Inhibition of endogenous miR‐23a/miR‐377 in CHO cells enhances difficult‐to‐express recombinant lysosomal sulfatase activity

Abstract Difficult‐to‐express (DTE) recombinant proteins such as multi‐specific proteins, DTE monoclonal antibodies, and lysosomal enzymes have seen difficulties in manufacturability using Chinese hamster ovary (CHO) cells or other mammalian cells as production platforms. CHO cells are preferably used for recombinant protein production for their ability to secrete human‐like recombinant proteins with posttranslational modification, resistance to viral infection, and familiarity with drug regulators. However, despite huge progress made in engineering CHO cells for high volumetric productivity, DTE proteins like recombinant lysosomal sulfatase represent one of the poorly understood proteins. Furthermore, there is growing interest in the use of microRNA (miRNA) to engineer CHO cells expressing DTE proteins to improve cell performance of relevant bioprocess phenotypes. To our knowledge, no research has been done to improve CHO cell production of DTE recombinant lysosomal sulfatase using miRNA. We identified miR‐23a and miR‐377 as miRNAs predicted to target SUMF1, an activator of sulfatases, using in silico prediction tools. Transient inhibition of CHO endogenous miR‐23a/miR‐377 significantly enhanced recombinant sulfatase enzyme‐specific activity by ~15–21% compared to scramble without affecting cell growth. Though inhibition of miR‐23a/miR‐377 had no significant effect on the mRNA and protein levels of SUMF1, overexpression of miR‐23a/377 caused ~30% and ~27–29% significant reduction in endogenous SUMF1 protein and mRNA expression levels, respectively. In summary, our data demonstrate the importance of using miRNA to optimize the CHO cell line secreting DTE recombinant lysosomal sulfatase.