Converging focal radiation and immunotherapy in a preclinical model of triple negative breast cancer: contribution of VISTA blockade

Antibodies targeting the co-inhibitory receptor programmed cell death 1 (PDCD1, best known as PD-1) or its main ligand CD274 (best known as PD-L1) have shown some activity in patients with metastatic triple-negative breast cancer (TNBC), especially in a recent Phase III clinical trial combining PD-L1 blockade with taxane-based chemotherapy. Despite these encouraging findings, however, most patients with TNBC fail to derive significant benefits from PD-L1 blockade, calling for the identification of novel therapeutic approaches. Here, we used the 4T1 murine mammary cancer model of metastatic and immune-resistant TNBC to test whether focal radiation therapy (RT), a powerful inducer of immunogenic cell death, in combination with various immunotherapeutic strategies can overcome resistance to immune checkpoint blockade. Our results suggest that focal RT enhances the therapeutic effects of PD-1 blockade against primary 4T1 tumors and their metastases. Similarly, the efficacy of an antibody specific for V-set immunoregulatory receptor (VSIR, another co-inhibitory receptor best known as VISTA) was enhanced by focal RT. Administration of cyclophosphamide plus RT and dual PD-1/VISTA blockade had superior therapeutic effects, which were associated with activation of tumor-infiltrating CD8⁺ T cells and depletion of intratumoral granulocytic myeloid-derived suppressor cells (MDSCs). Overall, these results demonstrate that RT can sensitize immunorefractory tumors to VISTA or PD-1 blockade, that this effect is enhanced by the addition of cyclophosphamide and suggest that a multipronged immunotherapeutic approach may also be required to increase the incidence of durable responses in patients with TNBC.

IL15 synergizes with radiotherapy to reprogram the tumor immune contexture through a dendritic cell connection

IL15 is a key cytokine for the activation and survival of anti-tumor effectors CD8⁺ T and NK cells. Recently published preclinical studies demonstrate that the therapeutic activity of IL15 requires conventional dendritic cells type 1 (cDC1). Radiotherapy cooperates with IL15 by enhancing cDC1 tumor infiltration via interferon type 1 activation.

Radiotherapy Cooperates with IL15 to Induce Antitumor Immune Responses

Focal radiotherapy can promote cross-presentation of tumor antigens to T cells, but by itself, it is insufficient to induce therapeutically effective T-cell responses. The common gamma-chain cytokine IL15 promotes and sustains the proliferation and effector function of CD8⁺ T cells but has limited activity against poorly immunogenic tumors that do not elicit significant spontaneous T-cell responses. Here, we show that radiotherapy and subcutaneous IL15 had complementary effects and induced CD8⁺ T-cell-mediated tumor regression and long-term protective memory responses in two mouse carcinoma models unresponsive to IL15 alone. Mechanistically, radiotherapy-induced IFN type I production and Batf3-dependent conventional dendritic cells type 1 (cDC1) were required for priming of tumor-specific CD8⁺ T cells and for the therapeutic effect of the combination. IL15 cooperated with radiotherapy to activate and recruit cDC1s to the tumor. IL15 alone and in complex with a hybrid molecule containing the IL15α receptor have been tested in early-phase clinical trials in patients with cancer and demonstrated good tolerability, especially when given subcutaneously. Expansion of natural killer (NK) cells and CD8⁺ T cells was noted, without clear clinical activity, suggesting further testing of IL15 as a component of a combinatorial treatment with other agents. Our results provide the rationale for testing combinations of IL15 with radiotherapy in the clinic.

Exosomes Shuttle TREX1-Sensitive IFN-Stimulatory dsDNA from Irradiated Cancer Cells to DCs

