Timed Regulation of 3BP2 Induction Is Critical for Sustaining CD8+ T Cell Expansion and Differentiation

Successful anti-viral response requires the sustained activation and expansion of CD8⁺ T cells for periods that far exceed the time limit of physical T cell interaction with antigen-presenting cells (APCs). The expanding CD8⁺ T cell pool generates the effector and memory cell populations that provide viral clearance and long-term immunity, respectively. Here, we demonstrate that 3BP2 is recruited in cytoplasmic microclusters and nucleates a signaling complex that facilitates MHC:peptide-independent activation of signaling pathways downstream of the TCR. We show that induction of the adaptor molecule 3BP2 is a sensor of TCR signal strength and is critical for sustaining CD8⁺ T cell proliferation and regulating effector and memory differentiation.

Dimitriou et al. show that the adaptor protein 3BP2 lowers the threshold of T cell activation and that the induction of the 3BP2 signaling module at later time points may serve to recapitulate and prolong the biochemical signals emanating from the TCR required for sustained MHC:peptide-independent T cell proliferation.

Efficacy of adoptive therapy with tumor-infiltrating lymphocytes and recombinant interleukin-2 in advanced cutaneous melanoma: a systematic review and meta-analysis

Adoptive cell therapy (ACT) using autologous tumor-infiltrating lymphocytes (TIL) has been tested in advanced melanoma patients at various centers. We conducted a systematic review and meta-analysis to assess its efficacy on previously treated advanced metastatic cutaneous melanoma. The PubMed electronic database was searched from inception to 17 December 2018 to identify studies administering TIL-ACT and recombinant interleukin-2 (IL-2) following non-myeloablative chemotherapy in previously treated metastatic melanoma patients. Objective response rate (ORR) was the primary end point. Secondary end points were complete response rate (CRR), overall survival (OS), duration of response (DOR) and toxicity. Pooled estimates were derived from fixed or random effect models, depending on the amount of heterogeneity detected. Analysis was carried out separately for high dose (HD) and low dose (LD) IL-2. Sensitivity analyses were carried out. Among 1211 records screened, 13 studies (published 1988 - 2016) were eligible for meta-analysis. Among 410 heavily pretreated patients (some with brain metastasis), 332 received HD-IL-2 and 78 LD-IL-2. The pooled overall ORR estimate was 41% [95% confidence interval (CI) 35% to 48%], and the overall CRR was 12% (95% CI 7% to 16%). For the HD-IL-2 group, the ORR was 43% (95% CI 36% to 50%), while for the LD-IL-2 it was 35% (95% CI 25% to 45%). Corresponding pooled estimates for CRR were 14% (95% CI 7% to 20%) and 7% (95% CI 1% to 12%). The majority of HD-IL-2 complete responders (27/28) remained in remission during the extent of follow-up after CR (median 40 months). Sensitivity analyses yielded similar results. Higher number of infused cells was associated with a favorable response. The ORR for HD-IL-2 compared favorably with the nivolumab/ipilimumab combination following anti-PD-1 failure. TIL-ACT therapy, especially when combined with HD-IL-2, achieves durable clinical benefit and warrants further investigation. We discuss the current position of TIL-ACT in the therapy of advanced melanoma, particularly in the era of immune checkpoint blockade therapy, and review future opportunities for improvement of this approach.

Malt1 Protease Deficiency in Mice Disrupts Immune Homeostasis at Environmental Barriers and Drives Systemic T Cell-Mediated Autoimmunity

The paracaspase Malt1 is a key regulator of canonical NF-κB activation downstream of multiple receptors in both immune and nonimmune cells. Genetic disruption of Malt1 protease function in mice and MALT1 mutations in humans results in reduced regulatory T cells and a progressive multiorgan inflammatory pathology. In this study, we evaluated the altered immune homeostasis and autoimmune disease in Malt1 protease-deficient (Malt1PD) mice and the Ags driving disease manifestations. Our data indicate that B cell activation and IgG1/IgE production is triggered by microbial and dietary Ags preferentially in lymphoid organs draining mucosal barriers, likely as a result of dysregulated mucosal immune homeostasis. Conversely, the disease was driven by a polyclonal T cell population directed against self-antigens. Characterization of the Malt1PD T cell compartment revealed expansion of T effector memory cells and concomitant loss of a CD4⁺ T cell population that phenotypically resembles anergic T cells. Therefore, we propose that the compromised regulatory T cell compartment in Malt1PD animals prevents the efficient maintenance of anergy and supports the progressive expansion of pathogenic, IFN-γ-producing T cells. Overall, our data revealed a crucial role of the Malt1 protease for the maintenance of intestinal and systemic immune homeostasis, which might provide insights into the mechanisms underlying IPEX-related diseases associated with mutations in MALT1.

Tumor cell expression of B7-H4 correlates with higher frequencies of tumor-infiltrating APCs and higher CXCL17 expression in human epithelial ovarian cancer

B7-H4, an immune suppressive member of the B7 family, is highly expressed in a wide variety of human malignancies making it an attractive immunotherapeutic target. However, the association between B7-H4 expression in the tumor microenvironment and the immune infiltrate has not been comprehensively examined. To evaluate the immune tumor microenvironment, we analyzed epithelial ovarian tumors from 28 patients using flow cytometry, immunohistochemistry, functional, and genomic analyses. We determined B7-H4 expression patterns and compared the immune infiltrates of tumors with high and low surface expression of B7-H4. Frequencies and phenotypes of tumor and immune cells were determined using multiple flow cytometry panels. Immunohistochemistry was used to analyze cellular infiltration and location. Publicly available datasets were interrogated to determine intratumoral cytokine and chemokine expression. We found that B7-H4 was predominantly expressed by tumor cells in the epithelial ovarian tumor microenvironment. Surface expression of B7-H4 on tumor cells was correlated with higher levels of infiltrating mature antigen-presenting cells. Further, expression of CXCL17, a monocyte and dendritic cell chemoattractant, correlated strongly with B7-H4 expression. T cells expressed activation markers, but T cells expressing a combination of markers associated with T cell activation/exhaustion phenotype were not prevalent. Overall, our data suggest that B7-H4 is associated with a pro-inflammatory tumor microenvironment.

Generation and molecular recognition of melanoma-associated antigen-specific human γδ T cells

Antigen recognition by T cells bearing αβ T cell receptors (TCRs) is restricted by major histocompatibility complex (MHC). However, how antigens are recognized by T cells bearing γδ TCRs remains unclear. Although γδ T cells can recognize nonclassical MHC, it is generally thought that recognition of antigens is not MHC restricted. Here, we took advantage of an in vitro system to generate antigen-specific human T cells and show that melanoma-associated antigens, MART-1 and gp100, can be recognized by γδ T cells in an MHC-restricted fashion. Cloning and transferring of MART-1-specific γδ TCRs restored the specific recognition of the initial antigen MHC/peptide reactivity and conferred antigen-specific functional responses. A crystal structure of a MART-1-specific γδ TCR, together with MHC/peptide, revealed distinctive but similar docking properties to those previously reported for αβ TCRs, recognizing MART-1 on HLA-A*0201. Our work shows that antigen-specific and MHC-restricted γδ T cells can be generated in vitro and that MART-1-specific γδ T cells can also be found and cloned from the naïve repertoire. These findings reveal that classical MHC-restricted human γδ TCRs exist in the periphery and have the potential to be used in developing of new TCR-based immunotherapeutic approaches.

Choline acetyltransferase-expressing T cells are required to control chronic viral infection

Although widely studied as a neurotransmitter, T cell-derived acetylcholine (ACh) has recently been reported to play an important role in regulating immunity. However, the role of lymphocyte-derived ACh in viral infection is unknown. Here, we show that the enzyme choline acetyltransferase (ChAT), which catalyzes the rate-limiting step of ACh production, is robustly induced in both CD4⁺ and CD8⁺ T cells during lymphocytic choriomeningitis virus (LCMV) infection in an IL-21-dependent manner. Deletion of Chat within the T cell compartment in mice ablated vasodilation in response to infection, impaired the migration of antiviral T cells into infected tissues, and ultimately compromised the control of chronic LCMV clone 13 infection. Our results reveal a genetic proof of function for ChAT in T cells during viral infection and identify a pathway of T cell migration that sustains antiviral immunity.

