IL15 and IL21: Better When Membrane-Tethered Together on Antitumor T Cells

Systemic administration of homeostatic γ-chain cytokines mediates antitumor responses in some patients treated with adoptive immunotherapy. Yet many patients experience toxic side effects. New work presented herein suggests these limitations can be overcome by membrane-tethering IL15 and IL21 to T-cell products. This finding has major implications in advancing medicine. See related article by Nguyen et al., p. 1555.

Radiation and anti-PD-L1 synergize by stimulating a stem-like T cell population in the tumor-draining lymph node

Radiotherapy (RT) and anti-PD-L1 synergize to enhance local and distant (abscopal) tumor control. However, clinical results in humans have been variable. With the goal of improving clinical outcomes, we investigated the underlying synergistic mechanism focusing on a CD8+ PD-1+ Tcf-1+ stem-like T cell subset in the tumor-draining lymph node (TdLN). Using murine melanoma models, we found that RT + anti-PD-L1 induces a novel differentiation program in the TdLN stem-like population which leads to their expansion and differentiation into effector cells within the tumor. Our data indicate that optimal synergy between RT + anti-PD-L1 is dependent on the TdLN stem-like T cell population as either blockade of TdLN egress or specific stem-like T cell depletion reduced tumor control. Together, these data demonstrate a multistep stimulation of stem-like T cells following combination therapy which is initiated in the TdLN and completed in the tumor.

Clinically relevant orthotopic pancreatic cancer models for adoptive T cell transfer therapy

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor. Prognosis is poor and survival is low in patients diagnosed with this disease, with a survival rate of ~12% at 5 years. Immunotherapy, including adoptive T cell transfer therapy, has not impacted the outcomes in patients with PDAC, due in part to the hostile tumor microenvironment (TME) which limits T cell trafficking and persistence. We posit that murine models serve as useful tools to study the fate of T cell therapy. Currently, genetically engineered mouse models (GEMMs) for PDAC are considered a "gold-standard" as they recapitulate many aspects of human disease. However, these models have limitations, including marked tumor variability across individual mice and the cost of colony maintenance.

METHODS

Using flow cytometry and immunohistochemistry, we characterized the immunological features and trafficking patterns of adoptively transferred T cells in orthotopic PDAC (C57BL/6) models using two mouse cell lines, KPC-Luc and MT-5, isolated from C57BL/6 KPC-GEMM (KrasLSL-G12D/+p53-/- and KrasLSL-G12D/+p53LSL-R172H/+, respectively).

RESULTS

The MT-5 orthotopic model best recapitulates the cellular and stromal features of the TME in the PDAC GEMM. In contrast, far more host immune cells infiltrate the KPC-Luc tumors, which have less stroma, although CD4+ and CD8+ T cells were similarly detected in the MT-5 tumors compared with KPC-GEMM in mice. Interestingly, we found that chimeric antigen receptor (CAR) T cells redirected to recognize mesothelin on these tumors that signal via CD3ζ and 41BB (Meso-41BBζ-CAR T cells) infiltrated the tumors of mice bearing stroma-devoid KPC-Luc orthotopic tumors, but not MT-5 tumors.

CONCLUSIONS

Our data establish for the first time a reproducible and realistic clinical system useful for modeling stroma-rich and stroma-devoid PDAC tumors. These models shall serve an indepth study of how to overcome barriers that limit antitumor activity of adoptively transferred T cells.

Progressively Enhancing Stemness of Adoptively Transferred T Cells with PI3Kδ Blockade Improves Metabolism and Antitumor Immunity

Generating stem-like memory T cells (TSCM) is a potential strategy to improve adoptive immunotherapy. Elucidating optimal ways to modulate signaling pathways that enrich TSCM properties could identify approaches to achieve this goal. We discovered herein that blocking the PI3Kδ pathway pharmaceutically to varying degrees can generate T cells with increasingly heightened stemness properties, based on the progressive enrichment of the transcription factors Tcf1 and Lef1. T cells with enhanced stemness features exhibited metabolic plasticity, marked by improved mitochondrial function and glucose uptake after tumor recognition. Conversely, T cells with low or medium stemness were less metabolically dynamic, vulnerable to antigen-induced cell death, and expressed more inhibitory checkpoint receptors. Only T-cell receptor-specific or chimeric antigen receptor (CAR)-specific T cells with high stemness persisted in vivo and mounted protective immunity to tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor-infiltrating lymphocytes and CAR T cells with elevated stemness properties, in turn bolstering their capacity to regress human solid tumors. The stemness level of T cells in vitro was important, ultimately impacting their efficacy in mice bearing three distinct solid tumors. Lef1 and Tcf1 sustained antitumor protection by donor high CD8+ TSCM or CD4+ Th17SCM, as deletion of either one compromised the therapeutic efficacy. Collectively, these findings highlight the importance of strategic modulation of PI3Kδ signaling in T cells to induce stemness and lasting protective responses to solid tumors.

SIGNIFICANCE

Elevating T-cell stemness by progressively blocking PI3Kδ signaling during ex vivo manufacturing of adoptive cell therapies alters metabolic and functional properties to enhance antitumor immunity dependent on Tcf1 and Lef1.

Distinct host preconditioning regimens differentially impact the antitumor potency of adoptively transferred Th17 cells

Background

Mechanisms by which distinct methods of host preconditioning impact the efficacy of adoptively transferred antitumor T helper cells is unknown.

Methods

CD4 + T cells with a transgenic TCR that recognize TRP-1 melanoma antigen were polarized to the T helper 17 (Th17) phenotype and then transferred into melanoma-bearing mice preconditioned with either total body irradiation or chemotherapy.

Results

We found that preconditioning mice with a non-myeloablative dose of total body irradiation (TBI of 5 Gy) was more effective than using an equivalently dosed non-myeloablative chemotherapy (CTX at 200 mg/kg) at augmenting therapeutic activity of anti-tumor TRP-1 Th17 cells. Anti-tumor Th17 cells engrafted better following preconditioning with TBI and regressed large established melanoma in all animals. Conversely, only half of mice survived long-term when preconditioned with CTX and infused with anti-melanoma Th17 cells. IL-17 and IFN-g produced by the infused Th17 cells, were detected in animals given either TBI or CTX preconditioning. Interestingly, inflammatory cytokines (G-CSF, IL-6, MCP-1, IL-5, and KC) were significantly elevated in the serum of mice preconditioned with TBI versus CTX after Th17 therapy.

Conclusions

Our results indicate, for the first time, that the antitumor response, persistence, and cytokine profiles resulting from Th17 therapy are impacted by the specific regimen of host preconditioning. This work is important for understanding mechanisms that promote long-lived responses by ACT, particularly as CD4 + based T cell therapies are now emerging in the clinic.

FcγRIIB expressed on CD8+ T cells limits responsiveness to PD-1 checkpoint inhibition in cancer

Checkpoint inhibition using Fc-containing monoclonal antibodies has emerged as a powerful therapeutic approach to augment antitumor immunity. We recently showed that FcγRIIB, the only inhibitory IgG-Fc receptor, is expressed on a population of highly differentiated effector CD8+ T cells in the tumors of mice and humans, raising the possibility that CD8+ T cell responses may be directly modulated by checkpoint inhibitor binding to T cell-expressed FcγRIIB. Here, we show that despite exhibiting strong proliferative and cytokine responses at baseline, human FcγRIIBpos CD8+ T cells exhibited reduced responsiveness to both PD-1 and CTLA-4 checkpoint inhibition as compared with FcγRIIBneg CD8+ T cells in vitro. Moreover, frequencies of FcγRIIBpos CD8+ T cells were reduced after treatment of patients with melanoma with nivolumab in vivo. This reduced responsiveness was FcγRIIB dependent, because conditional genetic deletion of FcγRIIB on tumor-specific CD8+ T cells improved response to checkpoint blockade in B16 and LLC mouse models of cancer. The limited responsiveness of FcγRIIBpos CD8+ T cells was also dependent on an intact Fc region of the checkpoint inhibitor, in that treatment with Fc-devoid anti-PD-1 F(ab) fragments resulted in increased proliferation of FcγRIIBpos CD8+ T cells, without altering the response of FcγRIIBneg CD8+ T cells. Last, the addition of FcγRIIB blockade improved efficacy of PD-1 checkpoint inhibition in mouse models of melanoma, lung, and colon cancer. These results illuminate an FcγRIIB-mediated, cell-autonomous mechanism of CD8+ T cell suppression, which limits the efficacy of checkpoint inhibitors during antitumor immune responses in vivo.

Does non-metastatic gastric cancer of the cardia warrant a different treatment strategy?

BACKGROUND

Multimodal treatment strategies with surgery as its centerpiece have been accepted as the standard of care in nonmetastatic cardia gastric cancer (CGC). There remains a lack of consensus regarding the optimal multimodal treatment strategy.

