Abstract 5146: In vitro neutrophil assays to support immuno-oncology drug development

Neutrophils have shown a lot of plasticity with important consequences on cancer disease progression and have been associated with multiple functions such as killing antibody-opsonized cancer cells, directly kill tumor cells through the release of reactive oxygen and nitrogen species and a controversial role in the tumor micro-environment with both pro- and anti-tumor roles. Studying neutrophil function in vitro can be done using the Incucyte® live imaging system to monitor antibody-dependent cell-mediated cytotoxicity (ADCC). Optimised in vitro assays using fresh human neutrophils and fluorescent-labeled tumor cells can be used to screen the potency of candidate therapeutics. Additionally, neutrophil chemotaxis can be monitored using transwell plates and live imaging via Incucyte®. Finally, multiplex cytokine and chemokine analysis after activation and stimulation of neutrophils can be evaluated using Luminex technology. When studying neutrophil activity in vitro, important factors such as access to fresh blood and optimized protocols for purifying untouched neutrophils are key for reproducible and reliable results.

Citation Format: Alanah Pieters, Martijn Vlaming, Jezabel Lefevere, Sofie Pattyn. In vitro neutrophil assays to support immuno-oncology drug development. [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 5146.

Abstract 5168: In vitro suppressive Treg bioassays for screening of candidate therapeutics

The increasing interest in the tumor microenvironment leads to a focus on new bioassays to represent all the players of the cancer immune response. Some of these players like regulatory T cells play an important role by downregulating the anti-tumor response. Their regulation mechanisms constitute an important target for new therapeutics. In order to study these mechanisms in a human model, suppressive Treg bioassays mimicking the suppressive action of these cells were developed and optimized. In vitro suppressive assays come with many technical challenges, therefore protocols for the purification and in vitro culture of regulatory T cells were optimized and fine-tuned to result in an optimal assay window e and allow screening of multiple candidates. Donor-to-donor variation is controlled by pre-evaluation of multiple donors and standardized methods are used for isolation and in vitro culture of responding and suppressive cells. Access to a large and broad panel of healthy donors is required for the evaluation of therapeutic agents targeting the regulatory T cell pathway.

Citation Format: Martijn Vlaming, Alanah Pieters, Jezabel Lefevere, Sofie Pattyn. In vitro suppressive Treg bioassays for screening of candidate therapeutics. [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 5168.

Expression and Functionality of Connexin-Based Channels in Human Liver Cancer Cell Lines

Liver cancer cell lines are frequently used in vitro tools to test candidate anti-cancer agents as well as to elucidate mechanisms of liver carcinogenesis. Among such mechanisms is cellular communication mediated by connexin-based gap junctions. The present study investigated changes in connexin expression and gap junction functionality in liver cancer in vitro. For this purpose, seven human liver cancer cell lines, as well as primary human hepatocytes, were subjected to connexin and gap junction analysis at the transcriptional, translational and activity level. Real-time quantitative reverse transcription polymerase chain reaction analysis showed enhanced expression of connexin43 in the majority of liver cancer cell lines at the expense of connexin32 and connexin26. Some of these changes were paralleled at the protein level, as evidenced by immunoblot analysis and in situ immunocytochemistry. Gap junctional intercellular communication, assessed by the scrape loading/dye transfer assay, was generally low in all liver cancer cell lines. Collectively, these results provide a full scenario of modifications in hepatocyte connexin production and gap junction activity in cultured liver cancer cell lines. The findings may be valuable for the selection of neoplastic hepatocytes for future mechanistic investigation and testing of anti-cancer drugs that target connexins and their channels.

Connexin-Based Channel Activity Is Not Specifically Altered by Hepatocarcinogenic Chemicals

Connexin-based channels play key roles in cellular communication and can be affected by deleterious chemicals. In this study, the effects of various genotoxic carcinogenic compounds, non-genotoxic carcinogenic compounds and non-carcinogenic compounds on the expression and functionality of connexin-based channels, both gap junctions and connexin hemichannels, were investigated in human hepatoma HepaRG cell cultures. Expression of connexin26, connexin32, and connexin43 was evaluated by means of real-time reverse transcription quantitative polymerase chain reaction analysis, immunoblot analysis and in situ immunostaining. Gap junction functionality was assessed via a scrape loading/dye transfer assay. Opening of connexin hemichannels was monitored by measuring extracellular release of adenosine triphosphate. It was found that both genotoxic and non-genotoxic carcinogenic compounds negatively affect connexin32 expression. However, no specific effects related to chemical type were observed at gap junction or connexin hemichannel functionality level.

