B1, a novel HDAC inhibitor, induces apoptosis through the regulation of STAT3 and NF-κB.

We previously demonstrated that B1 induced significant cytotoxic effects, cell cycle G1 arrest and apoptosis in human lung cancer A549 cells through the inhibition of DNA topoisomerase II activity. In the present study, we focused on the histone deacetylase (HDAC) modulation of B1 in A549 cells. HDACs, important enzymes affecting epigenetic regulation, play a crucial role in human carcinogenesis. Our findings showed that B1 could suppress the growth of A549 cells in vitro through the inhibition of HDAC activity. Additionally, B1 caused disruption of the mitochondrial membrane potential and induced DNA double-strand breaks (DSBs) in a dose- and time-dependent manner, which consequently led to cell apoptosis. We also observed that B1 inhibited cancer cell migration and angiogenesis-related signal expression, including vascular endothelial growth factor (VEGF) and pro-matrix metalloproteinases-2 and -9 (pro-MMP-2/9). Gelatin zymography suggested that B1 decreased pro-MMP-2 and pro-MMP-9 activity. Transcription factors, signal transducer and activator of transcription 3 (STAT3) and nuclear factor-κB (NF-κB), are vital players in the many steps of carcinogenesis. B1 showed significant dose-response inhibitory effects on cytoplasmic expression and nuclear translocation of both phosphorylated STAT3 (pSTAT3) and NF-κB. It has been well documented that reactivated telomerase confers cancer cells the ability to repair DNA. Real-time PCR results indicated that B1 inhibited STAT3 and NF-κB mRNA expression and telomerase activity. Taken together, our results demonstrated that B1 exerted significant inhibitory effects on HDAC, telomerase activities, oncogenic STAT3 and NF-κB expression. The inhibition of the intricate crosstalk between STAT3 and NF-κB may be a major factor in the molecular action mechanism of B1. The multiple targeting effects of B1 render it a potential new drug for lung cancer therapy.