Demonstration of insulin-like growth factor (IGF-I and -II) receptors and binding protein in human breast cancer cell lines.
The insulin like growth factors (IGFs), potent mitogens for a variety of normal and transformed cells, have been reported to be secreted by several human breast cancer cell lines (BC). We have investigated the binding characteristics of IGF-I and -II in four human BC: MCF-7, T-47D, MDA 231 and Hs578T. Binding studies in microsomal membrane preparations detected high specific binding for both IGF in all four BC studied. Cross-linking with 125I-IGF-I, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under reduced conditions, revealed the presence of an alpha subunit of apparent Mr = 130,000 in MCF-7, T-47D and MDA 213 cells. When 125I-IGF-II was cross-linked, a major band of apparent Mr = 260,000 was seen in all BC. This band was inhibited by IGF-II, but not by insulin. Cross-linking of 125I-IGF-I to conditioned media from BC demonstrated the presence of three binding proteins of apparent Mr = 45,000, 36,000 and 29,000 in all BC but T-47D, in which the 36,000 band was not seen. These data demonstrate that BC possess classical receptors for both IGF-I and -II and, furthermore, that BC produce specific binding proteins for these growth factors.
D001943:Breast Neoplasms / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D005260:Female; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D011972:Receptor, Insulin / Q000302:isolation & purification / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D011972:Receptor, Insulin