Longitudinal assessment of tumor-infiltrating lymphocytes in primary breast cancer following neoadjuvant radiotherapy

BACKGROUND

Tumor-infiltrating lymphocytes (TILs) have prognostic significance in several cancers, including breast. Despite interest in combining radiotherapy with immunotherapy, little is known about the effect of radiotherapy itself on the tumor-immune microenvironment, including TILs. Here, we interrogated longitudinal dynamics of tumor-infiltrating and systemic lymphocytes in patient samples taken before, during, and after neoadjuvant radiotherapy (NART), from XXX and XXX breast clinical trials.

METHODS

We manually scored stromal TILs (sTILs) from longitudinal tumor samples using standardized guidelines, as well as deep learning-based scores at cell-level (cTIL) and cell- and tissue-level combination analysis (SuperTIL). In parallel, we interrogated absolute lymphocyte counts from routine blood tests at corresponding timepoints during treatment. Exploratory analyses studied the relationship between TILs and pathological complete response (pCR) and long-term outcomes.

RESULTS

Patients receiving NART experienced a significant and uniform decrease in sTILs that did not recover at the time of surgery (P < 0.0001). This lymphodepletive effect was also mirrored in peripheral blood. Our "SuperTIL" deep learning score showed good concordance with manual sTILs, and importantly performed comparably to manual scores in predicting pCR from diagnostic biopsies. Analysis suggested an association between baseline sTILs and pCR, as well as sTILs at surgery and relapse, in patients receiving NART.

CONCLUSIONS

This study provides novel insights into TIL dynamics in the context of NART in breast cancer, and demonstrates the potential for artificial intelligence to assist routine pathology. We have identified trends which warrant further interrogation and have a bearing on future radio-immunotherapy trials.

Tumour immune escape via P2X7 receptor signalling

While P2X7 receptor expression on tumour cells has been characterized as a promotor of cancer growth and metastasis, its expression by the host immune system is central for orchestration of both innate and adaptive immune responses against cancer. The role of P2X7R in anti-tumour immunity is complex and preclinical studies have described opposing roles of the P2X7R in regulating immune responses against tumours. Therefore, few P2X7R modulators have reached clinical testing in cancer patients. Here, we review the prognostic value of P2X7R in cancer, how P2X7R have been targeted to date in tumour models, and we discuss four aspects of how tumours skew immune responses to promote immune escape via the P2X7R; non-pore functional P2X7Rs, mono-ADP-ribosyltransferases, ectonucleotidases, and immunoregulatory cells. Lastly, we discuss alternative approaches to offset tumour immune escape via P2X7R to enhance immunotherapeutic strategies in cancer patients.

Immunotherapy targeting different immune compartments in combination with radiation therapy induces regression of resistant tumors

Radiation therapy (RT) increases tumor response to CTLA-4 inhibition (CTLA4i) in mice and in some patients, yet deep responses are rare. To identify rational combinations of immunotherapy to improve responses we use models of triple negative breast cancer highly resistant to immunotherapy in female mice. We find that CTLA4i promotes the expansion of CD4+ T helper cells, whereas RT enhances T cell clonality and enriches for CD8+ T cells with an exhausted phenotype. Combination therapy decreases regulatory CD4+ T cells and increases effector memory, early activation and precursor exhausted CD8+ T cells. A combined gene signature comprising these three CD8+ T cell clusters is associated with survival in patients. Here we show that targeting additional immune checkpoints expressed by intratumoral T cells, including PD1, is not effective, whereas CD40 agonist therapy recruits resistant tumors into responding to the combination of RT and CTLA4i, indicating the need to target different immune compartments.

The interplay between the DNA damage response and ectonucleotidases modulates tumor response to therapy

The extracellular nucleoside adenosine reduces tissue inflammation and is generated by irreversible dephosphorylation of adenosine monophosphate (AMP) mediated by the ectonucleotidase CD73. The pro-inflammatory nucleotides adenosine triphosphate, nicotinamide adenine dinucleotide, and cyclic guanosine -monophosphate-AMP (cGAMP), which are produced in the tumor microenvironment (TME) during therapy-induced immunogenic cell death and activation of innate immune signaling, can be converted into AMP by ectonucleotidases CD39, CD38, and CD203a/ENPP1. Thus, ectonucleotidases shape the TME by converting immune-activating signals into an immunosuppressive one. Ectonucleotidases also hinder the ability of therapies including radiation therapy, which enhance the release of pro-inflammatory nucleotides in the extracellular milieu, to induce immune-mediated tumor rejection. Here, we review the immunosuppressive effects of adenosine and the role of different ectonucleotidases in modulating antitumor immune responses. We discuss emerging opportunities to target adenosine generation and/or its ability to signal via adenosine receptors expressed by immune and cancer cells in the context of combination immunotherapy and radiotherapy.

IMMU-12. Exploring and modulating the tumour immune microenvironment to facilitate the selection of immunotherapies for paediatric-type diffuse high-grade glioma

Immune cells have the potential to selectively eradicate high-risk brain tumours such as paediatric-type diffuse high-grade glioma (PDHGG). We aim to characterize the tumour immune microenvironment (TIME) of intra-cranial syngeneic mouse models of diffuse hemispheric glioma, H3G34 (DHG-H3G34) and diffuse midline glioma, H3K27 (DMG-H3K27). We also demonstrate how an oncolytic reovirus (Reolysin) can “heat-up” the TIME of our syngeneic models. Orthotopic immunocompetent mouse models of DHG-H3G34 (C57BL/6, NRASG12V + shp53 + shATRX +/- H3.3G34R) and DMG-H3K27 (Nestin-Tv-a/p53fl/fl, RCAS-ACVR1R206H + RCAS-H3.1K27M) were profiled using single-cell RNA-sequencing (scRNA-seq) (10x genomics), a 22-colour custom flow cytometry immune panel and spatial transcriptomics. Differential marker expression was validated with immunohistochemistry and immunofluorescence in tissue sections. Syngeneic mouse tumours treated systemically with Reolysin were also profiled to evaluate the effects of the oncolytic virus on the TIME. Cell type predictions in scRNA-seq using singleR, ssGSEA and expression of individual marker genes suggested that the predominant immune cell types within hemispheric tumours were monocytes (11-21%) and macrophages (10-19%) with much smaller proportions of CD4+ and CD8+ T-cells (4-10%). By contrast, much smaller proportions of monocytes (2%) and macrophages (3%) were observed in the H3.1K27M pontine model. Flow cytometry, immunohistochemistry and immunofluorescence validated scRNA-seq immune profiles and characterised signalling of the PD-1/PD-L1 checkpoint pathway. Spatial transcriptomics allowed immune cell populations to be positioned within tumour sections and showed significant co-localization of CD4+ and CD8+ lymphocytes at tumour margins. Treatment of syngeneic mouse tumours with Reolysin resulted in reduced tumour volumes and altered the TIME, in particular increasing cytotoxic T-cell tumour infiltration. Our results highlight immunological heterogeneity within molecular subgroups of PDHGG and demonstrate ability of a systemically delivered oncolytic virus, Reolysin, to “heat-up” the TIME, contributing to a more immune actionable profile. Future work will help to identify optimal combinations for the next generation of immunotherapies in PDHGG.

The ART of tumor immune escape

We recently identified the adenosine-5′-diphosphate (ADP)–ribosyltransferase-1 (ART1) as a novel immune checkpoint expressed by cancer cells. ART1 utilizes free nicotinamide adenine dinucleotide (NAD⁺) in the tumor microenvironment (TME) to mono-ADP-ribosylate (MARylate) the P2X7 receptor (P2X7R) on CD8 T cells, resulting in NAD-induced cell death (NICD) and tumor immune resistance. This process is blocked by therapeutic antibody targeting of ART1.

Hallmarks of Resistance to Immune-Checkpoint Inhibitors

Immune-checkpoint inhibitors (ICI), although revolutionary in improving long-term survival outcomes, are mostly effective in patients with immune-responsive tumors. Most patients with cancer either do not respond to ICIs at all or experience disease progression after an initial period of response. Treatment resistance to ICIs remains a major challenge and defines the biggest unmet medical need in oncology worldwide. In a collaborative workshop, thought leaders from academic, biopharma, and nonprofit sectors convened to outline a resistance framework to support and guide future immune-resistance research. Here, we explore the initial part of our effort by collating seminal discoveries through the lens of known biological processes. We highlight eight biological processes and refer to them as immune resistance nodes. We examine the seminal discoveries that define each immune resistance node and pose critical questions, which, if answered, would greatly expand our notion of immune resistance. Ultimately, the expansion and application of this work calls for the integration of multiomic high-dimensional analyses from patient-level data to produce a map of resistance phenotypes that can be utilized to guide effective drug development and improved patient outcomes.

Expression of the mono-ADP-ribosyltransferase ART1 by tumor cells mediates immune resistance in non-small cell lung cancer

Most patients with non-small cell lung cancer (NSCLC) do not achieve durable clinical responses from immune checkpoint inhibitors, suggesting the existence of additional resistance mechanisms. Nicotinamide adenine dinucleotide (NAD)-induced cell death (NICD) of P2X7 receptor (P2X7R)-expressing T cells regulates immune homeostasis in inflamed tissues. This process is mediated by mono-adenosine 5'-diphosphate (ADP)-ribosyltransferases (ARTs). We found an association between membranous expression of ART1 on tumor cells and reduced CD8 T cell infiltration. Specifically, we observed a reduction in the P2X7R⁺ CD8 T cell subset in human lung adenocarcinomas. In vitro, P2X7R⁺ CD8 T cells were susceptible to ART1-mediated ADP-ribosylation and NICD, which was exacerbated upon blockade of the NAD⁺-degrading ADP-ribosyl cyclase CD38. Last, in murine NSCLC and melanoma models, we demonstrate that genetic and antibody-mediated ART1 inhibition slowed tumor growth in a CD8 T cell-dependent manner. This was associated with increased infiltration of activated P2X7R⁺CD8 T cells into tumors. In conclusion, we describe ART1-mediated NICD as a mechanism of immune resistance in NSCLC and provide preclinical evidence that antibody-mediated targeting of ART1 can improve tumor control, supporting pursuit of this approach in clinical studies.

