CD4 Phenotypes Are Associated with Reduced Expansion of Tumor-Infiltrating Lymphocytes in Melanoma Patients Treated with Adoptive Cell Therapy

Tumor-infiltrating lymphocyte (TIL) adoptive cell therapy is effective in treating malignant melanoma, but its success relies on the adequate ex vivo expansion of TIL. To assess correlates of TIL expansion, CD4+ and CD8+ TIL were analyzed by RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing of acetylated histone 3. Patients were grouped into "TIL high" and "TIL low" based on division at the median number of TIL infused. Greater numbers of TIL infused correlated with longer overall survival, and increased frequencies of CD4+ cells infused were negatively correlated with the number of TIL infused. RNA-seq analysis of CD4+ TIL showed increases in Th2/Th17/regulatory T cell-related transcripts and pathways in the TIL-low group. Analysis of a public single-cell RNA-seq dataset validated findings that increased frequencies of CD4+ cells were negatively correlated with the number of TIL infused. TIL-low patients had significantly increased frequencies of CD4+ cells expressing ETS2 and OSM and trended toward increased expression of TNFRSF18.

Phase II clinical and immune correlate study of adjuvant nivolumab plus ipilimumab for high-risk resected melanoma

BACKGROUND

Adjuvant therapy for high-risk resected melanoma with programmed cell-death 1 blockade results in a median relapse-free survival (RFS) of 5 years. The addition of low dose ipilimumab (IPI) to a regimen of adjuvant nivolumab (NIVO) in CheckMate-915 did not result in increased RFS. A pilot phase II adjuvant study of either standard dose or low dose IPI with NIVO was conducted at two centers to evaluate RFS with correlative biomarker studies.

METHODS

Patients with resected stages IIIB/IIIC/IV melanoma received either IPI 3 mg/kg and NIVO 1 mg/kg (cohort 4) or IPI 1 mg/kg and NIVO 3 mg/kg (cohorts 5 and 6) induction therapy every 3 weeks for 12 weeks, followed by maintenance NIVO. In an amalgamated subset of patients across cohorts, peripheral T cells at baseline and on-treatment were assessed by flow cytometry and RNA sequencing for exploratory biomarkers.

RESULTS

High rates of grade 3-4 adverse events precluded completion of induction therapy in 50%, 35% and 7% of the patients in cohorts 4, 5 and 6, respectively. At a median of 63.9 months of follow-up, 16/56 patients (29%) relapsed. For all patients, at 5 years, RFS was 71% (95% CI: 60 to 84), and overall survival was 94% (95% CI: 88 to 100). Expansion of CD3+CD4+CD38+CD127-GARP- T cells, an on-treatment increase in CD39 expression in CD8+ T cells, and T-cell expression of phosphorylated signal-transducer-and-activator-of-transcription (STAT)2 and STAT5 were associated with relapse.

CONCLUSIONS

Adjuvant IPI/NIVO at the induction doses used resulted in promising relapse-free and overall survival, although with a high rate of grade 3-4 adverse events. Biomarker analyses highlight an association of ectoenzyme-expressing T cells and STAT signaling pathways with relapse, warranting future validation.

TRIAL REGISTRATION NUMBER

NCT01176474 and NCT02970981.

Clinical and immune correlate results from a phase 1b study of the histone deacetylase inhibitor mocetinostat with ipilimumab and nivolumab in unresectable stage III/IV melanoma

Checkpoint immunotherapies (CPIs) have improved outcomes for metastatic melanoma patients, with objective response rates to combination ipilimumab and nivolumab of ~58%. Preclinical data suggest that histone deacetylase (HDAC) inhibition enhances antitumor immune activity and may augment CPI. In a phase Ib open-label pilot trial (NCT03565406), patients with therapy-naive metastatic melanoma were treated with the class I/IV HDAC inhibitor mocetinostat orally three times a week in combination with nivolumab and ipilimumab every 3 weeks for 12 weeks followed by 12-week maintenance cycles of nivolumab every 2 weeks and mocetinostat at the same dose and schedule as induction. The endpoints of the trial were safety, definition of a recommended phase 2 dose, preliminary assessment of response, and correlative marker determination. Patient PBMC and serum samples collected at baseline and on-treatment were assessed by flow cytometry and Luminex assays for immune correlates. Ten patients were treated: nine with 70-mg and one with 50-mg mocetinostat. In the 70-mg cohort, eight patients had objective responses. The patient in the 50-mg cohort had an early progression of disease. All patients had grade 2 or higher toxicities, and six had grades 3 and 4 toxicities. Patient PBMC showed significant decreases in myeloid-derived suppressor cells and trends towards reduced anti-inflammatory monocyte phenotypes. Patient serum showed significant upregulation of granzyme A and TNF and trends towards increased granzyme B and IFNγ. Collectively, combining CPI and mocetinostat had favorable response rates but with high levels of toxicity. Assessment of immune correlates supports a shift away from immunosuppressive phenotypes towards enhanced immune responses.

PhenoComb: a discovery tool to assess complex phenotypes in high-dimensional single-cell datasets

Motivation

High-dimensional cytometry assays can simultaneously measure dozens of markers, enabling the investigation of complex phenotypes. However, as manual gating relies on previous biological knowledge, few marker combinations are often assessed. This results in complex phenotypes with the potential for biological relevance being overlooked. Here, we present PhenoComb, an R package that allows agnostic exploration of phenotypes by assessing all combinations of markers. PhenoComb uses signal intensity thresholds to assign markers to discrete states (e.g. negative, low, high) and then counts the number of cells per sample from all possible marker combinations in a memory-safe manner. Time and disk space are the only constraints on the number of markers evaluated. PhenoComb also provides several approaches to perform statistical comparisons, evaluate the relevance of phenotypes and assess the independence of identified phenotypes. PhenoComb allows users to guide analysis by adjusting several function arguments, such as identifying parent populations of interest, filtering of low-frequency populations and defining a maximum complexity of phenotypes to evaluate. We have designed PhenoComb to be compatible with a local computer or server-based use.

Results

In testing of PhenoComb's performance on synthetic datasets, computation on 16 markers was completed in the scale of minutes and up to 26 markers in hours. We applied PhenoComb to two publicly available datasets: an HIV flow cytometry dataset (12 markers and 421 samples) and the COVIDome CyTOF dataset (40 markers and 99 samples). In the HIV dataset, PhenoComb identified immune phenotypes associated with HIV seroconversion, including those highlighted in the original publication. In the COVID dataset, we identified several immune phenotypes with altered frequencies in infected individuals relative to healthy individuals. Collectively, PhenoComb represents a powerful discovery tool for agnostically assessing high-dimensional single-cell data.

Availability and implementation

The PhenoComb R package can be downloaded from https://github.com/SciOmicsLab/PhenoComb.

Supplementary information

Supplementary data are available at Bioinformatics Advances online.

Abstract PO030: A Novel T-cell Population Expressing the Ectoenzymes CD38 and CD39 is Associated with Melanoma Patient Non-Response to Immunotherapy

Cancer immunotherapy has emerged as one of the most potent therapeutic tools in treating melanoma and a variety of other malignancies. Immunotherapy includes inhibition of the modulators of T cell antitumor function, the immune checkpoints, by using antibodies against them. In advanced melanoma patients, immune checkpoint inhibitors ipilimumab (IPI) and nivolumab (NIVO) have had unprecedented efficacy. Although many patients respond well to this therapy, many patients remain unresponsive. The mechanism underlying treatment failures remains poorly understood. Using a novel high-dimensional flow cytometry analysis methodology, CytoBrute, we found that in the cohort of advanced melanoma patients receiving sequential NIVO-IPI, high baseline levels of a novel immunophenotype, CD4+CD38+CD39+CD127-GARP- T-cells (median frequency 0.3%), was associated with poor outcomes (disease progression p=0.008, and decreased overall survival p<0.0001 HR = 6.8). Both CD38 and CD39 are ectoenzymes with CD38 hydrolyzing NAD+ to cyclic-ADP ribose and CD39 converting extracellular ATP to immunosuppressive adenosine nucleosides. Both of these proteins are being evaluated as targets to increase the efficacy of immunotherapies. The association of this novel phenotype, which we have termed T-cells expressing ectoenzymes (Tee), was validated in two independent cohorts of melanoma patients treated with NIVO monotherapy, with progressors showing a higher frequency of this immunophenotype at baseline (p=0.047). In IPI+NIVO adjuvant treated melanoma patients, an increase in this population of cells was observed during treatment in relapsing patients, leading to a higher frequency of these cells in relapsing patients relative to patients with no evidence of disease (p=002). Preliminary data obtained from single cell RNA sequencing from the ectoenzyme expressing peripheral blood T cell population, demonstrated predominant expression of IL-32 and CD99 (a membrane glycoprotein associated with lymphocyte diapedesis) in this population, along with several additional clusters distinguished by expression of specific TcR V beta genes. Collectively, we have identified a novel population of ectoenzyme expressing T-cells (CD3+CD4+CD38+CD39+CD127-GARP-) associated with poor melanoma patient outcomes in response to checkpoint immunotherapy. Further investigation of the mechanisms by which this novel T-cell phenotype is associated with poor patient outcomes is under way.

Citation Format: Ankita Mitra, David M. Woods, Anjali Rao, Andressa S. Laino, Aidan Winters, Itai Yanai, Pratip K. Chattopadhyay, Jeffrey S. Weber. A Novel T-cell Population Expressing the Ectoenzymes CD38 and CD39 is Associated with Melanoma Patient Non-Response to Immunotherapy [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO030.

