A practical approach for evaluating new antibodies in the clinical immunohistochemistry laboratory

Predictive value of cyst/tumor volume ratio of pituitary adenoma for tumor cell proliferation

BACKGROUND

MRI has been widely used to predict the preoperative proliferative potential of pituitary adenoma (PA). However, the relationship between the cyst/tumor volume ratio (C/T ratio) and the proliferative potential of PA has not been reported. Herein, we determined the predictive value of the C/T ratio of PA for tumor cell proliferation.

METHODS

The clinical data of 72 patients with PA and cystic change on MRI were retrospectively analyzed. PA volume, cyst volume, and C/T ratio were calculated. The corresponding intraoperative specimens were collected. Immunohistochemistry and hematoxylin-eosin staining were performed to evaluate the Ki67 index and nuclear atypia. Patients were categorized according to the Ki67 index (< 3% and ≥ 3%) and nuclear atypia (absence and presence). Univariate and multivariate analyses were used to identify the significant predictors of the Ki67 index and nuclear atypia. The receiver operating characteristic curve assessed the prediction ability of the significant predictors.

RESULTS

Larger tumor volumes, smaller cyst volumes, and lower C/T ratios were found in patients with higher Ki67 indexes and those with nuclear atypia (P < 0.05). C/T ratio was an independent predictor of the Ki67 index (odds ratio = 0.010, 95% confidence interval = 0.000-0.462) and nuclear atypia (odds ratio = 0.010, 95% confidence interval = 0.000-0.250). The predictive value of the C/T ratio did not differ significantly from that of tumor volume (P > 0.05) but was better than that of cyst volume (P < 0.05). The area under the curve of the C/T ratio for predicting the Ki67 index and nuclear atypia was larger than that for predicting cyst volume and tumor volume.

CONCLUSIONS

C/T ratios can be used to predict PA tumor proliferation preoperatively. Our findings may facilitate the selection of surgery timing and the efficacy evaluation of surgery.

MRI features of pituitary adenoma apoplexy and their relationship with hypoxia, proliferation, and pathology

OBJECTIVE

We aim to study the MRI features of pituitary adenoma (PA) apoplexy and their relationship with hypoxia, proliferation, and pathology.

METHODS

Sixty-seven patients with MRI signs of PA apoplexy were selected. According to the MRI signs, they were divided into the parenchymal group and the cystic group. The parenchymal group had a low signal area on T2WI without cyst >2 mm and this area was not significantly enhanced on the corresponding TW1 enhancement. The cystic group had a cyst >2 mm on T2WI, and the cyst showed liquid stratification on T2WI or high signal on T1WI. The relative T1WI (rT1WI) enhancement value and relative T2WI (rT2WI) value of non-apoplexy areas were measured. Protein levels of hypoxia-inducible factor-1 (HIF-1α), pyruvate dehydrogenase kinase 1 (PDK1), and Ki67 were detected with immunohistochemistry and Western blot. Nuclear morphology was observed with HE staining.

RESULTS

The rT1WI enhancement average value, rT2WI average value, Ki67 protein expression level, and the number of abnormal nuclear morphology of non-apoplexy lesions in the parenchymal group were significantly lower than those in the cystic group. The protein expression levels of HIF-1α and PDK1 in the parenchymal group were significantly higher than those in the cystic group. HIF-1α protein was positively correlated with PDK1 but negatively correlated with Ki67.

CONCLUSION

When there is PA apoplexy, the ischemia and hypoxia of the cystic group are lesser than those of the parenchymal group, but the proliferation is stronger.

Effects of Automation on Sustainability of Immunohistochemistry Laboratory

The COVID-19 pandemic that hit the world recently caused numerous changes affecting the health system in every department. Reduced staff numbers, mostly due to illness, led to an increase in automation at every stage of laboratory work. The immunohistochemistry (IHC) laboratory conducts a high volume of slide staining every day. Therefore, we analyzed time and total costs required to obtain IHC slides in both the manual and automated way, comparing their efficiency by processing the same sample volume (48 microscope slides—the maximum capacity that an automated immunostainer—DAKO, Autostainer Link 48, Part No AS48030—can process over a single cycle). The total IHC procedure time to run 48 slides manually by one technician was 460 min, while the automated process finished a cycle within 390 min (15.22% less time). The final cost of a single manual IHC slide was 12.26 EUR and 7.69 EUR for slides labeled in the automated immunostainer, which reduced final costs by 37.27%. Thus, automation of the IHC procedure reduces the time and costs of the IHC process, contributing significantly to the sustainability of the healthcare system during the COVID-19 pandemic, overcoming insufficient human resources.

