Glyphosate as an Emerging Environmental Pollutant and Its Effects on Breast Cancer Cell Proliferation: A Systematic Literature Review of Preclinical Evidence

The widespread use of glyphosate-based herbicides (GBHs) has raised concerns about their potential role in hormone-sensitive cancers such as breast cancer. This systematic review aimed to evaluate preclinical evidence on the effects of glyphosate (pure compound) or glyphosate-based herbicide formulations (GBHs) exposure on breast cancer cell proliferation and related molecular pathways. A structured search was conducted across PubMed, ScienceDirect, and Springer Nature Link, Web of Science databases, covering studies published up to 9 November 2025, following a PROSPERO-registered protocol (ID: CRD42021238350). Eligible studies included original in vitro and in vivo preclinical research using human breast cancer cell lines (e.g., MCF-7, T47D, MDA-MB-231, MCF-12A, and MCF-10A) or relevant animal models. Outcomes assessed included cell viability, proliferation, tumor growth, apoptosis, cell cycle regulation, and molecular markers associated with endocrine signaling. Two reviewers independently screened and extracted data, resolving disagreements via discussion or third-party adjudication. From an initial pool of 699 articles, seven in vitro studies met the inclusion and quality criteria. Glyphosate exposure demonstrated weak estrogenic activity in ER-positive breast cancer cells, primarily via ERα modulation and altered gene expression related to proliferation and DNA repair. GBHs showed greater cytotoxic and epigenetic effects in non-tumorigenic cells, often independent of ER signaling. No included study employed in vivo breast cancer models. Overall, preclinical evidence suggests glyphosate may act as a weak endocrine disruptor under specific conditions, but findings are limited by the short-term in vitro designs, heterogeneous methodologies, and lack of chronic or in vivo data. Further research using long-term exposure and animal models is needed to clarify potential risks and inform regulatory and public health decisions.