Nivolumab and ipilimumab are associated with distinct immune landscape changes and response-associated immunophenotypes

BACKGROUNDThe reshaping of the immune landscape by nivolumab (NIVO) and ipilimumab (IPI) and its relation to patient outcomes is not well described.METHODSWe used high-parameter flow cytometry and a computational platform, CytoBrute, to define immunophenotypes of up to 15 markers to assess peripheral blood samples from metastatic melanoma patients receiving sequential NIVO > IPI or IPI > NIVO (Checkmate-064).RESULTSThe 2 treatments were associated with distinct immunophenotypic changes and had differing profiles associated with response. Only 2 immunophenotypes were shared but had opposing relationships to response/survival. To understand the impact of sequential treatment on response/survival, phenotypes that changed after the initial treatment and differentiated response in the other cohort were identified. Immunophenotypic changes occurring after NIVO were predominately associated with response to IPI > NIVO, but changes occurring after IPI were predominately associated with progression after NIVO > IPI. Among these changes, CD4+CD38+CD39+CD127-GARP- T cell subsets were increased after IPI treatment and were negatively associated with response/survival for the NIVO > IPI cohort.CONCLUSIONCollectively, these data suggest that the impact of IPI and NIVO on the immunophenotypic landscape of patients is distinct and that the impact of IPI may be associated with resistance to subsequent NIVO therapy, consistent with poor outcomes in the IPI > NIVO cohort of Checkmate-064.

C reactive protein impairs adaptive immunity in immune cells of patients with melanoma

BACKGROUND

High C reactive protein (CRP) levels have been reported to be associated with a poor clinical outcome in a number of malignancies and with programmed cell death protein 1 immune checkpoint blockade in patients with advanced cancer. Little is known about the direct effects of CRP on adaptive immunity in cancer. Therefore, we investigated how CRP impacted the function of T cells and dendritic cells (DCs) from patients with melanoma.

METHODS

The effects of CRP on proliferation, function, gene expression and phenotype of patient T cells and DCs, and expansion of MART-1 antigen-specific T cells were analyzed by multicolor flow cytometry and RNA-seq. Additionally, serum CRP levels at baseline from patients with metastatic melanoma treated on the Checkmate-064 clinical trial were assessed by a Luminex assay.

RESULTS

In vitro, CRP inhibited proliferation, activation-associated phenotypes and the effector function of activated CD4+ and CD8+ T cells from patients with melanoma. CRP-treated T cells expressed high levels of interleukin-1β, which is known to enhance CRP production from the liver. CRP also suppressed formation of the immune synapse and inhibited early events in T-cell receptor engagement. In addition, CRP downregulated the expression of costimulatory molecules on mature DCs and suppressed expansion of MART-1-specific CD8+ T cells in a dose-dependent manner by impacting on both T cells and antigen-presenting cells. High-serum CRP levels at baseline were significantly associated with a shorter survival in both nivolumab-treated and ipilimumab-treated patients.

CONCLUSIONS

These findings suggest that high levels of CRP induce an immunosuppressive milieu in melanoma and support the blockade of CRP as a therapeutic strategy to enhance immune checkpoint therapies in cancer.

TRIAL REGISTRATION NUMBER

NCT01783938 and NCT02983006.

High-Parameter Single-Cell Analysis

Thousands of transcripts and proteins confer function and discriminate cell types in the body. Using high-parameter technologies, we can now measure many of these markers at once, and multiple platforms are now capable of analysis on a cell-by-cell basis. Three high-parameter single-cell technologies have particular potential for discovering new biomarkers, revealing disease mechanisms, and increasing our fundamental understanding of cell biology. We review these three platforms (high-parameter flow cytometry, mass cytometry, and a new class of technologies called integrated molecular cytometry platforms) in this article. We describe the underlying hardware and instrumentation, the reagents involved, and the limitations and advantages of each platform. We also highlight the emerging field of high-parameter single-cell data analysis, providing an accessible overview of the data analysis process and choice of tools.

High-dimension flow cytometry reveals comprehensive deviations in immunophenotypes associated with non-response to melanoma immunotherapies

Immunotherapies have revolutionized the treatment of many cancers, but most patients fail to respond. To investigate immune phenotypes associated with patient response, we assessed 68 unique peripheral blood markers using high-dimension flow cytometry. Samples from 41 metastatic melanoma patients treated with αPD1 or αCTLA4 and 12 healthy donors (HD) were evaluated. To avoid a loss of higher order data, we used a novel computational approach, CytoBrute, to analyze the data through semi-comprehensive Boolean gating. Lineages (e.g. CD3+CD4+) were evaluated for all possible combinations for up to 15 markers. In αPD1 treated patients 1,051 immune signatures differentiated patient response at baseline with a p-value <0.05, while 823 differentiated αCTLA4 treated patients. Only eight signatures overlapped between the two therapies. Signatures included both low (e.g. CD4+CD45RO+CD278−) and high-dimension immunophenotypes (e.g. CD14+CD33+CD11C+CD163+PDL2+41BBL+CD86+CD40+PDL1−CD66B−CD80−GAL9−CD15−CD19−OX40L−). A total of 2,895 signatures significantly differentiated HD versus patients, of which 270 significantly differed (p<0.05) based on patient response. Samples from non-responding patients less closely resembled HD relative to responding patient in 205 of these 270 signatures (p<1e-8). Comparisons of all 102,000 assessed phenotypes showed that non-responding patients had a lesser degree of similarity in immunophenotypes in comparison to responders. Our data demonstrate a novel and powerful approach to interrogating complex immunophenotypes and show that comprehensive immunophenotypic deviations are associated with non-response to melanoma immunotherapies.

HDAC6 selective inhibition of melanoma patient T-cells augments anti-tumor characteristics

Background

Therapies targeting anti-tumor T-cell responses have proven successful in the treatment of a variety of malignancies. However, as most patients still fail to respond, approaches to augment immunotherapeutic efficacy are needed. Here, we investigated the ability of histone deacetylase 6 (HDAC6)-selective inhibitors to decrease immunosuppression and enhance immune function of melanoma patient T-cells in ex vivo cultures.

Methods

T-cells were harvested from peripheral blood or tumor biopsies of metastatic melanoma patients and cultured in the presence of pan-, class-specific or class-selective histone deacetylase (HDAC) inhibitors. Changes in cytokine production were evaluated by Luminex and intracellular flow cytometry staining. Expression of surface markers, transcription factors, protein phosphorylation, and cell viability were assessed by flow cytometry. Changes in chromatin structure were determined by ATAC-seq.

Results

T-cell viability was impaired with low doses of pan-HDAC inhibitors but not with specific or selective HDAC inhibitors. The HDAC6-selective inhibitors ACY-1215 (ricolinostat) and ACY-241 (citarinostat) decreased Th2 cytokine production (i.e. IL-4, IL-5, IL-6, IL-10 and IL-13). Expansion of peripheral blood T-cells from melanoma patients in the presence of these inhibitors resulted in downregulation of the Th2 transcription factor GATA3, upregulation of the Th1 transcription factor T-BET, accumulation of central memory phenotype T-cells (CD45RA-CD45RO + CD62L + CCR7+), reduced exhaustion-associated phenotypes (i.e. TIM3 + LAG3 + PD1+ and EOMES+PD1+), and enhanced killing in mixed lymphocyte reactions. The frequency, FOXP3 expression, and suppressive function of T regulatory cells (Tregs) were decreased after exposure to ACY-1215 or ACY-241. Higher frequencies of T-cells expressing CD107a + IFNγ+ and central memory markers were observed in melanoma tumor-infiltrating lymphocytes (TIL), which persisted after drug removal and further expansion. After ACY-1215 treatment, increased chromatin accessibility was observed in regions associated with T-cell effector function and memory phenotypes, while condensed chromatin was found in regions encoding the mTOR downstream molecules AKT, SGK1 and S6K. Decreased phosphorylation of these proteins was observed in ACY-1215 and ACY-241-treated T-cells. AKT- and SGK1-specific inhibition recapitulated the increase in central memory frequency and decrease in IL-4 production, respectively, similar to the observed effects of HDAC6-selective inhibition.

Conclusions

HDAC6-selective inhibitors augmented melanoma patient T-cell immune properties, providing a rationale for translational investigation assessing their potential clinical efficacy.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0517-0) contains supplementary material, which is available to authorized users.

Association of Tumor Microenvironment T-cell Repertoire and Mutational Load with Clinical Outcome after Sequential Checkpoint Blockade in Melanoma

To understand prognostic factors for outcome between differentially sequenced nivolumab and ipilimumab in a randomized phase II trial, we measured T-cell infiltration and PD-L1 by IHC, T-cell repertoire metrics, and mutational load within the tumor. We used next-generation sequencing (NGS) and assessed the association of those parameters with response and overall survival. Immunosequencing of the T-cell receptor β-chain locus (TCRβ) from DNA of 91 pretreatment tumor samples and an additional 22 pairs of matched pre- and posttreatment samples from patients who received nivolumab followed by ipilimumab (nivo/ipi), or the reverse (ipi/nivo), was performed to measure T-cell clonality and fraction. Mutational and neoantigen load were also assessed by NGS in 82 of the 91 patients. Tumors were stained using IHC for PD-L1⁺ and CD8⁺ T cells. Pretreatment tumor TCR clonality and neoantigen load were marginally associated with best response with nivo/ipi (P = 0.04 and 0.05, respectively), but not with ipi/nivo. Amalgamated pretreatment mutational load and tumor T-cell fraction were significantly associated with best response with nivo/ipi (P = 0.002). Pretreatment PD-L1 staining intensity and CD8⁺ T-cell counts were correlated with T-cell fraction and clonality, but not mutational or neoantigen load. Patients with increased T-cell fraction posttreatment at week 13 had a 30-fold increased likelihood of survival (P = 0.002). Mutational and neoantigen load, and T-cell infiltrate within the tumor, were associated with outcome of sequential checkpoint inhibition using nivolumab then ipilimumab, but not when ipilimumab was administered before nivolumab.

