Characterization of proliferating cell nuclear antigen (PCNA) isoforms in normal and cancer cells: There is no cancer-associated form of PCNA

In order to clarify the status of PCNA in normal and transformed cells, we performed analysis of this protein by 2D-PAGE, Western blot and mass spectrometry. All the cell lines examined contained the major PCNA form (pI 4.57/30 kDa), that is not post-translationally modified. In addition to the major form, two minor isoforms (pI 4.52/30 kDa and pI 4.62/30 kDa) were also detected in all the cell lines examined. However, the level of PCNA in cancer cells is 5-6 folds higher than those in primary and most of the immortalized cells. Taken together, the significant difference in PCNA status between cancer and normal cells is not at the post-translational modifications but in the overall levels of PCNA. Crown Copyright (c) 2007 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies. All rights reserved.