Sc, an abnormal form of cellular prion protein (PrP), in the brain of animals and humans leads to fatal neurodegenerative disorders known as prion diseases. Limited protease digestion of PrP Sc produces a truncated form called PrP(27-30) that retains prion infectivity and is the main marker of disease targeted in most diagnostic tests. In the search for new anti-prion molecules, drug-screening assays on prion-infected murine cells have been oriented toward decreasing levels of PrP(27-30). In contrast, we screened for drugs promoting multimers of PrP(27-30), illustrating a possible stabilization of mouse PrP Sc species, because recent studies aiming to characterize the conformational stability of various prion strains showed that stable recombinant amyloids produced more stable prion strain, leading to longest incubation time. We identified a family of thienyl pyrimidine derivatives that induce SDS-resistant dimers and trimers of PrP(27-30). Bioassays performed on mice brain homogenates treated with these compounds showed that these thienyl pyrimidine derivatives diminished prion infectivity in vivo. Oligomeric-induced activity by thienyl pyrimidine compounds is a promising approach not only to understanding the pathogenesis of prions but also for prion diagnostics. This approach could be extended to other neurodegenerative "prionopathies," such as Alzheimer's, Huntington, or Parkinson's diseases.

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.

BackgroundMetastatic colorectal cancer (mCRC) is one of the major causes of cancer-related death. Despite the substantial progress in mCRC management, it remains important to identify new therapeutic options and biological markers for personalized medicine. Here, we investigated the expression of claudin-1 (CLDN1), a major tight junction transmembrane protein, in the different colorectal cancer (CRC) molecular subtypes and then assessed the anti-tumor effect of a new anti-CLDN1 monoclonal antibody (mAb).MethodsGene expression profiling and immunochemistry analysis of normal and tumor tissue samples from patients with stage IV CRC were used to determine CLDN1 gene expression. Then, the 6F6 mAb against CLDN1 extracellular part was generated. Its effect on CRC cell cycle, proliferation, survival and migration was assessed in vitro, using a 3D cell culture system, flow cytometry, clonogenic and migration assays. In vivo, 6 F6 mAb efficacy was evaluated in nude mice after subcutaneous xenografts or intrasplenic injection of CRC cells.ResultsCompared with normal mucosa where it was almost exclusively cytoplasmic, in CRC samples CLDN1 was overexpressed (p < 0.001) and mainly localized at the membrane. Moreover, it was differentially expressed in the various CRC molecular subtypes. The strongest expressions were found in the consensus molecular subtype CMS2 (p < 0.001), the transit-ampliflying (p < 0.001) and the C5 subtypes (p < 0.001). Lower CLDN1 expression predicted a better outcome in the molecular subtypes C3 and C5 (p = 0.012 and p = 0.004, respectively). CLDN1 targeting with the 6 F6 mAb led to reduction of survival, growth and migration of CLDN1-positive cells. In preclinical mouse models, the 6F6 mAb decreased tumor growth and liver metastasis formation.ConclusionOur data indicate that CLDN1 targeting with an anti-CLDN1 mAb results in decreased growth and survival of CRC cells. This suggests that CLDN1 could be a new potential therapeutic target.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-017-0558-5) contains supplementary material, which is available to authorized users.