Radiotherapy (RT) used at immunogenic doses leads to accumulation of cytosolic double-stranded DNA (dsDNA) in cancer cells, which activates type I IFN (IFN-I) via the cGAS/STING pathway. Cancer cell-derived IFN-I is required to recruit BATF3-dependent dendritic cells (DC) to poorly immunogenic tumors and trigger antitumor T-cell responses in combination with immune checkpoint blockade. We have previously demonstrated that the exonuclease TREX1 regulates radiation immunogenicity by degrading cytosolic dsDNA. Tumor-derived DNA can also activate cGAS/STING-mediated production of IFN-I by DCs infiltrating immunogenic tumors. However, how DNA from cancer cells is transferred to the cytoplasm of DCs remains unclear. Here, we showed that tumor-derived exosomes (TEX) produced by irradiated mouse breast cancer cells (RT-TEX) transfer dsDNA to DCs and stimulate DC upregulation of costimulatory molecules and STING-dependent activation of IFN-I. In vivo, RT-TEX elicited tumor-specific CD8⁺ T-cell responses and protected mice from tumor development significantly better than TEX from untreated cancer cells in a prophylactic vaccination experiment. We demonstrated that the IFN-stimulatory dsDNA cargo of RT-TEX is regulated by TREX1 expression in the parent cells. Overall, these results identify RT-TEX as a mechanism whereby IFN-stimulatory dsDNA is transferred from irradiated cancer cells to DCs. We have previously shown that the expression of TREX1 is dependent on the RT dose size. Thus, these data have important implications for the use of RT with immunotherapy. Cancer Immunol Res; 6(8); 910-20. ©2018 AACR.

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.

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.

Therapeutic effect of local Interleukin-15 with radiotherapy in breast cancer

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Background: Interleukin (IL)-15 is a key regulator of T cell homeostasis with activity in cancer and a favorable toxicity profile compared to IL-2. IL-15 stimulates the proliferation and effector differentiation of CD8+T cells, and the proliferation and activation of natural killer (NK) cells. We observed IL-15 upregulation by gene arrays in radiotherapy (RT)-treated TSA mouse breast cancer, suggesting that it may play a role in RT-induced anti-tumor immunity. However, the upregulation was modest prompting us to test the hypothesis that administration of IL-15 may enhance in situ vaccination by RT. Methods: BALB/c mice with established poorly immunogenic TSA tumors were sham-treated, treated with tumor-targeted RT (8GyX3 days), IL-15 given peri-tumorally (2 ug/mouse/day for 10 days) starting on the first day of RT, and RT+IL-15, and monitored for tumor growth and survival. Tumor infiltrating lymphocytes (TIL) were analyzed by flow cytometry and immunostaining. In some experiments, Batf3-/-mice were used as tumor recipient. Results: IL-15 by itself was ineffective, but it significantly increased tumor control by RT (p=0.0007, RT versus RT+IL-15) leading to complete responses in 50% of the mice, most of them durable. Analysis of TILs showed significantly increased NK cells (CD45+ CD3- DX5+) in tumors treated with RT+IL-15 (p<0.0004 versus sham-treated; p<0.02 versus RT). NK cells were also more activated as indicated by expression of CD122 and CD137. Depletion of NK cells completely abrogated the therapeutic effect of the combination, while CD8 T cell depletion reduced tumor control and rate of complete regression. Interestingly, Batf3-/- mice, which lack CD103+ DCs, showed reduced response to RT+IL-15 compared to WT mice. Conclusions: Data suggest that local IL-15 with RT is an effective strategy to induce anti-tumor immunity to poorly immunogenic breast cancer. NK cells are critical mediators of the response, and may act by both killing tumor cells and promoting priming of CD8 T cells. Experiments are ongoing to determine the mechanisms of durable complete responses. <footer>Acknowledgments: IL-15 was provided by NCI BRB. Garcia-Martinez E was supported by GEICAM grant.</footer>

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

CD8(+) T-cell Immune Evasion Enables Oncolytic Virus Immunotherapy

Although counteracting innate defenses allows oncolytic viruses (OVs) to better replicate and spread within tumors, CD8(+) T-cells restrict their capacity to trigger systemic anti-tumor immune responses. Herpes simplex virus-1 (HSV-1) evades CD8(+) T-cells by producing ICP47, which limits immune recognition of infected cells by inhibiting the transporter associated with antigen processing (TAP). Surprisingly, removing ICP47 was assumed to benefit OV immuno-therapy, but the impact of inhibiting TAP remains unknown because human HSV-1 ICP47 is not effective in rodents. Here, we engineer an HSV-1 OV to produce bovine herpesvirus UL49.5, which unlike ICP47, antagonizes rodent and human TAP. Significantly, UL49.5-expressing OVs showed superior efficacy treating bladder and breast cancer in murine models that was dependent upon CD8(+) T-cells. Besides injected subcutaneous tumors, UL49.5-OV reduced untreated, contralateral tumor size and metastases. These findings establish TAP inhibitor-armed OVs that evade CD8(+) T-cells as an immunotherapy strategy to elicit potent local and systemic anti-tumor responses.

