ABSTRACT
A high-density cell culture method was successfully established in P. pastoris with the alcohol oxidase I (AOXI) promoter in order to produce large quantities of recombinant human angiostatin (AS) which has been reported to have antiangiogenic activity. A preliminary study on fermentation conditions in shaking flasks indicated that adequacy of biomass is beneficial to obtain more products. The fermentation was carried out in a 10 l bioreactor with 5 l modified growth medium recommended by Invitrogen at 30 degrees C. The cells were first grown in glycerol-PTM4 trace salts for 24 h. When the cell density reached A(600) = 125, methanol-PTM4 trace salts was added to induce the expression of AS. During the fermentation, dissolved oxygen level was maintained at 20-30%, pH was controlled at 5 by the addition of 7 M NH(4)OH and the biomass was maintained at about A(600) = 200. After 60 h of induction, the secreted AS was 153 mg/l. The recombinant AS inhibited the angiogenesis on CAM and suppressed the growth of B16 melanoma in C57BL/6J mice (P \0.01).
Subject(s)
Alcohol Oxidoreductases/genetics , Angiostatins/biosynthesis , Pichia/genetics , Angiogenesis Inhibitors/genetics , Angiogenesis Inhibitors/metabolism , Angiogenesis Inhibitors/pharmacology , Angiostatins/genetics , Angiostatins/pharmacology , Animals , Bioreactors , Blotting, Western , Carcinoma, Lewis Lung/drug therapy , Carcinoma, Lewis Lung/pathology , Cell Count , Cell Growth Processes/drug effects , Chick Embryo , Chorioallantoic Membrane/blood supply , Fermentation , Humans , Male , Melanoma, Experimental/drug therapy , Melanoma, Experimental/pathology , Mice , Mice, Inbred C57BL , Neovascularization, Physiologic/drug effects , Pichia/enzymology , Pichia/metabolism , Promoter Regions, Genetic , Recombinant Proteins/biosynthesis , Recombinant Proteins/genetics , Recombinant Proteins/pharmacologyABSTRACT
Pichia pastoris is an efficient host for the expression and secretion of heterologous proteins and the most important feature of P. pastoris is the existence of a strong and tightly regulated promoter from the alcohol oxidase I (AOX1) gene. The AOX1 promoter (pAOX1) has been used to express foreign genes and to produce a variety of recombinant proteins in P. pastoris. However, some efforts have been made to develop new alternative promoters to pAOX1 to avoid the use of methanol. The glyceraldehyde-3-phosphate dehydrogenase promoter (pGAP) has been used for constitutive expression of many heterologous proteins. The pGAP-based expression system is more suitable for large-scale production because the hazard and cost associated with the storage and delivery of large volume of methanol are eliminated. Some important developments and features of this expression system will be summarized in this review.
Subject(s)
Genetic Engineering/methods , Glyceraldehyde-3-Phosphate Dehydrogenases/genetics , Pichia/genetics , Promoter Regions, Genetic/genetics , Animals , Cloning, Molecular , Gene Expression Regulation , Genetic Vectors/geneticsABSTRACT
Carbon source plays an important role in the constitutive expression of foreign proteins in Pichia pastoris. In present study, glucose , glycerol , methanol and oil acid, was used respectively as the only carbon source to constitutively express hAS in Pichia pastoris GS115 (pGAP9K-AS)in shaking flask. The result shows that oleic acid is the best (163 mg/L) compared with glycerol (83mg/L), glucose (76 mg/L)and methanol (57 mg/L). Since oleic acid is insoluble in water, glycerol was used as the carbon source in the high-density cell culture of GS115 (pGAP9K-AS) in a 30 liter bioreactor and 169 mg/L of angiostatin was obtained after 48h of culture. The expressed angiostatin is immunologically active as shown by Western blotting. The recombinant hAS inhibits bFGF induced CAM angiogenesis and suppresses the growth of B16 melanoma in C57BL/6J mice. The tumor inhibition rate is 90% after 12 days of treatment. Statistics analysis revealed that the tumor volume difference of mice between the hAS group and PBS group is prominent (P < 0.01).