Clinical and research applications of multiplexed immunohistochemistry and in situ hybridization

Over the past decade, invention and adoption of novel multiplexing technologies for tissues have made increasing impacts in basic and translational research and, to a lesser degree, clinical medicine. Platforms capable of highly multiplexed immunohistochemistry or in situ RNA measurements promise evaluation of protein or RNA targets at levels of plex and sensitivity logs above traditional methods - all with preservation of spatial context. These methods promise objective biomarker quantification, markedly increased sensitivity, and single-cell resolution. Increasingly, development of novel technologies is enabling multi-omic interrogations with spatial correlation of RNA and protein expression profiles in the same sample. Such sophisticated methods will provide unprecedented insights into tissue biology, biomarker science, and, ultimately, patient health. However, this sophistication comes at significant cost, requiring extensive time, practical knowledge, and resources to implement. This review will describe the technical features, advantages, and limitations of currently available multiplexed immunohistochemistry and spatial transcriptomic platforms. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Immunofluorescence Staining of Paraffin Sections Step by Step

Immunofluorescence staining is the most frequently applied technique to detect and visualize various molecules in biological samples. Many protocols can be found in the literature and the websites of commercial antibody producers. This can result in a time-consuming and costly methodical work to establish “simple” antibody staining. We here summarize in a stepwise manner an easy-to-follow immunofluorescence staining protocol with an improved specific fluorescent signal and a reduced background and non-specific binding signal. This will help scientists to save time, effort, and antibody costs during the application of such a valuable technique.

Antibody validation for protein expression on tissue slides: a protocol for immunohistochemistry

Antibodies play a crucial role in basic research and clinical decision-making. However, there are no standardized algorithms or guidelines to ensure their accuracy and validity. There have been efforts to generate consensus, but, with the exception of clinical labs, antibody validation remains variable in the literature and sometimes in clinical practice. Here we focus on immunohistochemistry, an example of a scientific and clinical tool where validation of antibodies is critical. We describe a protocol that we use to validate antibodies specifically for immunohistochemistry, including some of the pillars of antibody validation from Uhlen et al. 2016, as an example of a rigorous approach to build antibody-based tests for both basic and translational science labs and for the clinic.

Performance evaluation of the polyclonal anti-rabies virus ribonucleoprotein IgG antibodies produced in-house for use in direct fluorescent antibody test

Fluorescein isothiocyanate (FITC) labelled anti-rabies virus ribonucleoprotein (RNP) antibodies can be used as immunoreagents in direct fluorescent antibody testing (dFAT) for rabies diagnoses. While in-house products are occasionally used by laboratories, most conjugates are commercial reagents. Commercial anti-RNP antibodies are only available for research purposes in Brazil, however, which contributes to the increasing use of in-house produced antibodies. Considering that conjugate quality may influence the results obtained during rabies diagnosis, we sought to analyze the performance requirements of in-house produced polyclonal anti-RNP IgG-FITC for application in dFAT. To that end, their reproducibility, diagnostic sensitivity, and specificity were evaluated. The titer of polyclonal anti-RNP IgG-FITC was initially determined and evaluated by dFAT, using central nervous system (CNS) samples of different animal species (dogs, cats, bovines, equines, bats, and non-human primates). As our main result, the polyclonal anti-RNP IgG-FITC reached a titer of 1:30/1:40 in dFAT, with 100% of diagnostic sensitivity and specificity. In terms of reproducibility, the antibodies, regardless the production batch, presented the same performances. In conclusion, the in-house produced polyclonal anti-RNP IgG-FITC proved suitable for rabies virus antigen detection by dFAT.

Prostate-specific markers to identify rare prostate cancer cells in liquid biopsies

Despite improvements in early detection and advances in treatment, patients with prostate cancer continue to die from their disease. Minimal residual disease after primary definitive treatment can lead to relapse and distant metastases, and increasing evidence suggests that circulating tumour cells (CTCs) and bone marrow-derived disseminated tumour cells (BM-DTCs) can offer clinically relevant biological insights into prostate cancer dissemination and metastasis. Using epithelial markers to accurately detect CTCs and BM-DTCs is associated with difficulties, and prostate-specific markers are needed for the detection of these cells using rare cell assays. Putative prostate-specific markers have been identified, and an optimized strategy for staining rare cancer cells from liquid biopsies using these markers is required. The ideal prostate-specific marker will be expressed on every CTC or BM-DTC throughout disease progression (giving high sensitivity) and will not be expressed on non-prostate-cancer cells in the sample (giving high specificity). Some markers might not be specific enough to the prostate to be used as individual markers of prostate cancer cells, whereas others could be truly prostate-specific and would make ideal markers for use in rare cell assays. The goal of future studies is to use sensitive and specific prostate markers to consistently and reliably identify rare cancer cells.

