Chlorpyrifos induces lung metastases and modulation of cancer stem cell markers in triple negative breast cancer model.

Breast cancer is a major public health problem, and distant metastases are the main cause of morbidity and mortality. Chlorpyrifos is an organophosphate that promotes Epithelial-Mesenchymal Transition-like phenotype in breast cancer cell lines and modulates the Breast Cancer Stem Cells activating two key processes related to the metastatic cascade. Here, we investigated whether Chlorpyrifos may induce distant metastases in an in vivo triple negative tumor model. Also, we studied the expression of Breast Cancer Stem Cell and Epithelial-Mesenchymal Transition activation-markers in Triple Negative Breast Cancer mice tumors and human cells. We demonstrate that Chlorpyrifos modulates stem cell plasticity as a function of growth conditions in monolayer or three-dimensional culture. Furthermore, Chlorpyrifos decreased the doubling period, increased tumor volume, stimulated the infiltration of adjacent muscle fibers and induced lung and lymphatic node metastases in mice. Finally, Chlorpyrifos modulated the expression of Epithelial-Mesenchymal Transition and Breast Cancer Stem Cell markers in mice exposed to the pesticide. All our findings confirm that Chlorpyrifos promotes breast cancer progression, enhances stemness and Epithelial-Mesenchymal Transition marker expression and generates lung metastases in an in vivo model induced in mice.