Estrogens and genomic instability in human cancer cells-involvement of Src/Raf/Erk signaling in micronucleus formation by estrogenic chemicals

This article is available open access through the publisher’s website. Copyright @ 2008 The Authors.Reports of the ability of estrogenic agents such as 17β-estradiol (E2), estriol (E3) and bisphenol A (BPA) to induce micronuclei (MN) in MCF-7 breast cancer cells have prompted us to investigate whether these effects are linked to activation of the estrogen receptor (ER) α. Coadministration of tamoxifen and the pure ER antagonist ICI 182 780 to cells treated with E2 and E3 did not lead to significant reductions in micronucleus frequencies. Since these antiestrogens interfere with the transcriptional activity of the ER and block promotion of ER-dependent gene expression, it appears that this process is not involved in micronucleus formation. However, ER activation also triggers rapid signaling via the Src/Raf/extracellular signal-regulated kinase (Erk) pathway. When MCF-7 cells were exposed to E2 and BPA in combination with the specific kinase inhibitors pyrazolopyrimidine and 2′-amino-3′-methoxyflavone, reductions in micronucleus frequencies occurred. These findings suggest that the Src/Raf/Erk pathway plays a role in micronucleus formation by estrogenic agents. Enhanced activation of the Src/Raf/Erk cascade disturbs the localization of Aurora B kinase to kinetochores, leading to a defective spindle checkpoint with chromosome malsegregation. Using antikinetochore CREST antibody staining, a high proportion of micronucleus containing kinetochores was observed, indicating that such processes are relevant to the induction of MN by estrogens. Our results suggest that estrogens induce MN by causing improper chromosome segregation, possibly by interfering with kinase signaling that controls the spindle checkpoint, or by inducing centrosome amplification. Our findings may have some relevance in explaining the effects of estrogens in the later stages of breast carcinogenesis.European Commissio

ECVAM retrospective validation of in vitro micronucleus test (MNT)

In the past decade several studies comparing the in vitro chromosome aberration test (CAT) and the in vitro micronucleus test (MNT) were performed. A high correlation was observed in each of the studies (>85%); however, no formal validation for the micronucleus in vitro assay had been carried out. Therefore, a working group was established by the European Centre for the Validation of Alternative Methods (ECVAM) to perform a retrospective validation of the existing data, in order to evaluate the validity of the in vitro MNT on the basis of the modular validation approach. The primary focus of this retrospective validation was on the evaluation of the potential of the in vitro MNT as alternative to the standard in vitro CAT. The working group evaluated, in a first step, the available published data and came to the conclusion that two studies [German ring trial, von der Hude, W., Kalweit, S., Engelhardt, G. et al. (2000) In-vitro micronucleus assay with Chinese hamster V79 cells: results of a collaborative study with 26 chemicals. Mutat. Res., 468, 137–163, and SFTG International Collaborative Study, Lorge, E., Thybaud, V., Aardema, M., Oliver, J., Wataka, A., Lorenzon, G. and Marzin, D. (2006) SFTG International Collaborative Study on in-vitro micronucleus test I. General conditions and overall conclusions of the study. Mutat. Res., 607, 13–36] met the criteria for a retrospective validation according to the criteria previously defined by the working group. These two studies were evaluated in depth (including the reanalysis of raw data) and provided the information required for assessing the reliability (reproducibility) of the test. For the assessment of the concordance between the in vitro MNT and the in vitro CAT, additional published data were considered. Based on this retrospective validation, the ECVAM Validation Management Team concluded that the in vitro MNT is reliable and relevant and can therefore be used as an alternative method to the in vitro CAT. Following peer review, these conclusions were formally endorsed by the ECVAM Scientific Advisory Committee

The Building of Verse: Descriptions of Architectural Structures in Roman Poetry

Thesis (Ph.D.)--University of Washington, 2014The Building of Verse: Descriptions of Architectural Structures in Roman Poetry examines depictions of architecture in the literature of the Roman poets Virgil, Ovid, Horace, Propertius, Statius, and Martial. These poets, whose careers span the most significant building programs of ancient Rome, from the Age of Augustus through the Flavian period (ca. 31 BC - AD 96), often build ekphrases, or extended literary descriptions, around residences, temples, and other structures within their poetry. Besides the poetic evidence, I look at Vitruvius' well-known architectural treatise, also written during the building-rich Augustan period, to explore how the poets share in the description of architectural elements and building practices found in his contemporaneous work. I argue that the depictions of architectural structures in these poets are never meant to function solely as settings but rather are intentionally included to more fully develop the poem's vocabulary, imagery, and overall narrative and/or purpose. The first chapter highlights the poetic treatment of caverns and grottoes. It establishes that the poets use a fully developed architectural vocabulary to describe the natural dwellings of monsters and divine beings, as well as the related ideas that these poetically created natural habitats reflect their owners and can even refer to real structures in the Roman world. The second chapter treats both encomiastic and critical depictions of fully developed residences, which serve to identify their owners/inhabitants not only in terms of their aesthetic preferences but also with respect to their social status and their lifestyle. The third chapter turns to temples, hybrid between private (divine) residence and public structure. The poets depict temples in ways that are reflective not of the god or religious ceremony, but rather of how they themselves (i.e., their speakers/narrators) or their characters relate personally and uniquely to the structure, whether they construct or simply view the temple. The fourth chapter focuses on public structures that were used by the people for reasons other than religious worship, such as the curia and baths. It reveals a shift in the nature of poetic architectural descriptions over time, from the late first century B.C.E. writing of Virgil, who uses contemporary architectural terminology to enliven traditional epic structures, to the mid-late first century C.E. poets Statius and Martial, who break generic boundaries in establishing new kinds of poetry to celebrate new, fully Roman architectural structures such as the imperial thermae. Chapter Five serves as a conclusion to the project, considering the formation of cities and their development

Oral exposure to commercially available coal tar-based pavement sealcoat induces murine genetic damage and mutations

Coal tar (CT) is a thick black liquid produced as a by‐product of coal carbonization to produce coke or manufactured gas. It is comprised a complex mixture of polycyclic aromatic compounds, including a wide range of polycyclic aromatic hydrocarbons (PAHs), many of which are genotoxic and carcinogenic. CT is used in some pavement sealants (also known as sealcoat), which are applied to pavement in order to seal and beautify the surface. Human exposure is known to occur not only during application, but also as a result of the weathering process, as elevated levels of PAHs have been found in settled house dust in residences adjacent to CT‐sealed surfaces. In this study we examined the genotoxicity of an extract of a commercially available CT‐based sealcoat in the transgenic Muta™Mouse model. Mice were orally exposed to 3 doses of sealcoat extract daily for 28 days. We evaluated genotoxicity by examining: (1) stable DNA adducts and (2) lacZ mutations in bone marrow, liver, lung, small intestine, and glandular stomach, as well as (3) micronucleated red blood cells. Significant increases were seen for each endpoint and in all tissues. The potency of the response differed across tissues, with the highest frequency of adducts occurring in liver and lung, and the highest frequency of mutations occurring in small intestine. The results of this study are the first demonstration of mammalian genotoxicity following exposure to CT‐containing pavement sealcoat. This work provides in vivo evidence to support the contention that there may be adverse health effects in mammals, and potentially in humans, from exposure to coal tar. Environ. Mol. Mutagen. 57:535–545, 2016. © 2016 Her Majesty the Queen in Right of Canad