Valproic acid enhances recombinant mRNA and protein levels in transiently transfected Chinese hamster ovary cells

Enhanced CHO Cell-Based Transient Gene Expression with the Epi-CHO Expression System

“…Furthermore, through the screening of various media, we have developed a serum-free transient process incorporating mild-hypothermia with an optimized lipofection protocol that has generated up to 140 mg/l of mAb, with no additional feeding post-transfection. This represents a 64% increase on the highest previously reported titer in CHO cells [8]. The Epi-CHO system represents a high-producing CHO cell-based TGE system, providing substantial recombinant protein yields.…”

“…In addition, we show the effectiveness of the Epi-CHO system for the production of recombinant mAbs in batch culture, achieving a titer of 140 mg/l, which represents a 64% increase over the previously highest reported level of transient mAb production in CHO cells [8].…”

“…TGE yields have improved dramatically over the last decade due to research into a variety of parameters, including; the expression vector [1], the development of advanced chemically defined and serum-free media, their supplementation, and the feeding strategy implemented post-transfection [2,3] and the direct addition of a variety of chemical agents such as epigenetic modulators [4], cell cycle regulators [5], growth factors [6], and agents thought to directly enhance transfection efficiency and promote plasmid maintenance [3]. Culturing under mild hypothermic conditions has also resulted in significant improvements in expression levels [6][7][8].…”

“…EBNA-1 drives the replication and maintenance of plasmid DNA containing the EBV latent origin of replication, OriP, which in turn promotes elevated and prolonged expression of the recombinant protein of interest [10][11][12][13]. Recent reports using the HEK.EBNA system have generated mAb titers in excess of 1 g/l [14], whereas, the highest reported mAb titers generated from CHO cellbased TGE in the literature are considerably lower and range from 60 to 90 mg/l [3,7,8]. Stably transfected CHO cells remain the host of choice for the large-scale commercial production of therapeutic proteins and yields in these systems now routinely exceed 1 g/l.…”

A simple high-yielding process for transient gene expression in CHO cells

“…In the latter, transient recombinant monoclonal antibody yields up to 1 g/L have been reported (Backliwal et al, 2008a). In contrast, the highest reported volumetric yields in batch cultures of transiently transfected CHO cells have been 80-100 mg/L (Ye et al, 2009;Wulhfard et al, 2008Wulhfard et al, , 2010. For HEK-293 cells, the highest yields have been obtained by transfection with linear 25 kDa polyethylenimine (PEI) at a density of 20 × 10 6 cells/mL with direct addition of plasmid DNA and PEI to the culture followed by dilution with production medium containing valproic acid (VPA), a histone deacetylase inhibitor (Backliwal et al, 2008a,b,c).…”