560 Immunotherapeutic and antimetastatic activity of LTX-315 in preclinical models of ICI-resistant breast cancer

Background

Oncolytic peptides are attractive tools for the development of novel anticancer regimens [1]. LTX-315 is a synthetic peptide with a marked capacity to elicit tumor-targeting immunity in preclinical cancer models [2]. Indeed, LTX-315 has been shown to elicit immunogenic cell death (ICD) in malignant cells [3, 4] and to deplete immunosuppressive cells such as CD4+CD25+FOXP3+ TREG cells and myeloid-derived suppressor cells (MDSCs) from the tumor microenvironment (TME) [5]. Accordingly, LTX-315 synergized with immunogenic chemotherapeutics or immune checkpoint inhibitors (ICIs) in preclinical tumor models [5, 6]. Moreover, recent findings from a Phase I clinical trial in patients with advanced solid tumors (NCT01986426) indicate that intratumoral LTX-315 is safe, clinically active, and elicits alterations in the TME that support the initiation of anticancer immunity [7, 8]. However, the dependency of LTX-315 therapeutic effects on the immune system in preclinical models of breast cancer has not been mechanistically investigated.

Methods

We harnessed three distinct mouse models of ICI-resistant breast cancer, namely hormone receptor (HR)-positive TS/A established and triple-negative breast cancer (TNBC) 4T1 cells established in immunocompetent syngeneic BALB/c mice, as well as medroxyprogesterone acetate (MPA, M)-initiated, 7,12-dimethylbenz[a]anthracene (DMBA, D)-driven mammary carcinomas evolving in C57BL/6 mice to assess the immunotherapeutic effects of LTX-315 optionally combined with radiation therapy (RT), based on the primary tumor growth, metastatic dissemination and overall survival (depending on model). Multilesion models, rechallenge assays, antibody-mediated depletion experiments as well as experiments in Rag1-/- mice were employed to elucidate the mechanistic involvement of the immune system.

Results

In the multilesion TS/A models, intratumoral LTX-315 to one lesion combined with hypofractionated RT to another lesion resulted in superior systemic disease control as manifested by eradication of a 3rd untreated lesion in up to 50% of mice, which were protected from a subsequent rechallenge with living TS/A cells. In the single lesion 4T1 model, LTX-315 mediated enable robust local and metastatic disease control, which could be enhanced (only locally) with RT and dependent on natural killer (NK) cells, but less so on T lymphocytes (as determined with anti-asialo GM1 antibodies and Rag1-/- hosts). In the M/D-driven model, LTX-315 considerably controlled the growth of primary tumors and delayed relapse, an effect that depended on NK cells (as demonstrated with anti-NK1.1 antibodies).

Conclusions

LTX-315, alone and combined with RT, mediates robust immunotherapeutic effects in multiple models of ICI-resistant breast cancer. Intriguingly, NK cells appear to be required for such effects, potentially linked to the emergence of immunological memory.

Acknowledgements

We are indebted to Dr. Fred Miller (Karmanos Cancer Center, Detroit, MI) for the kind gift of 4T1 cells, as well as to Dr. Karsten A. Pilones (Weill Cornell Medicine, New York, NY) and Maria E. Rodriguez-Ruiz (University of Navarra, Pamplona, Spain) for help with clonogenic assays. This work has been sponsored by a research grant by Lytix Biopharma (Oslo, Norway) to S.D. and L.G.

References

Kepp, O. et al. (2020) Oncolysis without viruses - inducing systemic anticancer immune responses with local therapies. Nat Rev Clin Oncol 17 (1), 49–64.

Vitale, I. et al. (2021) Targeting Cancer Heterogeneity with Immune Responses Driven by Oncolytic Peptides. Trends Cancer 7 (6), 557–572.

Eike, L.M. et al. (2015) The oncolytic peptide LTX-315 induces cell death and DAMP release by mitochondria distortion in human melanoma cells. Oncotarget 6 (33), 34910–23.

Zhou, H. et al. (2016) The oncolytic peptide LTX-315 triggers immunogenic cell death. Cell Death Dis 7 (3), e2134.

Yamazaki, T. et al. (2016) The oncolytic peptide LTX-315 overcomes resistance of cancers to immunotherapy with CTLA4 checkpoint blockade. Cell Death Differ 23 (6), 1004–15.

Camilio, K.A. et al. (2019) Combining the oncolytic peptide LTX-315 with doxorubicin demonstrates therapeutic potential in a triple-negative breast cancer model. Breast Cancer Res 21 (1), 9.

Jebsen, N.L. et al. (2019) Enhanced T-lymphocyte infiltration in a desmoid tumor of the thoracic wall in a young woman treated with intratumoral injections of the oncolytic peptide LTX-315: a case report. J Med Case Rep 13 (1), 177.

Spicer, J. et al. (2021) Safety, Antitumor Activity, and T-cell Responses in a Dose-Ranging Phase I Trial of the Oncolytic Peptide LTX-315 in Patients with Solid Tumors. Clin Cancer Res 27 (10), 2755–2763.

Ethics Approval

This study was approved by Weill Cornell Medical College’s Ethics Board; approval number 2015-0028, 2018-0002.

Kickstarting Immunity in Cold Tumours: Localised Tumour Therapy Combinations With Immune Checkpoint Blockade

Cancer patients with low or absent pre-existing anti-tumour immunity ("cold" tumours) respond poorly to treatment with immune checkpoint inhibitors (ICPI). In order to render these patients susceptible to ICPI, initiation of de novo tumour-targeted immune responses is required. This involves triggering of inflammatory signalling, innate immune activation including recruitment and stimulation of dendritic cells (DCs), and ultimately priming of tumour-specific T cells. The ability of tumour localised therapies to trigger these pathways and act as in situ tumour vaccines is being increasingly explored, with the aspiration of developing combination strategies with ICPI that could generate long-lasting responses. In this effort, it is crucial to consider how therapy-induced changes in the tumour microenvironment (TME) act both as immune stimulants but also, in some cases, exacerbate immune resistance mechanisms. Increasingly refined immune monitoring in pre-clinical studies and analysis of on-treatment biopsies from clinical trials have provided insight into therapy-induced biomarkers of response, as well as actionable targets for optimal synergy between localised therapies and ICB. Here, we review studies on the immunomodulatory effects of novel and experimental localised therapies, as well as the re-evaluation of established therapies, such as radiotherapy, as immune adjuvants with a focus on ICPI combinations.

LTX-315-enabled, radiotherapy-boosted immunotherapeutic control of breast cancer by NK cells

LTX-315 is a nonameric oncolytic peptide in early clinical development for the treatment of solid malignancies. Preclinical and clinical evidence indicates that the anticancer properties of LTX-315 originate not only from its ability to selectively kill cancer cells, but also from its capacity to promote tumor-targeting immune responses. Here, we investigated the therapeutic activity and immunological correlates of intratumoral LTX-315 administration in three syngeneic mouse models of breast carcinoma, with a focus on the identification of possible combinatorial partners. We found that breast cancer control by LTX-315 is accompanied by a reconfiguration of the immunological tumor microenvironment that supports the activation of anticancer immunity and can be boosted by radiation therapy. Mechanistically, depletion of natural killer (NK) cells compromised the capacity of LTX-315 to limit local and systemic disease progression in a mouse model of triple-negative breast cancer, and to extend the survival of mice bearing hormone-accelerated, carcinogen-driven endogenous mammary carcinomas. Altogether, our data suggest that LTX-315 controls breast cancer progression by engaging NK cell-dependent immunity.

Targeting Cancer Heterogeneity with Immune Responses Driven by Oncolytic Peptides

Accumulating preclinical and clinical evidence indicates that high degrees of heterogeneity among malignant cells constitute a considerable obstacle to the success of cancer therapy. This calls for the development of approaches that operate - or enable established treatments to operate - despite such intratumoral heterogeneity (ITH). In this context, oncolytic peptides stand out as promising therapeutic tools based on their ability to drive immunogenic cell death associated with robust anticancer immune responses independently of ITH. We review the main molecular and immunological pathways engaged by oncolytic peptides, and discuss potential approaches to combine these agents with modern immunotherapeutics in support of superior tumor-targeting immunity and efficacy in patients with cancer.

Abstract 2158: ART1 tumor expression mediates immune resistance in non-small cell lung cancer by elimination of P2 × 7R+ CD8 tissue resident memory T cells and conventional type I dendritic cells

Extracellular NAD+ (eNAD) is released from stressed and dying cells where it acts as a proinflammatory mediator. However, in the presence of mono-ADP-ribosyltransferases (ARTs) eNAD serves as a substrate for ADP-ribosylation of the P2 × 7 receptor (P2RX7), resulting in NAD-induced cell death (NICD). P2RX7 is expressed on several immune cells including CD103+ conventional type I dendritic cells (cDC1s) which are essential for initiation of tumor-specific immune responses as well as on tissue resident memory T cells (TRMs), of which high tumor infiltration has been associated with improved survival in non-small cell lung cancer (NSCLC) [1]. NICD of P2 × 7R+ TRMs was recently identified as a regulator of TRM tissue homeostasis [2]. CD38 is expressed on activated immune cells and can reduce eNAD levels by converting eNAD into ADPR. We tested the hypothesis that ART1 expression in NSCLC constitutes a mechanism of immune resistance by mediating NICD of P2 × 7R+ TRMs and P2 × 7R+ cDC1s.

ART1 expression in human NSCLC samples was determined by immunohistochemistry scoring of NSCLC tumors using a tissue microarray (TMA) (n=493). In addition, matched tumor and adjacent normal lung tissue samples were analyzed for ART1 expression by qPCR (n=40) and for infiltration of TRM and cDC1s by flow cytometry. A mouse KP1 lung tumor cell line with high ART1 expression was established from KRASG12D/P53−/− mice and transduced with a doxycycline-inducible shRNA targeting ART1 (ART1KD). KP1 cells and their derivatives were intravenously injected into syngeneic C57BL/6 mice to generate orthotopic lung tumors. Lung tumor nodules were enumerated two weeks after tumor inoculation using H&E-stained FFPE lung sections and lung-derived cell suspensions were analyzed by flow cytometry for infiltration of T cell and DC subsets.

