Heterologous protein expression by transimmortalized differentiated liver cell lines derived from transgenic mice (hepatomas/α1 antitrypsin/ONC mouse)

Abstract A number of therapeutic plasma proteins are synthesized by human hepatocytes. Since many of these proteins undergo liver-specific post-translational modifications which are required for full biological activity, it may therefore be necessary to develop hepatocyte-based expression systems for their production. Using transgenic mice we have developed a transimmortalisation technique for the isolation of differentiated hepatic cell lines, already engineered to secrete human α 1 antitrypsin ( α 1 AT), a plasma protein which is produced mainly in liver cells. This was achieved by co-expression of the mouse c- myc proto-oncogene and a genomic copy of the human α 1 AT gene, both under the control of the human α 1 AT promoter. Transgenic mice carrying this construct developed hepatomas producing human α 1 AT. Under defined culture conditions, cell lines secreting active α 1 AT were derived from these tumours. These cells maintain a differentiated hepatic phenotype and continue to secrete human α 1 AT for at least 40 generations.