Decreased Suppression and Increased Phosphorylated STAT3 in Regulatory T Cells are Associated with Benefit from Adjuvant PD-1 Blockade in Resected Metastatic Melanoma

PURPOSE

PD-1 blockade induces durable responses in patients with metastatic melanoma and prolongs relapse-free survival in patients with resected melanoma; however, current biomarkers do not consistently associate with patient responses. In this study, we investigated the impact of nivolumab therapy on peripheral blood regulatory T cells (Treg) and its relation to patient outcomes.

EXPERIMENTAL DESIGN

Peripheral blood Tregs and conventional CD4⁺ T cells from patients with resected high-risk melanoma treated with adjuvant nivolumab were assessed for gene expression changes by RNA-seq. Percentages of circulating Tregs and phosphorylated-STAT3 (pSTAT3) expression levels were assessed by flow cytometry and validated in an independent cohort of active disease patients. Suppressive function of Tregs was assessed in allogeneic mixed lymphocyte reactions.

RESULTS

Tregs from non-relapse patients had increased expression of proliferation associated genes. An increase in the proportion of circulating Tregs and pSTAT3 expression and a reduction in Treg-suppressive capacity were observed in non-relapsing, but not relapsing patient samples 13 weeks after starting treatment. In vitro blockade of PD-1 increased Treg percentages and pSTAT3 expression, and reduced Treg-suppressive function. PD-1 blockade also led to IL10 production by T cells, resulting in higher Treg proliferation. The addition of a STAT3 inhibitor ameliorated the increase in Tregs, enhanced suppressive function, and decreased T-cell IL10 production in vitro.

CONCLUSIONS

These results demonstrate that induction of pSTAT3, reduced suppressive function, and a paradoxical increase in Treg proliferation are novel correlates of patient benefit from PD-1 blockade.

Abstract 612: Nivolumab-induced changes associated with patient outcomes are disparate in metastatic melanoma patient Tregs versus conventional T cells

The PD1 blocking antibody nivolumab induces durable responses in metastatic melanoma patients. However, many patients do not respond and biomarkers differentiating patient response remain unidentified. To address this need, we investigated the effects of nivolumab on peripheral blood conventional CD4+ (Tcons) and regulatory T-cells (Tregs) of metastatic melanoma patients receiving nivolumab as adjuvant therapy or for metastatic disease. An increased ratio of PD1 expression on Tregs compared with Tcons was found at baseline patients with no evidence of disease (NED), while relapsing patients had a lower ratio (p<0.05). Intriguingly, NED patients had an increase in circulating Treg percentages post-nivolumab (p<0.05), which was not observed in relapsing patients. In vitro treatment of isolated T-cells with αPD1 resulted in increased proliferation (p<0.001). RNA-seq analysis of Tcons and Tregs showed distinct gene expression changes based on cell type and patient outcome. Pathway analysis demonstrated: upregulation of proliferation associated genes in NED Tregs, but not in relapse Tregs; downregulation of oxidative phosphorylation associated genes in NED patient Tregs and upregulation in NED Tcons; upregulation of heme metabolism associated genes in NED Tcons and downregulated in relapsing patient Tcons; and similar differences in MTORC1, heme metabolism and hypoxia pathways (all pathways q<0.01). Both Tcons and Tregs from non-relapsing patients had induction of phosphoSTAT3 (pSTAT3) expression post-nivolumab (p=0.012), which was absent in relapsing patients. This was also observed in a cohort of active disease patients (p=0.022), and the magnitude of change in pSTAT3 was positively correlated with patient survival (R2=0.49, p<0.05). Enhanced pSTAT3 expression was recapitulated in vitro in isolated T-cells (p<0.05). Post-nivolumab Tregs from patients with positive outcomes also had reduced suppressive function in mixed lymphocyte reactions (p<0.05), while patients with negative outcomes had no changes. In vitro treatment of Tregs with PD1 blocking antibodies resulted in a reduction in suppressive function (p<0.0001), while addition of a STAT3 inhibitor enhanced suppressive function (p<0.0001). These results suggest that nivolumab alters Treg signaling and metabolism pathways, hindering immune suppressive function. Collectively, our data demonstrate distinct effects of nivolumab on Tcons vs. Tregs, and highlight several potential biomarkers of patient benefit, warranting further exploration.

Citation Format: David M. Woods. Nivolumab-induced changes associated with patient outcomes are disparate in metastatic melanoma patient Tregs versus conventional T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 612.

The class I/IV HDAC inhibitor mocetinostat increases tumor antigen presentation, decreases immune suppressive cell types and augments checkpoint inhibitor therapy

Checkpoint inhibitor therapy has led to major treatment advances for several cancers including non-small cell lung cancer (NSCLC). Despite this, a significant percentage of patients do not respond or develop resistance. Potential mechanisms of resistance include lack of expression of programmed death ligand 1 (PD-L1), decreased capacity to present tumor antigens, and the presence of an immunosuppressive tumor microenvironment. Mocetinostat is a spectrum-selective inhibitor of class I/IV histone deacetylases (HDACs), a family of proteins implicated in epigenetic silencing of immune regulatory genes in tumor and immune cells. Mocetinostat upregulated PD-L1 and antigen presentation genes including class I and II human leukocyte antigen (HLA) family members in a panel of NSCLC cell lines in vitro. Mocetinostat target gene promoters were occupied by a class I HDAC and exhibited increased active histone marks after mocetinostat treatment. Mocetinostat synergized with interferon γ (IFN-γ) in regulating class II transactivator (CIITA), a master regulator of class II HLA gene expression. In a syngeneic tumor model, mocetinostat decreased intratumoral T-regulatory cells (Tregs) and potentially myeloid-derived suppressor cell (MDSC) populations and increased intratumoral CD8+ populations. In ex vivo assays, patient-derived, mocetinostat-treated Tregs also showed significant down regulation of FOXP3 and HELIOS. The combination of mocetinostat and a murine PD-L1 antibody antagonist demonstrated increased anti-tumor activity compared to either therapy alone in two syngeneic tumor models. Together, these data provide evidence that mocetinostat modulates immune-related genes in tumor cells as well as immune cell types in the tumor microenvironment and enhances checkpoint inhibitor therapy.

Predictors of responses to immune checkpoint blockade in advanced melanoma

Immune checkpoint blockers (ICB) have become pivotal therapies in the clinical armamentarium against metastatic melanoma (MMel). Given the frequency of immune related adverse events and increasing use of ICB, predictors of response to CTLA-4 and/or PD-1 blockade represent unmet clinical needs. Using a systems biology-based approach to an assessment of 779 paired blood and tumor markers in 37 stage III MMel patients, we analyzed association between blood immune parameters and the functional immune reactivity of tumor-infiltrating cells after ex vivo exposure to ICB. Based on this assay, we retrospectively observed, in eight cohorts enrolling 190 MMel patients treated with ipilimumab, that PD-L1 expression on peripheral T cells was prognostic on overall and progression-free survival. Moreover, detectable CD137 on circulating CD8⁺ T cells was associated with the disease-free status of resected stage III MMel patients after adjuvant ipilimumab + nivolumab (but not nivolumab alone). These biomarkers should be validated in prospective trials in MMel.The clinical management of metastatic melanoma requires predictors of the response to checkpoint blockade. Here, the authors use immunological assays to identify potential prognostic/predictive biomarkers in circulating blood cells and in tumor-infiltrating lymphocytes from patients with resected stage III melanoma.

PD-1 blockade induces phosphorylated STAT3 and results in an increase of Tregs with reduced suppressive function

PD-1 blockade has remarkable response rates in the treatment of melanoma; however, many patients fail to respond, and biomarkers and mechanisms of response remain unknown. We investigated the roles of Tregs, a population of immunosuppressive T-cells, in patient response to nivolumab. Tregs had a decrease in suppressive function in patients with positive outcomes (p=0.03), but not in patients with negative outcomes. Patients with no evidence of disease (NED) displayed increased percentages of Tregs post-nivolumab (p=0.04), but relapsing patients did not. RNA-seq analysis revealed genes significantly changed after treatment were distinct between Tcons and Tregs (~13% overlap) and between NED and relapsing patient Tregs (~2% overlap). Pathway analysis showed an increase in proliferation associated pathways in NED patient Tregs, but not relapsing patients. We found increased phosphoSTAT3 (pSTAT3) expression in Tregs from patients with positive outcomes (p=0.01), but not in patients with negative outcomes. Mechanistically, in vitro culturing of T-cells with αPD-1 resulted in increases in pSTAT3 expression (p=0.03) and increased percentages of Tregs (p=0.001). Culturing with αPD-1 also enhanced production of IL-10 (p=0.02), and the addition of a STAT3 inhibitor reduced the increases in IL-10 levels (p=0.01) and Treg percentages (p=0.01). The addition of an IL-10 neutralizing antibody also reduced the increased Tregs resulting from αPD-1 (p=0.01). These results support a model in which PD-1 blockade increases pSTAT3 expression leading to enhanced IL-10 production and Treg percentages, suggesting that pSTAT3 induction and reduced suppressive function are biomarkers of melanoma patient response to nivolumab.

