Technical pitfalls potentially affecting diagnoses in immunohistochemistry

Interstitial Foci Expression of Indoleamine 2,3-Dioxygenase 1: A Potential Biomarker for Kidney Transplant Rejection

(1) Background: Kidney transplantation is the best therapy for patients with end-stage renal disease, but the risk of rejection complicates it. Indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme involved in immune response modulation, has been suggested to play a role in transplant immunological injury. The aim of the study was to explore the expression of IDO1 in the interstitial foci of transplanted kidneys and its potential association with rejection episodes. (2) Methods: This retrospective study analysed kidney transplant biopsies from 121 patients, focusing on IDO1 expression in interstitial foci. Immunohistochemistry was used to detect IDO1, and patients were categorised based on IDO1 presence (IDO1-IF positive or negative). The incidence of rejection was compared between these groups. (3) Results: Patients with IDO1 expression in interstitial foci (IDO1-IF(+)) exhibited higher incidences of rejection 46/80 (57.5%) vs. 10/41 (24.34%) patients compared to IDO1-IF(-) patients, which was statistically significant with p = 0.0005. The analysis of antibody-mediated rejection showed that IDO1-IF(+) patients developed AMR at 12/80 (15%), while only 1 IDO1-IF(-) negative patient did (2,44%), with p = 0.035. T-cell-mediated rejection was also more common in IDO1-IF(+) patients 43/80 (53.75%) than in IDO1-IF(-) patients 7/41 (17.07%), with p = 0.0001. (4) Conclusions: IDO1 expression in interstitial foci of renal transplant biopsies is associated with a higher incidence of rejection, suggesting that IDO1 could serve as a potential biomarker for transplant rejection. These findings highlight the importance of IDO1 in immune regulation and its potential utility in improving the management of kidney transplant recipients.

IMmuneCite: an integrated workflow for analysis of immune enriched spatial proteomic data

Spatial proteomics enable detailed analysis of tissue at single cell resolution. However, creating reliable segmentation masks and assigning accurate cell phenotypes to discrete cellular phenotypes can be challenging. We introduce IMmuneCite, a computational framework for comprehensive image pre-processing and single-cell dataset creation, focused on defining complex immune landscapes when using spatial proteomics platforms. We demonstrate that IMmuneCite facilitates the identification of 32 discrete immune cell phenotypes using data from human liver samples while substantially reducing nonbiological cell clusters arising from co-localization of markers for different cell lineages. We established its versatility and ability to accommodate any antibody panel and different species by applying IMmuneCite to data from murine liver tissue. This approach enabled deep characterization of different functional states in each immune compartment, uncovering key features of the immune microenvironment in clinical liver transplantation and murine hepatocellular carcinoma. In conclusion, we demonstrated that IMmuneCite is a user-friendly, integrated computational platform that facilitates investigation of the immune microenvironment across species, while ensuring the creation of an immune focused, spatially resolved single-cell proteomic dataset to provide high fidelity, biologically relevant analyses.

An overview of the detection of bovine respiratory disease complex pathogens using immunohistochemistry: emerging trends and opportunities

The bovine respiratory disease complex (BRDC) is caused by a variety of pathogens, as well as contributing environmental and host-related risk factors. BRDC is the costliest disease for feedlot cattle globally. Immunohistochemistry (IHC) is a valuable tool for enhancing our understanding of BRDC given its specificity, sensitivity, cost-effectiveness, and capacity to provide information on antigen localization and immune response. Emerging trends in IHC include the use of multiplex IHC for the detection of coinfections, the use of digital imaging and automation, improved detection systems using enhanced fluorescent dyes, and the integration of IHC with spatial transcriptomics. Overall, identifying biomarkers for early detection, utilizing high-throughput IHC for large-scale studies, developing standardized protocols and reagents, and integrating IHC with other technologies are some of the opportunities to enhance the accuracy and applicability of IHC. We summarize here the various techniques and protocols used in IHC and highlight their current and potential role in BRDC research.

Immunohistochemical Staining Characteristics of Low-Grade Invasive Ductal Carcinoma Using the ADH5 Cocktail (CK5/14, P63, and CK7/18): A Potential Interpretative Pitfall

Background: In our practice, the antibody cocktail ADH5 (CK5/14, p63, and CK7/18) helps with diagnostic challenges, such as identifying microinvasion and foci of invasive carcinoma, differentiating atypical ductal hyperplasia from hyperplasia of the usual type, and distinguishing basal phenotypes in triple-negative carcinomas. However, the ADH5 cocktail does have pitfalls and caveats. Methods: We describe our experience with the ADH5 cocktail of antibodies in breast pathology. Institutional knowledge and a literature search form our data sources. Results: We analyzed 44 cases. Four out of a total of 44 cases (9.1%)-two tubular carcinomas and two low-grade invasive breast carcinomas of no special type (ductal) with tubular features-showed an expected pattern of staining for ADH5 with a loss of brown (P63, CK5/14) staining around invasive glands and diffuse red (CK7/18) expression. Forty out of 44 (90.9%) cases showed an unexpected staining pattern (mixture of cytoplasmic brown and red). All 44 cases (100%) showed negative myoepithelial staining around invasive foci when separately stained for P63 and SMMH (Smooth Muscle Myosin Heavy). Conclusions: The unexpected staining pattern of ADH5 in low-grade invasive ductal carcinomas can be challenging to interpret in these lesions with low-grade cytology. The occurrence can cause confusion among users who employ multiplex stains, and it is important for users to be aware of this potential pitfall.