Abstract CT124: Sitravatinib and nivolumab in oral cavity cancer window of opportunity study (SNOW)

Background: Squamous cell carcinoma of the oral cavity (SCCOC) often presents at early stages but its prognosis remains guarded, with a 5-year survival rate of 60% despite curative-intent therapies. Preoperative window-of-opportunity (WOO) studies in resectable SCCOC enable pharmacodynamic evaluation of molecular endpoints without compromising curative-intent treatment. Preoperative nivolumab in SCCOC was safe and showed promising tumor responses in CheckMate-358 WOO study (Ferris et al. ESMO 2017, LBA46). Sitravatinib, a receptor tyrosine kinase inhibitor which potently inhibits Tyro, AXL, Mer, and VEGF family of receptors, has shown encouraging results when combined with nivolumab in non-small cell lung cancer patients who have progressed on anti-PD-1 agents (Leal et al. ESMO 2018, 1129O). We hypothesize that sitravatinib and nivolumab have synergistic antitumor and immunogenic effects by increasing tumor immune infiltration and by blocking oncogenic pathways implicated in disease progression and immune-checkpoint resistance.

Methods: Trial design: SNOW is a single-center, non-randomized WOO study of preoperative sitravatinib and nivolumab in patients with resectable SCCOC. Sitravatinib 120 mg is given orally once daily from day 1 until 48h before surgery or for a maximum period of 28 days. Nivolumab 240mg is given intravenously on day 15 for one dose only. Surgery is planned between days 23-30 following study treatment initiation. Fresh tumor biopsies and serial blood samples for extensive immunophenotyping and evaluation of other pharmacodynamic biomarkers, as well as clinical photographs of the tumor, are collected at baseline, on day 15 prior to nivolumab and at the time of surgery. 18FAZA-PET scans are performed at baseline and before surgery.

Key eligibility criteria: previously untreated and resectable SCCOC; T2-4a, N0-2 or T1 (greater than 1 cm)-N2; no history of tumor bleeding or invasion of major vessels; adequate organ function; no autoimmune disorders; no immunosuppressive therapy.

Study objectives: primary objective is to evaluate the immune and pharmacodynamic effects of sitravatinib plus nivolumab. Secondary objectives are: safety and tolerability including toxicity, rate of surgery completion within the planned window and rate of postoperative complications; antitumor activity including rate of complete pathological response; pharmacokinetics of sitravatinib alone and in combination with nivolumab.

Correlative studies: tumor and blood immunophenotyping, tumor genome and transcriptome analysis, changes in intratumoral hypoxia based on 18FAZA-PET testing. Sample size: SNOW is a proof-of-concept study with no specific statistical assumptions at trial onset. We plan to enroll 12-15 patients evaluable for correlative studies.

Study activation: Aug 30th, 2018. Two patients enrolled as of Jan 10th2019.

Clinical trial identification: NCT03575598.

Citation Format: Marc Oliva Bernal, Douglas Chepeha, Amy Prawira, Douglass Vines, Anna Spreafico, Scott Bratman, John De Almeida, Aaron Hansen, David Goldstein, Ralph Gilbert, Patrick Gullane, Dale H. Brown, Ilan Weinreb, Bayardo Perez-Ordoñez, Pamela S. Ohashi, Tracy McGaha, Ben X. Wang, Jonathan Irish, Isan Chen, Lillian L. Siu. Sitravatinib and nivolumab in oral cavity cancer window of opportunity study (SNOW) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT124.

Abstract 568: Decoding shared antigenic epitopes and their cognate TCR genes in melanoma TILs using a library of paired human cell-based pHLA multimers and artificial APCs

HLA-restricted T cell responses toward immunogenic peptides, whether mutated or non-mutated, can induce antitumor responses in patients with advanced cancer. The fact that potential non-mutated antigens are greater in number than mutated antigens by multiple orders of magnitude and the high polymorphism of HLA genes may have hampered comprehensive analyses of the specificity of antitumor T cell responses toward non-mutated antigens than mutated antigens. Unlike shared antigens, the vast majority of neoantigens are not shared and are unique to each patient. The elucidation of T cell epitopes derived from shared antigens may facilitate the robust development of an efficacious and safe adoptive T cell therapy that is readily available to a larger cohort of cancer patients. It is well established that melanoma tumor-infiltrating T lymphocytes (TILs) contain antitumor T cells that are specific for both non-mutated and mutated antigens. The adoptive transfer of TILs can induce sustained clinical responses in some patients with advanced melanoma. However, a precise and extensive understanding of the shared antigen targets of TILs has been lacking. In this study, TILs were isolated from 8 metastatic melanoma patients, polyclonally expanded in vitro, and their shared antigen specificities for all 45 (25 different) class I alleles were examined. The combination of structure-based analysis using human cell-based peptide/HLA (pHLA) multimers and functional analysis using artificial antigen-presenting cells (APCs) were used to determine antigen-specific T cell responses. We were able to determine the specificity of 12.2 ± 7.2% (mean ± SD, max 25.8%, min 4.6%) of CD8+ T cells in an expanded TIL culture toward 3.0 ± 1.8 (mean ± SD, max 6, min 1) previously known or novel peptides derived from shared antigens. Furthermore, we isolated a number of cognate TCR genes with potent tumor reactivity from the CD8+ T cells. The strategy employed in this study using a library of paired human cell-based pHLA multimers and artificial APCs has enabled us to decipher the antigen specificity of tumor-specific T cells for any given HLA class I allele, regardless of allele frequency and for an infinite number of peptides. It has also allowed us to build a large database of class I-restricted peptides and cognate tumor-reactive TCR genes at an unprecedented scale. This database will be a valuable tool in defining the immune response at the level of each individual cancer patient with precision as well as the identification and validation of biomarkers to aid in patient-based selection of a cancer immunotherapy regimen. Furthermore, this database will help the robust development of novel cancer vaccines and TCR gene therapies for patients with a low mutation burden.

Citation Format: Kenji Murata, Kayoko Saso, Linh T. Nguyen, Douglas Millar, Marcus O. Butler, Pamela S. Ohashi, Naoto Hirano. Decoding shared antigenic epitopes and their cognate TCR genes in melanoma TILs using a library of paired human cell-based pHLA multimers and artificial APCs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 568.

Bone metastases as predictors of treatment response and rapidly progressive disease in NSCLC patients on PD-1/PD-L1 immune checkpoint inhibitors (ICI)

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Background: The tissue microenvironment associated with specific organ metastases potentially influences the efficacy of checkpoint inhibitors. The presence of liver metastases is a predictor of poor response and survival in melanoma and is correlated with reduced CD8+ T cell infiltration. Our study examined clinicopathologic characteristics, focusing on sites of metastatic disease, that are associated with poor outcomes. Methods: Advanced NSCLC patients treated with ≥1 cycle of ICI were reviewed. Baseline age, sex, histology, stage, smoking status, ethnicity, PD-L1 expression and sites of metastases were recorded. Best overall response (BOR) was determined by clinical imaging response and categorized ordinally as shrinkage, stable, or progression, adapted from RECIST for CR/PR, SD, PD. A rapidly progressive phenotype (RPP) was defined as BOR of progression and ICI use of ≤2 months. The association between sites of metastases and clinical outcomes were investigated using logistic and cox regression models. Results: Among 219 eligible patients, bone was the most common metastatic site (34.7%), followed by brain (21.5%), adrenals (14.2%), and liver (13.7%). Bone metastases (OR 0.45, p = 0.004) were associated with a worse BOR, while only a trend was observed for liver metastases (OR 0.47, p = 0.06). Adrenal metastases were associated with a better BOR (OR 2.08, p = 0.04). But thorax limited disease did not associate with BOR (OR 1.08, p = 0.76). In a multivariate model, bone was the only metastatic site associated with a worse BOR (OR 0.50, p = 0.01). Further, bone metastases were associated with RPP (adjusted OR 1.91, p = 0.04). Both bone (adjusted hazard ratio/aHR 1.61, p = 0.01) and liver metastases (aHR 1.80, p = 0.02) were associated with a shorter time-to-treatment-failure. The presence of liver (aHR 2.63, p < 0.001) but not bone (aHR 1.04, p = 0.86) metastases was a significant predictor of poor OS. Conclusions: We report a novel finding that the presence of bone metastases was associated with a worse clinical overall response on ICI and a rapidly progressive phenotype. Further investigations into the mechanisms of RPP in the presence of bone metastases are needed.