Abstract B109: Epigenetic reprogramming of T-cells from metastatic melanoma patients enhances central memory and decreases Th2/Treg phenotypes

Immunotherapy strategies for the treatment of melanoma have achieved impressive clinical outcomes over the past decade. Response rates to checkpoint blockade by PD-1 and CTLA-4 antibodies range from 15-40%, while in adoptive cell therapy using tumor infiltrating lymphocytes (TILs), anti-tumor response is observed in approximately 50%. However, the need to improve immunotherapies is evident as the majority of patients are unresponsive to treatment. Dysfunctional T-cells are thought to contribute to failed responses to checkpoint inhibition. As such we sought to investigate the ability of drugs targeting the epigenetic regulatory machinery as a means to alter T-cell function(s) and improve the anti-melanoma response. Here we demonstrate that the HDAC6 selective inhibitor ACY1215 disrupts mTORC signaling pathways in T-cells obtained from melanoma patients. Phosphorylation of mTOR, RAPTOR and the downstream molecules AKT, SGK1, PKCa and S6K were reduced on CD4 and CD8 T-cells after ACY1215 in vitro treatment (p<0.05). The levels of the Th2 cytokines IL-4, IL-6, IL-10 generated by ACY1215-treated T-cells (p<0.05) were also decreased. Similar results were achieved with an SGK1 inhibitor, in agreement with published data demonstrating SGK1 as a regulator of Th2 polarization. Since the mTOR/RAPTOR complex is known to be involved in determining T regulatory (Treg) function, the effects of ACY1215 on Tregs were evaluated. Treatment in vitro with ACY1215 decreased phosphorylated mTOR and RAPTOR in Tregs, and reduced the levels of FOXP3. In a functional suppression assay, ACY1215-treated Tregs displayed a reduced ability to impair proliferation of effector T-cells (Teff) compared to control (DMSO: 10% vs ACY1215: 25% Teff proliferation, p<0.05). To explore whether HDAC inhibition during expansion of tumor infiltrating lymphocytes (TIL) for adoptive transfer would improve their quality and anti-tumor reactivity, TIL isolated from melanoma surgical biopsies were cultured in vitro with IL-2 and ACY1215. Treatment with ACY1215 led to an accumulation of central memory CD4 and CD8 TILs (p<0.01 and p<0.05, respectively), which was maintained even after rapid expansion with anti-CD3 and anti-CD28 stimulation in vitro. Similarly, ACY1215 treatment of T-cells derived from peripheral blood of melanoma patients and healthy donors also displayed an increased central memory phenotype, characterized by expression of CD45RO, CD62L and CCR7 (p<0.05). Inhibition of AKT has been shown to increase T-cells with memory characteristics, and the use of an AKT inhibitor also resulted in accumulation of central memory T-cells. Confirming the observed phenotypic changes, microarray analysis of ACY1215-treated TILs revealed up-regulation of genes associated with a T-cell central memory and inflammatory response (e.g. SELL, LEF1, TNFRSF9) and downregulation of genes associated with Treg function (e.g. LGMN, CXCL8). Collectively these data suggest that reprogramming T-cells with epigenetic modulators may improve melanoma immunotherapy by reducing Treg suppression and production of immunosuppressive cytokines, while favoring generation of central memory T-cells.

Citation Format: Andressa L. Sodre, David M. Woods, Amod Sarnaik, Brian C. Betts, Jeffrey S. Weber. Epigenetic reprogramming of T-cells from metastatic melanoma patients enhances central memory and decreases Th2/Treg phenotypes [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B109.

Abstract A067: PD-1 blockade enhances OX40 expression on regulatory T-cells and decreases suppressive function through induction of phospho-STAT3 signaling

Blockade of the co-inhibitory receptor PD-1 has had unprecedented success in the treatment of metastatic melanoma, with response rates of approximately 40% in previously untreated patients. However, since the majority of patients fail to respond, a better understanding of the mechanisms of action involved in response/resistance and novel approaches to overcome resistance are needed. We evaluated T-cells present in peripheral blood samples of resected stage III/IV melanoma patients treated with adjuvant nivolumab. Data from intra-patient, paired pre-treatment/post-treatment samples showed a significant (p<0.05) increase in phosphorylated STAT3 (pSTAT3) in patients without relapse, but not in patients relapsing. Increases in regulatory T-cells (Tregs) (p<0.05) in relapsers, but not in non-relapsers, and OX40 expression on Tregs (p<0.05) in both relapsers and non-relapsers were also observed. Based on these data we evaluated the ability of PD-1 blocking antibodies to induce pSTAT3 signaling in vitro. Culturing with anti-PD-1 significantly increased levels of pSTAT3 in T-cells, including Tregs, both at the basal state (p<0.05) and post-CD3/CD28 activation (p<0.01). Additionally, culturing T-cells with PD-1 blocking antibodies increased the production of the STAT3 regulated cytokine IL-10 (p<0.05), the number of Tregs (p<0.01) and Treg expression of OX40 (p<0.05). Increases in all these markers/populations were abrogated with the addition of a STAT3 inhibitor (p<0.01). Similar increases in the number of Tregs and the expression of OX40 were also found when T-cells were treated in vitro with recombinant IL-10. Addition of IL-10 neutralizing antibodies ameliorated upregulation of Treg numbers and OX40 expression resulting from PD-1 blockade. Additionally, serum levels of IL-10 were found to be significantly elevated in non-relapsing patients relative to relapsers (p<0.05). RNA-seq analysis comparing Tregs from relapsers to non-relapsers further supported the observed increase in Tregs resulting from nivolumab treatment, with pathway analyses demonstrating significantly increased cell cycle, DNA replication, mitosis and other proliferation related pathways in Tregs from non-relapsed patients. Next we evaluated changes in the function of patient Tregs in an allogenic mixed lymphocyte suppression assay. Tregs from non-relapsers had a significant reduction in suppressive capacity post-nivolumab treatment in paired analyses (p<0.05), while Tregs from relapsers had no significant change. Post-treatment samples from relapses were also found to be significantly more suppressive (p<0.01) than those of non-relapsers. Additionally, decreased percentages of CCR4+CD45RA+ Tregs, previously described as having enhanced suppressive capacity, were found in non-relapsers post-treatment, but not in relapsers. A similar decrease in CCR4+CD45RA+ Tregs was achieved in vitro using OX40 agonist antibodies. Therefore, we propose that PD-1 blockade triggers STAT3 signaling, a hereunto unknown effect. These data support a model in which STAT3 induction by PD-1 blockade results in IL-10 production, which induces proliferation of Tregs with reduced suppressive capacity and triggers OX40 expression. Based on these results and previous findings of others demonstrating that ligation of OX40 expressed on Tregs hinders suppressive capacity, combining OX40 agonist antibodies may enhance the effectiveness of PD-1 blockade by reducing Treg suppression.

Citation Format: David M. Woods, Rupal Ramakrishnan, Andressa L. Sodré, Anders Berglund, Jeffrey Weber. PD-1 blockade enhances OX40 expression on regulatory T-cells and decreases suppressive function through induction of phospho-STAT3 signaling [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A067.

Applying the WHO conceptual framework for the International Classification for Patient Safety to a surgical population

OBJECTIVE

Efforts to improve patient safety are challenged by the lack of universally agreed upon terms. The International Classification for Patient Safety (ICPS) was developed by the World Health Organization for this purpose. This study aimed to test the applicability of the ICPS to a surgical population.

DESIGN

A web-based safety debriefing was sent to clinicians involved in surgical care of abdominal organ transplant patients. A multidisciplinary team of patient safety experts, surgeons and researchers used the data to develop a system of classification based on the ICPS. Disagreements were reconciled via consensus, and a codebook was developed for future use by researchers.

RESULTS

A total of 320 debriefing responses were used for the initial review and codebook development. In total, the 320 debriefing responses contained 227 patient safety incidents (range: 0-7 per debriefing) and 156 contributing factors/hazards (0-5 per response). The most common severity classification was 'reportable circumstance,' followed by 'near miss.' The most common incident types were 'resources/organizational management,' followed by 'medical device/equipment.' Several aspects of surgical care were encompassed by more than one classification, including operating room scheduling, delays in care, trainee-related incidents, interruptions and handoffs.

CONCLUSIONS

This study demonstrates that a framework for patient safety can be applied to facilitate the organization and analysis of surgical safety data. Several unique aspects of surgical care require consideration, and by using a standardized framework for describing concepts, research findings can be compared and disseminated across surgical specialties. The codebook is intended for use as a framework for other specialties and institutions.

Abstract A074: Selective Inhibition of HDAC6 augments T-cell central memory and enhances anti-tumor functions: Implications in TIL therapy

