Glyphosate Primes Mammary Cells for Tumorigenesis by Reprogramming the Epigenome in a TET3-Dependent Manner

Abstract

The acknowledgment that pollutants might influence the epigenome raises serious concerns regarding their long-term impact on the development of chronic diseases. The herbicide glyphosate has been scrutinized for an impact on cancer incidence, but reports demonstrate the difficulty of linking estimates of exposure and response analysis. An approach to better apprehend a potential risk impact for cancer is to follow a synergistic approach, as cancer rarely occurs in response to one risk factor. The known influence of glyphosate on estrogen-regulated pathway makes it a logical target of investigation in breast cancer research. We have used nonneoplastic MCF10A cells in a repeated glyphosate exposure pattern over 21 days. Glyphosate triggered a significant reduction in DNA methylation, as shown by the level of 5-methylcytosine DNA; however, in contrast to strong demethylating agent and cancer promoter UP peptide, glyphosate-treated cells did not lead to tumor development. Whereas UP acts through a DNMT1/PCNA/UHRF1 pathway, glyphosate triggered increased activity of ten-eleven translocation (TET)3. Combining glyphosate with enhanced expression of microRNA (miR) 182-5p associated with breast cancer induced tumor development in 50% of mice. Culture of primary cells from resected tumors revealed a luminal B (ER+/PR-/HER2-) phenotype in response to glyphosate-miR182-5p exposure with sensitivity to tamoxifen and invasive and migratory potentials. Tumor development could be prevented either by specifically inhibiting miR 182-5p or by treating glyphosate-miR 182-5p-cells with dimethyloxallyl glycine, an inhibitor of TET pathway. Looking for potential epigenetic marks of TET-mediated gene regulation under glyphosate exposure, we identified MTRNR2L2 and DUX4 genes, the hypomethylation of which was sustained even after stopping glyphosate exposure for 6 weeks. Our findings reveal that low pressure but sustained DNA hypomethylation occurring via the TET pathway primes cells for oncogenic response in the presence of another potential risk factor. These results warrant further investigation of glyphosate-mediated breast cancer risk.

A risk progression breast epithelial 3D culture model reveals Cx43/hsa_circ_0077755/miR-182 as a biomarker axis for heightened risk of breast cancer initiation

“…5a). This might imply that the down-regulation of hsa_circ_0077755, which is indicative of loss of of Cx43 mRNA expression along breast cancer initiation 8 , relieves its sponging activity on miR-182 causing an upregulation in its expression, which in turn acts as an oncogene and primers tumor initiation as mentioned earlier [68][69][70] . In addition, survival analyses for patients with grade II breast tumors revealed poor prognostic asso- www.nature.com/scientificreports/ ciation upon the up-regulation of miR-182 in a cohort of 460 patients (Fig.…”

“…Over-expression of miR-182 in vitro enhanced cell migration, invasion and proliferation and increased tumor volume and lung metastasis in vivo by regulating FOXF2 69 . In addition, in an attempt to identify insults that lead to breast cancer initiation, Duforestel et al revealed that exposing non-neoplastic MCF10A cells to low pressure but sustained DNA hypomethylation, via the TET pathway, through repeated exposure to Glyphosate, in combination with over-expression of miR-182 primed tumor-initiation from these non-neoplastic cells in vivo 70 . Thus, desponging these miRNAs by the differentially expressed circRNAs specific to Cx43 loss might drive mammary pretumorigenic phenotypes and cancer initiation, and hence, corroborate gap junction’s involvement in post-transcriptional regulatory axes that heighten the risk of breast cancer initiation.…”

Glyphosate and AMPA Induce Alterations in Expression of Genes Involved in Chromatin Architecture in Human Peripheral Blood Mononuclear Cells (In Vitro)

“…Ten-eleven translocations (TET) are other enzymes active in DNA methylation, which oxidize 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC), leading to DNA demethylation by removing 5-mC from the genome [ 39 , 40 , 41 ]. Duforestel et al [ 17 ] used nonneoplastic MCF10A cells in a repeated glyphosate exposure pattern over 21 days. They observed that glyphosate triggered a significant increase in the activity of ten-eleven translocation (TET3) enzyme and could affect breast cells to tumorigenesis via epigenetic reprogramming, which occurred through TET3-mediated global and local DNA hypomethylation.…”

“…Recent findings have suggested that glyphosate and AMPA affect changes in the human epigenome, associated with alterations in global methylation [ 16 , 17 , 18 , 19 ]. Furthermore our previous studies [ 20 , 21 ] had shown that glyphosate and AMPA significantly altered global DNA methylation in peripheral blood mononuclear cells (PBMCs), methylation in the promoter regions of tumor suppressor genes as well as expression of major cell cycle drivers and apoptosis.…”

Low herbicide doses can change the responses of weeds to subsequent treatments in the next generation: metamitron exposed PSII‐target‐site resistant Chenopodium album as a case study

“…It is therefore also unclear if quantities of herbicides as low as those that induce hormesis can trigger longer‐lasting epigenetic changes in plants. Nevertheless, the potential confirmation that herbicide hormesis has the ability to induce epigenetically mediated resilient phenotypes across generations would raise serious questions and concerns about potential practical, ecological and/or evolutionary long‐term effects …”