Isolation and characterization of the murine lymphoma L5178Y cell line highly resistant to 5-fluorouracil.

5-Fluorouracil-resistant cell line designated as L5178Y/FU was established in this experiment. This is one of the colonies derived from the subculture which acquired resistance to 5-fluorouracil by passing the L5178Y cells through ten successive episodes of culture in Fischer's medium containing 5-fluorouracil, in which each 5-fluorouracil treatment was followed by recovery intervals. The resistance of this line is about 80-fold that of the IC99 of 5-fluorouracil, and also shows a cross resistance to both 5-fluorouridine and 5-fluoro-2'-deoxyuridine. 5-Fluoro-2'-deoxyuridine resistant subline designated as L5178Y/FUdR was also isolated from the subculture which acquired resistance to 5-fluoro-2'-deoxyuridine by using the same selection procedure. The resistance of this line is about 650-fold that of the IC99 of 5-fluoro-2'-deoxyuridine, and shows a partial cross-resistance to 5-fluorouridine, but not to 5-fluorouracil.