Qualitative Histological Evaluation of Various Decalcifying Agents on Human Dental Tissue

OBJECTIVE

 Dental hard tissue is among the hardest tissue of humans because it contains high amounts of inorganic substances. This leads to difficulty in preparing histological sections for histopathological examination. Acid and chelating agents are generally used to decalcify teeth. We aimed to compare the histological quality of teeth decalcified with various calcifying agents including 5% nitric acid, 50% formic acid with 20% sodium citrate (Anna Morse solution), 10% formic acid, commercial solution, and 14.4% neutral EDTA.

MATERIALS AND METHODS

 Freshly extracted premolar teeth were fixed and submitted for decalcification using different agents. Histological examination was qualitatively evaluated for tissue integrity and staining quality.

RESULTS

 Dentin integrity of teeth decalcified with all decalcifying agents did not show any statistical differences except that with the formic acid, whereas cementum integrity decalcified with neutral EDTA showed a superior score compared with other agents. Tissue integrity and staining quality of dental pulp cells were the best decalcified with neutral EDTA or Anna Morse solution.

CONCLUSION

 Our findings demonstrated that EDTA and Anna Morse solution gave a similar efficiency in the preservation of tissue integrity while Anna Morse solution may be recommended as a decalcification agent in routine use due to the more satisfying decalcification time than EDTA.

Assessment of 2-Year Storage Conditions on Protein, RNA, and DNA in Unstained Human Tissue Sections, Including a Novel Multiplex Digital Gene Expression Profiling Method with Implications for Biobanking

Background: Formalin-fixed, paraffin-embedded (FFPE) tissues are a valuable resource for clinical and basic science research. Paraffin blocks and the resulting unstained sections (USS) are often stored for years before being used. Previous studies have evaluated the effects of time, temperature, humidity, and inert gases on preservation of USS; however, no study has examined all four variables together. Methods: In the current work, we prospectively and blindly assessed time points from 0 to 24 months, room versus refrigerated temperature, and presence of a desiccant and/or nitrogen atmosphere on a variety of benign and malignant tissues from North America and Africa. End points included immunohistochemistry (IHC), in situ hybridization (ISH), extracted RNA and DNA quantity and quality, and messenger RNA performance in a novel, multiplexed digital gene expression profiling assay of both housekeeping and tumor-specific genes. Results: We found that using current methods of antigen retrieval, staining, and extraction, the end points of IHC, ISH, RNA, and DNA were well preserved under the various conditions tested, with implications that pre-embedding factors contribute to variability in subsequent tissue integrity. We also document that spectrophotometric estimations of nucleic acid concentrations were in general estimated to be higher than with fluorimetric methods, which may be pertinent to end assay development. We further describe a new multiplex assay, the PlexSet digital gene expression assay, suitable for evaluating RNA quality in FFPE tissues. Conclusion: Altogether, these results may provide helpful guidance with regard to approaches for long-term storage conditions for USS.

The Role of Pathology-Based Methods in Qualitative and Quantitative Approaches to Cancer Immunotherapy

Simple Summary

Immunotherapy has become the filar of modern oncological treatment, and programmed death-ligand 1 expression is one of the primary immune markers assessed by pathologists. However, there are still some issues concerning the evaluation of the marker and limited information about the interaction between the tumour and associated immune cells. Recent studies have focused on cancer immunology to try to understand the complex tumour microenvironment, and multiplex imaging methods are more widely used for this purpose. The presented article aims to provide an overall review of a different multiplex in situ method using spectral imaging, supported by automated image-acquisition and software-assisted marker visualisation and interpretation. Multiplex imaging methods could improve the current understanding of complex tumour-microenvironment immunology and could probably help to better match patients to appropriate treatment regimens.

Abstract

Immune checkpoint inhibitors, including those concerning programmed cell death 1 (PD-1) and its ligand (PD-L1), have revolutionised the cancer therapy approach in the past decade. However, not all patients benefit from immunotherapy equally. The prediction of patient response to this type of therapy is mainly based on conventional immunohistochemistry, which is limited by intraobserver variability, semiquantitative assessment, or single-marker-per-slide evaluation. Multiplex imaging techniques and digital image analysis are powerful tools that could overcome some issues concerning tumour-microenvironment studies. This novel approach to biomarker assessment offers a better understanding of the complicated interactions between tumour cells and their environment. Multiplex labelling enables the detection of multiple markers simultaneously and the exploration of their spatial organisation. Evaluating a variety of immune cell phenotypes and differentiating their subpopulations is possible while preserving tissue histology in most cases. Multiplexing supported by digital pathology could allow pathologists to visualise and understand every cell in a single tissue slide and provide meaning in a complex tumour-microenvironment contexture. This review aims to provide an overview of the different multiplex imaging methods and their application in PD-L1 biomarker assessment. Moreover, we discuss digital imaging techniques, with a focus on slide scanners and software.

