Mini MCAT passage: Tyrosine-kinase inhibitors in cancer treatment

Tyrosine-kinase inhibitors (TKIs) are pharmaceutical drugs that inhibit the action of receptor tyrosine kinases (RTKs). RTKs are receptors on the cell surface that are activated by a variety of ligands such as growth factors, cytokines, and hormones. RTK activation often causes a signal transduction cascade, whereby the RTK phosphorylates downstream proteins on tyrosine residues which can affect their activity or localization. Research in TKIs have shown them to be especially effective in the fight against cancer.

HER-2 is a transmembrane RTK whose overexpression is associated with an adverse prognosis in breast cancer. HER-2 has an extracellular ligand binding domain, a transmembrane domain, and an intracellular domain that activates the signal transduction cascade within a cell. The downstream effectors of the HER-2 pathway including proteins involved in growth promoting pathways, including cell proliferation. Trastuzumab, also known as Herceptin, is a monoclonal antibody TKI that interferes with the HER-2 receptor and is used to treat certain breast cancers.