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Open Access Research article

Identification of oxidized protein hydrolase as a potential prodrug target in prostate cancer

Christopher A McGoldrick1, Yu-Lin Jiang2, Victor Paromov1, Marianne Brannon1, Koyamangalath Krishnan3 and William L Stone1*

Author Affiliations

1 Department of Pediatrics, East Tennessee State University, P.O. Box 70579, Johnson City, TN 37614, USA

2 Department of Chemistry, East Tennessee State University, Johnson City, TN USA

3 Division of Hematology-Oncology, Department of Internal Medicine, East Tennessee State University, Johnson City, TN USA

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BMC Cancer 2014, 14:77  doi:10.1186/1471-2407-14-77

Published: 10 February 2014

Abstract

Background

Esterases are often overexpressed in cancer cells and can have chiral specificities different from that of the corresponding normal tissues. For this reason, ester prodrugs could be a promising approach in chemotherapy. In this study, we focused on the identification and characterization of differentially expressed esterases between non-tumorigenic and tumorigenic prostate epithelial cells.

Methods

Cellular lysates from LNCaP, DU 145, and PC3 prostate cancer cell lines, tumorigenic RWPE-2 prostate epithelial cells, and non-tumorigenic RWPE-1 prostate epithelial cells were separated by native polyacrylamide gel electrophoresis (n-PAGE) and the esterase activity bands visualized using α-naphthyl acetate or α-naphthyl-N-acetylalaninate (ANAA) chiral esters and Fast Blue RR salt. The esterases were identified using nanospray LC/MS-MS tandem mass spectrometry and confirmed by Western blotting, native electroblotting, inhibition assays, and activity towards a known specific substrate. The serine protease/esterase oxidized protein hydrolase (OPH) was overexpressed in COS-7 cells to verify our results.

Results

The major esterase observed with the ANAA substrates within the n-PAGE activity bands was identified as OPH. OPH (EC 3.4.19.1) is a serine protease/esterase and a member of the prolyl oligopeptidase family. We found that LNCaP lysates contained approximately 40% more OPH compared to RWPE-1 lysates. RWPE-2, DU145 and PC3 cell lysates had similar levels of OPH activity. OPH within all of the cell lysates tested had a chiral preference for the S-isomer of ANAA. LNCaP cells were stained more intensely with ANAA substrates than RWPE-1 cells and COS-7 cells overexpressing OPH were found to have a higher activity towards the ANAA and AcApNA than parent COS-7 cells.

Conclusions

These data suggest that prodrug derivatives of ANAA and AcApNA could have potential as chemotherapeutic agents for the treatment of prostate cancer tumors that overexpress OPH.