Correlating amino acid profiles with improved expression capability of superior CHO based expression platforms
A novel modified CHO cell line was constructed by expressing a three gene combination of Bclx(L), Aven and BECN1 which are critical targets of the apoptosis and autophagy pathways. This synergistic combination significantly improved cell viability as well as Rituximab (RTX) expression by 7.5 fold. A comparative amino acid analysis of the modified and control cultures both with and without RTX expression showed interesting changes in amino acid uptake rates. We first compared the utilization of amino acids in the control cells without RTX expression to the control cells with RTX expression where it declined significantly in the later half of the culture with the maximum decrease observed with tyrosine, which instead of uptake got secreted into the medium. The uptake of aspartic and glutamic acid also fell drastically during this period demonstrating the deleterious effect of RTX expression on cellular health. When the modified cells were used for RTX expression, there was conversely a slight increase in amino acid consumption in the later part of the culture with the maximum increase observed with alanine and tyrosine. The differential amino acid consumption rates provided us with an indirect measure of improved cellular health and ability of the modified cells to counter the cellular stress associated with RTX expression. Amino acid analysis could thus become a useful predictive tool to identify the critical features of better host expression platforms.