Histone deacetylases (HDACs) are a family of epigenetic modulators responsible for regulating gene expression. As key players in orchestrating both tumor and immune responses, HDACs have received attention for their possible role in cancer immunotherapy. While pan-HDAC inhibitors directly impact tumor growth, their broad targeting can be detrimental to the immune system. In this sense, HDAC selective inhibition becomes attractive as a strategy to minimize off-target effects. Here a novel role of targeting HDAC6 in T-cells with potential implications for melanoma immunotherapy is explored. Adoptive T-cell therapy is an effective treatment for metastatic melanoma, reaching objective clinical responses in half of patients undergoing tumor infiltration lymphocyte (TIL) therapy. However, lack of persistence of reactive T-cells is a major reason why patients fail to sustain long-term responses to treatment. The presence of T-cell memory populations is associated with prolonged responses to TIL. Herein we have shown that HDAC6-selective inhibition by ricolinostat increased the central memory phenotype of human CD4 and CD8 T-cells (p<0.01 and p<0.05, respectively), as indicated by CD45RO, CD45RA, CD62L and/or CCR7 surface markers. While a decrease in the naïve, effector and effector memory subsets occurred, no differences in cell viability were observed. Accordingly, similar ricolinostat-induced central memory enhancement was seen in CD4 and CD8 T-cells from the peripheral blood of melanoma patients (p<0.01 and p<0.05, respectively). Ultimately, ricolinostat led to accumulation of a central memory phenotype for TIL derived from various cell preparations (e.g. tumor digest, pre- and post-rapid expansion in vitro), with p values <0.05. Intriguingly, Th2 cytokine production (i.e. IL-4 p<0.01, IL-6 p<0.001 and IL-10) was impaired in T-cells from melanoma patients treated with ricolinostat, while no differences occurred on IL-2, IFNg, TNF or IL-17a secretion. Functionally, TILs isolated from patient-derived melanoma fragments cultured in the presence of ricolinostat exhibited increased proportion of CD8 T-cells producing IFNg and CD107a cytolytic molecules (50% vs 35%, p<0.05). Moreover, no negative impact on T-cell viability or proliferation was observed following ricolinostat treatment. No detrimental effects were observed in the yield of TIL from melanoma fragments. Cytotoxicity in vitro was also evaluated. Relative to a melanoma only control group, ricolinostat pre-treatment of TILs or concomitantly with tumor cells induced 70% killing of HLA matched melanoma cells, while control-treated TILs resulted in 50% cell death. In vivo, adoptive transfer of rocilinostat-treated murine T-cells improved the anti-melanoma effect in a B16F10 model (day 25 mean tumor volume 800 vs. 2200 cubic mm). Ex vivo characterization of the memory T-cell distribution in the lymph nodes demonstrated increased CD44+CD62L+ T-cells upon HDAC6-selective inhibition (CD8+ 32.8% vs 21.8%; CD4+ 4.71% vs 2.3%), suggesting a role of HDAC6 in the formation or distribution of memory CD4+ and CD8+ T-cells. The results suggest a positive impact of HDAC6-selective inhibition on TIL therapy and the resulting anti-melanoma response in vivo. While further dissection of molecular mechanism(s) is essential, the data described provide a rationale for targeting HDAC6 to augment melanoma immunotherapy.

Citation Format: Andressa Sodre Laino, David M. Woods, Amod Sarnaik, Jeffrey Weber, Eduardo M. Sotomayor. Selective Inhibition of HDAC6 augments T-cell central memory and enhances anti-tumor functions: Implications in TIL therapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A074.

Abstract A066: Histone deacetylase 11 is an epigenetic regulator of T-cell pro-inflammatory function and novel target for enhancing T-cell anti-tumor activity

The efficacy of immunotherapy is dependent on the ability of antigen-specific T-cells to mount a proper anti-tumor response while avoiding a plethora of immunosuppressive mechanisms. Unfortunately, these immunosuppressive mechanisms often overwhelm the T-cell response, resulting in patients failing to respond. Histone deacetylases (HDACs) are a family of epigenetic modifiers named for their ability to remove acetyl groups from lysine residues of histone tails, thereby regulating the chromatin structure and gene expression. Here we report that HDAC11, the most recently discovered HDAC, is a regulator of T-cell pro-inflammatory function. Previous reports have shown HDAC11 expression to be tissue restricted. Consequently, we compared expression levels of HDAC11 using an eGFP reporter mouse, in various immune cells. It was found that T-cells expressed relatively high levels of HDAC11. However, while resting T-cells, both central memory and naïve, had high levels of HDAC11 expression, effector or effector memory T-cells displayed lower levels. Additionally, T-cells experienced rapid down-regulation of HDAC11 upon activation. To expand upon these observations, the function of T-cells from HDAC11KO mice were investigated. Initial experiments revealed no gross changes in the numbers or maturation of T-cells. However, HDAC11KO mice displayed an increased percentage of central memory CD8+ T-cells (p<0.05). Additionally, upon activation these T-cells were more apt to acquire effector status (p<0.001). Upon activation, HDAC11KO T-cells demonstrated a robust increase in IL-2, TNF and IFNγ production (p<0.01), but showed no differences in Th2 or Th17 cytokine production. These T-cells also expressed higher levels of the effector molecules granzyme B and perforin (p<0.01). Moreover, post-activation, CD8+ T-cells lacking HDAC11 also displayed a higher percentage of proliferating cells, and more divisions of proliferating cells (p<0.01). HDAC11KO T-cells displayed higher resistance to proliferative suppression by Tregs and failed to succumb to anergy in a high dose antigen model. Indeed, while OTII T-cells from mice injected with high dose OVA peptide displayed reduced levels of IFNγ production compared to cells from non-injected mice after rechallenge, HDAC11KO/OTII T-cells had an increase in IFNγ production. Mechanistically, T-cells devoid of HDAC11 did not appear to have differences in TCR signaling, but did express higher levels of the transcription factors EOMES and T-bet. Chromatin immunoprecipitation (ChIP) revealed higher basal levels of acetylation of these genes in HDAC11KO mice. ChIP analysis also revealed interactions of HDAC11 at the promoters of both EOMES and T-bet. In a graft vs. host disease (GvHD) model, HDAC11KO T-cells produced a more rapid onset of GvHD, and were able to do so with transfers of cell numbers below that able to induce GvHD using WT T-cells (p<0.01). This GvHD was characterized by greater levels of IFNγ and TNF as well as increased T-cell expansion (p<0.05). In a B16 melanoma model, adoptive transfer of HDAC11KO T-cells resulted in delayed tumor progression (p<0.05) compared to WT T-cells. To begin investigating the clinical potential of these data, the expression levels of HDAC11 were investigated in melanoma tumor sections utilized to grow tumor infiltrating lymphocytes (TIL) for clinical trials of adoptive cell therapy. A reduced level of HDAC11 was found in tumor sections from those patients responding to TIL therapy compared to progressing patients (p<0.01). Collectively, beyond demonstrating HDAC11 as a novel epigenetic regulator of T-cell pro-inflammatory function, these results highlight HDAC11 as a novel target for enhancing the efficacy of immunotherapy.

Citation Format: David M. Woods, Andressa L. Sodre, Karrune Woan, Alejandro Villagra, Amod Sarnaik, Jeffrey Weber, Eduardo M. Sotomayor. Histone deacetylase 11 is an epigenetic regulator of T-cell pro-inflammatory function and novel target for enhancing T-cell anti-tumor activity. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A066.

Abstract B19: Targeting histone deacetylase 6 in T-cells to improve melanoma immunotherapy

This abstract is being presented as a short talk in the scientific program. A full abstract is printed in the Proffered Abstracts section (PR09) of the Conference Proceedings.

Citation Format: Andressa Sodre Laino, David M. Woods, Esteban Celis, Jeffrey Weber, Eduardo Sotomayor. Targeting histone deacetylase 6 in T-cells to improve melanoma immunotherapy. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B19.

Abstract PR09: Targeting histone deacetylase 6 in T-cells to improve melanoma immunotherapy

Epigenetic modifications are a major component of regulating cell biology and, thus, have raised attention for their implications in cancer immunotherapies. In this regard, histone deacetylases (HDACs) have emerged as key players in orchestrating both tumor and immune response. Particularly HDAC6 has been identified as modulating the regulatory T-cell suppressive activity through HSP90. The uniqueness of HDAC6 in containing two enzymatic pockets allows the development of isotype-specific small molecule inhibitors. Here a novel role of HDAC6 in regulating anti-melanoma response is exploited and shown to have positive implications for tumor infiltration lymphocyte (TIL) therapy. Initially HDAC6 expression was evaluated in T-cell subsets from mouse, healthy human cells and melanoma patients. HDAC6 expression was decreased after T-cell activation as well as in the central memory TILs subset when compared to its naïve counterpart. To further investigate the role(s) of HDAC6 in T-cell anti-tumor responses, an HDAC6KO mouse model was utilized. Despite having normal lymphocyte compartments, melanoma growth was significantly delayed in HDAC6KO when comparing to age-, sex-match wild-type (WT) mice. Tumor-free HDAC6KO mice also displayed an enhanced T-cell response following melanoma-peptide vaccination, characterized by a less pronounced contraction phase of antigen-specific CD8+ T-cells. When systemically treated with the HDAC6 specific inhibitor ACY-1215, tumor growth was slightly reduced in melanoma-bearing mice. To address whether this was a direct effect on T-cell response, WT T-cells treated ex vivo with ACY-1215 were adoptively transferred to tumor-bearing WT mice. It was found that HDAC6 inhibition improved in vivo anti-tumor response and led to a modest accumulation of central memory T-cells in the lymph nodes. To further expand these results with a potential clinical application, previously frozen TILs from melanoma patients were thawed and treated with ACY-1215 during expansion in vitro. Accordingly, HDAC6 inhibition increased the percent of both CD8+ and CD4+ central memory T-cell subsets, as indicated by CD45RO, CD45RA, CCR7 and CD62L surface markers. To build upon these results, the expression of transcription factors involved in T-cell differentiation and polarization were evaluated. The transcription factor T-BET was found to be up-regulated in CD4+ and CD8+ TILs after in vitro expansion and treatment with ACY-1215, while there was a mild decrease in expression of GATA3 and RORgT in CD4+ TILs. This data is suggestive of CD4+ TIL polarization towards a pro-inflammatory Th1 phenotype. Moreover, both CD4+ and CD8+ TILs expanded and treated with ACY-1215 displayed enhanced Ki67 expression compared to the control treatment group, indicating higher proliferative capacity as a result of HDAC6 inhibition. To address if ACY-1215 treatment could ultimately improve T-cell cytotoxicity against melanoma, TILs from one melanoma patient were treated with ACY-1215 at the same time of in vitro expansion and then co-cultured with HLA matched melanoma. Treatment of TILs with ACY-1215 resulted in 20% more killing of target cells than the control group. The data presented so far suggests a positive effect of HDAC6 inhibition in generating and maintaining anti-tumor and peptide vaccination responses in vivo. While further investigation of cellular and molecular mechanisms is necessary, the results herein described provide rationale for targeting HDAC6 to improve cancer immunotherapy.

