Evaluation of the Tg.AC Transgenic Mouse Assay for Testing the Human Carcinogenic Potential of Pharmaceuticals—Practical Pointers, Mechanistic Clues, and New Questions

2002 ◽  
Vol 21 (1) ◽  
pp. 65-79 ◽  
Author(s):  
Frank D. Sistare ◽  
Karol L. Thompson ◽  
Ronald Honchel ◽  
Joseph DeGeorge
Keyword(s):  
Transgenic Mouse ◽  
Genetic Alterations ◽  
Protocol Design ◽  
Mouse Strains ◽  
Impact Study ◽  
Multistage Process ◽  
Short Term ◽  
Tumor Induction ◽  
Carcinogenic Potential ◽  
Testing Protocols

Transgenic mouse strains with genetic alterations known to play a role in the multistage process of carcinogenesis are being used increasingly as models for evaluating the human carcinogenic potential of chemicals and Pharmaceuticals. The Tg.AC transgenic mouse is one of the strains currently being used in such alternative short-term carcinogenicity testing protocols. This review is focused on recent data from studies designed to evaluate this model's ability to discriminate carcinogens from noncarcinogens. Details relating to protocol design that can significantly impact study outcome are described. Data relating to mechanisms of chemical tumor induction in the Tg.AC model are reviewed, and questions have been formulated to encourage research to further guide appropriate future applications of this model.

AhR Activation in Pharmaceutical Development: Applying Liver Gene Expression Biomarker Thresholds to Identify Doses Associated With Tumorigenic Risks in Rats

2019 ◽  
Vol 171 (1) ◽  
pp. 46-55 ◽  
Author(s):  
Chunhua Qin ◽  
Amy G Aslamkhan ◽  
Kara Pearson ◽  
Keith Q Tanis ◽  
Alexei Podtelezhnikov ◽  
...  
Keyword(s):  
Gene Expression ◽  
Gene Expression Signature ◽  
Carcinogenic Risk ◽  
Drug Candidate ◽  
Short Term ◽  
Pharmaceutical Development ◽  
Aryl Hydrocarbon ◽  
Carcinogenic Potential ◽  
Liver Gene ◽  
Dose Levels

Abstract Aryl hydrocarbon receptor (AhR) activation is associated with carcinogenicity of non-genotoxic AhR-activating carcinogens such as 2,3,7,8-tetrachlorodibenzodioxin (TCDD), and is often observed with drug candidate molecules in development and raises safety concerns. As downstream effectors of AhR signaling, the expression and activity of Cyp1a1 and Cyp1a2 genes are commonly monitored as evidence of AhR activation to inform carcinogenic risk of compounds in question. However, many marketed drugs and phytochemicals are reported to induce these Cyps modestly and are not associated with dioxin-like toxicity or carcinogenicity. We hypothesized that a threshold of AhR activation needs to be surpassed in a sustained manner in order for the dioxin-like toxicity to manifest, and a simple liver gene expression signature based on Cyp1a1 and Cyp1a2 from a short-term rat study could be used to assess AhR activation strength and differentiate tumorigenic dose levels from non-tumorigenic ones. To test this hypothesis, short-term studies were conducted in Wistar Han rats with 2 AhR-activating carcinogens (TCDD and PCB126) at minimally carcinogenic and noncarcinogenic dose levels, and 3 AhR-activating noncarcinogens (omeprazole, mexiletine, and canagliflozin) at the top doses used in their reported 2-year rat carcinogenicity studies. A threshold of AhR activation was identified in rat liver that separated a meaningful “tumorigenic-strength AhR signal” from a statistically significant AhR activation signal that was not associated with dioxin-like carcinogenicity. These studies also confirmed the importance of the sustainability of AhR activation for carcinogenic potential. A sustained activation of AhR above the threshold could thus be used in early pharmaceutical development to identify dose levels of drug candidates expected to exhibit dioxin-like carcinogenic potential.

scholarly journals Myeloid cells activate iNKT cells to produce IL-4 in the thymic medulla

2019 ◽  
Vol 116 (44) ◽  
pp. 22262-22268 ◽  
Author(s):  
Haiguang Wang ◽  
Elise R. Breed ◽  
You Jeong Lee ◽  
Lily J. Qian ◽  
Stephen C. Jameson ◽  
...  
Keyword(s):  
Steady State ◽  
Transgenic Mouse ◽  
Cell Receptor ◽  
Interleukin 4 ◽  
Mouse Strains ◽  
Inkt Cells ◽  
Diphtheria Toxin Receptor ◽  
Toxin Receptor ◽  
Thymic Medulla ◽  
Antigen Presenting

Interleukin-4 (IL-4) is produced by a unique subset of invariant natural killer T (iNKT) cells (NKT2) in the thymus in the steady state, where it conditions CD8+ T cells to become “memory-like” among other effects. However, the signals that cause NKT2 cells to constitutively produce IL-4 remain poorly defined. Using histocytometry, we observed IL-4–producing NKT2 cells localized to the thymic medulla, suggesting that medullary signals might instruct NKT2 cells to produce IL-4. Moreover, NKT2 cells receive and require T cell receptor (TCR) stimulation for continuous IL-4 production in the steady state, since NKT2 cells lost IL-4 production when intrathymically transferred into CD1d-deficient recipients. In bone marrow chimeric recipients, only hematopoietic, not stromal, antigen-presenting cells (APCs), provided such stimulation. Furthermore, using different Cre-recombinase transgenic mouse strains to specifically target CD1d deficiency to various APCs, together with the use of diphtheria toxin receptor (DTR) transgenic mouse strains to deplete various APCs, we found that macrophages were the predominant cell to stimulate NKT2 IL-4 production. Thus, NKT2 cells appear to encounter and require different activating ligands for selection in the cortex and activation in the medulla.

