Type 1 IGF receptor in human breast diseases

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• Insulin-like growth factors (IGFs) initiate action by binding to membrane receptors.
• IGF binding sites are crucial for understanding cellular responses in breast tissues.

Purpose of the Study:

• To characterize IGF binding sites in human breast cancer.
• To determine the role of IGF receptors in breast cancer cell proliferation.

Main Methods:

• Competitive binding assays using radiolabeled IGF1 and IGF2.
• Chemical cross-linking experiments to determine molecular weights of binding sites.
• Inhibition studies using a monoclonal antibody (alpha IR-3) against the IGF1 receptor.

Main Results:

• IGF1 and IGF2 bind to distinct receptors, identified as type 1 IGF receptor (IGF1-R) and type 2 IGF receptor.
• IGF1-R has an apparent molecular weight of 130,000.
• Type 2 IGF receptor has an apparent molecular weight of 260,000-270,000.
• The antibody alpha IR-3 blocks IGF1 binding and inhibits IGF1-stimulated cell growth.
• Alpha IR-3 also inhibits IGF2's mitogenic activity, suggesting partial mediation by IGF1-R.

Conclusions:

• IGF1 specific binding sites in breast cancer cells are the type 1 IGF receptors (IGF1-R).
• IGF1-R plays a significant role in mediating the growth-promoting effects of IGF1 and partially IGF2 in breast cancer cells.
• Most breast cancer cell lines express IGF1-R, highlighting its potential as a therapeutic target.