Inhibition of microRNA-let-7a Increases the Specific Productivity of Antibody-Producing CHO Cell Lines

Chinese hamster ovary cells (CHO) are the preferred cell line for the production of recombinant biopharmaceuticals, which constitutes a multi-billion dollar global market. Major challenges to improving protein productivity of CHO in large-scale production cultures include growth level, cellular stress, and translation rate. Because microRNA (miR, miRNA) can simultaneously perturb multiple pathways by inhibiting translation or destabilizing different mRNAs, we explored their utility to extend the cell growth phase or alter protein production per cell (specific productivity) with the goal of enhancing current optimization techniques to increase the production capacity of CHO cell cultures. To investigate the effect of altered microRNA expression on CHO cell viability and specific productivity, two clinically relevant antibody-producing CHO cell lines were stably transduced with lentiviral vectors encoding nine different miRNAs or anti-miRNAs based on their potential involvement in pathways critical for recombinant protein production. Inhibition of miR-let-7a led to a 50%~68% increase in specific productivity in two recombinant antibody-producing cell lines. Furthermore, following miR-let-7a inhibition, we identified increased expression of its targets HMGA2, MYC, NF2, NIRF, RAB40C, and eIF4a which are important mediators of apoptosis, protein translation, and cellular metabolism. Overall, this work provides proof of concept that exogenous microRNA modifications can positively affect specific productivity of CHO cell cultures and highlights the potential of miR-let-7a to have a broad impact on the complex biological functions necessary for improving the capabilities of CHO cell lines.