuzumab

Background: Elotuzumab (ELO), an immunobiologic therapy targeting SLAMF7/CD319, is effective in the treatment of multiple myeloma (MM) with clinical indications in relapsed/refractory disease in combination with lenalidomide or pomalidomide. ELO binds SLAMF7 on the surface of MM cells to increase immune recognition while also binding SLAMF7 on NK cells resulting in the activation of an effector cell population capable of readily killing via antibody-dependent cellular cytotoxicity (ADCC) mechanisms. ELO efficacy has also been linked to enhanced antibody-dependent cellular phagocytosis (ADCP). Given the dependence of ELO activity on immune elements of the tumor microenvironment (TME), we hypothesized that characterization of the immunologic constituents of the immune TME (iTME) would provide cues capable of predicting clinical efficacy. Methods: Nineteen patients were enrolled on a single-center clinical trial run at Moffitt Cancer Center comparing clinical activity of ELO in combination with low-dose (10mg) vs high-dose (25mg) lenalidomide and dexamethasone in patients with biochemical relapse while on lenalidomide maintenance after first line therapy. Bone marrow aspirate (BMA) and peripheral blood (PB) samples we collected at baseline, after completion of 2 treatment cycles, and at time of progression. Cells isolated from the BMA were analyzed by multiparameter flow cytometry (MPFC) using 4 panels; 3 panels characterized lymphocytes according to maturation, activation and polarization (T H1, T H2, T H17 or T Reg) and a 4 th panel characterized myeloid elements. Data was acquired on a BD Symphony cytometer and analysis was performed using FlowJo software. Results: Patient samples were categorized according to initial therapeutic response. Responders (n=6) achieved >PR at best response, Progressors (n=5) were identified as patients whose disease markers increased >25% and Stable Disease (n=8) was identified as demonstrating <25% change in serologic disease markers. Here, we present a comparison of phenotypic profiles from the BM samples acquired at baseline before treatment initiation from patients classified as Responders or Progressors (patients demonstrating stable disease as best response were analyzed separately). Sample analysis by MPFC revealed distinct populations uniquely associated with responses as well as with treatment refractoriness. Principal component analysis (PCA) of the myeloid immune compartment shows 2 clusters representing distinct populations detectable only in Responders, while another large cluster, also expressing a granulocytic phenotype consistent with granulocytic myeloid suppressor cells, is prevalent in the Progressor patients but nearly absent from Responder patients, as might be predicted. Similarly, PCA identified monocyte/macrophage clusters uniquely associated with Responder or Progressor samples. Evaluation of lymphoid populations using 3 lymphoid panels also reveals distinctive clustering patters by PCA highlighting populations differentially associated with Responder or Progressor samples. Notably, while NK cells are present in all patient samples, there is a population of immature NK cells enriched in Responder patients that is largely absent from the Progressor population. Conclusion: Immune profiling of the myeloid and lymphoid components of the baseline BM iTME in MM prior to treatment with ELO reveals distinct patterns of cellular constitution associated with responsiveness or refractoriness to subsequent treatment. While NK cells are known to be important to the ELO mechanism of action, our data suggests that ELO activity is compromised in the absence of immature NK cells. This work suggests that measurable characteristics of the cellular components of the iTME may provide important cues to help predict ELO therapeutic efficacy. These observations will need to be confirmed in a larger data set. Disclosures Shain: Amgen Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi Genzyme: Consultancy, Speakers Bureau; Adaptive Biotechnologies Corporation: Consultancy, Speakers Bureau; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GlaxoSmithLine, LLC: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen oncology: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Karyopharm Therapeutics Inc.: Honoraria, Research Funding. Baz: BMS, sanofi, Karyopharm, Janssen, AbbVie: Consultancy, Research Funding; Oncopeptides: Consultancy; GlaxoSmithKline: Consultancy, Honoraria; Merck: Research Funding. Nishihori: Novartis: Research Funding; Karyopharm: Research Funding.

Deep Immune Profiling in Multiple Myeloma at Diagnosis and Under Lenalidomide Maintenance Therapy

