Targeting carcinoma-associated mesothelial cells with antibody-drug conjugates in ovarian carcinomatosis.

Ovarian carcinomatosis is characterized by the accumulation of carcinoma-associated mesothelial cells (CAMs) in the peritoneal stroma and mainly originates through a mesothelial-to-mesenchymal transition (MMT) process. MMT has been proposed as a therapeutic target for peritoneal metastasis. Most ovarian cancer (OC) patients present at diagnosis with peritoneal seeding, which makes tumor progression control difficult by MMT modulation. An alternative approach is to use antibody-drug conjugates (ADCs) targeted directly to attack CAMs. This strategy could represent the cornerstone of precision-based medicine for peritoneal carcinomatosis. Here, we performed complete transcriptome analyses of ascitic fluid-isolated CAMs in advanced OC patients with primary-, high-, and low-grade, serous subtypes and following neoadjuvant chemotherapy. Our findings suggest that both cancer biological aggressiveness and chemotherapy-induced tumor mass reduction reflect the MMT-associated changes that take place in the tumor surrounding microenvironment. Accordingly, MMT-related genes, including fibroblast activation protein (FAP), mannose receptor C type 2 (MRC2), interleukin-11 receptor alpha (IL11RA), myristoylated alanine-rich C-kinase substrate (MARCKS), and sulfatase-1 (SULF1), were identified as specific actionable targets in CAMs of OC patients, which is a crucial step in the de novo design of ADCs. These cell surface target receptors were also validated in peritoneal CAMs of colorectal cancer peritoneal implants, indicating that ADC-based treatment could extend to other abdominal tumors that show peritoneal colonization. As proof of concept, a FAP-targeted ADC reduced tumor growth in an OC xenograft mouse model with peritoneal metastasis-associated fibroblasts. In summary, we propose MMT as a potential source of ADC-based therapeutic targets for peritoneal carcinomatosis. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

OMTX705, a Novel FAP-Targeting ADC Demonstrates Activity in Chemotherapy and Pembrolizumab-Resistant Solid Tumor Models.

PURPOSE: The tumor microenvironment plays a key role in cancer development and progression and is involved in resistance to chemo- and immunotherapy. Cancer-associated fibroblast expressing fibroblast-activating protein α (FAPα) is one of the predominant stroma cell types and is involved in resistance to immunotherapy. EXPERIMENTAL DESIGN: We generated OMTX705, a novel antibody-drug conjugate from a humanized anti-FAP antibody linked to a new cytolysin. Here, we studied its antineoplastic activity in vitro and in preclinical mouse models alone and in combination with chemotherapy as well as immunotherapy in PD-1-resistant tumors. RESULTS: In Avatar models, OMTX705 showed a 100% tumor growth inhibition and prolonged tumor regressions as single agent and in combination with chemotherapy. Treatment rechallenge following treatment discontinuation induced additional tumor regression, suggesting lack of treatment resistance. In a mouse model with a humanized immune system resistant to PD-1 inhibition, OMTX705 increased tumor infiltration by CD8+ T cells, induced complete regressions, and delayed tumor recurrence. CONCLUSIONS: These data suggest that FAP targeting with OMTX705 represents a novel and potent strategy for cancer treatment, including tumors resistant to immunotherapy, and support its clinical development.

Preclinical Efficacy of Endoglin-Targeting Antibody-Drug Conjugates for the Treatment of Ewing Sarcoma.

PURPOSE: Endoglin (ENG; CD105) is a coreceptor of the TGFß family that is highly expressed in proliferating endothelial cells. Often coopted by cancer cells, ENG can lead to neo-angiogenesis and vasculogenic mimicry in aggressive malignancies. It exists both as a transmembrane cell surface protein, where it primarily interacts with TGFß, and as a soluble matricellular protein (sENG) when cleaved by matrix metalloproteinase 14 (MMP14). High ENG expression has been associated with poor prognosis in Ewing sarcoma, an aggressive bone cancer that primarily occurs in adolescents and young adults. However, the therapeutic value of ENG targeting has not been fully explored in this disease. EXPERIMENTAL DESIGN: We characterized the expression pattern of transmembrane ENG, sENG, and MMP14 in preclinical and clinical samples. Subsequently, the antineoplastic potential of two novel ENG-targeting monoclonal antibody-drug conjugates (ADC), OMTX503 and OMTX703, which differed only by their drug payload (nigrin-b A chain and cytolysin, respectively), was assessed in cell lines and preclinical animal models of Ewing sarcoma. RESULTS: Both ADCs suppressed cell proliferation in proportion to the endogenous levels of ENG observed in vitro. Moreover, the ADCs significantly delayed tumor growth in Ewing sarcoma cell line-derived xenografts and patient-derived xenografts in a dose-dependent manner. CONCLUSIONS: Taken together, these studies demonstrate potent preclinical activity of first-in-class anti-ENG ADCs as a nascent strategy to eradicate Ewing sarcoma.

An in vitro tool to assess cytochrome P450 drug biotransformation-dependent cytotoxicity in engineered HepG2 cells generated by using adenoviral vectors.