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.

Combination of radiotherapy and immune checkpoint inhibitors

The ability of ionizing radiation to cause cell death and inflammatory reactions has been known since the beginning of its therapeutic use in oncology. However, only recently this property of radiation has attracted the attention of immunologists seeking to induce or improve antitumor immunity. As immune checkpoint inhibitors are becoming mainstream cancer treatments, radiation oncologists have begun to observe unexpected out-of-the-field (abscopal) responses in patients receiving radiation therapy during immunotherapy. These unexpected responses were predicted by experimental work in preclinical tumor models and have clear biological bases. Accumulating experimental evidence that radiation induces an immunogenic cell death and promotes recruitment and function of T cells within the tumor microenvironment supports the hypothesis that radiation can convert the tumor into an in situ individualized vaccine. This property of radiation is key to its synergy with immune checkpoint inhibitors, antibodies targeting inhibitory receptors on T cells such as cytotoxic T lymphocyte antigen-4 and programmed death-1. By removing the obstacles hindering the activation and function of antitumor T cells, these agents benefit patients with pre-existing antitumor immunity but are ineffective in patients lacking these spontaneous responses. Radiation induces antitumor T cells complementing the activity of immune checkpoint inhibitors.

Abstract 2493: Fractionated but not single dose radiation is an optimal adjuvant for in situ tumor vaccination

Local radiotherapy (RT) has the potential to generate an in situ tumor vaccine by inducing an immunogenic cell death (ICD) of the cancer cells. In vitro, generation of the signals that define ICD is radiation dose-dependent. However, in vivo we have previously shown that radiation doses of 8 and 6 Gy given in 3 to 5 consecutive days were more effective at inducing anti-tumor T cell responses in combination with anti-CTLA-4 antibody than a single larger dose of 20 Gy (Dewan et al., Clin Cancer Res 2009).

To understand the mechanisms underlying the different outcome obtained with fractionated versus single dose RT, TSA tumors growing in syngeneic immunocompetent BALB/c mice were harvested at 4, 24 and 48 hrs post irradiation with 8 Gy X 3 or 20 Gy X 1 for analysis of gene expression using Agilent mouse mRNA Microarray Kit (V2). Subsequent data were analyzed using Ingenuity Pathway Analysis (IPA) and gene ontology classification. Expression of key immune genes in TSA cells irradiated in vitro was assessed by RT-qPCR. Tumor-infiltrating dendritic cells (TIDC) were analyzed 5 days after the last radiation exposure by flow cytometry. IFNβ production by irradiated TSA cells was measured by Procarta™ immunoassay.

Over 100 immune response genes were differentially expressed in tumors irradiated with 8Gyx3 but not 20Gyx1, with a dominant type I interferon (IFN) response at 4 and 24 hours, which was confirmed by RT-qPCR. Tumor infiltration by CD8α+ dendritic cells (DC), which are the subset of DC cross-presenting tumor cell-derived antigens, was only slightly increased by 20Gyx1 but markedly increased by 8Gyx3. Moreover, DCs present in tumors treated with 8Gyx3 showed a significant upregulation of activation markers CD40 and CD70. Importantly, the in vitro setting (devoid of an immune infiltrate) demonstrated expression of IFNβ and downstream immune genes, including chemokines CXCL9, CXCL10 and CXCL11 by TSA cells irradiated with 8Gyx3 but not 20Gyx1. Production of IFNβ by TSA cells was confirmed with an increased secretion of IFNβ in the supernatant only after 8Gyx3 irradiation.

Overall, data indicate that fractionated RT can mimic, at least in part, a viral infection and activate canonical defense pathways in neoplastic epithelial cells with induction of type-I IFN. In vivo this leads to recruitment and activation of DC cross-presenting tumor antigens. Thus, fractionated-RT acts as an optimal immune adjuvant for in situ tumor vaccination. We propose that repeated cycles of RT-induced cell death may better mimick cycles of viral infection and are currently defining the molecular mechanisms involved. Results are important for understanding the determinant of response in patients currently treated wit RT and anti-CTLA-4 in clinical trials at our institution.