Introduction Here we report the results of one of the secondary endpoints of the Finnish Myeloma Group-MM02 study; composition of bone marrow (BM) immune cell subsets at treatment start and during lenalidomide (Len) maintenance focusing on 2 different response groups: good responders (GRs) and poor responders (PRs) at pre- and post-treatment stages. We evaluated the BM immune profile with CyTOF (cytometry by time-of-flight). Our hypothesis was that there would be distinct differences in immune cell profiles between patients with good and poor response, especially in the T and NK cell subsets. Patients and methods Twenty-two patients were included in this CyTOF study. Eighteen were NDMM patients from FMG-MM02 study who received 3 RVD cycles followed by ASCT. Len started 3 months after ASCT 10 mg/day in 21/28-day cycles until progression or toxicity. BM samples were collected to the Finnish Hematology Registry Clinical Biobank (FHRB Biobank) at several timepoints; from 18 patients at diagnosis, from 11 patients 1 st sample at good response during Len and 2 nd sample if this good response was maintained and from 5 patients at relapse during Len. The patients in the good response cohort (n=11) had progression-free survival (PFS) > 5 years. For comparison, we included 4 BM samples from the FHRB Biobank, taken at a good response after ASCT from MM patients without exposure to Len. Results With a median follow-up of 81 months (13-97) the median PFS was not reached in the good response (GR) cohort and was 18 months in the poor response (PR) cohort. The 1 st GR samples were collected after a median of 21 (6-46) months of Len. The 2 nd samples in GR cohort were collected after a median of 56 (45-67) months of Len. The PR samples were taken after a median of 6 (2-23) months of Len. CyTOF analysis revealed distinct good and poor responder's immune signatures at baseline level. GR, baseline group has shifted phenotype of T cells toward the CD8 T cells, expressing markers, attributed to the cytotoxicity (CD45RA, CD57), as well as having slightly higher abundance of CD8 TE and lower abundance of CD8 naïve T cells. Total T cells amounts were significantly higher in GR. Increased expression of CD56, CD57, and CD16 were also seen on NK cells in GR at the baseline, indicating both maturation and cytotoxic potential of NKs. In contrast, a significant decrease of CD56 and CD16 expression suggesting reduced cytotoxic potential and increase of CD57 were seen on NKs in PR, baseline indicating senescence status a phenotype associated with exhaustion. By using viSNE we discovered two novel populations - MAC1, and MAC2, - associated with disease pathogenesis. We further investigated the composition of these populations, and it appears that MAC1 expressed CD38+CD56+CD45-CD19- presumably malignant plasma cells and MAC2 expressed CD45- CD14+CD38+CD56+TCRgd+CCR7+CCR6+CXCR4+ CXCR3+CXCR5+CD294+, which might be the novel populations, having the features of myeloid suppressor cells. These two immune cells were higher in PR (9.2% and 8.2%, respectively) at baseline as compared to the GR (2.3% and 1.7%). NKs, T cells, and B cells showed a high expression of monocytic marker CD14 and chemokine receptors (CCR7, CCR6, CXCR4, CXCR3, and CXCR5) in PR both at baseline and relapse. This might be attributed to either biological features of MM environment, or the high level of interaction between these populations and monocytes, which left traces of their membranes on the non-monocytic populations. Conclusions Patients, responded to the treatment, have higher abundances of effector/cytotoxic cells, expressing higher levels of CD57 and/or CD45RA for T cells, and CD57, CD16, and CD56 for NK cells indicating proper differentiation and maturation of T, and NK cells to effector and cytotoxic subsets. Additionally, those patients have less degree of tumor burden as well as decreased expression of chemokine receptors. During the therapy administration, good responders show the increase in effector memory CD4 and CD8 subsets of T cells abundance, indicating even the higher cytotoxic effect of immune system. Disclosures Silvennoinen: Amgen: Consultancy, Honoraria, Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Research Funding. Luoma: Amgen: Honoraria; Janssen: Honoraria; Incyte: Honoraria. Anttila: Amgen: Honoraria; Celgene: Honoraria; Janssen: Honoraria; Takeda: Honoraria. Säily: Takeda: Honoraria; Janssen: Honoraria; Sanofi: Honoraria; Celgene: Honoraria. Partanen: Takeda: Honoraria; Abbvie: Honoraria; Behring: Honoraria. Heckman: Novartis: Research Funding; Orion Pharma: Research Funding; Celgene/BMS: Research Funding; Oncopeptides: Consultancy, Research Funding; Kronos Bio, Inc.: Research Funding.

Granulocytic Myeloid-Derived Suppressor Cells in Cystic Fibrosis

Cystic Fibrosis (CF) is a genetic disease that causes chronic and severe lung inflammation and infection associated with high rates of mortality. In CF, disrupted ion exchange in the epithelium results in excessive mucus production and reduced mucociliary clearance, leading to immune system exacerbation and chronic infections with pathogens such as P. aeruginosa and S. aureus. Constant immune stimulation leads to altered immune responses including T cell impairment and neutrophil dysfunction. Specifically, CF is considered a Th17-mediated disease, and it has been proposed that both P. aeruginosa and a subset of neutrophils known as granulocytic myeloid suppressor cells (gMDSCs) play a role in T cell suppression. The exact mechanisms behind these interactions are yet to be determined, but recent works demonstrate a role for arginase-1. It is also believed that P. aeruginosa drives gMDSC function as a means of immune evasion, leading to chronic infection. Herein, we review the current literature regarding immune suppression in CF by gMDSCs with an emphasis on T cell impairment and the role of P. aeruginosa in this dynamic interaction.

