Guide for Combining Primary Tumors for Statistical Analysis in Rodent Carcinogenicity Studies

The Tumor Combination Guide was created at the request of the U. S. Food and Drug Administration (FDA) by a Working Group of biopharmaceutical experts from international societies of toxicologic pathology, the Food and Drug Administration (FDA), and members of the Standard for Exchange of Nonclinical Data (SEND) initiative, to assist pharmacology/toxicology reviewers and biostatisticians in statistical analysis of nonclinical tumor data. The guide will also be useful to study and peer review pathologists in interpreting the tumor data. This guide provides a higher-level hierarchy of tumor types or categories correlating the tumor names from the International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) publications with those available in the NEOPLASM controlled terminology (CT) code list in SEND. The version of CT used in a study should be referenced in the nonclinical study data reviewer's guide (SDRG) (section 3.1) of electronic submissions to the FDA. The tumor combination guide instructions and examples are in a tabular format to make informed decisions for combining tumor data for statistical analysis. The strategy for combining tumor types for statistical analysis is based on scientific criteria gleaned from the current scientific literature; as SEND and INHAND terminology and information evolve, this guide will be updated.

Evaluating the sensitivity of newborn rats and newborn hamsters to oncogenic DNA

To evaluate the risk of residual cellular DNA in vaccines manufactured in tumorigenic cell lines, we have been establishing in vivo assays to quantify the oncogenic activity of DNA. We had generated three oncogene-expression plasmids: pMSV-T24-H-ras, which expresses activated H-ras; pMSV-c-myc, which expresses c-myc; and pMSV-T24-H-ras/MSV-c-myc, which expresses both oncogenes. Tumors were induced in mice by pMSV-T24-H-ras plus pMSV-c-myc or by pMSV-T24-H-ras/MSV-c-myc. Because newborn hamsters and newborn rats have been recommended for oncogenicity testing of the DNA from tumorigenic mammalian cell-substrates used for vaccine production, we evaluated their sensitivity. Newborn hamsters and rats were inoculated with different doses of pMSV-T24-H-ras/MSV-c-myc to determine their sensitivity to tumor induction and with the single-oncogene-expression plasmids to determine whether single oncogenes could induce tumors. Newborn rats were more sensitive than newborn hamsters, and activated H-ras but not c-myc induced tumors in newborns of both rodent species. DNA from four cell lines established from tumors induced by pMSV-T24-H-ras/MSV-c-myc was inoculated into newborn rats. Because no tumors were induced by this cellular DNA, which should be optimal as it contains both oncogenes linked and present in several copies, we conclude that available in vivo models are not sensitive enough to detect the oncogenicity of cellular DNA.

A U.S. Government-Coordinated Effort to Leverage Non-Human Primate Data to Facilitate Ebolavirus Vaccine Development

A United States Government (USG) interagency group, the Filovirus Animal Non-Clinical Group (FANG), has been established to support the development of biodefense medical countermeasures (MCMs). As both vaccines and therapeutics are licensed using “non-traditional pathways”, such as the U.S. Food and Drug Administration’s (FDA) Animal Rule (AR), non-human primate (NHP) models and associated assays have been developed and standardized across BSL4 testing sites to evaluate candidate products. Vaccine candidates are evaluated using these NHP models, and through this public–private partnership, a meta-analysis of NHP control data has been conducted and submitted to the FDA as a master file. This is an example of how existing NHP control data can be leveraged in lieu of conducting separate natural history studies at multiple testing facilities to demonstrate the consistency of a standardized animal model for vaccine development. As a result, animal use can be minimized and the duplication of effort avoided, thus reducing the amount of time needed to conduct additional studies, as well as the cost of vaccine candidate development. This successful strategy may be applied to other pathogens of high consequence for vaccine development, and shows how strategic preparedness for biodefense can be leveraged in response to outbreaks and public health emergencies.