METHOD

We queried National Cancer Database from 2004 to 2016 to identify patients with resected nonmetastatic CGC who received perioperative chemotherapy (PEC), postoperative chemoradiation therapy (POCR), or postoperative chemotherapy (POC). A subgroup analysis was performed in optimally treated patients defined as initial chemotherapy within 45 days of diagnosis, resection within 45 days of diagnosis, negative margins, adjuvant chemotherapy within 90 days of resection, and standard radiation dose (45 Gy). Kaplan-Meier, Univariate analysis (UVA), and Multivariable analysis (MVA) were performed.

RESULTS

We identified 2387 patients. Median survival was 38.8 months in the PEC group, 36 months in the POCR group, and 32.3 months in the POC group (p = 0.1025). On UVA, patients treated with PEC had an association with improved survival (HR, 0.83; p = 0.037) when compared with POC. On MVA, no significant difference was noted in overall survival (OS) between PEC, POCR, and POC, similar to subgroup analysis of optimally treated cohort.

CONCLUSION

OS rate in nonmetastatic CGC is not significantly different between patients receiving PEC, POCR, or POC.

Impact of nodal status in determining multimodal treatment strategies in non-cardia gastric cancer

BACKGROUND

Patients with resectable noncardia gastric cancer may be subjected to perioperative chemotherapy (PEC), postoperative chemoradiation (POCR), or postoperative chemotherapy (POC). We analyzed these treatment strategies to determine optimal therapy based on nodal status.

METHOD

The National Cancer Database was used to identify patients with resected noncardia gastric cancer (2004-2016). Patients were stratified based on clinical nodal status-negative (cLN-), positive (cLN+) and pathological nodal status (pLN-, pLN+). In cLN- patients who underwent upfront resection and were upstaged to pLN+, POC, and POCR were compared. Overall survival (OS) with PEC, POCR, and POC were compared in cLN- and cLN+.

RESULTS

We identified 6142 patients (cLN-: 3831; cLN+: 2311). In cLN- patients who underwent upfront resection (N = 3423), 69% were upstaged to pLN+ disease (N = 2499; POCR = 1796, POC = 703). On MVA, POCR was associated with significantly improved OS when compared to POC (hazard ratio [HR]: 0.75; p < 0.001). In patients with cLN- disease (PEC = 408; POCR = 2439; POC = 984), PEC(HR: 0.77; p = 0.01) and POCR(HR: 0.81; p < 0.001) were associated with improved OS compared with POC. In cLN+ group (PEC = 452; POCR = 1284; POC = 575), POCR was associated with improved OS compared with POC (HR: 0.81; p < 0.01), and trend towards improved OS was noted when PEC(HR: 0.83; p = 0.055) was compared with POC.

CONCLUSION

Postoperative chemoradiation may be the preferred treatment strategy over postoperative chemotherapy in non-cardia gastric cancer patients who receive upfront resection and are upstaged from clinically node negative to pathologically node positive disease.

Perspectives in Immunotherapy: meeting report from Immunotherapy Bridge (Naples, November 30th-December 1st, 2022)

The discovery and development of novel treatments that harness the patient's immune system and prevent immune escape has dramatically improved outcomes for patients across cancer types. However, not all patients respond to immunotherapy, acquired resistance remains a challenge, and responses are poor in certain tumors which are considered to be immunologically cold. This has led to the need for new immunotherapy-based approaches, including adoptive cell transfer (ACT), therapeutic vaccines, and novel immune checkpoint inhibitors. These new approaches are focused on patients with an inadequate response to current treatments, with emerging evidence of improved responses in various cancers with new immunotherapy agents, often in combinations with existing agents. The use of cell therapies, drivers of immune response, and trends in immunotherapy were the focus of the Immunotherapy Bridge (November 30th-December 1st, 2022), organized by the Fondazione Melanoma Onlus, Naples, Italy, in collaboration with the Society for Immunotherapy of Cancer.

Augmenting TCR signal strength and ICOS costimulation results in metabolically fit and therapeutically potent human CAR Th17 cells

IL-17-producing antigen-specific human T cells elicit potent antitumor activity in mice. Yet, refinement of this approach is needed to position it for clinical use. While activation signal strength regulates IL-17 production by CD4+ T cells, the degree to which T cell antigen receptor (TCR) and costimulation signal strength influences Th17 immunity remains unknown. We discovered that decreasing TCR/costimulation signal strength by incremental reduction of αCD3/costimulation beads progressively altered Th17 phenotype. Moreover, Th17 cells stimulated with αCD3/inducible costimulator (ICOS) beads produced more IL-17A, IFNγ, IL-2, and IL-22 than those stimulated with αCD3/CD28 beads. Compared with Th17 cells stimulated with the standard, strong signal strength (three beads per T cell), Th17 cells propagated with 30-fold fewer αCD3/ICOS beads were less reliant on glucose and favored the central carbon pathway for bioenergetics, marked by abundant intracellular phosphoenolpyruvate (PEP). Importantly, Th17 cells stimulated with weak αCD3/ICOS beads and redirected with a chimeric antigen receptor that recognizes mesothelin were more effective at clearing human mesothelioma. Less effective CAR Th17 cells generated with high αCD3/ICOS beads were rescued by overexpressing phosphoenolpyruvate carboxykinase 1 (PCK1), a PEP regulator. Thus, Th17 therapy can be improved by using fewer activation beads during manufacturing, a finding that is cost effective and directly translatable to patients.

Potential clinical implications of CD4+CD26high T cells for nivolumab treated melanoma patients

BACKGROUND

Nivolumab is an anti-PD1 antibody that has dramatically improved metastatic melanoma patients' outcomes. Nevertheless, many patients are resistant to PD-1 inhibition, occasionally experiencing severe off-target immune toxicity. In addition, no robust and reproducible biomarkers have yet been validated to identify the correct selection of patients who will benefit from anti-PD-1 treatment avoiding unwanted side effects. However, the strength of CD26 expression on CD4+ T lymphocytes permits the characterization of three subtypes with variable degrees of responsiveness to tumors, suggesting that the presence of CD26-expressing T cells in patients might be a marker of responsiveness to PD-1-based therapies.

METHODS

The frequency distribution of peripheral blood CD26-expressing cells was investigated employing multi-parametric flow cytometry in 69 metastatic melanoma patients along with clinical characteristics and blood count parameters at baseline (W0) and compared to 20 age- and sex-matched healthy controls. Percentages of baseline CD4+CD26high T cells were correlated with the outcome after nivolumab treatment. In addition, the frequency of CD4+CD26high T cells at W0 was compared with those obtained after 12 weeks (W1) of therapy in a sub-cohort of 33 patients.

RESULTS

Circulating CD4+CD26high T cells were significantly reduced in melanoma patients compared to healthy subjects (p = 0.001). In addition, a significant association was observed between a low baseline percentage of CD4+CD26high T cells (< 7.3%) and clinical outcomes, measured as overall survival (p = 0.010) and progression-free survival (p = 0.014). Moreover, patients with clinical benefit from nivolumab therapy had significantly higher frequencies of circulating CD4+CD26high T cells than patients with non-clinical benefit (p = 0.004) at 12 months. Also, a higher pre-treatment proportion of circulating CD4+CD26high T cells was correlated with Disease Control Rate (p = 0.014) and best Overall Response Rate (p = 0.009) at 12 months. Interestingly, after 12 weeks (W1) of nivolumab treatment, percentages of CD4+CD26high T cells were significantly higher in comparison with the frequencies measured at W0 (p < 0.0001), aligning the cell counts with the ranges seen in the blood of healthy subjects.

CONCLUSIONS

Our study firstly demonstrates that peripheral blood circulating CD4+CD26high T lymphocytes represent potential biomarkers whose perturbations are associated with reduced survival and worse clinical outcomes in melanoma patients.

The magic of small-molecule drugs during ex vivo expansion in adoptive cell therapy

In the past decades, advances in the use of adoptive cellular therapy to treat cancer have led to unprecedented responses in patients with relapsed/refractory or late-stage malignancies. However, cellular exhaustion and senescence limit the efficacy of FDA-approved T-cell therapies in patients with hematologic malignancies and the widespread application of this approach in treating patients with solid tumors. Investigators are addressing the current obstacles by focusing on the manufacturing process of effector T cells, including engineering approaches and ex vivo expansion strategies to regulate T-cell differentiation. Here we reviewed the current small-molecule strategies to enhance T-cell expansion, persistence, and functionality during ex vivo manufacturing. We further discussed the synergistic benefits of the dual-targeting approaches and proposed novel vasoactive intestinal peptide receptor antagonists (VIPR-ANT) peptides as emerging candidates to enhance cell-based immunotherapy.

