Cycloprodigiosin hydrochloride, a new H+/Cl- symporter, induces apoptosis in human and rat hepatocellular cancer cell lines in vitro and inhibits thegrowth of hepatocellular carcinoma xenografts in nude mice

The effects of cycloprodigiosin hydrochloride (cPrG-HCl), a new H+/Cl- symp orter, were examined in liver cancer cell lines in vitro and in vivo. In th e in vitro MTT assay, cPrG-HCl inhibited the growth of 6 liver cancer cell lines (Huh-7, HCC-M, HCC-T, dRLh-84, and H-35, hepatocellular carcinoma; He pG2, hepatoblastoma) in a dose- and time-dependent manner. The 50% inhibito ry concentrations (IC50) at 72 hours' treatment for liver cancer cell lines were 276 to 592 nmol/L, while that for isolated normal rat hepatocyte was 8.4 mu mol/L. The cPrG-HCl treatment of Huh-7 cells induced apoptosis as co nfirmed by the appearance of a subG(1) population, intranucleosomal DNA fra gmentation, and chromatin condensation. cPrG-HCl raised the pH of acidic or ganelles and lowered pHi (below pH 6,8). In addition, the apoptosis in Huh- 7 cells induced by cPrG-HCl was strongly suppressed when the cells were cul tured with imidazole, a cell-permeable base. In the in vivo assay, nude mic e bearing subcutaneous xenografted Huh-7 cells received 2 weeks of treatmen t with cPrG-HCl (1 or 10 mg/kg/d) subcutaneously. This treatment significan tly inhibited tumor growth compared with the control after 8 days. The cont rol mice were treated with 1% dimethylsulfoxide (DMSO) in saline (vehicle). A histopathological examination using the terminal deoxynucleotidyl transf erase mediated dUTP biotin nick end labeling (TUNEL) method showed apoptosi s in the treated tumor cells. No pathological changes were observed in any organs, and the serum alanine transaminase levels remained within normal li mits. These results suggest that cPrG-HCl may be useful for the treatment o f hepatocellular carcinoma.