Retrospective Analysis of Pneumonic Tularemia in Operation Whitecoat Human Subjects: Disease Progression and Tetracycline Efficacy

Francisella tularensis is a highly infectious Gram-negative bacterium that is the etiologic agent of tularemia in animals and humans. The incidence of tularemia is very low with a lack of comprehensive data that describe disease in humans due to difficulty in understanding time and routes of exposure. Under the title Operation Whitecoat, researchers at Ft. Detrick, MD conducted 40 clinical studies of tularemia from 1958 to 1968. In these studies, one of the objectives was to evaluate candidate countermeasures for treatment or prophylaxis of disease after exposure to Francisella tularensis strain Schu S4 by inhalation. These studies were reviewed retrospectively to delineate the early signs and symptoms or natural history of pneumonic tularemia and examine the efficacy of tetracycline in controlled human clinical studies. Using vital signs, onset of fever was objectively defined and calculated for each subject, while Adverse Events reported after exposure were also used to define the timing of disease onset and symptoms of early disease. There was a dose response relationship between time to fever onset and exposed dose at 200 cfu (172.8 h), 700 cfu (163.2 h), 2,500 cfu (105.3 h), and 25,000 cfu (75.5 h). Onset of fever was typically the earliest sign of disease at all doses but was often accompanied by symptoms such as headache, myalgia, chest pain, and nausea, irrespective of dose except at 200 cfu where only 50% of subjects exhibited fever onset or symptoms. Examining the efficacy of different treatment regimens of tetracycline, ineffective treatments were indicated by relapse of disease (fever and Adverse Events) after cessation of antibiotic treatment. Stratification of the data suggested that treatment for <14 days or doses <2g/day was associated with increased percentage of subjects with relapse of disease symptoms. Although these types of human challenge studies would not be ethically possible now, the climate post-World War II supported human testing under rigorous conditions with informed consent. Thus, going back and analyzing these unique clinical human challenge studies has helped describe the course of infection and disease induced by a biothreat pathogen and possible countermeasures for treatment under controlled conditions.

A mouse strain defective in both T cells and NK cells has enhanced sensitivity to tumor induction by plasmid DNA expressing both activated H-Ras and c-Myc

As part of safety studies to evaluate the risk of residual cellular DNA in vaccines manufactured in tumorigenic cells, we have been developing in vivo assays to detect and quantify the oncogenic activity of DNA. We generated a plasmid expressing both an activated human H-ras gene and murine c-myc gene and showed that 1 µg of this plasmid, pMSV-T24-H-ras/MSV-c-myc, was capable of inducing tumors in newborn NIH Swiss mice. However, to be able to detect the oncogenicity of dominant activated oncogenes in cellular DNA, a more sensitive system was needed. In this paper, we demonstrate that the newborn CD3 epsilon transgenic mouse, which is defective in both T-cell and NK-cell functions, can detect the oncogenic activity of 25 ng of the circular form of pMSV-T24-H-ras/MSV-c-myc. When this plasmid was inoculated as linear DNA, amounts of DNA as low as 800 pg were capable of inducing tumors. Animals were found that had multiple tumors, and these tumors were independent and likely clonal. These results demonstrate that the newborn CD3 epsilon mouse is highly sensitive for the detection of oncogenic activity of DNA. To determine whether it can detect the oncogenic activity of cellular DNA derived from four human tumor-cell lines (HeLa, A549, HT-1080, and CEM), DNA (100 µg) was inoculated into newborn CD3 epsilon mice both in the presence of 1 µg of linear pMSV-T24-H-ras/MSV-c-myc as positive control and in its absence. While tumors were induced in 100% of mice with the positive-control plasmid, no tumors were induced in mice receiving any of the tumor DNAs alone. These results demonstrate that detection of oncogenes in cellular DNA derived from four human tumor-derived cell lines in this mouse system was not possible; the results also show the importance of including a positive-control plasmid to detect inhibitory effects of the cellular DNA.

The transduction of rat submandibular glands by an adenoviral vector carrying the human growth hormone gene is associated with limited and reversible changes at the infusion site

Adenoviral vectors have been shown to efficiently deliver exogenous genes to salivary glands and have therefore been investigated as tools for the treatment of human disease. The purpose of this study was to evaluate the response of F344 rats to intraductal infusion of the right submandibular salivary gland with an adenoviral vector encoding the gene for human growth hormone (AdCMVhGH). Co-administration of hydroxychloroquine (HCQ) was used to redirect the secretion of human growth hormone (hGH) from saliva into serum. This paper documents the findings of the pathology evaluation of this National Toxicology Program study. The right submandibular salivary gland (infusion site) was the primary target organ, with microscopic lesions characteristic of a mild to moderate insult observed at 3 days post infusion in vector exposed animals. These lesions were characterized by variable degrees of acute glandular inflammation, degeneration and necrosis, with more severe lesions in the higher dose groups. Rats at 28 days post infusion had milder inflammation, degeneration and necrosis compared to day 3 rats, with variable degrees of regeneration. In conclusion, the effects on the salivary glands are reversible as indicated by the milder inflammation and degeneration in the day 28 rats concomitant with mild to moderate regeneration. Therefore, the vector appears relatively innocuous with limited tissue toxicity. [The supplemental data referenced in this paper is not printed in this issue of Toxicologic Pathology. It is available as a downloadable file in the online edition of Toxicologic Pathology, 34(4). In order to access the full article online, you must have either an individual subscription or a member subscription accessed through www.toxpath.org.].

