Anti-tumor Efficacy of a Recombinant Human Arginase in Human Hepatocellular Carcinoma

Ariel      K.M. Chow; Lui      Ng; Hung      Sing Li; Chi Wai      Cheng; Colin      S.C. Lam; Thomas      C.C. Yau; Paul      N.M. Cheng; Sheung      Tat Fan; Ronnie      T.P. Poon; Roberta      W.C. Pang

Abstract

Hepatocellular carcinoma (HCC) is considered as auxotrophic for arginine and BCT-100, a new recombinant human arginase, has been synthesized for arginine deprivation to inhibit arginine-dependent tumor growth. The aim of the present study was to evaluate the effects of BCT-100 on the inhibition of in vitro cell proliferation of HCC cell lines and in vivo tumor growth. The molecular mechanism involved was also studied. The anti-tumor efficacy of BCT-100 on cell proliferation, cell cycle distribution and cellular apoptosis were determined in human hepatoma HepG2 and PLC/PRF/5 cells. Protein expression in the Wnt/β-catenin and Akt signaling pathways were analyzed by western blotting. Tumors were also established subcutaneously and BCT-100, in combination with oxaliplatin, was administrated i.p. to study the anti-tumor growth of the drugs. Treatment with BCT-100 was found to inhibit cell proliferation and enhance caspasedependent cellular apoptosis. Cell cycle arrest at S phase was observed. Inhibition of Wnt/β-catenin and Akt signaling pathways, with a reduction in survivin and XIAP protein expressions, were also observed. Furthermore, combined treatment of BCT-100 and chemotherapy with oxaliplatin demonstrated synergistic inhibiting effect on tumor growth and the overall survival probability was enhanced as compared with BCT-100 or oxaliplatin treatment alone. These preclinical data demonstrate robust anti-tumor activity of BCT100 in HCC, thus providing the basis for its exploitation as a potential therapeutic agent in arginine-driven tumors. The positive effect of testing BCT100 with oxaliplatin in PLC/PRF/5 tumours also supports the rationale of combining BCT-100 and oxaliplatin in the clinical treatment of HCC.

Keywords: Hepatocellular carcinoma, human recombinant arginase, novel therapy, preclinical study, survivin, Wnt/β-catenin signaling pathway, XIAP, polyethylene glycol, propodium iodide, ornithine transcarbamylase, "3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide", mammalian target of rapamycin, mitogen-activated protein kinase, low-density-lipoprotein receptor protein, eukaryotic translation initiation factor 4E, dishevelled (dsh) homolog