Citation Format: Claire Isabelle Vanpouille-Box, Molykutty Aryankalayil, Karsten A. Pilones, Silvia C. Formenti, Norman Coleman, Sandra Demaria. Fractionated but not single dose radiation is an optimal adjuvant for in situ tumor vaccination. [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 2493. doi:10.1158/1538-7445.AM2015-2493

TGFβ Is a Master Regulator of Radiation Therapy-Induced Antitumor Immunity

T cells directed to endogenous tumor antigens are powerful mediators of tumor regression. Recent immunotherapy advances have identified effective interventions to unleash tumor-specific T-cell activity in patients who naturally develop them. Eliciting T-cell responses to a patient's individual tumor remains a major challenge. Radiation therapy can induce immune responses to model antigens expressed by tumors, but it remains unclear whether it can effectively prime T cells specific for endogenous antigens expressed by poorly immunogenic tumors. We hypothesized that TGFβ activity is a major obstacle hindering the ability of radiation to generate an in situ tumor vaccine. Here, we show that antibody-mediated TGFβ neutralization during radiation therapy effectively generates CD8(+) T-cell responses to multiple endogenous tumor antigens in poorly immunogenic mouse carcinomas. Generated T cells were effective at causing regression of irradiated tumors and nonirradiated lung metastases or synchronous tumors (abscopal effect). Gene signatures associated with IFNγ and immune-mediated rejection were detected in tumors treated with radiation therapy and TGFβ blockade in combination but not as single agents. Upregulation of programmed death (PD) ligand-1 and -2 in neoplastic and myeloid cells and PD-1 on intratumoral T cells limited tumor rejection, resulting in rapid recurrence. Addition of anti-PD-1 antibodies extended survival achieved with radiation and TGFβ blockade. Thus, TGFβ is a fundamental regulator of radiation therapy's ability to generate an in situ tumor vaccine. The combination of local radiation therapy with TGFβ neutralization offers a novel individualized strategy for vaccinating patients against their tumors.

Exploiting the stress response to radiation to sensitize poorly immunogenic tumors to anti-CTLA-4 treatment

Radiotherapy sensitizes unresponsive tumors to the antineoplastic activity of antibodies that target the inhibitory receptor CTLA-4 on T cells. One molecular mechanism accounting for this therapeutic synergy is the induction of NKG2D ligands on irradiated tumor cells. The fact that NKG2D receptors must be engaged for the elicitation of CD8⁺ T-cell antitumor responses has important clinical implications.

Invariant natural killer T cells regulate anti-tumor immunity by controlling the population of dendritic cells in tumor and draining lymph nodes

BACKGROUND

Invariant natural killer T (iNKT) cells are CD1d-restricted T cells, which respond rapidly to antigen recognition and promote development of anti-tumor immunity in many tumor models. Surprisingly, we previously found that mice deficient in iNKT cells developed spontaneous CD8(+) T cells responses partially effective at inhibiting metastases in mice bearing the 4T1 mammary carcinoma, and showed a markedly improved response to treatment with local radiotherapy and anti-CTLA-4 antibody compared to wild type (WT) mice.

METHODS

To understand the mechanisms of the immunosuppressive function of iNKT cells, dendritic cells (DCs) were analyzed by immunohistochemistry and flow cytometry in WT and iNKT-deficient (iNKT(-/-)) mice. The effects of antibody-mediated blockade of CD1d on DC number and phenotype, priming of anti-tumor T cells, and tumor response to treatment with local radiotherapy and anti-CTLA-4 antibody were evaluated. To determine if the improved response to treatment in the absence of iNKT cells was independent from the immunotherapy employed, 4T1-tumor bearing WT and iNKT(-/-) mice were treated with local radiotherapy in combination with antibody-mediated CD137 co-stimulation.

RESULTS

DCs in 4T1 tumors and tumor-draining lymph nodes but not distant lymph nodes were significantly reduced in WT mice compared to iNKT(-/-) mice (p < 0.05), suggesting the selective elimination of DCs cross-presenting tumor-associated antigens by iNKT cells. Consistently, priming of T cells to a tumor-specific CD8 T cell epitope in mice treated with radiotherapy and anti-CTLA-4 or anti-CD137 was markedly enhanced in iNKT(-/-) compared to WT mice. CD1d blockade restored the number of DC in WT mice, improved T cell priming in draining lymph nodes and significantly enhanced response to treatment.

