Fibrinogen-like Protein 1 Is a Major Immune Inhibitory Ligand of LAG-3.

Lymphocyte-activation gene 3 (LAG-3) is an immune inhibitory receptor, with major histocompatibility complex class II (MHC-II) as a canonical ligand. However, it remains controversial whether MHC-II is solely responsible for the inhibitory function of LAG-3. Here, we demonstrate that fibrinogen-like protein 1 (FGL1), a liver-secreted protein, is a major LAG-3 functional ligand independent from MHC-II. FGL1 inhibits antigen-specific T cell activation, and ablation of FGL1 in mice promotes T cell immunity. Blockade of the FGL1-LAG-3 interaction by monoclonal antibodies stimulates tumor immunity and is therapeutic against established mouse tumors in a receptor-ligand inter-dependent manner. FGL1 is highly produced by human cancer cells, and elevated FGL1 in the plasma of cancer patients is associated with a poor prognosis and resistance to anti-PD-1/B7-H1 therapy. Our findings reveal an immune evasion mechanism and have implications for the design of cancer immunotherapy.

A Paradigm Shift in Cancer Immunotherapy: From Enhancement to Normalization.

Harnessing an antitumor immune response has been a fundamental strategy in cancer immunotherapy. For over a century, efforts have primarily focused on amplifying immune activation mechanisms that are employed by humans to eliminate invaders such as viruses and bacteria. This "immune enhancement" strategy often results in rare objective responses and frequent immune-related adverse events (irAEs). However, in the last decade, cancer immunotherapies targeting the B7-H1/PD-1 pathway (anti-PD therapy), have achieved higher objective response rates in patients with much fewer irAEs. This more beneficial tumor response-to-toxicity profile stems from distinct mechanisms of action that restore tumor-induced immune deficiency selectively in the tumor microenvironment, here termed "immune normalization," which has led to its FDA approval in more than 10 cancer indications and facilitated its combination with different therapies. In this article, we wish to highlight the principles of immune normalization and learn from it, with the ultimate goal to guide better designs for future cancer immunotherapies.

CXCR1 and CXCR2 Chemokine Receptor Agonists Produced by Tumors Induce Neutrophil Extracellular Traps that Interfere with Immune Cytotoxicity.

Neutrophils are expanded and abundant in cancer-bearing hosts. Under the influence of CXCR1 and CXCR2 chemokine receptor agonists and other chemotactic factors produced by tumors, neutrophils, and granulocytic myeloid-derived suppressor cells (MDSCs) from cancer patients extrude their neutrophil extracellular traps (NETs). In our hands, CXCR1 and CXCR2 agonists proved to be the major mediators of cancer-promoted NETosis. NETs wrap and coat tumor cells and shield them from cytotoxicity, as mediated by CD8+ T cells and natural killer (NK) cells, by obstructing contact between immune cells and the surrounding target cells. Tumor cells protected from cytotoxicity by NETs underlie successful cancer metastases in mice and the immunotherapeutic synergy of protein arginine deiminase 4 (PAD4) inhibitors, which curtail NETosis with immune checkpoint inhibitors. Intravital microscopy provides evidence of neutrophil NETs interfering cytolytic cytotoxic T lymphocytes (CTLs) and NK cell contacts with tumor cells.

IL-18BP is a secreted immune checkpoint and barrier to IL-18 immunotherapy.

