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Glyphosate: Review of Animal Carcinogenicity Data and Epigenetic Impacts

May 13, 2020
1:00 pm US Eastern Time

There is considerable controversy concerning the carcinogenicity of glyphosate, with scientists and regulatory authorities involved in the review of glyphosate having markedly different opinions. One key aspect of these opinions is the degree to which glyphosate causes cancer in laboratory animals after lifetime exposure. In addition, the acknowledgment that pollutants such as glyphosate might influence the epigenome raises serious concerns regarding its long-term impact on the development of cancer. However, reports on glyphosate demonstrate the difficulty of linking estimates of exposure and response analysis.

During the webinar, Dr. Christopher Portier presented of a review of animal carcinogenicity data after exposure to glyphosate. Dr. Portier and colleagues identified twenty-one chronic exposure animal carcinoenicity studies of glyphosate from regulatory documents and reviews. Thirteen studies that were of sufficient quality and detail were reanalyzed and presented in this review using trend tests, historical control tests, and pooled analyses.

Following this presentation, Manon Duforestel discussed a synergistic approach she and colleagues used to assess the potential risk impact for cancer, as cancer rarely occurs in response to just one risk factor. The known influence of glyphosate on estrogen-regulated pathway makes it a logical target of investigation in breast cancer research. For this purpose, she and colleagues postulated that glyphosate could induce breast cancer by itself or in combination with other oncogenic hits, in line with the multiple-hit theory of carcinogenesis. They chose to analyze the carcinogenicity of glyphosate combined with a second oncogenic hit: the overexpression of miRNAs known to be involved in tumor progression and aggressiveness. In this context, their findings revealed that glyphosate induces global DNA hypomethylation in non-neoplastic mammary epithelial MCF10A cells and contributes to tumorigenesis in a “two-hit oncogenic model.” Their data also uncovered a specific DNA hypomethylation signature of genes related to the TET3 pathway that might be used as epimark of glyphosate exposure.

Featured Speakers

Prof. Dr. Christopher J. Portier is a semi-retired expert in the design, analysis, and interpretation of environmental health data with a focus on carcinogenicity. Dr. Portier is currently a Senior Collaborating Scientist (part-time) with the Environmental Defense Fund, and an Adjunct Professor at Emory University and Maastricht University. He is also working with several governments on risk assessment issues and is a consultant on chemical-related issues (including glyphosate) to several US law firms.

He has authored more than 200 peer-reviewed publications and book chapters. During his 36+ years of research, Dr. Portier has focused on using systems-based approaches to understand the impact of the environment on human health. He has received numerous awards including the President’s Dream Green Team Award from President Obama, the Spiegelman Award from the American Public Health Association and the Outstanding Practitioner of the Year Award from the International Society for Risk Analysis. He is an elected Fellow of the International Statistics Institute, the World Innovation Foundation, the American Statistical Association and the Collegium Ramazzini.

Prior to his retirement, Dr. Portier served as the Director of the US National Center for Environmental Health at the Centers for Disease Control and Prevention and Director of the Agency for Toxic Substances and Disease Registry. Prior to this, Dr. Portier was at the US National Institute of Environmental Health Sciences (NIEHS) where he conducted research on environmental health and served as the Director of the Environmental Toxicology Program, the Associate Director of the National Toxicology Program, and the Senior Scientific Advisor to the Director of NIEHS.

Manon Duforestel is a PhD student in Cancerology and Epigenetics at CRCINA in Nantes, France. After a master's degree in biology ended by an internship at CRCL in Lyon, France, she joined the "Apoptosis an tumor progression" team led by Dr. François Vallette at the Centre de Recherche en Cancérologie Immunologie Nantes Angers. Currently in the second year of PhD under the supervision of Dr. Pierre-François Cartron, part of her thesis is devoted to the study of the link between glyphosate and carcinogenesis, always through the prism of epigenetics. The second part of her thesis is devoted to the study of the epigenetic mechanisms involved in resistance to the treatment of glioblastoma multiforme.

This webinar is one in a monthly series sponsored by the Collaborative on Health and the Environment’s EDC Strategies Partnership. The CHE EDC Strategies Partnership is chaired by Sharyle Patton (Commonweal Biomonitoring Resource Center), Jerry Heindel (Commonweal HEEDS, Healthy Environment and Endocrine Disruptor Strategies), and Genon Jensen (HEAL) and coordinated by Hannah Donart (Collaborative on Health and the Environment, a Commonweal program). To see a full list of past calls and webinars related to EDCs and listen to or view recordings, please visit our partnership page. 

This webinar was moderated by Génon Jensen, Executive Director of Health and Environment Alliance (HEAL). It lasted for 45 minutes and was recorded for our call and webinar archive. If you did not have a chance to ask a question during the Q&A portion of the presentation, please submit your questions to Génon Jensen at Contact by May 20 and we will respond via email.