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Supplemental Fig.S3. In pancreatic cancer cells, ch9F7-F11-Emb is a negative allosteric modulator of NRG1-mediated signaling. The low-fucose non-NRG1 competing allosteric anti-HER3 antibody ch9F7-F11-Emb inhibits in a dose-dependent manner NRG1-mediated cell signaling more efficiently than the ligand-competing H4B-121-Emb antibody. BxPC3 cells were pre-stimulated with 1nM NRG1 for 5min, before adding antibodies at various concentrations for another 25min. After cell lysis, the expression levels of total and phosphorylated HER3 (Tyr1289, Tyr1197 and Tyr1222), and total and phosphorylated AKT (Ser473) were measured by western blotting (A) using the appropriate antibodies. Phosphorylation was then pixel-quantified with Image J (B) and shown relative to the maximal phosphorylation (100%) evaluated in NRG1-stimulated cells without antibody treatment (M). Results are the mean {plus minus} SD of three independent experiments

Supplementary Figure 1. AXL, MER and TYRO-3 expression in Triple Negative Breast Cancer (TNBC) cell lines and PDXs by Western blot analysis. Supplementary Figure 2. AXL mRNA expression in a large dataset of breast cancer tumors. Supplementary Figure 3. The 100 genes most correlated with AXL expression in 254 basal-like breast cancers. Supplementary Figure 4. Effect of the anti-AXL monoclonal antibody 20G7-D9 on matrix degradation by breast cancer cell lines. Supplementary Figure 5. GAS6 regulates expression of EMT markers in TNBC - Western Blot quantifications. Supplementary Figure 6. E-cadherin expression in TNBC cell lines

Suppl.Table 1: Analysis of the cellular localization, pathways and gene expression modification of the 100 genes most correlated with AXL expression in 254 basal-like breast cancers.

Purpose: AXL receptor tyrosine kinase has been described as a relevant molecular marker and a key player in invasiveness, especially in triple-negative breast cancer (TNBC).Experimental Design: We evaluate the antitumor efficacy of the anti-AXL monoclonal antibody 20G7-D9 in several TNBC cell xenografts or patient-derived xenograft (PDX) models and decipher the underlying mechanisms. In a dataset of 254 basal-like breast cancer samples, genes correlated with AXL expression are enriched in EMT, migration, and invasion signaling pathways.Results: Treatment with 20G7-D9 inhibited tumor growth and bone metastasis formation in AXL-positive TNBC cell xenografts or PDX, but not in AXL-negative PDX, highlighting AXL role in cancer growth and invasion. In vitro stimulation of AXL-positive cancer cells by its ligand GAS6 induced the expression of several EMT-associated genes (SNAIL, SLUG, and VIM) through an intracellular signaling implicating the transcription factor FRA-1, important in cell invasion and plasticity, and increased their migration/invasion capacity. 20G7-D9 induced AXL degradation and inhibited all AXL/GAS6–dependent cell signaling implicated in EMT and in cell migration/invasion.Conclusions: The anti-AXL antibody 20G7-D9 represents a promising therapeutic strategy in TNBC with mesenchymal features by inhibiting AXL-dependent EMT, tumor growth, and metastasis formation. Clin Cancer Res; 23(11); 2806–16. ©2016 AACR.

Background: The survival rate for patients with Pancreatic Ductal Adenocarcinoma (PDAC) is dramatically poor with a five-year survival rate less than 10%. The research of new treatments, which could complement the current therapeutic arsenal constituted by Gemcitabine, FOLFIRINOX (fluorouracile, leucovorin, irinotecan, oxaliplatin) and nab-paclitaxel, is a major challenge. Imiqualines are new original small heterocyclic chemical molecules based on the quinoxalinic moiety. Among these first in class compounds, the lead EAPB02303 (1) displays outstanding nanomolar activities comparable to those of the current best anticancer agents on a panel of human cancer cell lines, notably on poorly sensitive cancer like PDAC and melanoma. We tested here if EAPB02303 could be an attractive first in class molecule in PDAC and we conducted in-deep molecular characterization and bioinformatics studies to decipher its mechanism of action. Methods: We characterized EAPB02303 effect on tumor growth in-vitro by conducting sulforhodamine B assay on a panel of PDAC cells including cells derived from PDX (Patient Derived Xenograft) and 3D models with Cancer Associated Fibroblasts. We assessed in-vivo activity on subcutaneous PDAC xenografts mouse models. We then studied EAPB02303 effect on cell cycle, apoptosis and microtubule polymerisation by flow cytometry and immunofluorescence. We analyzed mRNAseq and Reverse Phase Protein Assay (RPPA) data of PDAC cell lines treated with EAPB02303 at multiple time points and concentrations to identify signaling pathways and key proteins implicated in EAPB02303 effect. We performed differential gene expression and gene set enrichment analysis by using EdgeR, Deseq2 and fgsea packages. We also used PharmacoGx package to seek for similar transcriptomic profiles among the CMAP perturbational database. Results: We showed that EAPB02303 exerts activity at low nanomolar concentrations in-vitro in PDAC cell lines and 3D models, and is able to reduce tumor growth in our xenografts in-vivo mouse models. We also found a potent synergy with Paclitaxel at lower concentrations of both compounds. Furthermore, we found that EAPB02303 induces mitosis arrest and impairment of spindle assembly after 24h treatment. Cells also underwent apoptosis after 48h treatment. mRNAseq and RPPA data showed activation of several signaling pathways including MAPK kinases. CMAP database mining revealed a high connectivity score of transcriptomic signatures between EAPB02303 and inhibitors of microtubule polymerization. All these data suggest that EAPB02303 is a new microtubule-disrupting agent with in-vivo activity in PDAC and in-vitro synergy with Paclitaxel, showing potential for future clinical investigations. (1) Imidazo[1,2a]quinoxalines and derivatives thereof for treating cancers. WO 2009 043934A1. Deleuze-Masqeufa C. et al. Citation Format: Kevin Bigot, Véronique Garambois, Nadia Vie, Marine Bruciamacchie, Pierre-Emmanuel Colombo, Diego Tosi, Cindy Patinote, Yann Maggipinto, Pierre-Antoine Bonnet, Céline Gongora, Carine Deleuze-Masquefa, Christel Larbouret. Imiqualines for pancreatic cancer: first-in-class potent and synergistic inhibitors of microtubule polymerisation. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5729.

International audience; Monoclonal antibodies have revolutionized the treatment of many diseases, but their clinical effectiveness remains limited in some cases. Associations of antibodies binding to the same target (homo-combination) or to several different targets (hetero-combination), thereby mimicking a polyclonal humoral immune response, have demonstrated a therapeutic improvement in pre-clinical and clinical trials, mainly in the field of oncology and infectious diseases. The combinations increase the efficacy of the biological responses and override resistance mechanisms observed with antibody monotherapy. The most common method of formulating and administering antibody combinations is a separate formulation, with sequential injection of each antibody as individual drug substance. Alternatively, combined formulations are developed where the separately-produced antibodies are mixed before administration or produced simultaneously by a single cell line, or a mixture of cell lines as a polyclonal master cell bank. The regulation, the toxicity and the injection sequence of these oligoclonal antibody-based mixtures remain points to be clarified and optimized for a better therapeutic effect.; Les anticorps monoclonaux ont révolutionné le traitement de nombreuses maladies mais leur efficacité clinique reste limitée dans certains cas. Des associations d'anticorps se liant à une même cible (homo-combinaisons) ou à plusieurs cibles différentes (hétéro-combinaisons), mimant ainsi une réponse immunitaire humorale polyclonale, ont conduit à une amélioration thérapeutique dans des essais précliniques et cliniques, essentiellement en cancérologie et en infectiologie. Ces combinaisons augmentent l'efficacité des réponses biologiques et court-circuitent les mécanismes de résistances observés lors d'une monothérapie par anticorps. Le procédé de formulation et d'administration des combinaisons d'anticorps le plus fréquent est une formulation séparée, avec injection séquentielle de chaque anticorps « principe actif ». Alternativement, se développent des formulations combinées, où les anticorps produits séparément sont mélangés avant administration, ou produits simultanément par une lignée cellulaire unique ou un mélange de lignées cellulaires correspondant à une master-bank 2 cellulaire polyclonale. La réglementation, la toxicité et la séquence d'injection des mélanges oligoclonaux restent des points à éclaircir et à optimiser pour un meilleur effet thérapeutique.