Many adverse drug reactions leading to hepatotoxicity are caused by the cytochrome P450-dependent activation of non-toxic drugs or chemicals into reactive metabolites. To this end, adenoviruses were used as a tool to efficiently deliver specific CYP genes into cultured cells (i.e., human hepatoma cell line HepG2). Recombinant-defective adenoviral vectors encoding for genes CYP3A4 (Adv-CYP3A4), CYP2E1 (Adv-CYP2E1), CYP2A6 (Adv-CYP2A6) and CYP1A2 (Adv-CYP1A2) were used to confer specific CYP drug metabolic capabilities to HepG2 cells. Upgraded cells transiently expressed single specific cytochrome P450 enzymatic activities in terms of the number of the infecting virus particles used in their transduction. HepG2 cells transduced with adenoviruses and wild HepG2 cells cultured in 96 well-plates were incubated in the presence of model compounds, some of which can be metabolized to reactive metabolites. After compound exposure, cell viability was assessed by the commonly used MTT assay. The results confirm that the cell-based assay is a valuable tool in toxicology assessments and high-throughput screenings to detect cytotoxicity mediated by cytochrome P450 biotransformation in preclinical drug development. The assay also has a potential applicability in other industrial sectors such as the chemical industry.

A database of IC50 values and principal component analysis of results from six basal cytotoxicity assays, for use in the modelling of the in vivo and in vitro data of the EU ACuteTox project.

The main aim of the ACuteTox project (part of the EU 6th Framework programme) is to demonstrate that animal tests for acute systemic toxicity can be replaced by alternative in vitro assays. In this project, data for 97 reference chemicals were collected in the AcuBase database, designed to handle deposited in vitro and in vivo (human and animal) data. To demonstrate the applicability of in vitro basal cytotoxicity tests and in vitro-in vivo modelling, it was deemed necessary to obtain data that were generated via defined standard operating procedures. The molar basal cytotoxicity IC50 values (the 50% inhibitory concentrations for the endpoint measured) for a mouse fibroblast cell line (3T3), a human hepatic cell line (HepG2), a rat hepatic cell line (Fa32), and a human neutrophil cell line (HL-60), were compared, and gave an R(2) correlation of 0.83. To identify chemicals that showed differential cytotoxicity to the various cell types involved, principal component analysis (PCA) was undertaken independently, once all the results had been returned. This showed that colchicine, cycloheximide, digoxin, 5-fluorouracil and hexachlorobenzene gave the lowest correlations with the first score vector of the PCA. The results presented are to be used to identify outliers that need to be further studied via the use of tissue-specific in vitro assays.

DCC regulates cell adhesion in human colon cancer derived HT-29 cells and associates with ezrin.

The deleted in colorectal cancer (DCC) gene encodes a 170- to 190-kDa protein of the Immunoglobulin superfamily. Firstly identified as a tumor suppressor gene in human colorectal carcinomas, the main function for DCC has been described in the nervous system as part of a receptor complex for netrin-1. Moreover, roles in mucosecretory cell differentiation and as inducer of apoptosis have also been reported. DCC knockout mice supported a crucial role for this gene in axonal migration, yet questioned its implication in tumor suppression and mucosecretory differentiation. The work presented here demonstrates that a DCC-transfected HT-29 colonic human cell line (HT-29/DCC) displays an increase in cell-cell adhesion to the detriment of cell-matrix interactions: HT-29/DCC cells exhibit more and better-structured desmosomes while focal adhesions and hemidesmosomes are disrupted. HT-29/DCC cells show no changes in adherent junctions but upon treatment with TPA, HT-29/DCC cells show resistance to scattering, and maintain E-cadherin in the membrane. In addition, the actin cytoskeleton is affected in HT-29/DCC cells: stress fibers are disrupted while cortical actin remains intact. We identified a putative ERM-M (ezrin/radixin/moesin and merlin) binding domain in the juxtamembrane region of the DCC protein. In vitro pull-down assays demonstrate the interaction of the DCC cytoplasmic domain with the N-terminal region of ezrin and merlin, and co-immunoprecipitation assays in transiently DCC-transfected COS-1 cells showed that the interaction between DCC and ezrin also takes place in vivo. Altogether, our results suggest that DCC could regulate cell adhesion and migration through its association with ERM-M proteins.

The transcription factors Slug and Snail act as repressors of Claudin-1 expression in epithelial cells.