Increased expression of ART1 in tumor compared to normal lung was observed in 55% of NSCLC samples by TMA analysis, and confirmed by qPCR. The frequency of P2RX7+ CD8 TRMs (p&lt;0.05) and P2 × 7R+ cDC1s (p&lt;0.01) were reduced in ART1+ tumors compared to matched normal lung tissue. In line with the hypothesis that CD38 protects P2 × 7R+ cells from ART1-mediated NICD, P2 × 7R+ CD8 TRMs and P2 × 7R+ cDC1s present within ART1+ tumors had elevated expression of CD38. In mice, knockdown of ART1 in KP1 tumors resulted in significantly delayed growth in immunocompetent mice (p&lt;0.001) but not in nude or CD8-depeleted mice. In an orthotopic lung model, ART1KD resulted in a 75% decrease in lung metastatic nodules (p&lt;0.01) and was associated with increased infiltration of CD8 T cells (P&lt;0.0001) and cDC1s (p&lt;0.01). In vitro experiments confirmed that CD38- P2RX7+ CD8 T cells were susceptible to ADP-ribosylation and NICD when co-cultured with ART1high lung tumor cells, while P2 × 7R+ CD8 T cells that co-expressed CD38 were resistant to NICD.

In conclusion, we show that ART1 is overexpressed in NSCLC and identify ART1-mediated NICD of P2 × 7R+ TRMs and cDC1s as a possible novel immune escape mechanism in NSCLC.

Furthermore, we describe a novel role of CD38 expression on immune cells in its protection against NICD.

1. Nizard, M., et al., Induction of resident memory T cells enhances the efficacy of cancer vaccine. Nat Commun, 2017. 8: p. 15221.

2. Stark, R., et al., T RM maintenance is regulated by tissue damage via P2RX7. Sci Immunol, 2018. 3(30).

Citation Format: Erik Wennerberg, Clarey Hung, Amanda Valeta, Timothy McGraw, Sandra Demaria, Brendon Stiles. ART1 tumor expression mediates immune resistance in non-small cell lung cancer by elimination of P2 × 7R+ CD8 tissue resident memory T cells and conventional type I dendritic cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2158.

CD73 Blockade Promotes Dendritic Cell Infiltration of Irradiated Tumors and Tumor Rejection

The ability of focal radiotherapy to promote priming of tumor-specific CD8⁺ T cells and increase responses to immunotherapy is dependent on infiltration of the tumor by Batf3-dependent conventional dendritic cell type 1 (cDC1) cells. Such infiltration is driven by radiotherapy-induced IFN type I (IFN-I). Other signals may also modulate cDC1 infiltration of irradiated tumors. Here we found increased expression of adenosine-generating enzymes CD38 and CD73 in irradiated mouse and human breast cancer cells and increased adenosine in mouse tumors following radiotherapy. CD73 blockade alone had no effect. CD73 blockade with radiotherapy restored radiotherapy-induced cDC1 infiltration of tumors in settings where radiotherapy induction of IFN-I was suboptimal. In the absence of radiotherapy-induced IFN-I, blockade of CD73 was required for rejection of the irradiated tumor and for systemic tumor control (abscopal effect) in the context of cytotoxic T-lymphocyte-associated protein 4 blockade. These results suggest that CD73 may be a radiation-induced checkpoint, and that CD73 blockade in combination with radiotherapy and immune checkpoint blockade might improve patient response to therapy.

Exercise reduces immune suppression and breast cancer progression in a preclinical model

Exercise is associated with favorable changes in circulating immune cells and improved survival in early-stage breast cancer patients, but the mechansims remain to be fully elucidated. Preclinical studies indicate that physical activity started before tumor injection reduces tumor incidence and progression. Here we tested whether exercise has anti-tumor effects in mice with established 4T1 mammary carcinoma, a mouse model of triple negative breast cancer. Exercise slowed tumor progression and reduced the tumor-induced accumulation of myeloid-derived suppressor cells (MDSCs). The reduction in MDSCs was accompanied by a relative increase in natural killer and CD8 T cell activation, suggesting that exercise restores a favorable immune environment. Consistently, exercise improved responses to a combination of programmed cell death protein 1 (PD-1) blockade and focal radiotherapy. These data support further investigations of exercise in breast cancer patients treated with combinations of immunotherapy and cytotoxic agents to improve cancer outcomes.

Born to Kill: NK Cells Go to War against Cancer

Preclinical and clinical data emerging over the past year demonstrate that cancer cells suppress the cytotoxic functions of natural killer cells by a variety of mechanisms. These findings reveal a new arsenal of actionable therapeutic targets to drive clinically relevant immune responses against cancer.

Radiotherapy induces responses of lung cancer to CTLA-4 blockade

Focal radiation therapy enhances systemic responses to anti-CTLA-4 antibodies in preclinical studies and in some patients with melanoma1-3, but its efficacy in inducing systemic responses (abscopal responses) against tumors unresponsive to CTLA-4 blockade remained uncertain. Radiation therapy promotes the activation of anti-tumor T cells, an effect dependent on type I interferon induction in the irradiated tumor4-6. The latter is essential for achieving abscopal responses in murine cancers6. The mechanisms underlying abscopal responses in patients treated with radiation therapy and CTLA-4 blockade remain unclear. Here we report that radiation therapy and CTLA-4 blockade induced systemic anti-tumor T cells in chemo-refractory metastatic non-small-cell lung cancer (NSCLC), where anti-CTLA-4 antibodies had failed to demonstrate significant efficacy alone or in combination with chemotherapy7,8. Objective responses were observed in 18% of enrolled patients, and 31% had disease control. Increased serum interferon-β after radiation and early dynamic changes of blood T cell clones were the strongest response predictors, confirming preclinical mechanistic data. Functional analysis in one responding patient showed the rapid in vivo expansion of CD8 T cells recognizing a neoantigen encoded in a gene upregulated by radiation, supporting the hypothesis that one explanation for the abscopal response is radiation-induced exposure of immunogenic mutations to the immune system.

Abstract B05: Adenosine generation limits the ability of radiation therapy to induce antitumor immunity by abrogating recruitment and activation of CD103+ DCs

Localized radiation therapy (RT) can act as a powerful adjuvant to immunotherapeutic strategies by triggering anti-tumor immune responses to poorly immunogenic tumors. Radiation of tumor cells induces a dose-dependent release of ATP, a molecule that when released in the tumor microenvironment (TME) triggers recruitment and activation of dendritic cells (DCs), including CD103+ DCs recently identified as the key DC subset responsible for cross-presentation of tumor-derived antigens to CD8+ T cells. However, rapid hydrolysis of extracellular ATP by ecto-enzymes CD39 and CD73 results in a local accumulation of immunosuppressive adenosine that inhibits DC activation and CD8+ T cell effector functions and promotes regulatory T cells (Tregs). By blocking CD73 in conjunction with local tumor RT, we tested the hypothesis that adenosine generation limits the ability of RT to trigger anti-tumor immunity.

Wild type (WT) or BATF3-/- mice (CD103+ DC-deficient) were inoculated s.c. with TSA tumor cells (day 0) and assigned to treatment with: (1) control Ab; (2) anti-CD73 Ab (100 μg) (3) RT (20 Gy); (4) RT + anti-CD73 Ab. Antibodies were administered i.p. on day 11, 14, 17 and 20. RT was given locally as single 20 Gy dose on day 12. On day 18, tumors were analyzed by flow cytometry for DC and T cell infiltration. Mice were monitored for tumor progression. Bone marrow-derived DCs (BMDCs) isolated from WT mice (&gt;90% CD103+) were labeled with CFSE and intravenously injected in BATF3-/- recipient mice. Tumors were harvested after 48h and analyzed by flow cytometry for infiltration of CFSE+ DCs.

In irradiated but not mock-treated mice, anti-CD73 Ab resulted in increased infiltration of CD103+DCs (8.9±2.6% of DCs in RT+anti-CD73 v. 3.5±2.8% of DCs in RT, p&lt;0.05) expressing elevated levels of activation marker CD86 compared to mice treated with RT alone. This change was associated with improved CD8+T cell/Treg ratio (5±2.8 in RT+anti-CD73 v. 0.8±0.2 in RT). Importantly, CD73 blockade had no effect by itself but improved significantly radiation-induced tumor control (Tumor size at day 57 post inoculation: 385±525 mm3 in RT+anti-CD73 v. 1036±727 mm3 in RT). Consistent with the hypothesis that CD103+ DCs are essential for anti-tumor responses, the therapeutic effect of RT+CD73 blockade was abrogated in BATF3-/- mice. Moreover, CD73 blockade facilitated recruitment of adoptively transferred CD103+ BMDCs in irradiated tumors in BATF3-/- mice.

Our data support the hypothesis that adenosine generated following RT plays a key role in hindering development of anti-tumor immune responses and identify, as a mechanism of this effect, an abrogated infiltration and activation of CD103+ DCs. Blockade of adenosine generation by anti-CD73 treatment constitutes a promising strategy to enhance radiation-induced anti-tumor immunity.

Citation Format: Erik Wennerberg, Silvia Formenti, Sandra Demaria. Adenosine generation limits the ability of radiation therapy to induce antitumor immunity by abrogating recruitment and activation of CD103+ DCs [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B05.

Immune recognition of irradiated cancer cells

Ionizing irradiation has been extensively employed for the clinical management of solid tumors, with therapeutic or palliative intents, for decades. Until recently, radiation therapy (RT) was believed to mediate antineoplastic activity mostly (if not only) as a consequence of cancer cell-intrinsic effects. Indeed, the macromolecular damage imposed to malignant cells by RT initiates one or multiple signal transduction cascades that drive a permanent proliferative arrest (cellular senescence) or regulated cell death. Both these phenomena show a rather linear dose-response correlation. However, RT also mediates consistent immunological activity, not only as an "on-target effect" originating within irradiated cancer cells, but also as an "off-target effect" depending on the interaction between RT and stromal, endothelial, and immune components of the tumor microenvironment. Interestingly, the immunological activity of RT does not exhibit linear dose-response correlation. Here, we discuss the mechanisms whereby RT alters the capacity of the immune system to recognize and eliminate irradiated cancer cells, either as an "on-target" or as on "off-target" effect. In particular, we discuss the antagonism between the immunostimulatory and immunosuppressive effects of RT as we delineate combinatorial strategies to boost the former at the expenses of the latter.

