Basic Research
Copyright ©2006 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Mar 14, 2006; 12(10): 1569-1576
Published online Mar 14, 2006. doi: 10.3748/wjg.v12.i10.1569
Cis-hydroxyproline-induced inhibition of pancreatic cancer cell growth is mediated by endoplasmic reticulum stress
Christoph Mueller, Joerg Emmrich, Robert Jaster, Dagmar Braun, Stefan Liebe, Gisela Sparmann
Christoph Mueller, Joerg Emmrich, Robert Jaster, Stefan Liebe, Gisela Sparmann, Department of Medicine, Division of Gastroenterology, University of Rostock, Germany
Dagmar Braun, Riemser Arzneimittel AG, Greifswald, Germany
Author contributions: All authors contributed equally to the work.
Supported by the Bundeministerium für Bildung und Forschung, grant 01ZZ0108
Correspondence to: Gisela Sparmann, MD, Department of Medicine, Division of Gastroenterology, University of Rostock, Ernst-Heydemann-Str. 6, D-18057 Rostock, Germany.
Telephone: +49-381-4945954 Fax: +49-381-4947482
Received: August 17, 2005
Revised: September 1, 2005
Accepted: October 9, 2005
Published online: March 14, 2006

AIM: To investigate the biological effects of cis-hydroxyproline (CHP) on the rat pancreatic carcinoma cell line DSL6A, and to examine the underlying molecular mechanisms.

METHODS: The effect of CHP on DSL6A cell proliferation was assessed by using BrdU incorporation. The expression of focal adhesion kinase (FAK) was characterized by Western blotting and immunofluorescence. Induction of endoplasmic reticulum (ER) stress was investigated by using RT-PCR and Western blotting for the glucose-related protein-78 (GRP78) and growth arrest and DNA inducible gene (GADD153). Cell viability was determined through measuring the metabolic activity based on the reduction potential of DSL6A cells. Apoptosis was analyzed by detection of caspase-3 activation and cleavage of poly(ADP-ribose) polymerase (PARP) as well as DNA laddering.

RESULTS: In addition to inhibition of proliferation, incubation with CHP induced proteolytic cleavage of FAK and a delocalisation of the enzyme from focal adhesions, followed by a loss of cell adherence. Simultaneously, we could show an increased expression of GRP78 and GADD153, indicating a CHP-mediated activation of the ER stress cascade in the DSL6A cell line. Prolonged incubation of DSL6A cells with CHP finally resulted in apoptotic cell death. Beside L-proline, the inhibition of intracellular proteolysis by addition of a broad spectrum protease inhibitor could abolish the effects of CHP on cellular functions and the molecular processes. In contrast, impeding the activity of apoptosis-executing caspases had no influence on CHP-mediated cell damage.

CONCLUSION: Our data suggest that the initiation of ER stress machinery by CHP leads to an activation of intracellular proteolytic processes, including caspase-independent FAK degradation, resulting in damaging pancreatic carcinoma cells.

Keywords: Cis-hydroxyproline, Pancreatic cancer cell, endoplasmic reticulum stress, FAK, Caspase-3