SCIENCE NEWS: New study finds glyphosate is weakly oestrogenic | Breast Cancer UK

SCIENCE NEWS: New study finds glyphosate is weakly oestrogenic

Published 26 Jul 2017

Research co-funded by Breast Cancer UK and published on July 12 in the journal Food and Chemical Toxicology has found that glyphosate is oestrogenic, but only at high concentrations.

Researchers found that glyphosate, but not other compounds present in glyphosate-based herbicides, is oestrogenic, but only at relatively high concentrations (1). This suggests that humans exposed to glyphosate at typical exposure levels would not have an increased risk of breast cancer as a result of oestrogenicity.

The finding is in contrast to that of a previous study (2), which reported that glyphosate could activate the oestrogen receptor with a potency similar to natural oestrogen, (a result which has not been repeated by other researchers). The results of the current study, which used several different techniques to show glyphosate at low concentration is not oestrogenic, are consistent with results obtained from the US Environmental Protection Agency’s endocrine disruptor screening programme (3).

Glyphosate-based formulations are the most commonly used herbicides, worldwide. Glyphosate is ubiquitous in the environment (4) and routinely detected in human body fluids (5). In 2015, the WHO’s International Agency for Research on Cancer (6) classified glyphosate as a probable human carcinogen due to its positive association with non-Hodgkin’s lymphoma in humans and liver and kidney effects in animals. Recently, the state of California classified glyphosate as a substance “known to cause cancer” (7). However, classification of glyphosate as carcinogenic to humans is disputed by some scientists and regulatory bodies, including the EU’s chemicals agency, ECHA (8).

Using two assays (E-screen and an ERE-luciferase reporter assay) the new research found that a relatively high concentration of glyphosate (10 mg/l or more) activates oestrogen receptors, triggering increased growth and division of breast cancer cells. A hallmark of around two thirds of breast cancers is that cell proliferation is driven by such oestrogen receptor activation. Using gene expression studies and RNA sequencing, the research showed that breast cancer cells exposed to high concentrations of glyphosate display the hallmarks of oestrogen activation, but not those associated with glyphosate binding to the oestrogen receptor. Computer modelling (using molecular dynamic simulations) also predicted glyphosate is unlikely to bind to oestrogen receptors.

None of the co-formulants found in glyphosate-based herbicides had oestrogenic activity. Co-formulants, such as polyethoxylated tallowamine (POEA), are used to help stabilise products and allow penetration of glyphosate into the plant. Although the current study showed it doesn’t affect the oestrogen receptor, previous studies have shown POEA can inhibit aromatase (an enzyme involved in sex hormone synthesis) and is toxic to cells (9).

The results of this study are potentially encouraging for breast cancer risk, as they suggest that general exposure to glyphosate and glyphosate formulations through ordinary domestic usage and dietary intake is not oestrogenic. However, the study did find that exposure to high concentrations of glyphosate is oestrogenic – which suggests those who are acutely exposed – perhaps professionally – may be put at increased risk.

Breast Cancer UK believes more studies are needed to understand fully the role of glyphosate in breast cancer risk, in particular those involving occupational exposures, as well as the potential impact of long term chronic exposures, especially to mixtures of glyphosate-containing herbicides and other EDCs. We will continue to monitor new studies and ensure these inform our position on glyphosate and glyphosate formulations.

1. Breast Cancer UK awarded a grant of £15,000 to Dr Michael Antoniou, along with his research associate Dr Robin Mesnage, to research the endocrine disrupting properties of glyphosate. For more details see here.
2. The paper discussed is: Mesnage et al. (2017). Evaluation of estrogen receptor alpha activation by glyphosate-based herbicide constituents. Food and Chemical Toxicology (2017), doi: 10.1016/j.fct.2017.07.025.

3. The lead authors are Dr. Robin Mesnage, Research Associate, Gene Expression and Therapy Group, and Dr Michael Antoniou, Head: Gene Expression and Therapy Group, King’s College London, Department of Medical and Molecular Genetics, Guy’s Hospital, London, SE1 9RT

4. Breast Cancer UK grants programme awards up to £45,000 to further research into the environmental and chemical causes and prevention of breast cancers. No animal testing is permitted. For more information on how to apply please visit our grants section

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