Proof of the quantitative potential of immunofluorescence by mass spectrometry

Protein expression in formalin-fixed, paraffin-embedded patient tissue is routinely measured by Immunohistochemistry (IHC). However, IHC has been shown to be subject to variability in sensitivity, specificity and reproducibility, and is generally, at best, considered semi-quantitative. Mass spectrometry (MS) is considered by many to be the criterion standard for protein measurement, offering high sensitivity, specificity, and objective molecular quantification. Here, we seek to show that quantitative immunofluorescence (QIF) with standardization can achieve quantitative results comparable to MS. Epidermal growth factor receptor (EGFR) was measured by quantitative immunofluorescence in 15 cell lines with a wide range of EGFR expression, using different primary antibody concentrations, including the optimal signal-to-noise concentration after quantitative titration. QIF target measurement was then compared to the absolute EGFR concentration measured by Liquid Tissue-selected reaction monitoring mass spectrometry. The best agreement between the two assays was found when the EGFR primary antibody was used at the optimal signal-to-noise concentration, revealing a strong linear regression (R²=0.88). This demonstrates that quantitative optimization of titration by calculation of signal-to-noise ratio allows QIF to be standardized to MS and can therefore be used to assess absolute protein concentration in a linear and reproducible manner.

Antibody Validation by Western Blotting

Validation of antibodies is an integral part of translational research, particularly for biomarker discovery. Assaying the specificity of the reagent (antibody) and confirming the identity of the protein biomarker is of critical importance prior to implementing any biomarker in clinical studies, and the lack of such quality control tests may result in unexpected and/or misleading results.Antibody validation is the procedure in which a single antibody is thoroughly assayed for sensitivity and specificity. Although a plethora of commercial antibodies exist, antibody specificity must be extensively demonstrated using diverse complex biological samples, rather than purified recombinant proteins, prior to use in clinical translational research. In the simplest iteration, antibody specificity is determined by the presence of a single band in a complex biological sample, at the expected molecular weight, on a Western blot.To date, numerous Western blotting procedures are available, based on either manual or automated systems and spanning the spectrum of single blots to multiplex blots. X-ray film is still employed in many research laboratories, but digital imaging has become a gold standard in immunoblotting. The basic principles of Western blotting are (a) separation of protein mixtures by gel electrophoresis, (b) transfer of the proteins to a blot, (c) probing the blot for a protein or proteins of interest, and (d) subsequent detection of the protein by chemiluminescent, fluorescent, or colorimetric methods. This chapter focuses on the chemiluminescent detection of proteins using a manual Western blotting system and a vacuum-enhanced detection system (SNAP i.d.™, Millipore).

Quality Management of the Immunohistochemistry Laboratory: A Practical Guide

Governmental regulations and most published guidelines do not provide specific guidance on implementation of quality management (QM) programs for immunohistochemistry (IHC) assays in Anatomic Pathology. QM of IHC consists of 3 main components: quality control, quality assurance, and quality improvement initiatives, each entailing distinctive but interrelated objectives. Discussion of the principles and some specific practices involved in these phases of QM of the IHC laboratory are therefore offered in this review, with an admitted emphasis on pragmatism.

The Application of Aptamers for Immunohistochemistry

Immunohistochemistry has helped to make surgical pathology the "gold" standard for tumor diagnosis. However, given the numerous problems associated with the use of antibodies for the staining of cellular markers in paraffin-embedded tissues, there is a requirement for novel agents that have the advantages of antibodies, but with few of the disadvantages. Aptamers, which are chemical antibodies, are highly specific and sensitive, like their protein counterparts, but display few of the disadvantages. These molecules represent a unique reagent that has the potential to revolutionize the field of histopathological diagnostics. In this study, we present a review of some of the aptamers that have been validated for use in diagnoses and suggest some of the advantages to using these molecules in the future.

Transplantation of autologous bone marrow-derived mesenchymal stem cells for traumatic brain injury

Results from the present study demonstrated that transplantation of autologous bone marrow-derived mesenchymal stem cells into the lesion site in rat brain significantly ameliorated brain tissue pathological changes and brain edema, attenuated glial cell proliferation, and increased brain-derived neurotrophic factor expression. In addition, the number of cells double-labeled for 5-bromodeoxyuridine/glial fibrillary acidic protein and cells expressing nestin increased. Finally, blood vessels were newly generated, and the rats exhibited improved motor and cognitive functions. These results suggested that transplantation of autologous bone marrow-derived mesenchymal stem cells promoted brain remodeling and improved neurological functions following traumatic brain injury.

