Life at the periphery: what makes CHO cells survival talents

Abstract

The production of biopharmaceuticals relies on robust cell systems that can produce recombinant proteins at high levels and grow and survive in the stressful bioprocess environment. Chinese hamster ovary cells (CHO) as the main production hosts offer a variety of advantages including robust growth and survival in a bioprocess environment. Cell surface proteins are of special interest for the understanding of how CHO cells react to their environment while maintaining growth and survival phenotypes, since they enable cellular reactions to external stimuli and potentially initiate signaling pathways. To provide deeper insight into functions of this special cell surface sub-proteome, pathway enrichment analysis of the determined CHO surfaceome was conducted. Enrichment of growth/ survival-pathways such as the phosphoinositide-3-kinase (PI3K)–protein kinase B (AKT), mitogen-activated protein kinase (MAPK), Janus kinase/signal transducers and activators of transcription (JAK-STAT), and RAP1 pathways were observed, offering novel insights into how cell surface receptors and ligand-mediated signaling enable the cells to grow and survive in a bioprocess environment. When supplementing surfaceome data with RNA expression data, several growth/survival receptors were shown to be co-expressed with their respective ligands and thus suggesting self-induction mechanisms, while other receptors or ligands were not detectable. As data about the presence of surface receptors and their associated expressed ligands may serve as base for future studies, further pathway characterization will enable the implementation of optimization strategies to further enhance cellular growth and survival behavior. Key points • PI3K/AKT, MAPK, JAK-STAT, and RAP1 pathway receptors are enriched on the CHO cell surface and downstream pathways present on mRNA level. • Detected pathways indicate strong CHO survival and growth phenotypes. • Potential self-induction of surface receptors and respective ligands. Graphical abstract

Long term culture promotes changes to growth, gene expression, and metabolism in CHO cells that are independent of production stability

“…We observed upregulated genes involved in the MAPK‐ERK and PI3K‐Akt signaling pathways at LP (Supporting Information: Figures S4 and S5 and Table S1). Whilst both the MAPK‐ERK and PI3K‐Akt signaling pathways participate in multiple biological processes and are key for cell function, a recent study showed that activation of these pathways supported cell growth and survival during the environmental conditioning during bioprocessing scale‐up (Jerabek et al, 2022). In addition, we found that both cell lines showed increased expression of transcripts linked to focal adhesion signaling (Supporting Information: Table S1).…”

“…A phosphoproteomic analysis of human cancer cells showed constitutive activation of the PI3K/Akt and MAPK/ERK signaling pathways as a driver of cell proliferation (Y. Y. Lee et al, 2013) and of genomic instability (Ma et al, 2018). A recent CHO cell surfactome revealed the enrichment of these two pathways in CHO cells (Jerabek et al, 2022), suggesting that cell surface receptors and associated ligands play fundamental roles in controlling the proliferative status of CHO cells.…”

“…Lee et al, 2013) and of genomic instability (Ma et al, 2018). A recent CHO cell surfactome revealed the enrichment of these two pathways in CHO cells (Jerabek et al, 2022), suggesting that cell surface receptors and associated ligands play fundamental roles in controlling the proliferative status of CHO cells.…”