FIG. 1.

Outline of the functional genetic screen to create GC-resistant cells. The constructs MMTV-TK, MMTV-Puro, and MMTV-EGFP were transfected into HeLa cells, and the cells were cultivated in G418. Stable integration of the three plasmids was verified in the isolated clone parental1. For mutagenesis and drug selection, cells were subjected to three to five rounds of ICR191 or ENU treatment and selected in medium containing 10 μg of ganciclovir/ml and 1 μM dex. The tables show the characteristics of parental1 and the mutant cells. +, positive; −, negative.