Generation of high-producing CHO cell lines using cell picking system combined with fluorescent labeling of secreted products

To facilitate the commercialization of protein therapeutics, the establishment of a mass production system is necessary for cost reduction and ensuring a stable supply. The common method for producing protein therapeutics is a mammalian cell-based expression system, predominantly utilizing Chinese hamster ovarian (CHO) cells. In the process of generating stable CHO cell lines expressing protein therapeutics, the most critical step is the selection of high producer cell lines. While limiting dilution has been a classical method for selecting candidate clones, it is time-consuming and lacks the ability to evaluate cell productivity. To address this issue, in this study, a novel selection method utilizing Cell Picking System was established and compared with limiting dilution in identifying high-producer clones. In this method, transfected CHO cells were loaded into a microchamber containing 20-µm-diameter microwells, allowing secreted proteins from individual cells to be detected using fluorescently labeled antibodies. The results of small-scale production test demonstrated that clones with higher productivity distributions were enriched using Cell Picking System. In addition, the highest clone achieved 2.34 g/L protein production, suggesting potential applicability for commercial supply with some modifications in cell culture conditions. This method supports high-throughput applications of protein therapeutics to the industrial scale and addresses the limitations of traditional selection methods.