Radiotherapy and CTLA-4 Blockade Shape the TCR Repertoire of Tumor-Infiltrating T Cells

Immune checkpoint inhibitors activate T cells to reject tumors. Unique tumor mutations are key T-cell targets, but a comprehensive understanding of the nature of a successful antitumor T-cell response is lacking. To investigate the T-cell receptor (TCR) repertoire associated with treatment success versus failure, we used a well-characterized mouse carcinoma that is rejected by CD8 T cells in mice treated with radiotherapy (RT) and anti-CTLA-4 in combination, but not as monotherapy, and comprehensively analyzed tumor-infiltrating lymphocytes (TILs) by high-throughput sequencing of the TCRΒ CDR3 region. The combined treatment increased TIL density and CD8/CD4 ratio. Assessment of the frequency of T-cell clones indicated that anti-CTLA-4 resulted in fewer clones and a more oligoclonal repertoire compared with untreated tumors. In contrast, RT increased the CD8/CD4 ratio and broadened the TCR repertoire, and when used in combination with anti-CTLA-4, these selected T-cell clones proliferated. Hierarchical clustering of CDR3 sequences showed a treatment-specific clustering of TCRs that were shared by different mice. Abundant clonotypes were commonly shared between animals and yet treatment-specific. Analysis of amino-acid sequence similarities revealed a significant increase in the number and richness of dominant CDR3 motifs in tumors treated with RT + anti-CTLA-4 compared with control. The repertoire of TCRs reactive with a single tumor antigen recognized by CD8⁺ T cells was heterogeneous but highly clonal, irrespective of treatment. Overall, data support a model whereby a diverse TCR repertoire is required to achieve tumor rejection and may underlie the synergy between RT and CTLA-4 blockade. Cancer Immunol Res; 6(2); 139-50. ©2017 AACR.

Genetic engineering of human NK cells to express CXCR2 improves migration to renal cell carcinoma

Background

Adoptive natural killer (NK) cell transfer is being increasingly used as cancer treatment. However, clinical responses have so far been limited to patients with hematological malignancies. A potential limiting factor in patients with solid tumors is defective homing of the infused NK cells to the tumor site. Chemokines regulate the migration of leukocytes expressing corresponding chemokine receptors. Various solid tumors, including renal cell carcinoma (RCC), readily secrete ligands for the chemokine receptor CXCR2. We hypothesize that infusion of NK cells expressing high levels of the CXCR2 chemokine receptor will result in increased influx of the transferred NK cells into tumors, and improved clinical outcome in patients with cancer.

Methods

Blood and tumor biopsies from 14 primary RCC patients were assessed by flow cytometry and chemokine analysis. Primary NK cells were transduced with human CXCR2 using a retroviral system. CXCR2 receptor functionality was determined by Calcium flux and NK cell migration was evaluated in transwell assays.

Results

We detected higher concentrations of CXCR2 ligands in tumors compared with plasma of RCC patients. In addition, CXCL5 levels correlated with the intratumoral infiltration of CXCR2-positive NK cells. However, tumor-infiltrating NK cells from RCC patients expressed lower CXCR2 compared with peripheral blood NK cells. Moreover, healthy donor NK cells rapidly lost their CXCR2 expression upon in vitro culture and expansion. Genetic modification of human primary NK cells to re-express CXCR2 improved their ability to specifically migrate along a chemokine gradient of recombinant CXCR2 ligands or RCC tumor supernatants compared with controls. The enhanced trafficking resulted in increased killing of target cells. In addition, while their functionality remained unchanged compared with control NK cells, CXCR2-transduced NK cells obtained increased adhesion properties and formed more conjugates with target cells.

Conclusions

To increase the success of NK cell-based therapies of solid tumors, it is of great importance to promote their homing to the tumor site. In this study, we show that stable engineering of human primary NK cells to express a chemokine receptor thereby enhancing their migration is a promising strategy to improve anti-tumor responses following adoptive transfer of NK cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-017-0275-9) contains supplementary material, which is available to authorized users.

Adenosine generation limits radiation-induced tumor immunogenicity by abrogating recruitment and activation of CD103+ DCs

Radiation therapy (RT) induces release of ATP in the tumor micro environment (TME) triggering recruitment and activation of dendritic cells (DCs), including CD103+ DCs, identified as the key DC subsetresponsible for cross-presentation of tumor antigens to CD8+ T cells. However, CD39 and CD73-expressing cells in the TME hydrolyze ATP into adenosine that potently inhibits DCs and CD8+ T cells. Here, we tested the hypothesis that adenosine generation limits the ability of RT totrigger anti-tumor immunity.

Wild type (WT) or BATF3−/− mice (CD103+DC-deficient) were inoculated s.c. with TSA tumor cells (day 0) and assigned to treatment with: (1) control Ab; (2) anti-CD73 Ab (100 μg) (3) RT (20 Gy); (4) RT + anti-CD73 Ab. Antibodies were administered i.p. on day 11, 14, 17 and 20. RT was given locally as single 20 Gy dose on day 12. On day 18, tumors were analyzed by flow cytometry for DC and T cell infiltration. Mice were monitored for tumor progression. DCs generated in vitro by culture of bone marrow from WT mice with Flt3L (&gt;90% CD103+) were labeled with CFSE and intravenously injected in BATF3−/− recipient mice. Tumors were harvested after 48h and analyzed by flow cytometry for infiltration of CFSE+ DCs.

In tumors of RT- but not sham-treated mice, anti-CD73 mAb increased infiltration of CD103+DCs and enhanced CD8+T cell/Treg ratio. Importantly, CD73 blockade had no anti-tumor effect by itself but significantly improved RT-induced tumor control. The therapeutic effect of RT + CD73 blockade was abrogated in BATF3−/− mice. Moreover, CD73 blockade increased recruitment of adoptively transferred CD103+DCs to irradiated tumors in BATF3−/− mice. Overall, data suggest that adenosine is a critical regulator of RT-induced immunogenicity.

Barriers to Radiation-Induced In Situ Tumor Vaccination

The immunostimulatory properties of radiation therapy (RT) have recently generated widespread interest due to preclinical and clinical evidence that tumor-localized RT can sometimes induce antitumor immune responses mediating regression of non-irradiated metastases (abscopal effect). The ability of RT to activate antitumor T cells explains the synergy of RT with immune checkpoint inhibitors, which has been well documented in mouse tumor models and is supported by observations of more frequent abscopal responses in patients refractory to immunotherapy who receive RT during immunotherapy. However, abscopal responses following RT remain relatively rare in the clinic, and antitumor immune responses are not effectively induced by RT against poorly immunogenic mouse tumors. This suggests that in order to improve the pro-immunogenic effects of RT, it is necessary to identify and overcome the barriers that pre-exist and/or are induced by RT in the tumor microenvironment. On the one hand, RT induces an immunogenic death of cancer cells associated with release of powerful danger signals that are essential to recruit and activate dendritic cells (DCs) and initiate antitumor immune responses. On the other hand, RT can promote the generation of immunosuppressive mediators that hinder DCs activation and impair the function of effector T cells. In this review, we discuss current evidence that several inhibitory pathways are induced and modulated in irradiated tumors. In particular, we will focus on factors that regulate and limit radiation-induced immunogenicity and emphasize current research on actionable targets that could increase the effectiveness of radiation-induced in situ tumor vaccination.

Melanoma and immunotherapy bridge 2015 : Naples, Italy. 1-5 December 2015

MELANOMA BRIDGE 2015

KEYNOTE SPEAKER PRESENTATIONS

Molecular and immuno-advances

K1 Immunologic and metabolic consequences of PI3K/AKT/mTOR activation in melanoma

Vashisht G. Y. Nanda, Weiyi Peng, Patrick Hwu, Michael A. Davies

K2 Non-mutational adaptive changes in melanoma cells exposed to BRAF and MEK inhibitors help the establishment of drug resistance

Gennaro Ciliberto, Luigi Fattore, Debora Malpicci, Luigi Aurisicchio, Paolo Antonio Ascierto, Carlo M. Croce, Rita Mancini

K3 Tumor-intrinsic beta-catenin signaling mediates tumor-immune avoidance

Stefani Spranger, Thomas F. Gajewski

K4 Intracellular tumor antigens as a source of targets of antibody-based immunotherapy of melanoma

Yangyang Wang, Soldano Ferrone

Combination therapies

K5 Harnessing radiotherapy to improve responses to immunotherapy in cancer

Claire Vanpouille-Box, Erik Wennerberg, Karsten A. Pilones, Silvia C. Formenti, Sandra Demaria

K6 Creating a T cell-inflamed tumor microenvironment overcomes resistance to checkpoint blockade

Haidong Tang, Yang Wang, Yang-Xin Fu

K7 Biomarkers for treatment decisions?

Reinhard Dummer

K8 Combining oncolytic therapies in the era of checkpoint inhibitors

Igor Puzanov

K9 Immune checkpoint blockade for melanoma: should we combine or sequence ipilimumab and PD-1 antibody therapy?

Michael A. Postow

News in immunotherapy

K10 An update on adjuvant and neoadjuvant therapy for melanom

Ahmad Tarhini

K11 Targeting multiple inhibitory receptors in melanoma

Joe-Marc Chauvin, Ornella Pagliano, Julien Fourcade, Zhaojun Sun, Hong Wang, Cindy Sanders, John M. Kirkwood, Tseng-hui Timothy Chen, Mark Maurer, Alan J. Korman, Hassane M. Zarour

K12 Improving adoptive immune therapy using genetically engineered T cells

David F. Stroncek

Tumor microenvironment and biomarkers

K13 Myeloid cells and tumor exosomes: a crosstalk for assessing immunosuppression?