The degree of T cell stemness differentially impacts the potency of adoptive cancer immunotherapy in a Lef-1 and Tcf-1 dependent manner

Generating stem memory T cells (T _SCM ) is a key goal for improving cancer immunotherapy. Yet, the optimal way to modulate signaling pathways that enrich T _SCM properties remains elusive. Here, we discovered that the degree to which the PI3Kδ pathway is blocked pharmaceutically can generate T cells with differential levels of stemness properties. This observation was based on the progressive enrichment of transcriptional factors of stemness (Tcf-1 and Lef-1). Additional investigation revealed that T cells with high stemness features had enhanced metabolic plasticity, marked by heightened mitochondrial function and glucose uptake. Conversely, T cells with low or medium features of stemness expressed more inhibitory checkpoint receptors (Tim-3, CD39) and were vulnerable to antigen-induced cell death. Only TCR-antigen specific T cells with high stemness persisted following adoptive transfer in vivo and mounted protective immunity to melanoma tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor infiltrating lymphocytes (TILs) and CAR T cells with heightened stemness properties, in turn bolstering their capacity to regress human mesothelioma tumors. We find that the level of stemness T cells possess in vitro differentially impacts their potency upon transfer in three tumor models. Mechanistically, both Lef-1 and Tcf-1 sustain anti-tumor protection by high T _SCM , as deletion of either one compromised cellular therapy. Collectively, these findings highlight the therapeutic potential of carefully modulating PI3Kδ signaling in T cells to confer high stemness and mediate protective responses to solid tumors.

Dual IL-6 and CTLA-4 blockade regresses pancreatic tumors in a T cell and CXCR3-dependent manner

This study aimed to enhance anti-tumor immune responses to pancreatic cancer via antibody-based blockade of IL-6 and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). Mice bearing subcutaneous or orthotopic pancreatic tumors were treated with blocking antibodies to IL 6 and/or CTLA-4. In both tumor models, dual IL-6 and CTLA-4 blockade significantly inhibited tumor growth. Additional investigations revealed that dual therapy induced an overwhelming infiltration of T cells into the tumor as well as changes in CD4+ T cell subsets. Dual blockade therapy elicited CD4+ T cells to secrete increased IFN-γ in vitro. Likewise, in vitro stimulation of pancreatic tumor cells with IFN-γ profoundly increased tumor cell production of CXCR3 specific chemokines, even in the presence of IL-6. In vivo blockade of CXCR3 prevented orthotopic tumor regression in the presence of the combination treatment, demonstrating a dependence on the CXCR3 axis for anti-tumor efficacy. Both CD4+ and CD8+ T cells were required for the anti-tumor activity of this combination therapy, as their in vivo depletion via antibodies impaired outcomes. These data represent the first report of IL-6 and CTLA 4 blockade as a means to regress pancreatic tumors with defined operative mechanisms of efficacy. Given these results, this therapeutic combination has potential for immediate clinical translation.

A dhesion analysis via a tumor vasculature-like microfluidic device identifies CD8+ T cells with enhanced tumor homing to improve cell therapy

CD8⁺ T cell recruitment to the tumor microenvironment is critical for the success of adoptive cell therapy (ACT). Unfortunately, only a small fraction of transferred cells home to solid tumors. Adhesive ligand-receptor interactions have been implicated in CD8⁺ T cell homing; however, there is a lack of understanding of how CD8⁺ T cells interact with tumor vasculature-expressed adhesive ligands under the influence of hemodynamic flow. Here, the capacity of CD8⁺ T cells to home to melanomas is modeled ex vivo using an engineered microfluidic device that recapitulates the hemodynamic microenvironment of the tumor vasculature. Adoptively transferred CD8⁺ T cells with enhanced adhesion in flow in vitro and tumor homing in vivo improve tumor control by ACT in combination with immune checkpoint blockade. These results show that engineered microfluidic devices can model the microenvironment of the tumor vasculature to identify subsets of T cells with enhanced tumor infiltrating capabilities, a key limitation in ACT.

Time to first treatment and optimal adjuvant treatment strategy in patients with resectable gastric cancer pathologically upstaged to lymph node–positive disease

473

Background: Treatment strategies in resectable gastric cancer (GC) patients include perioperative chemotherapy (PEC), postoperative chemoradiation therapy (POCR), and postoperative chemotherapy (POC). Treatment delay can lead to metastases with unfavorable outcomes. We aim to identify the distribution of patients upstaged to pathologically node positive disease (pLN+) stratified by time and the optimal treatment in this cohort. Methods: We analyzed resected GC patients in the National Cancer Database (2004-2016) with clinically node negative disease (cLN-). Time from diagnosis to first definitive therapy was stratified as ≤2, >2 to ≤4, and >4 weeks. The distribution of patients upstaged from cLN- to pLN+ disease, the concordance between cLN- and pathologically lymph node negative (pLN-) disease based on treatment strategy, and time to first definitive therapy was analyzed. POC and POCR were compared to evaluate their effect on overall survival (OS) in patients with cLN- upstaged to pLN+ disease. Kaplan-Meier test, log-rank test, multivariable Cox proportional hazards analysis (MVA) were performed. Results: Of the 4,828 gastric cancer patients with cLN- disease, 514 (10.65%) patients received PEC and 4,314 (89.35%) patients received upfront surgery followed by POCR/POC. Distribution of patients stratified by time between diagnosis to first definitive treatment - chemotherapy (PEC) or surgery (POC/POCR), for ≤2 weeks was 9.5% vs. 33%, >2 - ≤4 weeks was 28.4% vs. 24.2% and >4weeks was 62% vs 42.7%, respectively. Patients upstaged from cLN- to pLN+ disease in the PEC group was 43.37%(n=206), and 70%(n=2574) in the upfront surgery group (POC/POCR). Of the 206 (43.37%) patients upstaged from cLN- to pLN+ in the PEC cohort, the upstage rate was 7.77% when chemotherapy was started within 2 weeks of diagnosis, compared to 27.67% with >2 to ≤4 weeks, and 64.56% with >4 weeks. Of the 2,574 (70%) patients upstaged in the upfront surgery cohort (POCR/POC), 30.61% were upstaged in ≤2 weeks, 24.95% in >2 to ≤4 weeks, and 44.44% in ≥4 weeks. On MVA, patients with cLN- disease that were pLN- (POCR=766, POC=341) had no significant difference in OS when treated with POCR (HR 1.11, p=0.39) compared to POC. Patients with pLN+ (POCR=2300, POC=907) disease had an association with improved OS when treated with POCR (HR 0.78, p<0.001) compared to POC. Conclusions: When resectable gastric cancer patients undergoing upfront surgery are upstaged from clinically node negative to pathologically node positive disease, postoperative chemoradiation therapy may be the optimal treatment strategy compared to postoperative chemotherapy. Clinical nodal status may not be an optimal predictor of nodal disease.

Stress-Mediated Attenuation of Translation Undermines T-cell Activity in Cancer

Protein synthesis supports robust immune responses. Nutrient competition and global cell stressors in the tumor microenvironment (TME) may impact protein translation in T cells and antitumor immunity. Using human and mouse tumors, we demonstrated here that protein translation in T cells is repressed in solid tumors. Reduced glucose availability to T cells in the TME led to activation of the unfolded protein response (UPR) element eIF2α (eukaryotic translation initiation factor 2 alpha). Genetic mouse models revealed that translation attenuation mediated by activated p-eIF2α undermines the ability of T cells to suppress tumor growth. Reprograming T-cell metabolism was able to alleviate p-eIF2α accumulation and translational attenuation in the TME, allowing for sustained protein translation. Metabolic and pharmacological approaches showed that proteasome activity mitigates induction of p-eIF2α to support optimal antitumor T-cell function, protecting from translation attenuation and enabling prolonged cytokine synthesis in solid tumors. Together, these data identify a new therapeutic avenue to fuel the efficacy of tumor immunotherapy.

SIGNIFICANCE

Proteasome function is a necessary cellular component for endowing T cells with tumor killing capacity by mitigating translation attenuation resulting from the unfolded protein response induced by stress in the tumor microenvironment.

Combined MEK/PD-L1 Inhibition Alters Peripheral Cytokines and Lymphocyte Populations Correlating with Improved Clinical Outcomes in Advanced Biliary Tract Cancer

PURPOSE

Biliary tract cancers (BTC) are aggressive malignancies refractory to chemotherapy and immunotherapy. MEK inhibition (MEKi)-based regimens may have utility in this disease when combined with PD-L1 blockade. We hypothesize that dual MEK/PD-L1 inhibition alters circulating soluble and cellular immune mediators to improve clinical outcomes in patients with advanced BTC.

EXPERIMENTAL DESIGN

We examined immune features in peripheral blood from 77 patients with advanced BTC enrolled in a phase II clinical trial investigating atezolizumab with or without cobimetinib. Plasma and peripheral blood mononuclear cells (PBMC) were isolated from whole blood to evaluate soluble factors and immune cell populations. Baseline blood samples were additionally compared with healthy donors to identify immune signatures unique to BTC.

RESULTS

At baseline, the soluble factors platelet-derived growth factor B (PDGF)-BB, placental growth factor (PlGF)-1, IL5, and IL17A were elevated in patients with BTC compared with healthy adult donors, and higher baseline frequencies of CD8+BTLA+ T cells correlated with better overall survival (OS) in this trial. There were also significant treatment-related alterations in several factors, including decreased PDGF-BB following combination treatment, that correlated with improved OS and progression-free survival (PFS). Higher baseline levels of IL23 and RANTES corresponded to improved clinical outcomes following combination treatment. Dual MEK/PD-L1 inhibition increased populations of CD4+TIM3+ and decreased CD8+VISTA+ T cells, correlating with worse OS and better PFS, respectively.

