Publication Categories in Toxicologic Pathology.

Toxicologic Pathology is the official journal of the Society of Toxicologic Pathology (STP), the British Society of Toxicological Pathology, and the European STP (ESTP). Toxicologic Pathology publishes articles related to topics in various aspects of toxicologic pathology such as anatomic pathology, clinical pathology, experimental pathology, and biomarker research. Publications include society-endorsed Best Practice/Position and Points to Consider publications and ESTP Expert Workshop articles that are relevant to toxicologic pathology and scientific regulatory processes, Opinion articles under the banner of the STP Toxicologic Pathology Forum, Original Articles, Review Articles (unsolicited/contributed, mini, and invited), Brief Communications, Letters to the Editor, Meeting Reports, and Book Reviews. This article provides details on the various publication categories in Toxicologic Pathology and will serve as a reference for authors and readers.

Effects of lersivirine on canine and rodent thyroid function.

Lersivirine is a nonnucleoside reverse transcriptase inhibitor (NNRTI) being developed for the treatment of HIV-1 infection. Like other NNRTIs, lersivirine is a potent enzyme inducer in rodents capable of inducing a number of hepatic enzymes including those involved in its own metabolism. Preclinically lersivirine has been associated with hepatocellular hypertrophy and thyroid gland follicular cell hypertrophy in rats, mice, and dogs. In rodents, we show that development of thyroid hypertrophy is related to the classic mechanism, namely increased thyroxine (T4) clearance secondary to induction of uridine-diphosphoglucuronosyltransferase (UDPGT) in the liver and a resulting increase in thyroid-stimulating hormone. Similarly, lersivirine-exposed dogs exhibit a significant increase in hepatic UDPGT enzyme activity along with increased T4 clearance although clear effects on serum thyroid hormone levels were less apparent. These effects on thyroid hormonal clearance in the dog suggest that thyroid gland hypertrophy in this species is due to the same mechanism shown to occur in rodents although, as expected, dogs better adapt to these effects and therefore maintain relatively normal thyroid hormonal balance. It is also notable that the minimal thyroid follicular hypertrophy that occurs in dogs does not progress as is seen in rodents. As is the case with rodents, these adaptive changes in the dog are not considered indicative of a human health risk.

Neuropathology standards: what constitutes an optimal histomorphologic evaluation of the nervous system in general toxicity studies.

The identification of neurotoxicity is a critical issue in drug development, and toxicologic pathologists play an important role in this effort. Neuropathology is a specialized area of toxicologic pathology in which a substantial number of nonroutine techniques and methods have been developed, and there are undoubtedly many instances in which these specialized procedures have helped characterize a neuropathologic lesion. Routine histopathologic methods employed in general toxicologic pathology studies are needed to identify the complete range of possible neuropathologic changes; once identified, many of these changes can be better defined by specialized techniques, such as immunohistochemistry, to confirm cell types involved. Sometimes, when neurotoxicity is expected, dedicated studies can be designed a priori and optimized for detection of the anticipated effects. However, when neurotoxicity arises unexpectedly or there is uncertainty around the potential for neurotoxicity, the decision of what to do can become more difficult. Recommendations to go ahead and perform the "optimal" study design that would accommodate all the potentially useful specialized techniques for characterizing a neuropathologic change are sometimes not practical and can be unnecessary and potentially detrimental to other end points in the study. In addition, there is not always agreement on when specialized techniques would be required and which ones should be used when necessary. Two techniques in particular that are commonly recommended to help facilitate the detection of neuropathologic lesions are perfusion fixation and the Fluoro-Jade stain.

K-ras mutations in lung tumors and tumors from other organs are consistent with a common mechanism of ethylene oxide tumorigenesis in the B6C3F1 mouse.

Ethylene oxide is a multisite carcinogen in rodents and classified as a human carcinogen by the National Toxicology Program. In 2-year mouse studies, ethylene oxide (EO) induced lung, Harderian gland (HG), and uterine neoplasms. We evaluated representative EO-induced and equivalent spontaneous neoplasms for K-ras mutations in codons 12, 13, and 61. K-ras mutations were identified in 100% (23/23) of the EO-induced lung neoplasms and 25% (27/108) of the spontaneous lung neoplasms. Codon 12 G to T transversions were common in EO-induced lung neoplasms (21/23) but infrequent in spontaneous lung neoplasms (1/108). K-ras mutations were found in 86% (18/21) of the EO-induced HG neoplasms and 7% (2/27) of the spontaneous HG neoplasms. Codon 13 G to C and codon 12 G to T transversions were predominant in the EO-induced HG neoplasms but absent in spontaneous HG neoplasms (0/27). K-ras mutations occurred in 83% (5/6) of the EO-induced uterine carcinomas and all were codon 13 C to T transitions. These data show a strong predilection for development of K-ras mutations in EO-induced lung, Harderian gland, and uterine neoplasms. This suggests that EO specifically targets the K-ras gene in multiple tissue types and that this event is a critical component of EO-induced tumorigenesis.

Cardiovascular involvement in 8 dogs with blastomyces dermatitidis infection.

