title: Deprivation of arginine by recombinant human arginase in prostate cancer cells.
abstract: BACKGROUND
  Recombinant human arginase (rhArg) has been developed for arginine deprivation therapy in cancer, and is currently under clinical investigation. During pre-clinical evaluation, rhArg has exhibited significant anti-proliferative activity in cancer cells deficient in the expression of ornithine carbamoyl transferase (OCT). Interestingly, a variety of cancer cells such as melanoma and prostate cancer deficient in argininosuccinate synthetase (ASS) are sensitive to arginine deprivation by arginine deiminase. In this study, we investigated levels of gene expression of OCT and ASS, and the effects of rhArg in human prostate cancer cells: LNCaP (androgen-dependent), PC-3 and DU-145 (both androgen-independent).
  
  
  RESULTS
  Quantitative real-time PCR showed minimal to absent gene expression of OCT, but ample expression of ASS expression in all 3 cell lines. Cell viability assay after 72-h exposure of rhArg showed all 3 lines had half maximal inhibitory concentration less than or equal to 0.02 U/ml. Addition of ornithine to cell culture media failed to rescue these cells from rhArg-mediated cytotoxicity.Decreased phosphorylation of 4E-BP1, a downstream effector of mammalian target of rapamycin (mTOR), was noted in DU-145 and PC-3 after exposure to rhArg. Moreover, there was no significant apoptosis induction after arginine deprivation by rhArg in all 3 prostate cancer cell lines.
  
  
  CONCLUSIONS
  rhArg causes significant cytotoxicity in LNCaP, DU-145 and PC-3 prostate cancer cells which all demonstrate decreased OCT expression. Inhibition of mTOR manifested by hypophosphorylation of 4E-BP1 suggests autophagy is involved as alternative cell death mechanism. rhArg demonstrates a promising novel agent for prostate cancer treatment.
authors.affiliation: Department of Surgery, Saint Louis University, St. Louis, MO, USA.
authors.forename: Eddy C
authors.initials: EC
authors.lastname: Hsueh
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Knebel
authors.forename: Wai-Hung
authors.initials: WH
authors.lastname: Lo
authors.forename: Yun-Chung
authors.initials: YC
authors.lastname: Leung
authors.forename: Paul Ning-Man
authors.initials: PN
authors.lastname: Cheng
authors.forename: Chung-Tsen
authors.initials: CT
authors.lastname: Hsueh
mesh_terms: D017209:Apoptosis; D001119:Arginase / Q000378:metabolism*; D001120:Arginine / Q000172:deficiency*; D015153:Blotting, Western; D002470:Cell Survival; D006801:Humans; D008297:Male; D009954:Ornithine Carbamoyltransferase / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D012333:RNA, Messenger; D011994:Recombinant Proteins; D001120:Arginine; D009954:Ornithine Carbamoyltransferase; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D001119:Arginase