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Journal of Biomedicine and Biotechnology
Volume 2012, Article ID 425907, 12 pages
http://dx.doi.org/10.1155/2012/425907
Research Article

Identification of Pigment Epithelium-Derived Factor Protein Forms with Distinct Activities on Tumor Cell Lines

1Section of Protein Structure and Function, LRCMB, National Eye Institute, NEI, Bethesda, MD 20892-0608, USA
2Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, NEI, Bethesda, MD 20892, USA
3Center for Cancer Research (CCR), National Cancer Institute, Bethesda, MD 20892, USA
4Otsuka Maryland Medicinal Laboratories, Rockville, MD 20850, USA
5Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, USA

Received 16 December 2011; Accepted 7 March 2012

Academic Editor: Crispin Dass

Copyright © 2012 P. Subramanian et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose. Pigment epithelium-derived factor (PEDF) is a multifunctional serpin. The purpose of this study is to identify PEDF protein forms and investigate their biological activities on tumor cell lines. Methods. Recombinant human PEDF proteins were purified by cation- and anion-exchange column chromatography. They were subjected to SDS-PAGE, IEF, deglycosylation, heparin affinity chromatography, and limited proteolysis. Cell viability, real-time electrical impedance of cells, and wound healing assays were performed using bladder and breast cancer cell lines, rat retinal R28, and human ARPE-19 cells. Results. Two PEDF protein peaks were identified after anion-exchange column chromatography: PEDF-1 eluting with lower ionic strength than PEDF-2. PEDF-1 had higher pI value and lower apparent molecular weight than PEDF-2. Both PEDF forms were glycosylated, bound to heparin, and had identical patterns by limited proteolysis. However, PEDF-2 emerged as being highly potent in lowering cell viability in all tumor cell lines tested, and in inhibiting tumor and ARPE-19 cell migration. In contrast, PEDF-1 minimally affected tumor cell viability and cell migration but protected R28 cells against death caused by serum starvation. Conclusion. Two distinct biochemical forms of PEDF varying in overall charge have distinct biological effects on tumor cell viability and migration. The existence of PEDF forms may explain the multifunctional modality of PEDF.