Evolving Perspectives on Innate Immune Mechanisms of IPF

While epithelial-fibroblast interactions are viewed as the primary drivers of Idiopathic Pulmonary Fibrosis (IPF), evidence gleaned from animal modeling and human studies implicates innate immunity as well. To provide perspective on this topic, this review synthesizes the available data regarding the complex role of innate immunity in IPF. The role of substances present in the fibrotic microenvironment including pathogen associated molecular patterns (PAMPs) derived from invading or commensal microbes, and danger associated molecular patterns (DAMPs) derived from injured cells and tissues will be discussed along with the proposed contribution of innate immune populations such as macrophages, neutrophils, fibrocytes, myeloid suppressor cells, and innate lymphoid cells. Each component will be considered in the context of its relationship to environmental and genetic factors, disease outcomes, and potential therapies. We conclude with discussion of unanswered questions and opportunities for future study in this area.

ETIOLOGY AND PATHOGENESIS OF HYPOPHARYNX CANCER: GENETIC AND IMMUNOLOGICAL FACTORS OF DEVELOPMENT. Review

Relevance. In the modern oncology hypopharynx malignant tumors are one of the urgent and significant problems. Hypopharynx is one of the most frequent localizations in the head and neck. An important factor causing the high occurrence in the population is the asymptomatic course of the disease, resulting in patients presenting for treatment with аn already widespread tumour process. Objective: to summarize and systematize data on the etiology and pathogenesis of hypopharynx cancer. Materials and methods. Analysis of scientific publications in the international electronic scientometric databases Scopus, PubMed by keywords. Search depth – 20 years (2001-2020). Results. In recent years, the view on the mechanisms of the development of carcinogenesis has changed dramatically, the tumour is no longer considered as a mass of malignant cells, but rather as a self-sufficient biological structure with a complex microenvironment in which other subpopulations of cells damaged by cancer are involved. The stromal component of the tumour microenvironment consists of various types of cells such as cancer-associated fibroblasts, neutrophils, macrophages, regulatory T-cells, myeloid suppressor cells, NK-cells etc. These subpopulations of cells interact with each other as well as with cancer cells. In addition to amplification, deletion, loss of heterozygosity, as well as polymorphism of some genes that are directly involved in the cell cycle or act as regulators of posttranscriptional modifiers of their products at the early stages of carcinogenesis may be one of the promising directions in creating a panel of markers for the risk of developing hypopharynx cancer. Conclusions. The microenvironment of the tumor consists of many different cell populations. These parts of the surrounding stroma can function as both positive and negative regulators of all signs of cancer, including evasion of apoptosis, induction of angiogenesis, deregulation of energy metabolism, resistance to detection and destruction by the immune system, and activation of invasion and metastasis. Exploring differences in the composition of the tumour microenvironment and their influence on the development and progression of hypopharynx cancer can help better understand mechanisms underlying different responses to therapy, and help to identify possible targets for clinical intervention.

OMIC-11. SINGLE CELL RNA SEQUENCING FROM THE CSF OF SUBJECTS WITH H3K27M+ DIPG/DMG TREATED WITH GD2 CAR T-CELLULAR THERAPY

Introduction We are conducting a Phase I clinical trial utilizing chimeric antigen receptor (CAR) T-cells targeting GD2 (NCT04196413) for H3K27M-mutant diffuse intrinsic pontine glioma (DIPG) and spinal cord diffuse midline glioma (DMG). Cerebrospinal fluid (CSF) is collected for correlative studies at the time of routine intracranial pressure monitoring via Ommaya catheter. Here we present single cell RNA-sequencing results from the first 3 subjects. Methods Single cell RNA-sequencing was performed utilizing 10X Genomics on cells isolated from CSF at various time points before and after CAR T-cell administration and on the CAR T-cell product. Output was aligned with Cell Ranger and analyzed in R. Results As detailed in the Majzner et al. abstract presented at this meeting, three of four subjects treated at dose-level one exhibited clear radiographic and/or clinical benefit. We have to date completed single cell RNA-sequencing for three of these four subjects (two with benefit, one without). After filtering out low-quality signals and doublets, 89,604 cells across 3 subjects were analyzed. Of these, 4,122 cells represent cells isolated from CSF and 85,482 cells represent CAR T-cell product. Two subjects who demonstrated clear clinical and radiographic improvement exhibited fewer S100A8+S100A9+ myeloid suppressor-cells and CD25+FOXP3+ regulatory T-cells in the CSF pre-infusion compared to the subject who did not derive a therapeutic response. In one subject with DIPG who demonstrated improvement, polyclonal CAR T-cells detectable in CSF at Day +14 demonstrated enrichment of CD8A, GZMA, GNLY and PDCD1 compared to the pre-infusion CAR T-cells by trajectory analysis, suggesting differentiation toward a cytotoxic phenotype; the same subject exhibited increasing numbers of S100A8+S100A9+ myeloid cells and CX3CR1+P2RY12+ microglia over time. Further analyses will be presented as data become available. Conclusions The presence of immunosuppressive myeloid populations, detectable in CSF, may correlate to clinical response in CAR T cell therapy for DIPG/DMG.