Simple Summary The approval of the two antibody combinations trastuzumab/pertuzumab and ipilimumab/nivolumab in oncology has paved the way for novel antibody combinations or oligoclonal antibody mixtures to improve their efficacy in cancer. The underlying biological mechanisms and challenges of these strategies will be discussed using data from clinical trials listed in databases. These therapeutic combinations also lead to questions on how to optimize their formulation and delivery to induce a therapeutic polyclonal response in patients with cancer. Abstract Monoclonal antibodies have revolutionized the treatment of many diseases, but their clinical efficacy remains limited in some other cases. Pre-clinical and clinical trials have shown that combinations of antibodies that bind to the same target (homo-combinations) or to different targets (hetero-combinations) to mimic the polyclonal humoral immune response improve their therapeutic effects in cancer. The approval of the trastuzumab/pertuzumab combination for breast cancer and then of the ipilimumab/nivolumab combination for melanoma opened the way to novel antibody combinations or oligoclonal antibody mixtures as more effective biologics for cancer management. We found more than 300 phase II/III clinical trials on antibody combinations, with/without chemotherapy, radiotherapy, small molecules or vaccines, in the ClinicalTrials.gov database. Such combinations enhance the biological responses and bypass the resistance mechanisms observed with antibody monotherapy. Usually, such antibody combinations are administered sequentially as separate formulations. Combined formulations have also been developed in which separately produced antibodies are mixed before administration or are produced simultaneously in a single cell line or a single batch of different cell lines as a polyclonal master cell bank. The regulation, toxicity and injection sequence of these oligoclonal antibody mixtures still need to be addressed in order to optimize their delivery and their therapeutic effects.

Pancreatic Ductal Adenocarcinoma (PDAC) is an extremely aggressive disease.There is a clear need of new strategies and new researches to treat and diagnose these patients. Regarding treatments, surgery is possible in only 20% of cases, and the chemotherapeutic molecule Gemcitabine is unfortunately lacking a good response rate. Recently, a new polychemotherapy oxaliplatin-based (FOLFIRINOX), which is a combination of 4 drugs: oxaliplatin, irinotecan, fluorouracil and leucovorin, has been approved. It has showed a significant increase of the overall survival inpatients compared to gemcitabine, but associated with more toxicity and still limited efficiency. Most of the drugs induce their toxicity by provoking DNA damages and replication stress, leading to the activation of DNA repair pathways. In this context,our research project proposes to find a synergistic association of FOLFIRINOX with specific inhibitors of DNA damage repair -Ataxia Telangiectasia and Rad3 related inhibitor (ATRi)- to increase the efficiency of the chemotherapy while reducing itstoxicity. The resistance to chemotherapy can come from the stroma that represents up to 80% of the tumor mass. The impact of the chemotherapies on the microenvironment can be a key to increase the treatments efficiency. That’s why in this project, we studied co-culture models to look at the effect of this new polychemotherapy on tumor cells and its microenvironment, in particular Cancer-Associated Fibroblasts (CAFs). Viability matrix in 2D & 3D in vitro co-culture of tumor cells with primary CAFs were carried out. DNA damage and proteins from the DNA damage repair pathways were analysed after treatments. Cell death and autophagy pathways were studied. In vivo, immunodeficient mice xenografted with ATCC and Patient Derived Xenograft models were treated with FOLFIRINOX and ATRi to evaluate the effect on tumor progression. A synergistic effect of the association was demonstrated in vitro independently of the KRAS, ATM, TP53, BRCA1/2 mutation statuts in several pancreatic models (ATCC and derived from PDX) and in co-culture with CAFs. A higher apoptosis and DNA damages were observed in tumor cells treated with the associated drugs. These results were associated with a decrease of DNA damage repair pathways leading to more apoptosis compared to the chemotherapy alone and an inhibition of the autophagy flux. Also, a phenotypic change in the cells was found after treating with ATRi and with an increase of this particular phenotype when the chemotherapy was added. A protective effect of the CAFs on tumor cells was observed and CAF secretome was analysed. In vivo, the association inhibits significantly the tumor growth compared to each treatment alone and no toxicity was observed. Now, validation of this polychemotherapy in vivo using co-culture models in immunodeficient and immunocompetent mice are crucial to confirm the therapeutic potential of this new treatment for PDAC. Citation Format: Marine Bruciamacchie, Nadia Vie, Véronique Garambois, Diego Tosi, Pierre-Emmanuel Colombo, Céline Gongora, Christel Larbouret. Effect of folfirinox with an ATR inhibitor on pancreatic tumor cells and its microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2589.

Human epidermal growth factor receptor 4 (HER4) isoforms have oncogenic or tumor suppressor functions depending on their susceptibility to proteolytic cleavage and HER4 intracellular domain (4ICD) translocation. Here, we report that the neuregulin 1 (NRG1) tumor suppressor mechanism through the HER4 JMa/CYT1 isoform can be mimicked by the agonist anti‐HER4 Ab C6. Neuregulin 1 induced cleavage of poly(ADP‐ribose) polymerase (PARP) and sub‐G1 DNA fragmentation, and also reduced the metabolic activity of HER3−/HER4+ cervical (C‐33A) and ovarian (COV318) cancer cells. This effect was confirmed in HER4 JMa/CYT1‐, but not JMa/CYT2‐transfected BT549 triple‐negative breast cancer cells. Neuregulin 1 favored 4ICD cleavage and retention in mitochondria in JMa/CYT1‐transfected BT549 cells, leading to reactive oxygen species (ROS) production through mitochondrial depolarization. Similarly, the anti‐HER4 Ab C6, which binds to a conformational epitope located on a.a. 575‐592 and 605‐620 of HER4 domain IV, induced 4ICD cleavage and retention in mitochondria, and mimicked NRG1‐mediated effects on PARP cleavage, ROS production, and mitochondrial membrane depolarization in cancer cells. In vivo, C6 reduced growth of COV434 and HCC1187 tumor cell xenografts in nude mice. Biasing 4ICD trafficking to mitochondria with anti‐HER4 Abs to mimic NRG1 suppressor functions could be an alternative anticancer strategy., Neuregulin 1 (NRG1) induced cleavage of poly(ADP‐ribose) polymerase (PARP) in human epidermal growth factor receptor 4 (HER4) JMa/CYT1‐expressing cancer cells. NRG1 favored HER4 intracellular domain (4ICD) cleavage and retention into mitochondria leading to reactive oxygen species (ROS) production through mitochondrial depolarization in HER4 JMa/CYT1‐expressing cancer cells. Phage‐displayed selected anti‐HER4 Ab C6 induced 4ICD cleavage and retention into mitochondria, mimicking NRG1‐mediated effects on PARP cleavage, ROS production, and mitochondrial membrane depolarization. C6 Ab reduced in vivo growth of ovarian COV434 and breast HCC1187 tumor cell xenografts in nude mice.