CONCLUSIONS

Here we describe a novel mechanism of tumor immune escape mediated by iNKT cells that limit priming of anti-tumor T cells by controlling DC in tumors and draining lymph nodes. These results have important implications for the design of immunotherapies targeting iNKT cells.

The optimal partnership of radiation and immunotherapy: from preclinical studies to clinical translation

The main role of the immune system is to restore tissue homeostasis when altered by pathogenic processes, including neoplastic transformation. Immune-mediated tumor rejection has been recognized as an extrinsic tumor suppressor mechanism that tumors need to overcome to progress. By the time a tumor becomes clinically apparent it has successfully escaped immune control by establishing an immunosuppressive microenvironment. Ionizing radiation applied locally to a tumor alters these tumor-host interactions. Accumulating evidence indicates that standard therapeutic doses of radiation have the potential to recover tumor immunogenicity and convert the tumor into an in situ personalized vaccine. Radiotherapy induces an immunogenic tumor cell death promoting cross-presentation of tumor-derived antigens by dendritic cells to T cells. In addition, radiotherapy stimulates chemokine-mediated recruitment of effector T cells to the tumor, and cellular recognition and killing by T cells that is facilitated by upregulation of major histocompatibility antigens, NKG2D ligands, adhesion molecules and death receptors. Despite these effects, radiotherapy alone is only rarely capable of generating enough proinflammatory signals to sufficiently overcome suppression, as it can also activate immunosuppressive factors. However, our group and others have shown that when combined with targeted immunotherapy agents radiotherapy significantly contributes to a therapeutically effective anti-tumor immune response. To illustrate this partnership between radiation and immunotherapy we will discuss as an example our experience in preclinical models and the molecular mechanisms identified. Additionally, the clinical translation of these combinations will be discussed.

Invariant NKT cells as novel targets for immunotherapy in solid tumors

Natural killer T (NKT) cells are a small population of lymphocytes that possess characteristics of both innate and adaptive immune cells. They are uniquely poised to respond rapidly to infection and inflammation and produce cytokines that critically shape the ensuing adaptive cellular response. Therefore, they represent promising therapeutic targets. In cancer, NKT cells are attributed a role in immunosurveillance. NKT cells also act as potent activators of antitumor immunity when stimulated with a synthetic agonist in experimental models. However, in some settings, NKT cells seem to act as suppressors and regulators of antitumor immunity. Here we briefly review current data supporting these paradoxical roles of NKT cells and their regulation. Increased understanding of the signals that determine the function of NKT cells in cancer will be essential to improve current strategies for NKT-cell-based immunotherapeutic approaches.

Suppressing T cell motility induced by anti-CTLA-4 monotherapy improves antitumor effects

A promising strategy for cancer immunotherapy is to disrupt key pathways regulating immune tolerance, such as cytotoxic T lymphocyte-associated protein 4 (CTLA-4). However, the determinants of response to anti-CTLA-4 mAb treatment remain incompletely understood. In murine models, anti-CTLA-4 mAbs alone fail to induce effective immune responses to poorly immunogenic tumors but are successful when combined with additional interventions, including local ionizing radiation (IR) therapy. We employed an established model based on control of a mouse carcinoma cell line to study endogenous tumor-infiltrating CD8+ T lymphocytes (TILs) following treatment with the anti-CTLA-4 mAb 9H10. Alone, 9H10 monotherapy reversed the arrest of TILs with carcinoma cells in vivo. In contrast, the combination of 9H10 and IR restored MHC class I-dependent arrest. After implantation, the carcinoma cells had reduced expression of retinoic acid early inducible-1 (RAE-1), a ligand for natural killer cell group 2D (NKG2D) receptor. We found that RAE-1 expression was induced by IR in vivo and that anti-NKG2D mAb blocked the TIL arrest induced by IR/9H10 combination therapy. These results demonstrate that anti-CTLA-4 mAb therapy induces motility of TIL and that NKG2D ligation offsets this effect to enhance TILs arrest and antitumor activity.