Effect of minimal lymphodepletion prior to ACT with TBI-1301, NY-ESO-1 specific gene-engineered TCR-T cells, on clinical responses and CRS

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Background: Adoptive transfer of T cell receptor (TCR) gene-engineered T cells can induce durable anti-cancer responses. Post-infusion cytokine release syndrome (CRS) has been associated with clinical utility. Pre-infusion lymphodepletion (LD) may influence CRS, graft persistence, and clinical responses. While the optimal LD regimen is not yet defined, most include both cyclophosphamide (CY) and fludarabine (FLU). TBI-1301 is a novel gene therapy produced by engineering autologous lymphocytes to express an NY-ESO-1-specific TCR using a retrovirus vector that encodes siRNA to silence endogenous TCR. Since less intensive LD may be sufficient with the use of this novel vector, we are conducting a study where patients are treated with TBI-1301 following LD with CY alone. Methods: Eligibility includes informed consent, HLA-A*02:01 or A*02:06 haplotype, and NY-ESO-1 expression by immunohistochemistry. Eligible patients undergo harvest of PBMC which are then processed locally to generate engineered TBI-1301 cells. The study design is to infuse 5x109 cells (day 0) to patients following LD with CY (750 mg/m2 on day -3 and -2). Endpoints include safety, efficacy, and biological correlates for persistence of NY-ESO-1-specific T cells post infusion. Results: Thus far, 9 patients have been treated, and 8 have received the target dose. To date, 8 patients are evaluable for response and toxicity, and no DLTs have been observed. Despite LD with CY alone, all 4 patients with synovial sarcoma and 1 with melanoma experienced clinical and laboratory evidence of grade 1-2 CRS with increased CRP, ferritin, and IL-6 levels. CRS resolved spontaneously in all but one patient who required tocilizumab due to grade 2 nausea/vomiting. Two subjects experienced grade 3 tumor-associated pain. Other treatment-associated grade 3 or 4 toxicities included neutropenia and hypophosphatemia. Best overall response by RECIST is as follows: 2 partial responses, 5 stable disease, and 1 progressive disease. Biomarker analysis demonstrates persistence of transferred TBI-1301 cells, > 100 days in some patients. Conclusions: TBI-1301 appears to be safe and to possess anti-tumor activity. Despite LD with CY alone, grade 1-2 CRS is induced. Additional cohorts to this study will examine the role of repeat infusions to enhance anti-tumor activity. Clinical trial information: NCT02869217.

Bespoke circulating tumor DNA (ctDNA) analysis as a predictive biomarker in solid tumor patients (pts) treated with single-agent pembrolizumab (P)

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Background: Limited data exist in the clonal dynamics of serial ctDNA as a predictive biomarker in advanced solid tumor pts receiving immune checkpoint blockade. Methods: Pts with mixed solid tumors received single agent P (anti-PD-1) 200 mg IV Q3wks in the investigator-initiated phase II INSPIRE trial (NCT02644369). ctDNA was assayed at baseline (B) and start of cycle 3 (C3) using a pt-specific amplicon-based NGS assay (Signatera™). Samples were considered ctDNA positive if ≥2 of 16 pt-specific targets met the qualifying confidence score threshold. Results: Results of 70 pts are presented. Demographics: male 46%; median age=60 yrs (range 21–82); head and neck (20%), triple negative breast (14%) and ovarian (14%) cancers comprised the major malignancies. Median no. of P cycles=4 (range 2–35); follow up was 14m (range 2–29); RECIST responses: CR 2.9% (n=2), PR 17% (n=12), CBR (CR+PR+SD≥6 cycles) 31% (n=22), RECIST/clinical PD (n=43/10; 65%/15%). Median PFS=3.3m and median OS=17.8m. 68/70 pts had ctDNA detected at baseline (median=16/16 variants) demonstrating 97% sensitivity. Table shows correlation of ΔctDNA (ctDNAB compared to ctDNAC3) with clinical efficacy parameters, whereas ctDNAB values did not reach statistical significance. Conclusions: A strong correlation exists between ΔctDNA with OS, PFS, CBR and ORR with P, suggesting it is a potential predictive biomarker in pts with mixed solid tumors. Clinical trial information: NCT02644369. [Table: see text]

Myeloid immunosuppressive state as a predictor of rapidly progressive phenotype and poor survival in advanced non-small cell lung cancer (NSCLC) patients treated with PD-1/PD-L1 inhibitors

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Background: Immune subpopulations within the tumor microenvironment (TME) play a central role in determining response to checkpoint inhibitors. Myeloid derived suppressor cells, a heterogeneous population of immature myeloid cells, have a predominantly immunosuppressive role by stimulating T regulatory cells. We hypothesize that elevated myeloid-to-lymphocyte measures in the peripheral blood predict for greater numbers of myeloid derived suppressor cells in the TME and worse outcomes. Methods: In advanced NSCLC patients who received immunotherapy between 2010-2018, baseline characteristics collected retrospectively included age, sex, histology, stage, smoking status, ethnicity, PD-L1 expression and tumor genotype. Pre-treatment neutrophil/lymphocyte (NLR) and monocyte/lymphocyte ratios (MLR) were log transformed and analyzed using cox and logistic regression models. Results: Among 219 eligible patients, a high NLR was associated with shorter time-to-treatment-failure (HR 1.38, 95%CI 1.09-1.75, p = 0.008) and poorer OS (HR 1.62, 95%CI 1.23-2.14, p < 0.001), independent of PD-L1 levels. Disproportionate increases in NLR and MLR were highly correlated (Spearman’s rho = 0.78). Further, higher NLR (p = 0.09) or MLR (p = 0.06) tended to associate with best overall response (BOR) to immunotherapy, with higher rates of progressive disease (PD) and lower rates of clinical response. A high NLR (p = 0.01) and MLR (p = 0.02) were associated with a rapidly progressive phenotype defined by PD as the BOR and duration of therapy ≤2 months. This remained significant after adjusting for confounders in a multivariate model (p = 0.03 for NLR and p = 0.03 for MLR). No associations were observed between high myeloid counts and other clinical prognostic factors such as liver metastases. Conclusions: A myeloid immunosuppressive state characterized by a disproportionate increase in peripheral immune myeloid populations is significantly associated with primary refractory disease, rapidly progressive phenotype, and poorer survival. Further investigation into myeloid mediated mechanisms of resistance is warranted.

Phase II clinical trial of adoptive cell therapy for patients with metastatic melanoma with autologous tumor-infiltrating lymphocytes and low-dose interleukin-2

Adoptive cell therapy using autologous tumor-infiltrating lymphocytes (TIL) has shown significant clinical benefit, but is limited by toxicities due to a requirement for post-infusion interleukin-2 (IL-2), for which high dose is standard. To assess a modified TIL protocol using lower dose IL-2, we performed a single institution phase II protocol in unresectable, metastatic melanoma. The primary endpoint was response rate. Secondary endpoints were safety and assessment of immune correlates following TIL infusion. Twelve metastatic melanoma patients were treated with non-myeloablative lymphodepleting chemotherapy, TIL, and low-dose subcutaneous IL-2 (125,000 IU/kg/day, maximum 9-10 doses over 2 weeks). All but one patient had previously progressed after treatment with immune checkpoint inhibitors. No unexpected adverse events were observed, and patients received an average of 6.8 doses of IL-2. By RECIST v1.1, two patients experienced a partial response, one patient had an unconfirmed partial response, and six had stable disease. Biomarker assessment confirmed an increase in IL-15 levels following lymphodepleting chemotherapy as expected and a lack of peripheral regulatory T-cell expansion following protocol treatment. Interrogation of the TIL infusion product and monitoring of the peripheral blood following infusion suggested engraftment of TIL. In one responding patient, a population of T cells expressing a T-cell receptor Vβ chain that was dominant in the infusion product was present at a high percentage in peripheral blood more than 2 years after TIL infusion. This study shows that this protocol of low-dose IL-2 following adoptive cell transfer of TIL is feasible and clinically active. (ClinicalTrials.gov identifier NCT01883323.).

Phase I study of local radiation and tremelimumab in patients with inoperable locally recurrent or metastatic breast cancer

Immunotherapy has shown modest activity in metastatic breast cancer (MBC). In this phase I dose escalation study, we assessed safety of tremelimumab, a humanized anti-CTLA4 monoclonal antibody, at starting dose 3 mg/kg, on the third day of palliative radiotherapy (2000cGy in 5 daily fractions) in patients with MBC. Primary objective was to determine the maximum tolerated dose (MTD) of tremelimumab combined with RT. Secondary objective was to assess response. Among 6 patients enrolled between July 2010 and October 2011, 5 had hormone receptor-positive MBC, 1 had triple negative MBC. Median age was 45 years. Common toxicities included lymphopenia (83%), fatigue (50%) and rash (33%). One dose-limiting toxicity occurred at 6 mg/kg, however the trial closed before MTD could be determined. One patient discontinued treatment due to a pathological fracture. Best response was stable disease (SD), 1 patient had SD for >6 months. Median follow up was 27.0 months. Median OS was 50.8 months, with 1 patient surviving >8 years. Peripheral blood mononuclear cell (PBMC) profiles showed increasing proliferating (Ki67+) Treg cells 1 week post treatment in 5 patients. Overall, tremelimumab at 3 mg/kg combined with RT appears to be a tolerable treatment strategy. Further studies are needed to optimize this combination approach.