Monoclonal antibodies have revolutionized the treatment of many diseases, but their clinical effectiveness remains limited in some cases. Associations of antibodies binding to the same target (homo-combination) or to several different targets (hetero-combination), thereby mimicking a polyclonal humoral immune response, have demonstrated a therapeutic improvement in pre-clinical and clinical trials, mainly in the field of oncology and infectious diseases. The combinations increase the efficacy of the biological responses and override resistance mechanisms observed with antibody monotherapy. The most common method of formulating and administering antibody combinations is a separate formulation, with sequential injection of each antibody as individual drug substance. Alternatively, combined formulations are developed where the separately-produced antibodies are mixed before administration or produced simultaneously by a single cell line, or a mixture of cell lines as a polyclonal master cell bank. The regulation, the toxicity and the injection sequence of these oligoclonal antibody-based mixtures remain points to be clarified and optimized for a better therapeutic effect.Imiter la réponse immunitaire humorale polyclonale - De l’association de deux anticorps monoclonaux aux productions oligoclonales.Les anticorps monoclonaux ont révolutionné le traitement de nombreuses maladies mais leur efficacité clinique reste limitée dans certains cas. Des associations d’anticorps se liant à une même cible (homo-combinaisons) ou à plusieurs cibles différentes (hétéro-combinaisons), mimant ainsi une réponse immunitaire humorale polyclonale, ont conduit à une amélioration thérapeutique dans des essais précliniques et cliniques, essentiellement en cancérologie et en infectiologie. Ces combinaisons augmentent l’efficacité des réponses biologiques et court-circuitent les mécanismes de résistances observés lors d’une monothérapie par anticorps. Le procédé de formulation et d’administration des combinaisons d’anticorps le plus fréquent est une formulation séparée, avec injection séquentielle de chaque anticorps « principe actif ». Alternativement, se développent des formulations combinées, où les anticorps produits séparément sont mélangés avant administration, ou produits simultanément par une lignée cellulaire unique ou un mélange de lignées cellulaires correspondant à une master-bank cellulaire polyclonale. La réglementation, la toxicité et la séquence d’injection des mélanges oligoclonaux restent des points à éclaircir et à optimiser pour un meilleur effet thérapeutique.

Herein we describe the synthesis and evaluation of four novel HER2-targeting, cathepsin B-sensitive antibody-drug conjugates bearing a monomethylauristatin E (MMAE) cytotoxic payload, constructed via the conjugation of cleavable linkers to trastuzumab using a site-specific bioconjugation methodology. These linkers vary by both cleavable trigger motif and hydrophilicity, containing one of two cathepsin B sensitive dipeptides (Val-Cit and Val-Ala), and engendered with either hydrophilic or hydrophobic character via application of a PEG12 spacer. Through evaluation of physical properties, in vitro cytotoxicity, and receptor affinity of the resulting antibody-drug conjugates (ADCs), we have demonstrated that while both dipeptide triggers are effective, the increased hydrophobicity of the Val-Ala pair limits its utility within this type of linker. In addition, while PEGylation augments linker hydrophilicity, this change does not translate to more favourable ADC hydrophilicity or potency. While all described structures demonstrated excellent and similar in vitro cytotoxicity, the ADC with the ValCitPABMMAE linker shows the most promising combination of in vitro potency, structural homogeneity, and hydrophilicity, warranting further evaluation into its therapeutic potential.

International audience; Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer characterized by poor response to chemo- and radiotherapy due to the lack of efficient therapeutic tools and early diagnostic markers. We previously generated the non-ligand competing anti-HER3 antibody 9F7-F11 that binds to pancreatic tumor cells and induces tumor regression in vivo in experimental models. Here, we asked whether coupling 9F7-F11 with a radiosensitizer, such as monomethylauristatin E (MMAE), by using the antibody-drug conjugate (ADC) technology could improve radiation therapy efficacy in PDAC. We found that the MMAE-based HER3 antibody-drug conjugate (HER3-ADC) was efficiently internalized in tumor cells, increased the fraction of cells arrested in G2/M, which is the most radiosensitive phase of the cell cycle, and promoted programmed cell death of irradiated HER3-positive pancreatic cancer cells (BxPC3 and HPAC cell lines). HER3-ADC decreased the clonogenic survival of irradiated cells by increasing DNA double-strand break formation (based on γH2AX level), and by modulating DNA damage repair. Tumor radiosensitization with HER3-ADC favored the inhibition of the AKT-induced survival pathway, together with more efficient caspase 3/PARP-mediated apoptosis. Incubation with HER3-ADC before irradiation synergistically reduced the phosphorylation of STAT3, which is involved in chemoradiation resistance. In vivo, the combination of HER3-ADC with radiation therapy increased the overall survival of mice harboring BxPC3, HPAC cell xenografts or patient-derived xenografts, and reduced proliferation (KI67-positive cells). Combining auristatin radiosensitizer delivery via an HER3-ADC with radiotherapy is a new promising therapeutic strategy in PDAC. This article is protected by copyright. All rights reserved.

International audience; We characterized the mechanism of action of the neuregulin-non-competitive anti-HER3 therapeutic antibody 9F7-F11 that blocks the PI3K/AKT pathway, leading to cell cycle arrest and apoptosis in vitro and regression of pancreatic and breast cancer in vivo. We found that 9F7-F11 induces rapid HER3 down-regulation. Specifically, 9F7-F11-induced HER3 ubiquitination and degradation in pancreatic, breast and prostate cancer cell lines was driven mainly by the itchy E3 ubiquitin ligase (ITCH/AIP4). Overexpression of the ITCH/AIP4 inhibitor N4BP1 or small-interfering RNA-mediated knockdown of ITCH/AIP4 inhibited HER3 ubiquitination/degradation and PI3K/AKT signaling blockade induced by 9F7-F11. Moreover, 9F7-F11-mediated JNK1/2 phosphorylation led to ITCH/AIP4 activation and recruitment to HER3 for receptor ubiquitination and degradation. ITCH/AIP4 activity was activated by the deubiquitinases USP8 and USP9X, as demonstrated by RNA interference. Taken together, our results suggest that 9F7-F11-induced HER3 ubiquitination and degradation in cancer cells mainly occurs through JNK1/2-dependent ITCH/AIP4 activation.

