Figure 1.

Effect of axitinib and SN-38, the active metabolite of irinotecan, on in vitro cell proliferation (A–C). The antiproliferative effects of the drugs were studied using continuous exposures (72 hours) on HMVEC-d (A), Capan-1 (B), and MIAPaCa-2 cell lines (C). Symbols and bars indicate mean values ± SE, respectively. *P < .05 versus vehicle-treated controls. IC₅₀ indicates the concentration of drug that reduced cell proliferation by 50%. Isobologram analyses of HMVEC-d (D), Capan-1 (E), and MIAPaCa-2 (F) cell proliferation inhibition by simultaneous combination of axitinib and SN-38. The IC₅₀ and IC₉₀ values of each drug are plotted on the axes; the solid line represents the addictive effect, whereas the point representing the concentrations of axitinib and SN-38 resulting in 50% or 90% proliferation inhibition of the combination is reported on the left of the connecting line, indicating synergism.