Veronica Huber, Licia Rivoltini

K14 Update on the SITC biomarker taskforce: progress and challenges

Magdalena Thurin

World-wide immunoscore task force: an update

K15 The immunoscore in colorectal cancer highlights the importance of digital scoring systems in surgical pathology

Tilman Rau, Alessandro Lugli

K16 The immunoscore: toward an integrated immunomonitoring from the diagnosis to the follow up of cancer’s patients

Franck Pagès

Economic sustainability of melanoma treatments: regulatory, health technology assessment and market access issues

K17 Nivolumab, the regulatory experience in immunotherapy

Jorge Camarero, Arantxa Sancho

K18 Evidence to optimize access for immunotherapies

Claudio Jommi

ORAL PRESENTATIONS

Molecular and immuno-advances

O1 Ipilimumab treatment results in CD4 T cell activation that is concomitant with a reduction in Tregs and MDSCs

Yago Pico de Coaña, Maria Wolodarski, Yuya Yoshimoto, Giusy Gentilcore, Isabel Poschke, Giuseppe V. Masucci, Johan Hansson, Rolf Kiessling

O2 Evaluation of prognostic and therapeutic potential of COX-2 and PD-L1 in primary and metastatic melanoma

Giosuè Scognamiglio, Francesco Sabbatino, Federica Zito Marino, Anna Maria Anniciello, Monica Cantile, Margherita Cerrone, Stefania Scala, Crescenzo D’alterio, Angela Ianaro, Giuseppe Cirino, Paolo Antonio Ascierto, Giuseppina Liguori, Gerardo Botti

O3 Vemurafenib in patients with BRAFV600 mutation–positive metastatic melanoma: final overall survival results of the BRIM-3 study

Paul B. Chapman, Caroline Robert, James Larkin, John B. Haanen, Antoni Ribas, David Hogg, Omid Hamid, Paolo Antonio Ascierto, Alessandro Testori, Paul Lorigan, Reinhard Dummer, Jeffrey A. Sosman, Keith T. Flaherty, Huibin Yue, Shelley Coleman, Ivor Caro, Axel Hauschild, Grant A. McArthur

O4 Updated survival, response and safety data in a phase 1 dose-finding study (CA209-004) of concurrent nivolumab (NIVO) and ipilimumab (IPI) in advanced melanoma

Mario Sznol, Margaret K. Callahan, Harriet Kluger, Michael A. Postow, RuthAnn Gordan, Neil H. Segal, Naiyer A. Rizvi, Alexander Lesokhin, Michael B. Atkins, John M. Kirkwood, Matthew M. Burke, Amanda Ralabate, Angel Rivera, Stephanie A. Kronenberg, Blessing Agunwamba, Mary Ruisi, Christine Horak, Joel Jiang, Jedd Wolchok

Combination therapies

O5 Efficacy and correlative biomarker analysis of the coBRIM study comparing cobimetinib (COBI) + vemurafenib (VEM) vs placebo (PBO) + VEM in advanced BRAF-mutated melanoma patients (pts)

Paolo A. Ascierto, Grant A. McArthur, James Larkin, Gabriella Liszkay, Michele Maio, Mario Mandalà, Lev Demidov, Daniil Stoyakovskiy, Luc Thomas, Luis de la Cruz-Merino, Victoria Atkinson, Caroline Dutriaux, Claus Garbe, Matthew Wongchenko, Ilsung Chang, Daniel O. Koralek, Isabelle Rooney, Yibing Yan, Antoni Ribas, Brigitte Dréno

O6 Preliminary clinical safety, tolerability and activity results from a Phase Ib study of atezolizumab (anti-PDL1) combined with vemurafenib in BRAFV600-mutant metastatic melanoma

Ryan Sullivan, Omid Hamid, Manish Patel, Stephen Hodi, Rodabe Amaria, Peter Boasberg, Jeffrey Wallin, Xian He, Edward Cha, Nicole Richie, Marcus Ballinger, Patrick Hwu

O7 Preliminary safety and efficacy data from a phase 1/2 study of epacadostat (INCB024360) in combination with pembrolizumab in patients with advanced/metastatic melanoma

Thomas F. Gajewski, Omid Hamid, David C. Smith, Todd M. Bauer, Jeffrey S. Wasser, Jason J. Luke, Ani S. Balmanoukian, David R. Kaufman, Yufan Zhao, Janet Maleski, Lance Leopold, Tara C. Gangadhar

O8 Primary analysis of MASTERKEY-265 phase 1b study of talimogene laherparepvec (T-VEC) and pembrolizumab (pembro) for unresectable stage IIIB-IV melanoma

Reinhard Dummer, Georgina V. Long, Antoni Ribas, Igor Puzanov, Olivier Michielin, Ari VanderWalde, Robert H.I. Andtbacka, Jonathan Cebon, Eugenio Fernandez, Josep Malvehy, Anthony J. Olszanski, Thomas F. Gajewski, John M. Kirkwood, Christine Gause, Lisa Chen, David R. Kaufman, Jeffrey Chou, F. Stephen Hodi

News in immunotherapy

O9 Two-year survival and safety update in patients (pts) with treatment-naïve advanced melanoma (MEL) receiving nivolumab (NIVO) or dacarbazine (DTIC) in CheckMate 066

Victoria Atkinson, Paolo A. Ascierto, Georgina V. Long, Benjamin Brady, Caroline Dutriaux, Michele Maio, Laurent Mortier, Jessica C. Hassel, Piotr Rutkowski, Catriona McNeil, Ewa Kalinka-Warzocha, Celeste Lebbé, Lars Ny, Matias Chacon, Paola Queirolo, Carmen Loquai, Parneet Cheema, Alfonso Berrocal, Karmele Mujika Eizmendi, Luis De La Cruz-Merino, Gil Bar-Sela, Christine Horak, Joel Jiang, Helene Hardy, Caroline Robert

O10 Efficacy and safety of nivolumab (NIVO) in patients (pts) with advanced melanoma (MEL) who were treated beyond progression in CheckMate 066/067

Georgina V. Long, Jeffrey S. Weber, James Larkin, Victoria Atkinson, Jean-Jacques Grob, Reinhard Dummer, Caroline Robert, Ivan Marquez-Rodas, Catriona McNeil, Henrik Schmidt, Karen Briscoe, Jean-François Baurain, F. Stephen Hodi, Jedd D. Wolchok

Tumor microenvironment and biomarkers

O11 New biomarkers for response/resistance to BRAF inhibitor therapy in metastatic melanoma

Rosamaria Pinto, Simona De Summa, Vito Michele Garrisi, Sabino Strippoli, Amalia Azzariti, Gabriella Guida, Michele Guida, Stefania Tommasi

O12 Chemokine receptor patterns in lymphocytes mirror metastatic spreading in melanoma and response to ipilimumab

Nicolas Jacquelot, David Enot, Caroline Flament, Jonathan M. Pitt, Nadège Vimond, Carolin Blattner, Takahiro Yamazaki, Maria-Paula Roberti, Marie Vetizou, Romain Daillere, Vichnou Poirier-Colame, Michaëla Semeraro, Anne Caignard, Craig L Slingluff Jr, Federica Sallusto, Sylvie Rusakiewicz, Benjamin Weide, Aurélien Marabelle, Holbrook Kohrt, Stéphane Dalle, Andréa Cavalcanti, Guido Kroemer, Anna Maria Di Giacomo, Michaele Maio, Phillip Wong, Jianda Yuan, Jedd Wolchok, Viktor Umansky, Alexander Eggermont, Laurence Zitvogel

O13 Serum levels of PD1- and CD28-positive exosomes before Ipilimumab correlate with therapeutic response in metastatic melanoma patients

Passarelli Anna, Tucci Marco, Stucci Stefania, Mannavola Francesco, Capone Mariaelena, Madonna Gabriele, Ascierto Paolo Antonio, Silvestris Franco

O14 Immunological prognostic factors in stage III melanomas

María Paula Roberti, Nicolas Jacquelot, David P Enot, Sylvie Rusakiewicz, Michaela Semeraro, Sarah Jégou, Camila Flores, Lieping Chen, Byoung S. Kwon, Ana Carrizossa Anderson, Caroline Robert, Christophe Borg, Benjamin Weide, François Aubin, Stéphane Dalle, Michele Maio, Jedd D. Wolchok, Holbrook Kohrt, Maha Ayyoub, Guido Kroemer, Aurélien Marabelle, Andréa Cavalcanti, Alexander Eggermont, Laurence Zitvogel

POSTER PRESENTATIONS

Molecular and immuno-advances

P1 Human melanoma cells resistant to B-RAF and MEK inhibition exhibit mesenchymal-like features

Anna Lisa De Presbiteris, Fabiola Gilda Cordaro, Rosa Camerlingo, Federica Fratangelo, Nicola Mozzillo, Giuseppe Pirozzi, Eduardo J. Patriarca, Paolo A. Ascierto, Emilia Caputo

P2 Anti-proliferative and pro-apoptotic effect of ABT888 on melanoma cell lines and its potential role in the treatment of melanoma resistant to B-RAF inhibitors

Federica Fratangelo, Rosa Camerlingo, Emilia Caputo, Maria Letizia Motti, Rosaria Falcone, Roberta Miceli, Mariaelena Capone, Gabriele Madonna, Domenico Mallardo, Maria Vincenza Carriero, Giuseppe Pirozzi and Paolo Antonio Ascierto

P3 Involvement of the L-cysteine/CSE/H2S pathway in human melanoma progression

Elisabetta Panza, Paola De Cicco, Chiara Armogida, Giuseppe Ercolano, Rosa Camerlingo, Giuseppe Pirozzi, Giosuè Scognamiglio, Gerardo Botti, Giuseppe Cirino, Angela Ianaro

P4 Cancer stem cell antigen revealing pattern of antibody variable region genes were defined by immunoglobulin repertoire analysis in patients with malignant melanoma

Beatrix Kotlan, Gabriella Liszkay, Miri Blank, Timea Balatoni, Judit Olasz, Emil Farkas, Andras Szollar, Akos Savolt, Maria Godeny, Orsolya Csuka, Szabolcs Horvath, Klara Eles, Yehuda Shoenfeld and Miklos Kasler

P5 Upregulation of Neuregulin-1 expression is a hallmark of adaptive response to BRAF/MEK inhibitors in melanoma

Debora Malpicci, Luigi Fattore, Susan Costantini, Francesca Capone, Paolo Antonio Ascierto, Rita Mancini, Gennaro Ciliberto

P6 HuR positively regulates migration of HTB63 melanoma cells

Farnaz Moradi, Pontus Berglund, Karin Leandersson, Rickard Linnskog, Tommy Andersson, Chandra Prakash Prasad

P7 Prolyl 4- (C-P4H) hydroxylases have opposing effects in malignant melanoma: implication in prognosis and therapy

Cristiana Lo Nigro, Laura Lattanzio, Hexiao Wang, Charlotte Proby, Nelofer Syed, Marcella Occelli, Carolina Cauchi, Marco Merlano, Catherine Harwood, Alastair Thompson, Tim Crook

P8 Urokinase receptor antagonists: novel agents for the treatment of melanoma

Maria Letizia Motti, Katia Bifulco, Vincenzo Ingangi, Michele Minopoli, Concetta Ragone, Federica Fratangelo, Antonello Pessi, Gennaro Ciliberto, Paolo Antonio Ascierto, Maria Vincenza Carriero

