Optical Imaging Enhanced IHC

Immunohistochemistry (IHC)-based biomarker analysis is a widely used method to detect activated and non-activated forms of protein in routinely-processed formalin-fixed tissue. In contrast to other biomarker technologies, IHC offers the additional advantage of providing information on relevant cellular localization since tissue morphology is retained.

However, IHC technology contains several disadvantages. First, the data collected is qualitative rather than quantitative and is reported in broad categories of 0, 1+, 2+, 3+ scores. This limits its utility where accurate measurements or high resolution of the data is required. Second, the qualitative nature of this technology provides a subjective result. Frequently, this can result in moderate to high inter-user and inter-laboratory variability. Despite these disadvantages, the technology’s capability to measure protein expression within the context of tissue morphology remains a powerful feature.

TMD has implemented optical imaging analysis to overcome the qualitative and subjective characteristics of this technology. In addition to providing conventional scores, TMD also captures the results in Optical Density (O.D.) units. This process involves digital capture of a stained tissue section to detect the amount and localization of the protein. Thus, the following data components become available through this process: number of cells stained, % of cells stained, and the amount of nuclear, cytoplasmic or membrane involvement for each biomarker. By analyzing these parameters, optical imaging-enhanced IHC can be used in several powerful ways for drug development.

TMD has used this technique to quantify the biomarker expression at different points of treatment in xenografts to create a dose response curve. Another application is to measure upregulation or downregulation of a specific biomarker under different treatment conditions. TMD has documented examples of these applications in: J Clin Onc (2005) 23(11):2502-12 and Br J Canc (2004) 91:1190-94.

Three xenografts from mice treated with different doses of a dual ErbB1/ErbB2 inhibitor were stained for Phospho-ErbB1: Untreated (left panel), 30 mg/kg (middle panel) and 100 mg/kg (right panel). Image analysis was performed and a quantitative Optical Density (OD) measurement for each slide was obtained. The graph shows the amount of Phospho-ErbB1 stain relative to the untreated control xenograft (set at 100%).

KEY BENEFITS

To learn more, review TMD’s Breakthrough Article on Optical Imaging Enhanced IHC.

To consult with TMD’s Translational Biomarker Specialists, call 866.897.7350 ex 213 or email TMD Translational Biomarker Services at biomarkers@tmdlab.com.