P1-01-05: Conditioning by the Tumor Environment Turns Invariant Natural Killer T Cells into Negative Regulators of Anti-Tumor Immunity Elicited by Treatment

Background: Local suppression in the tumor microenvironment remains an important obstacle to success of immune-based therapy. We have previously shown in the 4T1 model of metastatic breast cancer that combination radiotherapy (RT) to the primary tumor and CTLA-4 blockade can elicit a robust anti-tumor effector response that can inhibit metastases and prolong survival. However, complete cure and long-term memory was seen in only a small fraction of mice, prompting us to investigate new ways to improve the response elicited by treatment. iNKT cells are known to be powerful regulators of tumor immunity as a result of their ability to rapidly secrete a broad range of cytokines, but the mechanisms regulating their switch from a stimulatory to a regulatory role remain poorly defined. We have previously shown that iNKT cells negatively regulate the response to treatment with RT and CTLA-4 blockade in 4T1 tumor-bearing mice (Clin Cancer Res 15:597, 2009). Here, we test the novel hypothesis that conditioning of iNKT cells to perform this regulatory role occurs within the tumor microenvironment. Specifically, we address whether 4T1 tumor cells, directly or indirectly, promote iNKT cell regulatory phenotype. Methods: For in vitro experiments, 4T1 tumor or LPS-matured bone marrow-derived dendritic cells (BMDC) were loaded with α-galactosylceramide and used to stimulate the NKT DN32.D3 hybridoma cells. In some wells, BMDCs were supplemented with 4T1 conditioned media or loaded with tumor lysates from 4T1 cells. For in vivo experiments, wild-type and iNKT-deficient mice were inoculated s.c with 4T1 cells for enumeration of DCs on immunostained sections. Phenotypic profile of DCs within tumor and draining lymph nodes were assessed by flow cytometry. Results: 4T1 cells are positive for CD1d by real-time RT-PCR; surface CD1d were barely detectable by flow cytometry but sufficient to induce activation of DN32.D3 cells when irradiated 4T1 cells were loaded with α-GalCer. BMDC supplemented with conditioned media from untreated or irradiated 4T1 cells, or loaded with tumor lysates from irradiated 4T1 cells were also able to activate DN32.D3 cells, and this effect was partially inhibited by blocking CD1d mAb (1B1) in a dose-dependent manner. In vivo, we found that iNKT-deficient mice showed significantly (p=0.04) higher densities of tumor infiltrating DCs than wild type mice. Moreover, DC in tumor and tumor-draining lymph nodes expressed markers of maturation in the absence but not presence of iNKT cells. Conclusion: Results indicate that a 4T1 derived factor, possibly a lipid antigen that can be presented directly by tumor cells themselves or indirectly by BMDCs induces activation of iNKT cells in vitro. In vivo, data suggests that iNKT cells downregulate the response to treatment by controlling the population of DC present in the tumor and draining lymph nodes. Since DC are essential for cross-presentation of the tumor antigens released by RT-induced cell death, reduced DC numbers may impair the activation of anti-tumor T cells. Supported by DOD Postdoctoral Award W81XWH-10-1-

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-01-05.

TGFβ1 inhibition increases the radiosensitivity of breast cancer cells in vitro and promotes tumor control by radiation in vivo

PURPOSE

To determine whether inhibition of TGFβ signaling prior to irradiation sensitizes human and murine cancer cells in vitro and in vivo.

EXPERIMENTAL DESIGN

TGFβ-mediated growth and Smad phosphorylation of MCF7, Hs578T, MDA-MB-231, and T47D human breast cancer cell lines were examined and correlated with clonogenic survival following graded radiation doses with and without pretreatment with LY364947, a small molecule inhibitor of the TGFβ type I receptor kinase. The DNA damage response was assessed in irradiated MDA-MB-231 cells pretreated with LY364947 in vitro and LY2109761, a pharmacokinetically stable inhibitor of TGFβ signaling, in vivo. The in vitro response of a syngeneic murine tumor, 4T1, was tested using a TGFβ neutralizing antibody, 1D11, with single or fractionated radiation doses in vivo.