Photocleavable DNA Barcoding Antibodies for Multiplexed Protein Analysis in Single Cells

We describe a DNA-barcoded antibody sensing technique for single cell protein analysis in which the barcodes are photocleaved and digitally detected without amplification steps (Ullal et al., Sci Transl Med 6:219, 2014). After photocleaving the unique ~70 mer DNA barcodes we use a fluorescent hybridization technology for detection, similar to what is commonly done for nucleic acid readouts. This protocol offers a simple method for multiplexed protein detection using 100+ antibodies and can be performed on clinical samples as well as single cells.

Evaluation of HER2 Protein Expression Using 2 New Monoclonal Antibodies

This study describes the performance of 2 new mouse anti-HER2 monoclonal antibodies (Abs), clones 33F and 410G, in evaluating HER2 overexpression in a series of 123 invasive breast carcinoma cases. In-house immunohistochemistry (IHC) was performed and the results were compared with those for the SP3 and A0485 anti-HER2 Abs. Chromogenic in situ hybridization was used to detect ERBB2 amplification and its concordance with IHC was analyzed. Comparison of IHC results for 33F with SP3 and A0485 yielded concordance rates (K) of 0.81 and 0.75, respectively; the same concordance rates were found when comparing results for 410G with SP3 and A0485. Compared with SP3 and A0485, 33F and 410G specificities were 98.6% and 98.6%, and 100% and 100%, respectively, whereas the sensitivities were 80% and 74.1%, and 78% and 72.2%, respectively. The K values between 33F and 410G HER2+ expression and chromogenic in situ hybridization-positive amplification were 1 and 0.96, respectively. These concordance rates were reproduced in another production batch (K=0.96 and K=0.96). Together, these results show that the tested monoclonal Abs would be well suited for detecting HER2 protein overexpression by IHC.

Cancer cell profiling by barcoding allows multiplexed protein analysis in fine-needle aspirates

Immunohistochemistry-based clinical diagnoses require invasive core biopsies and use a limited number of protein stains to identify and classify cancers. We introduce a technology that allows analysis of hundreds of proteins from minimally invasive fine-needle aspirates (FNAs), which contain much smaller numbers of cells than core biopsies. The method capitalizes on DNA-barcoded antibody sensing, where barcodes can be photocleaved and digitally detected without any amplification steps. After extensive benchmarking in cell lines, this method showed high reproducibility and achieved single-cell sensitivity. We used this approach to profile ~90 proteins in cells from FNAs and subsequently map patient heterogeneity at the protein level. Additionally, we demonstrate how the method could be used as a clinical tool to identify pathway responses to molecularly targeted drugs and to predict drug response in patient samples. This technique combines specificity with ease of use to offer a new tool for understanding human cancers and designing future clinical trials.

When tissue antigens and antibodies get along: revisiting the technical aspects of immunohistochemistry--the red, brown, and blue technique

Once focused mainly on the characterization of neoplasms, immunohistochemistry (IHC) today is used in the investigation of a broad range of disease processes with applications in diagnosis, prognostication, therapeutic decisions to tailor treatment to an individual patient, and investigations into the pathogenesis of disease. This review addresses the technical aspects of immunohistochemistry (and, to a lesser extent, immunocytochemistry) with attention to the antigen-antibody reaction, optimal fixation techniques, tissue processing considerations, antigen retrieval methods, detection systems, selection and use of an autostainer, standardization and validation of IHC tests, preparation of proper tissue and reagent controls, tissue microarrays and other high-throughput systems, quality assurance/quality control measures, interpretation of the IHC reaction, and reporting of results. It is now more important than ever, with these sophisticated applications, to standardize the entire IHC process from tissue collection through interpretation and reporting to minimize variability among laboratories and to facilitate quantification and interlaboratory comparison of IHC results.