Cytokines were the first modern immunotherapies to produce durable responses in patients with advanced cancer, but they have only modest efficacy and limited tolerability1,2. In an effort to identify alternative cytokine pathways for immunotherapy, we found that components of the interleukin-18 (IL-18) pathway are upregulated on tumour-infiltrating lymphocytes, suggesting that IL-18 therapy could enhance anti-tumour immunity. However, recombinant IL-18 previously did not demonstrate efficacy in clinical trials3. Here we show that IL-18BP, a high-affinity IL-18 decoy receptor, is frequently upregulated in diverse human and mouse tumours and limits the anti-tumour activity of IL-18 in mice. Using directed evolution, we engineered a 'decoy-resistant' IL-18 (DR-18) that maintains signalling potential but is impervious to inhibition by IL-18BP. Unlike wild-type IL-18, DR-18 exerted potent anti-tumour effects in mouse tumour models by promoting the development of poly-functional effector CD8+ T cells, decreasing the prevalence of exhausted CD8+ T cells that express the transcriptional regulator of exhaustion TOX, and expanding the pool of stem-like TCF1+ precursor CD8+ T cells. DR-18 also enhanced the activity and maturation of natural killer cells to effectively treat anti-PD-1 resistant tumours that have lost surface expression of major histocompatibility complex class I molecules. These results highlight the potential of the IL-18 pathway for immunotherapeutic intervention and implicate IL-18BP as a major therapeutic barrier.

Antitumor efficacy and reduced toxicity using an anti-CD137 Probody therapeutic.

Costimulation via CD137 (4-1BB) enhances antitumor immunity mediated by cytotoxic T lymphocytes. Anti-CD137 agonist antibodies elicit mild liver inflammation in mice, and the maximum tolerated dose of Urelumab, an anti-human CD137 agonist monoclonal antibody, in the clinic was defined by liver inflammation-related side effects. A protease-activated prodrug form of the anti-mouse CD137 agonist antibody 1D8 (1D8 Probody therapeutic, Pb-Tx) was constructed and found to be selectively activated in the tumor microenvironment. This construct, which encompasses a protease-cleavable linker holding in place a peptide that masks the antigen binding site, exerted antitumor effects comparable to the unmodified antibody but did not result in liver inflammation. Moreover, it efficaciously synergized with both PD-1 blockade and adoptive T-cell therapy. Surprisingly, minimal active Pb-Tx reached tumor-draining lymph nodes, and regional lymphadenectomy did not abrogate antitumor efficacy. By contrast, S1P receptor-dependent recirculation of T cells was absolutely required for efficacy. The preferential cleavage of the anti-CD137 Pb-Tx by tumor proteases offers multiple therapeutic opportunities, including neoadjuvant therapy, as shown by experiments in which the Pb-Tx is given prior to surgery to avoid spontaneous metastases.

Differential Interleukin-8 thresholds for chemotaxis and netosis in human neutrophils.

In humans, IL-8 (CXCL8) is a key chemokine for chemotaxis of polymorphonuclear leukocytes and monocytes/macrophages when acting on CXCR1 and CXCR2. CXCL8 activity on neutrophils includes chemotaxis and eliciting the extrusion of neutrophil extracellular traps (NETs). In this study, we show that concentrations of IL-8 that induce NETosis surpass in at least one order of magnitude those required to elicit chemoattraction in human neutrophils. IL-8-induced NETosis was less dependent on G-proteins than migration, while extracellular Ca+2 chelation similarly inhibited both processes. Reactive oxygen species (ROS) were more important for NETosis than for chemotaxis as evidenced by neutralization with N-acetyl -cysteine. Interestingly, selective blockade with anti-CXCR1 mAb inhibited NETosis much more readily than chemotaxis, while pharmacological inhibition of both CXCR1 and CXCR2, or selective inhibition for CXCR2 alone, similarly inhibited both functions. Together, these results propose a model according to which low concentrations of IL-8 in a gradient attract neutrophils to the inflammatory foci, while high receptor-saturating concentrations of IL-8 give rise to NETosis once leukocytes reach the core of the inflammatory insult.

Heterogenous presence of neutrophil extracellular traps in human solid tumours is partially dependent on IL-8.

