Expression of the mouse serum albumin gene introduced into differentiated and dedifferentiated rat hepatoma cells.

A 23-kilobase-pair segment of DNA containing the entire mouse serum albumin gene as well as 2.2 kilobase pairs of 5' and 4.3 kilobase pairs of 3' flanking sequences has been introduced into pSV2dhfr, a plasmid in which expression of the mouse dihydrofolate reductase cDNA is under the control of simian virus 40 sequences. This vector, pSV2dhfr-alb, was used to transfect differentiated and variant dedifferentiated rat hepatoma cells. Nine independent clones of transfected differentiated cells secrete considerable amounts of mouse albumin, while the expression of the normal rat albumin is the same as in nontransfected cells. In contrast, only small amounts of mouse and rat albumin are produced by transfected dedifferentiated cells. The amounts of albumin mRNA present in the cells are consistent with the amounts of albumin produced. These results show that a transfected gene can be regulated in a fashion consistent with the overall differentiation profile of the cell.