DHFR-deficient CHO cell lines are a type of Chinese hamster ovary (CHO) cell line that have been engineered to lack functional dihydrofolate reductase (DHFR) enzyme. DHFR is an important enzyme in the folate metabolic pathway, which is involved in the synthesis of nucleotides and other important biomolecules.
CHO cells that are deficient in DHFR cannot synthesize thymidine and other essential nucleotides, and therefore require exogenous sources of these compounds in order to grow and proliferate. This property is exploited in the generation of stable cell lines for the production of recombinant proteins.
DHFR-deficient CHO cells are typically generated by introducing a DHFR-targeted gene knockout or mutation into the host CHO cell line. These cells can then be selected for their ability to grow in the presence of methotrexate, which is a potent inhibitor of DHFR activity. The cells that survive methotrexate selection are typically DHFR-deficient and are therefore dependent on exogenous sources of thymidine and other nucleotides for growth.
DHFR-deficient CHO cells are widely used in the biopharmaceutical industry for the production of recombinant proteins, particularly those that require high levels of gene amplification in order to achieve high levels of expression. By providing the cells with increasing concentrations of methotrexate, the number of copies of the recombinant gene can be increased, resulting in higher levels of protein expression.