Fig. 1

Clonogenic survival of MO59K and MO59J tumor cell lines treated with PI-103 for 3 h prior to IR. Irradiated cells were either re-plated for the colony-forming test 24 h after IR (a, b, c) or were seeded at fixed cell densities, drug treated, irradiated, and 24 h after IR drug-containing medium was replaced with fresh medium (d, e). After 10–12 days, colonies containing at least 50 cells were scored as survivors. Data derived from at least three independent experiments for each cell line were pooled together (a) and fitted by a linear-quadratic equation (Eq. 1). The SD values are indicated by error bars. Parts b and c show the survival data at 3 and 5 Gy extracted from part a. Parts d and e showed the survival data at 3 and 5 Gy obtained without re-plating. “*” means P < 0.05