Neutrophil extracellular traps (NETs) are webs of extracellular nuclear DNA extruded by dying neutrophils infiltrating tissue. NETs constitute a defence mechanism to entrap and kill fungi and bacteria. Tumours induce the formation of NETs to the advantage of the malignancy via a variety of mechanisms shown in mouse models. Here, we investigated the presence of NETs in a variety of human solid tumours and their association with IL-8 (CXCL8) protein expression and CD8+ T-cell density in the tumour microenvironment. Multiplex immunofluorescence panels were developed to identify NETs in human cancer tissues by co-staining with the granulocyte marker CD15, the neutrophil marker myeloperoxidase and citrullinated histone H3 (H3Cit), as well as IL-8 protein and CD8+ T cells. Three ELISA methods to detect and quantify circulating NETs in serum were optimised and utilised. Whole tumour sections and tissue microarrays from patients with non-small cell lung cancer (NSCLC; n = 14), bladder cancer (n = 14), melanoma (n = 11), breast cancer (n = 31), colorectal cancer (n = 20) and mesothelioma (n = 61) were studied. Also, serum samples collected retrospectively from patients with metastatic melanoma (n = 12) and NSCLC (n = 34) were ELISA assayed to quantify circulating NETs and IL-8. NETs were detected in six different human cancer types with wide individual variation in terms of tissue density and distribution. At least in NSCLC, bladder cancer and metastatic melanoma, NET density positively correlated with IL-8 protein expression and inversely correlated with CD8+ T-cell densities. In a series of serum samples from melanoma and NSCLC patients, a positive correlation between circulating NETs and IL-8 was found. In conclusion, NETs are detectable in formalin-fixed human biopsy samples from solid tumours and in the circulation of cancer patients with a considerable degree of individual variation. NETs show a positive association with IL-8 and a trend towards a negative association with CD8+ tumour-infiltrating lymphocytes. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Single-cell characterization of a model of poly I:C-stimulated peripheral blood mononuclear cells in severe asthma.

BACKGROUND: Asthma has been associated with impaired interferon response. Multiple cell types have been implicated in such response impairment and may be responsible for asthma immunopathology. However, existing models to study the immune response in asthma are limited by bulk profiling of cells. Our objective was to Characterize a model of peripheral blood mononuclear cells (PBMCs) of patients with severe asthma (SA) and its response to the TLR3 agonist Poly I:C using two single-cell methods. METHODS: Two complementary single-cell methods, DropSeq for single-cell RNA sequencing (scRNA-Seq) and mass cytometry (CyTOF), were used to profile PBMCs of SA patients and healthy controls (HC). Poly I:C-stimulated and unstimulated cells were analyzed in this study. RESULTS: PBMCs (n = 9414) from five SA (n = 6099) and three HC (n = 3315) were profiled using scRNA-Seq. Six main cell subsets, namely CD4 + T cells, CD8 + T cells, natural killer (NK) cells, B cells, dendritic cells (DCs), and monocytes, were identified. CD4 + T cells were the main cell type in SA and demonstrated a pro-inflammatory profile characterized by increased JAK1 expression. Following Poly I:C stimulation, PBMCs from SA had a robust induction of interferon pathways compared with HC. CyTOF profiling of Poly I:C stimulated and unstimulated PBMCs (n = 160,000) from the same individuals (SA = 5; HC = 3) demonstrated higher CD8 + and CD8 + effector T cells in SA at baseline, followed by a decrease of CD8 + effector T cells after poly I:C stimulation. CONCLUSIONS: Single-cell profiling of an in vitro model using PBMCs in patients with SA identified activation of pro-inflammatory pathways at baseline and strong response to Poly I:C, as well as quantitative changes in CD8 + effector cells. Thus, transcriptomic and cell quantitative changes are associated with immune cell heterogeneity in this model to evaluate interferon responses in severe asthma.

Immunotherapy targeting 4-1BB: mechanistic rationale, clinical results, and future strategies.