Turning the Tide Against Regulatory T Cells

Regulatory T (Treg) cells play crucial roles in health and disease through their immunosuppressive properties against various immune cells. In this review we will focus on the inhibitory role of Treg cells in anti-tumor immunity. We outline how Treg cells restrict T cell function based on our understanding of T cell biology, and how we can shift the equilibrium against regulatory T cells. To date, numerous strategies have been proposed to limit the suppressive effects of Treg cells, including Treg cell neutralization, destabilizing Treg cells and rendering T cells resistant to Treg cells. Here, we focus on key mechanisms which render T cells resistant to the suppressive effects of Treg cells. Lastly, we also examine current limitations and caveats of overcoming the inhibitory activity of Treg cells, and briefly discuss the potential to target Treg cell resistance in the context of anti-tumor immunity.

An interim report on the investigator-initiated phase 2 study of pembrolizumab immunological response evaluation (INSPIRE)

Background

Immune checkpoint inhibitors (ICIs) demonstrate unprecedented efficacy in multiple malignancies; however, the mechanisms of sensitivity and resistance are poorly understood and predictive biomarkers are scarce. INSPIRE is a phase 2 basket study to evaluate the genomic and immune landscapes of peripheral blood and tumors following pembrolizumab treatment.

Methods

Patients with incurable, locally advanced or metastatic solid tumors that have progressed on standard therapy, or for whom no standard therapy exists or standard therapy was not deemed appropriate, received 200 mg pembrolizumab intravenously every three weeks. Blood and tissue samples were collected at baseline, during treatment, and at progression. One core biopsy was used for immunohistochemistry and the remaining cores were pooled and divided for genomic and immune analyses. Univariable analysis of clinical, genomic, and immunophenotyping parameters was conducted to evaluate associations with treatment response in this exploratory analysis.

Results

Eighty patients were enrolled from March 21, 2016 to June 1, 2017, and 129 tumor and 382 blood samples were collected. Immune biomarkers were significantly different between the blood and tissue. T cell PD-1 was blocked (≥98%) in the blood of all patients by the third week of treatment. In the tumor, 5/11 (45%) and 11/14 (79%) patients had T cell surface PD-1 occupance at weeks six and nine, respectively. The proportion of genome copy number alterations and abundance of intratumoral 4-1BB+ PD-1+ CD8 T cells at baseline (P < 0.05), and fold-expansion of intratumoral CD8 T cells from baseline to cycle 2–3 (P < 0.05) were associated with treatment response.

Conclusion

This study provides technical feasibility data for correlative studies. Tissue biopsies provide distinct data from the blood and may predict response to pembrolizumab.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0541-0) contains supplementary material, which is available to authorized users.

Immunoscore clinical utility to identify good prognostic colon cancer stage II patients with high-risk clinico-pathological features for whom adjuvant treatment may be avoided

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Background: Immunoscore Colon is an IVD test predicting the risk of relapse in early-stage colon cancer (CC) patients, by measuring the host immune response at the tumor site. It is a risk-assessment tool providing independent and superior prognostic value than the usual tumor risk parameters and is intended to be used as an adjunct to the TNM classification. Risk assessment is particularly important to decide when to propose an adjuvant (adj.) treatment for stage (St) II CC patients. High-risk stage II patients defined as those with poor prognostic features including T4, lymph nodes < 12, poor differentiation, VELIPI, bowel obstruction/perforation can be considered for adj. chemotherapy (CT). However, additional risk factors are needed to guide treatment decisions. Methods: A subgroup analysis was performed on the St II untreated patients (n = 1130) from the Immunoscore international validation study (Pagès The Lancet 2018). The high-risk patients (with at least 1 clinico-pathological high-risk feature) were classified in 2 categories using pre-defined cutoffs: Low Immunoscore versus High Immunoscore and their five-year time to recurrence (5Y TTR) was compared to the TTR of the low-risk patients (without any clinico-pathological high-risk feature). Results: Among the patients with high-risk features (n = 630), 438 (69.5%) had a High Immunoscore with a corresponding 5Y TTR of 87.4 (95% CI 83.9-91.0), statistically similar (logrank pv not stratified p > 0.42, wald pv stratified by center p > 0.20) to the TTR 89.1 (95% CI 86.1-92.1) observed for the 500 low-risk patients (with no clinico-pathological feature). Furthermore, 5Y TTR for these patients were statistically similar to those of St II patients with high-risk features and a High Immunoscore (n = 438), who received adj. CT (n = 162) (5Y TTR of 83.4 (95% CI 77.6-89.9). Conclusions: These data show that despite the presence of high-risk features that usually trigger adj. treatment, when not treated with CT, a significant part of these patients (69.5%) have a recurrence risk similar to the low risk patients. Therefore, the Immunoscore test could be a good tool for adj. treatment decision in St II patients.

In vitro-generated MART-1-specific CD8 T cells display a broader T-cell receptor repertoire than ex vivo naïve and tumor-infiltrating lymphocytes

The differentiation of human hematopoietic stem cells into CD8 T cells can be achieved in vitro with the OP9-DL4 system. We considered that in the absence of medullary thymic epithelial cells, which serve to restrict the breath of the T-cell receptor (TCR) repertoire by expressing tissue-restricted antigens, a distinct repertoire would be generated in vitro. To test this notion, we compared the TCR-Vα/Vβ (TRAV/TRBV) gene usage of major histocompatibility complex-restricted antigen (MART-1)-specific T cells generated in vitro to that from ex vivo naïve T cells and tumor-infiltrating lymphocytes (TILs) using high-throughput DNA sequencing. In contrast to naïve T cells and TILs, which showed the expected narrow TRAV repertoire, in vitro-generated MART-1-specific T cells used almost all TRAV gene families and displayed unique CDR3 lengths. Our work demonstrates that the OP9-DL4 system supports the creation of a broad antigen-specific TCR repertoire, suggesting that T cells generated in vitro may undergo a different set of selection events that otherwise constrains the TCR repertoire of thymus-derived T cells.

Activation of Peroxisome Proliferator-Activated Receptors α and δ Synergizes with Inflammatory Signals to Enhance Adoptive Cell Therapy

Memory CD8⁺ T cells (T_mem) are superior mediators of adoptive cell therapy (ACT) compared with effector CD8⁺ T cells (T_eff) due to increased persistence in vivo. Underpinning T_mem survival is a shift in cellular metabolism away from aerobic glycolysis towards fatty acid oxidation (FAO). Here we investigated the impact of the peroxisome proliferator-activated receptor (PPAR) agonist GW501516 (GW), an agent known to boost FAO in other tissues, on CD8⁺ T-cell metabolism, function, and efficacy in a murine ACT model. Via activation of both PPARα and PPARδ/β, GW treatment increased expression of carnitine palmitoyl transferase 1a, the rate-limiting enzyme of FAO, in activated CD8⁺ T cells. Using a metabolomics approach, we demonstrated that GW increased the abundance of multiple different acylcarnitines, consistent with enhanced FAO. T cells activated in the presence of GW and inflammatory signals, either mature dendritic cells or IL12, also demonstrated enhanced production of IFNγ and expression of T-bet. Despite high expression of T-bet, a characteristic of short-lived effector cells, GW-treated cells demonstrated enhanced persistence in vivo and superior efficacy in a model of ACT. Collectively, these data identify combined PPARα and PPARδ/β agonists as attractive candidates for further studies and rapid translation into clinical trials of ACT. SIGNIFICANCE: Dual activation of peroxisome proliferator-activated receptors α and δ improves the efficacy of adoptive cell therapy by reprogramming T-cell metabolism and cytokine expression.

