PI3K/Akt/JNK/c-Jun Signaling Pathway is a Mediator for Arsenite- Induced Cyclin D1 Expression and Cell Growth in Human Bronchial Epithelial Cells

Arsenite exposure is associated with an increased risk of human lung cancer. However, the molecular mechanisms underlying the arsenite-induced human lung carcinogenesis remain elusive. In this study, we demonstrated that arsenite upregulates cyclin D1 expression/activity to promote the growth of human bronchial epithelial Beas-2B cells. In this process, the JNKs (c-Jun N-terminal kinases)/c-Jun cascade is elicited. The inhibition of JNKs or c-Jun by chemical or genetic inhibitors blocks the cyclin D1 induction mediated by arsenite. Furthermore, using a loss of function mutant of p85 (Δp85, a subunit of PI3K) or dominant-negative Akt (DN-Akt), we showed that PI3K and Akt act as the upstream regulators of JNKs and c-Jun in arsenite-mediated growth promotion. Overall, our data suggest a pathway of PI- 3K/Akt/JNK/c-Jun/cylin D1 signaling in response to arsenite in human bronchial epithelial cells.