Fig. 5.

PARP and CHK inhibitors radiosensitize tumor cells. A, BT474 cells were infected with empty vector virus (CMV) or with viruses to express dominant negative caspase 9 (dn Casp9), BCL-XL, or c-FLIP-s. Twenty-four hours after infection, cells were treated with vehicle (DMSO) or with AZD7762 (50 nM)+AZD2281 (1 μM). Cells were irradiated (4 Gy) 30 min after drug treatment. Cells were fixed 24 h later, and viability was determined using TUNEL assay (±S.E.M., n = 3). B, BT474 cells were transfected with WT CHK-GFP, dominant-negative (DN) CHK1-GFP, or GFP control vector. Twelve hours after transfection, single cells were replated in sextuplicate. Twelve hours after plating, cells were treated with vehicle (VEH, DMSO), AZD2281 (1 μM), AZD7762 (50 nM), or AZD7762+AZD2281. Cells were irradiated or mock-exposed 30 min after initiation of drug treatment (2 Gy). Colonies were permitted to form over the following 10 to 14 days. #, p < 0.05 greater than corresponding value in GFP-transfected cells; *, p < 0.05 less than corresponding value in GFP-transfected cells. C, BT549 cells (5 × 10⁶) were injected into the fourth mammary fat pad. Tumors were permitted to form to ∼75 mm³. Initial volumes of the tumor groups were as follows: vehicle, 84 mm³; AZD7762, 73 mm³; AZD2281, 66 mm³; and AZD7762+AZD2281, 76 mm³. Animals were injected with vehicle, AZD7762 (12.5 mg/kg), AZD2281 (12.5 mg/kg), or AZD7762+AZD2281 for 5 days. Tumors were irradiated on day 2 and day 4 (4 Gy). Tumors were measured with a caliper to determine tumor volume as described under Materials and Methods. The mean ± S.E.M. tumor volume for all animals in each treatment condition was plotted (n = 8 animals/group, 2 separate studies). D, for animals carrying BT549 tumors in C after receiving the indicated drug treatment, animals were monitored daily and when tumor volumes were >1.5 cm³, animals were sacrificed and survival of animals is plotted as a percentage of animals alive on any given day. P+C, PARP and CHK.