IGF-I receptors were phosphorylated by IL-6 in IL-6Rα–transfected U266. (A) Flow cytometry showed the elevated expression of IL-6Rα on IL-6Rα–U266. (B) IP-Western analysis showed the phosphorylation of IGF-I receptor β by IL-6 (2 ng/mL) in IL-6Rα–U266 but not in mock U266.