CONCLUSIONS

This work represents a comprehensive analysis of peripheral immune features in patients with BTC and systemic responses to dual MEK/PD-L1 inhibition. These data support further investigation to understand how MEKi combines with immunotherapeutic approaches to improve clinical outcomes for patients with advanced BTC.

Association of age with survival in older patients with cutaneous melanoma treated with immune checkpoint inhibitors

INTRODUCTION

Several types of immune checkpoint inhibitors (ICIs) are approved to treat advanced melanoma, but their effectiveness has not been compared in older patients treated outside of a clinical trial. Moreover, evidence suggests that a patient's response to ICI therapy may vary by age and type of ICI. The purpose of this study was to compare survival by ICI type in older patients with melanoma and to investigate treatment effect modification by age.

MATERIALS AND METHODS

Using the SEER-Medicare database, we identified patients with cutaneous melanoma (2012-2015) treated with an ICI (CTLA-4, PD-1, or combination CTLA-4 + PD-1 inhibitors). Cox proportional hazards regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CI) for ICI types. We used an interaction term and stratified models to test for treatment effect modification by age.

RESULTS

Of the 1435 patients included in our analysis, 790 (55.1%) received CTLA-4 inhibitors, 512 (35.7%) received PD-1 inhibitors, and 133 (9.3%) were treated with combination ICIs. Median survival ranged from 13.4 months (95%CI: 10.7-16.3) for CTLA-4 inhibitors to 23.5 months (95%CI: 16.2-30.0) for combination ICIs. In multivariable models, the risk of death was lower with PD-1 inhibitors compared to CTLA-4 inhibitors (HR = 0.78, 95%CI: 0.68-0.89). An age*ICI type interaction term was significant (p < 0.001), and survival gains were greater the older age group (≥80) compared to the younger group (65-79).

DISCUSSION

In a population-based setting, we identified important differences in survival by ICI type in older patients with melanoma treated with ICIs, with prolonged survival associated with PD-1 inhibitors compared to CTLA-4 inhibitors.

Abstract 594: FcγRIIB expressed on activated CD8+ T cells restrains T cell responsiveness to αPD-1 immune checkpoint blockade in melanoma patients

In this study, we show that FcγRIIB on the surface of CD8+ T cells reduces responsiveness to αPD-1 antibody in melanoma patients, and we suggest therapeutic strategies to improve CD8+ T cell response to PD-1 blockade. Immune checkpoint blockade (ICB) such as PD-1 blockade has drastically improved melanoma patient survival, but not all patients respond to ICB. Elevated expression of inhibitory molecules on CD8+ T cells dampens the antitumor T cell response and limits patient response to ICB. We recently showed that the inhibitory receptor FcγRIIB is expressed on effector-like memory CD8+ T cells and functions in a cell-intrinsic manner to temper activated CD8+ T cells in vivo. We found that FcγRIIB+ CD8+ T cells were more proliferative and secreted more pro-inflammatory cytokines than their FcγRIIB- counterparts. FcγRIIB+ CD8+ T cells also expressed elevated levels of exhaustion/activation markers (PD-1, CTLA-4, etc.). As these markers are also the targets of immune checkpoint blockade, we investigated the response of these cells to checkpoint therapy. Interestingly, FcγRIIB+ cells exhibited significantly reduced proliferation to αPD-1 and αCTLA-4 in vitro compared to FcγRIIB- cells (p&lt;0.05). In stage-IV melanoma patients, we observed a decrease in FcγRIIB+ CD8+ T cells (p&lt;0.05) following administration of nivolumab (αPD-1), a finding replicated in mouse models in vivo. Because ICB utilizes IgG antibody, a canonical ligand for FcγRs, we hypothesized that ICB antibodies could bind FcγRIIB on CD8+ T cells and elicit counterproductive negative signaling. In a B16-melanoma mouse model, genetic deletion of FcγRIIB on CD8+ T cells increased CD8+ T-cell infiltration and IFNγ production at the tumor in αPD-1 treated mice (p&lt;0.05). Further, blocking inhibitory signaling through FcγRIIB in αPD-1-treated animals increased the number of Ki67+, TNF+, and IFNγ+ CD8+ T cells at the tumor and delayed tumor growth compared to αPD-1 treatment alone (p&lt;0.05). Thus, we show that FcγRIIB is a novel inhibitory molecule on CD8+ T cells that limits T-cell responsiveness to αPD-1 immunotherapy and that T cell-expressed FcγRIIB should be a consideration in the development of therapeutic antibodies. We also demonstrate the efficacy of blocking FcγRIIB to enhance the CD8+ T-cell response to αPD-1 in mice, illuminating a potential new therapeutic target to improve melanoma patient response to ICB.

Citation Format: Kelsey B. Bennion, Marvi Tariq, Kirsten M. Baecher, Chrystal M. Paulos, Ragini Kudchadkar, Michael C. Lowe, Mandy L. Ford. FcγRIIB expressed on activated CD8+ T cells restrains T cell responsiveness to αPD-1 immune checkpoint blockade in melanoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 594.

Abstract 5595: Statin drugs have anti-tumor activity and enhance responses to anti-PD-1 therapy in preclinical models of head and neck cancer

Background/Rationale: Head and neck squamous cell carcinoma (HNSCC) is a common malignancy with significant morbidity and mortality. Approximately half of patients with HNSCC develop recurrent or metastatic disease. Recently, anti-PD-1 immune checkpoint blockade was FDA-approved for first-line treatment of recurrent or metastatic disease, and although relatively well tolerated, only a minority of patients respond. There is an unmet clinical need for agents that enhance responses to anti-PD-1 therapy without excessive toxicity. HMG-CoA reductase inhibitors, also known as statin drugs, are in wide clinical use for hyperlipidemia and are inexpensive and well tolerated. Statin drugs are associated with superior survival outcomes in retrospective population studies of several cancers, including HNSCC. Moreover, statins may reduce multiple treatment-related toxicities, such as radiation-induced skin fibrosis and cisplatin chemotherapy-induced hearing loss. Emerging data suggest that statins may also enhance some aspects of anti-tumor immunity, but this has not been studied in HNSCC. Further, the pleiotropic effects of different statin drugs are highly variable. We hypothesized that a subset of statin drugs would enhance anti-tumor immunity and delay tumor growth in preclinical models of HNSCC.

Methods: Two immunocompetent, syngeneic murine models of oral cancer (MOC1 and MOC22) were used. To identify which of the seven FDA-approved statin drugs are capable of antitumor activity and enhancing T-cell induced killing, we used a high-throughput ex vivo co-culture assay of murine oral cancer cells and tumor infiltrating CD8+ T lymphocytes. Tumor-bearing mice were then treated with anti-PD-1 antibody (twice weekly IP) and/or statin drug (daily by oral gavage) for up to three weeks, and tumor kinetics and survival were tracked.

Results: When added at or near physiologic drug concentrations, all 7 statins strongly inhibited proliferation of MOC1 and MOC22 cell lines. Moreover, the combination of CD8+ T cells and a subset of statins mediated nearly two-fold tumor cell killing effect versus either treatment used alone. In mice, tumor growth delay did not reach statistical significance with statins or anti-PD-1 alone. However, combination therapy induced a significant tumor growth delay versus control mice (p&lt;0.05).

Conclusions: Our results have significant implications for both biologic mechanisms and therapeutic applications of statin drugs in HNSCC. Additional experiments to investigate the mechanisms by which statins inhibit tumor cell proliferation and enhance anti-tumor immunity are currently underway.

Funding: supported by Winship Cancer Institute and the Morningside Center for Innovative and Affordable Medicine.

Citation Format: Andre J. Burnham, Vikash Kansal, Brendan L. Kinney, Chrystal M. Paulos, Gregory B. Lesinski, Nabil F. Saba, Nicole C. Schmitt. Statin drugs have anti-tumor activity and enhance responses to anti-PD-1 therapy in preclinical models of head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5595.

Perspectives in Immunotherapy: meeting report from the Immunotherapy Bridge, December 1st-2nd, 2021

Over the past decade, immunotherapy has become an increasingly fundamental modality in the treatment of cancer. The positive impact of immune checkpoint inhibition, especially anti-programmed death (PD)-1/PD-ligand (L)1 blockade, in patients with different cancers has focused attention on the potential for other immunotherapeutic approaches. These include inhibitors of additional immune checkpoints, adoptive cell transfer (ACT), and therapeutic vaccines. Patients with advanced cancers who previously had limited treatment options available may now benefit from immunotherapies that can offer durable responses and improved survival outcomes. However, despite this, a significant proportion of patients fail to respond to immunotherapy, especially those with less immunoresponsive cancer types, and there remains a need for new treatment strategies.The virtual Immunotherapy Bridge (December 1st-2nd, 2021), organized by the Fondazione Melanoma Onlus, Naples, Italy in collaboration with the Society for Immunotherapy of Cancer addressed several areas of current research in immunotherapy, including lessons learned from cell therapies, drivers of immune response, and trends in immunotherapy across different cancers, and these are summarised here.