P9 Exosomes released by melanoma cell lines enhance chemotaxis of primary tumor cells

Francesco Mannavola, Stella D’Oronzo, Claudia Felici, Marco Tucci, Antonio Doronzo, Franco Silvestris

P10 New insights in mitochondrial metabolic reprogramming in melanoma

Anna Ferretta, Gabriella Guida, Stefania Guida, Imma Maida, Tiziana Cocco, Sabino Strippoli, Stefania Tommasi, Amalia Azzariti, Michele Guida

P11 Lenalidomide restrains the proliferation in melanoma cells through a negative regulation of their cell cycle

Stella D’Oronzo, Anna Passarelli, Claudia Felici, Marco Tucci, Davide Quaresmini, Franco Silvestris

Combination therapies

P12 Chemoimmunotherapy elicits polyfunctional anti-tumor CD8 + T cells depending on the activation of an AKT pathway sustained by ICOS

Ornella Franzese, Belinda Palermo, Cosmo Di Donna, Isabella Sperduti, MariaLaura Foddai, Helena Stabile, Angela Gismondi, Angela Santoni, Paola Nisticò

P13 Favourable toxicity profile of combined BRAF and MEK inhibitors in metastatic melanoma patients

Andrea P. Sponghini, Francesca Platini, Elena Marra, David Rondonotti, Oscar Alabiso, Maria T. Fierro, Paola Savoia, Florian Stratica, Pietro Quaglino

P14 Electrothermal bipolar vessel sealing system dissection reduces seroma output or time to drain removal following axillary and ilio-inguinal node dissection in melanoma patients: a pilot study

Di Monta Gianluca, Caracò Corrado, Di Marzo Massimiliano, Marone Ugo, Di Cecilia Maria Luisa, Mozzillo Nicola

News in immunotherapy

P15 Clinical and immunological response to ipilimumab in a metastatic melanoma patient with HIV infection

Francesco Sabbatino, Celeste Fusciello1, Antonio Marra, Rosario Guarrasi, Carlo Baldi, Rosa Russo, Di Giulio Giovanni, Vincenzo Faiola, Pio Zeppa, Stefano Pepe

P16 Immunotherapy and hypophysitis: a case report

Elisabetta Gambale, Consiglia Carella, Alessandra Di Paolo, Michele De Tursi

Tumor microenvironment and biomarkers

P17 New immuno- histochemical markers for the differential diagnosis of atypical melanocytic lesions with uncertain malignant potential

Laura Marra, Giosuè Scognamiglio, Monica Cantile, Margherita Cerrone, Fara De Murtas, Valeria Sorrentino, Anna Maria Anniciello, Gerardo Botti

P18 Utility of simultaneous measurement of three serum tumor markers in melanoma patients

Angela Sandru, Silviu Voinea, Eugenia Panaitescu, Madalina Bolovan, Adina Stanciu, Sabin Cinca

P19 The significance of various cut-off levels of melanoma inhibitory activity in evaluation of cutaneous melanoma patients

Angela Sandru, Silviu Voinea, Eugenia Panaitescu, Madalina Bolovan, Adina Stanciu, Sabin Cinca

P20 The long noncoding RNA HOTAIR is associated to metastatic progression of melanoma and it can be identified in the blood of patients with advanced disease

Chiara Botti, Giosuè Scognamiglio, Laura Marra, Gabriella Aquino, Rosaria Falcone, Annamaria Anniciello, Paolo Antonio Ascierto, Gerardo Botti, Monica Cantile

Other

P21 The effect of Sentinel Lymph Node Biopsy in melanoma mortality: timing of dissection

Cristina Fortes, Simona Mastroeni, Alessio Caggiati, Francesca Passarelli, Alba Zappalà, Maria Capuano, Riccardo Bono, Maurizio Nudo, Claudia Marino, Paola Michelozzi

P22 Epidemiological survey on related psychopathology in melanoma

Valeria De Biasio, Vincenzo C. Battarra

IMMUNOTHERAPY BRIDGE

KEYNOTE SPEAKER PRESENTATIONS

Immunotherapy beyond melanoma

K19 Predictor of response to radiation and immunotherapy

Silvia Formenti

K20 Response and resistance to PD-1 pathway blockade: clues from the tumor microenvironment

Maria Libera Ascierto, Tracee L. McMiller, Alan E. Berger, Ludmila Danilova, Robert A. Anders, George J. Netto, Haiying Xu, Theresa S. Pritchard, Jinshui Fan, Chris Cheadle, Leslie Cope, Charles G. Drake, Drew M. Pardoll, Janis M. Taube and Suzanne L. Topalian

K21 Combination immunotherapy with autologous stem cell transplantation, protein immunization, and PBMC reinfusion in myeloma patients

Sacha Gnjatic, Sarah Nataraj, Naoko Imai, Adeeb Rahman, Achim A. Jungbluth, Linda Pan, Ralph Venhaus, Andrew Park, Frédéric F. Lehmann, Nikoletta Lendvai, Adam D. Cohen, and Hearn J. Cho

K22 Anti-cancer immunity despite T cell “exhaustion”

Speiser Daniel

Immunotherapy in oncology (I-O): data from clinical trial

K23 The Checkpoint Inhibitors for the Treatment of Metastatic Non-small Cell Lung Cancer (NSCLC)

Vera Hirsh

Abstract 4033: Adenosine regulates radiation therapy-induced antitumor immunity

Radiation-induced immunogenic cell death (ICD) is a key mechanism whereby local radiation therapy (RT) can elicit anti-tumor immune responses and synergize with immune checkpoint inhibitors in enhancing tumor responses. ATP, which is an essential signal of ICD, activates tumor-resident dendritic cells (DCs) promoting their ability to cross-present tumor-derived antigens to T cells. Interestingly, while release of ATP by RT is dose-dependent (Golden et al., OncoImmunology 2014), a large RT dose of 20 Gy was not effective in inducing anti-tumor T cells and synergize with anti-CTLA-4 (Dewan et al., Clin Cancer Res 2009). Extracellular ATP is rapidly catabolized to adenosine (ADO) by ectonucleotidases CD39 and CD73, which are expressed on tumor cells and immune cells. ADO has immunosuppressive effects, inhibiting DC- and effector T cell-activation, while promoting regulatory T cells (Tregs). Here, we tested the hypothesis that conversion of ATP to ADO hinders generation of effective anti-tumor immunity by high dose RT.

Mice were inoculated s.c. with TSA breast cancer cells or MCA38 colon cancer cells on day 0 and assigned to treatment with: (1) control mAb; (2) anti-CD73 (TY/23); (3) RT (4) RT+TY/23. TY/23 (200 μg) was administered i.p. on day 11, 14, 17 and 20. RT was given locally as single 20 Gy dose on day 12. On day 18, some tumors were harvested for flow cytometry analysis of DC and T cells. Mice were monitored for tumor progression. HPLC was used to measure ADO levels in supernatants from 24 h co-cultures of bone marrow-derived DCs and irradiated TSA cells.In vitro, antibody blockade of CD73, the rate-limiting enzyme in the generation of ADO, reduced the levels of ADO in the supernatant and restored the activation of DCs cultured with irradiated TSA cells. In irradiated tumors, anti-CD73 reduced the percentage of Tregs within the tumor-infiltrating CD4+ T cell population (7.9±2.5% in RT+TY/23 vs 20±0.8% in RT, p&lt;0.01) while increasing CD8+ T cells (38.3±0.1% in RT+TY/23 vs 17.3±4% in RT, p&lt;0.05). Among intratumoral DCs, the CD8a+ DC subpopulation was increased after CD73-blockade (37.9±15.7% in TY/23+RT vs 11.3±4.9% in RT, p&lt;0.01). Importantly, in irradiated tumors, anti-CD73 enhanced expression of activation markers CD40 on CD8a+ DCs (MFI: 218±1 in RT+TY/23 vs 54±41 in RT, p&lt;0.05) and CD69 on CD8+ T cells (MFI: 513±126 in RT+TY/23 vs 148±59 in RT, p&lt;0.01). Furthermore, tumor-bearing mice treated with RT in combination with anti-CD73 had a significantly delayed tumor progression (p&lt;0.05) and prolonged survival (p&lt;0.01) compared to mice receiving RT alone. Anti-CD73 given alone had no effect on tumor growth.

Our data show that adenosinergic signaling regulates the ability of RT to induce anti-tumor immunity, affecting activation of both DCs and effector T cells. ADO blockade may represent a promising strategy to enhance the immunogenicity of irradiated tumors by improving the ability of RT to induce in situ tumor vaccination.

Citation Format: Erik Wennerberg, Aranzazu Mediero, Tuere Wilder, Silvia Formenti, Bruce Cronstein, Sandra Demaria. Adenosine regulates radiation therapy-induced antitumor immunity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4033.

Exercise in Regulation of Inflammation-Immune Axis Function in Cancer Initiation and Progression

Pharmacologic manipulation of the immune system is emerging as a viable and robust treatment for some cancer patients. Exercise-induced modulation of the immune system may be another adjunctive strategy for inhibiting tumor initiation and progression. In healthy individuals, exercise has been shown to modulate a number of cell subsets involved in innate and adaptive immunity. Here, we provide an overview of the current state of knowledge pertaining to exercise modulation of the inflammation-immune axis in cancer. The current evidence suggests that exercise may be a promising adjunctive strategy that can favorably alter numerous components of the immune system, which, in turn, may modulate tumorigenesis. However, many important knowledge gaps are evident. To this end, we propose a framework to guide future research efforts investigating the immune effects of exercise in cancer.

Abstract A21: Adenosine is a rheostat for radiation therapy-induced immune activation

Background: Administration of anti-CTLA-4 antibodies has shown clinical benefit in a small percentage of cancer patients. However, most patients are unresponsive to anti-CTLA-4 antibody treatment, due to immunosuppressive mechanisms and/or the absence of sufficient spontaneous anti-tumor T cells that can be activated by CTLA-4 blockade. We have previously shown that radiotherapy (RT) induces immunogenic tumor cell death and priming of anti-tumor T cells making tumors susceptible to anti-CTLA-4 treatment. RT also triggers the release of ATP in the tumor microenvironment, which has proinflammatory effects. However, ATP is rapidly converted into adenosine, a pleiotropic immunosuppressive mediator, by ectonucleotidases CD39 and CD73 expressed on cancer cells and tumor stromal cells. We hypothesized that adenosine generation in the tumor microenvironment acts as a rheostat modulating RT ability to prime effective anti-tumor immunity. To test this hypothesis we used a mouse tumor model where we have previously characterized two RT regimens that were efficient (8Gy x 3) or inefficient (20 Gy) in inducing anti-tumor immunity in combination with anti-CTLA-4 antibodies.

