Detection of Receptor Activation in FFPE Specimens Figure 2. VeraTag FFPE c-MET quantification and correlation with Western blot, ELISA and IHC in cell lines. A. Quantification of c-MET expression in FFPE preparations of H441, H226, H2170, MCF7, Ln18, U138, U118, Ln229, U87, and H661 FFPE cell lines using the VeraTag assay. Background signals generated using an isotype control IgG (shown in inset) were subtracted from the c-MET assay signals. B. Western blot analysis of c-MET expression in H441, H226, H2170, MCF7, Ln18, U138, U118, Ln229, and H661 cell lysates. b-actin levels in the blot serves as a loading control. C. ELISA measurements of c-MET expression in H441, H226, H2170, MCF7, Ln18, U138, U118, Ln229, and H661 cell lysates. ND: Not detectable. D. IHC detection of c-MET expression in FFPE preparations of H441, H226, MCF7, Ln18, U118, and H661 cell lines. doi:10.1371/journal.pone.0015932.g002 cancers [4]. Consequently, RTK’s are important therapeutic targets and a number of RTK-directed drugs have received regulatory approval for treatment of human cancers. c-MET is a disulfide-linked a/b heterodimeric cell surface tyrosine kinase receptor. Hepatocyte growth factor (HGF; also known as scatter factor) is the only known c-MET ligand [5]. Binding of HGF to c- MET triggers c-MET receptor activation via autophosphorylation of the cytoplasmic domain and recruitment of adaptor proteins PLoS ONE | www.plosone.org 3 January 2011 | Volume 6 | Issue 1 | e15932