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

Abstract

To enhance the production of recombinant human transforming growth factor-beta1 (rhTGF-beta 1) in Chinese hamster ovary (CHO) cells, rhTGF-beta 1 was first characterized for endocytosis, signaling pathway, and overall maturation process. The mature rhTGF-beta 1 used for clinical application was internalized into CHO cells and inhibited the growth of CHO cells in a dose-dependent manner. However, mature rhTGF-beta 1 was mostly produced in the form of latent rhTGF-beta 1 in cultures of recombinant CHO (rCHO) cells producing rhTGF-beta 1 (CHO-rhTGF-beta 1). The concentration of active mature rhTGF-beta 1 in the culture supernatant of CHO-rhTGF-beta 1 cells was not high enough to compromise yield. In addition, a significant amount of unprocessed precursors was produced by CHO-rhTGF-beta 1 cells. Overexpression of PACEsol, a soluble form of furin, in CHO-rhTGF-beta 1 cells was effective for the proteolytic cleavage of unprocessed precursors. The highest mature rhTGF-beta 1 concentration (6.4 mu g 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-beta 1 with respect to the overall maturation process, signaling pathway, and endocytosis is essential for effectively enhancing the production of mature rhTGF-beta 1 in CHO cells.