CapTCR-seq: hybrid capture for T-cell receptor repertoire profiling

Mature T-cell lymphomas consisting of an expanded clonal population of T cells that possess common rearrangements of the T-cell receptor (TCR) encoding genes can be identified and monitored using molecular methods of T-cell repertoire analysis. We have developed a hybrid-capture method that enriches DNA sequencing libraries for fragments encoding rearranged TCR genes from all 4 loci in a single reaction. We use this method to describe the TCR repertoires of 63 putative lymphoma clinical isolates, 7 peripheral blood mononuclear cell (PBMC) populations, and a collection of tumor infiltrating lymphocytes. Dominant Variable (V) and Joining (J) gene pair rearrangements in cancer cells were confirmed by polymerase chain reaction (PCR) amplification and Sanger sequencing; clonality assessment of clinical isolates using BIOMED-2 methods showed agreement for 73% and 77% of samples at the β and γ loci, respectively, whereas β locus V and J allele prevalence in PBMCs were well correlated with results from commercial PCR-based DNA sequencing assays (r 2 = 0.94 with Adaptive ImmunoSEQ, 0.77-0.83 with Invivoscribe LymphoTrack TRB Assay). CapTCR-seq allows for rapid, high-throughput and flexible characterization of dominant clones within TCR repertoire that will facilitate quantitative analysis of patient samples and enhance sensitivity of tumor surveillance over time.

Landscape of genomic alterations in high-grade serous ovarian cancer from exceptional long- and short-term survivors

BACKGROUND

Patients diagnosed with high-grade serous ovarian cancer (HGSOC) who received initial debulking surgery followed by platinum-based chemotherapy can experience highly variable clinical responses. A small percentage of women experience exceptional long-term survival (long term (LT), 10+ years), while others develop primary resistance to therapy and succumb to disease in less than 2 years (short term (ST)). To improve clinical management of HGSOC, there is a need to better characterize clinical and molecular profiles to identify factors that underpin these disparate survival responses.

METHODS

To identify clinical and tumor molecular biomarkers associated with exceptional clinical response or resistance, we conducted an integrated clinical, exome, and transcriptome analysis of 41 primary tumors from LT (n = 20) and ST (n = 21) HGSOC patients.

RESULTS

Younger age at diagnosis, no residual disease post debulking surgery and low CA125 levels following surgery and chemotherapy were clinical characteristics of LT. Tumors from LT survivors had increased somatic mutation burden (median 1.62 vs. 1.22 non-synonymous mutations/Mbp), frequent BRCA1/2 biallelic inactivation through mutation and loss of heterozygosity, and enrichment of activated CD4+, CD8+ T cells, and effector memory CD4+ T cells. Characteristics of ST survival included focal copy number gain of CCNE1, lack of BRCA mutation signature, low homologous recombination deficiency scores, and the presence of ESR1-CCDC170 gene fusion.

CONCLUSIONS

Our findings suggest that exceptional long- or short-term survival is determined by a concert of clinical, molecular, and microenvironment factors.

Landscape of genomic alterations in high-grade serous ovarian cancer from exceptional long- and short-term survivors

Background

Patients diagnosed with high-grade serous ovarian cancer (HGSOC) who received initial debulking surgery followed by platinum-based chemotherapy can experience highly variable clinical responses. A small percentage of women experience exceptional long-term survival (long term (LT), 10+ years), while others develop primary resistance to therapy and succumb to disease in less than 2 years (short term (ST)). To improve clinical management of HGSOC, there is a need to better characterize clinical and molecular profiles to identify factors that underpin these disparate survival responses.

Methods

To identify clinical and tumor molecular biomarkers associated with exceptional clinical response or resistance, we conducted an integrated clinical, exome, and transcriptome analysis of 41 primary tumors from LT (n = 20) and ST (n = 21) HGSOC patients.

Results

Younger age at diagnosis, no residual disease post debulking surgery and low CA125 levels following surgery and chemotherapy were clinical characteristics of LT. Tumors from LT survivors had increased somatic mutation burden (median 1.62 vs. 1.22 non-synonymous mutations/Mbp), frequent BRCA1/2 biallelic inactivation through mutation and loss of heterozygosity, and enrichment of activated CD4+, CD8+ T cells, and effector memory CD4+ T cells. Characteristics of ST survival included focal copy number gain of CCNE1, lack of BRCA mutation signature, low homologous recombination deficiency scores, and the presence of ESR1-CCDC170 gene fusion.

Conclusions

Our findings suggest that exceptional long- or short-term survival is determined by a concert of clinical, molecular, and microenvironment factors.

Electronic supplementary material

The online version of this article (10.1186/s13073-018-0590-x) contains supplementary material, which is available to authorized users.

Landscape of genomic alterations in high-grade serous ovarian cancer from exceptional long- and short-term survivors

BACKGROUND

Patients diagnosed with high-grade serous ovarian cancer (HGSOC) who received initial debulking surgery followed by platinum-based chemotherapy can experience highly variable clinical responses. A small percentage of women experience exceptional long-term survival (long term (LT), 10+ years), while others develop primary resistance to therapy and succumb to disease in less than 2 years (short term (ST)). To improve clinical management of HGSOC, there is a need to better characterize clinical and molecular profiles to identify factors that underpin these disparate survival responses.

METHODS

To identify clinical and tumor molecular biomarkers associated with exceptional clinical response or resistance, we conducted an integrated clinical, exome, and transcriptome analysis of 41 primary tumors from LT (n = 20) and ST (n = 21) HGSOC patients.

RESULTS

Younger age at diagnosis, no residual disease post debulking surgery and low CA125 levels following surgery and chemotherapy were clinical characteristics of LT. Tumors from LT survivors had increased somatic mutation burden (median 1.62 vs. 1.22 non-synonymous mutations/Mbp), frequent BRCA1/2 biallelic inactivation through mutation and loss of heterozygosity, and enrichment of activated CD4+, CD8+ T cells, and effector memory CD4+ T cells. Characteristics of ST survival included focal copy number gain of CCNE1, lack of BRCA mutation signature, low homologous recombination deficiency scores, and the presence of ESR1-CCDC170 gene fusion.

CONCLUSIONS

Our findings suggest that exceptional long- or short-term survival is determined by a concert of clinical, molecular, and microenvironment factors.

Radiation and Heat Improve the Delivery and Efficacy of Nanotherapeutics by Modulating Intratumoral Fluid Dynamics

Nanomedicine drug delivery systems are capable of transporting significant payloads to solid tumors. However, only a modest increase in antitumor efficacy relative to the standard of care has been observed. In this study, we demonstrate that a single dose of radiation or mild hyperthermia can substantially improve tumor uptake and distribution of nanotherapeutics, resulting in improved treatment efficacy. The delivery of nanomedicine was driven by a reduction in interstitial fluid pressure (IFP) and small perturbation of steady-state fluid flow. The transient effects on fluid dynamics in tumors with high IFP was also shown to dominate over immune cell endocytic capacity, another mechanism suspected of improving drug delivery. Furthermore, we demonstrate the specificity of this mechanism by showing that delivery of nanotherapeutics to low IFP tumors with high leukocyte infiltration does not benefit from pretreatment with radiation or heat. These results demonstrate that focusing on small perturbations to steady-state fluid dynamics, rather than large sustained effects or uncertain immune cell recruitment strategies, can impart a vulnerability to tumors with high IFP and enhance nanotherapeutic drug delivery and treatment efficacy.

Regulatory T Cells in Ovarian Cancer Are Characterized by a Highly Activated Phenotype Distinct from that in Melanoma

Purpose: Regulatory T (Treg) cells expressing the transcription factor FOXP3 are essential for the maintenance of immunologic self-tolerance but play a detrimental role in most cancers due to their ability to suppress antitumor immunity. The phenotype of human circulating Treg cells has been extensively studied, but less is known about tumor-infiltrating Treg cells. We studied the phenotype and function of tumor-infiltrating Treg cells in ovarian cancer and melanoma to identify potential Treg cell-associated molecules that can be targeted by tumor immunotherapies.Experimental Design: The phenotype of intratumoral and circulating Treg cells was analyzed by multicolor flow cytometry, mass cytometry, RNA-seq, and functional assays.Results: Treg cells isolated from ovarian tumors displayed a distinct cell surface phenotype with increased expression of a number of receptors associated with TCR engagement, including PD-1, 4-1BB, and ICOS. Higher PD-1 and 4-1BB expression was associated with increased responsiveness to further TCR stimulation and increased suppressive capacity, respectively. Transcriptomic and mass cytometry analyses revealed the presence of Treg cell subpopulations and further supported a highly activated state specifically in ovarian tumors. In comparison, Treg cells infiltrating melanomas displayed lower FOXP3, PD-1, 4-1BB, and ICOS expression and were less potent suppressors of CD8 T-cell proliferation.Conclusions: The highly activated phenotype of ovarian tumor-infiltrating Treg cells may be a key component of an immunosuppressive tumor microenvironment. Receptors that are expressed by tumor-infiltrating Treg cells could be exploited for the design of novel combination tumor immunotherapies. Clin Cancer Res; 24(22); 5685-96. ©2018 AACR.

