In situ Protein Detection for Companion Diagnostics

Abstract

The emergence of targeted therapies for cancer has created a need for the development of companion diagnostic tests. Assays developed in recent years are aimed at determining both the effectiveness and safety of specific drugs for a defined group of patients, thus, enabling the more efficient design of clinical trials and also supporting physicians when making treatment-related decisions. Immunohistochemistry (IHC) is a widely accepted method for protein expression analyses in human tissues. Immunohistochemical assays, used to localize and quantitate relative protein expression levels within a morphological context, are frequently used as companion diagnostics during clinical trials and also following drug approval. Herein, we describe established immunochemistry-based methods and their application in routine diagnostics. We also explore the possibility of using IHC to detect specific protein mutations in addition to DNA-based tests. Finally, we review alternative protein binders and proximity ligation assays and discuss their potential to facilitate the development of novel, targeted therapies against cancer.

Quantification of HER family dimers by proximity ligation assay and its clinical evaluation in non–small cell lung cancer patients treated with osimertinib

“…The proteins of interest are recognized by primary antibodies and subsequently by two PLA probes that are conjugated to specific oligonucleotides. If the proteins and bound oligonucleotides are separated by a distance of <40 nm, the oligonucleotides are ligated, subjected to rolling-circle amplification, and detected with fluorescent complementary oligonucleotides [24]. We previously showed that EGFR (Her1) homodimers could be visualized and quantitated in both NSCLC cell lines and tissue specimens by in situ PLA [25].…”

Drug-Diagnostics Co-Development in Oncology

“…Likewise, there seems to be cancer-related changes in the proteins that are not directly reflected in the changes in RNA and DNA. Gremel et al review the currently applied CDx tests based on IHC but points also toward the future with regard to mutation-specific antibodies, in situ proximity legation assays, and alternative protein binders such as aptamers ( 10 ).…”