Fenhexamid (Fen), a fungicide used to treat gray mold of fruits and vegetables, is reported to function as an
endocrine disrupting chemical via the
estrogen receptors (ER), despite low-toxicity of the
pesticide. In this study, we elucidated that the disrupting effects of Fen are exerted via the ER and
phosphatidylinositol 3-kinase (PI3K) pathways in
breast cancer models. The WST assay, live cell monitoring, cell cycle analysis, colony formation assay, apoptotic analysis by
JC-1 dyeing, and Western blot analysis were applied in ER positive MCF-7 and ER negative MDA-MB-231
breast cancer cells, after exposure to 17β-estradiol (E2), Fen,
ICI 182,780 (ICI; an ER antagonist) and/or
Pictilisib (Pic; a PI3K inhibitor). Exposure to E2 and Fen induced the cell growth and survival ability of MCF-7 cells by increasing the S-phase cells and regulating the cell cycle-related
proteins (
Cyclin D1 and E1, p21 and p27). In addition, E2 and Fen treatment resulted in elevated levels of the survival-related
proteins (
Survivin and
PCNA), and inhibited apoptosis by increasing the mitochondrial membrane potential and regulating the apoptosis-related
proteins (BAX, BCL-2, and
Caspase-9). These changes were reversed to the same level as the control group when exposed to their respective inhibitors, thereby indicating that the changes are exerted via the ER and PI3K pathways. In particular, co-treatment with these inhibitors induced greater inhibition than single treatment. Conversely, no alterations were observed in the ER-negative MDA-MB-231
breast cancer cells. Taken together, these results indicate that Fen promotes the growth of
breast cancer cells via the ER and/or PI3K pathways, similar to the E2 mechanism. Although a relatively safe
pesticide, Fen possibly exerts its influence as an
endocrine disrupting chemical in ER-positive
breast cancer cells via the ER and PI3K pathways.