title: In vitro evaluation of novel N-acetylalaninate prodrugs that selectively induce apoptosis in prostate cancer cells.
abstract: BACKGROUND
  Cancer cell esterases are often overexpressed and can have chiral specificities different from that of the corresponding normal cells and can, therefore, be useful targets for activating chemotherapeutic prodrug esters. Prodrug esters are inactive compounds that can be preferentially activated by esterase enzymes. Moreover, cancer cells often exhibit a high level of intrinsic oxidative stress due to an increased formation of reactive oxygen species (ROS) and a decreased expression of some enzymatic antioxidants. Prodrugs designed to induce additional oxidative stress can selectively induce apoptosis in cancer cells already exhibiting a high level of intrinsic oxidative stress. This study focused on the in vitro evaluation of four novel prodrug esters: the R- and S- chiral esters of 4-[(nitrooxy)methyl]phenyl N-acetylalaninate (R- and S-NPAA) and the R- and S- chiral esters of 4-[(nitrooxy)methyl]naphth-1-yl N-acetylalaninate (R- and S-NQM), which are activated, to varying extents, by oxidized protein hydrolase (OPH, EC 3.4.19.1) yielding a quinone methide (QM) intermediate capable of depleting glutathione (GSH), a key intracellular antioxidant. OPH is a serine esterase/protease that is overexpressed in some human tumors and cancer cell lines.
  
  
  METHODS
  To evaluate the chiral ester prodrugs, we monitored cellular GSH depletion, cellular protein carbonyl levels (an oxidative stress biomarker) and cell viability in tumorigenic and nontumorigenic prostate cancer cell lines.
  
  
  RESULTS
  We found that the prodrugs were activated by OPH and subsequently depleted GSH. The S-chiral ester of NPAA (S-NPAA) was two-fold more effective than the R-chiral ester (R-NPAA) in depleting GSH, increasing oxidative stress, inducing apoptosis, and decreasing cell viability in tumorigenic prostate LNCaP cells but had little effect on non-tumorigenic RWPE-1 cells. In addition, we found that that S-NPAA induced apoptosis and decreased cell viability in tumorigenic DU145 and PC3 prostate cell lines. Similar results were found in a COS-7 model that overexpressed active human OPH (COS-7-OPH).
  
  
  CONCLUSIONS
  Our results suggest that prostate tumors overexpressing OPH and/or exhibiting a high level of intrinsic oxidative stress may be susceptible to QM generating prodrug esters that are targeted to OPH with little effect on non-tumorigenic prostate cells.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: McGoldrick
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Jiang
authors.forename: Marianne
authors.initials: M
authors.lastname: Brannon
authors.forename: Koyamangalath
authors.initials: K
authors.lastname: Krishnan
authors.affiliation: Department of Pediatrics, East Tennessee State University, Johnson City, TN 37614-0578, USA. stone@etsu.edu.
authors.forename: William L
authors.initials: WL
authors.lastname: Stone
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D008297:Male; D015394:Molecular Structure; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011355:Prodrugs; D011471:Prostatic Neoplasms / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D011355:Prodrugs; D017382:Reactive Oxygen Species; D005978:Glutathione; D000409:Alanine