Amplification and expression of heterologous ornithine decarboxylase in Chinese hamster cells.

We have developed an amplifiable mammalian expression vector based on the enzyme ornithine decarboxylase (ODC). We show greater than 700-fold amplification of this vector in ODC-deficient Chinese hamster ovary cells. A passive coamplified marker, dihydrofolate reductase (dhfr), was amplified and overexpressed 1,000-fold. This ODC vector was a dominant marker in a variety of cell types and displayed at least 300-fold amplification in wild-type Chinese hamster ovary cells.