The Validation of Toxicological Prediction Models

An alternative method is shown to consist of two parts: the test system itself; and a prediction model for converting in vitro endpoints into predictions of in vivo toxicity. For the alternative method to be relevant and reliable, it is important that its prediction model component is of high predictive power and is sufficiently robust against sources of data variability. In other words, the prediction model must be subjected to criticism, leading successful models to the state of confirmation. It is shown that there are certain circumstances in which a new prediction model may be introduced without the necessity to generate new test system data.

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Recommendations for the Application of Biostatistical Methods during the Development and Validation of Alternative Toxicological Methods

Alternatives to Laboratory Animals ◽

10.1177/026119299602400410 ◽

1996 ◽

Vol 24 (4) ◽

pp. 511-530

Author(s):

Hermann-Georg Holzhütter ◽

Graeme Archer ◽

Nadia Dami ◽

David P. Lovell ◽

Andrea Saltelli ◽

...

Keyword(s):

Prediction Models ◽

Task Force ◽

Test System ◽

Alternative Methods ◽

In Vitro Test ◽

General Importance ◽

Study Designs ◽

Development And Validation

Assessment of the relevance and reliability of alternative toxicological methods requires the application of biostatistical methods. This report contains the recommendations of the ECVAM Task Force on Biostatistics for the appropriate use of biometrical methods, and for closer collaboration between biostatisticians and experimental toxicologists in the development and validation of alternative methods. The main objectives of these recommendations are to improve the compatibility of the results obtained from different studies, and to prevent the misinterpretation of statistical analyses. The following points are discussed: a) the general importance of biostatistics in the development and validation of alternative tests; b) optimisation of study designs; c) statistical characterisation and processing of toxicological data; and d) the analysis of relationships which may exist between data obtained from various tests. In particular, the establishment of appropriate prediction models which are able to predict the toxic effects likely to occur in vivo from the results obtained in an in vitro test system is discussed. The members of the Task Force hope that this report will help to stimulate discussions among biostatisticians and experimental toxicologists about how the proper application of biostatistical methods can improve the design and evaluation of alternative toxicological methods.

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Experimental Models of Hepatocellular Carcinoma—A Preclinical Perspective

Cancers ◽

10.3390/cancers13153651 ◽

2021 ◽

Vol 13 (15) ◽

pp. 3651

Author(s):

Alexandru Blidisel ◽

Iasmina Marcovici ◽

Dorina Coricovac ◽

Florin Hut ◽

Cristina Adriana Dehelean ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Molecular Mechanisms ◽

Prediction Models ◽

3D Models ◽

Experimental Models ◽

Health Concern ◽

Liver Carcinoma ◽

Tumor Type

Hepatocellular carcinoma (HCC), the most frequent form of primary liver carcinoma, is a heterogenous and complex tumor type with increased incidence, poor prognosis, and high mortality. The actual therapeutic arsenal is narrow and poorly effective, rendering this disease a global health concern. Although considerable progress has been made in terms of understanding the pathogenesis, molecular mechanisms, genetics, and therapeutical approaches, several facets of human HCC remain undiscovered. A valuable and prompt approach to acquire further knowledge about the unrevealed aspects of HCC and novel therapeutic candidates is represented by the application of experimental models. Experimental models (in vivo and in vitro 2D and 3D models) are considered reliable tools to gather data for clinical usability. This review offers an overview of the currently available preclinical models frequently applied for the study of hepatocellular carcinoma in terms of initiation, development, and progression, as well as for the discovery of efficient treatments, highlighting the advantages and the limitations of each model. Furthermore, we also focus on the role played by computational studies (in silico models and artificial intelligence-based prediction models) as promising novel tools in liver cancer research.

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Internal exposure dynamics drive the Adverse Outcome Pathways of synthetic glucocorticoids in fish

Scientific Reports ◽

10.1038/srep21978 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 33

Author(s):

Luigi Margiotta-Casaluci ◽

Stewart F. Owen ◽

Belinda Huerta ◽

Sara Rodríguez-Mozaz ◽

Subramanian Kugathas ◽

...

