John R Bucher's research while affiliated with National Institute of Environmental Health Sciences and other places

The cancer hazard associated with lifetime exposure to radiofrequency radiation (RFR) was examined in Sprague Dawley (SD) rats at the Ramazzini Institute (RI), Italy. There were increased incidences of gliomas and cardiac schwannomas. The translational relevance of these rare rat tumors for human disease is poorly understood. We examined the genetic alterations in RFR-derived rat tumors through molecular characterization of important cancer genes relevant for human gliomagenesis. A targeted next-generation sequencing (NGS) panel was designed for rats based on the top 23 orthologous human glioma-related genes. Single-nucleotide variants (SNVs) and small insertion and deletions (indels) were characterized in the rat gliomas and cardiac schwannomas. Translational relevance of these genetic alterations in rat tumors to human disease was determined through comparison with the Catalogue of Somatic Mutations in Cancer (COSMIC) database. These data suggest that rat gliomas resulting from life-time exposure to RFR histologically resemble low grade human gliomas but surprisingly no mutations were detected in rat gliomas that had homology to the human IDH1 p.R132 or IDH2 p.R172 suggesting that rat gliomas are primarily wild-type for IDH hotspot mutations implicated in human gliomas. The rat gliomas appear to share some genetic alterations with IDH1 wildtype human gliomas and rat cardiac schwannomas also harbor mutations in some of the queried cancer genes. These data demonstrate that targeted NGS panels based on tumor specific orthologous human cancer driver genes are an important tool to examine the translational relevance of rodent tumors resulting from chronic/life-time rodent bioassays.

Background: The Consortium Linking Academic and Regulatory Insights on Bisphenol A Toxicity (CLARITY-BPA) was a collaborative research effort to better link academic research with governmental guideline studies. This review explores the secondary goal of CLARITY-BPA: to identify endpoints or technologies from CLARITY-BPA and prior/concurrent literature from these laboratories that may enhance the capacity of rodent toxicity studies to detect endocrine disrupting chemicals (EDCs). Methods: A systematic literature search was conducted with search terms for BPA and the CLARITY-BPA participants. Relevant studies employed a laboratory rodent model and reported results on 1 of the 10 organs/organ systems evaluated in CLARITY-BPA (brain and behavior, cardiac, immune, mammary gland, ovary, penile function, prostate gland and urethra, testis and epididymis, thyroid hormone and metabolism, and uterus). Study design and findings were summarized, and a risk-of-bias assessment was conducted. Results: Several endpoints and methods were identified as potentially helpful to detect effects of EDCs. For example, molecular and quantitative morphological approaches were sensitive in detecting alterations in early postnatal development of the brain, ovary, and mammary glands. Hormone challenge studies mimicking human aging reported increased susceptibility of the prostate to disease following developmental BPA exposure. Statistical analyses for nonmonotonic dose responses, and computational approaches assessing multiple treatment-related outcomes concurrently in linked hormone-sensitive organ systems, reported effects at low BPA doses. Conclusions: This review provided an opportunity to evaluate the unique insights provided by nontraditional assessments in CLARITY-BPA to identify technologies and endpoints to enhance detection of EDCs in future studies.

The cancer hazard associated with exposure to cell phone radiofrequency radiation (RFR) was examined using lifetime exposure in Sprague-Dawley (SD) rats at the Ramazzini Institute (RI), Italy. There were increased incidences of gliomas in the brain and schwannomas in the heart. In order to understand the translational relevance of these rat tumors for human disease, we examined the top 23 orthologous cancer genes mutated in human gliomas using a custom built a next-generation sequencing gene panel for rats based on Illumina’s TruSeq Custom Amplicon Technology. SD rat tissues (gliomas =15; cardiac schwannomas=9, interim (1 year) sacrificed non-tumor brain tissues from RFR exposed rats =30, control brain and heart control tissues from lifetime exposure=10 each, and age-matched control brain tissues from interim sacrificed rats=10) from the RI-RFR cancer bioassay were examined in this study. The deepSNV R-package with various filtering criteria and the read depth of >1000x were used to identify single-nucleotide variants (SNVs) in the rat gliomas and schwannomas. At 5% allelic frequency, there were an average of 43 SNVs per rat glioma and point mutations were detected in 9 genes (Arid1a, Cic, Tert promoter, Tp53, Atrx, Nf1, Pdgfra, Pi3kr1, and Setd2) in at least 3 or more rat gliomas based on population frequency. Five genes (Nf1, Tert promoter, Setd2, Arid1a, and Pdgfra) harbored SNVs in interim sacrificed brain tissues that were also present in RFR-exposed gliomas from lifetime exposure. Interestingly, no mutations were detected in hotspot regions of Idh1, Idh2, Egfr or Braf. In contrast to most human gliomas which harbor mutations in IDH1 and IDH2 genes, the rat gliomas seem to be Idh1 wild type with mutations in the other glioma-related genes. Primary cardiac tumors are extremely rare in humans. With this targeted NGS panel (at allelic frequency of 2.5%), there were an average of 146 SNVs per rat cardiac schwannoma and unique point mutations were detected in Cic, Egfr, Arid1a, Nf1, Setd2, Cdkn2a, Erbb2, Atrx, Pdgfra, and Notch1 in 3 or more cardiac schwannomas. A subset of the SNVs (Arid1a, Tp53, and Nf1) in rat gliomas was confirmed in human gliomas in the COSMIC database supporting the translational relevance of the rat gliomas for human disease. In addition, several SNVs from rat gliomas and cardiac schwannomas were found in various human cancers including carcinomas, hematopoietic neoplasms, melanomas and neuroendocrine tumors. In conclusion, the rat gliomas appear to share genetic alterations with a subtype of IDH1 wildtype human gliomas and rat primary cardiac schwannomas also harbor mutations in some of the queried cancer genes. Citation Format: Ramesh C. Kovi, Andrea Vornoli, Ashley Brooks, Thai Vu T. Ton, Miaofei Xu, Eva Tibaldi, Federica Gnudi, Jian-Liang Li, Robert C. Sills, John R. Bucher, Fiorella Belpoggi, Arun R. Pandiri. Genetic profiling of rat gliomas and cardiac schwannomas from cell phone radiofrequency radiation exposure using a targeted next-generation sequencing gene panel [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-084.