IRS1 and breast carcinoma: These disparities may be due to a number of factors, including selection of patients or the diverse approaches used to detect IGF-IR, including immunoblots of membrane fractions and/or whole tissues, ligand binding assays, etc. Immunohistochemical studies revealed high IGF-IR and IRS-1 levels in control breast tissues and in well-differentiated breast carcinoma, whereas very low levels were seen in poorly differentiated cancers [3].