Practice Passage Test - 4 | Practice Passages for MCAT PDF Download

"Pharmaceutical drugs known as tyrosine-kinase inhibitors (TKIs) are utilized to hinder the activity of receptor tyrosine kinases (RTKs). RTKs are receptors found on the surface of cells, which get activated by various ligands like growth factors, cytokines, and hormones. Activation of RTKs often triggers a signal transduction process, in which the RTKs phosphorylate downstream proteins on tyrosine residues, affecting their activity or location. Extensive research on TKIs has demonstrated their effectiveness in combating cancer. One particular RTK, called HER-2, is a transmembrane receptor associated with poor prognosis in breast cancer cases. HER-2 consists of an extracellular ligand binding domain, a transmembrane domain, and an intracellular domain that initiates the signal transduction process within a cell. The downstream effectors of the HER-2 pathway include proteins involved in pathways that promote cell growth. Trastuzumab, also known as Herceptin, is a monoclonal antibody TKI that disrupts the HER-2 receptor and is employed in the treatment of specific breast cancers. This raises the question: What is the rationale behind the common use of TKIs in cancer treatments?"