Figure 4.

Bystander effect. To investigate the bystander effect in vitro, Escherichia coli purine nucleoside phosphorylase (ePNP)‐positive cells and parental cells were mixed in different proportions (0:100; 1:99; 2:98; 5:95; 10:90; 25:75; 50:50; and 100:0). Twenty‐four hours later, all cells were cultured in RPMI‐1640 media containing 6‐methoxypurine 2′‐deoxyriboside at different concentrations (0–5 µg/mL) for 3 days. The percentage of surviving cells was calculated to evaluate the survival ratios of 4T1 mammary carcinoma cells by 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide assay. Data are representative of at least three separate experiments. Survival ratios are expressed as percentages relative to the corresponding mixture of untreated control cells.