Background The irinotecan-induced phosphokinome changes in colorectal cancer (CRC) cells were used to guide the selection of targeted agents to be tested in combination with irinotecan. Methods Phosphokinome profiling with peptide arrays of tumour samples from nude mice xenografted with HT29 cells and treated or not with an effective dose of irinotecan was used to identify signalling pathways activated by irinotecan treatment. Then, drugs targeting these pathways were combined in vitro with irinotecan to test potential synergistic effect. The interactions between these drug combinations were assessed by a dose matrix approach. Confirmation of the most potential combination has been confirmed in vivo in xenografted mice. Results Irinotecan induced in vivo the activation of AKT and MEK1 phosphorylation. The dose matrix approach showed that BKM120 (PI3K inhibitor) and MEK162 (MEK inhibitor) are synergistic in vitro and in vivo with a cytostatic and cytotoxic effect, while combination of BKM120 and irinotecan or MEK162 and irinotecan are only additive or even antagonistic. However, the triple combination of SN38, BKM120 and MEK162 showed a better synergistic effect that BKM120 and MEK162, indicating that the cells need to inhibit both AKT and ERK pathways to become more sensitive to irinotecan-based chemotherapies. Conclusion Analysis of chemotherapy-induced phosphokinome changes helps to elucidate the mechanisms of drug resistance and to guide the selection of targets for combination therapies with synergistic activity. Electronic supplementary material The online version of this article (10.1186/s12885-018-4712-z) contains supplementary material, which is available to authorized users.

International audience; Neuregulin 1 (NRG1), a ligand for HER3 and HER4 receptors, is secreted by both pancreatic tumor cells (PC) and cancer-associated fibroblasts (CAFs), the latter representing the most abundant compound of pancreatic stroma. This desmoplastic stroma contributes to Pancreatic Ductal Adenocarcinoma (PDAC) aggressiveness and therapeutic failure by promoting tumor progression, invasion and resistance to chemotherapies. In the present work, we aimed at disrupting the complex crosstalk between PC and CAF in order to prevent tumor cell proliferation. To do so, we demonstrated the promising tumor growth inhibitory effect of the 7E3, an original antibody directed to NRG1. This antibody promotes antibody dependent cellular cytotoxicity in NRG1-positive PC and CAFs and inhibits NRG1-associated signaling pathway induction, by blocking NRG1-mediated HER3 activation. Moreover, 7E3 inhibits migration and growth of pancreatic cancer cells co-cultured with CAFs, both in vitro and in vivo using orthotopic pancreatic tumor xenografts. Our preclinical results demonstrate that the anti-NRG1 antibody 7E3 could represent a promising approach to target pancreatic stroma and cancer cells, thereby providing novel therapeutic options for PDAC.

Exploratory clinical trials using therapeutic anti-HER3 antibodies strongly suggest that neuregulin (NRG1; HER3 ligand) expression at tumor sites is a predictive biomarker of anti-HER3 antibody efficacy in cancer. We hypothesized that in NRG1-expressing tumors, where the ligand is present before antibody treatment, anti-HER3 antibodies that do not compete with NRG1 for receptor binding have a higher receptor-neutralizing action than antibodies competing with the ligand for binding to HER3. Using time-resolved–fluorescence energy transfer (TR-FRET), we demonstrated that in the presence of recombinant NRG1, binding of 9F7-F11 (a nonligand-competing anti-HER3 antibody) to HER3 is increased, whereas that of ligand-competing anti-HER3 antibodies (H4B-121, U3-1287, Ab#6, Mab205.10.2, and MOR09825) is decreased. Moreover, 9F7-F11 showed higher efficacy than antibodies that compete with the ligand for binding to HER3. Specifically, 9F7-F11 inhibition of cell proliferation and of HER3/AKT/ERK1/2 phosphorylation as well as 9F7-F11–dependent cell-mediated cytotoxicity were higher in cancer cells preincubated with recombinant NRG1 compared with cells directly exposed to the anti-HER3 antibody. This translated in vivo into enhanced growth inhibition of NRG1-expressing BxPC3 pancreatic, A549 lung, and HCC-1806 breast cell tumor xenografts in mice treated with 9F7-F11 compared with H4B-121. Conversely, both antibodies had similar antitumor effect in NRG1-negative HPAC pancreatic carcinoma cells. In conclusion, the allosteric modulator 9F7-F11 shows increased anticancer effectiveness in the presence of NRG1 and thus represents a novel treatment strategy for NRG1-addicted tumors. Mol Cancer Ther; 16(7); 1312–23. ©2017 AACR.

Purpose: AXL receptor tyrosine kinase has been described as a relevant molecular marker and a key player in invasiveness, especially in triple-negative breast cancer (TNBC). Experimental Design: We evaluate the antitumor efficacy of the anti-AXL monoclonal antibody 20G7-D9 in several TNBC cell xenografts or patient-derived xenograft (PDX) models and decipher the underlying mechanisms. In a dataset of 254 basal-like breast cancer samples, genes correlated with AXL expression are enriched in EMT, migration, and invasion signaling pathways. Results: Treatment with 20G7-D9 inhibited tumor growth and bone metastasis formation in AXL-positive TNBC cell xenografts or PDX, but not in AXL-negative PDX, highlighting AXL role in cancer growth and invasion. In vitro stimulation of AXL-positive cancer cells by its ligand GAS6 induced the expression of several EMT-associated genes (SNAIL, SLUG, and VIM) through an intracellular signaling implicating the transcription factor FRA-1, important in cell invasion and plasticity, and increased their migration/invasion capacity. 20G7-D9 induced AXL degradation and inhibited all AXL/GAS6–dependent cell signaling implicated in EMT and in cell migration/invasion. Conclusions: The anti-AXL antibody 20G7-D9 represents a promising therapeutic strategy in TNBC with mesenchymal features by inhibiting AXL-dependent EMT, tumor growth, and metastasis formation. Clin Cancer Res; 23(11); 2806–16. ©2016 AACR.

BACKGROUND: Cetuximab, a monoclonal antibody against EGFR used for the treatment of colorectal cancer (CRC), is ineffective in many patients. The aim of this study was to identify the signalling pathways activated by cetuximab in CRC cells and define new biomarker of response. METHODS: We used in vitro, in vivo models and clinical CRC samples to assess the role of p38 and FOXO3a in cetuximab mechanism of action. RESULTS: We show that cetuximab activates the MAPK p38. Specifically, p38 inhibition reduced cetuximab efficacy on cell growth and cell death. At the molecular level, cetuximab activates the transcription factor FOXO3a and promotes its nuclear translocation via p38-mediated phosphorylation, leading to the upregulation of its target genes p27 and BIM and the subsequent induction of apoptosis and inhibition of cell proliferation. Finally, we found that high FOXO3a and p38 expression levels are associated with better response rate and improved outcome in cetuximab-treated patients with CRC harbouring WT KRAS. CONCLUSIONS: We identify FOXO3a as a key mediator of cetuximab mechanism of action in CRC cells and define p38 as its activator in this context. Moreover, high FOXO3a and p38 expression could predict the response to cetuximab in patients with CRC harbouring WT KRAS.British Journal of Cancer advance online publication, 29 September 2016; doi:10.1038/bjc.2016.313 www.bjcancer.com.

Toll-like receptors are ubiquitous and very well conserved throughout evolution, with important functions mediating innate and adaptative immunological mechanisms. The importance of these receptors and their agonists has been recently pointed out in immunology and cancerology, although the accurate underlying mechanisms are still under investigation. The association of agonists of these receptors with ionizing radiation has been studied in preclinical experiments with promising results. Part of these compounds is flagellin, which seems to be able to modulate the radiosensitivity of both tumors and healthy tissues.

