Saxena et al. and Ozbay et al. independently demonstrated the ObR:IGF-IR cross-talk in breast cancer cells: both IGF-I and leptin phosphorylate the reciprocal receptor, ObR and IGF-IR can be co-immunoprecipitated, and combined treatment increased proliferation, invasion, and migration of breast cancer cells (251, 252). Here, IGF1 is linked to breast cancer.