Case Report: Delayed Onset Multi-Organ Toxicities in a Melanoma Patient Achieving Complete Response to BRAF/MEK Inhibition

Autoimmune toxicities, while common following treatment with cancer immunotherapies, are not well-characterized in patients treated with BRAF/MEK inhibitors. Emerging data suggest that autoimmune effects may be linked with superior responses to both treatment modalities; however, there is little evidence describing mechanisms of immune-related toxicity for patients on BRAF/MEK inhibitors. Here we describe the experience of a 59-year-old HLA-A2, A29, B27-positive male with recurrent/metastatic melanoma. After progression on checkpoint inhibitor therapy, he was treated with dabrafenib/trametinib followed by encorafenib/binimetinib, which were well-tolerated and resulted in a complete response. Eighteen months into BRAF/MEK inhibitor therapy, and three months after initially finding a complete response, he developed a series of sudden-onset, severe toxicities: namely, bilateral panuveitis, cytopenias, joint pain, skin rash, hypercalcemia, and interstitial nephritis, which led to BRAF/MEKi cessation. Immunological analyses revealed induction of a peripheral type-17 cytokine signature characterized by high IL-23, IL-6, IL-10, IL-17A/F, IL-1β, and IL-21 among other cytokines in plasma corresponding with the height of symptoms. These findings highlight a novel instance of delayed autoimmune-like reaction to BRAF/MEK inhibition and identify a possible role for Th/Tc17 activation in their pathogenesis thus warranting future clinical and immunological characterization.

Programmed death 1 (PD‐1) and ligand (PD‐L1) inhibitors in head and neck squamous cell carcinoma: A meta‐analysis

Background

PD‐1 and PD‐L1 inhibitors have emerged as promising treatments for patients with head and neck squamous cell carcinoma (HNSCC).

Methods

Systematic review and meta‐analysis of PD‐1 and PD‐L1 inhibitors in HNSCC. Outcomes: median overall survival (mOS), median progression‐free survival (mPFS), Response Evaluation Criteria in Solid Tumors (RECIST) and treatment‐related adverse events (TRAEs).

Results

Eleven trials reported data on 1088 patients (mean age: 59.9 years, range: 18–90). The total mOS was 7.97 months (range: 6.0–16.5). Mean mPFS for all studies was 2.84 months (range: 1.9–6.5). PD‐1 inhibitors had a lower rate of RECIST Progressive Disease than PD‐L1 inhibitors (42.61%, 95% confidence interval [CI]: 36.29–49.06 vs. 56.79%, 95% CI: 49.18–64.19, P < 0.001). The rate of TRAEs of any grade (62.7%, 95% CI: 59.8–65.6) did not differ.

Conclusions

Meta‐analysis shows the efficacy of PD‐1 and PD‐L1 inhibitors in HNSCC and suggests a possible difference in certain RECIST criterion between PD‐1 and PD‐L1 inhibitors. Future work to investigate the clinical significance of these findings is warranted.

Significant Findings of this Study: 11 studies were analyzed in this meta‐analysis of PD‐1 and PD‐L1 inhibitor use in head and neck squamous cell carcinoma. Data showed that PD‐1 inhibitors had a significantly lower rate of RECIST progressive disease when compared to PD‐L1 inhibitors.

What this study adds: Our meta‐analysis describes the efficacy of PD‐1 and PD‐L1 inhibitors in HNSCC and suggests a possible difference in certain RECIST criterion between PD‐1 and PD‐L1 inhibitors. This lays foundation for future work to guide clinical treatment of HNSCC.

B cells imprint adoptively transferred CD8+ T cells with enhanced tumor immunity

BACKGROUND

Adoptive T cell transfer (ACT) therapy improves outcomes in patients with advanced malignancies, yet many individuals relapse due to the infusion of T cells with poor function or persistence. Toll-like receptor (TLR) agonists can invigorate antitumor T cell responses when administered directly to patients, but these responses often coincide with toxicities. We posited that TLR agonists could be repurposed ex vivo to condition T cells with remarkable potency in vivo, circumventing TLR-related toxicity.

METHODS

In this study we investigated how tumor-specific murine CD8+ T cells and human tumor infiltrating lymphocytes (TILs) are impacted when expanded ex vivo with the TLR9 agonist CpG.

RESULTS

Herein we reveal a new way to reverse the tolerant state of adoptively transferred CD8+ T cells against tumors using TLR-activated B cells. We repurposed the TLR9 agonist, CpG, commonly used in the clinic, to bolster T cell-B cell interactions during expansion for ACT. T cells expanded ex vivo from a CpG-treated culture demonstrated potent antitumor efficacy and prolonged persistence in vivo. This antitumor efficacy was accomplished without in vivo administration of TLR agonists or other adjuvants of high-dose interleukin (IL)-2 or vaccination, which are classically required for effective ACT therapy. CpG-conditioned CD8+ T cells acquired a unique proteomic signature hallmarked by an IL-2RαhighICOShighCD39low phenotype and an altered metabolic profile, all reliant on B cells transiently present in the culture. Likewise, human TILs benefitted from expansion with CpG ex vivo, as they also possessed the IL-2RαhighICOShighCD39low phenotype. CpG fostered the expansion of potent CD8+ T cells with the signature phenotype and antitumor ability via empowering a direct B-T cell interaction. Isolated B cells also imparted T cells with the CpG-associated phenotype and improved tumor immunity without the aid of additional antigen-presenting cells or other immune cells in the culture.

CONCLUSIONS

Our results demonstrate a novel way to use TLR agonists to improve immunotherapy and reveal a vital role for B cells in the generation of potent CD8+ T cell-based therapies. Our findings have immediate implications in the clinical treatment of advanced solid tumors.

Effect of immunotherapy time-of-day infusion on overall survival among patients with advanced melanoma in the USA (MEMOIR): a propensity score-matched analysis of a single-centre, longitudinal study

BACKGROUND

The dependence of the adaptive immune system on circadian rhythm is an emerging field of study with potential therapeutic implications. We aimed to determine whether specific time-of-day patterns of immune checkpoint inhibitor infusions might alter melanoma treatment efficacy.

METHODS

Melanoma Outcomes Following Immunotherapy (MEMOIR) is a longitudinal study of all patients with melanoma who received ipilimumab, nivolumab, or pembrolizumab, or a combination of these at a single tertiary cancer centre (Winship Cancer Institute of Emory University, Atlanta, GA, USA). For this analysis, we collected deidentified participant-level data from the MEMOIR database for adults (age ≥18 years) diagnosed with stage IV melanoma between 2012 and 2020. Those who received fewer than four infusions were excluded. Standard of care doses were used, with modifications at the treating physicians' discretion. The primary outcome was overall survival, defined as death from any cause and indexed from date of first infusion of immune checkpoint inhibitor. We calculated the association between overall survival and proportion of infusions of immune checkpoint inhibitors received after 1630 h (a composite time cutoff derived from seminal studies of the immune-circadian rhythm to represent onset of evening) using Cox regression and propensity score-matching on age, Eastern Cooperative Oncology Group performance status, serum lactate dehydrogenase concentration, and receipt of corticosteroids and radiotherapy. Treatment-related adverse events that led to change or discontinuation of immune checkpoint inhibitors were also assessed.

FINDINGS

Between Jan 1, 2012, and Dec 31, 2020, 481 patients with melanoma received treatment with immune checkpoint inhibitors at the study centre, of whom 299 had stage IV disease and were included in this study; median follow-up was 27 months (IQR 14 to 47). In the complete unmatched sample, 102 (34%) patients were female and 197 (66%) were male, with a median age of 61 years (IQR 51 to 72). Every additional 20% of infusions of immune checkpoint inhibitors received after 1630 h (among all infusions received by a patient) conferred an overall survival hazard ratio (HR) of 1·31 (95% CI 1·00 to 1·71; p=0·046). A propensity score-matched analysis of patients who did (n=73) and did not (n=73) receive at least 20% of their infusions of immune checkpoint inhibitors after 1630 h (54 [37%] of 146 patients were women and 92 [63%] were men, with a median age of 58 years [IQR 48 to 68]) showed that having at least 20% of infusions in the evening was associated with shorter overall survival (median 4·8 years [95% CI 3·9 to not estimable] vs not reached; HR 2·04 [1·04 to 4·00; p=0·038]). This result remained robust to multivariable proportional hazards adjustment with (HR 1·80 [1·08 to 2·98; p=0·023]) and without (2·16 [1·10 to 4·25; p=0·025]) inclusion of the complete unmatched study sample. The most common adverse events were colitis (54 [18%] of 299 patients), hepatitis (27 [9%]), and hypophysitis (15 [5%]), and there were no treatment-related deaths.

INTERPRETATION

Our findings are in line with an increasing body of evidence that adaptive immune responses are less robust when initially stimulated in the evening than if stimulated in the daytime. Although prospective studies of the timing of immune checkpoint inhibitor infusions are warranted, efforts towards scheduling infusions before mid-afternoon could be considered in the multidisciplinary management of advanced melanoma.

FUNDING

National Institutes of Health, American Society for Radiation Oncology and Melanoma Research Alliance, and Winship Cancer Institute.

