Generation of CHO cell mutants for growth control

The use of a temperature switch to control the growth and productivity of temperature-sensitive (ts) mutants was investigated, in order to extend the productive life span of recombinant CHO cells in batch culture. Bromodeoxyuridine was used at 39°C to select mutagenized CHO-Kl cells, which resulted in the isolation of 31 temperature-sensitive mutants that were growth-inhibited at 39°C. Two of these mutants were successfully transfected with the gene for tissue inhibitor of metalloproteinases (TIMP) using glutamine synthetase amplification, and a permanent recombinant cell line established (5G1-B1) that maintains the ts-phenotype.