This abstract is also presented as Poster B19.

Citation Format: Andressa Sodre Laino, David M. Woods, Esteban Celis, Jeffrey Weber, Eduardo Sotomayor. Targeting histone deacetylase 6 in T-cells to improve melanoma immunotherapy. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr PR09.

HDAC Inhibition Upregulates PD-1 Ligands in Melanoma and Augments Immunotherapy with PD-1 Blockade

Expression of PD-1 ligands by tumors and interaction with PD-1-expressing T cells in the tumor microenvironment can result in tolerance. Therapies targeting this coinhibitory axis have proven clinically successful in the treatment of metastatic melanoma, non-small cell lung cancer, and other malignancies. Therapeutic agents targeting the epigenetic regulatory family of histone deacetylases (HDAC) have shown clinical success in the treatment of some hematologic malignancies. Beyond direct tumor cell cytotoxicity, HDAC inhibitors have also been shown to alter the immunogenicity and enhance antitumor immune responses. Here, we show that class I HDAC inhibitors upregulated the expression of PD-L1 and, to a lesser degree, PD-L2 in melanomas. Evaluation of human and murine cell lines and patient tumors treated with a variety of HDAC inhibitors in vitro displayed upregulation of these ligands. This upregulation was robust and durable, with enhanced expression lasting past 96 hours. These results were validated in vivo in a B16F10 syngeneic murine model. Mechanistically, HDAC inhibitor treatment resulted in rapid upregulation of histone acetylation of the PD-L1 gene leading to enhanced and durable gene expression. The efficacy of combining HDAC inhibition with PD-1 blockade for treatment of melanoma was also explored in a murine B16F10 model. Mice receiving combination therapy had a slower tumor progression and increased survival compared with control and single-agent treatments. These results highlight the ability of epigenetic modifiers to augment immunotherapies, providing a rationale for combining HDAC inhibitors with PD-1 blockade.

Abstract 1338: Novel implications of histone deacetylase 6 selective inhibition in melanoma T-cell immunotherapy

Adoptive T-cell therapy is an effective treatment for metastatic melanoma, achieving objective clinical responses in half of patients undergoing tumor infiltration lymphocyte (TIL) therapy. Epigenetic modifications are key players in regulating gene expression. Modulation of histone deacetylases (HDACs) has received attention for its implications in altering gene regulation. While HDAC pan-inhibition directly affects tumor growth, the immune system may be negatively impacted. Novel HDAC-selective inhibitors can ameliorate these undesirable effects. HDAC6 is unique in containing two catalytic domains, allowing for the development of isotype-selective inhibitors. Here a novel role of HDAC6 in T-cell immunity with important implications for adoptive cell therapy was explored. Initially a delay in B16 melanoma growth was observed in HDAC6KO mice (p<0.001 at day 19). Furthermore, tumor-free HDAC6KO mice vaccinated with melanoma antigen peptides displayed a mean of 30% antigen-specific circulating CD8+ T-cells versus 12% in WT mice. Moreover, HDAC6 expression was reduced over three fold in T-cells activated in vitro. To further investigate the role(s) of HDAC6 in anti-tumor T-cell responses, the HDAC6 selective inhibitor rocilinostat was utilized. Adoptive transfer of rocilinostat-treated T-cells conferred an increased anti-melanoma response in a B16 model (day 25 mean tumor volume 800 vs. 2200 cubic mm), characterized by accumulation of central memory T-cells in the lymph nodes. To directly address the clinical potential of targeting HDAC6, T-cells from healthy human donors and melanoma patient-derived TILs were treated with rocilinostat. A modest but consistent 5% increase in central memory phenotype in healthy CD4+ and CD8+ T-cells was observed. While a decrease in the naïve, effector and effector memory subsets occurred, no differences in cell viability were seen. Rocilinostat treatment of TILs derived from different cell preparations (e.g. tumor digest, pre- and post-rapid expansion in vitro) displayed up to a three-fold increase in central memory in three patients analyzed. Impressively, repeated in vitro treatment with rocilinostat further increased the proportion of central memory CD4+ and CD8+ T-cells. Intriguingly, initial results show that the transcription factor T-BET, involved in T-cell function, was upregulated in TILs after rocilinostat treatment and in vitro expansion. Functionally, activation of rocilinosat-treated TILs resulted in increased IFNg+CD107a+ T-cells. Ultimately, rocilinostat pre-treatment of TILs or concomitantly with tumor resulted in 70% killing of HLA matched melanoma cells, compared to 50% killing by control-treated TILs, both relative to melanoma only control. These preliminary data provide a rationale for targeting HDAC6 in T-cells to improve cancer immunotherapy.

Citation Format: Andressa Sodre Laino, David M. Woods, Amod Sarnaik, Esteban Celis, Jeffrey Weber, Eduardo M. Sotomayor. Novel implications of histone deacetylase 6 selective inhibition in melanoma T-cell immunotherapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1338. doi:10.1158/1538-7445.AM2015-1338

Abstract 257: Class I HDAC inhibition upregulates PD-1 ligands in melanoma and increases the efficacy of PD-1 blockade

Ligation of co-inhibitory molecules such as PD-L1/PD-1 are known mechanisms of tumor escape. Blockade of this specific pathway with antibodies against PD-1 has proven effective in the treatment of metastatic melanoma, with response rates of 30-40% (Topalian, SL et al. 2012). However, since the majority of patients fail to respond, approaches to augment the efficacy of this approach are needed. We report herein that histone deacetylase (HDAC) inhibitors against class I HDACs generate robust and durable upregulation of PD-L1 and PD-L2 in melanoma cell lines as well as patient tumor samples. Combining the HDAC inhibitor LBH589 with PD-1 blockade in a murine melanoma model results in delayed tumor growth and increased survival, superior to either single agent. Initially, we evaluated the expression of PD-L1 by flow cytometry on several melanoma cell lines treated with the HDAC inhibitors LBH589, MS275 and MGCD0103. At 72 hours, all treatments resulted in increased PD-L1 surface expression. As a follow-up, additional inhibitors and time points were assessed. Upregulation was seen at 24 hours after treatment and continued past 96 hours. However, these effects were not observed with HDAC6 or class IIa specific inhibitors. We then evaluated a larger panel of HDACi on several patient derived melanomas. We observed dose dependent upregulation with all inhibitors with inhibition of HDAC1, HDAC2 and/or HDAC3, but no impact of HDAC6, HDAC8 or class IIa specific inhibitors. Additionally, we observed low level, but consistent upregulation of PD-L2 in conjunction with PD-L1. These in vitro results were validated in vivo using a B16 murine melanoma model and patient xenografts in SCID mice. Chromatin immunoprecipitation analysis shows that treatment of melanoma with an HDAC inhibitor results in increased histone acetylation at the PD-L1 promoter. Previous studies have demonstrated PD-L1 regulation by STAT3 (Wolfle SJ et al. 2011), in addition to HDAC inhibitor alteration of STAT3 activation (Gupta M. et al 2012). We are currently evaluating alterations in STAT3 signaling in HDAC inhibitor treated melanoma. Given the anti-melanoma properties of LBH589 and its augmentation of immunogenicity previously reported by our group, combination therapy using PD-1 blocking antibodies with LBH589 was explored. Treatment of B16 melanoma-bearing C57BL/6 mice with the combination resulted in tumor progression delay (p = 0.01) compared to control and single agent treatments. Accompanying this tumor delay was an increase in overall survival (p = 0.03). These results highlight the ability of epigenetic modifying agents to augment immunogenicity and increase the efficacy of current immunotherapies. These results provide a strong rationale for combining LBH589 with PD-1 blockade for the treatment of metastatic melanoma.

Citation Format: David M. Woods, Andressa L. Sodre, Amod Sarnaik, Eduardo M. Sotomayor, Jeffrey Weber. Class I HDAC inhibition upregulates PD-1 ligands in melanoma and increases the efficacy of PD-1 blockade. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 257. doi:10.1158/1538-7445.AM2015-257

Targeting histone deacetylase 6 mediates a dual anti-melanoma effect: Enhanced antitumor immunity and impaired cell proliferation

The median survival for metastatic melanoma is in the realm of 8-16 months and there are few therapies that offer significant improvement in overall survival. One of the recent advances in cancer treatment focuses on epigenetic modifiers to alter the survivability and immunogenicity of cancer cells. Our group and others have previously demonstrated that pan-HDAC inhibitors induce apoptosis, cell cycle arrest and changes in the immunogenicity of melanoma cells. Here we interrogated specific HDACs which may be responsible for this effect. We found that both genetic abrogation and pharmacologic inhibition of HDAC6 decreases in vitro proliferation and induces G1 arrest of melanoma cell lines without inducing apoptosis. Moreover, targeting this molecule led to an important upregulation in the expression of tumor associated antigens and MHC class I, suggesting a potential improvement in the immunogenicity of these cells. Of note, this anti-melanoma activity was operative regardless of mutational status of the cells. These effects translated into a pronounced delay of in vivo melanoma tumor growth which was, at least in part, dependent on intact immunity as evidenced by the restoration of tumor growth after CD4+ and CD8+ depletion. Given our findings, we provide the initial rationale for the further development of selective HDAC6 inhibitors as potential therapeutic anti-melanoma agents.