Method: BALB/c mice were inoculated s.c. with 1 x 105 TSA cells, a poorly immunogenic breast cancer cell line on day 0. Anti-CD73 mAb TY/23 (200 µg) was administered i.p. every 4 days starting on day 11. RT was given locally to the tumor as a single 20 Gy dose on day 12 or in three doses of 8 Gy each given on day 12, 13 and 14. At day 19, tumors were harvested and infiltrating immune cells were isolated for analysis of DC and T cell phenotype by flow cytometry. In another experiment, mice were randomly assigned (n=5/group) to be treated with: (1) Isotype control mAb (2) TY/23 (3) TY/23 + anti-CTLA-4 mAb 9H10 (4) RT 20 Gy (5) RT 20 Gy + TY/23 (6) RT 20 Gy + 9H10 (6) RT 20 Gy + TY/23+ 9H10. RT was given on day 12 and mAbs were administered i.p. on day 11, 14, 17 and 20 after tumor inoculation. Mice were monitored for tumor growth.

Results: In tumors that had received 8GyX3 RT there was a four-fold increase in CD70 expression (MFI 436 ± 72 in 8GyX3 vs. 110 ± 30 in control, p&lt;0.05) on CD8α+ dendritic cells (DCs), which are responsible for tumor-antigen cross-presentation. In addition, CD8+ T cells showed a two-fold increase in PD-1 expression (MFI 550 ± 22 in 8GyX3 vs. 271 ± 35 in control, p&lt;0.01) and 1.6-fold increase in CD69 expression (MFI 351 ± 95 in 8GyX3 vs. 225 ± 40 in control), indicating increased activation of both DC and T cells in tumors treated with 8GyX3 RT. In contrast, there was no evidence of activation of DC and T cells infiltrating tumors treated with 20Gy RT. However, when 20Gy RT was given in combination with TY/23 to block adenosine generation, DC and T cells showed an increase in expression of activation markers comparable to what was observed in tumors treated with 8GyX3. Interestingly, the frequency of intratumoral CD4+CD25+FoxP3+ regulatory T cells (Treg) was increased in mice receiving TY/23 + 8GyX3 (62% increase, p&lt;0.05) compared to TY/23 alone, suggesting that the inflammation induced by RT may trigger Treg recruitment to the tumor when it is not controlled by adenosine. TY/23 and 9H10 given alone or in combination did not have any effect on tumor growth. However, they improved tumor inhibition obtained with 20 Gy RT (Two-way ANOVA: p=0.08 for RT+anti-CD73 and p&lt;0.05 for RT+9H10 vs. RT alone). Moreover, blockade of both CD73 and CTLA-4 in combination with 20Gy RT further improved tumor control resulting in complete tumor regression in 2/5 mice (p&lt;0.01 for RT+TY/23+9H10 vs. RT alone).

Conclusions: Data indicate that the ability of RT to promote immune activation is dependent on the radiation regimen employed and is regulated by adenosine generation by the ectonucleotidase CD73. Importantly, data suggest that blocking CD73 can improve the ability of RT to synergize with immunotherapy.

Citation Format: Erik Wennerberg, Noriko Kawashima, Sandra Demaria. Adenosine is a rheostat for radiation therapy-induced immune activation. [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 A21.

In situ vaccination by radiotherapy to improve responses to anti-CTLA-4 treatment

Targeting immune checkpoint receptors has emerged as an effective strategy to induce immune-mediated cancer regression in the subset of patients who have significant pre-existing anti-tumor immunity. For the remainder, effective anti tumor responses may require vaccination. Radiotherapy, traditionally used to achieve local tumor control, has acquired a new role, that of a partner for immunotherapy. Ionizing radiation has pro-inflammatory effects that facilitate tumor rejection. Radiation alters the tumor to enhance the concentration of effector T cells via induction of chemokines, cytokines and adhesion molecules. In parallel, radiation can induce an immunogenic death of cancer cells, promoting cross-presentation of tumor-derived antigens by dendritic cells to T cells. Newly generated anti-tumor immune responses have been demonstrated post-radiation in both murine models and occasional patients, supporting the hypothesis that the irradiated tumor can become an in situ vaccine. It is in this role, that radiation can be applied to induce anti-tumor T cells in lymphocyte-poor tumors, and possibly benefit patients who would otherwise fail to respond to immune checkpoint inhibitors. This review summarizes preclinical and clinical data demonstrating that radiation acts in concert with antibodies targeting the immune checkpoint cytotoxic T-lymphocyte antigen-4 (CTLA-4), to induce therapeutically effective anti-tumor T cell responses in tumors otherwise non responsive to anti-CTLA-4 therapy.

CXCL10-induced migration of adoptively transferred human natural killer cells toward solid tumors causes regression of tumor growth in vivo

Adoptive infusion of natural killer (NK) cells is being increasingly explored as a therapy in patients with cancer, although clinical responses are thus far limited to patients with hematological malignancies. Inadequate homing of infused NK cells to the tumor site represents a key factor that may explain the poor anti-tumor effect of NK cell therapy against solid tumors. One of the major players in the regulation of lymphocyte chemotaxis is the chemokine receptor chemokine (C-X-C motif) receptor 3 (CXCR3) which is expressed on activated NK cells and induces NK cell migration toward gradients of the chemokine (C-X-C motif) ligand (CXCL9, 10 and 11). Here, we show that ex vivo expansion of human NK cells results in a tenfold increased expression of the CXCR3 receptor compared with resting NK cells (p = 0.04). Consequently, these NK cells displayed an improved migratory capacity toward solid tumors, which was dependent on tumor-derived CXCL10. In xenograft models, adoptively transferred NK cells showed increased migration toward CXCL10-transfected melanoma tumors compared with CXCL10-negative wild-type tumors, resulting in significantly reduced tumor burden and increased survival (median survival 41 vs. 32 days, p = 0.03). Furthermore, administration of interferon-gamma locally in the tumor stimulated the production of CXCL10 in subcutaneous melanoma tumors resulting in increased infiltration of adoptively transferred CXCR3-positive expanded NK cells. Our findings demonstrate the importance of CXCL10-induced chemoattraction in the anti-tumor response of adoptively transferred expanded NK cells against solid melanoma tumors.

Human anaplastic thyroid carcinoma cells are sensitive to NK cell-mediated lysis via ULBP2/5/6 and chemoattract NK cells

PURPOSE

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive forms of cancer with no curative therapies available. To date, strategies to target ATC by immunotherapy have not been evaluated. We investigated whether ATC would be a suitable target for natural killer (NK) cell-based immunotherapy.

EXPERIMENTAL DESIGN

We first established seven new cell lines from ATC tumors, three from papillary thyroid carcinoma tumors and analyzed them together with eight additional ATC cell lines. Cells were analyzed for sensitivity to lysis by NK cells and their ability to chemoattract and regulate the activity of NK cells. In addition, fresh tumor samples and peripheral blood from six patients with ATC were analyzed for NK cell infiltration and phenotype.

RESULTS

We observed that ATC cell lines are sensitive to lysis by ex vivo expanded NK cells and that the lysis was abrogated upon blockade of NKG2D. Sensitivity of thyroid cancer cell lines to NK cell-mediated lysis correlated with surface expression of UL16-binding protein 2 on tumor cells. Moreover, ATC cell lines produced high levels of CXCL10 and stimulated migration of expanded NK cells and ATC tumors were enriched for NK cells expressing the cognate chemokine receptor CXCR3. However, compared with NK cells in peripheral blood, ATC tumor-derived NK cells displayed a suppressed phenotype with a downregulated expression of NKG2D. In vitro, suppression of NK cell-mediated lysis and NKG2D expression by ATC cells was restored upon neutralization of prostaglandin-E2.

CONCLUSIONS

ATC cell lines are sensitive to NK cell-mediated lysis via ULBP2/5/6 and chemoattract CXCR3-positive NK cells. Patients with ATC may benefit from NK cell-based immunotherapy.

Opposing consequences of signaling through EGF family members: Escape from CTLs could be a bait for NK cells

Oncogenes have been traditionally viewed as molecular drivers for tumor growth and survival. Recent evidence indicates that oncogenes may facilitate the escape of malignant cells from immune recognition and elimination. In this article, we discuss the implications of the overexpression of epidermal growth factor receptor (EGFR) family members on immune escape of tumors and immunotherapy.

Gap junction intercellular communications regulate NK cell activation and modulate NK cytotoxic capacity

Gap junctions (GJs) mediate intercellular communication between adjacent cells. Previously, we showed that connexin 43 (Cx43), the main GJ protein in the immune system, mediates Ag transfer between human dendritic cells (DCs) and is recruited to the immunological synapse during T cell priming. This crosstalk contributed to T cell activation, intracellular Ca(2+) responses, and cytokine release. However, the role of GJs in NK cell activation by DCs and NK cell-mediated cytotoxicity against tumor cells remains unknown. In this study, we found polarization of Cx43 at the NK/DC and NK/tumor cell-contact sites, accompanied by the formation of functional GJs between NK/DCs and NK/tumor cells, respectively. Cx43-GJ-mediated intercellular communication (GJIC) between human NK and DCs was bidirectional. Blockage of Cx43-GJIC inhibited NK cell activation, though it affected neither the phenotype nor the function of DCs. Cx43 knockdown or inhibition using mimetic peptides greatly reduced CD69 and CD25 expression and IFN-γ release by DC-stimulated NK cells. Moreover, blocking Cx43 strongly inhibited the NK cell-mediated tumor cell lysis associated with inhibition of granzyme B activity and Ca(2+) influx. Our data identify a novel and active role for Cx43-GJIC in human NK cell activation and antitumor effector functions that may be important for the design of new immune therapeutic strategies.