Response and recurrence correlates in individuals treated with neoadjuvant anti-PD-1 therapy for resectable oral cavity squamous cell carcinoma

Neoadjuvant PD-1 blockade may be efficacious in some individuals with high-risk, resectable oral cavity head and neck cancer. To explore correlates of response patterns to neoadjuvant nivolumab treatment and post-surgical recurrences, we analyzed longitudinal tumor and blood samples in a cohort of 12 individuals displaying 33% responsiveness. Pretreatment tumor-based detection of FLT4 mutations and PTEN signature enrichment favors response, and high tumor mutational burden improves recurrence-free survival. In contrast, preexisting and/or acquired mutations (in CDKN2A, YAP1, or JAK2) correlate with innate resistance and/or tumor recurrence. Immunologically, tumor response after therapy entails T cell receptor repertoire diversification in peripheral blood and intratumoral expansion of preexisting T cell clones. A high ratio of regulatory T to T helper 17 cells in pretreatment blood predicts low T cell receptor repertoire diversity in pretreatment blood, a low cytolytic T cell signature in pretreatment tumors, and innate resistance. Our study provides a molecular framework to advance neoadjuvant anti-PD-1 therapy for individuals with resectable head and neck cancer.

Neoadjuvant presurgical PD-1 inhibition in oral cavity squamous cell carcinoma

Oral cavity squamous cell carcinoma (OCSCC) is a prevalent surgically treated subset of head and neck cancer with frequent recurrence and poor survival. Immunotherapy has demonstrated efficacy in recurrent/metastatic head and neck cancer. However, whether antitumor responses could be fostered by neoadjuvant presurgical immunotherapy remains unclear. Using a Simon's two-stage design, we present results of a single-arm phase-II trial where 12 patients with stage II-IVA OCSCC received 3 to 4 biweekly doses of 3 mg/kg nivolumab followed by definitive surgical resection with curative intent. Presurgical nivolumab therapy in this cohort shows an overall response rate of 33% (n = 4 patients; 95% CI: 12%-53%). With a median follow up of 2.23 years, 10 out of 12 treated patients remain alive. Neoadjuvant nivolumab is safe, well-tolerated, and is not associated with delays in definitive surgical treatment in this study. This work demonstrates feasibility and safety for incorporation of nivolumab in the neoadjuvant setting for OCSCC (ClinicalTrials.gov: NCT03021993).

Discovery of LYC-55716: A Potent, Selective, and Orally Bioavailable Retinoic Acid Receptor-Related Orphan Receptor-γ (RORγ) Agonist for Use in Treating Cancer

Retinoic acid receptor-related orphan receptor γ (RORc, RORγ, or NR1F3) is the nuclear receptor master transcription factor that drives the function and development of IL-17-producing T helper cells (Th17), cytotoxic T cells (Tc17), and subsets of innate lymphoid cells. Activation of RORγ+ T cells in the tumor microenvironment is hypothesized to render immune infiltrates more effective at countering tumor growth. To test this hypothesis, a family of benzoxazines was optimized to provide LYC-55716 (37c), a potent, selective, and orally bioavailable small-molecule RORγ agonist. LYC-55716 decreases tumor growth and enhances survival in preclinical tumor models and was nominated as a clinical development candidate for evaluation in patients with solid tumors.

Strategies to Overcome Failures in T-Cell Immunotherapies by Targeting PI3K-δ and -γ

PI3K-δ and PI3K-γ are critical regulators of T-cell differentiation, senescence, and metabolism. PI3K-δ and PI3K-γ signaling can contribute to T-cell inhibition via intrinsic mechanisms and regulation of suppressor cell populations, including regulatory T-cells and myeloid derived suppressor cells in the tumor. We examine an exciting new role for using selective inhibitors of the PI3K δ- and γ-isoforms as modulators of T-cell phenotype and function in immunotherapy. Herein we review the current literature on the implications of PI3K-δ and -γ inhibition in T-cell biology, discuss existing challenges in adoptive T-cell therapies and checkpoint blockade inhibitors, and highlight ongoing efforts and future directions to incorporate PI3K-δ and PI3K-γ as synergistic T-cell modulators in immunotherapy.

Modeling ex vivo tumor-infiltrating lymphocyte expansion from established solid malignancies

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) elicits the regression of metastatic malignancies, yet a low proportion of patients achieve complete durable responses. The high incidence of relapse in these patients highlights the need to better understand mechanisms of tumor escape from T cell control. While melanoma has provided the foundation for developing TIL therapy, much less is known about TIL efficacy and relapse in other malignancies. We sought to investigate TIL characteristics in mouse tumors which have not been studied in this setting. Here, we expanded murine TIL ex vivo in IL-2 from fragments of multiple tumor models, including oral cavity cancer models of varying immunogenicity. Additionally, TIL was expanded from pmel-1 mice bearing B16F10 melanoma, yielding an enriched population of tumor-infiltrating TCR transgenic T cells. Murine TIL are similar to human TIL in that they express high levels of inhibitory receptors (PD-1, Tim-3, etc.) and can be expanded ex vivo in IL-2 extensively. Of clinical relevance, we draw parallels between murine and human oral cavity cancer TIL, evaluating relationships between inhibitory receptor expression and function. This platform can be used by labs even in the absence of clinical specimens or clean cell facilities and will be important to more broadly understand TIL phenotypes across many different malignancies.

Perspectives in immunotherapy: meeting report from the immunotherapy bridge (December 2nd-3rd, 2020, Italy)

Improved understanding of tumor immunology has enabled the development of therapies that harness the immune system and prevent immune escape. Numerous clinical trials and real-world experience has provided evidence of the potential for long-term survival with immunotherapy in various types of malignancy. Recurring observations with immuno-oncology agents include their potential for clinical application across a broad patient population with different tumor types, conventional and unconventional response patterns, durable responses, and immune-related adverse events. Despite the substantial achievements to date, a significant proportion of patients still fail to benefit from current immunotherapy options, and ongoing research is focused on transforming non-responders to responders through the development of novel treatments, new strategies to combination therapy, adjuvant and neoadjuvant approaches, and the identification of biomarkers of response. These topics were the focus of the virtual Immunotherapy Bridge (December 2nd-3rd, 2020), organized by the Fondazione Melanoma Onlus, Naples, Italy, in collaboration with the Society for Immunotherapy of Cancer and are summarised in this report.

Preinvasive Colorectal Lesions of African Americans Display an Immunosuppressive Signature Compared to Caucasian Americans

Background

African Americans (AAs) have higher colorectal cancer (CRC) incidence and mortality rate than Caucasian Americans (CAs). Recent studies suggest that immune responses within CRCs contribute to the disparities. If racially distinct immune signatures are present in the early phases of carcinogenesis, they could be used to develop interventions to prevent or slow disease.

Methods

We selected a convenience sample of 95 patients (48 CAs, 47 AAs) with preinvasive colorectal adenomas from the surgical pathology laboratory at the Medical University of South Carolina. Using immunofluorescent-conjugated antibodies on tissue slides from the lesions, we quantified specific immune cell populations: mast cells (CD117⁺), Th17 cells (CD4⁺RORC⁺), and NK cell ligand (MICA/B) and inflammatory cytokines, including IL-6, IL-17A, and IFN-γ. We compared the mean density counts (MDCs) and density rate ratios (RR) and 95% CI of immune markers between AAs to CAs using negative binomial regression analysis. We adjusted our models for age, sex, clinicopathologic characteristics (histology, location, dysplasia), and batch.

Results

We observed no racial differences in age or sex at the baseline endoscopic exam. AAs compared to CAs had a higher prevalence of proximal adenomas (66% vs. 40%) and a lower prevalence of rectal adenomas (11% vs. 23%) (p =0.04) but no other differences in pathologic characteristics. In age, sex, and batch adjusted models, AAs vs. CAs had lower RRs for cells labeled with IFNγ (RR 0.50 (95% CI 0.32-0.81); p=0.004) and NK cell ligand (RR 0.67 (0.43-1.04); p=0.07). In models adjusted for age, sex, and clinicopathologic variables, AAs had reduced RRs relative to CAs for CD4 (p=0.02), NK cell ligands (p=0.01), Th17 (p=0.005), mast cells (p=0.04) and IFN-γ (p< 0.0001).

Conclusions

Overall, the lower RRs in AAs vs. CAs suggests reduced effector response capacity and an immunosuppressive (‘cold’) tumor environment. Our results also highlight the importance of colonic location of adenoma in influencing these differences; the reduced immune responses in AAs relative to CAs may indicate impaired immune surveillance in early carcinogenesis. Future studies are needed to understand the role of risk factors (such as obesity) in influencing differences in immune responses by race.

Fundamentals of T Cell Metabolism and Strategies to Enhance Cancer Immunotherapy

Emerging reports show that metabolic pathways can be targeted to enhance T cell-mediated immunity to tumors. Yet, tumors consume key metabolites in the host to survive, thus robbing T cells of these nutrients to function and thrive. T cells are often deprived of basic building blocks for energy in the tumor, including glucose and amino acids needed to proliferate or produce cytotoxic molecules against tumors. Immunosuppressive molecules in the host further compromise the lytic capacity of T cells. Moreover, checkpoint receptors inhibit T cell responses by impairing their bioenergetic potential within tumors. In this review, we discuss the fundamental metabolic pathways involved in T cell activation, differentiation and response against tumors. We then address ways to target metabolic pathways to improve the next generation of immunotherapies for cancer patients.

