Effects of exposure to benzo[a]pyrene on metastasis of breast cancer are mediated through ROS-ERK-MMP9 axis signaling

• Exposure to benzo[a]pyrene increases the migration and invasion of breast cancer cells both in vitro and in vivo.
• Benzo[a]pyrene enhanced breast cancer cell migration and invasion is mediated by up-regulating ROS-induced ERK signaling, which leads to the activation of matrix metalloproteinase 9.
• A new murine model was established to demonstrate that benzo[a]pyrene-induced mammary gland cancer metastasis is an important and intricate process facilitated by cumulative benzo[a]pyrene exposure.

Metastasis is the leading cause of deaths in patients with breast cancer. Benzo[a]pyrene is a cumulative carcinogen and ubiquitous environmental pollutant with potent carcinogenic properties. As we report here, we established an accumulative mouse model mimicking the cumulative effects of benzo[a]pyrene exposure in human breast carcinogenesis. Our focus was on elucidating the mechanisms by which benzo[a]pyrene contributes to the process of breast cancer metastasis. Our study indicated that benzo[a]pyrene increased the migration of breast cancer cells both in vitro and in vivo. Specifically, we demonstrated that benzo[a]pyrene enhances breast cancer cell migration and invasion by up-regulating ROS-induced ERK signaling, leading to the activation of matrix metalloproteinases 9. Our results suggest that benzo[a]pyrene-induced mammary gland cancer metastasis is an important and intricate process facilitated by cumulative benzo[a]pyrene exposure leading to activation of the ROS-ERK-MMP9 signaling pathway.