IL-6 induced the tyrosine phosphorylation of IGF-I receptor β in NOP2 but not in ILKM3. (A) Immunoprecipitation (IP) and Western blot (WB) analysis with the indicated antibodies showed tyrosine phosphorylation of IGF-I receptor β and IRS-1 in ILKM3 and NOP2 treated with or without IL-6 (2 ng/mL) or IGF-I (100 ng/mL) for 5 minutes. (B) A Jak2 inhibitor, AG490 (20 μM), had no effect on the IL-6–induced phosphorylation of IGF-I receptor β in NOP2. (C) IL-6 (2 ng/mL) activated Jak2 in NOP2, as shown by IP-Western analysis using a phospho-specific Jak2 antibody.