Engineering CHO cell metabolism for growth in galactose

Abstract

Background Chinese hamster ovary (CHO) cells are one of the main hosts for industrial production of therapeutic proteins, owing to well-characterized technologies for gene trans-fection, amplification, and selection of high-producer clones. This has motivated the search for different strategies for the improvement of their specific productivity being one of the key points for this approaches the reduction of metabolic end-products like lactate and ammonia. The use of different carbon sources has been an alternative solution for this problem, as they are metabolized more slowly than glucose leading to lower production of metabolic end-products [1]. Particularly, it has been observed that cultures in presence of glucose and galac-tose undergo a metabolic shift in which they are capable of remetabolize lactate. However, the specific growth rate is diminished due to a slower metabolism associated to the incorporation of galactose [2]. In addition, cells are unable to survive with galactose as their unique carbon source [3]. In this work we aim at identifying culture conditions that extend the culture's viability for tPA producing CHO cells in media with combined glucose and galac-tose as carbon sources. Furthermore, we propose reducing the production of secondary metabolites by over-expressing galactokinase (GALK1), a bottleneck point in the galactose metabolism.