Effect of Chemical Mutagens and Carcinogens on Gene Expression Profiles in Human TK6 Cells

Characterization of toxicogenomic signatures of carcinogen exposure holds significant promise for mechanistic and predictive toxicology. In vitro transcriptomic studies allow the comparison of the response to chemicals with diverse mode of actions under controlled experimental conditions. We conducted an in vitro study in TK6 cells to characterize gene expression signatures of exposure to 15 genotoxic carcinogens frequently used in European industries. We also examined the dose-responsive changes in gene expression, and perturbation of biochemical pathways in response to these carcinogens. TK6 cells were exposed at 3 dose levels for 24 h with and without S9 human metabolic mix. Since S9 had an impact on gene expression (885 genes), we analyzed the gene expression data from cells cultures incubated with S9 and without S9 independently. The ribosome pathway was affected by all chemical-dose combinations. However in general, no similar gene expression was observed among carcinogens. Further, pathways, i.e. cell cycle, DNA repair mechanisms, RNA degradation, that were common within sets of chemical-dose combination were suggested by clustergram. Linear trends in dose–response of gene expression were observed for Trichloroethylene, Benz[a]anthracene, Epichlorohydrin, Benzene, and Hydroquinone. The significantly altered genes were involved in the regulation of (anti-) apoptosis, maintenance of cell survival, tumor necrosis factor-related pathways and immune response, in agreement with several other studies. Similarly in S9+ cultures, Benz[a]pyrene, Styrene and Trichloroethylene each modified over 1000 genes at high concentrations. Our findings expand our understanding of the transcriptomic response to genotoxic carcinogens, revealing the alteration of diverse sets of genes and pathways involved in cellular homeostasis and cell cycle control

Up-regulation of cell cycle arrest protein BTG2 correlates with increased overall survival in breast cancer, as detected by immunohistochemistry using tissue microarray

<p>Abstract</p> <p>Background</p> <p>Previous studies have shown that the <it>ADIPOR1</it>, <it>ADORA1</it>, <it>BTG2 </it>and <it>CD46 </it>genes differ significantly between long-term survivors of breast cancer and deceased patients, both in levels of gene expression and DNA copy numbers. The aim of this study was to characterize the expression of the corresponding proteins in breast carcinoma and to determine their correlation with clinical outcome.</p> <p>Methods</p> <p>Protein expression was evaluated using immunohistochemistry in an independent breast cancer cohort of 144 samples represented on tissue microarrays. Fisher's exact test was used to analyze the differences in protein expression between dead and alive patients. We used Cox-regression multivariate analysis to assess whether the new markers predict the survival status of the patients better than the currently used markers.</p> <p>Results</p> <p>BTG2 expression was demonstrated in a significantly lower proportion of samples from dead patients compared to alive patients, both in overall expression (<it>P </it>= 0.026) and cell membrane specific expression (<it>P </it>= 0.013), whereas neither ADIPOR1, ADORA1 nor CD46 showed differential expression in the two survival groups. Furthermore, a multivariate analysis showed that a model containing BTG2 expression in combination with HER2 and Ki67 expression along with patient age performed better than a model containing the currently used prognostic markers (tumour size, nodal status, HER2 expression, hormone receptor status, histological grade, and patient age). Interestingly, BTG2 has previously been described as a tumour suppressor gene involved in cell cycle arrest and p53 signalling.</p> <p>Conclusions</p> <p>We conclude that high-level BTG2 protein expression correlates with prolonged survival in patients with breast carcinoma.</p

Disease-associated CAG·CTG triplet repeats expand rapidly in non-dividing mouse cells, but cell cycle arrest is insufficient to drive expansion

Artículo científico -- Universidad de Costa Rica, Instituto de Investigaciones en Salud. 2014Genetically unstable expanded CAG·CTG trinucleotide repeats are causal in a number of human disorders, including Huntington disease and myotonic dystrophy type 1. It is still widely assumed that DNA polymerase slippage during replication plays an important role in the accumulation of expansions. Nevertheless, somatic mosaicism correlates poorly with the proliferative capacity of the tissue and rates of cell turnover, suggesting that expansions can occur in the absence of replication. We monitored CAG·CTG repeat instability in transgenicmouse cells arrested by chemical or genetic manipulation of the cell cycle and generated unequivocal evidence for the continuous accumulation of repeat expansions in non-dividing cells. Importantly, the rates of expansion in non-dividing cells were at least as high as those of proliferating cells. These data are consistent with amajor role for cell division-independent expansion in generating somatic mosaicism in vivo. Although expansions can accrue in non-dividing cells, we also show that cell cycle arrest is not sufficient to drive instability, implicating other factors as the key regulators of tissue-specific instability. Our data reveal that de novo expansion events are not limited to S-phase and further support a cell divisionindependent mutational pathway.Universidad de Costa Rica. Instituto de Investigaciones en SaludInstitute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, GlasgowParis Descartes-Sorbonne Paris Cité UniversityUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones en Salud (INISA

B Cell Translocation Gene 2 Enhances Susceptibility of HeLa Cells to Doxorubicin-induced Oxidative Damage*

BTG2/TIS21/PC3 (B cell translocation gene 2) has been known as a p53 target gene and functions as a tumor suppressor in carcinogenesis of thymus, prostate, kidney, and liver. Although it has been known that the expression of BTG2/TIS21/PC3 is induced during chemotherapy-mediated apoptosis in cancer cells, a role of BTG2/TIS21/PC3 in cell death remains to be elucidated. In this study, the mechanism and role of BTG2 involved in the enhancement of doxorubicin (DOXO)-induced cell death were examined. Treatment of HeLa cells with DOXO revealed apoptotic phenomena, such as chromatin condensation and cleavage of poly(ADP-ribose) polymerase and lamin A/C with concomitant increase of BTG2/TIS21/PC3 expression. Employing infections of Ad-TIS21 virus and lentivirus with short hairpin RNA to BTG2, the effect of BTG2/TIS21/PC3 on the DOXO-induced apoptosis of HeLa cells and liver cancer cells was evaluated. Not only short hairpin RNA-BTG2 but also N-acetyl-l-cysteine significantly reduced the DOXO-induced HeLa cell death and generation of H2O2. Moreover, forced expression of BTG2/TIS21/PC3 using adenoviral vector augmented DOXO-induced cancer cell death concomitantly with increase of manganese-superoxide dismutase but not catalase, CuZnSOD, and glutathione peroxidase 1. The increased apoptosis by forced expression of BTG2/TIS21/PC3 could be inhibited by N-acetyl-l-cysteine and polyethylene glycol-catalase. These results therefore suggest that BTG2/TIS21/PC3 works as an enhancer of DOXO-induced cell death via accumulation of H2O2 by up-regulating manganese-superoxide dismutase without any other antioxidant enzymes. In summary, BTG2/TIS21/PC3 enhances cancer cell death by accumulating H2O2 via imbalance of the antioxidant enzymes in response to chemotherapy