NU7441 (KU-57788)

The effect of NU7441 on cellular survival following exposure to etoposide, doxorubicin, and ionizing radiation is measured in SW620, LoVo, V3, and V3-YAC cells by clonogenic assays. Briefly, growing cells in six-well plates or 6-cm dishes are exposed to etoposide or doxorubicin with or without NU7441 (0.5 or 1.0 μM) for 16 hours. For radiosensitization studies, NU7441 is added to the cells 1 hour before irradiation. V3 and V3-YAC cells are exposed to γ-irradiation (3.1 Gy/min ¹³⁷Cesium). SW620 and LoVo are exposed to X-irradiation (2.9 Gy/min at 230 kV, 10 mA) due to the equipment available. After irradiation, the cells are incubated with or without NU7441 for a further 16 hours. Cells are then harvested by trypsinization, counted, and seeded into 10-cm diameter Petri dishes at densities varying from 100 to 10⁵ per dish in drug-free medium for colony formation. Colonies are stained with crystal violet after 10 to 14 days and counted with an automated colony counter. The survival reduction factor (SRF) is calculated as the surviving fraction of cells in the absence of NU7441 divided by the surviving fraction of cells in the presence of NU7441 for any given dose or concentration of cytotoxic agent. The dose modification ratio (DMR90) is calculated as the concentration/dose of cytotoxic agent required to kill 90% of the cells in the absence of NU7441 divided by the concentration/dose of cytotoxic agent required to kill 90% of the cells in the presence of NU7441.