Fluorescent proteins in animal cells for process development: Optimization of sodium butyrate treatment as an example

• Published in: Biotechnology and bioengineering Vol. 77; no. 5; pp. 528 - 537
• Main Authors: Hunt, Lisa, Batard, Pascal, Jordan, Martin, Wurm, Florian M.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 05.03.2002; Wiley
• Subjects: Animal cells; Animals; Biological and medical sciences; Biotechnology; Butyrates - pharmacology; Cell Count; Cell Culture Techniques - methods; CHO cells; CHO Cells - cytology; CHO Cells - physiology; Cricetinae; Dose-Response Relationship, Drug; Eukaryotic cell cultures; fluorescent proteins; Fundamental and applied biological sciences. Psychology; Gene Expression; GFP; Glucose - metabolism; Green Fluorescent Proteins; Indicators and Reagents - metabolism; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Methods. Procedures. Technologies; Microscopy, Fluorescence - methods; Miscellaneous; process development tool; recombinant protein production; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; sodium butyrate; Transgenes; YFP; Productivity; Cell culture; Animal; Production; Green fluorescent protein; Fluorescence; Measurement method; Recombinant protein; Gene expression; CHO cell line; Optimization
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.10108

Fluorescent proteins expressed in mammalian cells can be quantified quickly and noninvasively with a standard fluorescence plate reader. We have previously exploited this quality in cell growth assessment (Hunt et al., 1999b). In this work, different CHO cell lines constitutively expressing fluorescent proteins were evaluated as model systems for process development and optimization. Our results demonstrate that the fluorescence of these cell lines quickly reveals conditions that might improve the overall productivity. Sodium butyrate, a well‐known yet unpredictable enhancer of production, was chosen for this study. Due to the competing effects of sodium butyrate (“butyrate”) on expression and cell number, the maximal overall productivity represents a compromise between enhancement of production and toxicity. Based on fluorescence only, it is possible to separate effects on cell number and specific production by combining microplate fluorescence measurements with data obtained by flow cytometry. This allows for rapid screening of different clones without counting cells or quantifying the recombinant protein, a highly attractive feature if the expression of green fluorescent protein (GFP) was correlated to that of a protein of interest. For all clones tested, negative effects of butyrate on proliferation were similar, while net enhancement of expression was characteristic for each clone. Therefore, it is necessary to optimize treatment for each individual clone. This work demonstrates that, based on the fluorescence of GFP‐expresssing cell lines, it is possible to examine noninvasively three critical, generic parameters of butyrate treatment: butyrate concentration, exposure time, and culture phase at the time of addition. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 528–537, 2002; DOI 10.1002/bit.10108