4-1BB (CD137, tumor necrosis factor receptor superfamily 9) is an inducible costimulatory receptor expressed on activated T and natural killer (NK) cells. 4-1BB ligation on T cells triggers a signaling cascade that results in upregulation of antiapoptotic molecules, cytokine secretion, and enhanced effector function. In dysfunctional T cells that have a decreased cytotoxic capacity, 4-1BB ligation demonstrates a potent ability to restore effector functions. On NK cells, 4-1BB signaling can increase antibody-dependent cell-mediated cytotoxicity. Agonistic monoclonal antibodies targeting 4-1BB have been developed to harness 4-1BB signaling for cancer immunotherapy. Preclinical results in a variety of induced and spontaneous tumor models suggest that targeting 4-1BB with agonist antibodies can lead to tumor clearance and durable antitumor immunity. Clinical trials of 2 agonist antibodies, urelumab and utomilumab, are ongoing. Despite initial signs of efficacy, clinical development of urelumab has been hampered by inflammatory liver toxicity at doses >1 mg/kg. Utomilumab has a superior safety profile, but is a less potent 4-1BB agonist relative to urelumab. Both antibodies have demonstrated promising results in patients with lymphoma and are being tested in combination therapy trials with other immunomodulatory agents. In an effort to optimally leverage 4-1BB-mediated immune activation, the next generation of 4-1BB targeting strategies attempts to decouple the observed antitumor efficacy from the on-target liver toxicity. Multiple therapeutics that attempt to restrict 4-1BB agonism to the tumor microenvironment and minimize systemic exposure have emerged. 4-1BB is a compelling target for cancer immunotherapy and future agents show great promise for achieving potent immune activation while avoiding limiting immune-related adverse events.

Identification of mutations associated with acquired resistance to sunitinib in renal cell cancer.

Sunitinib is one of the most widely used targeted therapeutics for renal cell carcinoma (RCC), but acquired resistance against targeted therapies remains a major clinical challenge. To dissect mechanisms of acquired resistance and unravel reliable predictive biomarkers for sunitinib in RCC, we sequenced the exons of 409 tumor-suppressor genes and oncogenes in paired tumor samples from an RCC patient, obtained at baseline and after development of acquired resistance to sunitinib. From newly arising mutations, we selected, using in silico prediction models, six predicted to be deleterious, located in G6PD, LRP1B, SETD2, TET2, SYNE1, and DCC. Consistently, immunoblotting analysis of lysates derived from sunitinib-desensitized RCC cells and their parental counterparts showed marked differences in the levels and expression pattern of the proteins encoded by these genes. Our further analysis demonstrates essential roles for these proteins in mediating sunitinib cytotoxicity and shows that their loss of function renders tumor cells resistant to sunitinib in vitro and in vivo. Finally, sunitinib resistance induced by continuous exposure or by inhibition of the six proteins was overcome by treatment with cabozantinib or a low-dose combination of lenvatinib and everolimus. Collectively, our results unravel novel markers of acquired resistance to sunitinib and clinically relevant approaches for overcoming this resistance in RCC.

Cytokines in clinical cancer immunotherapy.

Cytokines are soluble proteins that mediate cell-to-cell communication. Based on the discovery of the potent anti-tumour activities of several pro-inflammatory cytokines in animal models, clinical research led to the approval of recombinant interferon-alpha and interleukin-2 for the treatment of several malignancies, even if efficacy was only modest. These early milestones in immunotherapy have been followed by the recent addition to clinical practice of antibodies that inhibit immune checkpoints, as well as chimeric antigen receptor T cells. A renewed interest in the anti-tumour properties of cytokines has led to an exponential increase in the number of clinical trials that explore the safety and efficacy of cytokine-based drugs, not only as single agents, but also in combination with other immunomodulatory drugs. These second-generation drugs under clinical development include known molecules with novel mechanisms of action, new targets, and fusion proteins that increase half-life and target cytokine activity to the tumour microenvironment or to the desired effector immune cells. In addition, the detrimental activity of immunosuppressive cytokines can be blocked by antagonistic antibodies, small molecules, cytokine traps or siRNAs. In this review, we provide an overview of the novel trends in the cytokine immunotherapy field that are yielding therapeutic agents for clinical trials.

