Figure 1.

Effect of chronic radiation on cell proliferation and survival of neuroblastoma cells. (A) The ability of neuroblastoma cells to survive and form colonies were measured using a colony formation assay. Acute radiation resulted in reduced colonies compared with controls, whereas following chronic radiation, the cells regained the ability to form colonies. (B) Cell viability was measured at 24, 48, 72 and 96 h using an MTT assay. NB1691 and SK-N-BE (2) cells treated with chronic radiation demonstrated increased proliferation potential compared with acute radiation and controls (*P<0.0001; **P=0.004).