Host cell protein knock-out cells for production of therapeutic proteins

A method for producing a composition comprising a Vitamin K-dependent protein of interest having a substantially lower amount of protein contaminant Protein S expressed endogenously by a Chinese Ovary Hamster (CHO) host cell in the absence of modification, said method comprising the steps of:

• a) producing said host cell expressing a Vitamin K-dependent protein of interest comprising the following steps in any order:
• 1) transfecting a cell with a polynucleotide construct encoding a Vitamin K-dependent protein of interest;
• and
• 2) modifying said cell to express a substantially lower amount of endogenous Protein S by any method selected from:
• i) disruption by gene knock-out of the gene encoding endogenous Protein S;
• ii) transfection with a siRNA polynucleotide construct targeting a mRNA encoding Protein S;
• iii) transfection with a transcription factor being a Zinc finger protein binding to a DNA element of the gene encoding endogenous Protein S;
• iv) random mutagenesis for disruption of the gene encoding endogenous Protein S;
• and
• b) growing said host cell in a growth medium and harvesting said growth medium comprising said Vitamin K-dependent protein of interest;
• wherein said Vitamin K-dependent protein of interest is selected from the group consisting of:
• Protein S, GAS-6, Factor II (Prothrombin), Factor X, Factor IX, Protein C, Factor VII, Protein Z, Transmembrane gamma-carboxyglutamic acid protein 1, Transmembrane gamma-carboxyglutamic acid protein 2, Transmembrane gamma carboxyglutamic acid protein 3, Transmembrane gamma-carboxyglutamic acid protein 4, Bone Gla protein, Matrix Gla protein, and Osteocalcin.