Susceptibility Alleles for Aberrant B-1 Cell Proliferation Involved in Spontaneously Occurring B-Cell Chronic Lymphocytic Leukemia in a Model of New Zealand White Mice

Blood ◽  
1998 ◽  
Vol 92 (10) ◽  
pp. 3772-3779
Author(s):  
Yoshitomo Hamano ◽  
Sachiko Hirose ◽  
Akinori Ida ◽  
Masaaki Abe ◽  
Danqing Zhang ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
Autoimmune Disease ◽  
B Cell ◽  
Genetic Alterations ◽  
Lymphocytic Leukemia ◽  
Chromosome 17 ◽  
Mouse Strains ◽  
Autoantibody Production ◽  
Age Related ◽  
Cell Chronic Lymphocytic Leukemia

B-cell chronic lymphocytic leukemia (B-CLL) and autoimmune disease are a related event, and genetic factors are linked to both diseases. As B-CLL is mainly of B-1 cell type that participates in autoantibody production, genetically-determined regulatory abnormalities in proliferation and/or differentiation of B-1 cells may determine their fate. We earlier found that, in H-2–congenic (NZB × NZW) F1 mice, while H-2d/z heterozygosity predisposes to autoimmune disease, H-2z/z homozygosity predisposes to B-CLL. Studies also suggested the involvement of non–H-2-linked NZW allele(s) in leukemogenesis. Using H-2–congenic NZW and B10 mouse strains, their F1 and backcross progeny, we have now identified three major NZW susceptibility loci for abnormal proliferation of B-1 cells, which form the basis of leukemogenesis; one H-2–linked locus on chromosome 17 and the other two non–H-2-linked loci, each on chromosome 13 and chromosome 17. Each susceptibility allele functioned independently, in an incomplete dominant fashion, the sum of effects determining the extent of aberrant B-1 cell frequencies. The development of leukemia was associated with age-related increase in B-1 cell frequencies in the blood. Thus, these alleles probably predispose B-1 cells to accumulate genetic alterations, giving rise to B-CLL. Potentially important candidate genes and correlation of the findings with autoimmune disease are discussed.

scholarly journals Positive Selection of γδ CTL by TL Antigen Expressed in the Thymus

1996 ◽  
Vol 184 (6) ◽  
pp. 2175-2184 ◽  
Author(s):  
Kunio Tsujimura ◽  
Toshitada Takahashi ◽  
Akimichi Morita ◽  
Hitomi Hasegawa-Nishiwaki ◽  
Shigeru Iwase ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Positive Selection ◽  
Transgenic Mouse ◽  
Mouse Strains ◽  
Skin Grafts ◽  
Spleen Cells ◽  
C3h Mice ◽  
Ctl Activity ◽  
Selection Of

To elucidate the function of the mouse TL antigen in the thymus, we have derived two TL transgenic mouse strains by introducing Tlaa-3 of A strain origin with its own promoter onto a C3H background with no expression of TL in the thymus. These transgenic mouse strains, both of which express high levels of Tlaa-3-TL antigen in their thymus, were analyzed for their T cell function with emphasis on cytotoxic T lymphocyte (CTL) generation. A T cell response against TL was induced in Tg.Tlaa-3-1, Tg.Tlaa-3-2, and control C3H mice by skin grafts from H-2Kb/T3b transgenic mice, Tg.Con.3-1, expressing T3b-TL ubiquitously. Spleen cells from mice that had rejected the T3b-TL positive skin grafts were restimulated in vitro with Tg.Con.3-1 irradiated spleen cells. In mixed lymphocyte cultures (MLC), approximately 20% and 15% of Thy-1+ T cells derived from Tg.Tlaa-3-1 and Tg.Tlaa-3-2, respectively, expressed TCRγδ, whereas almost all those from C3H expressed TCRαβ. The MLC from Tg.Tlaa-3-2 and C3H demonstrated high CTL activity against TL, while those from Tg.Tlaa-3-1 had little or none. The generation of γδ CTL recognizing TL in Tg.Tlaa-3-2, but not C3H mice, was confirmed by the establishment of CTL clones. A total of 14 γδ CTL clones were established from Tg.Tlaa-3-2, whereas none were obtained from C3H. Of the 14 γδ CTL clones, 8 were CD8+ and 6 were CD4−CD8− double negative. The CTL activity of all these clones was TL specific and inhibited by anti-TL, but not by anti-H-2 antibodies, demonstrating that they recognize TL directly without antigen presentation by H-2. The CTL activity was blocked by antibodies to TCRγδ and CD3, and also by antibodies to CD8α and CD8β in CD8+ clones, showing that the activity was mediated by TCRγδ and coreceptors. The thymic origin of these γδ CTL clones was indicated by the expression of Thy-1 and Ly-1 (CD5), and also CD8αβ heterodimers in CD8+ clones on their surfaces and by the usage of TCR Vγ4 chains in 12 of the 14 clones. Taken together, these results suggest that Tlaa-3-TL antigen expressed in the thymus engages in positive selection of a sizable population of γδ T cells.

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