Keyword(s):

Predictive Power ◽

Adverse Outcome ◽

Plasma Concentrations ◽

Internal Exposure ◽

Adverse Outcome Pathway ◽

Conceptual Tool ◽

Fish Model ◽

Species Specific

Abstract The Adverse Outcome Pathway (AOP) framework represents a valuable conceptual tool to systematically integrate existing toxicological knowledge from a mechanistic perspective to facilitate predictions of chemical-induced effects across species. However, its application for decision-making requires the transition from qualitative to quantitative AOP (qAOP). Here we used a fish model and the synthetic glucocorticoid beclomethasone dipropionate (BDP) to investigate the role of chemical-specific properties, pharmacokinetics, and internal exposure dynamics in the development of qAOPs. We generated a qAOP network based on drug plasma concentrations and focused on immunodepression, skin androgenisation, disruption of gluconeogenesis and reproductive performance. We showed that internal exposure dynamics and chemical-specific properties influence the development of qAOPs and their predictive power. Comparing the effects of two different glucocorticoids, we highlight how relatively similar in vitro hazard-based indicators can lead to different in vivo risk. This discrepancy can be predicted by their different uptake potential, pharmacokinetic (PK) and pharmacodynamic (PD) profiles. We recommend that the development phase of qAOPs should include the application of species-specific uptake and physiologically-based PK/PD models. This integration will significantly enhance the predictive power, enabling a more accurate assessment of the risk and the reliable transferability of qAOPs across chemicals.

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Genotoxic and Chemopreventive Effects of Vochysia divergens Leaves (Pantanal, Brazil)

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2018/6596142 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7

Author(s):

Pollyanna Francielli de Oliveira ◽

Suzana Amorim Mendes ◽

Nathália Oliveira Acésio ◽

Luis Claudio Kellner Filho ◽

Leticia Pereira Pimenta ◽

...

Keyword(s):

Protective Effect ◽

Skin Diseases ◽

Chemical Constituents ◽

Test System ◽

Negative Control ◽

Control Group ◽

Xtt Assay ◽

Vochysia Divergens

The medicinal plant Vochysia divergens is a colonizing tree species of the Pantanal, a unique and little explored wetland region in Brazil. This species is used in folk medicine as syrups and teas to treat respiratory infections, digestive disorders, asthma, scarring, and skin diseases. The objectives of this study were to evaluate the antioxidant, cytotoxic, and genotoxic potential of the ethanolic extract of Vochysia divergens leaves (VdE), as well as the influence of VdE and its major component (the flavone 3′,5-dimethoxy luteolin-7-O-β-glucopyranoside; 3′5 DL) on MMS-induced genotoxicity. The extract significantly reduced the viability of V79 cells in the colorimetric XTT assay at concentrations ≥ 39 μg/mL. A significant increase in micronucleus frequencies was observed in V79 cell cultures treated with VdE concentrations of 160 and 320 μg/mL. However, animals treated with the tested doses of VdE (500, 1000, and 2000 mg/kg b.w.) exhibited frequencies that did not differ significantly from those of the negative control group, indicating the absence of genotoxicity. The results also showed that VdE was effective in reducing MMS-induced genotoxicity at concentrations of 20, 40, and 80 μg/mL in the in vitro test system and at a dose of 15 mg/kg b.w. in the in vivo test system. Its major component 3′5 DL exerted no protective effect, suggesting that it is not responsible for the effect of the extract. The results of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed that VdE was able to scavenge 92.6% of free radicals. In conclusion, the results suggest that the protective effect of VdE may be related, at least in part, to the antioxidant activity of its chemical constituents.

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Prediction of in Vivo Cytotoxicity of Chemotherapeutic Agents by Their Effect on Malignant Leukocytes in Vitro

Blood ◽

10.1182/blood.v30.2.176.176 ◽

1967 ◽

Vol 30 (2) ◽

pp. 176-188 ◽

Cited By ~ 19

Author(s):

MARTIN J. CLINE

Keyword(s):

Test System ◽

Chemotherapeutic Agents ◽

Response To Treatment ◽

In Vitro Test ◽

Malignant Cells ◽

Vitro Test ◽

In Vitro Effects ◽

In Vivo Cytotoxicity

Abstract In order to develop a test system for predicting the response to chemotherapeutic agents, leukocytes from patients with leukemia and leukolymphosarcoma were cultured in vitro and the effect of several drugs on the incorporation of H3-uridine into ribonucleic acid was measured. Cortisol, vincristine and cytosine arabinoside at concentrations near the therapeutic range produced inhibition of H3-uridine incorporation in sensitive leukocytes. The in vitro effects of 6-mercaptopurine and methotrexate were variable. In 39 trials on 25 patients with leukemia or lymphosarcoma, the in vitro test was used successfully to predict the response to treatment with prednisone and vincristine. It was concluded that the in vitro test system can predict the in vivo cytotoxicity of certain drugs for malignant cells, although it cannot be used to predict the likelihood of the induction of remissions with these drugs.