Epo receptors are not detectable in primary human tumor tissue samples

Erythropoietin (Epo) is a cytokine that binds and activates an Epo receptor (EpoR) expressed on the surface of erythroid progenitor cells to promote erythropoiesis. While early studies suggested EpoR transcripts were expressed exclusively in the erythroid compartment, low-level EpoR transcripts were detected in nonhematopoietic tissues and tumor cell lines using sensitive RT-PCR methods. However due to the widespread use of nonspecific anti-EpoR antibodies there are conflicting data on EpoR protein expression. In tumor cell lines and normal human tissues examined with a specific and sensitive monoclonal antibody to human EpoR (A82), little/no EpoR protein was detected and it was not functional. In contrast, EpoR protein was reportedly detectable in a breast tumor cell line (MCF-7) and breast cancer tissues with an anti-EpoR polyclonal antibody (M-20), and functional responses to rHuEpo were reported with MCF-7 cells. In another study, a functional response was reported with the lung tumor cell line (NCI-H838) at physiological levels of rHuEpo. However, the specificity of M-20 is in question and the absence of appropriate negative controls raise questions about possible false-positive effects. Here we show that with A82, no EpoR protein was detectable in normal human and matching cancer tissues from breast, lung, colon, ovary and skin with little/no EpoR in MCF-7 and most other breast and lung tumor cell lines. We show further that M-20 provides false positive staining with tissues and it binds to a non-EpoR protein that migrates at the same size as EpoR with MCF-7 lysates. EpoR protein was detectable with NCI-H838 cells, but no rHuEpo-induced phosphorylation of AKT, STAT3, pS6RP or STAT5 was observed suggesting the EpoR was not functional. Taken together these results raise questions about the hypothesis that most tumors express high levels of functional EpoR protein.

Expanded clinical and experimental use of SOX11 - using a monoclonal antibody

BACKGROUND

The transcription factor SOX11 is of diagnostic and prognostic importance in mantle cell lymphoma (MCL) and epithelial ovarian cancer (EOC), respectively. Thus, there is an unmet clinical and experimental need for SOX11-targeting assays with low background, high specificity and robust performance in multiple applications, including immunohistochemistry (IHC-P) and flow cytometry, which until now has been lacking.

METHODS

We have developed SOX11-C1, a monoclonal mouse antibody targeting SOX11, and successfully evaluated its performance in western blots (WB), IHC-P, fluorescence microscopy and flow cytometry.

RESULTS

We confirm the importance of SOX11 as a diagnostic antigen in MCL as 100% of tissue micro array (TMA) cases show bright nuclear staining, using the SOX11-C1 antibody in IHC-P. We also show that previous reports of weak SOX11 immunostaining in a fraction of hairy cell leukemias (HCL) are not confirmed using SOX11-C1, which is consistent with the lack of transcription. Thus, high sensitivity and improved specificity are demonstrated using the monoclonal SOX11-C1 antibody. Furthermore, we show for the first time that flow cytometry can be used to separate SOX11 positive and negative cell lines and primary tumors. Of note, SOX11-C1 shows no nonspecific binding to primary B or T cells in blood and thus, can be used for analysis of B and T cell lymphomas from complex clinical samples. Dilution experiments showed that low frequencies of malignant cells (~1%) are detectable above background using SOX11 as a discriminant antigen in flow cytometry.

CONCLUSIONS

The novel monoclonal SOX11-specific antibody offers high sensitivity and improved specificity in IHC-P based detection of MCL and its expanded use in flow cytometry analysis of blood and tissue samples may allow a convenient approach to early diagnosis and follow-up of MCL patients.

Antibody validation by Western blotting

Validation of antibodies is an integral part of translational research, particularly for biomarker discovery. Validation is essential to show the specificity of the reagent (antibody) and to confirm the identity of the protein biomarker, prior to implementing the biomarker in clinical studies.Antibody validation is the procedure in which a single antibody is thoroughly assayed for sensitivity and specificity. Although a plethora of commercial antibodies exist, antibody specificity must be thoroughly demonstrated using a complex biological sample, rather than a recombinant protein, prior to use in clinical translational research. In the simplest iteration, antibody specificity is determined by the presence of a single band in a complex biological sample, at the expected molecular weight, on a western blot.Numerous western blotting procedures are available, spanning the spectrum of single blots to multiplex blots, with images and quantitation generated by manual or automated systems. The basic principles of western blotting are (a) separation of protein mixtures by gel electrophoresis, (b) transfer of the proteins to a blot, (c) probing the blot for a protein or proteins of interest, and (d) subsequent detection of the protein by chemiluminescent, fluorescent, or colorimetric methods. This chapter focuses on the chemiluminescent detection of proteins using a manual western blotting system and a vacuum-enhanced detection system (SNAP i.d.™, Millipore).

Antibody validation by combining immunohistochemistry and protein extraction from formalin-fixed paraffin-embedded tissues

AIMS

  Personalized cancer treatment strategies depend on comprehensive and detailed characterization of individual human malignancies. Clinical pathology, particularly immunohistochemical evaluation of biomarkers in tissues, is considered to be the approved standard for diagnostic and therapeutic decisions, having a direct influence on patient management and therapy. Although antibody-based approaches are established and integrated successfully into both clinical and research applications, for personalized treatment regimens new demands have been placed on the quality, reproducibility and accuracy of antibody-based assays. To ensure the accuracy of specific antigen detection in immunohistochemistry, we introduce a novel approach for antibody validation.