Abstract 643: The histone deacetylase inhibitor Quisinostat augments the anti-tumor reponses of T-cells: Implications in adoptive cell therapy

It has become increasingly clear that histone deacetylases (HDACs), a family of epigenetic modifiers, play intimate roles in both tumor and immune biology. Indeed, two HDAC inhibitors (HDACi) are FDA approved for the treatment of cutaneous T-cell leukemia, and various others are currently undergoing clinical trials for the treatment of both solid and hematological malignancies. Beyond direct anti-tumor effects, HDACi have shown pronounced abilities to augment the immunogenicity of tumor cells leading to an improved ant-tumor immune response. Furthermore, in addition to anti-tumor effects, several studies have demonstrated a profound ability of HDACi to tip the scale between tolerance and inflammation in antigen presenting cells, leading to enhanced T-cell activation. However, less well studied is the ability of HDACi to directly influence the function and fate of T-cells. Here we report that the HDACi JNJ-264-81585 (Quisinostat) is able to augment the pro-inflammatory phenotype of T-cells in vitro and in vivo. Quisinostat is a hydroxamic acid with potent sub-nanomolar inhibition of several HDACs, and reported anti-tumor activity. Here we report that Quisinostat has a potent HDAC inhibition in T-cells, with sub-nanomolar doses increasing histone 3 acetylation levels in a dose dependent manner. Intriguingly, when treated with Quisinostat in vitro, activated murine CD4+ and CD8+ T-cells produced significantly higher levels of the pro-inflammatory cytokines IL-2, IFN-g, and TNF. Concomitantly, treated T-cells produced decreased levels of IL-6 and IL-17. To determine the efficacy of Quisinostat at augmenting T-cell function in vivo, a novel T-cell adoptive transfer model was utilized. In this model syngeneic T-cells from B6.SJL mice were stained with the proliferation tracking dye CellTrace™ Violet and activated in the presence of Quisinostat, then subsequently adoptively transferred into sub-lethally irradiated C57BL/6 recipient mice. Analysis of proliferation of transferred T-cells showed that CD8+ T-cells treated with Quisinostat had significantly higher rates of proliferation than those treated with DMSO control. As well, in a result similar to that seen in vitro, adoptively transferred T-cells had skewing towards a predominantly CD8+ composition. Finally, T-cells treated with Quisinostat displayed a reconstitution advantage over DMSO treated cells, with higher percentages of transferred T-cells relative to endogenous T-cells. Collectively, these results demonstrate a profound and important ability of HDAC inhibition to modulate the T-cell response, highlighting a role of HDACi, particularly Quisinostat, in augmenting the efficacy of adoptive cell therapy, giving rationale for clinical investigation.

Citation Format: David M. Woods, Andressa L. Sodre, Jason B. Brayer, Eduardo M. Sotomayor. The histone deacetylase inhibitor Quisinostat augments the anti-tumor reponses of T-cells: Implications in adoptive cell therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 643. doi:10.1158/1538-7445.AM2014-643

Abstract 4090: Inhibition of class I histone deacetylases promotes robust and durable enhancement of PDL1 expression in melanoma: Rationale for combination therapy

Histone deacetylase inhibitors (HDACi) have shown remarkable anti-tumor activity, leading to FDA approval of two HDACi for the treatment of CTCL and several others currently at various stages of clinical development for the treatment of both solid and hematological malignancies. Previous work from our lab has shown that treatment with HDACi results in increased expression of pro-inflammatory promoting surface markers on melanoma cells, promoting enhanced T-cell activation. Recent clinical trial data has shown that blockade of the PD1/PDL1 interaction is effective in the treatment of melanoma, renal cell and non-small cell lung cancer. Importantly, responses to PD1 blocking antibodies were preferentially seen in patients with tumors expressing PDL1. Here we report that HDACi targeting class I HDACs, but not class II, augments expression of PDL1 in melanoma cells. Two murine and five human melanoma cell lines were treated for up to 72 hours with DMSO, LBH589 (pan-HDACi), MS275 (class I inhibitor), MGCD0103 (class I inhibitor), an HDAC6 specific inhibitor, or a class IIa inhibitor. Using flow cytometry, dose dependent, increases in PDL1 expression were found in the LBH589, MS275 and MGCD0103 treated groups, but not in those receiving HDAC6i or class IIa inhibitor, relative to DMSO. Increased expression was noted as early as 24 hours after treatment and peaked at 72 to 96 hours post-treatment. As IFN-γ is known to upregulate the expression of PDL1 in both normal and transformed cells, we evaluated whether these results were associated with induction of IFN-γ expression by the melanoma cells. However, no detectable levels of IFN-γ were seen in either non-treated, class I HDACi, or class II HDACi-treated cells. Melanoma cells treated with HDACi in addition to IFN-γ have enhanced expression of PDL1 relative to either treatment alone. To further gain insight into the specific HDAC regulating the expression of PDL1, preliminary experiments utilizing knockdowns (KD) of individual class I HDACs were performed. In all KD melanoma cells no increase in PDL1 expression was seen, suggesting that the increased expression of PDL1 is dependent on inhibition of multiple class I HDACs. Supporting this conclusion, treatment of class I HDAC-KDs with HDACi recapitulates the increased PDL1 expression seen with WT melanoma. Finally, in preliminary in vivo experiments combining treatment of melanoma bearing mice with anti-PDL1 antibodies, mice receiving the combination treatment had a survival advantage over those receiving PDL1 blocking antibodies or HDACi alone. These results provide a strong rationale for the evaluation of combination therapies utilizing PDL1 or PD1 blocking antibodies in combination with HDACi. Furthermore, these results support the need for further development and investigation of iso-specific HDACi in order to obtain more directed therapeutic efficacy.

Citation Format: David M. Woods, Andressa L. Sodre, Eva Sahakian, John Powers, Maritza Lienlaf-Moreno, Patricio Perez-Villarroel, Alejandro Villagra, Javier Pinilla-Ibarz, Eduardo Sotomayor. Inhibition of class I histone deacetylases promotes robust and durable enhancement of PDL1 expression in melanoma: Rationale for combination therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4090. doi:10.1158/1538-7445.AM2014-4090

Abstract 2564: Histone deacetylase 6 is a novel target for enhancing T-cell function during anti-tumor response and tumor-peptide vaccination

Histone deacetylases (HDACs) are a family of epigenetic regulators with emerging roles in both tumor and immune system biology. In particular, HDAC6 has been reported to modulate the acetylation HSP90, a regulator of regulatory T-cell (Treg) suppressive activity (de Zoeten, Mol Cel Biol, 2011). Here we report a novel role of HDAC6 in T-cell activation and response against tumor or peptide vaccine. Initially the relative expression of HDAC6 was evaluated in mouse and human T-cells, revealing decreased expression of this HDAC following CD3/CD28 stimulation. To further investigate the role(s) of HDAC6 in T-cell function, an HDAC6KO mouse model was utilized. Characterization of the T-cell compartments of the HDAC6KO mouse model showed a slight, but statistically significant increase in CD4+ T-cell population in the lymph nodes at the expense of a decreased percentage of CD8+ T-cells. Further investigation using isotype-specific HDAC6 inhibitors showed similar results when WT T-cells were activated and treated with an HDAC6 inhibitor. In addition to this population skewing, HDAC6 inhibition led to an enhanced expression of CD69 in WT CD4+ T-cells. This result was reproduced in human CD4+ T-cells, indicating a role of HDAC6 in regulating T-cell activation. To evaluate advantages of HDAC6 inhibition for tumor immunotherapy, melanoma-bearing mice were adoptively transferred with T-cells activated and treated with an HDAC6 inhibitor. Ex vivo analysis of memory T-cell distribution in the lymph nodes demonstrated an increased percent of CD44+CD62L+ T-cells upon HDAC6 inhibition, suggesting a role of HDAC6 in the formation or distribution of memory CD4+ and CD8+ T-cells. In a separate experiment, HDAC6KO mice inoculated with melanoma presented significantly delayed tumor growth. Additionally, in a tumor-peptide vaccination model, HDAC6KO mice displayed a remarkably reduced contraction phase in the antigen-specific CD8+ T-cell compartment when compared to WT mice after peptide vaccine administration. To further evaluate whether these in vivo responses were dependent on T-cells, WT or lympho-deficient, lymphoma-bearing mice were treated with an HDAC6 inhibitor. HDAC6 inhibition led to reduced tumor burden in WT mice, which was absent in lympho-deficient mice, highlighting the importance of lymphocytes in the aforementioned in vivo results. Thus, the role of HDAC6 in regulating immune cells during anti-tumor response appears to be more important than the previously reported role as a regulator of Treg function. The data presented demonstrates a positive effect of HDAC6 in T-cell activation, maintenance of anti-tumor response in vivo and persistence of reactive T-cells following peptide vaccination. The results herein described have revealed an unexplored role of HDAC6 with positive implications for cancer immunotherapy, warranting further investigation.

Citation Format: Andressa S. Laino, David M. Woods, Fengdong Cheng, HongWei Wang, Eduardo M. Sotomayor. Histone deacetylase 6 is a novel target for enhancing T-cell function during anti-tumor response and tumor-peptide vaccination. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2564. doi:10.1158/1538-7445.AM2014-2564

Histone deacetylase 11: A novel epigenetic regulator of myeloid derived suppressor cell expansion and function

Myeloid-derived suppressor cells (MDSCs), a heterogeneous population of cells capable of suppressing anti-tumor T cell function in the tumor microenvironment, represent an imposing obstacle in the development of cancer immunotherapeutics. Thus, identifying elements essential to the development and perpetuation of these cells will undoubtedly improve our ability to circumvent their suppressive impact. HDAC11 has emerged as a key regulator of IL-10 gene expression in myeloid cells, suggesting that this may represent an important targetable axis through which to dampen MDSC formation. Using a murine transgenic reporter model system where eGFP expression is controlled by the HDAC11 promoter (Tg-HDAC11-eGFP), we provide evidence that HDAC11 appears to function as a negative regulator of MDSC expansion/function in vivo. MDSCs isolated from EL4 tumor-bearing Tg-HDAC11-eGFP display high expression of eGFP, indicative of HDAC11 transcriptional activation at steady state. In striking contrast, immature myeloid cells in tumor-bearing mice display a diminished eGFP expression, implying that the transition of IMC to MDSC's require a decrease in the expression of HDAC11, where we postulate that it acts as a gate-keeper of myeloid differentiation. Indeed, tumor-bearing HDAC11-knockout mice (HDAC11-KO) demonstrate a more suppressive MDSC population as compared to wild-type (WT) tumor-bearing control. Notably, the HDAC11-KO tumor-bearing mice exhibit enhanced tumor growth kinetics when compare to the WT control mice. Thus, through a better understanding of this previously unknown role of HDAC11 in MDSC expansion and function, rational development of targeted epigenetic modifiers may allow us to thwart a powerful barrier to efficacious immunotherapies.

