An immunogenetic basis for lung cancer risk

Cancer risk is influenced by inherited mutations, DNA replication errors, and environmental factors. However, the influence of genetic variation in immunosurveillance on cancer risk is not well understood. Leveraging population-level data from the UK Biobank and FinnGen, we show that heterozygosity at the human leukocyte antigen (HLA)-II loci is associated with reduced lung cancer risk in smokers. Fine-mapping implicated amino acid heterozygosity in the HLA-II peptide binding groove in reduced lung cancer risk, and single-cell analyses showed that smoking drives enrichment of proinflammatory lung macrophages and HLA-II+ epithelial cells. In lung cancer, widespread loss of HLA-II heterozygosity (LOH) favored loss of alleles with larger neopeptide repertoires. Thus, our findings nominate genetic variation in immunosurveillance as a critical risk factor for lung cancer.

Functional impairment of "helpless" CD8 + memory T cells is transient and driven by prolonged but finite cognate antigen presentation

Generation of functional CD8 + T cell memory typically requires engagement of CD4 + T cells. However, in certain scenarios, such as acutely-resolving viral infections, effector (T E ) and subsequent memory (T M ) CD8 + T cell formation appear impervious to a lack of CD4 + T cell help during priming. Nonetheless, such "helpless" CD8 + T M respond poorly to pathogen rechallenge. At present, the origin and long-term evolution of helpless CD8 + T cell memory remain incompletely understood. Here, we demonstrate that helpless CD8 + T E differentiation is largely normal but a multiplicity of helpless CD8 T M defects, consistent with impaired memory maturation, emerge as a consequence of prolonged yet finite exposure to cognate antigen. Importantly, these defects resolve over time leading to full restoration of CD8 + T M potential and recall capacity. Our findings provide a unified explanation for helpless CD8 + T cell memory and emphasize an unexpected CD8 + T M plasticity with implications for vaccination strategies and beyond.

An IL-4 signalling axis in bone marrow drives pro-tumorigenic myelopoiesis

Myeloid cells are known to suppress antitumour immunity1. However, the molecular drivers of immunosuppressive myeloid cell states are not well defined. Here we used single-cell RNA sequencing of human and mouse non-small cell lung cancer (NSCLC) lesions, and found that in both species the type 2 cytokine interleukin-4 (IL-4) was predicted to be the primary driver of the tumour-infiltrating monocyte-derived macrophage phenotype. Using a panel of conditional knockout mice, we found that only deletion of the IL-4 receptor IL-4Rα in early myeloid progenitors in bone marrow reduced tumour burden, whereas deletion of IL-4Rα in downstream mature myeloid cells had no effect. Mechanistically, IL-4 derived from bone marrow basophils and eosinophils acted on granulocyte-monocyte progenitors to transcriptionally programme the development of immunosuppressive tumour-promoting myeloid cells. Consequentially, depletion of basophils profoundly reduced tumour burden and normalized myelopoiesis. We subsequently initiated a clinical trial of the IL-4Rα blocking antibody dupilumab2-5 given in conjunction with PD-1/PD-L1 checkpoint blockade in patients with relapsed or refractory NSCLC who had progressed on PD-1/PD-L1 blockade alone (ClinicalTrials.gov identifier NCT05013450 ). Dupilumab supplementation reduced circulating monocytes, expanded tumour-infiltrating CD8 T cells, and in one out of six patients, drove a near-complete clinical response two months after treatment. Our study defines a central role for IL-4 in controlling immunosuppressive myelopoiesis in cancer, identifies a novel combination therapy for immune checkpoint blockade in humans, and highlights cancer as a systemic malady that requires therapeutic strategies beyond the primary disease site.

Interleukin-3 coordinates glial-peripheral immune crosstalk to incite multiple sclerosis

Glial cells and central nervous system (CNS)-infiltrating leukocytes contribute to multiple sclerosis (MS). However, the networks that govern crosstalk among these ontologically distinct populations remain unclear. Here, we show that, in mice and humans, CNS-resident astrocytes and infiltrating CD44hiCD4+ T cells generated interleukin-3 (IL-3), while microglia and recruited myeloid cells expressed interleukin-3 receptor-ɑ (IL-3Rɑ). Astrocytic and T cell IL-3 elicited an immune migratory and chemotactic program by IL-3Rɑ+ myeloid cells that enhanced CNS immune cell infiltration, exacerbating MS and its preclinical model. Multiregional snRNA-seq of human CNS tissue revealed the appearance of IL3RA-expressing myeloid cells with chemotactic programming in MS plaques. IL3RA expression by plaque myeloid cells and IL-3 amount in the cerebrospinal fluid predicted myeloid and T cell abundance in the CNS and correlated with MS severity. Our findings establish IL-3:IL-3RA as a glial-peripheral immune network that prompts immune cell recruitment to the CNS and worsens MS.