METHODS AND RESULTS

  In a tandem approach we used the same archival tissue of interest for antibody validation by combining extraction of immunoreactive proteins from formalin-fixed, paraffin-embedded tissue with Western blot analysis and immunohistochemistry. This procedure allows for specification of the antigen detected and for localization of the protein in the tissue. Of the 32 antibodies tested used in research and routine diagnostics, 19 showed reliable specificity in both assays.

CONCLUSION

  This study emphasizes the advantage of combining suitable methods to ensure reproducibility and specific antigen detection. Based on our results, we propose a novel step-by-step strategy to validate antibody specificity and reduce variability of immunohistochemical results.

Selection and validation of antibodies for signal transduction immunohistochemistry

The in situ expression levels and subcellular localization of molecules involved in signal transduction using specific antibodies can be useful for prognosis and diagnosis of human diseases such as cancer. In addition, it has the potential to be helpful in monitoring biologic response to targeted therapies. The increasing availability of such antibodies makes these studies feasible. However, compared to typical immunohistochemical stains in which stabile molecules such as cytokeratins are targeted, additional -validation may be required for signal transduction immunohistochemistry.

The immunohistochemistry laboratory: looking at molecules and preparing for tomorrow

CONTEXT

Surgical and subspecialty pathologists rely heavily on the patient's clinical context, imaging studies, morphology, and on ancillary studies such as immunohistochemistry (IHC), cytogenetics, and molecular diagnostics in arriving at accurate, contemporary diagnoses. Lymphoma/leukemia classification has led the way in the number of antibodies used in IHC algorithmic diagnostic approaches to distinguish more than 40 diseases. As the era of genomics, transcriptomics, proteomics, and targeted pathway therapeutics unfolds-and as infusion of federal funds to programs such as Accelerating Clinical Trials of Novel Oncologic PathWays (ACTNOW) requires that correlative biomarker assays be performed in Clinical Laboratory Improvement Amendments of 1988 (CLIA)-certified IHC laboratories-we face changes and challenges for the future.

OBJECTIVE

To discuss the laboratory, pertinent daily diagnostic, prognostic, and therapeutic uses of IHC, and future directions and challenges.

DATA SOURCES

Recent literature review and ongoing current activities in our laboratory and institution.

CONCLUSIONS

Meticulous attention at the microscope by expert subspecialty pathologists using ancillary methods is important in making correct diagnoses. Awareness of the literature and interactions with our research colleagues, including clinical, basic, and translational scientists, continue to expand our insights into and understanding of complex diseases; this will ultimately provide prognostic information to assist in appropriate clinical management of our patients and development of new targeted or combination therapies. Multimodality correlations will continue, with morphology, imaging data, immunophenotyping, and genetics as well as steadily increasing integration of pathway signaling, genome, sequenome, transcriptome, and proteome data used in clinical settings.

Antibody validation

Antibodies are among the most frequently used tools in basic science research and in clinical assays, but there are no universally accepted guidelines or standardized methods for determining the validity of these reagents. Furthermore, for commercially available antibodies, it is clear that what is on the label does not necessarily correspond to what is in the tube. To validate an antibody, it must be shown to be specific, selective, and reproducible in the context for which it is to be used. In this review, we highlight the common pitfalls when working with antibodies, common practices for validating antibodies, and levels of commercial antibody validation for seven vendors. Finally, we share our algorithm for antibody validation for immunohistochemistry and quantitative immunofluorescence.

Analytic variability in immunohistochemistry biomarker studies

BACKGROUND

Despite the widespread use of immunohistochemistry (IHC), there are no standardization guidelines that control for antibody probe variability. Here we describe the effect of variable antibody reagents in the assessment of cancer-related biomarkers by IHC.

METHODS

Estrogen receptor (ER), epidermal growth factor receptor (EGFR) 1, and human epidermal growth factor receptor 3 (HER3) were evaluated by quantitative immunofluorescence. Correlations between ER clones 1D5, SP1, F10, and ER60c, and EGFR monoclonal 31G7, 2-18C9, H11, and 15F8, and polyclonal 2232 antibodies were assessed in 642 breast cancer patients. HER3 was measured by RTJ1, RTJ2, SGP1, M7297, RB-9211, and C-17 antibodies in 42 lung cancer patients. Survival analysis was done with the use of multiple cutoff points to reveal any prognostic classification.

RESULTS

All ER antibodies were tightly correlated (Pearson's r(2) = 0.94-0.96; P < 0.0001) and western blotting confirmed their specificity in MCF-7 and BT474 cells. All EGFR antibodies but 2232 yielded specific results in western blotting; however, only 31G7 and 2-18C9 were strongly associated (Pearson's r(2) = 0.61; P < 0.0001). HER3 staining was nonspecific and nonreproducible. High EGFR-expressing patients had a worse prognosis when EGFR was measured with H11 or 31G7 (log rank P = 0.015 and P = 0.06). There was no statistically significant correlation between survival and EGFR detected by 2-18C9, 15F8, or polyclonal 2232 antibodies.

