Establishment of Stable Chinese Hamster Ovary Cells Expressing Codon-Optimized Human Interferon-β Gene

Background: Codon optimization is an efficient approach to achieve a higher level of heterologous gene expression and generate productive recombinant mammalian cell lines. In our previous work, based on the codon usage preference of Chinese hamster ovary (CHO) cells, a codon-optimized human interferon-beta (opt-hIFN-β) gene was redesigned and transiently expressed in a suspension-adapted CHO (CHO-s) cell line. Our results indicated a 2.8-fold increase in the expression level of the codon-optimized gene compared to the unmodified sequence. Objectives: In the current work, based on our previous results, a stable CHO-K1 cell line expressing the opt-hIFN-β gene was engineered, in which the opt-hIFN-β gene expression was confirmed by dot and western blotting analyses. Methods: The designed opt-hIFN-β sequence was digested and cloned into a pcDNA3.0 shuttle vector downstream to the cytomegalovirus (CMV) promoter. The verified recombinant plasmid was then linearized and transfected into a CHO-K1 cell line to integrate the opt-hIFN-β gene into the CHO-K1 genome. The transfected cells were then grown under the selective pressure of 450 µg/mL of G418 to develop a stable CHO-K1 cell line expressing the opt-hIFN-β gene. The enzyme-linked immunosorbent assay (ELISA) and dot and western blotting analyses were carried out to verify hIFN-β protein expression. Results: ELISA and dot and western blotting analyses confirmed the expression of hIFN-β in the stably-transfected CHO-K1 cells. Conclusions: Stable expression of the opt-hIFN-β gene in the CHO-K1 cell line was verified by ELISA and dot and western blotting analyses. This study was a pioneering work for further production of recombinant hIFN-β in the bioreactor.