Epidermal growth factor receptor and epididymis invasion as prognostic biomarkers in clinical stage I testicular germ cell tumours.

BACKGROUND: Inguinal orchiectomy is curative in 70-80% of clinical stage I testicular germ cell tumours (CS I TGCT). The identification of patients who are at low risk of relapse is critical to avoid unnecessary treatment. The aim of this study is to explore EGFR, hMLH-1/hMSH-2 and microsatellite instability (MSI) as potential prognostic factors of recurrence in CS I TGCT. METHODS: Fifty-six CS I TGCT patients who underwent inguinal orchiectomy were included in this study. We analysed the relationship between clinicopathological and molecular factors with survival. Analysis of hMLH1, hMSH2 and EGFR expression was carried out by immunohistochemistry. Methylation status of the hMLH1 promoter was determined by pyrosequencing analysis in selected cases. EGFR exons 19, 20, 21 were analysed by PCR labeled-fragments and MSI status was determined using standard Multiplex MSI assays. RESULTS: Classical pathological factors such as lymphovascular invasion, high percentage of embryonal carcinoma, rete testis invasion or tumour size ≥4 cm showed a significant relationship with a higher risk of relapse. Additionally, it was found that an epididymis invasion proved to be a significant independent poor prognostic factor of recurrence (p = 0.001). hMLH1 or hMSH2 expression showed no significant association with risk of relapse and no MSI was found. EGFR expression was observed in 30.4% of samples and its expression was associated with higher risk of relapse (HR 3.5; 95% CI 1.3-9.8; p = 0.016). None of the cases presented EGFR kinase domain mutations. CONCLUSIONS: Epididymis invasion and EGFR expression, but not hMLH-1/hMSH-2 or MSI, could be potentially useful as new prognostic factors of recurrence for CS I TGCT.

Quantitative cell-free circulating BRAFV600E mutation analysis by use of droplet digital PCR in the follow-up of patients with melanoma being treated with BRAF inhibitors.

BACKGROUND: Around 50% of cutaneous melanomas harbor the BRAF(V600E) mutation and can be treated with BRAF inhibitors. DNA carrying this mutation can be released into circulation as cell-free BRAF(V600E) (cfBRAF(V600E)). Droplet digital PCR (ddPCR) is an analytically sensitive technique for quantifying small concentrations of DNA. We studied the plasma concentrations of cfBRAF(V600E) by ddPCR in patients with melanoma during therapy with BRAF inhibitors. METHODS: Plasma concentrations of cfBRAF(V600E) were measured in 8 controls and 20 patients with advanced melanoma having the BRAF(V600E) mutation during treatment with BRAF inhibitors at baseline, first month, best response, and progression. RESULTS: The BRAF(V600E) mutation was detected by ddPCR even at a fractional abundance of 0.005% in the wild-type gene. Agreement between tumor tissue BRAF(V600E) and plasma cfBRAF(V600E) was 84.3%. Baseline cfBRAF(V600E) correlated with tumor burden (r = 0.742, P < 0.001). cfBRAF(V600E) concentrations decreased significantly at the first month of therapy (basal median, 216 copies/mL; Q1-Q3, 27-647 copies/mL; first response median, 0 copies/mL; Q1-Q3, 0-49 copies/mL; P < 0.01) and at the moment of best response (median, 0 copies/mL; Q1-Q3, 0-33 copies/mL; P < 0.01). At progression, there was a significant increase in the concentration of cfBRAF(V600E) compared with best response (median, 115 copies/mL; Q1-Q3, 3-707 copies/mL; P = 0.013). Lower concentrations of basal cfBRAF(V600E) were significantly associated with longer overall survival and progression-free survival (27.7 months and 9 months, respectively) than higher basal concentrations (8.6 months and 3 months, P < 0.001 and P = 0.024, respectively). CONCLUSIONS: cfBRAF(V600E) quantification in plasma by ddPCR is useful as a follow-up to treatment response in patients with advanced melanoma.

