Figure 4.

Four modes of vascular responses to PI3K inhibitors in tumors. Antiangiogenic responses to PI3K inhibitors are not homogenous; in fact, these agents can have opposite effects on vessel number and vessel function. Current data seem to indicate that vessel function, rather than number, determines the antitumor efficacy of PI3K inhibitors. Thus, reduced vessel function leads to a decrease in tumor growth, whereas enhanced blood flow and perfusion does not. The doses of the PI3K inhibitors used in preclinical models are shown for comparison.