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Transcriptional and post-transcriptional targeting for enhanced transient gene expression in CHO cells

Rajendra, Yashas, Hougland, Maria D., Schmitt, Matthew G., Barnard, Gavin C.
Biotechnology letters 2015 v.37 no.12 pp. 2379-2386
DNA, biopharmaceuticals, engineering, gene overexpression, messenger RNA, transcription (genetics), transgenes, unfolded protein response
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). CONCLUSION: 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.