Taken together, the observations that SU5416 is relatively well tolerated (∼145 mg/m2 1–2 doses/weeks) in patients, significantly activates the AhR in vivo (Figure 3), and has significant anti-proliferative activity that requires AhR signaling (Figures 3, 4, 5) strongly supports the possibility of developing SU5416 as an AhR-based cancer therapeutic. This evidence concerns the gene AHR and cancer.