Recombinant cyclin E expression activates proliferation and obviates surface attachment of chinese hamster ovary (CHO) cells in protein‐free medium

Publisher Website
Google Scholar
Abstract
Exogenous growth factors normally required in cell culture activate cell proliferation via the molecular controls of cell‐cycle progression. Highly differing influences of mitogenic stimulation of Chinese hamster ovary (CHO) cells by insulin and basic fibroblast growth factor(bFGF) have been clearly observed in a defined protein‐free medium. CHO K1 cells stimulated only with insulin grow with flattened cell morphology and extensive cell–cell contact, whereas stimulation with only bFGF or bFGF plus insulin results in loss of cell‐cell contact and a transformed and rounded‐up morphology. Compared with insulin‐stimulated cells, bFGF‐stimulated cells exhibit a relatively long G1, and short S phase, and contain higher levels of cyclin E. Observation of elevated levels of cyclin E in wild‐type CHO K1 cells mitogenically stimulated by basic fibroblast growth factor motivated transfection of these cells by a cyclin E expression vector. These transfectants grew rapidly in protein‐free basal medium and had similar cyclin b levels, distributions of nuclear cell‐cycle times, and cell morphologies as bFGF‐stimutated CHO K1 culture. Metabolic engineering of cell‐cycle regulation thus bypasses exogenous growth factor requirements, addressing a priority objective in economical, reproducible, and safe biopharmaceutical manufacturing. © 1995 John Wiley & Sons Inc.