Claudin-1 is an integral membrane protein component of tight junctions. The Snail family of transcription factors are repressors that play a central role in the epithelial-mesenchymal transition, a process that occurs during cancer progression. Snail and Slug members are direct repressors of E-cadherin and act by binding to the specific E-boxes of its proximal promoter. In the present study, we demonstrate that overexpression of Slug or Snail causes a decrease in transepithelial electrical resistance. Overexpression of Slug and Snail in MDCK (Madin-Darby canine kidney) cells down-regulated Claudin-1 at protein and mRNA levels. In addition, Snail and Slug are able to effectively repress human Claudin-1-driven reporter gene constructs containing the wild-type promoter sequence, but not those with mutations in two proximal E-box elements. We also demonstrate by band-shift assay that Snail and Slug bind to the E-box motifs present in the human Claudin-1 promoter. Moreover, an inverse correlation in the levels of Claudin-1 and Slug transcripts were observed in breast cancer cell lines. E-box elements in the Claudin-1 promoter were found to play a critical negative regulatory role in breast cancer cell lines that expressed low levels of Claudin-1 transcript. Significantly, in invasive human breast tumours, high levels of Snail and Slug correlated with low levels of Claudin-1 expression. Taken together, these results support the hypothesis that Claudin-1 is a direct downstream target gene of Snail family factors in epithelial cells.

Polypodium leucotomos extract: antioxidant activity and disposition.

The extract of the fern Polypodium leucotomos (PL, Fernblock) is an oral photoprotectant with strong antioxidative properties. Recent studies to determine its chemical composition have shown 4-hydroxycinnamic acid (p-coumaric), 3 methoxy-4-hydroxycinnamic acid (ferulic), 3,4-dihydroxycinnamic acid (caffeic), 3-methoxy-4-hydroxybenzoic acid (vanillic) and 3-caffeoilquinic acid (chlorogenic) to be among its major phenolic components. No conclusive data are available, however, on the H2O2-scavenging capacity of these compounds, or on their absorption and metabolism following their oral intake. In the present work, their antioxidative capacity was assessed by the luminol/H2O2 assay, their absorption studied using Caco-2 cells to resemble the intestinal barrier, and their metabolism investigated using cultured primary rat hepatocytes. The antioxidant capacity of PL components increased in a concentration-dependent manner, with ferulic and caffeic acids the most powerful antioxidants. The apparent permeability results correspond to a human post-oral administration absorption of 70-100% for all tested substances. Coumaric, ferulic and vanillic acids were metabolized by CYP450-dependent mono-oxygenases and partially conjugated to glucuronic acid and sulfate. These phenolic compounds may contribute to the health benefits afforded by this oral photoprotectant.

Evolutionary combinatorial chemistry, a novel tool for SAR studies on peptide transport across the blood-brain barrier. Part 2. Design, synthesis and evaluation of a first generation of peptides.

The use of high-throughput methods in drug discovery allows the generation and testing of a large number of compounds, but at the price of providing redundant information. Evolutionary combinatorial chemistry combines the selection and synthesis of biologically active compounds with artificial intelligence optimization methods, such as genetic algorithms (GA). Drug candidates for the treatment of central nervous system (CNS) disorders must overcome the blood-brain barrier (BBB). This paper reports a new genetic algorithm that searches for the optimal physicochemical properties for peptide transport across the blood-brain barrier. A first generation of peptides has been generated and synthesized. Due to the high content of N-methyl amino acids present in most of these peptides, their syntheses were especially challenging due to over-incorporations, deletions and DKP formations. Distinct fragmentation patterns during peptide cleavage have been identified. The first generation of peptides has been studied by evaluation techniques such as immobilized artificial membrane chromatography (IAMC), a cell-based assay, log Poctanol/water calculations, etc. Finally, a second generation has been proposed.

Influence of cytoplasmic deletions on the filopodia-inducing effect of syndecan-3.

Syndecans, transmembrane heparan sulfate proteoglycans (HSPG), mediate cell-cell and cell-matrix adhesion thereby controlling cell movement and shape. Syndecan cytoplasmic domains are very short (ca. 30 amino acids) and divided into two constant regions (C1 and C2) separated by one variable (V) region. Here we attempted to map the cytoplasmic region responsible for the filopodia-inducing effect of syndecan-3. We found that only the C1-region was necessary for this effect. In addition, the deletion of the C2-region led to extensive membrane blebbing. Nevertheless, the elimination of the entire cytoplasmic region did not affect delivery of syndecan-3 to the plasma membrane. These results indicate that the different regions of syndecan-3 cytoplasmic domain have different functions probably by binding to distinct proteins.

Erythropoietin protects the in vitro blood-brain barrier against VEGF-induced permeability.

The blood-brain barrier (BBB) ensures the homeostasis of the brain microenvironment, mostly through complex tight junctions between brain endothelial cells that prevent the passage of hydrophilic molecules from blood to brain and vice versa. A recent study has shown in vivo that systemic administration of erythropoietin (Epo) protects against brain injury. Using an in vitro model of the bovine BBB, we observed that the expression of the Epo receptor is modulated by its ligand and hypoxic stimuli such as vascular endothelial growth factor (VEGF) treatment. In addition, Epo protects against the VEGF-induced permeability of the BBB, decreases the levels of endothelial nitric oxide synthase and restores junction proteins. The kinetic transport experiments revealed the capacity of Epo to cross the in vitro BBB in a saturable and specific way. Our results suggest a new mechanism for Epo-induced neuroprotection, in which circulating Epo controls and maintains the BBB through an Epo receptor signalling pathway and the re-establishment of cell junctions.