PD-1H/VISTA mediates immune evasion in acute myeloid leukemia.

Acute myeloid leukemia (AML) presents a pressing medical need in that it is largely resistant to standard chemotherapy as well as modern therapeutics, such as targeted therapy and immunotherapy, including anti-programmed cell death protein (anti-PD) therapy. We demonstrate that programmed death-1 homolog (PD-1H), an immune coinhibitory molecule, is highly expressed in blasts from the bone marrow of AML patients, while normal myeloid cell subsets and T cells express PD-1H. In studies employing syngeneic and humanized AML mouse models, overexpression of PD-1H promoted the growth of AML cells, mainly by evading T cell-mediated immune responses. Importantly, ablation of AML cell-surface PD-1H by antibody blockade or genetic knockout significantly inhibited AML progression by promoting T cell activity. In addition, the genetic deletion of PD-1H from host normal myeloid cells inhibited AML progression, and the combination of PD-1H blockade with anti-PD therapy conferred a synergistic antileukemia effect. Our findings provide the basis for PD-1H as a potential therapeutic target for treating human AML.

Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure.

Introduction: Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy. Methods: TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352). Results: Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro. Discussion: This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

Whole exome sequencing and machine learning germline analysis of individuals presenting with extreme phenotypes of high and low risk of developing tobacco-associated lung adenocarcinoma.

BACKGROUND: Tobacco is the main risk factor for developing lung cancer. Yet, while some heavy smokers develop lung cancer at a young age, other heavy smokers never develop it, even at an advanced age, suggesting a remarkable variability in the individual susceptibility to the carcinogenic effects of tobacco. We characterized the germline profile of subjects presenting these extreme phenotypes with Whole Exome Sequencing (WES) and Machine Learning (ML). METHODS: We sequenced germline DNA from heavy smokers who either developed lung adenocarcinoma at an early age (extreme cases) or who did not develop lung cancer at an advanced age (extreme controls), selected from databases including over 6600 subjects. We selected individual coding genetic variants and variant-rich genes showing a significantly different distribution between extreme cases and controls. We validated the results from our discovery cohort, in which we analysed by WES extreme cases and controls presenting similar phenotypes. We developed ML models using both cohorts. FINDINGS: Mean age for extreme cases and controls was 50.7 and 79.1 years respectively, and mean tobacco consumption was 34.6 and 62.3 pack-years. We validated 16 individual variants and 33 variant-rich genes. The gene harbouring the most validated variants was HLA-A in extreme controls (4 variants in the discovery cohort, p = 3.46E-07; and 4 in the validation cohort, p = 1.67E-06). We trained ML models using as input the 16 individual variants in the discovery cohort and tested them on the validation cohort, obtaining an accuracy of 76.5% and an AUC-ROC of 83.6%. Functions of validated genes included candidate oncogenes, tumour-suppressors, DNA repair, HLA-mediated antigen presentation and regulation of proliferation, apoptosis, inflammation and immune response. INTERPRETATION: Individuals presenting extreme phenotypes of high and low risk of developing tobacco-associated lung adenocarcinoma show different germline profiles. Our strategy may allow the identification of high-risk subjects and the development of new therapeutic approaches. FUNDING: See a detailed list of funding bodies in the Acknowledgements section at the end of the manuscript.

Up-regulated PLA2G10 in cancer impairs T cell infiltration to dampen immunity.