Monocytes re-enter the bone marrow during fasting and alter the host response to infection

Diet profoundly influences physiology. Whereas over-nutrition elevates risk for disease via its influence on immunity and metabolism, caloric restriction and fasting appear to be salutogenic. Despite multiple correlations observed between diet and health, the underlying biology remains unclear. Here, we identified a fasting-induced switch in leukocyte migration that prolongs monocyte lifespan and alters susceptibility to disease in mice. We show that fasting during the active phase induced the rapid return of monocytes from the blood to the bone marrow. Monocyte re-entry was orchestrated by hypothalamic-pituitary-adrenal (HPA) axis-dependent release of corticosterone, which augmented the CXCR4 chemokine receptor. Although the marrow is a safe haven for monocytes during nutrient scarcity, re-feeding prompted mobilization culminating in monocytosis of chronologically older and transcriptionally distinct monocytes. These shifts altered response to infection. Our study shows that diet-in particular, a diet's temporal dynamic balance-modulates monocyte lifespan with consequences for adaptation to external stressors.

Spatial CRISPR genomics identifies regulators of the tumor microenvironment

While CRISPR screens are helping uncover genes regulating many cell-intrinsic processes, existing approaches are suboptimal for identifying extracellular gene functions, particularly in the tissue context. Here, we developed an approach for spatial functional genomics called Perturb-map. We applied Perturb-map to knock out dozens of genes in parallel in a mouse model of lung cancer and simultaneously assessed how each knockout influenced tumor growth, histopathology, and immune composition. Moreover, we paired Perturb-map and spatial transcriptomics for unbiased analysis of CRISPR-edited tumors. We found that in Tgfbr2 knockout tumors, the tumor microenvironment (TME) was converted to a fibro-mucinous state, and T cells excluded, concomitant with upregulated TGFβ and TGFβ-mediated fibroblast activation, indicating that TGFβ-receptor loss on cancer cells increased TGFβ bioavailability and its immunosuppressive effects on the TME. These studies establish Perturb-map for functional genomics within the tissue at single-cell resolution with spatial architecture preserved and provide insight into how TGFβ responsiveness of cancer cells can affect the TME.

Lynch Syndrome and MSI-H Cancers: From Mechanisms to "Off-The-Shelf" Cancer Vaccines

Defective DNA mismatch repair (dMMR) is associated with many cancer types including colon, gastric, endometrial, ovarian, hepatobiliary tract, urinary tract, brain and skin cancers. Lynch syndrome - a hereditary cause of dMMR - confers increased lifetime risk of malignancy in different organs and tissues. These Lynch syndrome pathogenic alleles are widely present in humans at a 1:320 population frequency of a single allele and associated with an up to 80% risk of developing microsatellite unstable cancer (microsatellite instability - high, or MSI-H). Advanced MSI-H tumors can be effectively treated with checkpoint inhibitors (CPI), however, that has led to response rates of only 30-60% despite their high tumor mutational burden and favorable immune gene signatures in the tumor microenvironment (TME). We and others have characterized a subset of MSI-H associated highly recurrent frameshift mutations that yield shared immunogenic neoantigens. These frameshifts might serve as targets for off-the-shelf cancer vaccine designs. In this review we discuss the current state of research around MSI-H cancer vaccine development, its application to MSI-H and Lynch syndrome cancer patients and the utility of MSI-H as a biomarker for CPI therapy. We also summarize the tumor intrinsic mechanisms underlying the high occurrence rates of certain frameshifts in MSI-H. Finally, we provide an overview of pivotal clinical trials investigating MSI-H as a biomarker for CPI therapy and MSI-H vaccines. Overall, this review aims to inform the development of novel research paradigms and therapeutics.

