Green fluorescent protein (GFP) is employed as a selection marker for gene transduction and to track tumor cells. Transduction of enhanced GFP (eGFP) into human neuroblastoma cell lines via a lentiviral vector significantly sensitized CHLA-20 (wild-type and functional TP53), and to a lesser extent CHLA-90 cells (multidrug-resistant, mutant, and nonfunctional TP53) to carboplatin, doxorubicin, etoposide, or melphalan, relative to cells transduced using the cell surface antigen CD80 as a selection marker. Total glutathione (GSH) was significantly up-regulated (1.8- to 2.8-fold) after eGFP (but not CD80) transduction in cell lines with, but not in those lacking, functional p53. Cytotoxicity of GSH depletion by buthionine sulfoximine in CHLA-20 (but not in CHLA-20-eGFP) was diminished by hypoxia (2% O(2)). Thus, oxidative stress produced by GFP selects for cells with up-regulated GSH in a p53-dependent manner, and also enhanced the cytotoxicity of anticancer drugs in neuroblastoma cell lines. Our data suggest caution when employing GFP-transduced cells to assess drug sensitivity and that using a cell surface antigen as a selection marker for gene transduction may perturb cells less than GFP.