In Vitro Liver Toxicity Testing of Chemicals: A Pragmatic Approach

The liver is among the most frequently targeted organs by noxious chemicals of diverse nature. Liver toxicity testing using laboratory animals not only raises serious ethical questions, but is also rather poorly predictive of human safety towards chemicals. Increasing attention is, therefore, being paid to the development of non-animal and human-based testing schemes, which rely to a great extent on in vitro methodology. The present paper proposes a rationalized tiered in vitro testing strategy to detect liver toxicity triggered by chemicals, in which the first tier is focused on assessing general cytotoxicity, while the second tier is aimed at identifying liver-specific toxicity as such. A state-of-the-art overview is provided of the most commonly used in vitro assays that can be used in both tiers. Advantages and disadvantages of each assay as well as overall practical considerations are discussed.

Rodent models of cholestatic liver disease: A practical guide for translational research

Cholestatic liver disease denotes any situation associated with impaired bile flow concomitant with a noxious bile acid accumulation in the liver and/or systemic circulation. Cholestatic liver disease can be subdivided into different types according to its clinical phenotype, such as biliary atresia, drug-induced cholestasis, gallstone liver disease, intrahepatic cholestasis of pregnancy, primary biliary cholangitis and primary sclerosing cholangitis. Considerable effort has been devoted to elucidating underlying mechanisms of cholestatic liver injuries and explore novel therapeutic and diagnostic strategies using animal models. Animal models employed according to their appropriate applicability domain herein play a crucial role. This review provides an overview of currently available in vivo animal models, fit-for-purpose in modelling different types of cholestatic liver diseases. Moreover, a practical guide and workflow is provided which can be used for translational research purposes, including all advantages and disadvantages of currently available in vivo animal models.

Biomarkers of cholestasis

Cholestasis is a major pathological manifestation, often resulting in detrimental liver conditions, which occurs in a variety of indications collectively termed cholestatic liver diseases. The frequent asymptomatic character and complexity of cholestasis, together with the lack of a straightforward biomarker, hampers early detection and treatment of the condition. The 'omics' era, however, has resulted in a plethora of cholestatic indicators, yet a single clinically applicable biomarker for a given cholestatic disease remains missing. The criteria to fulfil as an ideal biomarker as well as the challenging molecular pathways in cholestatic liver diseases advocate for a scenario in which multiple biomarkers, originating from different domains, will be assessed concomitantly. This review gives an overview of classical clinical and novel molecular biomarkers in cholestasis, focusing on their benefits and drawbacks.

Cholestasis Differentially Affects Liver Connexins

Connexins are goal keepers of tissue homeostasis, including in the liver. As a result, they are frequently involved in disease. The current study was set up to investigate the effects of cholestatic disease on the production of connexin26, connexin32 and connexin43 in the liver. For this purpose, bile duct ligation, a well-known trigger of cholestatic liver injury, was applied to mice. In parallel, human hepatoma HepaRG cell cultures were exposed to cholestatic drugs and bile acids. Samples from both the in vivo and in vitro settings were subsequently subjected to assessment of mRNA and protein quantities as well as to in situ immunostaining. While the outcome of cholestasis on connexin26 and connexin43 varied among experimental settings, a more generalized repressing effect was seen for connexin32. This has also been observed in many other liver pathologies and could suggest a role for connexin32 as a robust biomarker of liver disease and toxicity.

Targeting gap junctional intercellular communication by hepatocarcinogenic compounds

Gap junctions in liver, as in other organs, play a critical role in tissue homeostasis. Inherently, these cellular constituents are major targets for systemic toxicity and diseases, including cancer. This review provides an overview of chemicals that compromise liver gap junctions, in particular biological toxins, organic solvents, pesticides, pharmaceuticals, peroxides, metals and phthalates. The focus in this review is placed upon the mechanistic scenarios that underlie these adverse effects. Further, the potential use of gap junctional activity as an in vitro biomarker to identify non-genotoxic hepatocarcinogenic chemicals is discussed.

Predicting factors for chronic colonization of Pseudomonas aeruginosa in bronchiectasis

About 25% of the patients with bronchiectasis are likely to develop a chronic colonization with Pseudomonas aeruginosa. A better understanding of predictors of acquiring Pseudomonas within the patient population may facilitate future focused research. The aim of this retrospective observational study was to investigate predicting factors for P. aeruginosa colonization in patients with bronchiectasis. This was a single-center retrospective cohort study using a bronchiectasis database which consisted of 211 patients with bronchiectasis. Data were collected for demographic details, etiology, spirometry, microbiology data, maintenance medication use, exacerbation frequency, hospital admission rate, and FACED and Bronchiectasis Severity Index (BSI) score. Two hundred eleven patients were identified from our bronchiectasis database. Overall, 25% of the patients (n = 53) had a chronic colonization with P. aeruginosa. Seventeen patients (8%) died in a 5-year follow-up period of whom 7 (41%) had a chronic P. aeruginosa colonization (p > 0.05). After multiple regression analysis, P. aeruginosa-positive patients were significantly associated with an older age (> 55 years) (p = 0.004), the use of hypertonic saline (0.042), and inhalation antibiotics (< 0.001). Furthermore, the presence of PCD (p < 0.001) and post-infectious etiology (p < 0.001) as underlying causes were significantly associated with P. aeruginosa colonization. We observed that independent predictors for P. aeruginosa colonization were age > 55 years, hypertonic saline, and PCD, and post-infectious etiology as underlying causes of bronchiectasis. Since prevention of P. aeruginosa colonization is an important aim in the treatment of bronchiectasis, more attention could be directed to these groups at risk for Pseudomonas colonization.