BackgroundPrion diseases are characterized by the accumulation in the central nervous system of an abnormally folded isoform of the prion protein, named PrPSc. Aggregation of PrPSc into oligomers and fibrils is critically involved in the pathogenesis of prion diseases. Oligomers are supposed to be the key neurotoxic agents in prion disease, so modulation of prion aggregation pathways with small molecules can be a valuable strategy for studying prion pathogenicity and for developing new diagnostic and therapeutic approaches. We previously identified thienyl pyrimidine compounds that induce SDS-resistant PrPSc (rSDS-PrPSc) oligomers in prion-infected samples.ResultsDue to the low effective doses of the thienyl pyrimidine hits, we synthesized a quaterthiophene-bis-triazine compound, called MR100 to better evaluate their diagnostic and therapeutic potentials. This molecule exhibits a powerful activity inducing rSDS-PrPSc oligomers at nanomolar concentrations in prion-infected cells. Fluorescence interaction studies of MR100 with mouse PrP fibrils showed substantial modification of the spectrum, and the interaction was confirmed in vitro by production of rSDS-oligomer species upon incubation of MR100 with fibrils in SDS-PAGE gel. We further explored whether MR100 compound has a potential to be used in the diagnosis of prion diseases. Our results showed that: (i) MR100 can detect rSDS-oligomers in prion-infected brain homogenates of various species, including human samples from CJD patients; (ii) A protocol, called “Rapid Centrifugation Assay” (RCA), was developed based on MR100 property of inducing rSDS-PrPSc oligomers only in prion-infected samples, and avoiding the protease digestion step. RCA allows the detection of both PK-sensitive and PK-resistant PrPSc species in rodents samples but also from patients with different CJD forms (sporadic and new variant); (iii) A correlation could be established between the amount of rSDS-PrPSc oligomers revealed by MR100 and the duration of the symptomatic phase of the disease in CJD patients; and (iv) Bioassay experiments showed that MR100 can trap prion infectivity more efficiently than P30 drug.ConclusionsMR100 is a powerful tool not only for studying the prion aggregation pathways regarding oligomeric and sPrPSc species, but also for developing alternative methods for the detection of prion-infected samples. Considering our bioassay results, MR100 is a promising molecule for the development of prion decontamination approaches.Electronic supplementary materialThe online version of this article (doi:10.1186/s13024-016-0074-7) contains supplementary material, which is available to authorized users.

Transmissible spongiform encephalopathies (TSEs), also called prion diseases, are fatal, infectious, genetic or sporadic neurodegenerative disorders of humans and animals. In humans, TSEs are represented by Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome, Fatal Familial Insomnia and Kuru. In animals, the most prominent prion diseases are scrapie of sheep and goats, bovine spongiform encephalopathy (BSE) of cattle and chronic wasting disease (CWD) of deer and elk. A critical event in prion diseases is the accumulation in the central nervous system (CNS) of the abnormally folded PrP(Sc) protein that is the protease-resistant isoform of a normal cellular protein encoded by the host and called PrP(C). PrP(Sc) (also known as rPrP(Sc) or PrP27-30) represents the main marker of prion diseases and is routinely used in the reference method for the diagnosis of prion diseases. Most of the therapeutic strategies developed so far aimed at identifying compounds that diminish the levels of PrP(Sc), with variable success when tested in vivo. In this review, we present an alternative approach in which small molecules that induce PrP(Sc) oligomers are identified. By using virtual and cellular screenings, we found several thienyl pyrimidine compounds that trigger PrP(Sc) oligomerization and trap prion infectivity.

In metastatic colorectal cancer (CRC) patients, chemotherapy in combination with targeted therapies such as Avastin, Erbitux, and Vectibix (monoclonal antibodies) has improved response rates with prolongation of progression free survival and overall survival. Despite these major therapeutic progresses, at least 30 to 50% of patients remain non-responders. Our project aimed to identify and validate new molecular targets of CRC. Comparison of gene expression profiles between normal mucosa and primary tumor of CRC patients followed by immunohistochemistry analysis identified claudin-1 (CLDN1) as potential therapeutic target for antibody-targeted therapy. CLDN1 is a major tight junction transmembrane protein, already found overexpressed in CRC in several studies and associated with tumor progression. We have generated monoclonal antibodies (mAb) directed against extracellular domains of CLDN1 and demonstrated their specificity against human CLDN1 in vitro and in vivo. Then, using mice xenografted with the CRC cell line SW620 we tested the therapeutic effect of the 6F6C3mAb. The mice were treated by i.p. injections with vehicle or 6F6C3mAb at two different doses. The results showed that 6F6C3mAb treated-groups had a significant (p= 0,018) reduced growth compared to the control group and this effect was dose-dependent. The in vitro effects of the binding of 6F6C3mAb to CLDN1 were also assessed by clonogenic assays. Treatment by 6F6C3mAb induced a significant (p&lt; 0.05) reduction of the number of colony-forming cells for CLDN1high colorectal cancer cells (SW620, Caco2) but also for CLDN1high ovarian and pancreatic cancer cells (PANC1, BXPC3, SKOV3, IGROV1). Thus, 6F6C3mAb binding had a profound effect on cancer cell survival. In conclusion, CLDN1 seems to be a promising target for antibody-based therapy. The 6F6C3mAb is able to inhibit tumor growth and tumor survival by binding the extracellular domains of CLDN1. It can be used in the treatment of cancer diseases such as colorectal cancer as well in adjuvant as in metastatic setting. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B245. Citation Format: Adeline Ayrolles-Torro, Nadia Vezzio-Vie, Vincent Denis, Florence Boissiere-Michot, Véronique Garambois, Muriel Busson, Imade Ait Arsa, Caroline Mollevi, Martine Pugniere, Frédéric Bibeau, Pierre Martineau, Céline Gongora, Maguy Del Rio. Claudin-1 (CLDN1) as a new therapeutic target in colorectal cancer: Inhibition of cell growth and survival by an anti-CLDN1 monoclonal antibody. [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 B245.