HNRNPM controls circRNA biogenesis and splicing fidelity to sustain cancer cell fitness

High spliceosome activity is a dependency for cancer cells, making them more vulnerable to perturbation of the splicing machinery compared to normal cells. To identify splicing factors important for prostate cancer (PCa) fitness, we performed pooled shRNA screens in vitro and in vivo. Our screens identified heterogeneous nuclear ribonucleoprotein M (HNRNPM) as a regulator of PCa cell growth. RNA- and eCLIP-sequencing identified HNRNPM binding to transcripts of key homeostatic genes. HNRNPM binding to its targets prevents aberrant exon inclusion and backsplicing events. In both linear and circular mis-spliced transcripts, HNRNPM preferentially binds to GU-rich elements in long flanking proximal introns. Mimicry of HNRNPM-dependent linear-splicing events using splice-switching-antisense-oligonucleotides was sufficient to inhibit PCa cell growth. This suggests that PCa dependence on HNRNPM is likely a result of mis-splicing of key homeostatic coding and non-coding genes. Our results have further been confirmed in other solid tumors. Taken together, our data reveal a role for HNRNPM in supporting cancer cell fitness. Inhibition of HNRNPM activity is therefore a potential therapeutic strategy in suppressing growth of PCa and other solid tumors.

Shared Immunogenic Poly-Epitope Frameshift Mutations in Microsatellite Unstable Tumors

Microsatellite instability-high (MSI-H) tumors are characterized by high tumor mutation burden and responsiveness to checkpoint blockade. We identified tumor-specific frameshifts encoding multiple epitopes that originated from indel mutations shared among patients with MSI-H endometrial, colorectal, and stomach cancers. Epitopes derived from these shared frameshifts have high population occurrence rates, wide presence in many tumor subclones, and are predicted to bind to the most frequent MHC alleles in MSI-H patient cohorts. Neoantigens arising from these mutations are distinctly unlike self and viral antigens, signifying novel groups of potentially highly immunogenic tumor antigens. We further confirmed the immunogenicity of frameshift peptides in T cell stimulation experiments using blood mononuclear cells isolated from both healthy donors and MSI-H cancer patients. Our study uncovers the widespread occurrence and strong immunogenicity of tumor-specific antigens derived from shared frameshift mutations in MSI-H cancer and Lynch syndrome patients, suitable for the design of common "off-the-shelf" cancer vaccines.

Abstract 5587: Characterization of shared immunogenic frameshift mutations in microsatellite unstable cancers to guide the design of off-the-shelf immunotherapies

Microsatellite instability-high (MSI-H) cancers are an important model for evaluating neoantigen-based immunotherapies, given their high loads of tumor-specific antigens, evidence of T cell infiltration and exceptional response rates to checkpoint blockade. Importantly, MSI-H tumors are enriched in short nucleotide insertion/deletions in microsatellite regions (“hot spots”) within open reading frames, potentially leading to frameshift mutations shared across patients with MSI-H tumors and Lynch Syndrome, a hereditary cancer predisposition syndrome with MSI-H phenotype. We hypothesized that MSI-H tumors are enriched in recurrent frameshift mutations encoding immunogenic neoantigens and pre-selection of an optimal set of recurrent frameshift mutations, based on the multiplicity of encoded neoepitopes, diversity of interaction with common major histocompatibility complex (MHC) alleles and immunogenicity, will inform the design of off-the-shelf immune therapies for patients with MSI-H phenotype. Utilizing the whole-exome sequencing information available at The Cancer Genome Atlas, we evaluated the neoantigen profiles of patients with colorectal (n=461), stomach (n=443) and endometrial carcinoma (n=560) (COAD, STAD and UCEC, respectively) according to the aforementioned criteria and identified 37, 23 and 9 frameshift mutations encoding potentially immunogenic neoantigens, which were shared across the MSI-H population in COAD, STAD and UCEC, respectively. In an array of immunological assays utilizing peripheral blood mononuclear cells (PBMCs) from healthy donors, we characterized the immunogenicity of the neoantigens derived from the 9 frameshift peptides shared in MSI-H UCEC to assess the extent and specificity of the engendered T cell immunity. We found that each frameshift peptide could elicit antigen-specific CD8+ T cell responses in a subset of subjects tested, which suggests that MSI-H UCEC patients have an increased frequency of high-quality T cell epitopes derived from shared frameshift peptides, binding to a broad spectrum of MHC alleles, capable of inducing CD8+ T responses. Currently, utilizing blood and tissue specimens from patients with MSI-H COAD, STAD and UCEC, we are interrogating (1) the expression levels and frequencies of the selected shared neoantigens, (2) whether these neoantigens are presented in the context of MHC and (3) can elicit endogenous T cell responses. Findings from this research will guide the selection of shared neoantigens eliciting antitumor T cell immunity in patients with MSI-H tumors and will ultimately lay the foundation for common neoantigen-based, off-the-shelf cancer immunotherapy designs, which can be utilized in therapeutic and preventative settings in MSI-H cancers and Lynch Syndrome, respectively.