RESULTS

Human breast cancer cell lines pretreated with TGFβ small molecule inhibitor were radiosensitized, irrespective of sensitivity to TGFβ growth inhibition. Consistent with increased clonogenic cell death, radiation-induced phosphorylation of H2AX and p53 was significantly reduced in MDA-MB-231 triple-negative breast cancer cells when pretreated in vitro or in vivo with a TGFβ type I receptor kinase inhibitor. Moreover, TGFβ neutralizing antibodies increased radiation sensitivity, blocked γH2AX foci formation, and significantly increased tumor growth delay in 4T1 murine mammary tumors in response to single and fractionated radiation exposures.

CONCLUSION

These results show that TGFβ inhibition prior to radiation attenuated DNA damage responses, increased clonogenic cell death, and promoted tumor growth delay, and thus may be an effective adjunct in cancer radiotherapy.

Invariant natural killer T cells regulate breast cancer response to radiation and CTLA-4 blockade

PURPOSE

Immunoregulatory and suppressive mechanisms represent major obstacles to the success of immunotherapy in cancer patients. We have shown that the combination of radiotherapy to the primary tumor and CTL-associated protein 4 (CTLA-4) blockade induces antitumor immunity, inhibiting metastases and extending the survival of mice bearing the poorly immunogenic and highly metastatic 4T1 mammary carcinoma. Similarly to patients with metastatic cancer, however, mice were seldom cured. Here we tested the hypothesis that invariant natural killer T (iNKT) cells, a subset with unique regulatory functions, can regulate the response to radiotherapy and CTLA-4 blockade.

EXPERIMENTAL DESIGN

The growth of 4T1 primary tumors and lung metastases was compared in wild-type and iNKT cell-deficient (iNKT-/-) mice. Treatment was started on day 13 when the primary tumors were palpable. Mice received radiotherapy to the primary tumor in two doses of 12 Gy in combination or not with 9H10 monoclonal antibody against CTLA-4. Response to treatment was assessed by measuring primary tumor growth delay/regression, survival, and number of lung metastases.

RESULTS

The response to radiotherapy plus 9H10 was markedly enhanced in the absence of iNKT cells, with 50% of iNKT-/- versus 0% of wild-type mice showing complete tumor regression, long-term survival, and resistance to a challenge with 4T1 cells. Administration of the iNKT cell activator alpha-galactosylceramide did not enhance the response of wild-type mice to radiotherapy plus 9H10. Tumor-infiltrating iNKT cells were markedly reduced in wild-type mice treated with radiotherapy plus 9H10.

CONCLUSIONS

iNKT cells play a major role in regulating the response to treatment with local radiotherapy and CTLA-4 blockade.

MERCURY-INDUCED ACCELERATION OF SPONTANEOUS AUTOIMMUNITY IN PRE-NEPHRITIC (NZBxSWR)F1 (SNF1) FEMALE MICE (B90)

Mercury exposure in susceptible mice has been known to induce autoimmunity, including the proliferation of autoantibodies, Th2-dominated antibody responses and immune complex disease. We investigated whether the immunostimulating effects of mercury can accelerate the induction of autoimmunity in SNF1 mice, a model that closely resembles human SLE nephritis. Previous studies from our laboratory have shown that dysregulation of the idiotypic network is key in the development of renal immune complex deposits in SNF1 females. In this study, six week-old pre-nephritic SNF1 females were exposed to 10 mg/L of either mercuric chloride or methylmercury in drinking water and examined for modulations in pathogenic immunophenotypes, autoantibody titers and clinical evidence of disease. We found increased populations of splenic T-cells and B-cells reactive with a pathogenic idiotypic determinant (IdLNF1) in mice exposed to mercury which, interestingly, also showed reductions in the percentage and absolute numbers of regulatory phenotypes (CD4+CD25+GITR+). Splenic lymphocytes from exposed mice showed increased proliferative responses to IdLNF1. LPS-induced proliferation was also increased in exposed mice, regardless of mercurial species used. We found modulations in serum antibody levels, including increased titers of anti-double stranded DNA autoantibodies. Clinically, mice exposed to mercury showed increased proteinuria and are currently being evaluated for glomerular damage and nephritis. The results of this study support the hypothesis that low-level exposure to metal xenobiotics such as mercury may trigger or accelerate autoimmune disease especially in a background of genetic susceptibility.