title: Transcriptional and post-transcriptional targeting for enhanced transient gene expression in CHO cells.
abstract: OBJECTIVE
  To develop a simple approach to increase titers of transient gene expression in CHO cells without relying on host cell line engineering as recent reports suggest that for PEI-mediated transfections, under optimized conditions, DNA delivery into cells and nuclei is not the limiting factor.
  
  
  RESULTS
  N, N-Dimethyl acetamide (DMA) was utilized to enhance transcription. To target post-transcriptional events, we evaluated the co-expression of various genes involved in the unfolded protein response, namely XBP1S, ATF4, CHOP and HSPA5. XBP1S overexpression led to a 15-85 % increase in titer for multiple therapeutic proteins. Mechanistic studies confirmed that addition of 0.125 % DMA increased transgene mRNA levels as expected. However, overexpression of XBP1S had no effect on transgene mRNA levels, indicating that it influenced post-transcriptional events. Since DMA and XBP1S targeted different pathways, the combination of the two approaches led to an additive improvement in protein titer (150-250 % titer increase).
  
  
  CONCLUSIONS
  Transcriptional and post-transcriptional pathways of transient gene expression can be targeted to increase titers without resorting to host cell line engineering in a simple, short, 7 day production process.
authors: Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, 46285, USA.
authors: Yashas
authors: Y
authors: Rajendra
authors: Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, 46285, USA.
authors: Maria D
authors: MD
authors: Hougland
authors: Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, 46285, USA.
authors: Matthew G
authors: MG
authors: Schmitt
authors: Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN, 46285, USA. barnard_gavin_c@lilly.com.
authors: Gavin C
authors: GC
authors: Barnard
mesh_terms: D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D015870:Gene Expression; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D011994:Recombinant Proteins
keywords: Dimethyl acetamide; Glutamine synthetase (GS)-CHO; Polyethyleneimine; Transient gene expression; Transient transfection; Unfolded protein response; XBP1S