Citation Format: Cansu Cimen Bozkus, Vladimir Roudko, Theofani Orfanelli, Stephanie Blank, Benjamin Greenbaum, Nina Bhardwaj. Characterization of shared immunogenic frameshift mutations in microsatellite unstable cancers to guide the design of off-the-shelf immunotherapies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5587.

Hybrid Gene Origination Creates Human-Virus Chimeric Proteins during Infection

RNA viruses are a major human health threat. The life cycles of many highly pathogenic RNA viruses like influenza A virus (IAV) and Lassa virus depends on host mRNA, because viral polymerases cleave 5'-m7G-capped host transcripts to prime viral mRNA synthesis ("cap-snatching"). We hypothesized that start codons within cap-snatched host transcripts could generate chimeric human-viral mRNAs with coding potential. We report the existence of this mechanism of gene origination, which we named "start-snatching." Depending on the reading frame, start-snatching allows the translation of host and viral "untranslated regions" (UTRs) to create N-terminally extended viral proteins or entirely novel polypeptides by genetic overprinting. We show that both types of chimeric proteins are made in IAV-infected cells, generate T cell responses, and contribute to virulence. Our results indicate that during infection with IAV, and likely a multitude of other human, animal and plant viruses, a host-dependent mechanism allows the genesis of hybrid genes.

Computational Prediction and Validation of Tumor-Associated Neoantigens

Tumor progression is typically accompanied by an accumulation of driver and passenger somatic mutations. A handful of those mutations occur in protein coding genes which introduce non-synonymous polymorphisms. Certain substitutions may give rise to novel, tumor-associated antigens or neoantigens, presentable by cancer cells to the host adaptive immune system. As antigen recognition is the core of an effective immune response, the identification of patient tumor specific antigens derived from transformed cells is of importance for immunotherapeutic approaches. Recent technological advances in DNA sequencing of tumor genomes, advances in gene expression analysis, algorithm development for antigen predictions and methods for T-cell receptor (TCR) repertoire sequencing have facilitated the selection of candidate immunogenic neoantigens. In this regard, multiple research groups have reported encouraging results of neoantigen-based cancer vaccines that generate tumor antigen specific immune responses, both in mouse models and clinical trials. Additionally, both the quantity and quality of neoantigens has been shown to have predictive value for clinical outcomes in checkpoint-blockade immunotherapy in certain tumor types. Neoantigen recognition by vaccination or through adoptive T cell therapy may have unprecedented potential to advance cancer immunotherapy in combination with other approaches. In our review we discuss three parameters regarding neoantigens: computational methods for epitope prediction, experimental methods for epitope immunogenicity validation and future directions for improvement of those methods. Within each section, we will describe the advantages and limitations of existing methods as well as highlight pressing fundamental problems to be addressed.

Immune Checkpoint Blockade Enhances Shared Neoantigen-Induced T-cell Immunity Directed against Mutated Calreticulin in Myeloproliferative Neoplasms