In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal antibodies (mAbs) is an efficient therapeutic strategy but the underlying mechanisms are not fully understood. Here, we describe a time-resolved fluorescence resonance energy transfer (TR-FRET) method to quantify EGFR/HER2 heterodimers on cell surface to shed some light on the mechanism of such therapies. First, we tested this antibody-based TR-FRET assay in NIH/3T3 cell lines that express EGFR and/or HER2 and in various tumor cell lines. Then, we used the antibody-based TR-FRET assay to evaluate in vitro the effect of different targeted therapies on EGFR/HER2 heterodimers in the ovarian carcinoma cell line SKOV-3. A simultaneous incubation with Cetuximab (anti-EGFR) and Trastuzumab (anti-HER2) disturbed EGFR/HER2 heterodimers resulting in a 72% reduction. Cetuximab, Trastuzumab or Pertuzumab (anti-HER2) alone induced a 48, 44, or 24% reduction, respectively. In contrast, the tyrosine kinase inhibitors Erlotinib and Lapatinib had very little effect on EGFR/HER2 dimers concentration. In vivo, the combination of Cetuximab and Trastuzumab showed a better therapeutic effect (median survival and percentage of tumor-free mice) than the single mAbs. These results suggest a correlation between the extent of the mAb-induced EGFR/HER2 heterodimer reduction and the efficacy of such mAbs in targeted therapies. In conclusion, quantifying EGFR/HER2 heterodimers using our antibody-based TR-FRET assay may represent a useful method to predict the efficacy and explain the mechanisms of action of therapeutic mAbs, in addition to other commonly used techniques that focus on antibody-dependent cellular cytotoxicity, phosphorylation, and cell proliferation.

The symposium on Antibodies as Drugs, organized by Keystone Symposia and chaired by J. Marks, (University of California Los Angeles, USA), E.S. Ward (University of Texas Southwestern Medical Center, USA) and L. Weiner (Georgetown University Medical Center, USA), was held in Whistler, British Columbia. This Canadian Rockies village, which will host the 2010 Olympic Games, served as an enchanting backdrop to the meeting. The >350 speakers and attendees included scientists from major pharmaceutical firms, e.g., Abbott, MedImmune/Astra Zeneca, Bristol-Myers Squibb, Merck & Co, Pfizer, Sanofi-Aventis, Schering, GlaxoSmithKline, Eli Lilly, Hoffmann LaRoche, Novartis, Wyeth, and biotechnology companies, e.g., Ablynx, Medarex, Morphosys, GenMab, Amgen, Genentech, ImmunoGen, Agensys, Domantis, Biogen Idec, Centocor, LFB, Micromet, PDL Biopharma, Borean Pharma, Dyax Corp, Symphogen, Syntonix. Academic research groups at Imperial College London, University of Oxford, ETH Zurich, Scripps, Institute Cochin, Karolinsk...

International audience; The human EGF receptor (HER/EGFR) family of receptor tyrosine kinases serves as a key target for cancer therapy. Specifically, EGFR and HER2 have been repeatedly targeted because of their genetic aberrations in tumors. The therapeutic potential of targeting HER3 has long been underestimated, due to relatively low expression in tumors and impaired kinase activity. Nevertheless, in addition to serving as a dimerization partner of EGFR and HER2, HER3 acts as a key player in tumor cells' ability to acquire resistance to cancer drugs. In this study, we generated several monoclonal antibodies to HER3. Comparisons of their ability to degrade HER3, decrease downstream signaling, and inhibit growth of cultured cells, as well as recruit immune effector cells, selected an antibody that later emerged as the most potent inhibitor of pancreatic cancer cells grown as tumors in animals. Our data predict that anti-HER3 antibodies able to intercept autocrine and stroma-tumor interactions might strongly inhibit tumor growth, in analogy to the mechanism of action of anti-EGFR antibodies routinely used now to treat colorectal cancer patients.

Tumor necrosis factor-alpha (TNF-alpha) enhances X-ray killing of human tumor cells in vitro and enhances tumor control when combined with radiotherapy (RT) in animal tumor models. In multiple Phase I studies, intravenous injection of TNF-alpha appeared to have severe systemic side effects. To overcome these limitations, we used a bispecific antibody (BAb) directed against carcinoembryonic antigen and human TNF-alpha to target this cytokine in human digestive carcinoma treated with simultaneous RT. We used human digestive carcinoma cell lines (colon cancer, LS174T, and pancreatic cancer, BxPC-3) to determine the interaction of TNF-alpha and RT on clonogenic cytotoxicity. Isobolograms were established to confirm additive or supra-additive effects between both treatments. LS174T and BxPC-3 cells were grafted subcutaneously at Day 0 into female nude mice (7-8 weeks old). When the tumors reached a volume of about 80 mm(3), the mice were randomly assigned to treatment: Group 1, normal saline i.v. injection (control group); Group 2, TNF-alpha at 1 microg/i.v. injection; Group 3, BAb at 25 microg/i.v. injection; Group 4, BAb plus TNF-alpha (ratio 25 microg to 1 microg) i.v. injection; Group 5, local RT plus normal saline (0.5 Gy. min(-1)) at a total dose of 30 Gy delivered in five fractions; Group 6, local RT plus TNF-alpha injections 3 h before RT; Group 7, local RT plus BAb plus TNF-alpha co-injected 24 h before RT. Tumor growth delay was used as the end point for all groups. In the LS174T experiments, TNF-alpha added 12 h before RT showed a statistically significant decrease in the survival fraction at 2 Gy compared with RT alone (0.23 vs. 0.42 Gy, p = 0.0017). These results were largely confirmed with the BxPC-3 cell lines (0.29 vs. 0.72, p0.00001). Isobolograms confirmed the additivity between TNF-alpha and RT in both cell lines. At 50% survival, the data points were within the envelope of additivity. In the LS174T and BxPC-3 xenografts, RT as a single agent (Group 5) slowed tumor progression compared with Group 1 (p0.027 and p = 0.00001, respectively). TNF-alpha alone, BAb alone, or BAb plus TNF-alpha (Groups 2, 3, and 4) had no effect. In the LS174T model, TNF-alpha plus RT enhanced the delay to reach 2000 mm(3) compared with RT alone but without statistical significance. This delay was significantly longer when BAb was added (p = 0.0033, for Group 6 vs. Group 7). In the BxPC-3 experiments, the median delay to reach 2000 mm(3) was similar between the RT and TNF-alpha plus RT groups (93 days). The use of our BAb in combination with TNF-alpha and RT dramatically enhanced this median delay (177 days, p = 0.0013). No body weight loss was observed in any group. Our data could be used as a solid preclinical rationale on which to base a clinical study of locally advanced pancreatic or rectal cancers in the near future.

The aim of this study was to treat carcinoembryonic antigen (CEA)-expressing pancreatic carcinoma cells with tumour necrosis factor alpha (TNFalpha) and simultaneous radiation therapy (RT), using a bispecific antibody (BAb) anti-TNFalpha/anti-CEA. TNFalpha used alone produced a dose-dependent inhibition of the clonogenic capacity of the cultured cells. Flow cytometry analysis of cell cycle progression confirmed the accumulation of cells in G(1) phase after exposure to TNFalpha. When TNFalpha was added 12 h before RT, the surviving fraction at 2 Gy was 60% lower than that obtained with irradiation alone (0.29 vs 0.73, respectively, P0.00001). In combination treatment, cell cycle analysis demonstrated that TNFalpha reduced the number of cells in radiation-induced G(2) arrest, blocked irreversibly the cells in G(1) phase, and showed an additive decrease of the number of cells in S phase. In mice, RT as a single agent slowed tumour progression as compared with the control group (P0.00001). BAb+TNFalpha+RT combination enhanced the delay for the tumour to reach 1500 mm(3) as compared with RT alone or with RT+TNFalpha (P=0.0011). Median delays were 90, 93, and 142 days for RT alone, RT+TNFalpha, and RT+BAb+TNFalpha groups, respectively. These results suggest that TNFalpha in combination with BAb and RT may be beneficial for the treatment of pancreatic cancer in locally advanced or adjuvant settings.

