Abstract
The natural compound 1,4-naphthoquinone has potent anti-tumor activity. However, the clinical application of 1,4-naphthoquinone and its derivatives has been limited by their side effects. In this study, we attempted to reduce the toxicity of 1,4-naphthoquinone by synthesizing two derivatives: 2,3-dihydro-2,3-epoxy-2-propylsulfonyl-5,8-dimethoxy-1,4-naphthoquinone (EPDMNQ) and 2,3-dihydro-2,3-epoxy-2-nonylsulfonyl-5,8-dimethoxy-1,4-naphthoquinone (ENDMNQ). Then we evaluated the cytotoxicity and molecular mechanisms of these compounds in lung cancer cells. EPDMNQ and ENDMNQ significantly inhibited the viabilities of three lung cancer cell lines and induced A549 cell cycle arrest at the G1 phase. In addition, they induced the apoptosis of A549 lung cancer cells by increasing the phosphorylation of p38 and c-Jun N-terminal kinase (p-JNK), and decreasing the phosphorylation of extracellular signal-related kinase (p-ERK), protein kinase B (Akt), and signal transducer and activator of transcription 3 (STAT3). Furthermore, they increased reactive oxygen species (ROS) levels in A549 cells; however, pretreatment with the ROS inhibitor N-acetyl-l-cysteine significantly inhibited EPDMNQ- and ENDMNQ-mediated apoptosis and reversed apoptotic proteins expression. In conclusion, EPDMNQ and ENDMNQ induced G1 phase cell cycle arrest and apoptosis in A549 cells via the ROS-mediated activation of mitogen activated protein kinase (MAPK), Akt and STAT3 signaling pathways.