Inhibition of Nox1 induces apoptosis by attenuating the AKT signaling pathway in oral squamous cell carcinoma cell lines

: NADPH oxidases, also known as the Nox family, are major sources of reactive oxygen species generation that regulate redox-sensitive signaling pathways. Recent studies have implicated the Nox family in cancer development and progression. However, the involvement of its members in the development of oral squamous cell carcinoma (OSCC) remains to be elucidated. To clarify this issue, we first analyzed mRNA expression of Nox/Duox family members (Nox1, Nox2, Nox3, Nox4, Nox5, Duox1 and Duox2) in five OSCC cell lines. Nox1 and Nox4 mRNAs were highly expressed in four OSCC cell lines. Western blot analysis revealed that the protein expression level of Nox1 was higher than that of Nox4 in the OSCC cell lines. In addition, knockdown of Nox1, but not Nox4, significantly suppressed cell viability and induced apoptosis in the HSC-2 and HSC-3 cells. We also found that a specific AKT inhibitor, perifosine, dose-dependently suppressed OSCC cell growth. Notably, Nox1 knockdown significantly attenuated the phosphorylation level of AKT. Furthermore, both Nox1 knockdown and perifosine treatment markedly enhanced the cisplatin-induced cytotoxic effect. Taken together, our results highlight that the Nox1/AKT signaling pathway plays an important role in cell survival in OSCC cells.