King’s College London
Breast Cancer UK was pleased to award Dr Michael Antoniou, from King’s College London, two research grants to evaluate the endocrine disrupting properties of the herbicide glyphosate, and to investigate the endocrine disrupting effects of low dose EDC mixtures of herbicides and plasticisers (bisphenol compounds).
Evaluating the Endocrine Disrupting Properties of Glyphosate
Breast Cancer UK is funding research, being carried out at King’s College London, into the potential endocrine (hormone) disrupting effects of glyphosate and commercial glyphosate formulations.
Glyphosate-based herbicides (weedkillers) are the world’s most abundantly used pesticides both in agriculture and domestically. Recently, WHO listed glyphosate as a probable cause of cancer in humans . Glyphosate is not currently listed as an endocrine disrupting chemical (EDC), despite evidence ,  which suggests it may interfere with oestrogen signaling that could lead to breast tumour formation and/or progression.
Human breast cancer cells, whose growth under laboratory conditions is either dependent or independent on the presence of oestrogen, will be exposed to environmentally relevant (real world exposure) concentrations of glyphosate and commercial glyphosate formulations. Commercial glyphosate formulations are a mixture of glyphosate and a complex array of additional chemicals collectively labeled as “inert adjuvants” but which are proving to be toxic in their own right. Hence the need to test commercial glyphosate formulations alongside glyphosate alone. Cells will also be exposed to selective inhibitors of oestrogen receptors (e.g., tamoxifen) to determine their role in any toxic, endocrine disruptive effects observed. EDC effects will be determined by measuring cell survival, cell growth rates, and gene expression profiling (transcriptomic analysis), which provides insight into which biochemical pathways are affected.
This research will help advance our understanding of the potential dangers of glyphosate arising from EDC effects and how it interacts with oestrogen receptors to create a potentially carcinogenic environment, which may contribute to either the formation of breast cancer or stimulate its progression.
Brief description of results
Different glyphosate-based herbicide formulations, pure glyphosate, and co-formulant mixtures, were tested in cell culture systems using oestrogen-dependent and oestrogen independent human breast cancer cells, to determine whether compounds were able to mimic oestrogen-dependent or independent cell proliferation. Glyphosate was found to be a weak activator of the oestrogen receptor in hormone-dependent human breast cancer cells. Glyphosate formulations and co-formulants were not oestrogenic.
RNA sequencing and gene expression profiling using oestrogen-dependent human breast cells were used to assess involvement of other signaling pathways (including other non-classical oestrogenic pathways) and confirm any endocrine disruptive effects and computer modelling of the interaction of glyphosate at the active site of oestrogen receptor alpha was performed. The findings indicate that glyphosate does not bind to the oestrogen receptor alpha and is activating the receptor through a ligand-independent mechanism that may affect the balance between cell proliferation and programmed cell death.
In summary: glyphosate is oestrogenic at high concentration but not at exposure levels normally encountered by the general population
Evaluating the Endocrine Disrupting Properties of Mixtures of Herbicides and Plasticisers
Endocrine disrupting chemicals that will be tested include the herbicides glyphosate, 2,4-D and dicamba, and the plasticisers bisphenol A (BPA), and BPA variants (e.g. bisphenol F, bisphenol Z, bisphenol B) which are increasingly being used as BPA substitutes.
Bisphenol A is oestrogenic and may cause adverse health effects, including breast cancer. For these reasons, BPA is being phased out by plastics manufacturers and replaced with BPA variants. Identifying whether or not potential replacements for BPA are oestrogenic is important, and such data may be used to justify a ban on the use of all bisphenols as plasticisers.
Glyphosate is under consideration for reauthorization in the EU and its use is likely to be restricted. If glyphosate is restricted, it seems likely use of dicamba and 2,4-D will increase. 2,4-D is oestrogenic and has been linked to breast cancer and dicamba is a potential EDC with possible cancer links. Hence, the oestrogenic effect of these herbicide combinations is highly relevant.
Brief description of results
Bisphenol A (BPA) is being phased out of plastics and being replaced by BPA alternatives. Six such compounds (bisphenol S, bisphenol F, bisphenol AP, bisphenol AF, bisphenol Z and bisphenol B) were tested for their oestrogenic activity using cell culture, gene expression profiling and RNA sequencing, as described above. Each was able to promote breast cancer cell growth through oestrogen receptors. Furthermore, bisphenol AF, bisphenol B and bisphenol Z contained in “BPA-free” plastics, were more oestrogenic than BPA (which was recently classified by the EU as a substance of very high concern due to its endocrine disrupting and reprotoxic properties).
In summary: Bisphenol substitutes are as oestrogenic as BPA; and some are more oestrogenic and potentially more harmful
Dr Antoniou's full report can be found here and the associated research paper here. For more information and comment on this research see our science blog written by Dr Robin Mesnage, a co-recipient of this research grant.
page last updated July 25, 2017