Somatic frameshift mutations in the calreticulin (CALR) gene are key drivers of cellular transformation in myeloproliferative neoplasms (MPN). All patients carrying these mutations (CALR ⁺ MPN) share an identical sequence in the C-terminus of the mutated CALR protein (mut-CALR), with the potential for utility as a shared neoantigen. Here, we demonstrate that although a subset of patients with CALR ⁺ MPN develop specific T-cell responses against the mut-CALR C-terminus, PD-1 or CTLA4 expression abrogates the full complement of responses. Significantly, blockade of PD-1 and CLTA4 ex vivo by mAbs and of PD-1 in vivo by pembrolizumab administration restores mut-CALR-specific T-cell immunity in some patients with CALR ⁺ MPN. Moreover, mut-CALR elicits antigen-specific responses from both CD4⁺ and CD8⁺ T cells, confirming its broad applicability as an immunogen. Collectively, these results establish mut-CALR as a shared, MPN-specific neoantigen and inform the design of novel immunotherapies targeting mut-CALR. SIGNIFICANCE: Current treatment modalities for MPN are not effective in eliminating malignant cells. Here, we show that mutations in the CALR gene, which drive transformation in MPN, elicit T-cell responses that can be further enhanced by checkpoint blockade, suggesting immunotherapies could be employed to eliminate CALR ⁺ malignant cells in MPN.This article is highlighted in the In This Issue feature, p. 1143.

Natural Adjuvants for in situ Vaccination Lymphoma Immunotherapy

BACKGROUND

In situ vaccination (ISV) against lymphoma can be achieved with Flt3-ligand treatment to recruit dendritic cells (DC), radiotherapy to load DC with tumor antigens, and intratumoral injection of a pattern-recognition- receptor agonist (PRRa) to activate antigen-loaded DC. While clinical trials of ISV using synthetic PRRa have yielded remissions, the optimal approach to activate DC is unknown. We hypothesize that ‘natural’ PRRa, such as the attenuated pathogens in common prophylactic vaccines, could target multiple PRR, leading to more robust activation of DC as compared to synthetic PRRa.

METHODS

20 FDA-approved vaccines (BCG, MMR, etc.) were screened in vitro, for their effect on DC phenotype and function. DC tumor antigen cross-presentation was assessed using CRISPR gene-edited β2m−/−GFP-lymphoma cells and a GFP-specific CD8 T cell system. Mechanisms of immune activation were interrogated using MyD88, TRIF, MAVS, and IFNAR knockout mice, as well as a library of CRISPR-edited PRR-null Raw264 macrophages. Potent vaccines functioning through distinct mechanisms were evaluated in vivo in an ISV using the A20 murine lymphoma model.

RESULTS

Several vaccines induced robust DC activation, cross-presentation and increases in T cell activation, proliferation, and tumor killing. Some vaccines were more effective than synthetic PRRa in activating DCs to induce a T cell response. Distinct PRR and signaling pathways were engaged by different vaccines. In vivo, vaccine combination therapy induced tumor regression in a majority of animals.

CONCLUSIONS

Prophylactic vaccines, used alone or in combination, are effective DC activators and can be repurposed for use in ISV, with immediate translation into the clinic.

Abstract B072: Immune checkpoint blockade enhances mutated calreticulin-induced T-cell immunity in myeloproliferative neoplasms

