Benzo[a]pyrene at human blood equivalent level induces human lung epithelial cell invasion and migration via aryl hydrocarbon receptor signaling

Benzo[a]pyrene (B[a]P), a typical carcinogenic polycyclic aromatic hydrocarbon, exists worldwide in vehicle exhaust, cigarette smoke and other polluted environments. Recent studies have demonstrated a strong association between B[a]P and lung cancer. However, whether B[a]P at human blood equivalent level can promote epithelial-mesenchymal transition (EMT), a crucial molecular event during cell malignant transformation, remains unclear. Besides, whether B[a]P facilitates this progress via aryl hydrocarbon receptor (AhR) signaling pathway also lacks scientific evidence. In our study, the transwell assay showed that 5 mu g/L of B[a]P promoted BEAS-2B cell invasion and migration. In addition, the mRNA and protein expression levels of AhR and its target genes involved in B[a]P metabolism, such as AhR nuclear translocator, heat shock protein 90 and CYP1A1, were significantly increased by B[a]P exposure. Moreover, the mRNA expression levels of downstream regulatory factors related to both AhR signaling pathway and EMT, such as NRF2, K-RAS and hypoxia-inducible factor 1-alpha, were significantly increased. Furthermore, the expression level of the epithelial marker E-cadherin was significantly downregulated, while the mRNA expression of mesenchymal phenotype markers, N-cadherin, fibronectin and vimentin, were significantly upregulated. Notably, the above changes induced by B[a]P were significantly attenuated or even stopped by resveratrol (RSV), a natural phenol, also an AhR inhibitor, when the AhR signaling pathway was inhibited by RSV, demonstrating the regulatory role of AhR signaling pathway in B[a]P-induced EMT. In conclusion, B[a]P at the human blood equivalent level induces BEAS-2B cell invasion and migration through the AhR signaling pathway.