Gefitinib: Difference between revisions

[[EGFR|Epidermal Growth Factor Receptors]] are overexpressed in many types of human [[Cancer|carcinomas]] including lung, pancreatic, and breast cancer. This overexpression leads to excessive activation of the anti-apoptotic [[Ras]] signalling cascade, resulting in uncontrolled [[DNA_Replication|DNA synthesis]] and cell proliferation. Studies have revealed that the <scene name='Gefitinib/Kinase/1'>EGFR tyrosine kinase domain</scene> is responsible for activating this Ras signaling cascade. Upon binding ligands like Epidermal Growth Factor, EGFR dimerizes and autophosphorylates several tyrosine residues at its C-terminal domain. It is these phosphorylated tyrosine residues which elicit downstream activation of other signaling proteins and subsequent signaling cascades.<ref>PMID:6090945</ref><ref>PMID:16729045</ref> Gefitinib inhibits the EGFR tyrosine kinase by <scene name='Gefitinib/Bound/1'>binding to the ATP-binding site</scene> located within the kinase domain. Residues Lys 745, Leu 788, Ala 743, Thr 790, Gln 791, Met 193, Pro 794, Gly 796, Asp 800, Ser 719, Glu 762, & Met 766 to tightly bind the inhibitor. Unable to bind ATP, EGFR is incapable of autophosphorylating its C-terminal tyrosines, and the uncontrolled cell-proliferation signal is terminated.<ref>PMID:15284455</ref>