International audience; AXL receptor tyrosine kinase (RTK) is implicated in proliferation and invasion of many cancers, particularly in pancreatic ductal adenocarcinoma (PDAC), for which new therapeutic options are urgently required. We investigated whether inhibition of AXL activity by specific monoclonal antibodies (mAbs) is efficient in limiting proliferation and migration of pancreatic cancer cells. Expression of AXL was evaluated by immunohistochemistry in 42 PDAC. The AXL role in oncogenesis was studied using the short hairpin RNA approach in a pancreatic carcinoma cell line. We further generated antihuman AXL mAbs and evaluated their inhibitory effects and the AXL downstream signaling pathways first in vitro, in a panel of pancreatic cancer cell lines and then in vivo, using subcutaneous or orthotopic pancreatic tumor xenografts. AXL receptor was found expressed in 76% (32/42) of PDAC and was predominantly present in invasive cells. The AXL-knockdown Panc-1 cells decreased in vitro cell migration, survival and proliferation, and reduced in vivo tumor growth. Two selected anti-AXL mAbs (D9 and E8), which inhibited phosphorylation of AXL and of its downstream target AKT without affecting growth arrest-specific factor 6 (GAS6) binding, induced downexpression of AXL by internalization, leading to an inhibition of proliferation and migration in the four pancreatic cancer cell lines studied. In vivo, treatment by anti-AXL mAbs significantly reduced growth of both subcutaneous and orthotopic pancreatic tumor xenografts independently of their KRAS mutation status. Our in vitro and preclinical in vivo data demonstrate that anti-human AXL mAbs could represent a new approach to the pancreatic cancer immunotherapy.Oncogene advance online publication, 18 November 2013; doi:10.1038/onc.2013.487.

International audience; We previously demonstrated the synergistic therapeutic effect of the cetuximab (anti-epidermal growth factor receptor [EGFR] monoclonal antibody, mAb)-trastuzumab (anti-HER2 mAb) combination (2mAbs therapy) in HER2(low) human pancreatic carcinoma xenografts. Here, we compared the 2mAbs therapy, the erlotinib (EGFR tyrosine kinase inhibitor [TKI])-trastuzumab combination and lapatinib alone (dual HER2/EGFR TKI) and explored their possible mechanisms of action. The effects on tumor growth and animal survival of the three therapies were assessed in nude mice xenografted with the human pancreatic carcinoma cell lines Capan-1 and BxPC-3. After therapy, EGFR and HER2 expression and AKT phosphorylation in tumor cells were analyzed by Western blot analysis. EGFR/HER2 heterodimerization was quantified in BxPC-3 cells by time-resolved FRET. In K-ras-mutated Capan-1 xenografts, the 2mAbs therapy gave significantly higher inhibition of tumor growth than the erlotinib/trastuzumab combination, whereas in BxPC-3 (wild-type K-ras) xenografts, the erlotinib/trastuzumab combination showed similar growth inhibition but fewer tumor-free mice. Lapatinib showed no antitumor effect in both types of xenografts. The efficacy of the 2mAbs therapy was partly Fc-independent because F(ab')(2) fragments of the two mAbs significantly inhibited BxPC-3 growth, although with a time-limited therapeutic effect. The 2mAbs therapy was associated with a reduction of EGFR and HER2 expression and AKT phosphorylation. BxPC-3 cells preincubated with the two mAbs showed 50% less EGFR/HER2 heterodimers than controls. In pancreatic carcinoma xenografts, the 2mAbs therapy is more effective than treatments involving dual EGFR/HER2 TKIs. The mechanism of action may involve decreased AKT phosphorylation and/or disruption of EGFR/HER2 heterodimerization.

Following the development of targeted therapies against EGFR and HER2, two members of the human epidermal receptor (HER) family of receptor tyrosine kinases, much interest has been focused on their expression in tumors. However, knowing the expression levels of individual receptors may not be sufficient to predict drug response. Here, we describe the development of antibody-based time-resolved Forster resonance energy transfer (TR-FRET) assays for the comprehensive analysis not only of EGFR and HER2 expression in tumor cryosections, but also of their activation through quantification of HER homo- or heterodimers. First, EGFR and HER2 expression levels were quantified in 18 breast tumors and the results were compared with those obtained by using reference methods. The EGFR number per cell determined by TR-FRET was significantly correlated with EGFR mRNA copy number (P

Cetuximab is a monoclonal antibody against EGFR and is associated with 5-FU and irinotecan for the treatment of patients with colorectal cancer harboring wild type KRAS. However, cetuximab is ineffective in patients with constitutively active mutated KRAS and also in half of the patients with wild type KRAS. As cetuximab downstream cellular targets are not fully characterized, the aim of this study was to identify the signaling pathways activated by cetuximab in CRC cells. Our results show that in addition to inhibiting ERK and AKT, cetuximab also activates the mitogen-activated protein kinase (MAPK) p38. We have showed that p38 inhibition reduced cetuximab efficacy on cell growth and cell death. At the molecular level, cetuximab activates the transcription factor FOXO3a and promotes its nuclear translocation via p38-mediated phosphorylation. FOXO3a phosphorylation and activation by p38 led to the up-regulation of its target genes p27 and BIM and the subsequent induction of apoptosis and inhibition of cell proliferation. Finally, FOXO3a silencing reduced cetuximab cytotoxicity, further confirming FOXO3a role in cetuximab effect. Collectively, our results identify FOXO3a as a key mediator of cetuximab mechanism of action in CRC cells KRAS WT and define p38 as its main activator in this context. Citation Format: Laetitia Marzi, Eve Combes, Nadia VIE, Diego Tosi, Adeline Ayrolles-Torro, Christel Larbouret, Vincent Denis, Laetitia K. Linares, Clara Montagut, Mar Iglesias, Pierre Martineau, Eric W-F Lam, Maguy Del Rio, Céline Gongora. Cetuximab activates Foxo3a via the MAPK p38 to induce apoptosis and reduce cell proliferation in colorectal cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B16.

In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal antibodies (mAbs) is an efficient therapeutic strategy but the underlying mechanisms are not fully understood. Here, we describe a time-resolved fluorescence resonance energy transfer (TR-FRET) method to quantify EGFR/HER2 heterodimers on cell surface to shed some light on the mechanism of such therapies. First, we tested this antibody-based TR-FRET assay in NIH/3T3 cell lines that express EGFR and/or HER2 and in various tumor cell lines. Then, we used the antibody-based TR-FRET assay to evaluate in vitro the effect of different targeted therapies on EGFR/HER2 heterodimers in the ovarian carcinoma cell line SKOV-3. A simultaneous incubation with Cetuximab (anti-EGFR) and Trastuzumab (anti-HER2) disturbed EGFR/HER2 heterodimers resulting in a 72% reduction. Cetuximab, Trastuzumab or Pertuzumab (anti-HER2) alone induced a 48, 44, or 24% reduction, respectively. In contrast, the tyrosine kinase inhibitors Erlotinib and Lapatinib had very little effect on EGFR/HER2 dimers concentration. In vivo, the combination of Cetuximab and Trastuzumab showed a better therapeutic effect (median survival and percentage of tumor-free mice) than the single mAbs. These results suggest a correlation between the extent of the mAb-induced EGFR/HER2 heterodimer reduction and the efficacy of such mAbs in targeted therapies. In conclusion, quantifying EGFR/HER2 heterodimers using our antibody-based TR-FRET assay may represent a useful method to predict the efficacy and explain the mechanisms of action of therapeutic mAbs, in addition to other commonly used techniques that focus on antibody-dependent cellular cytotoxicity, phosphorylation, and cell proliferation.

