Multiplex Immunostaining Method to Distinguish HSP Isoforms in Cancer Tissue Specimens

Heat shock proteins (HSPs) are often expressed in all nucleated cells, but their expression profiles differ. In particular, HSP90α and HSP90β have high sequence identity and have not been fully examined for their individual and compensatory functions as molecular chaperones, differences in client proteins, and extracellular distributions with exosomes. Immunohistochemical staining is a technique to visualize the presence and localization of target antigens using specific antibodies, of which the multiplex immunostaining method can reveal differences in protein expression in the same tumor tissue and the localization of proteins of interest within tumor tissue or single cells. The common multiplex immunostaining method uses multiple secondary antibodies of different reacting animal species to identify and detect different antigens, thus requiring different animals to be immunized with each primary antibody. Furthermore, the fluorescent-antibody method is the predominant multiplex staining method but has the critical disadvantage that permanent specimens cannot be prepared. Here, we outline a multiplex staining method for HSP90α and HSP90β based on the enzyme–antibody method that allows permanent specimens to be prepared without the restriction of immunized animal species.