Method for mass production of factor vii/viia

A method for mass production of human coagulation factor VII, comprising:

• a) providing an animal cell line transfected with an expression vector, said expression vector carrying i) a dihydrofolate reductase promoter devoid of one or more CCGCC repeat sequences from the GC-rich region thereof and a dihydrofolate reductase gene operably linked thereto and ii) a cytomegalovirus promoter and a human coagulation factor VII gene operably linked thereto;
• b) culturing the transfected animal cell line of step a) in the presence of a dihydrofolate reductase inhibitor to select cells which express human coagulation factor VII;
• c) culturing the selected cells in a medium containing sodium butyrate to produce human coagulation factor VII;
• and
• d) harvesting the produced human coagulation factor VII.