Background Tumor resistance is a frequent cause of therapy failure and remains a major challenge for the long-term management of colorectal cancer (CRC). The aim of this study was to determine the implication of the tight junctional protein claudin 1 (CLDN1) in the acquired resistance to chemotherapy. Methods Immunohistochemistry was used to determine CLDN1 expression in post-chemotherapy liver metastases from 58 CRC patients. The effects of oxaliplatin on membrane CLDN1 expression were evaluated by flow cytometry, immunofluorescence and western blotting experiments in vitro and in vivo. Phosphoproteome analyses, proximity ligation and luciferase reporter assays were used to unravel the mechanism of CLDN1 induction. RNAseq experiments were performed on oxaliplatin-resistant cell lines to investigate the role of CLDN1 in chemoresistance. The “one-two punch” sequential combination of oxaliplatin followed by an anti-CLDN1 antibody-drug conjugate (ADC) was tested in both CRC cell lines and murine models. Results We found a significant correlation between CLDN1 expression level and histologic response to chemotherapy, CLDN1 expression being the highest in resistant metastatic residual cells of patients showing minor responses. Moreover, in both murine xenograft model and CRC cell lines, CLDN1 expression was upregulated after exposure to conventional chemotherapies used in CRC treatment. CLDN1 overexpression was, at least in part, functionally related to the activation of the MAPKp38/GSK3β/Wnt/β-catenin pathway. Overexpression of CLDN1 was also observed in oxaliplatin-resistant CRC cell lines and was associated with resistance to apoptosis, suggesting an anti-apoptotic role for CLDN1. Finally, we demonstrated that the sequential treatment with oxaliplatin followed by an anti-CLDN1 ADC displayed a synergistic effect in vitro and in in vivo. Conclusion Our study identifies CLDN1 as a new biomarker of acquired resistance to chemotherapy in CRC patients and suggests that a “one-two punch” approach targeting chemotherapy-induced CLDN1 expression may represent a therapeutic opportunity to circumvent resistance and to improve the outcome of patients with advanced CRC.

Colorectal cancer (CRC) is one of the major causes of cancer-related deaths in the Western world. When localized, CRC is often curable by surgery, but the prognosis of patients with metastatic disease remains very poor. The current treatment of metastatic CRC (mCRC) relies on therapy combining chemotherapy and targeted therapies. However, relapses are observed in most cases due to the occurrence of drug resistance. Therefore, more therapeutic options are required particularly by identifying new molecular targets that can be reached by antibodies. We previously showed that Claudin-1 (CLDN1), a major constituent of tight junctions, is overexpressed at the membrane of CRC cells which makes it a good target for antibodies. Besides, CLDN1 is differentially expressed in the new CRC molecular subtypes. We have then developed a monoclonal antibody (mAb) against CLDN1, called 6F6, which targets the extracellular part of CLDN1. Results showed that the 6F6 mAb significantly decreased cell growth, survival, and migration in vitro as well as in vivo. Furthermore, we demonstrated the cytostatic effect of the 6F6 mAb through proliferation assays. We are now deciphering the role of CLDN1 on 3D spheroids, a model that reflects the physiopathology. Using immunofluorescence staining on frozen sections we are exploring the impact of CLDN1 on spheroids proliferation. We are also investigating on the distribution of tight junction proteins implicated on cell proliferation in the presence or absence of CLDN1. CLDN1 is a new promising therapeutic target in CRC, it is now interesting to elucidate its role in colorectal cancer cell proliferation. Keywords: Colorectal, Cancer, Claudin-1, monoclonal antibodies, spheroids, proliferation Citation Format: Sara Cherradi, Adeline Ayrolles-Torro, Nadia Vezzo-Vié, Eve Combes, Lucile Canterel-Thouennon, Fabien Gava, Valérie Lobjois, Bernard Ducommun, Celine Gongora, Maguy Del Rio. Targeting the tight junction protein claudin-1 in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2902.