Differential Protein Expression Induced by c-Myc Over-Expression: Proteomic Analysis of a CHO Cell Line with Increased Proliferation Capacity

To examine the role of the transcription factor Myc in cell culture processes a stable adherent Chinese Hamster Ovary (CHO) cell line, under constitutive controlled over-expression of the human c-myc gene was produced (Ifandi and Al-Rubeai, 2003). A significant increase in proliferation and a reduction in serum dependency resulting from c-myc over-expression were observed. Although c-myc was responsible for the induction of higher apoptotic rate when compared with the control, the impact was negligible compared to the overall increase in proliferation capacity. A proteomic investigation identified over 100 protein spots on 2D-gel that exhibited notable expression alterations when compared to the wildtype CHO cell line. Based on mass spectrometry identification, some of the morphological changes and the increased proliferative capacity of the modified cell line could be explained. An up-regulation of nucleolin protein and ATP synthetase was associated to the higher proliferation rate. Annexin A2, involved in adhesion, was down-regulated which may explain why the modified cell line has a tendency to be less adherent. The down-regulation of F-actin capping protein, linked to the secretory pathway, verified the small reduction in productivity of recombinant human secreted alkaline phosphatase. This on going investigation has given us a better understanding of some of the factors involved in adherence, apoptosis, proliferation capacity and productivity. The study has also provided possible multiple cell engineering targets to improve suspension adaptation, proliferation capacity of industrially important cell lines.