In Situ Hybridization (ISH) Combined with Immunohistochemistry (IHC) for Co-detection of EGFR RNA and Phosphorylated EGFR Protein in Lung Cancer Tissue.

Detection of phosphorylated proteins in tissue sections using immunohistochemistry (IHC) is a challenging task. The absence of tissue staining may be caused by either a lack of protein expression or a lack of protein activation via its phosphorylation. To address this problem, we employed Integrated Co-detection Workflow (ICW) protocol to analyze lung cancer tissue sections by combining in situ hybridization (ISH) with IHC. The target protein of interest was epidermal growth factor receptor (EGFR, also known as ErbB1 and HER1) which is the founding member of the ErbB family of receptor tyrosine kinases. Using phospho-specific antibodies specific for a phosphorylated site Y1173 of EGFR molecule allowed us to analyze IHC and ISH staining at a single cell level in lung cancer tissue. We have observed both a co-localization of IHC with ISH signals and ISH-positive cells lacking IHC labeling for phosphorylated EGFR. ICW appears to be a very powerful spatial biology technique for accurate localization of cancer cells with phosphorylated/activated and non-phosphorylated/nonactivated proteins.