Inhibition of CUG-binding protein 1 and activation of caspases are critically involved in piperazine derivative BK10007S induced apoptosis in hepatocellular carcinoma cells

Though piperazine derivative BK10007S was known to induce apoptosis in pancreatic cancer xenograft model as a T-type CaV3.1 a1G isoform calcium channel blocker, its underlying antitumor mechanism still remains unclear so far. Thus, in the present study, the antitumor mechanism of BK10007S was elucidated in hepatocellular carcinoma cells (HCCs). Herein, BK10007S showed significant cytotoxicity by 3-[4,5-2-yl]-2,5-diphenyltetra-zolium bromide (MTT) assay and anti-proliferative effects by colony formation assay in HepG2 and SK-Hep1 cells. Also, apoptotic bodies and terminal deoxynucleotidyl transferase (TdT) dUTP Nick End Labeling (TUNEL) positive cells were observed in BK10007S treated HepG2 and SK-Hep1 cells by 4',6-diamidino-2-phenylinodole (DAPI) staining and TUNEL assay, respectively. Consistently, BK10007S increased sub G(1) population in HepG2 and SK-Hep1 cells by cell cycle analysis. Furthermore, Western blotting revealed that BK10007S activated the caspase cascades (caspase 8, 9 and 3), cleaved poly (ADP-ribose) polymerase (PARP), and downregulated the expression of cyclin D1, survivin and for CUG-binding protein 1 (CUGBP1 or CELF1) in HepG2 and SK-Hep1 cells. Conversely, overexpression of CUGBP1 reduced cleavages of PARP and caspase 3, cytotoxicity and subG(1) population in BK10007S treated HepG2 cells. Overall, these findings provide scientific evidences that BK10007S induces apoptosis via inhibition of CUGBP1 and activation of caspases in hepatocellular carcinomas as a potent anticancer candidate.