Patent ID: 7968341

Claim:
A method of expressing a gene of interest encoding one or more desired therapeutic polypeptide(s) or product(s) in a eukaryotic host cell comprising: a) introducing a first DNA comprising a first recombination sequence and a selectable marker gene under the control of a promoter into a eukaryotic cell population; b) culturing the transformed cell population and selecting therefrom a cell based on expression of said marker gene; c) introducing a second DNA comprising a second recombination sequence, and an expression cassette comprising a promoter operably linked to the gene of interest into the selected cell of step b); d) contacting the cell of step c) comprising the second DNA with a bacteriophage lambda integrase or a modified integrase, wherein the second DNA is integrated into the first DNA by sequence-specific recombination mediated by the bacteriophage lambda integrase or the modified integrase to produce the eukaryotic host cell; and e) cultivating the host cell in suspension under serum free conditions, wherein the gene of interest is expressed; and f) isolating said one or more desired therapeutic polypeptide(s) or product(s) from the cultivated host cell or cell culture medium thereof, wherein the recombination site/integrase combinations are selected from the following: the first recombination sequence is attB (SEQ ID NO:13), the second recombination sequence is an attB (SEQ ID NO: 13), and the integrase is Int-h or Int-h/218; the first recombination sequence is attB (SEQ ID NO:13), the second recombination sequence is an attL (SEQ ID NO: 15), and the integrase is Int-h/218; the first recombination sequence is attL (SEQ ID NO:15), the second recombination sequence is an attB (SEQ ID NO: 13), and the integrase is Int-h/218; the first recombination sequence is attP (SEQ ID NO:14), the second recombination sequence is an attP (SEQ ID NO: 14), and the integrase is Int, Int-h or Int-h/218; the first recombination sequence is attP (SEQ ID NO:14), the second recombination sequence is an attR (SEQ ID NO: 16), and the integrase is Int-h/218; and the first recombination sequence is attR (SEQ ID NO:16), the second recombination sequence is an attP (SEQ ID NO: 13), and the integrase is Int-h/218; and further, if either recombination sequence is attL or attR, then IHF must also be present in step d).