The effects of 4-nonylphenol in rats: a multigeneration reproduction study

The alkylphenol breakdown products of alkylphenol ethoxylates have been shown in in vitro studies to be weakly estrogenic, but few in vivo data address this issue in mammals. Because estrogens have been found to be most potent during developmental/perinatal exposures, this study maximized developmental exposure to nonylphenol (NP) by treating 3.5 generations of Sprague-Dawley rats to NP in diet at 200, 650, and 2000 ppm to determine the range and severity of any toxicity. Dose rate was higher for younger rats; calculated dose ranges were 9-35, 30-100, and 100-350 mg/kg/d for the low (200NP), middle (650NP), and high (2000NP) dose groups, respectively. There were adult (F0, F1, F2) and postnatal day (pnd) 21 (F1, F2, F3) necropsies; the oldest F3 rats were killed on pnd 55-58. Body weight gain was reduced by 8-10% in the 650NP and 2000NP groups. Vaginal opening was accelerated by approximately 2 days (650NP) and approximately 6 days (2000NP) in F1, F2, and F3 generations. Uterine weights at pnd 21 were increased in 650NP (14%) and 2000NP (50%) F1 females, but not in other generations. Testis descent, anogenital distance, and preputial separation were not consistently changed. No consistent changes were seen in pup number, weight or viability, litter indices, or other functional reproductive measures. Relative ovary weight in F2 adults was decreased at 650NP and 2000NP by 12%; relative ovary was unchanged in other generations. Follicle counts were unchanged in F2 adults. Sperm indices, including CASA measures, were unchanged in F0 and F1 males. In F2 rats, epididymal sperm density was reduced by 8% and 13% at 650NP and 2000NP, respectively. Testicular spermatid count was reduced by 13% in 2000NP F2 males; testis and epididymis weights were unchanged. Erosion of gastric and duodenal mucosa was monitored grossly and microscopically, and never found. Kidney weights were increased in 650NP and 2000NP males, and renal medullary tubular dilatation and cyst formation were noted in all generations of males, and often at the lowest dose tested. These data show that NP had limited effects on the reproductive system in the presence of measurable nephrotoxicity. The F2 sperm effects are either statistical/biological "noise," or imply heretofore unknown pharmacokinetics or toxicodynamics. These sperm data should be interpreted cautiously until the findings are repeated.

Channel patency and neovascularization after transmyocardial revascularization using an excimer laser: results and comparisons to nonlased channels

BACKGROUND

Transmyocardial revascularization (TMR) has emerged as a promising treatment for ischemic heart disease in patients who are not candidates for coronary bypass surgery or angioplasty. Controversy exists, however, as to whether the use of laser energy is critical for TMR channel patency. We therefore compared by histologic assessment the outcome of lased channels with nonlased channels 30) days after TMR, using a low energy, short-pulse, fiberoptic excimer laser.

METHODS AND RESULTS

In each of six sheep, 36 1-mm TMR channels (9 mJ; 240 Hz; 1.55 cm advance/s) were placed in the anterior wall of the left ventricle, and 12 1-mm nonlased channels were created in adjacent segments by advancing the fiberoptic through the left ventricular wall with the laser inactivated. Of the 36 lased channels, 56+/-7.3% were identifiable, and 100% of those identifiable appeared to represent a "channel derivative" with evidence of an endothelialized lumen, whereas none of the nonlased channels had evidence of channel patency. Lased channels had a marked neovascular response (graded on a 0-3 scale) compared with nonlased channels (2.5+/-0.1 versus 1.0+/-0.1; P<.05). Echocardiography performed 1 and 30 days after TMR demonstrated normal global and regional left ventricular function in all animals. Creatinine phosphokinase myocardial band fractions were not significantly increased after TMR.

CONCLUSIONS

TMR using the excimer laser results in increased evidence of channel derivatives and neovascularization compared with nonlased channels while preserving normal ventricular function. These findings suggest that laser energy may be an important component of TMR strategy.