A novel inhibitor of proteasome deubiquitinating activity renders tumor cells sensitive to TRAIL-mediated apoptosis by natural killer cells and T cells

The proteasome inhibitor bortezomib simultaneously renders tumor cells sensitive to killing by natural killer (NK) cells and resistant to killing by tumor-specific T cells. Here, we show that b-AP15, a novel inhibitor of proteasome deubiquitinating activity, sensitizes tumors to both NK and T cell-mediated killing. Exposure to b-AP15 significantly increased the susceptibility of tumor cell lines of various origins to NK (p < 0.0002) and T cell (p = 0.02)-mediated cytotoxicity. Treatment with b-AP15 resulted in increased tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor-2 expression (p = 0.03) and decreased cFLIP expression in tumor cells in vitro. In tumor-bearing SCID/Beige mice, treatment with b-AP15 followed by infusion of either human NK cells or tumor-specific T cells resulted in a significantly delayed tumor progression compared with mice treated with NK cells (p = 0.006), T cells (p < 0.0001) or b-AP15 alone (p = 0.003). Combined infusion of NK and T cells in tumor-bearing BALB/c mice following treatment with b-AP15 resulted in a significantly prolonged long-term survival compared with mice treated with b-AP15 and NK or T cells (p ≤ 0.01). Our findings show that b-AP15-induced sensitization to TRAIL-mediated apoptosis could be used as a novel strategy to augment the anticancer effects of adoptively infused NK and T cells in patients with cancer.

Melanoma-educated CD14+ cells acquire a myeloid-derived suppressor cell phenotype through COX-2-dependent mechanisms

Tumors can suppress the host immune system by employing a variety of cellular immune modulators, such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells (MDSC). In the peripheral blood of patients with advanced stage melanoma, there is an accumulation of CD14(+)HLA-DR(lo/-) MDSC that suppress autologous T cells ex vivo in a STAT-3-dependent manner. However, a precise mechanistic basis underlying this effect is unclear, particularly with regard to whether the MDSC induction mechanism relies on cell-cell contact of melanoma cells with CD14(+) cells. Here, we show that early-passage human melanoma cells induce phenotypic changes in CD14(+) monocytes, leading them to resemble MDSCs characterized in patients with advanced stage melanoma. These MDSC-like cells potently suppress autologous T-cell proliferation and IFN-γ production. Notably, induction of myeloid-suppressive functions requires contact or close proximity between monocytes and tumor cells. Further, this induction is largely dependent on production of cyclooxygenase-2 (COX-2) because its inhibition in these MDSC-like cells limits their ability to suppress T-cell function. We confirmed our findings with CD14(+) cells isolated from patients with advanced stage melanoma, which inhibited autologous T cells in a manner relying up prostaglandin E2 (PGE2), STAT-3, and superoxide. Indeed, PGE2 was sufficient to confer to monocytes the ability to suppress proliferation and IFN-γ production by autologous T cells ex vivo. In summary, our results reveal how immune suppression by MDSC can be initiated in the tumor microenvironment of human melanoma.

Doxorubicin sensitizes human tumor cells to NK cell- and T-cell-mediated killing by augmented TRAIL receptor signaling

Doxorubicin (DOX) is an anthracycline antibiotic that is widely used to treat different types of malignancy. In this study, it was studied whether DOX could be used to render tumor cells susceptible to apoptosis by NK and T cells. Pretreatment with subapoptotic doses of DOX sensitized tumor cell lines of various histotypes to both NK and T cells resulting in a 3.7 to 32.7% increase in lysis (2.5 mean fold increase, p < 0.0001) and a 2.9 to 14.2% increase in lysis (3.0 mean-fold increase, p < 0.05), respectively. The sensitizing effect of the drug was primarily dependent on the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/TRAIL-receptor signaling, but not on Fas-ligand, perforin, NKG2D or DNAM-1. The central role of the TRAIL signaling pathway was further supported by an increased expression of TRAIL-R2 on DOX-treated tumor cells and by downregulation of cellular FLICE inhibitory protein, the inhibitors of death receptor-mediated apoptosis. Compared to untreated cells, pretreatment of tumor cells with DOX showed increased processing and activation of caspase-8 on coculture with NK or T cells. The significance of this treatment strategy was confirmed using a xenogeneic tumor-bearing mouse model. Tumor progression was delayed in mice that received either NK cells (p < 0.05) or T cells (p < 0.0001) following DOX treatment compared to mice receiving either cell type alone. Moreover, combined infusion of both NK and T cells following DOX treatment not only delayed tumor progression but also significantly improved the long-term survival (p < 0.01). Based on these findings, it was proposed that DOX can be used to improve the efficacy of adoptive cell therapy in patients with cancer.

Abstract A15: IFN-gamma-inducible-protein-10 stimulates intratumoral infiltration of adoptively transferred human NK cells in a melanoma xenograft mouse model

Aim: In the present study, we investigated whether adoptively transferred human NK cells would migrate towards IP-10 producing melanoma tumors in a xenograft mouse model. Moreover, we assessed the effect of the chemotherapeutic agent doxorubicin in increasing the sensitivity of IFNγ-treated tumors to NK cell lysis in vitro and in vivo.

Background: Adoptive transfer of natural killer (NK) cells is being increasingly used in the treatment of cancer. However, clinical trials involving adoptive transfer of NK cells have to date been more successful against leukemia and other blood-borne cancers than against solid tumors. Several groups have reported that intratumoral infiltration of NK cells correlates with improved prognosis in patients with solid tumors. Recruitment and infiltration and of NK cells in the tumor is dependent on the production of IFN-gamma-inducible-protein-10 (IP-10) by tumor cells. Although tumor cells can be triggered to produce IP-10 by IFNγ stimulation, the expression of MHC class I is increased on tumor cells resulting in decreased sensitivity to NK cell lysis.

Results: Following activation with IL-2, human NK cells upregulated the chemokine receptor CXCR3 resulting in significantly increased migration toward recombinant IP-10, MIG and I-TAC in a transwell migration assay (p=0.03). Expanded NK cells also migrated toward melanoma tumor cells that had been stimulated with IFNγ to induce secretion of IP-10 (p&lt;0.01). In an in vivo xenograft model, an increased accumulation of adoptively infused human NK cells could be detected in subcutaneous melanoma tumors transfected with IP-10 while IP-10 negative tumors had little or no NK cell infiltration (p=0.02). Following infusion of expanded NK cells, significantly reduced tumor burden (p=0.02) and prolonged survival was observed in mice bearing IP-10 positive tumors than mice bearing IP-10 negative tumors (p=0.03). We found that in mice bearing subcutaneous melanoma tumors, intratumoral injections of IFNγ triggered IP-10 production, as confirmed by protein analysis of tumor lysates. Mice that received intravenous injections of doxorubicin prior to IFNγ-injections and adoptive transfer of NK cells had a slower tumor progression than mice that received IFNγ alone prior to NK cell transfer.

Conclusion: Secretion of IP-10 from melanoma tumors stimulates intratumoral infiltration of adoptively transferred NK cells, demonstrating the importance of IP-10/CXCR3 signaling in recruitment of NK cells to solid tumors. Intratumoral IFNγ-treatment of tumors triggers an increased local production of IP-10. Pretreatment of tumor cells with doxorubicin can offset INFγ-induced resistance to NK cell lysis in vitro and in vivo.

Citation Format: Erik Wennerberg, Veronika Kremer, Andreas Lundqvist. IFN-gamma-inducible-protein-10 stimulates intratumoral infiltration of adoptively transferred human NK cells in a melanoma xenograft mouse model. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A15.

Activated monocytes augment TRAIL-mediated cytotoxicity by human NK cells through release of IFN-γ

Natural killer (NK) cells are innate lymphocytes that are able to directly kill tumor cells through different mechanisms including ligation of TNF-related apoptosis-inducing ligand (TRAIL) receptors. Zoledronic acid (ZA) is a bisphosphonate known to upregulate the expression of TRAIL on human γδ T cells. Here, we investigated whether exposure to ZA would upregulate TRAIL expression on human NK cells and augment their cytotoxicity against tumor cells. When cocultured with monocytes, treatment with ZA and IL-2 resulted in a significant upregulation of TRAIL expression on human NK cells (p = 0.002). Consequently, ZA-primed NK cells were significantly more cytotoxic against TRAIL sensitive tumor cells (p < 0.0001). In the presence of ZA and IL-2, monocytes produced high levels of IFN-γ; when cultured in the presence of neutralizing antibodies to IFN-γ, TRAIL expression and TRAIL-mediated cytotoxicity of NK cells were significantly reduced. Furthermore, in tumor-bearing SCID/Beige mice, a significant delayed tumor progression and prolonged survival was observed after infusion of ZA-primed NK cells compared with that observed in mice infused with unprimed NK cells. These findings represent a novel approach to potentiate TRAIL-mediated apoptosis by adoptively infused NK cells that could improve the outcome in patients with cancer.

HER2/HER3 signaling regulates NK cell-mediated cytotoxicity via MHC class I chain-related molecule A and B expression in human breast cancer cell lines

Overexpression of the receptor tyrosine kinases HER2 and HER3 is associated with a poor prognosis in several types of cancer. Presently, HER2- as well as HER3-targeted therapies are in clinical practice or evaluated within clinical trials, including treatment with mAbs mediating growth inhibition and/or activation of Ab-induced innate or adaptive cellular immunity. A better understanding of how HER2/HER3 signaling in tumors influences cellular immune mechanisms is therefore warranted. In this study, we demonstrate that HER2/HER3 signaling regulates the expression of MHC class I-related chain A and B (MICA and MICB) in breast cancer cell lines. The MICA and MICB (MICA/B) molecules act as key ligands for the activating receptor NK group 2, member D (NKG2D) and promote NK cell-mediated recognition and cytolysis. Genetic silencing of HER3 but not HER2 downregulated the expression of MICA/B, and HER3 overexpression significantly enhanced MICA expression. Among the major pathways activated by HER2/HER3 signaling, the PI3K/AKT pathway was shown to predominantly regulate MICA/B expression. Treatment with the HER3-specific ligand neuregulin 1β promoted the expression in a process that was antagonized by pharmacological and genetic interference with HER3 but not by the ataxia-telangiectasia-mutated (ATM) and ATM and Rad3-related protein kinases inhibitor caffeine. These observations further emphasize that HER2/HER3 signaling directly, and not via genotoxic stress, regulates MICA/B expression. As anticipated, stimulating HER2/HER3 enhanced the NKG2D-MICA/B-dependent NK cell-mediated cytotoxicity. Taken together, we conclude that signaling via the HER2/HER3 pathway in breast carcinoma cell lines may lead to enhanced NKG2D-MICA/B recognition by NK cells and T cells.