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IS IT POSSIBLE TO IDENTIFY HUMAN PLATELETS IN VITRO AS BEING DESENSITIZED TO PLATELET ACTIVATING FACTOR (PAF-ACETHER,PAF) IN VIVO?

10.1055/s-0038-1643484 ◽

1987 ◽

Author(s):

Cs Perger ◽

A von Felten

Keyword(s):

Platelet Activating Factor ◽

Test System ◽

Human Platelets ◽

Vacuum Filtration ◽

Reversible Aggregation ◽

The Individual ◽

20 Nm ◽

And Control

PAF is suggested to be of pathophysiological importance in a variety of diseases. Since platelets exhibit a reduced sensitivity to PAF after a contact with this agent, this behavior may be used as indicator of PAF released into the circulation. In extrinsic asthma, platelets show a diminished reaction to PAF after exposition of the patients to the antigen compared to their own platelets before exposition (Beer and von Felten, Adv. Inflamm. Res. 10:323,1986). We were therefore looking for a test system indicating directly whether platelets had been in contact with PAF.Preparation of PAF-desensitized platelets: Citrated PRP was placed in a cuvette of an aggregometer, and PAF was added in 10 portions at intervals of 10 sec (37oc, constant stirring) to a final concentration of 10 to 100 nM, depending on the individual sensitivity of each platelet preparation. Therby, only a minimal, completely reversible aggregation was registered without any release of serotonin (ST) or 3-thromboglobulin (BTG). Control platelets were pretreated with buffer instead of PAF. Both platelets preparations were kept at 37°C for 45 min. Whereas control platelets showed a secondary aggregation to PAF (5x conc. used for desensitization), PAF-pretreated piatelets were only reversibly aggregated.Sensitivity of PAF-desensitized and control platelets to other platelet agonists: No difference in aggregation, ST-or BTG-relea-se was observed after stimulation with several concentrations of ADP, collagen and arachidonate (p>0.05,n= 41).Binding of 3H-PAF to platelets: PAF-desensitized and control platelets were separated from plasma by filtration through sepharose CL-2B (Pharmacia) in hepes-buffered Tyrode’s solution. After incubation with 3H-PAF, platelets were washed on Whatman 934-AH filters (vacuum filtration). On desensitized and control platelets, we found 175±48 (mean±sd) and 231±70 3H-PAF molecules / platelet respectively after incubation with 5 nM ^h-PAF, 399±36 and 504±66 ^H-PAF molecules / platelet after incubation with 20 nM. In spite of a statistically significant reduction of PAF-binding after desensitization (p<0.01),the variability of PAF-binding between platelets of different individuals is too high to allow a discrimination of normal from PAF-desensitized platelets.

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Multiple-endpoint in vitro carcinogenicity test in human cell line TK6 distinguishes carcinogens from non-carcinogens and highlights mechanisms of action

Archives of Toxicology ◽

10.1007/s00204-020-02902-3 ◽

2020 ◽

Author(s):

Katherine E. Chapman ◽

Eleanor C. Wilde ◽

Fiona M. Chapman ◽

Jatin R. Verma ◽

Ume-Kulsoom Shah ◽

...

Keyword(s):