International validation of the consensus Immunoscore for the classification of colon cancer: a prognostic and accuracy study

BACKGROUND

The estimation of risk of recurrence for patients with colon carcinoma must be improved. A robust immune score quantification is needed to introduce immune parameters into cancer classification. The aim of the study was to assess the prognostic value of total tumour-infiltrating T-cell counts and cytotoxic tumour-infiltrating T-cells counts with the consensus Immunoscore assay in patients with stage I-III colon cancer.

METHODS

An international consortium of 14 centres in 13 countries, led by the Society for Immunotherapy of Cancer, assessed the Immunoscore assay in patients with TNM stage I-III colon cancer. Patients were randomly assigned to a training set, an internal validation set, or an external validation set. Paraffin sections of the colon tumour and invasive margin from each patient were processed by immunohistochemistry, and the densities of CD3+ and cytotoxic CD8+ T cells in the tumour and in the invasive margin were quantified by digital pathology. An Immunoscore for each patient was derived from the mean of four density percentiles. The primary endpoint was to evaluate the prognostic value of the Immunoscore for time to recurrence, defined as time from surgery to disease recurrence. Stratified multivariable Cox models were used to assess the associations between Immunoscore and outcomes, adjusting for potential confounders. Harrell's C-statistics was used to assess model performance.

FINDINGS

Tissue samples from 3539 patients were processed, and samples from 2681 patients were included in the analyses after quality controls (700 patients in the training set, 636 patients in the internal validation set, and 1345 patients in the external validation set). The Immunoscore assay showed a high level of reproducibility between observers and centres (r=0·97 for colon tumour; r=0·97 for invasive margin; p<0·0001). In the training set, patients with a high Immunoscore had the lowest risk of recurrence at 5 years (14 [8%] patients with a high Immunoscore vs 65 (19%) patients with an intermediate Immunoscore vs 51 (32%) patients with a low Immunoscore; hazard ratio [HR] for high vs low Immunoscore 0·20, 95% CI 0·10-0·38; p<0·0001). The findings were confirmed in the two validation sets (n=1981). In the stratified Cox multivariable analysis, the Immunoscore association with time to recurrence was independent of patient age, sex, T stage, N stage, microsatellite instability, and existing prognostic factors (p<0·0001). Of 1434 patients with stage II cancer, the difference in risk of recurrence at 5 years was significant (HR for high vs low Immunoscore 0·33, 95% CI 0·21-0·52; p<0·0001), including in Cox multivariable analysis (p<0·0001). Immunoscore had the highest relative contribution to the risk of all clinical parameters, including the American Joint Committee on Cancer and Union for International Cancer Control TNM classification system.

INTERPRETATION

The Immunoscore provides a reliable estimate of the risk of recurrence in patients with colon cancer. These results support the implementation of the consensus Immunoscore as a new component of a TNM-Immune classification of cancer.

FUNDING

French National Institute of Health and Medical Research, the LabEx Immuno-oncology, the Transcan ERAnet Immunoscore European project, Association pour la Recherche contre le Cancer, CARPEM, AP-HP, Institut National du Cancer, Italian Association for Cancer Research, national grants and the Society for Immunotherapy of Cancer.

Genomic and immune landscape of metastatic melanoma (MM) treated with pembrolizumab (PEM)

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Background: Predictive biomarkers for PEM in MM is an active area of research. Methods: INSPIRE (NCT02644369) is a biomarker-driven Princess Margaret Cancer Centre initiative to evaluate genomic and immunologic changes in tumor and blood of patient (pts) treated with PEM at 200 mg IV Q3W. Baseline (BL) and on treatment (post 2-3 doses of PEM) fresh tumor biopsies were collected for DNA/RNA sequencing, immune-profiling, and tumor PD-L1 expression by immunohistochemistry (QualTek), with longitudinal blood collection for immunophenotyping. Results: As of 9/2017, 11 MM pts (9 cutaneous, 1 choroidal, 1 mucosal) were enrolled. Median treatment duration was 6 months (0.75 – 14.25); 7 pts remain on study. 7/11 (64%) pts had partial response (PR), 3/11 (27%) progressive disease (PD) and 1 was not evaluable (NE) per RECIST 1.1. Based on data for 8 pts (6 PR, 2 PD), higher percentage (%) PD-1 (mean 70 vs 12%), TIGIT (82 vs 43%) and 4-1BB (23 vs 4%) positivity on CD8 T cells in tumor vs blood was seen (all p < 0.05). In BL blood, lower % TIGIT positive CD8 T cells was detected in pts with PR vs PD (38 vs 58%, p < 0.05). T cell profile of 4 pts with paired BL and post PEM samples is shown in Table 1. Mean tumor PD-L1 score was 24% (0 - 90%), with no correlation to PEM response. Genomic analysis on 8 pts (5 PR, 2 PD, 1 NE) found mean tumor mutation burden (TMB) of 538. B2M deletion was seen in 2/2 PD and 0/6 PR pts. Among pts with PRs, 4/6 (67%) had TAP1 and TAP2 amplification post PEM therapy. HLA-A and HLA-B amplifications were each found in 3/6 (50%) PR pts, with only 1 present at BL. TMB was not associated with response to PEM. Conclusions: In this exploratory analysis of MM pts treated with PEM, there was significantly discordant T cell phenotype in tumor vs blood at BL. Our findings suggest B2M deletion to be associated with PEM resistance. The observed development of HLA-A/B and TAP1/2 amplification in 50-67% pts with PR post PEM suggests potential predictive significance, although further validation is warranted. Clinical trial information: NCT02644369. [Table: see text]

Notch Shapes the Innate Immunophenotype in Breast Cancer

Notch activation, which is associated with basal-like breast cancer (BLBC), normally directs tissue patterning, suggesting that it may shape the tumor microenvironment. Here, we show that Notch in tumor cells regulates the expression of two powerful proinflammatory cytokines, IL1β and CCL2, and the recruitment of tumor-associated macrophages (TAM). Notch also regulates TGFβ-mediated activation of tumor cells by TAMs, closing a Notch-dependent paracrine signaling loop between these two cell types. We use a mouse model in which Notch can be regulated in spontaneous mammary carcinoma to confirm that IL1β and CCL2 production, and macrophage recruitment are Notch-dependent. In human disease, expression array analyses demonstrate a striking association between Notch activation, IL1β and CCL2 production, macrophage infiltration, and BLBC. These findings place Notch at the nexus of a vicious cycle of macrophage infiltration and amplified cytokine secretion and provide immunotherapeutic opportunities in BLBC.Significance: BLBC is aggressive and has an unmet need for effective targeted treatment. Our data highlight immunotherapeutic opportunities in Notch-activated BLBC. Effective IL1β and CCL2 antagonists are currently in clinical review to treat benign inflammatory disease, and their transition to the cancer clinic could have a rapid impact. Cancer Discov; 7(11); 1320-35. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 1201.

A technical feasibility report on correlative studies from the investigator-initiated phase II study of pembrolizumab (Pembro) immunological response evaluation (INSPIRE)

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Background: Validated biomarkers of response to immune checkpoint inhibitors are needed. Methods: INSPIRE (NCT02644369) is a biomarker-driven study to comprehensively evaluate changes in genomic and immune landscapes in tumors and blood of patients (pts) treated with pembro at 200 mg IV Q3W. It consists of 5 histological cohorts of 20 evaluable pts each: head and neck squamous cell cancer (SCCHN), triple negative breast cancer (TNBC), high grade serous ovarian cancer (HGSOC), melanoma (MM) and mixed solid tumors (MST). All pts undergo pre- and on-treatment (week 6-9) fresh tumor biopsies (bx), and at progression for responders. The first core bx is for immunohistochemistry and subsequent cores are pooled to create single cell suspension for 5 prioritized biomarker assay groups: (1) whole exome/RNA-/TCR-sequencing; (2) T/B/NK, APCs, and/or Treg phenotyping; (3) patient-derived xenografts; (4) RNA-seq on viably sorted immune populations; (5) TIL expansion and characterization. Serial blood samples for immunophenotyping, chemokines/cytokines and ctDNA are collected. Results: 53 pts were enrolled from March 21, 2016-January 16, 2017 (5 SCCHN, 8 TNBC, 17 HGSOC, 7 MM, 16 MST). 84 tumor bx (53 pre-, 30 on-treatment, 1 progression) and 244 blood-based biomarker samples have been collected. The most common sites of tumor bx were: lymph nodes (27%), liver (22%) and skin (14%) (see table). For the 5 cohorts, the % of tumor bx with sufficient cellularity for biomarker assay groups 1 and 2 are: SCCHN (33%), TNBC (9%), HGSOC (52%), MM (55%), MST (55%). Conclusions: This report provides robust technical feasibility data to plan immune and molecular characterization of tumor and blood-based biomarkers in pts receiving ICI. Clinical trial information: NCT02644369. [Table: see text]

