Cell Line Development

Cell line development is the process by which the cellular machinery is co-opted to manufacture therapeutic biologics or other proteins of interest. You can use different expression systems for cell line development: bacterial, plant-based, yeast, mammalian. Most commonly used for the production of the complex protein is Chinese hamster ovary (CHO), cells grown in suspension cultures for eventual use in bioreactors at the manufacturing stage.

Cell Line Development Process

The development of these cell lines is a long and arduous process with numerous steps and challenges (Figure 1). Once CHO cells have been transfected with the construct of interest a selection step is required to enrich for those cells that have taken up the construct. Single cells must then be isolated, grown into colonies, and assayed for protein production. Once this production screen has been accomplished, the top candidates are expanded and maintained to test for expression stability. Eventually the top hits are further optimized in different media conditions to enhance expression or other protein attributes (e.g. glycosylation) before scaling up to production levels. Because this process takes months to complete, there are many more challenges than a typical short-term cellular workflow. First, maintaining sterility is essential during various manipulations and throughout the weeks of growth from a single cell. Secondly, as with most screens, the throughput required to identify a handful of optimal clones typically requires thousands of wells. This throughput then tapers off after the hit picking phase, so one should schedule overlapping campaigns to maximize resources. Finally, as clones move through the system and are reformatted into lower density plates during hit picking, all previously recorded data must be tracked as these cell lines are established. We have overcome these challenges by automating the establishment and screening of clones for cell line development.