CONCLUSIONS

Antibody validation is a critical analytic factor that regulates IHC readings in biomarker studies. Evaluation of IHC proficiency and quality control are key components toward IHC standardization.

IMPACT

This work highlights the importance of IHC standardization and could result in the improvement of clinically relevant IHC protocols.

Immunohistochemistry as an important tool in biomarkers detection and clinical practice

The immunohistochemistry technique is used in the search for cell or tissue antigens that range from amino acids and proteins to infectious agents and specific cellular populations. The technique comprises two phases: (1) slides preparation and stages involved for the reaction; (2) interpretation and quantification of the obtained expression. Immunohistochemistry is an important tool for scientific research and also a complementary technique for the elucidation of differential diagnoses which are not determinable by conventional analysis with hematoxylin and eosin. In the last couple of decades there has been an exponential increase in publications on immunohistochemistry and immunocytochemistry techniques. This review covers the immunohistochemistry technique; its history, applications, importance, limitations, difficulties, problems and some aspects related to results interpretation and quantification. Future developments on the immunohistochemistry technique and its expression quantification should not be disseminated in two languages—that of the pathologist and another of clinician or surgeon. The scientific, diagnostic and prognostic applications of this methodology must be explored in a bid to benefit of patient. In order to achieve this goal a collaboration and pooling of knowledge from both of these valuable medical areas is vital

Suggested Guidelines for Immunohistochemical Techniques in Veterinary Diagnostic Laboratories

This document is the consensus of the American Association of Veterinary Laboratory Diagnosticians (AAVLD) Subcommittee on Standardization of Immunohistochemistry on a set of guidelines for immunohistochemistry (IHC) testing in veterinary laboratories. Immunohistochemistry is a powerful ancillary methodology frequently used in many veterinary laboratories for both diagnostic and research purposes. However, neither standardization nor validation of IHC tests has been completely achieved in veterinary medicine. This document addresses both issues. Topics covered include antibody selection, fixation, antigen retrieval, antibody incubation, antibody dilutions, tissue and reagent controls, buffers, and detection systems. The validation of an IHC test is addressed for both infectious diseases and neoplastic processes. In addition, storage and handling of IHC reagents, interpretation, quality control and assurance, and troubleshooting are also discussed. Proper standardization and validation of IHC will improve the quality of diagnostics in veterinary laboratories.

Utility of formaldehyde cross-linking and mass spectrometry in the study of protein-protein interactions

For decades, formaldehyde has been routinely used to cross-link proteins in cells, tissue, and in some instances, even entire organisms. Due to its small size, formaldehyde can readily permeate cell walls and membranes, resulting in efficient cross-linking, i.e. the formation of covalent bonds between proteins, DNA, and other reactive molecules. Indeed, formaldehyde cross-linking is an instrumental component of many mainstream analytical/cell biology techniques including chromatin immunoprecipitation (ChIP) of protein-DNA complexes found in nuclei; immunohistological analysis of protein expression and localization within cells, tissues, and organs; and mass spectrometry (MS)-compatible silver-staining methodologies used to visualize low abundance proteins in polyacrylamide gels. However, despite its exquisite suitability for use in the analysis of protein environments within cells, formaldehyde has yet to be commonly employed in the directed analysis of protein-protein interactions and cellular networks. The general purpose of this article is to discuss recent advancements in the use of formaldehyde cross-linking in combination with MS-based methodologies. Key advantages and limitations to the use of formaldehyde over other cross-linkers and technologies currently used to study protein-protein interactions are highlighted, and formaldehyde-based experimental approaches that are proving very promising in their ability to accurately and efficiently identify novel protein-protein and multiprotein interaction complexes are presented.

In situ hybridization in the pathology laboratory: General principles, automation, and emerging research applications for tissue-based studies of gene expression

Diagnostic anatomic pathologists play an important role in the care of patients through their careful evaluation of morphological features in routinely prepared histological sections stained with Hematoxylin and Eosin. Morphological assessment of tissue sections, backed by over one hundred years of experience is powerful and allows for the accurate classification and diagnosis of the majority of disease states within pathologically altered tissues. However, the appearance of cells and their architectural arrangement within a morphologically complex tissue represents only a fraction of the information, which is contained within a histological section. These tissues also contain all of the cellular proteins and expressed genes, which help to ultimately determine the biological behavior of cells, as well as provide clues to the origins and pathogenesis of disease states. Technical and theoretical advances in our understanding of cellular biology have provided pathologists with powerful tools to probe beyond pure morphology into the abnormalities in both protein and gene expression that underlie human disease. These tools, which include immunohistochemistry and in situ hybridization, are playing an increasingly important role in diagnostic pathology, as well as in translational research. This review will focus on the emerging role of in situ hybridization within clinical and research laboratories, and will highlight a number of technical advances that have expanded the application of this technology.

