Cell lines and their use for the production plasminogen activators

DETAILED DESCRIPTION OF THE INVENTION Production of serum-independent human cell lines The present invention provides new human cell lines which grow in the absence of serum or of any exogenous macromolecular growth fctor, such as insulin, transferrin, epidermal growth factor etc.
The cells according to the invention are capable of adhering to the culture vessel even in the absence of serum or fibronectin.
The major advantages of the new cell lines are: (1) an enormous reduction in costs as serum, such as foetal calf serum, is very expensive, (2) the very cheap and simple purification of products produced by the new cell lines as there are no serum contaminants in the medium and the product can easily be purified from the serum-free medium, and (3) the possibility of producing proteins which, due to the presence of proteases in serum, cannot be obtained (or which can only be obtained in poor yields) from serum-dependent cell lines.
The process for the production of the new serum-independent human cell lines comprises the steps of: a.
removing serum containing medium from the culture of a serum-dependent human cell line and replacing it with serum-free medium, b.
feeding the adherent or not adherent cells with serum-free medium, and c.
allowing the cells to grow until a serum-independent cell line has been established.
The term "serum-free medium" as used hereinbefore and hereinafter is intended to designate a medium which is not only deprived of serum but also of any macromolecular growth factor.
Accordingly, a cell line which grows in the absence of both serum and exogenous macromolecular growth factors is referred to as a "serum-independent cell line".
The serum-dependent human cell line used as a "starting material" in the above process is especially a continuous one and may originate from human neoplasms, such as melanoma, malignant teratoma, sarcoma, glioblastoma, meningioma, neuroblastoma, lipoma, adenoma, carcinoma of breast or carcinoma of the bladder.
Preferred cell lines are those which produce TPA and/or pro-TPA