BACKGROUND: Blastomycosis is a common systemic fungal infection in dogs. HYPOTHESIS: Dogs with cardiovascular involvement may have abnormalities in electrical conduction and valvular function, and may have a worse prognosis. ANIMALS: Eight client-owned animals. METHODS: Dogs with cardiovascular lesions caused by blastomycosis were identified from retrospective evaluation of medical records. RESULTS: Five dogs had de novo infections and 3 had recurrences of previously treated infections. Harsh labored breathing, lethargy, and anorexia were the most common historic complaints. Three dogs had syncope. Physical examination and clinicopathologic data were typical of blastomycosis and included dyspnea, increased lung sounds, and lethargy. In addition, 3 dogs had heart murmurs and 1 had a third-degree atrioventricular block. Four dogs had myocarditis and 2 had pericarditis or epicarditis. Two dogs had cardiac signs attributed to extracardiac compression by fungal granulomas and clinical signs were relieved by treatment. Half of the remaining 6 dogs were euthanized; 2 of these were not treated. Of the remaining 3 dogs, 1 dog died acutely while sleeping; the second died intraoperatively during an attempt to place an epicardial pacemaker; and the third had Blastomyces-induced endocarditis and died of heart failure. CONCLUSIONS AND CLINICAL IMPORTANCE: Blastomycosis should be considered in the differential diagnosis of dogs from endemic areas with inflammatory myocarditis, heart block, heart base or intracardiac mass lesions, syncope, or endocarditis.

Frequent p53 and H-ras mutations in benzene- and ethylene oxide-induced mammary gland carcinomas from B6C3F1 mice.

Benzene and ethylene oxide are multisite carcinogens in rodents and classified as human carcinogens by the National Toxicology Program. In 2-year mouse studies, both chemicals induced mammary carcinomas. We examined spontaneous, benzene-, and ethylene oxide-induced mouse mammary carcinomas for p53 protein expression, using immunohistochemistry, and p53 (exons 5-8) and H-ras (codon 61) mutations using cycle sequencing techniques. p53 protein expression was detected in 42% (8/19) of spontaneous, 43% (6/14) of benzene-, and 67% (8/12) of ethylene oxide-induced carcinomas. However, semiquantitative evaluation of p53 protein expression revealed that benzene- and ethylene oxide-induced carcinomas exhibited expression levels five- to six-fold higher than spontaneous carcinomas. p53 mutations were found in 58% (7/12) of spontaneous, 57% (8/14) of benzene-, and 67% (8/12) of ethylene oxide-induced carcinomas. H-ras mutations were identified in 26% (5/19) of spontaneous, 50% (7/14) of benzene-, and 33% (4/12) of ethylene oxide-induced carcinomas. When H-ras mutations were present, concurrent p53 mutations were identified in 40% (2/5) of spontaneous, 71% (5/7) of benzene-, and 75% (3/4) of ethylene oxide-induced carcinomas. Our results demonstrate that p53 and H-ras mutations are relatively common in control and chemically induced mouse mammary carcinomas although both chemicals can alter the mutational spectra and more commonly induce concurrent mutations.

Spontaneous and irradiation-induced tumor susceptibility in BRCA2 germline mutant mice and cooperative effects with a p53 germline mutation.

Mutations in both p53 and BRCA2 are commonly seen together in human tumors suggesting that the loss of both genes enhances tumor development. To elucidate this interaction in an animal model, mice lacking the carboxy terminal domain of Brca2 were crossed with p53 heterozygous mice. Females from this intercross were then irradiated with an acute dose of 5 Gy ionizing radiation at 5 weeks of age and compared to nonirradiated controls. We found decreased survival and timing of tumor onsets, and significantly higher overall tumor incidences and prevalence of particular tumors, including stomach tumors and squamous cell carcinomas, associated with the homozygous loss of Brca2, independent of p53 status. The addition of a p53 mutation had a further impact on overall survival, incidence of osteosarcomas and stomach tumors, and tumor latency. The spectrum of tumors observed for this Brca2 germline mouse model suggest that it faithfully recapitulates some human disease phenotypes associated with BRCA2 loss. In addition, these findings include extensive in vivo data demonstrating that germline Brca2 and p53 mutations cooperatively affect animal survivals, tumor susceptibilities, and tumor onsets.

Mutant Brca2/p53 mice exhibit altered radiation responses in the developing mammary gland.