The evolving landscape of immunotherapy in solid tumors

While surgical resection, local and cytotoxic therapies have long formed the basis of cancer care, immunotherapy now plays a key role in supplementing and even replacing these agents in the first line. Here we review the early success of programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 blockade and discuss biomarkers of therapeutic response. We next highlight a select group of novel targets in Phase III trials both as monotherapies and in combination with PD-1 inhibitors. Finally, we discuss innovations which seek to improve outcomes in therapy-resistant solid tumors.

Perspectives in immunotherapy: meeting report from the "Immunotherapy Bridge" (December 4th-5th, 2019, Naples, Italy)

Over the last few years, numerous clinical trials and real-world experience have provided a large amount of evidence demonstrating the potential for long-term survival with immunotherapy agents across various malignancies, beginning with melanoma and extending to other tumours. The clinical success of immune checkpoint blockade has encouraged increasing development of other immunotherapies. It has been estimated that there are over 3000 immuno-oncology trials ongoing, targeting hundreds of disease and immune pathways. Evolving topics on cancer immunotherapy, including the state of the art of immunotherapy across various malignancies, were the focus of discussions at the Immunotherapy Bridge meeting (4-5 December, 2019, Naples, Italy), and are summarised in this report.

Racial disparity in survival of patients diagnosed with early-onset colorectal cancer

Background: Survival is reduced in African–Americans (AAs) diagnosed with colorectal cancer (CRC), especially in those <50 years old, when compared with Caucasian Americans (CAs). Yet, the role of clinicopathologic features of CRCs on racial differences in survival needs further study. Materials & methods: Over 1000 individuals (CA 709, AA 320) diagnosed with CRC were studied for survival via the Cox proportional hazards regression analysis based on race and risk of death in two age groups (<50 or 50+). Results: Risk of death for younger AAs (<50) was elevated compared with younger CAs (hazard ratio [HR] 1.98 [1.26–3.09]). Yet no racial differences in survival was observed in older cohort (50+ years), HR 1.07 (0.88–1.31); p for interaction = 0.01. In younger AAs versus CAs only, colonic location attenuated the risk of death. Conclusion: The tumor location and histology influence the poorer survival observed in younger AAs suggesting these may also influence treatment responses.

The Great Debate at 'Immunotherapy Bridge', Naples, December 5, 2019

As part of the 2019 Immunotherapy Bridge congress (December 4-5, Naples, Italy), the Great Debate session featured counterpoint views from leading experts on six topical issues in immunotherapy today. These were the use of chimeric antigen receptor T cell therapy in solid tumors, whether the Immunoscore should be more widely used in clinical practice, whether antibody-dependent cellular cytotoxicity is important in the mode of action of anticytotoxic T-lymphocyte-associated protein 4 antibodies, whether the brain is immunologically unique or just another organ, the role of microbiome versus nutrition in affecting responses to immunotherapy, and whether chemotherapy is immunostimulatory or immunosuppressive. Discussion of these important topics are summarized in this report.

Identification of human CD4+ T cell populations with distinct antitumor activity

How naturally arising human CD4+ T helper subsets affect cancer immunotherapy is unclear. We reported that human CD4+CD26high T cells elicit potent immunity against solid tumors. As CD26high T cells are often categorized as TH17 cells for their IL-17 production and high CD26 expression, we posited these populations would have similar molecular properties. Here, we reveal that CD26high T cells are epigenetically and transcriptionally distinct from TH17 cells. Of clinical importance, CD26high and TH17 cells engineered with a chimeric antigen receptor (CAR) regressed large human tumors to a greater extent than enriched TH1 or TH2 cells. Only human CD26high T cells mediated curative responses, even when redirected with a suboptimal CAR and without aid by CD8+ CAR T cells. CD26high T cells cosecreted effector cytokines, produced cytotoxic molecules, and persisted long term. Collectively, our work underscores the promise of CD4+ T cell populations to improve durability of solid tumor therapies.

IL6 Fuels Durable Memory for Th17 Cell-Mediated Responses to Tumors

The accessibility of adoptive T-cell transfer therapies (ACT) is hindered by the cost and time required for product development. Here we describe a streamlined ACT protocol using Th17 cells expanded only 4 days ex vivo. While shortening expansion compromised cell yield, this method licensed Th17 cells to eradicate large tumors to a greater extent than cells expanded longer term. Day 4 Th17 cells engrafted, induced release of multiple cytokines including IL6, IL17, MCP-1, and GM-CSF in the tumor-bearing host, and persisted as memory cells. IL6 was a critical component for efficacy of these therapies via its promotion of long-term immunity and resistance to tumor relapse. Mechanistically, IL6 diminished engraftment of FoxP3⁺ donor T cells, corresponding with robust tumor infiltration by donor effector over regulatory cells for the Day 4 Th17 cell product relative to cell products expanded longer durations ex vivo. Collectively, this work describes a method to rapidly generate therapeutic T-cell products for ACT and implicates IL6 in promoting durable immunity of Th17 cells against large, established solid tumors. SIGNIFICANCE: An abbreviated, 4-day ex vivo expansion method licenses Th17 cells to confer long-lived immunity against solid malignancies via induction of systemic IL6 in the host.See related commentary by Fiering and Ho, p. 3795.

Ex vivo blockade of PI3K gamma or delta signaling enhances the antitumor potency of adoptively transferred CD8+ T cells

Adoptive T cell transfer therapy induces objective responses in patients with advanced malignancies. Despite these results, some individuals do not respond due to the generation of terminally differentiated T cells during the expansion protocol. As the gamma and delta catalytic subunits in the PI3K pathway are abundant in leukocytes and involved in cell activation, we posited that blocking both subunits ex vivo with the inhibitor IPI‐145 would prevent their differentiation, thereby increasing antitumor activity in vivo. However, IPI‐145 treatment generated a product with reduced antitumor activity. Instead, T cells inhibited of PI3Kγ (IPI‐549) or PI3Kδ (CAL‐101 or TGR‐1202) alone were more potent in vivo. While T cells coinhibited of PI3Kγ and PI3Kδ were less differentiated, they were functionally impaired, indicated by reduced production of effector cytokines after antigenic re‐encounter and decreased persistence in vivo. Human CAR T cells expanded with either a PI3Kγ or PI3Kδ inhibitor possessed a central memory phenotype compared to vehicle cohorts. We also found that PI3Kδ‐inhibited CARs lysed human tumors in vitro more effectively than PI3Kγ‐expanded or traditionally expanded CAR T cells. Our data imply that sole blockade of PI3Kγ or PI3Kδ generates T cells with remarkable antitumor properties, a discovery that has substantial clinical implications.

Inhibition of PI3Kδ improves tumor specific T cell immunity and metabolic fitness

Durable responses have been observed with adoptive T cell therapy (ACT) in some patients. However, current protocols used to expand T cells often exhibit suboptimal tumor control. Failure in these therapies has been attributed to premature differentiation and impaired metabolism of the infused T cells. Previous work done in our lab showed that reduced PI3Kδ signaling improved ACT. Because PI3Kγ and PI3Kδ have critical regulatory roles in T cell differentiation and function, we tested whether inhibiting PI3Kγ could recapitulate or synergize PI3Kδ blockade. To test this, we primed melanoma specific CD8+ pmel-1 T cells in the presence of PI3Kγ (IPI-459), PI3Kδ (CAL101 or TGR-1202) or PI3Kγ/δ (IPI-145) inhibitors and infused them into B16F10 tumor bearing mice. Sole inhibition of PI3Kδ or PI3Kγ in vitro promoted greater tumor immunity and survival compared to dual inhibition. To understand how PI3Kδ or PI3Kγ blockade improved T cell therapy, we assessed their phenotype. CAL101 treatment produced more CD62Lhi CD44lo T cells compared to IPI-459, while TGR-1202 enriched mostly CD62LhiCD44hi T cells. Because decreased T cell differentiation is associated with mitochondrial metabolism, we focused on CAL101 treated T cells to study their metabolism. We found that CAL101 decreased glucose uptake and increased mitochondrial respiration in vitro, indicating augmented mitochondrial function. These findings indicate that blocking PI3Kδ is sufficient to mediate lasting tumor immunity of adoptively transferred T cells by preventing premature differentiation and improving mitochondrial fitness. Our data suggest that addition of CAL101 to ACT expansion protocols could greatly improve T cell therapies for solid tumors.