Impact of anti-CASPR2 autoantibodies from patients with autoimmune encephalitis on CASPR2/TAG-1 interaction and Kv1 expression

Autoantibodies against CASPR2 (contactin-associated protein-like 2) have been linked to autoimmune limbic encephalitis that manifests with memory disorders and temporal lobe seizures. According to the growing number of data supporting a role for CASPR2 in neuronal excitability, CASPR2 forms a molecular complex with transient axonal glycoprotein-1 (TAG-1) and shaker-type voltage-gated potassium channels (Kv1.1 and Kv1.2) in compartments critical for neuronal activity and is required for Kv1 proper positioning. Whereas the perturbation of these functions could explain the symptoms observed in patients, the pathogenic role of anti-CASPR2 antibodies has been poorly studied. In the present study, we find that patient autoantibodies alter Caspr2 distribution at the cell membrane promoting cluster formation. We confirm in a HEK cellular model that the anti-CASPR2 antibodies impede CASPR2/TAG-1 interaction and we identify the domains of CASPR2 and TAG-1 taking part in this interaction. Moreover, introduction of CASPR2 into HEK cells induces a marked increase of the level of Kv1.2 surface expression and in cultures of hippocampal neurons Caspr2-positive inhibitory neurons appear to specifically express high levels of Kv1.2. Importantly, in both cellular models, anti-CASPR2 patient autoAb increase Kv1.2 expression. These results provide new insights into the pathogenic role of autoAb in the disease.

The Role of Stromal Cells in Tumor Metastases

Background: In 1889, Stephen Paget hypothesized that metastatic cells - the “seeds” - only grow in the secondary sites - the “soil” - with a permissive microenvironment. Here, we show that the “seeds” can carry their own “soil” - activated fibroblasts from primary site of metastatic tumors. Moreover, we report that carryover of these non-malignant host-derived cells during metastatic cell colonization in the lungs can increase cancer's metastatic efficiency.Materials and Methods: We use multiple animal models and two metastatic tumor cell lines (LLC1 and LA-P0297) to study the composition, origin and role of fragments shed by tumors in the metastatic process.Results: we have shown that, in addition to single cells (81%), tumors shed fragments consisting of both tumor and host cells. We show that these fragments are more viable in the circulation compared to tumor cells alone (p&lt;0.05). When we selectively deplete the host cells in the tumor microenvironment the spontaneous formation of metastases is significantly reduced three weeks after primary tumor resection compared to control mice (p&lt;0.05). Next, survival was significantly increased in mice with metastases after co-implantation of carcinoma-associated fibroblasts (CAFs) isolated from breast cancer patients together with LLC1 cells, but had no effect in mice implanted with LLC1 cells alone (p&lt;0.01) Lastly, we have assessed the nature of these host stromal cells using immunohistochemistry and RT-PCR and indentified the majority of them as being of mesenchymal/fibroblast lineage.Discussion: We found that tumor-associated stromal cells can escape primary tumors along with cancer cells, survive in blood circulation and in metastatic nodules. Pre-existence of a tissue-like structure in the form of heterotypic cell fragments may increase the viability of cancer cells in blood circulation and modulate metastasis efficiency. How this mechanism contributes to the organo-tropism of certain metastatic tumors is not known. But demonstration of the involvement of some of the same tumor “soil” in both local and distant tumor invasion has important conceptual and clinical implications for colonization during metastasis progression.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6151.

The role of oral fluoropyrimidines in the treatment of advanced gastric cancer

Although the incidence of gastric cancer is declining during the second half of the 20th century, it remains the second leading cause of cancer death worldwide. The majority of patients with gastric cancer will require palliative treatment at some point in the course of their disease. Approximately 50% of patients already have advanced incurable disease at the time of initial presentation, and even those who undergo potentially curative resection have high rates of distant as well as local recurrence. Chemotherapy in advanced gastric cancer demonstrated a significant survival benefit over best supportive care alone. Median overall survival increased from 3-5 to 8-12 months. Today, a platinum based regimen is considered as first-line treatment in advanced gastric cancer. Different regimens are investigated and used in routine practice. Similarly to fluorouracil, capecitabine is well tolerated in combination with a range of cytotoxic drugs. As a single agent, it has not undergone large scale randomised studies. S-1, another oral fluoropyrimidine, is a potential challenger to the role of capecitabine, but is lacking phase III data in Western population.

