Abstract
Selection of high producing cell lines to produce maximum product concentration is a challenging and time consuming task for the biopharmaceutical industry. The identification of early markers to predict high productivity will significantly reduce the time required for new cell line development. This study identifies candidate determinants of high productivity by profiling the molecular and morphological characteristics of a panel of six Chinese Hamster Ovary (CHO) stable cell lines with varying recombinant monoclonal antibody productivity levels ranging between 2 and 50 pg/cell/day. We examined the correlation between molecular parameters and specific productivity (qp) throughout the growth phase of batch cultures. Results were statistically analyzed using Pearson correlation coefficient. Our study revealed that, overall, heavy chain (HC) mRNA had the strongest association with qp followed by light chain (LC) mRNA, HC intracellular polypeptides, and intracellular antibodies. A significant correlation was also obtained between qp and the following molecular markers: growth rate, biomass, endoplasmic reticulum, and LC polypeptides. However, in these cases, the correlation was not observed at all-time points throughout the growth phase. The repeated sampling throughout culture duration had enabled more accurate predictions of productivity in comparison to performing a single-point measurement. Since the correlation varied from day to day during batch cultivation, single-point measurement was of limited use in making a reliable prediction.
Highlights
The slow progression of recombinant protein production in the biopharmaceutical industry is mainly due to the low productivity of host cell lines [1,2,3]
The suspension-variant derivative of Chinese Hamster Ovary (CHO)-K1 (CHOK1SV) cell lines were generated by transfection with glutamine synthetase (GS) expression vector, pcB72.3 containing light chain (LC) and heavy chain (HC), each driven by the hCMV-MIE promoter [40,41]
The results indicate that, consistent to the ratio of LC to HC GCNs, LC to HC mRNA ratios show that LCs are present abundantly in all six cell lines, though were found to be lower in CL 47[1] and CL 38[5]
Summary
The slow progression of recombinant protein production in the biopharmaceutical industry is mainly due to the low productivity of host cell lines [1,2,3]. The lack of correlation was postulated to be due to the limited resources of processing and secretory apparatus during the folding and assembly step that primarily takes place in the endoplasmic reticulum (ER) [21] Certain transcription regulators, such as X-box binding protein (X-BP1) and activating transcription factor 4 (ATF4) and ER proteins, including binding protein (BiP), protein disulphide isomerise (PDI) and glucoseregulated proteins 94 (GRP94), have been shown to influence the ER expansion during protein synthesis and affecting the secretion rate of antibody [22,23,24,25,26,27,28,29,30,31,32,33]. It has been shown that low expression of ER proteins in a small ER volume can result in antibody aggregation [34]
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