Clinical significance of performing immunohistochemistry on cases with a previous diagnosis of cancer coming to a national comprehensive cancer center for treatment or second opinion

Immunohistochemistry (IHC) is an important adjunctive test in diagnostic surgical pathology. We studied the clinical significance and outcomes in performing IHC on cases with a previous diagnosis of cancer who are coming to the Fox Chase Cancer Center (FCCC), a National Cancer Institute designated National Comprehensive Cancer Center (NCCC), for treatment and/or second opinion. We reviewed all the outside surgical pathology slide review cases seen at the FCCC for 1998 and 1999 in which IHC was performed. Cases were divided into the following: confirmation of outside diagnoses without and with prior IHC performed by the outside institution (groups A and B, respectively) and cases with a significant change in diagnosis without and with prior IHC performed by the outside institution (groups C and D, respectively). During 1998 and 1999, 6678 slide review cases were reviewed at the FCCC with an overall significant change in diagnosis in 213 cases (3.2%). IHC was performed on 186 of 6678 (2.7%) slide review cases with confirmation of the outside diagnosis in 152 (81.7%) cases and a significant change in diagnosis in 34 (18.3%) cases. Patient follow-up was obtained in 32 of 34 (94.1%) cases with a significant change in diagnosis (groups C and D), which confirmed the correctness of our diagnosis in 26 of 27 cases (96%; in five cases follow-up was inconclusive). We repeated the identical antibodies performed by the outside institutions in group D (37 antibodies) and group B (133 antibodies) with different results in 48.6% and 13.5%, respectively (overall nonconcordance 21.2%). In group D additional antibody tests beyond that performed by the outside institution were needed in 88.8% of cases to make a change of diagnosis. In the setting of a NCCC, reperforming and/or performing IHC on cases with a previous diagnosis of cancer is not a duplication of effort or misuse of resources. Repeating and/or performing IHC in this setting is important in the care and management of patients with cancer.

Clinical laboratory assays for HER-2/neu amplification and overexpression: quality assurance, standardization, and proficiency testing

OBJECTIVE

To present and contrast the results of immunohistochemistry and fluorescence in situ hybridization (FISH) proficiency testing surveys for HER-2/neu, as conducted by the Cell Markers and Cytogenetics Committees of the College of American Pathologists.

DESIGN

During the past 2 years, unstained sections from invasive breast carcinomas have been used for both immunohistochemistry and interphase FISH proficiency surveys. In most instances, the same cases were used for both the Cell Markers and Cytogenetics surveys. Additional data regarding interpretative variability for immunohistochemistry surveys have also been captured.

RESULTS

The number of laboratories performing FISH for HER-2/neu testing doubled during the 2-year period. The results of FISH testing have been remarkably concordant for laboratories submitting results. In contrast, the results of immunohistochemistry testing continue to highlight substantial variability among laboratories evaluating the same cases. The data show that this variability is at least in part due to variability in interpretation among observers, as well as inherent differences between immunohistochemistry and FISH techniques.

CONCLUSIONS

College of American Pathologists proficiency survey programs provide useful information about clinical testing for HER-2/neu amplification/overexpression.

Issues and barriers to development of clinically useful tumor markers: a development pathway proposal

There are few tumor markers that are clinically useful in predicting therapeutic responses or patient outcomes despite nearly 20 years of advances in molecular biology. We discuss a variety of issues and barriers that have affected movement of clinical tests from research into clinical practice. Studies of new markers frequently lack clear hypotheses and are generally underpowered to reach statistically valid conclusions. Relevant clinical endpoints may not be possible to evaluate, often leading to suboptimal study designs. Major stumbling blocks exist because studies are rarely comparable. This makes it difficult to determine why results vary from study to study. It also prevents pooling of small datasets for analysis. We propose a tumor marker development pathway that we think will be more efficient and effective. The pathway depends on developing statistically valid study designs, focusing on assay refinement and standardization early in the process, including assay details in publications, and providing data in a format that allows comparison with other studies. The process described should be applicable to development of new technologies that include analysis and interpretation of large, complex datasets. The proposed marker development pathway will require thoughtful refinement and expansion, but it should begin a productive dialog.