Somatic mutations in the CALR gene are key drivers of cellular transformation in myeloproliferative neoplasms (MPN) and are the second most common driver mutations in essential thrombocythemia (ET) and myelofibrosis (MF) patients. CALR mutations are 1-bp frameshift mutations that result in the formation of a novel C-terminus with an identical 36-amino acid (aa) sequence that is shared by all CALR+ MPN patients. We hypothesized that the recurrence and uniformity of the novel C-terminus mark the mutated (mut)-CALR an attractive candidate as an MPN-specific tumor neoantigen that might elicit anti-tumor immune responses across patients who express this mutation. To assess the immunogenicity of mut-CALR neopeptide, we interrogated the binding affinity of epitopes from the altered C-terminus using in silico peptide binding prediction algorithms. The analysis showed that multiple epitopes could bind to class I and II human leukocyte antigens (HLA). We investigated whether we could elicit T-cell responses against mut-CALR neopeptide from CALR+ MPN patients. Peripheral blood mononuclear cells (PBMCs) from 18 MPN patients with ET (7), MF (4) or MF arising from ET (7) were stimulated in vitro with pooled overlapping long peptides (OLPs; 14-15 aa) spanning the mutated or wild type (WT) CALR C-terminus and T-cell responses were assessed by enzyme-linked immunospot assay (ELISPOT). There was a significant increase in interferon (IFN)-γ production upon stimulation with mut-CALR OLPs, whereas the corresponding WT sequence did not induce a T-cell response. Next, we evaluated whether mut-CALR-specific T-cells were undergoing exhaustion. Examination of the expression of checkpoint receptors on T-cells ex vivo determined that T-cells from peripheral blood of CALR+ MPN patients exhibited increased expression of multiple cell surface inhibitory molecules compared to healthy donor T-cells, including programmed cell death (PD)-1 and cytotoxic T lymphocyte-associated antigen (CTLA)-4. In order to address whether PD-1 and CTLA-4 overexpression suppressed mut-CALR-specific T-cell responses in CALR+ MPN patients, PD-1 or CTLA-4 signaling on T-cells was blocked through addition of monoclonal blocking antibodies. T-cell responses against mut-CALR peptides were recovered in 3 CALR+ MPN patients that were previously nonresponsive to mut-CALR stimulation. To gain further insights into checkpoint receptor-mediated T-cell suppression in CALR+ MPN patients, we investigated mut-CALR-specific T-cell responses in a CALR+ MPN patient receiving PD-1 inhibitor pembrolizumab, in our ongoing clinical trial (NCT03065400). We monitored the changes in the frequencies of peripheral blood T-cells in this patient before and after pembrolizumab treatment by both flow cytometry and T-cell receptor (TCR) sequencing. Prior to therapy, this patient had low proportion of T-cells (4.33% of PBMCs) and 32.3% of the T-cells expressed PD-1. After 2 cycles of pembrolizumab, the T-cell proportion greatly increased (26% of PBMCs) and remained high when measured after 6 cycles (18% of PBMCs). Sequencing of TCR Vβ chains of peripheral blood T-cells revealed that T-cells exhibited greater clonality after pembrolizumab treatment. Furthermore, we evaluated changes in mut-CALR-specific T-cell responses in this CALR+ MPN patient prior to and during pembrolizumab administration. At baseline, peripheral blood T-cells from this patient did not respond to stimulation with mut-CALR peptides. After pembrolizumab treatment, however, mut-CALR-specific T-cell responses were evident, as shown by increased IFN-γ production. Together, these results establish mut-CALR as a novel MPN-specific tumor shared-neoantigen and provide a strong rationale to study its immunogenic properties to inform the design of novel immunotherapies targeting mut-CALR in MPN patients carrying the mutation.

Citation Format: Cansu Cimen Bozkus, Vladimir Roudko, John P. Finnigan, John Mascarenhas, Ronald Hoffman, Camelia Iancu-Rubin, Nina Bhardwaj. Immune checkpoint blockade enhances mutated calreticulin-induced T-cell immunity in myeloproliferative neoplasms [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B072.

Therapeutic Immune Modulation against Solid Cancers with Intratumoral Poly-ICLC: A Pilot Trial

Purpose: Polyinosinic-polycytidylic acid-poly-l-lysine carboxymethylcellulose (poly-ICLC), a synthetic double-stranded RNA complex, is a ligand for toll-like receptor-3 and MDA-5 that can activate immune cells, such as dendritic cells, and trigger natural killer cells to kill tumor cells.Patients and Methods: In this pilot study, eligible patients included those with recurrent metastatic disease in whom prior systemic therapy (head and neck squamous cell cancer and melanoma) failed. Patients received 2 treatment cycles, each cycle consisting of 1 mg poly-ICLC 3× weekly intratumorally (IT) for 2 weeks followed by intramuscular (IM) boosters biweekly for 7 weeks, with a 1-week rest period. Immune response was evaluated by immunohistochemistry (IHC) and RNA sequencing (RNA-seq) in tumor and blood.Results: Two patients completed 2 cycles of IT treatments, and 1 achieved clinical benefit (stable disease, progression-free survival 6 months), whereas the remainder had progressive disease. Poly-ICLC was well tolerated, with principal side effects of fatigue and inflammation at injection site (<grade 2). In the patient with clinical benefit, IHC analysis of tumor showed increased CD4, CD8, PD1, and PD-L1 levels compared with patients with progressive disease. RNA-seq analysis of the same patient's tumor and peripheral blood mononuclear cells showed dramatic changes in response to poly-ICLC treatment, including upregulation of genes associated with chemokine activity, T-cell activation, and antigen presentation.Conclusions: Poly-ICLC was well tolerated in patients with solid cancer and generated local and systemic immune responses, as evident in the patient achieving clinical benefit. These results warrant further investigation and are currently being explored in a multicenter phase II clinical trial (NCT02423863). Clin Cancer Res; 24(20); 4937-48. ©2018 AACR.