Integrated Pathway Analysis of Genome-Wide Expression Changes Associated with Serum-Free Suspension Adaptation of an Antibody-Producing Chinese Hamster Ovary (CHO) Cell Line

Genome-wide expression profiles of antibody-producing CHO cells during suspension-adaptation into a serum-free medium have been characterized using CHO DNA microarrays. The transcriptome was analyzed with the RNA samples of cultures collected prior to and after adaptation. Over 500 genes and many major pathways were found to be profoundly affected by suspension adaptation. Among the down-regulated pathways were cell-cell adhesion, cell cycle, nucleotide synthesis, transcription, translation, vesiclular transport, microfilaments, and motor proteins. Among the up-regulated pathways were extracellular matrix, basement membrane, hypoxia signal pathway, antioxidant response elements, amino acid transporters as well as protein processing mechanisms in ER and Golgi. Most strikingly, the metabolic pathways were shifted to the de novo synthesis of fatty acids and sterols. The genes for fatty acid transport were significantly up-regulated and among them the mRNA of several key enzymes increased several hundred fold.