The use of cytokines as adjuvant for different forms of cancer therapy represents one of the most promising areas of applied cancer research (Seruga et al.2008). As examples, Interleukin-2 is now been a classical treatment for renal cell carcinoma (FDA approved in 1992) and always evaluated for other cancer immunotherapy, interferon α for melanoma therapy (FDA approved in 1995) and others, such as IL-15 emerged as good candidate since IL-15 was ranked 1st/124 immunomodulatory drugs in clinical and preclinical trials to treat cancer by an NCI consortium (Cheever 2008).

International audience; PURPOSE: Tumor necrosis factor-alpha (TNF-alpha) enhances radiotherapy (RT) killing of tumor cells in vitro and in vivo. To overcome systemic side effects, we used a bispecific antibody (BsAb) directed against carcinoembryonic antigen (CEA) and TNF-alpha to target this cytokine in a CEA-expressing colon carcinoma. We report the evaluation of this strategy in immunocompetent CEA-transgenic mice. METHODS AND MATERIALS: The murine CEA-transfected colon carcinoma MC-38 was used for all experiments. In vitro, clonogenic assays were performed after RT alone, TNF-alpha alone, and RT plus TNF-alpha. In vivo, the mice were randomly assigned to treatment groups: control, TNF-alpha, BsAb, BsAb plus TNF-alpha, RT, RT plus TNF-alpha, and RT plus BsAb plus TNF-alpha. Measurements of endogenous TNF-alpha mRNA levels and evaluation of necrosis (histologic evaluation) were assessed per treatment group. RESULTS: In vitro, combined RT plus TNF-alpha resulted in a significant decrease in the survival fraction at 2 Gy compared with RT alone (p < 0.00001). In vivo, we observed a complete response in 5 (50%) of 10, 2 (20%) of 10, 2 (18.2%) of 11, and 0 (0%) of 12 treated mice in the RT plus BsAb plus TNF-alpha, RT plus TNF-alpha, RT alone, and control groups, respectively. This difference was statistically significant when TNF-alpha was targeted with the BsAb (p = 0.03). The addition of exogenous TNF-alpha to RT significantly increased the endogenous TNF-alpha mRNA level, particularly when TNF-alpha was targeted with BsAb (p < 0.01). The percentages of necrotic area were significantly augmented in the RT plus BsAb plus TNF-alpha group. CONCLUSION: These results suggest that targeting TNF-alpha with the BsAb provokes RT curability in a CEA-expressing digestive tumor syngenic model and could be considered as a solid rationale for clinical trials.

Purpose: Pancreatic carcinoma is highly resistant to therapy. Epidermal growth factor receptor (EGFR) and HER2 have been reported to be both dysregulated in this cancer. To evaluate the in vivo effect of binding both EGFR and HER2 with two therapeutic humanized monoclonal antibodies (mAb), we treated human pancreatic carcinoma xenografts, expressing high EGFR and low HER2 levels. Experimental Design: Nude mice, bearing xenografts of BxPC-3 or MiaPaCa-2 human pancreatic carcinoma cell lines, were injected twice weekly for 4 weeks with different doses of anti-EGFR (matuzumab) and anti-HER2 (trastuzumab) mAbs either alone or in combination. The effect of the two mAbs, on HER receptor phosphorylation, was also studied in vitro by Western blot analysis. Results: The combined mAb treatment significantly inhibited tumor progression of the BxPC-3 xenografts compared with single mAb injection (P = 0.006) or no treatment (P = 0.0004) and specifically induced some complete remissions. The two mAbs had more antitumor effect than 4-fold greater doses of each mAb. The significant synergistic effect of the two mAbs was confirmed on the MiaPaCa-2 xenograft and on another type of carcinoma, SK-OV-3 ovarian carcinoma xenografts. In vitro, the cooperative effect of the two mAbs was associated with a decrease in EGFR and HER2 receptor phosphorylation. Conclusions: Anti-HER2 mAb has a synergistic therapeutic effect when combined with an anti-EGFR mAb on pancreatic carcinomas with low HER2 expression. These observations may open the way to the use of these two mAbs in a large panel of carcinomas expressing different levels of the two HER receptors.

Purpose: As a first step for the development of a new cancer immunotherapy strategy, we evaluated whether antibody-mediated coating by MHC class I–related chain A (MICA) could sensitize tumor cells to lysis by natural killer (NK) cells. Experimental Design: Recombinant MICA (rMICA) was chemically conjugated to Fab′ fragments from monoclonal antibodies specific for tumor-associated antigens, such as carcinoembryonic antigen, HER2, or CD20. Results: Flow cytometry analysis showed an efficient coating of MICA-negative human cancer cell lines with the Fab-rMICA conjugates. This was strictly dependent on the expression of the appropriate tumor-associated antigens in the target cells. Importantly, preincubation of the tumor cells with the appropriate Fab-rMICA conjugate resulted in NK cell–mediated tumor cell lysis. Antibody blocking of the NKG2D receptor in NK cells prevented conjugate-mediated tumor cell lysis. Conclusions: These results open the way to the development of immunotherapy strategies based on antibody-mediated targeting of MICA.

Recent studies have demonstrated that ionizing radiation activate existing cellular response pathways involving protein kinases. These pathways mediate the cytotoxic and cytoprotective responses of cell death and cell survival, respectively. Cytoprotective responses involve dominantly mitogen-activated protein kinase (MAPK) through radiation-induced activation of EGF receptors and may stimulate cell proliferation if radiation-induced damage is successfully repaired. Similarly, overexpression of EGF receptor family members or their activation by ligands expressed at normal levels may also confer radioresistance. Recent encouraging results indicate that EGF receptor inhibitors such as antibodies or small molecule tyrosine-kinase inhibitors may be effective radiosensitizers in tumors. Within the antibody class of EGF receptor inhibitors are monoclonal antibodies such as cetuximab and trastuzumab. These agents have a common target of the extracellular domain of the EGF receptor. Striking synergistic antitumor effects on human epidermoid and on adenocarcinoma cancer-cell xenografts have been observed when cetuximab treatment is combined with radiotherapy. Promising results have also been obtained from the first clinical trial with cetuximab and radiotherapy in squamous-cell carcinoma of the head and neck. Trastuzumab has been poorly studied in combination with radiotherapy but showed an increased radiosensitivity of HER2-overexpressing breast cancer cells as measured by in vitro colony-forming assays. The mechanism of radiosensitization appears to involve DNA repair. There are well over a dozen agents in the small molecule tyrosine-kinase inhibitor category but the preclinical studies in combination with radiotherapy exist only for ZD1839 and CI1033. Preliminary studies confirm the capacity of ZD1839 and radiotherapy to produce a highly significant increase in tumor growth inhibition when compared to treatment with either modality alone. Another member of the quinazoline class of small molecule tyrosine-kinase inhibitors (CI1033) has recently been examined for its impact in conjunction with radiation in a series of HER-overexpressing breast cancer cell lines. This molecule inhibits tyrosine-kinase activity in all four members of the HER family, and preclinical studies showed a synergistic interaction of CI1033 with ionizing radiation. Finally, EGF receptor family member inhibitors may themselves be effective radiosensitizers and their use in future clinical investigations are based on a solid radiobiological rational.

