Figure 5: PARP1 inhibition with radiation is more effective than radiation alone in a SUM-190 xenograft model.

SUM-190 cells were subcutaneously injected into CB17-SCID mice, and treatment was started when tumors reached approximately 80 mm³ (A). Olaparib treatment began one day before the initiation of radiation treatment and ended on the same day as the last fraction of radiation. With this paradigm, the combination treatment leads to delayed growth of tumors (B) and an increased time to tumor doubling (C) and tumor tripling (D) (p < 0.0001 = ****). The treatment did not display significant toxicities, and animal weights were not significantly different between the treatment groups (E). Using the FTV method, there was a synergistic effect with olaparib and RT treatment to antagonize tumor growth (ratios >1 indicate synergism) (F). A two-way ANOVA was performed to compare tumor volume between experimental groups.