CD26 enzymatic activity modulates efficient migration of adoptively transferred cancer-specific T cells to solid tumors

The restricted ability of adoptively transferred T cells to eradicate solid tumors limits their use in some patients. Efforts to improve ACT for solid tumors aim to identify strategies that poise T cells for migration. We have previously identified a specific subset of CD4 T cells which express high levels of the ubiquitous ectoenzyme dipeptidyl peptidase-4 (DPP-4), also known as CD26, that produce a tremendous antitumor response in solid tumors. We therefore sought to investigate the functional importance of CD26 on T cells destined for ACT. We transferred tumor specific CD26+ T cells into melanoma-bearing CD26−/− mice and blocked the CD26 enzymatic activity of the donor cells in vivo with sitagliptin, an established competitive inhibitor of CD26. Sitagliptin-treated mice eventually succumbed to tumor burden, while tumors in untreated mice were ablated, eliciting long-term cures exceeding 4 months. Additional analysis determined that tumor infiltrating donor and host T cells diminished with sitagliptin treatment. A 32-plex cytokine array of peripheral blood plasma from these mice revealed a global diminishment of cytokines and chemokines, signifying that the inflammatory response of the T cells was dampened with sitagliptin treatment. Further experiments examined how CD26+ T cells responded to tumor trafficking signals using a transwell migration assay and found that sitagliptin treatment significantly impaired their migratory capacity. However, sitagliptin did not impair the ability of T cells to mount a functional response to tumor antigen. These data reveal that the enzymatic activity of CD26 is important for the ability of T cells to migrate to malignant sites and supports an effective antitumor response.

RNA binding protein PCBP1 is an intracellular immune checkpoint for shaping T cell responses in cancer immunity

Distinct lineages of T cells can act in response to various environmental cues to either drive or restrict immune-mediated pathology. Here, we identify the RNA binding protein, poly(C)-binding protein 1 (PCBP1) as an intracellular immune checkpoint that is up-regulated in activated T cells to prevent conversion of effector T (Teff) cells into regulatory T (Treg) cells, by restricting the expression of Teff cell-intrinsic Treg commitment programs. This was critical for stabilizing Teff cell functions and subverting immune-suppressive signals. T cell-specific deletion of Pcbp1 favored Treg cell differentiation, enlisted multiple inhibitory immune checkpoint molecules including PD-1, TIGIT, and VISTA on tumor-infiltrating lymphocytes, and blunted antitumor immunity. Our results demonstrate a critical role for PCBP1 as an intracellular immune checkpoint for maintaining Teff cell functions in cancer immunity.

T cells exhibit prolonged immunity against melanoma tumors expressing high, but not low affinity antigens

We seek to identify the intrinsic properties in T cells from patients responsive or not to immunotherapy. Therapeutic efficacy is seen in patients where the immune system attacks ‘hot’ tumors due to their high mutation burden. ‘Cold’ tumors, in contrast, are not effectively recognized by T cells due to low mutation burden or expression of self-antigen. To simulate this clinical scenario, we used two different melanoma models: 1) B16F10 expressing a low affinity peptide (mgp100 = i.e. self-antigen), which represents a cold tumor or 2) B16F10 expressing a high affinity peptide (hgp100 = i.e. neoantigen), which represents a hot tumor. In these tumor-bearing mice, we infused pmel-1 CD8+ T cells expressing a TCR that recognizes gp100 peptide on B16F10 melanoma. We hypothesized that the function and persistence of adoptively transferred (ACT) cells would be increased in responsive tumors compared to unresponsive. Our findings show that pmel-1 were less exhausted and persisted more in mice bearing responsive tumors. In these mice, efficiency was observed as shrinkage of large subcutaneous tumors post ACT treatment and enhanced long-term survival. Interestingly, mice bearing hot tumors had metabolically improved pmel-1 cells, demonstrated by their ability to take up glucose and mitochondrial health. Mice that were cured from bearing responsive tumors were protected when rechallenged with both cold and hot tumors simultaneously, implicating a memory response. Herein, we underscore how tumor antigen affinity can drastically change the fate and memory of T cells.

IL-6 fuels durable memory for Th17 cell-mediated responses to tumors

Accessibility of T cell transfer therapies is hindered by cost and time required for product development. We found that shortening ex vivo expansion of Th17 cells licenses a proinflammatory cell product which induces cytokine storm with high levels of systemic IL-6 in tumor-bearing hosts. Unique from other helper subsets, briefly expanded Th17 cells eradicate large tumors in low doses and generate long-lived memory against tumor rechallenge, suggesting a benefit to the inflammatory state. As the toxicity of cytokine release is managed in patients through IL-6 blockade, we addressed the physiologic impact of IL-6 on efficacy and durability of Th17 cell therapy in this immunocompetent model. We hypothesized that peak IL-6 induced by Th17 cells was critical to their durable memory properties. To address this, we used the TRP-1 transgenic mouse model where CD4+ T cells express a TCR that recognizes TRP-1 of B16F10 melanoma. Acute IL-6 blockade post Th17 transfer did not impact the primary antitumor response, yet abrogated long-term responses by promoting tumor relapse upon secondary challenge. Mechanistically, IL-6 blockade reduced pSTAT3 and Bcl2 in transferred T cells and promoted a greater frequency of FoxP3+ Treg cells in the peripheral blood and tumor-draining lymph nodes. Finally, serum IL-6 was inversely correlated with engraftment of tumor-specific Tregs from the transferred product. Overall, short-term expanded Th17 cells uniquely induce IL-6, which promotes Th17 survival, suppresses engraftment of tumor-specific Tregs, and is critical to durable memory. This work may suggest that the universal strategy to inhibit IL-6 during cytokine release syndrome may come at the expense of long-term efficacy for cell therapy.

Immunological effects of nivolumab immunotherapy in patients with oral cavity squamous cell carcinoma

BACKGROUND

Although checkpoint blockades have become widely used, the immunological impact in cancer patients, especially those with oral cavity squamous cell carcinoma (OCSCC), has not been well studied.

METHODS

The present study assessed the immunological impact of anti-PD-1 (nivolumab) treatment in 10 patients with OCSCC. This involved phenotypic analyses of peripheral blood T-cell subpopulations and their expression of immune mediators prior to and following nivolumab treatment. The focus was on immunological effects of treatment without regard to possible clinical responses.

RESULTS

Nivolumab caused a decline in the frequency of blood CD4+ cells but did not affect their expression of IFN-γ. However, nivolumab increased the proportion of CD4+ cells expressing the Treg-supporting factor Foxp3. Nivolumab treatment caused an increase in the proportion of CD8+ cells. While their expression of granzyme B increased, it did not attain significance. Analyses of CD8+ cell subpopulations showed nivolumab caused an increase in levels of unconventional CD8dimCD3+ T-cells. It also caused an increase in expression of granzyme B by these unconventional T-cells as well as by the conventional CD8hiCD3+ cells. The CD8hiCD3+ subpopulation also had a near-significant increase in IFN-γ expression. Treatment with nivolumab had no effect on the levels of the NK containing CD8dimCD3- subpopulation of cells or their expression of IFN-γ or granzyme B.

CONCLUSIONS

These results show nivolumab causes opposing effects on CD4+ and CD8+ cell populations, with CD4+ cell levels declining but increasing the proportion of Treg cells, and unconventional CD8+ T-cell levels increasing with increased expression of immune mediators by CD8+ T-cell subpopulations.

Perspectives in immunotherapy: meeting report from the "Immunotherapy Bridge 2018" (28-29 November, 2018, Naples, Italy)

Immunotherapy is now widely established as a potent and effective treatment option across several types of cancer. However, there is increasing recognition that not all patients respond to immunotherapy, focusing attention on the immune contexture of the tumor microenvironment (TME), drivers of the immune response and mechanisms of tumor resistance to immunity. The development of novel immunotherapeutics and their use in combination with checkpoint inhibitors and other standard of care and novel treatment modalities is an area of particular attention across several tumor types, including melanoma, lung, ovarian, breast, pancreatic, renal, head and neck, brain and non-melanoma skin cancers. The 4th Immunotherapy Bridge meeting (28-29 November, 2018, Naples, Italy) focused on a wide range of evolving topics and trends in the field of cancer immunotherapy and key presentations from this meeting are summarised in this report.

Genomics meets immunity in pancreatic cancer: Current research and future directions for pancreatic adenocarcinoma immunotherapy

Pancreatic adenocarcinoma (PDAC) remains a formidable disease that needs improved therapeutic strategies. Even though immunotherapy has revolutionized treatment for various solid tumor types, it remains largely ineffective in treating individuals with PDAC. This review describes how the application of genome-wide analysis is revitalizing the field of PDAC immunotherapy. Major themes include new insights into the body’s immune response to the cancer, and key immunosuppressive elements that blunt that antitumor immunity. In particular, new evidence indicates that T cell-based antitumor immunity against PDAC is more common, and more easily generated, than previously thought. However, equally common are an array of cellular and molecular defenses employed by the tumor against those T cells. These discoveries have changed how current immunotherapies are deployed and have directed development of novel strategies to better treat this disease. Thus, the impact of genomic analysis has been two-fold: both in demonstrating the heterogeneity of immune targets and defenses in this disease, as well as providing a powerful tool for designing and identifying personalized therapies that exploit each tumor’s unique phenotype. Such personalized treatment combinations may be the key to developing successful immunotherapies for pancreatic adenocarcinoma.