Appropriate balance between proliferation and apoptosis is critical for mammary gland development and is often altered during tumorigenesis. Carcinogens like radiation induce DNA damage and activate protective responses such as cell cycle arrest and apoptosis. We used mice carrying Brca2(-/-) and/or p53(-/-) mutations to evaluate the individual and combined effects of these genes on cell proliferation and apoptosis in the developing mammary gland. Mice were exposed to 5Gy of radiation or chamber exposure (controls) followed by injection with BrdU. Mammary glands were collected 6 h post-radiation exposure and evaluated for proliferation (BrdU) and apoptosis (TUNEL) in terminal end buds (TEB) and ducts. Under control conditions, the Brca2 mutation reduced proliferation and apoptosis in TEB but not ducts, whereas the p53 mutation reduced apoptosis in TEB and ducts but did not influence proliferation. Despite these alterations in proliferation and/or apoptosis, neither mutation, either individually or combined, significantly altered the overall balance between the two as measured by the proliferation to apoptosis ratio (growth index). Following irradiation, the Brca2 mutation had no significant effect on proliferation or apoptosis, whereas the p53 mutation resulted in reduced apoptosis in TEB and ducts but did not significantly influence proliferation. Neither mutation by itself altered the growth index in the TEB after irradiation although combined Brca2/p53 mutation caused significantly increased proliferation, reduced apoptosis, and an elevated growth index in TEB and ducts. These results reveal both independent and collaborative growth regulatory roles for Brca2 and p53 under normal and adverse environmental conditions. Additionally, we demonstrate the importance of gene-environment interactions by showing that Brca2- and p53-deficient mice can compensate for their genetic deficiencies under control conditions but not after exposure to radiation. We also demonstrate distinct spatial differences in the cellular functions of Brca2 and p53 and show that combined mutation of both genes is more detrimental than loss of either gene alone.

Changes in global gene and protein expression during early mouse liver carcinogenesis induced by non-genotoxic model carcinogens oxazepam and Wyeth-14,643.

We hypothesized that the mouse liver tumor response to non-genotoxic carcinogens would involve some common early gene and protein expression changes that could ultimately be used to predict chemical hepatocarcinogenesis. In order to identify a panel of genes to test, we analyzed global differences in gene and protein expression in livers from B6C3F1 mice following dietary treatment with two rodent carcinogens, the benzodiazepine anti-anxiety drug oxazepam (2500 p.p.m.) and the hypolipidemic agent Wyeth (Wy)-14,643 (500 p.p.m.) compared with livers from untreated mice. Male mice were exposed for 2 weeks and 1, 3 or 6 months to oxazepam or Wy-14,643 in an age-matched study design. By histopathological evaluation, no liver preneoplastic foci or tumors were detected at 6 months in treated or control groups. By cDNA microarray analysis [NIEHS Mouse Chip (8700 genes); n = 3 individual livers/group, four hybridizations/sample], expression of 36 genes or 220 genes were changed relative to control livers following 6 months of oxazepam or Wy-14,643 treatment, respectively. To obtain a more comprehensive picture of gene/protein expression changes, we also conducted a proteomics study by 2D-gel electrophoresis followed by matrix assisted laser desorption/ionization-mass spectrometry on cytoplasmic, nuclear, and microsomal subcellular fractions of the same liver samples utilized for the cDNA microarray analysis. Real-time PCR, western blot analysis and immunohistochemistry were utilized for validation and to expand the results to other time points. Cyp2b20, growth arrest- and damage-inducible gene beta (Gadd45beta), tumor necrosis factor alpha-induced protein 2 and insulin-like growth factor binding protein 1 (Igfbp5) genes and proteins were upregulated by oxazepam, and Cyp2b20, Cyclin D1, proliferating cell nuclear antigen, Igfbp5, Gadd45beta and cell death-inducing DNA fragmentation factor alpha subunit-like effector A exhibited higher expression after Wy-14,643 treatment. Most of these genes/proteins were also deregulated at 2 weeks. There appeared to be more distinct than common changes in the expression of carcinogenesis-related genes/proteins between the two compounds, suggesting that the major carcinogenic pathways are different for these compounds and may be distinct for different chemical classes.

Loss of expression and altered localization of KAI1 and CD9 protein are associated with epithelial ovarian cancer progression.

OBJECTIVE: Impairment of cell adhesion plays a vital role in tumor progression. E- and N-cadherin, CD9, and KAI1 are all adhesion molecules that have been implicated in the progression of several different tumor types. To help explain the potential role these adhesion molecules have in ovarian cancer, comparisons were made between expression patterns in normal ovary and various grades of primary and metastatic epithelial ovarian cancers. METHODS: Thirty-two primary and 8 metastatic human ovarian epithelial carcinomas and 18 samples of normal ovarian tissue were examined for adhesion molecule expression using immunohistochemistry. RESULTS: KAI1 and CD9 revealed an inverse relationship between tumor grade and expression levels, characterized by high expression in low-grade tumors and low expression in high-grade tumors and metastases. KAI1 and CD9 also demonstrated a shift in cellular localization from the membrane in grade 1 tumors to the cytoplasm in grade 3 tumors. N-cadherin expression showed a positive trend between expression levels and tumor grade. E-cadherin expression varied little between different tumor grades and metastases. Inclusion cysts (n = 6) and surface invaginations often strongly expressed KAI1, CD9, and E-cadherin. KAI1 expression was variable in ovarian follicles and corpora lutea depending on their stage of development. CONCLUSIONS: Although sample size is limited, these findings suggest that progression of ovarian epithelial carcinomas is associated with down-regulation and altered cellular localization of KAI1 and CD9. In addition, variable KAI1 expression during follicular and luteal development suggests that it has a physiological function in the ovary. Further investigation will be needed to see if it is also regulated this way during progression of ovarian cancers.