Immunologic and genomic characterization of high grade serous ovarian cancer (HGSOC) in patients (pts) treated with pembrolizumab (Pembro) in the phase II INSPIRE trial

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Background: Checkpoint inhibitors have shown to be effective in different tumors and are under investigation in HGSOC. Methods: INSPIRE (NCT02644369) is a prospective multi-cohort study investigating tumor genomic and immune landscapes in pts treated with Pembro at 200 mg IV Q3W. Patients underwent tumor biopsy pre, on-treatment and at progression for DNA/RNA sequence, immune-profile, and PD-L1 expression by immunohistochemistry (IHC). Serial blood samples for immunophenotyping were collected. Correlative data are available for 6 pts: 3 with shrinkage in target lesion and 3 with progressive disease (PD). Results: At interim analysis as of January 2017, 18 pts with HGSOC have been enrolled and 16 have platinum-resistant disease, with median 3 prior lines of treatment (range 1-7). Of 14 evaluable pts, best response by RECIST 1.1 was stable disease (SD) in 5 (36%) and PD in 9 (64%). Mean Tumor Proportion Score of PD-L1 by IHC (Qualtek) was 6.4% (range 0-30%). Grade 3/4 adverse events possibly related to Pembro were observed in 4/18 (22%) pts; none was fatal and the most common were fatigue and hyponatremia. Preliminary correlative data showed no significant change in CD4, CD8 and myeloid-derived suppressor cells in peripheral blood after Pembro treatment. Mean PD-1 expression on CD4 and CD8 T cells on baseline tumor tissue (measured as product of PD-1+ cells and the per cell expression of PD-1 [% of mean fluorescence intensity]) was significantly higher in pts with tumor shrinkage compared to pts with PD (CD4: 2658 vs 678, p = .02; CD8: 1999 vs 451, p = .048). Genomic analysis of baseline tumor tissue was available for 3 pts with tumor shrinkage and 2 with PD. Mean mutation burden was higher for pts with tumor shrinkage (2.38 vs 1.0 mutations/Mb covered). The pt with the longest SD in our cohort (6 months) had the highest mutation burden (2.72), including somatic POLE (c.6331-6C > G) and germline BRCA2mutations. Conclusions: In HGSOC, pts with higher PD-1 level on tumor CD4 and CD8 T cells and higher mutation burden at baseline may have a better outcome following treatment with Pembro. POLE mutation is rare in HGSOC but may correlate with checkpoint inhibitor activity. Clinical trial information: NCT02644369.

Molecular Pathways: Evaluating the Potential for B7-H4 as an Immunoregulatory Target

With the clinical success of CTLA-4 and PD-1 blockade in treating malignancies, there is tremendous interest in finding new ways to augment antitumor responses by targeting other inhibitory molecules. In this review, we describe one such molecule. B7-H4, a member of the B7 family of immunoregulatory proteins, inhibits T cell proliferation and cytokine production through ligation of an unknown receptor expressed by activated T cells. Notably, B7-H4 protein expression is observed in a high proportion of patients' tumors across a wide variety of malignancies. This high expression by tumors in combination with its low or absent protein expression in normal tissues makes B7-H4 an attractive immunotherapeutic target. Preclinical investigation into B7-H4-specific chimeric antigen receptor (CAR) T cells, antibody-mediated blockade of B7-H4, and anti-B7-H4 drug conjugates has shown antitumor efficacy in mouse models. The first clinical trials have been completed to assess the safety and efficacy of a B7-H4 fusion protein in ameliorating rheumatoid arthritis. Clin Cancer Res; 23(12); 2934-41. ©2017 AACR.

Exposure to sequestered self-antigens in vivo is not sufficient for the induction of autoimmune diabetes

Although the role of T cells in autoimmunity has been explored for many years, the mechanisms leading to the initial priming of an autoimmune T cell response remain enigmatic. The 'hit and run' model suggests that self-antigens released upon cell death can provide the initial signal for a self-sustaining autoimmune response. Using a novel transgenic mouse model where we could induce the release of self-antigens via caspase-dependent apoptosis. We tracked the fate of CD8+ T cells specific for the self-antigen. Our studies demonstrated that antigens released from apoptotic cells were cross-presented by CD11c+ cells in the draining lymph node. This cross-presentation led to proliferation of self-antigen specific T cells, followed by a transient ability to produce IFN-γ, but did not lead to the development of autoimmune diabetes. Using this model we examined the consequences on T cell immunity when apoptosis was combined with dendritic cell maturation signals, an autoimmune susceptible genetic background, and the deletion of Tregs. The results of our study demonstrate that autoimmune diabetes cannot be initiated by the presentation of antigens released from apoptotic cells in vivo even in the presence of factors known to promote autoimmunity.

A distinct innate lymphoid cell population regulates tumor-associated T cells

Antitumor T cells are subject to multiple mechanisms of negative regulation. Recent findings that innate lymphoid cells (ILCs) regulate adaptive T cell responses led us to examine the regulatory potential of ILCs in the context of cancer. We identified a unique ILC population that inhibits tumor-infiltrating lymphocytes (TILs) from high-grade serous tumors, defined their suppressive capacity in vitro, and performed a comprehensive analysis of their phenotype. Notably, the presence of this CD56+CD3- population in TIL cultures was associated with reduced T cell numbers, and further functional studies demonstrated that this population suppressed TIL expansion and altered TIL cytokine production. Transcriptome analysis and phenotypic characterization determined that regulatory CD56+CD3- cells exhibit low cytotoxic activity, produce IL-22, and have an expression profile that overlaps with those of natural killer (NK) cells and other ILCs. NKp46 was highly expressed by these cells, and addition of anti-NKp46 antibodies to TIL cultures abrogated the ability of these regulatory ILCs to suppress T cell expansion. Notably, the presence of these regulatory ILCs in TIL cultures corresponded with a striking reduction in the time to disease recurrence. These studies demonstrate that a previously uncharacterized ILC population regulates the activity and expansion of tumor-associated T cells.

K48-linked KLF4 ubiquitination by E3 ligase Mule controls T-cell proliferation and cell cycle progression

T-cell proliferation is regulated by ubiquitination but the underlying molecular mechanism remains obscure. Here we report that Lys-48-linked ubiquitination of the transcription factor KLF4 mediated by the E3 ligase Mule promotes T-cell entry into S phase. Mule is elevated in T cells upon TCR engagement, and Mule deficiency in T cells blocks proliferation because KLF4 accumulates and drives upregulation of its transcriptional targets E2F2 and the cyclin-dependent kinase inhibitors p21 and p27. T-cell-specific Mule knockout (TMKO) mice develop exacerbated experimental autoimmune encephalomyelitis (EAE), show impaired generation of antigen-specific CD8⁺ T cells with reduced cytokine production, and fail to clear LCMV infections. Thus, Mule-mediated ubiquitination of the novel substrate KLF4 regulates T-cell proliferation, autoimmunity and antiviral immune responses in vivo.

The E3 ligase Mule has been previously reported to be essential for B cell development and function by modulating p53 ubiquitination and degradation. Here Hao et al. identify KLF4 as a novel ubiquitination target of Mule and show it controls T cell proliferation and autoimmunity.

RAIDD Mediates TLR3 and IRF7 Driven Type I Interferon Production

BACKGROUND/AIMS

Viral infections represent a global health problem with the need for new viral therapies and better understanding of the immune response during infection. The most immediate and potent anti-viral defense mechanism is the production of type I interferon (IFN-I) which are activated rapidly following recognition of viral infection by host pathogen recognition receptors (PRR). The mechanisms of innate cellular signaling downstream of PRR activation remain to be fully understood. In the present study, we demonstrate that CASP2 and RIPK1 domain-containing adaptor with death domain (CRADD/RAIDD) is a critical component in type I IFN production.

