JNK-mediated transcriptional upregulation of RhoB is critical for apoptosis of HCT-116 colon cancer cells by a novel diarylsulfonylurea derivative.

Diarylsulfonylureas are potent antitumor agents that have been tested in clinical trials. However, detailed mechanisms of their apoptotic activity remain unclear. Here, we report a new diarylsulfonylurea derivative, LB2A, that upregulates RhoB, thereby inducing potent apoptosis in HCT-116 human colon cancer cells independently of p53 status. LB2A decreased procaspase-3, increased phospho-JNK, and cleaved PARP, leading to apoptosis of HCT-116 cells. Prior treatment of HCT-116 cells with the JNK inhibitor SP600125 and the RNA synthesis inhibitor DRB blocked apoptosis, implying that JNK activation and mRNA production are important for apoptosis by LB2A. Western blotting, RT-PCR, and RhoB-promoter luciferase reporter assays revealed that LB2A increased RhoB via JNK-mediated transcriptional activation. LB2A decreased HDAC1 and increased acetyl-H3, both of which activate the RhoB promoter and were blocked by SP600125. Ectopic expression of RhoB induced apoptosis of HCT-116 cells, suggesting that RhoB is critical for the anti-cancer activity of LB2A in human colon cancer cells. LB2A also exhibited potent tumor growth inhibition of HCT-116 cells in vivo using a mouse xenograft assay. Taken together, these results show that LB2A induces apoptosis of HCT-116 cells via JNK-mediated transcriptional upregulation of RhoB and may therefore provide a potential therapy for human colon cancer.