T cells are often absent from human cancer tissues during both spontaneously induced immunity and therapeutic immunotherapy, even in the presence of a functional T cell-recruiting chemokine system, suggesting the existence of T cell exclusion mechanisms that impair infiltration. Using a genome-wide in vitro screening platform, we identified a role for phospholipase A2 group 10 (PLA2G10) protein in T cell exclusion. PLA2G10 up-regulation is widespread in human cancers and is associated with poor T cell infiltration in tumor tissues. PLA2G10 overexpression in immunogenic mouse tumors excluded T cells from infiltration, resulting in resistance to anti-PD-1 immunotherapy. PLA2G10 can hydrolyze phospholipids into small lipid metabolites, thus inhibiting chemokine-mediated T cell mobility. Ablation of PLA2G10's enzymatic activity enhanced T cell infiltration and sensitized PLA2G10-overexpressing tumors to immunotherapies. Our study implicates a role for PLA2G10 in T cell exclusion from tumors and suggests a potential target for cancer immunotherapy.

Sequential immunotherapy and targeted therapy for metastatic BRAF V600 mutated melanoma: 4-year survival and biomarkers evaluation from the phase II SECOMBIT trial.

No prospective data were available prior to 2021 to inform selection between combination BRAF and MEK inhibition versus dual blockade of programmed cell death protein-1 (PD-1) and cytotoxic T lymphocyte antigen-4 (CTLA-4) as first-line treatment options for BRAFV600-mutant melanoma. SECOMBIT (NCT02631447) was a randomized, three-arm, noncomparative phase II trial in which patients were randomized to one of two sequences with immunotherapy or targeted therapy first, with a third arm in which an 8-week induction course of targeted therapy followed by a planned switch to immunotherapy was the first treatment. BRAF/MEK inhibitors were encorafenib plus binimetinib and checkpoint inhibitors ipilimumab plus nivolumab. Primary outcome of overall survival was previously reported, demonstrating improved survival with immunotherapy administered until progression and followed by BRAF/MEK inhibition. Here we report 4-year survival outcomes, confirming long-term benefit with first-line immunotherapy. We also describe preliminary results of predefined biomarkers analyses that identify a trend toward improved 4-year overall survival and total progression-free survival in patients with loss-of-function mutations affecting JAK or low baseline levels of serum interferon gamma (IFNy). These long-term survival outcomes confirm immunotherapy as the preferred first-line treatment approach for most patients with BRAFV600-mutant metastatic melanoma, and the biomarker analyses are hypothesis-generating for future investigations of predictors of durable benefit with dual checkpoint blockade and targeted therapy.

Immunotherapeutic synergy between anti-CD137 mAb and intratumoral administration of a cytopathic Semliki Forest virus encoding IL-12.

Intratumoral injection of Semliki Forest virus encoding interleukin-12 (SFV-IL-12) combines acute expression of IL-12 and stressful apoptosis of infected malignant cells. Agonist antibodies directed to costimulatory receptor CD137 (4-1BB) strongly amplify pre-existing cellular immune responses toward weak tumor antigens. In this study, we provide evidence for powerful synergistic effects of a combined strategy consisting of intratumoral injection of SFV-IL-12 and systemic delivery of agonist anti-CD137 monoclonal antibodies (mAbs), which was substantiated against poorly immunogenic B16 melanomas (B16-OVA and B16.F10) and TC-1 lung carcinomas. Effector CD8(ß)(+) T cells were sufficient to mediate complete tumor eradications. Accordingly, there was an intensely synergistic in vivo enhancement of cytotoxic T lymphocytes (CTL)-mediated immunity against the tumor antigens OVA and tyrosine-related protein-2 (TRP-2). This train of phenomena led to long-lasting tumor-specific immunity against rechallenge, attained transient control of the progression of concomitant tumor lesions that were not directly treated with SFV-IL-12 and caused autoimmune vitiligo. Importantly, we found that SFV-IL-12 intratumoral injection induces bright expression of CD137 on most tumor-infiltrating CD8(+) T lymphocytes, thereby providing more abundant targets for the action of the agonist antibody. This efficacious combinatorial immunotherapy strategy offers feasibility for clinical translation since anti-CD137 mAbs are already undergoing clinical trials and development of clinical-grade SFV-IL-12 vectors is in progress.