Enhancing the production of recombinant human TGF‐β1 through an understanding of TGF‐β1 synthesis, signaling, and endocytosis in CHO cells

To enhance the production of recombinant human transforming growth factor‐beta1 (rhTGF‐β1) in Chinese hamster ovary (CHO) cells, rhTGF‐β1 was first characterized for endocytosis, signaling pathway, and overall maturation process. The mature rhTGF‐β1 used for clinical application was internalized into CHO cells and inhibited the growth of CHO cells in a dose‐dependent manner. However, mature rhTGF‐β1 was mostly produced in the form of latent rhTGF‐β1 in cultures of recombinant CHO (rCHO) cells producing rhTGF‐β1 (CHO‐rhTGF‐β1). The concentration of active mature rhTGF‐β1 in the culture supernatant of CHO‐rhTGF‐β1 cells was not high enough to compromise yield. In addition, a significant amount of unprocessed precursors was produced by CHO‐rhTGF‐β1 cells. Overexpression of PACEsol, a soluble form of furin, in CHO‐rhTGF‐β1 cells was effective for the proteolytic cleavage of unprocessed precursors. The highest mature rhTGF‐β1 concentration (6.4 μg mL −1 ) was obtained with the PACEsol‐expressing clone, which was approximately 45% higher than that of the parental clone ( P < 0.01). Thus, a comprehensive understanding of the intrinsic properties of rhTGF‐β1 with respect to the overall maturation process, signaling pathway, and endocytosis is essential for effectively enhancing the production of mature rhTGF‐β1 in CHO cells.