The antimelanoma activity of the histone deacetylase inhibitor panobinostat (LBH589) is mediated by direct tumor cytotoxicity and increased tumor immunogenicity

Melanoma is the deadliest skin cancer, and its incidence has been increasing faster than any other cancer. Although immunogenic, melanoma is not effectively cleared by host immunity. In this study, we investigate the therapeutic, antimelanoma potential of the histone deacetylase inhibitor (HDACi) panobinostat (LBH589) by assessing both its cytotoxic effects on melanoma cells as well as enhancement of immune recognition of melanoma. Utilizing murine and human melanoma cell lines, we analyzed the effects of LBH589 on proliferation and survival. In addition, we analyzed the expression of several immunologically relevant surface markers and melanoma differentiation antigens, and the ability of LBH589-treated melanoma to activate antigen-specific T cells. Finally, we assessed the in-vivo effects of LBH589 in a mouse melanoma model. Low nanomolar concentrations of LBH589 inhibit the growth of all melanoma cell lines tested, but not normal melanocytes. This inhibition is characterized by increased apoptosis as well as a G1 cell cycle arrest. In addition, LBH589 augments the expression of major histocompatibility complex and costimulatory molecules on melanoma cells leading to an increased ability to activate antigen-specific T cells. Treatment also increases expression of melanoma differentiation antigens. In vivo, LBH589 treatment of melanoma-bearing mice results in a significant increase in survival. However, in immunodeficient mice, the therapeutic effect of LBH589 is lost. Taken together, LBH589 exerts a dual effect upon melanoma cells by affecting not only growth/survival but also by increasing melanoma immunogenicity. These effects provide the framework for future evaluation of this HDAC inhibitor in melanoma treatment.

Abstract 3554: The histone deacetylase inhibitor LBH589 augments anti-tumor immunity through direct effects on tumor and immune cells leading to impaired tumor progression in vivo

Overcoming immune tolerance is critical for the development of effective immunotherapy against cancer. Tumor cells induce tolerance through a variety of modalities including the secretion of IL-10 and TGF-β, the expression of inhibitory ligands, and the generation of cells with regulatory properties. Epigenetic modifiers have gained special attention due to their ability to modify immune regulatory pathways. In this context, a group of chemical compound collectively named histone deacetylase inhibitors (HDACi) have recently been shown to modulate tumor cell immunogenicity, adding a new property to their already well-documented cytotoxic effect against transformed cells. LBH589 is a potent, pan-HDACi that has been used in clinical trials for the treatment of several hematological malignancies. Here, we provide evidence of the anti-melanoma effect of LBH589 through its direct effects upon tumor cells as well as its modulatory effects upon immune cells. Indeed, treatment of human and murine melanoma cells in vitro with LBH589 resulted in inhibition of melanoma proliferation, characterized by cell cycle arrest in G1. Moreover, we found that LBH589 enhances the expression of MHC class I and II molecules on melanoma cells, which is critical for immune recognition. In addition, LBH589 treatment inhibits the production of IL-10, while enhancing the secretion of pro-inflammatory cytokines such as IL-12 and the expression of the costimulatory molecule B7.2 on antigen-presenting cells (APCs). LBH-treated APCs also displayed an enhanced capability to activate naïve antigen-specific T-cells as evidenced by their increased production of IL-2 and IFN-γ. More importantly, LBH589-treated APCs also restored the function of anergic T-cells isolated from tumor bearing mice. Finally, in vivo treatment of B16 melanoma bearing mice with LBH589 resulted in a substantial decrease in tumor growth when compared to vehicle-control treated mice (mean 602mm3 vs. 1316mm3, respectively). In conclusion, the dual ability of the pan-HDACi LBH589 to target both melanoma cells and to enhance anti-tumor immune responses provides the rationale for evaluating this compound either alone or in combination with immune enhancing therapeutic approaches (eg, CTLA4 blockade) for melanoma treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3554. doi:1538-7445.AM2012-3554

Puccinia jaceae var. solstitialis teliospore priming on yellow starthistle

Following the introduction of Puccinia jaceae var. solstitialis to California for biological control of yellow starthistle (Centaurea solstitialis, Asteraceae), teliospores, pycnia, and multiple urediniospore generations have been observed in the field. Because urediniospores have a relatively short life span in the field, functioning teliospores are expected to be necessary for the permanent establishment of P. jaceae var. solstitialis in California. To determine if conditions in California were conducive to this, teliospore emergence and priming were evaluated in the field. A factorial experiment in the laboratory with five incubation times and three incubation temperatures was used to determine teliospore priming requirements. Teliospore production coincided with plant senescence in August and September at two sites in 2 years; fewer teliospores were produced in 2006, suggesting inconsistent teliospore production may limit population growth and contribute to local extinctions in some areas. When teliospores were primed in the field, germination was low through the fall and abruptly peaked in January during both years. In the laboratory, teliospore germination increased as incubation time increased from 2 to 6 weeks and temperatures decreased from 12 to 4 degrees C. A degree-hour model derived from laboratory data accurately predicts when teliospores are primed for germination in the field. Based on the results obtained in this study, it is apparent that teliospore germination can occur over a range of priming conditions. However, lower temperatures and longer incubation periods are superior in breaking teliospore dormancy.

Anatomy of a patient safety event: a pediatric patient safety taxonomy

BACKGROUND

Idiosyncratic terminology and frameworks in the study of patient safety have been tolerated but are increasingly problematic. Agreement on standard language and frameworks is needed for optimal improvement and dissemination of knowledge about patient safety.

METHODS

Patient safety events were assessed using critical incident analysis, a method used to classify risks that has been more recently applied to medicine. Clinician interviews and clinician reports to a web based reporting system were used for analysis of hospital based and ambulatory care events, respectively. Events were classified independently by three investigators.

RESULTS

A pediatric patient safety taxonomy, relevant to both hospital based and ambulatory pediatric care, was developed from the analysis of 122 hospital based and 144 ambulatory care events. It is composed of four main categories: (1) problem type; (2) domain of medicine; (3) contributing factors in the patient (child-specific), environment (latent conditions) and care providers (human factors); and (4) outcome or result of the event and level of harm. A classification of preventive mechanisms was also developed. Inter-rater reliability of classifications ranged from 72% to 86% for sub-categories of the taxonomy.

CONCLUSIONS

This patient safety taxonomy reflects the nature of events that occur in both pediatric hospital based and ambulatory care settings. It is flexible in its construction, permits analysis to begin at any point, and depicts the relationships and interactions of elements of an event.

First Report of Musk Thistle Rust (Puccinia carduorum) in California and Nevada

Musk thistle, Carduus nutans L., is an introduced weed of pastures, rangelands, and natural areas in much of North America. Puccinia carduorum Jacky, an autoecious rust fungus from Turkey, has been evaluated for biological control of musk thistle since 1978, including a field study near Blacksburg, VA, from 1987 to 1990. After release of the fungus in Virginia, rusted musk thistle was found in eight eastern states by 1992, in Missouri by 1994 (1), and in Oklahoma by 1997 (2). A rust disease was discovered on musk thistle near Mt. Shasta, CA, on 22 September 1998, and near Mogul, NV, on 12 August 1999. The pathogen was identified as P. carduorum on the basis of pathogenicity on musk thistle and urediniospore morphology (ovate spores, 21 μm diameter, three germ pores equatorial in location, and echinulations over the upper two-thirds to three-quarters of urediniospores). Ribosomal RNA internal transcribed spacer DNA sequences (ITS1 and ITS2) were identical to those from the isolate obtained after the field release in Virginia, verifying that the California isolate is P. carduorum. The initial California infestation was observed on a few plants late in the season, and by September 2000, nearly 100% of plants were infected. The occurrence of P. carduorum in California is apparently the result of natural, unaided spread of the fungus on musk thistle from the East Coast of the United States. References: (1) A. B. A. M. Baudoin and W. L. Bruckart. Plant Dis. 80:1193, 1996. (2) L. J. Littlefield et al. Plant Dis. 82:832, 1998.

Experimental enhancement of drug uptake using short-term flow occlusion: a comparison of balloon and tourniquet techniques

Three groups of dogs, four per group, were used to examine the safety of short-term arterial flow occlusion and potential benefits of balloon and/or tourniquet occlusion-infusion techniques. In part 1, local plasma gases and pH were monitored during a 1-hr period of vascular occlusion. Tourniquet occlusion was found to significantly (p = 0.01) lower pO2. In part 2, local muscle and venous blood samples were obtained during and after a 30-min intraarterial infusion of floxuridine (FUDR). A tourniquet was added to try to eliminate collateral circulation. Local FUDR concentration was increased by 1.3 times in muscle and 19.6 times (p less than 0.01) in ipsilateral femoral vein serum when a tourniquet was added to arterial balloon occlusion-infusion. In addition, the combination of the two occlusion techniques produced a 4.1-fold reduction (p less than 0.05) in systemic venous FUDR levels during infusion when compared to balloon occlusion.