METHODS

The role of RAIDD during IFN-I production was investigated using western blot, shRNA mediated lentiviral knockdown, immunoprecipitation and IFN-I driven dual luciferase assay.

RESULTS

Immunoprecipitation analysis revealed the molecular interaction of RAIDD with interferon regulatory factor 7 (IRF7) and its phosphorylating kinase IKKε. Using an IFN-4α driven dual luciferase analysis in RAIDD deficient cells, type I IFN activation by IKKε and IRF7 was dramatically reduced. Furthermore, deletion of either the caspase recruitment domain (CARD) or death domain (DD) of RAIDD inhibited IKKε and IRF7 mediated interferon-4α activation.

CONCLUSION

We have identified that the adaptor molecule RAIDD coordinates IKKε and IRF7 interaction to ensure efficient expression of type I interferon.

Society for immunotherapy of cancer (SITC) statement on the proposed changes to the common rule

The Common Rule is a set of ethical principles that provide guidance on the management of human subjects taking part in biomedical and behavioral research in the United States. The elements of the Common Rule were initially developed in 1981 following a revision of the Declaration of Helsinki in 1975. Most academic facilities follow the Common Rule in the regulation of clinical trials research. Recently, the government has suggested a revision of the Common Rule to include more contemporary and streamlined oversight of clinical research. In this commentary, the leadership of the Society for Immunotherapy of Cancer (SITC) provides their opinion on this plan. While the Society recognizes the considerable contribution of clinical research in supporting progress in tumor immunotherapy and supports the need for revisions to the Common Rule, there is also some concern over certain elements which may restrict access to biospecimens and clinical data at a time when high throughput technologies, computational biology and assay standardization is allowing major advances in understanding cancer biology and providing potential predictive biomarkers of immunotherapy response. The Society values its professional commitment to patients for improving clinical outcomes with tumor immunotherapy and supports continued discussion with all stakeholders before implementing changes to the Common Rule in order to ensure maximal patient protections while promoting continued clinical research at this historic time in cancer research.

The Role of Cbl-b in CD4+ T Cell Resistance to Regulatory T Cell Suppression

Cancer immunotherapy has demonstrated enormous potential as a novel therapeutic modality in the management of multiple malignancies, including melanoma and leukemia. While cancer immunotherapy is designed to enhance effector T cell function and promote tumor destruction, one of its limitations is the negative influence of tumour-resident CD4+ FoxP3+ regulatory T (Treg) cells on T cell anti-tumour activity. Previous attempts to overcome this challenge have largely focused on the depletion of Treg cells, but this has proven to be a challenging and largely ineffectual process. An alternative approach to overcoming this problem involves generating effector T cell resistance against Treg cell-mediated suppression. Work in this area to date has shown that deficiency in the E3 ubiquitin ligase, Cbl-b, in mice results in the development of hyper-proliferative and pro-inflammatory effector T cells, even in the presence of Treg cells. This study investigates the cellular mechanisms behind this Treg resistance using Cbl-b deficient CD4+ FoxP3− and CD8+ T cells. We demonstrate that Cbl-b −/− CD4+ FoxP3− T cells exhibit both hyper-secretion of and hyper-sensitivity to IL-2, and that this serves as an important mechanism to escape suppression by Treg cells. Accordingly, we show that the blockade of IL-2Rα is sufficient to reverse the Treg cell-mediated suppression and excess IL-2 alone is sufficient to override suppressive signals by Treg cells. Overall, this study provides further insight into the potential development of Treg resistant effector T cells able to generate a more robust anti-tumor immune response.

Abstract A35: Elucidating mechanisms involved in long-term response to platinum-based chemotherapy in high-grade serous ovarian cancer

Introduction: Approximately eighty percent of women with stage III high-grade serous ovarian cancer (HGSOC) develop recurrent disease despite initial surgery and platinum-based combination chemotherapy. Clinico-pathological factors do not allow precise prediction of outcome and hence initial treatment is not stratified. Potential genomic and immunologic predictive factors of response/resistance to platinum-based chemotherapy could be identified by comparing and contrasting long-term with short-term survivors.

Methods: Patients with stage III HGSOC and upfront debulking surgery followed by platinum-based chemotherapy were selected from the Princess Margaret Cancer Centre registry. Retrospectively, 25 patients were identified as long-term responders (alive 10 years or more from the time of diagnosis) and 24 patients as short-term responders (dead within 2 years of diagnosis and primary platinum resistant). Available archival snap frozen or formalin-fixed paraffin-embedded tumor and matched normal tissue sections from identified patients were obtained through the University Health Network (UHN) Biobank. Pathology was confirmed by an expert gynecological pathologist. Each archival specimen was characterized by histological, molecular, genomic and immunologic patterns at presentation of disease. We performed whole exome sequencing (WES) and transcriptome sequencing (RNAseq) from total DNA and RNA extracted from archival tumor tissues to characterize genetic alterations and gene expression profiles. We profiled the tumor tissue protein expression of p53, Ki67, p16, Rb1, cyclin E, cyclin D1, CD3, CD8, CD68, PDL-1, FoxP3, and the Bcl-2 family proteins (Bcl-xL, Bcl-2, MCL-1, Bax, Bak, Bim, Noxa, Puma) through immunohistochemistry (IHC) analyses.

Results: Preliminary genomic data were analyzed from the initial set of 3 long-term survivors and 7 short-term survivors. 8/10 tumors were characterized by TP53 mutations. All long-term survivors harbor germline mutations in BRCA1 or 2. Somatic mutations in ADAMTS family genes associated with chemo-sensitivity occur at a higher frequency in long-term survivors. One patient with a long-term response had a hyper-mutated phenotype. Preliminary IHC analyses on 21 patients (10 long- and 11 short-term survivors) examined to date showed that apoptosis-regulating genes—such as p53, Bcl-2, Bcl-xL, Bax, which regulate cancer cell sensitivity/resistance—do not have a significant difference in protein expression at baseline. Purity estimates generated from WES shows that tumors from long survivors have reduced purity as compared to short-term survivors. Overall levels of immune and stromal infiltration for each tumor by applying the ESTIMATE algorithm to the quantile-normalized gene expression profiles suggest higher immune and stromal scores in long surviving compared to short surviving HGSOC.

Conclusions: The initial results indicate a potential predictive signature for long-term response in HGSOC.

Citation Format: Stephanie Lheureux, Cindy Yang, Patricia Shaw, Blaise Clarke, Julissa Tsao, Katherine Karakasis, Marcus Butler, Noor Salman, Mark Dowar, Jing Xu, Laurent Poulain, Pamela S. Ohashi, Trevor Pugh, Amit Oza. Elucidating mechanisms involved in long-term response to platinum-based chemotherapy in high-grade serous ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A35.

miR-155 Upregulation in Dendritic Cells Is Sufficient To Break Tolerance In Vivo by Negatively Regulating SHIP1

TLR-induced maturation of dendritic cells (DCs) leads to the production of proinflammatory cytokines as well as the upregulation of various molecules involved in T cell activation. These are believed to be the critical events that account for the induction of the adaptive immune response. In this study, we have examined the role of miR-155 in DC function and the induction of immunity. Using a model in which the transfer of self-Ag-pulsed, TLR-matured DCs can induce a functional CD8 T cell response and autoimmunity, we find that DCs lacking miR-155 have an impaired ability to break immune tolerance. Importantly, transfer of self- Ag-pulsed DCs overexpressing miR-155 was sufficient to break tolerance in the absence of TLR stimuli. Although these unstimulated DCs induced T cell function in vivo, there was no evidence for the upregulation of costimulatory ligands or cytokine secretion. Further analysis showed that miR-155 influenced the level of the phosphatase SHIP1 in DCs and that the lack of SHIP1 in DCs was sufficient to break T cell tolerance in vivo, again in the absence of TLR-induced DC maturation. Our study demonstrates that the overexpression of miR-155 in DCs is a critical event that is alone sufficient to break self-tolerance and promote a CD8-mediated autoimmune response in vivo. This process is independent of the induction of conventional DC maturation markers, indicating that miR-155 regulation of SHIP represents a unique axis that regulates DC function in vivo.

B7-H4 is a positive regulator of antitumor immunity

B7-H4 (B7x, B7S1, VTCN1, DD-0110) is a member of the B7 superfamily that negatively regulates T cell responses.¹ In addition, B7-H4 expression is increased on tumors and has been shown to be a negative prognostic marker for many cancers.² Unexpectedly our recent study demonstrated that B7-H4 inhibited tumor growth and was required to promote effective antitumor responses.³.