Cell Line ◽

Human Cell Line ◽

Test System ◽

In Vitro Tests ◽

Correct Identification ◽

In Vitro Test ◽

Human Lymphoblastoid Cell ◽

Carcinogenic Potential

Abstract Current in vitro genotoxicity tests can produce misleading positive results, indicating an inability to effectively predict a compound’s subsequent carcinogenic potential in vivo. Such oversensitivity can incur unnecessary in vivo tests to further investigate positive in vitro results, supporting the need to improve in vitro tests to better inform risk assessment. It is increasingly acknowledged that more informative in vitro tests using multiple endpoints may support the correct identification of carcinogenic potential. The present study, therefore, employed a holistic, multiple-endpoint approach using low doses of selected carcinogens and non-carcinogens (0.001–770 µM) to assess whether these chemicals caused perturbations in molecular and cellular endpoints relating to the Hallmarks of Cancer. Endpoints included micronucleus induction, alterations in gene expression, cell cycle dynamics, cell morphology and bioenergetics in the human lymphoblastoid cell line TK6. Carcinogens ochratoxin A and oestradiol produced greater Integrated Signature of Carcinogenicity scores for the combined endpoints than the “misleading” in vitro positive compounds, quercetin, 2,4-dichlorophenol and quinacrine dihydrochloride and toxic non-carcinogens, caffeine, cycloheximide and phenformin HCl. This study provides compelling evidence that carcinogens can successfully be distinguished from non-carcinogens using a holistic in vitro test system. Avoidance of misleading in vitro outcomes could lead to the reduction and replacement of animals in carcinogenicity testing.

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A phosphorylation site in brain and the delayed neurotoxic effect of some organophosphorus compounds

Biochemical Journal ◽

10.1042/bj1110487 ◽

1969 ◽

Vol 111 (4) ◽

pp. 487-495 ◽

Cited By ~ 110

Author(s):

M K Johnson

Keyword(s):

Organophosphorus Compounds ◽

Specific Binding ◽

Phosphorylation Site ◽

Test System ◽

Binding Activity ◽

Specific Component ◽

Esterase Inhibitors ◽

Brain And Spinal Cord

1. It is proposed that part of a neurotoxic dose of di-isopropyl phosphorofluoridate will be covalently bound in vivo to a specific component in the brain and spinal cord as the initial biochemical event in the genesis of the lesion. 2. A test system in vitro was devised that removes many di-isopropyl phosphorofluoridate-binding sites and indicates that the specific component may be a protein present in brain at a concentration comparable with that of the cholinesterases. 3. The site was found to be present and capable of binding di-isopropyl phosphorofluoridate in vitro in brain samples taken from either normal hens or those dosed with organophosphorus esterase inhibitors that are not neurotoxic. 4. Very little of the specific binding activity was found in brain samples from hens pre-dosed with a variety of neurotoxic organophosphorus compounds. 5. A solubilized preparation of the active brain component was obtained, suitable for further purification and study.

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The molecular structure and lubricating activity of lubricin isolated from bovine and human synovial fluids

Biochemical Journal ◽

10.1042/bj2250195 ◽

1985 ◽

Vol 225 (1) ◽

pp. 195-201 ◽

Cited By ~ 198

Author(s):

D A Swann ◽

F H Silver ◽

H S Slayter ◽

W Stafford ◽

E Shore

Keyword(s):

Amino Acid ◽

Synovial Fluid ◽

Test System ◽

Sedimentation Equilibrium ◽

Human Knee ◽

Synovial Fluids ◽

Molecular Masses ◽

Friction Measurements

Lubricin was isolated from bovine ankle, metacarpophalangeal and knee and human knee synovial fluids. The lubricins isolated from the bovine joint fluids had the same amino acid and carbohydrate compositions, but differences were observed in the relative molecular masses. The Mr values of bovine metacarpophalangeal and ankle lubricin determined by light-scattering measurements were about 200 000, whereas values of 132 000 and 143 000 were obtained for the bovine knee lubricin. The human knee lubricin had a similar carbohydrate composition to bovine knee lubricin except for the higher glucosamine content, and the amino acid composition differed slightly. The human sample had a lower glutamic acid content and a leucine/isoleucine ratio of 2:1 compared with 1:1 in the bovine. The Mr value of the human knee lubricin (166 000) was also lower than that of the bovine metacarpophalangeal and ankle samples. The Mr value of the bovine knee lubricin determined by sedimentation-equilibrium measurements was 171 000. The length measurements determined by electron microscopy and also the sedimentation measurements showed considerable polydispersity and indicate that the degree of extension of lubricin molecules can vary. Friction measurements showed that the human knee synovial-fluid lubricin had equivalent lubricating ability in a test system in vitro to that observed for lubricin isolated from normal bovine synovial fluids. The lubricating ability of lubricin was concentration-dependent, and each lubricin sample was able to act as a lubricant in vitro in an equivalent manner to whole synovial fluid at concentrations that are thought to occur in vivo.

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