Brightfield multiplex immunohistochemistry with multispectral imaging.

Brightfield microscopy is the preferred method of pathologists for diagnosing solid tumors, utilizing common staining techniques such as hematoxylin and eosin staining and immunohistochemistry (IHC). However, as our understanding of the complex tumor microenvironment grows, there is increasing demand for multiplexed biomarker detection. Currently, multiplexed IHC assays are almost exclusively based on immunofluorescence because brightfield techniques are limited by the broad spectral absorption of chromogens and a reliance on conventional 3-channel color cameras. In this work, we overcome these limitations by combining new chromogens possessing narrow absorbance bands with matched illumination channels and monochrome imaging. Multiplex IHC was performed using four or five covalently deposited chromogens and hematoxylin nuclear stain to preserve morphological context and detail. Brightfield illumination was provided with a tungsten lamp/filter wheel combination or filtered light emitting diodes to provide up to 12 illumination wavelengths. In addition, an automated rapid imaging system was developed, using a synchronized 12-LED illuminator, that could capture images at all wavelengths in under 1 s. In one example, a four-biomarker multiplex assay was designed and used to distinguish regions of adenocarcinoma and squamous cell carcinoma in non-small cell lung cancer. The technology was also validated with a five-biomarker assay in prostate cancer. Spectrally unmixed images of each biomarker demonstrated concordant expression patterns with DAB single stain on serial sections, indicating faithful identification of each biomarker. In each assay, all chromogens were well resolved by spectral unmixing to remove spectral crosstalk. While further characterization and refinement of the assay, and improvements in automation and user interface are necessary for pathologist acceptance, this approach to multiplex IHC and multispectral imaging has the potential to accelerate adoption of multiplexing by combining the medical value of high-order multiplexing with the speed, pathologist familiarity, and broadly established clinical utility of brightfield microscopy.

Chromogenic immunohistochemical quadruplex provides accurate diagnostic differentiation of non-small cell lung cancer.

Lung cancer is the most common cancer worldwide and has the highest mortality rate. Carcinomas comprise 95% of all lung malignancies, the vast majority of which are non-small cell lung carcinomas (NSCLC). Increasingly, the diagnosis of lung cancer is established by examination of small tissue specimens obtained by minimally invasive techniques. It is critical to employ these tissues at maximum efficiency in order to render an accurate pathologic diagnosis and to perform theranostic studies, either genomic or by immunohistochemistry, to demonstrate genetic mutations that make patients eligible for molecularly targeted agents. Currently Thyroid Transcription Factor-1 (TTF-1) and Napsin A are the most commonly used immunohistochemical (IHC) stains to identify primary lung adenocarcinoma, and p40 and cytokeratin 5/6 (CK5/6) are used for squamous cell carcinoma. IHC stains for these markers, are performed either individually (IHC brown staining) or in combination as dual immunostains (i.e. TTF-1 + Napsin A and p40 + CK5/6, utilizing brown and red chromogens). Here we present a novel, truly multiplex immunohistochemical approach that combines staining with the above four antibodies on a single tissue section utilizing four different chromogens to accurately diagnose primary lung adenocarcinomas, squamous cell carcinomas, and combined adenosquamous carcinomas of the lung. Each marker is represented by a distinct color that can be read by a pathologist, using standard, bright field microscopy. We evaluated the ability of pathologists to differentiate NSCLCs using the multiplexed assay as compared to standard, single marker per slide diaminobenzidine (DAB)-based IHC. All cases in a cohort of 264 NSCLCs showed concordance of information (including positivity of stain, intensity of stain and coverage) between single IHC stains and the multiplex assay. This new multiplex IHC offers the capability to accurately diagnose and sub-classify primary lung NSCLCs, while conserving precious tissue for additional testing.

Covalently deposited dyes: a new chromogen paradigm that facilitates analysis of multiple biomarkers in situ.

Multiplexed analysis of multiple biomarkers in a tissue sample requires use of reporter dyes with specific spectral properties that enable discrimination of signals. Conventional chromogens with broad absorbance spectra, widely used in immunohistochemistry (IHC), offer limited utility for multiplexed detection. Many dyes with narrow absorbance spectra, eg rhodamines, fluoresceins, and cyanines, potentially useful for multiplexed detection are well-characterized; however, generation of a chromogenic reagent useful for IHC analysis has not been demonstrated. Studies reported herein demonstrate utility of tyramine-chemistry for synthesis of a wide variety of new chromogenic dye conjugates useful for multiplexed in situ analysis using conventional light microscopes. The dyes, useful individually or in blends to generate new colors, provide signal sensitivity and dynamic range similar to conventional DAB chromogen, while enabling analysis of co-localized biomarkers. It is anticipated that this new paradigm will enable generation of a wide variety of new chromogens, useful for both research and clinical biomarker analysis that will benefit clinicians and patients.