In recent years, the advent of new tumor-targeting vectors such as monoclonal or bispecific antibodies has resulted in the development of a new generation of therapeutic radiopharmaceuticals and an increasing research interest in this field. However, the emphasis in the overwhelming majority of such studies has been on efficacy in clinical conditions or in animal models of human cancers, and little consideration has been given to the effects of the combination of these antibodies and radiation therapy.

Cetuximab is used in colorectal cancer (CRC), as targeted therapy against the Epithelial Growth Factor receptor (EGFR), in association with chemotherapy (5-FU and irinotecan). Its binding inhibits signalling pathways downstream to the receptor leading to a decrease in proliferation and surviving. In KRAS mutated CRC patients, cetuximab is ineffective, and half of KRAS Wild Type (WT) patients does not respond to cetuximab either. Thus, a better knowledge of cetuximab mechanism of action will help to improve response rate. We have previously shown that activation of the MAP Kinase p38 (p38MAPK) induces irinotecan resistance in vitro and in vivo. The aim of our project is to determine, in KRAS WT colorectal cells, if p38MAPK is involved as well in the cetuximab effect. Experiments were done on two KRAS WT CRC cell lines which respond differently to cetuximab: Caco2 cells (30% of survival inhibition, p53 mutated) and DiFi cells (80% of survival inhibition, p53 Wild Type). Cytotoxic experiments combining cetuximab treatment and inhibition of p38MAPK by a pharmacological inhibitor (SB202190) were performed. We assessed apoptosis and inhibition of proliferation by FACS analysis of cell cycle and DNA synthesis. In addition, Erk, Bim and p27 were analysed by Western Blot. Our results showed that inhibition of p38MAPK by SB202190 enhances cetuximab cytotoxic effect in Caco2 cells but impairs it in DiFi cells. We also observed that inhibition of p38MAPK decreases cetuximab induced apoptosis (from 40% of cells in subG1 to 15%) and anti-proliferative effect (from 10% EdU positive cells to 40%) in DiFi cells. The prevention of cell death by SB202190 in cetuximab treated DiFi cells could be explained by Erk pathway activation and the decrease of p27 and Bim respectively involved in cellular proliferation and mitochondrial apoptosis. We have shown that genetic inhibition of p53 also prevents cetuximab cytotoxicity in DiFi cells and we observed a synergistic effect with p38MAPK inhibition leading to higher impairment of cetuximab effect. Our results have shown the same inhibiting effect of SB202190 on the cytotoxic effect of two tyrosine-kinase inhibitors targeting EGFR (lapatinib and erlotinib) in DiFi cells indicating that p38MAPK implication is linked to inhibition of EGFR kinase activity not to cetuximab only. We have shown that p38MAPK is involved in response to the inhibition of EGFR activity. However, it seems to have different role according to the cell line used and genetic background (p53 status). Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A62. Citation Format: Laetitia Marzi, Eve Combès, Nadia Vezzio-Vié, Gaelle Thomas, Christel Larbouret, Laetitia Linares, Clara Montagut, Mar Iglesias, Vincent Denis, Maguy Del Rio, Pierre Martineau, Céline Gongora. p38MAPK implication in cetuximab response. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A62.

Blockade of the human epidermal growth factor receptor 3 (HER3) and of the downstream phosphatidylinositide 3-kinase (PI3K)/AKT pathway is a prerequisite for overcoming drug resistance and to develop novel treatments for cancers that are not eligible for the currently approved targeted therapies. To this end, we generated specific antibodies (Abs) against domain 1 (D1) and domain 3 (D3) of HER3 that recognize epitopes that do not overlap with the neuregulin-binding site. The fully human H4B-121 Ab and the mouse monoclonal Abs 16D3-C1 and 9F7-F11 inhibited tumor growth in nude mice xenografted with epidermoid, pancreatic, or triple-negative breast cancer cells. The combination of one anti-HER3 Ab and trastuzumab improved tumor growth inhibition in mice xenografted with HER2low cancer cell lines, for which trastuzumab alone shows no or moderate efficiency. Ab-induced disruption of tumor growth was associated with G1 cell cycle arrest, proliferation inhibition, and apoptosis of cancer cells. Anti-HER3 Abs blocked HER2/HER3 heterodimerization and HER3 phosphorylation at the cell membrane, leading to inhibition of phosphorylation of the downstream AKT targets murine double minute 2, X-linked inhibitor of apoptosis, and forkhead box O1. This study demonstrates that anti-HER3 D1 and D3 Abs could represent a new option for immunotherapy of pancreatic and triple-negative breast cancers.

Introduction L’oligomerisation des Recepteurs a Tyrosine-Kinase (RTKs) HER1(EGFR) et HER2 (erbB-2) est un facteur critique dans les mecanismes d’oncogenese. La surexpression de HER2, utilisee pour selectionner les patients en vue d’un traitement a l’herceptine (anti-HER2) est communement evaluee par Immunohistochimie. Cette technique n’est pas quantitative et seulement 60 % des patients repondent a l’herceptine ce qui suggere que d’autres facteurs sont impliques, entre autre les heterodimeres HER1-HER2. Methode Nous avons mesure l’oligomerisation des recepteurs HER par TR-FRET sur des cellules vivantes surexprimant HER1 et/ou HER2 (lignees SKBR3, SKOV3) ainsi que des cellules NIH-3T3 transfectees de facon stable par ces recepteurs. Les cellules en cultures sont transferees dans les puits de plaques de microtitration et incubees avec des anticorps anti-HER ou de l’EGF marques avec un donneur (Terbium) et un accepteur (d2) puis analyse a l’aide d’un fluorimetre en mode temps resolu. Resultats En utilisant un couple d’anticorps tel que l’herceptine (anti-HER2) et le cetuximab (anti-HER1) ou l’EGF marque, nous pouvons quantifier les homodimeres HER1-HER1 ainsi que les heterodimeres HER1-HER2 sur des cellules vivantes. Le signal mesure par TR-FRET augmente en fonction du niveau d’expression des recepteurs HER. Discussion L’oligomerisation des recepteurs HER peut etre mesuree quantitativement par TR-FRET et pourrait etre utilisee pour ameliorer la prediction de la reponse aux therapies anti-HER.

It has been previously demonstrated that tumor cells expressing MICA are no more able to grow in vivo due to the killing of tumor cells by both NK and CD8+ T cells. In order to restore the presence of the MICA ligand at the surface of tumor cells, we designed biomolecules composed of MICA and an scFv (single chain fragment variable) that can recognise tumor associated antigens (TAA). The biomolecules should target tumor cells and re-direct the specific lysis of tumor cells by NK cells after interaction between NKG2D and exogenous MICA at the surface of tumor cells. In vitro cytometry experiments showed that the biomolecules specifically bind different tumor cells expressing TAA. Using 51Cr release assay, we demonstrated that the biomolecules induce an efficient and specific killing of tumor cells mediated by NK cells or human PMBCs. In vivo, biodistribution studies showed that the biomolecules could target xenografted tumor when injected intravenously. Consequently, a protocol is investigated for therapy.