Brucellar spondylodiscitis: case report

Brucellosis is a common zoonosis which still remains a major health problem in certain parts of the world. Osteoarticular involvement is the most frequent complication of brucellosis, in which the diagnosis of brucellar spondylodiscitis is often difficult since the clinical presentation may be obscured by many other conditions. Herein, we report an uncommon case of spondylodiscitis due to Brucella in a male who presented with abdominal pain. The diagnosis was established by positron emission tomography combined with computed tomography (PET/CT scan) and magnetic resonance followed by a confirmation on Brucella-agglutination test and positive culture of computed tomography (CT) guided punction fluid. This case report illustrates an atypical presentation of spondylitis and points out the difficulties in diagnosing the aetiological agens Brucella and differentiating its specific features from tuberculosis.

Seasonal changes in photosynthesis of trees in the flooded forest of the Mapire River

We studied the flood tolerance of five tree species growing in the flooded forest adjacent to the Mapire river, in SW Venezuela. Mean photosynthetic rate and leaf conductance were 11 &mgr;mol m(-2) s(-1) and 700 mmol m(-2) s(-1), respectively. Xylem water potential ranged from -0.08 to -1.15 MPa. Based on leaf gas exchange as a criterion of tolerance to flooding, two response patterns were identified: (1) decreasing photosynthetic rate with increasing flooding and leaf conductance (Psidium ovatifolium Berg. ex Desc., Campsiandra laurifolia Benth., Symmeria paniculata Benth. and Acosmium nitens (Vog.) Benth); and (2) independence of photosynthesis and leaf conductance from flooding (Eschweilera tenuifolia (Berg.) Miers.). In the first response pattern, declining photosynthetic rate with flooding may be interpreted as a sign of reduced flood tolerance, whereas the second response pattern may indicate increased flood tolerance. An increase in xylem water potential with depth of water column was found for all species (with the possible exception of P. ovatifolium), indicating that flooding does not cause water stress in these trees. Submerged leaves that had been under water for between four days and four months generally had photosynthetic rates and leaf conductances similar to those of aerial leaves, indicating maintenance of photosynthetic capacity under water. Daily positive oscillations in glucan content in submerged leaves of P. ovatifolium and C. laurifolia suggest that submerged leaves do not represent a sink for photosynthates produced by aerial leaves.

A highly conserved region of the Sendai virus nucleocapsid protein contributes to the NP-NP binding domain

The nucleocapsid protein (NP) of Sendai virus is an essential component of both the nucleocapsid template and the NP-NP and NP0-P protein complexes required for viral RNA replication. When expressed alone in mammalian cells NP self-assembles into nucleocapsid-like particles which appear to contain cellular RNA. To identify putative NP-NP binding domains, fusions between the monomeric maltose-binding protein (MBP) and portions of NP were constructed. The fusion proteins which contain the central conserved region (CCR) (amino acids 258-357, MBP-NP1) and the N-terminal 255 amino acids (MBP-NP2) of NP both oligomerized, suggesting that these regions contain sequences important for NP-NP self-assembly. In addition, the MBP-NP1 fusion protein can function as an inhibitor of viral RNA replication. Complementary studies involving site-directed mutagenesis of the full-length NP protein have identified specific residues in the CCR which are essential for viral RNA replication in vitro. Two such replication-negative mutants, F324V and F324I, were defective in self-assembly, suggesting that the Phe residue at amino acid 324 is essential for the NP-NP interaction. A third mutant, NP260-1 (Y260D), self-assembled to form aberrant oligomers which exhibit an unusual helical structure and appear to lack any associated RNA. The mutants NP299-5 (L299I and I300V) and NP313-2 (I313F), in contrast, appear to form all the required protein complexes, but were inactive in viral RNA replication, suggesting that interactions specifically with Sendai RNA were disrupted. These data have thus identified specific residues in the CCR of the native NP protein which appear to be important for NP-NP or NP-RNA interactions and for genome replication.

Influence of explant source on in vitro axillary shoot formation in oak seedlings

In vitro shoot development was slower for apical shoot explants of young oak (Quercus robur L.) seedlings growing on Woody Plant Medium containing activated charcoal than for nodal shoot explants. The rate of in vitro shoot development was slowest in explants taken from seedlings that were undergoing rapid shoot elongation and most rapid in explants taken from seedlings that had stopped elongating and had fully expanded leaves. Maximum rooting was achieved on half-strength Woody Plant Medium containing activated charcoal. Rooting ability was not influenced by explant source.