Evaluation of EDTA and nitric acid solutions for decalcification of joints in AG/WT, BALB/c, C57, DBA1/J mice, and in Wistar rats

Decalcification of mineralized samples for microscopic analysis involves competing factors including decalcification time, preservation of tissue integrity and cost. We investigated the utility of different decalcification solutions for studying joints in AG/WT, BALB/c, C57, DBA1/J mice and Wistar rats. The hind paws of the rodents were removed and fixed with 10% buffered formalin. Specimens were divided randomly into three groups for demineralization: 10% nitric acid, 12.5% EDTA at room temperature and 12.5% EDTA at 35 °C with shaking. Sections of joints were stained with hematoxylin and eosin (H & E). We evaluated decalcification time and expense, ease of cutting sections, preservation of nuclear basophilia and intranuclear detail, and intensity of eosin staining. The 10% nitric acid solution produced the most rapid decalcification for the mice, but not the rats. The 12.5% EDTA solution at 35 °C with shaking did not decrease decalcification time. Effects on microtomy were variable as were the effects on H & E staining. The EDTA solution provided the best basophilia and intranuclear detail for the mice. For rats, only 12.5% EDTA at 35 °C with shaking produced good preservation. Preservation of nuclear basophilia and intranuclear detail for rats was best with 10% nitric acid and EDTA 35 °C. For mice, 10% nitric acid failed to preserve nuclear basophilia and intranuclear detail. For intensity of eosin staining, EDTA at room temperature and EDTA 35 °C was best for both mice and rats. Sections also exhibited good H & E staining in most samples decalcified with 10% nitric acid. Although we found considerable variation among groups of animals, we found less variation among the different mouse strains than between mice and Wistar rats.

Comprehensive Comparison of 22C3 and SP263 PD-L1 Expression in Non-Small-Cell Lung Cancer Using Routine Clinical and Conditioned Archives

PD-L1 harmonization studies revealed a strong correlation between the 22C3 and SP263 assays in non-small-cell lung cancer (NSCLC). However, the assays’ characteristics have yet to be validated in a variety of clinical and analytical settings. The results of 431 NSCLC samples tested concurrently in routine clinical practice with the PD-L1 22C3 and SP263 assays were reviewed, and both assays were performed on 314 archives of surgically resected NSCLCs to assess PD-L1 expression in relation to variables such as FFPE block age and FFPE section storage condition. In routine clinical samples, 22C3 showed the highest concordance rate with 94.5% of SP263 tumor proportion score (TPS) ≥50% and 92.3% of SP263 TPS ≥1%, while SP263 showed a concordance rate with 79.6% of 22C3 TPS ≥50% and 89.9% of 22C3 TPS ≥1%. In the archival analysis, the high TPS of 22C3 and SP263 (versus TPS 1%) were significantly associated with a more recent block (<3 years versus ≥3 years) (p = 0.007 and p = 0.009, respectively). Only the TPS of 22C3 was reduced when FFPE sections were stored at room temperature compared to SP263. However, when stored at 4 °C, the storage duration had no effect on expression in either assay. For 22C3 TPS 1−49 percent and ≥50 percent (OR = 1.73, p = 0.006 and OR = 1.98, p = 0.002, respectively). There was a considerably larger chance of preserved 22C3 expression in recent room-temperature paraffin section storage, although SP263 demonstrated preserved expression in prolonged room-temperature section storage. Despite the good association between PD-L1 22C3 and SP263 in routine clinical samples, FFPE blocks older than 3 years and sections held at room temperature for more than 1 week may result in an underestimation of PD-L1 status, particularly for the 22C3 test. However, the SP263 assay was more sensitive under these conditions.

The Global Prevalence of Neospora caninum Infection in Sheep and Goats That Had an Abortion and Aborted Fetuses: A Systematic Review and Meta-Analysis

Neospora caninum (N. caninum) can be a potential factor causing a significant rate of miscarriages in small ruminants (sheep and goats) worldwide. Therefore, the present study aimed to determine the global status of N. caninum in sheep and goats that had an abortion and aborted fetuses. Five English databases (PubMed, ScienceDirect, Web of Science, Scopus, and ProQuest) were searched for relevant scientific articles published from their inception until November 4, 2021. Finally, 21 studies conducted on sheep (1,671 aborted fetuses and 935 abortive sheep) and 10 studies on goats (130 aborted fetuses and 80 abortive goats) were included for the final meta-analysis. A random-effects meta-analysis model was used to estimate the pooled prevalence with 95% confidence intervals (CIs). Moreover, sensitivity analysis, publication bias test, and quality assessment were performed in this study. The pooled prevalence of N. caninum in aborted fetuses of sheep and goats globally was estimated to be 15% (95% CI: 9-21%) and 7% (95% CI: 2-12%) using molecular methods. Besides, the seroprevalence of N. caninum was estimated to be 17% for aborted fetuses of sheep. The overall prevalence rate of N. caninum infection in sheep that had an abortion was 3%. The present results show a relatively high prevalence of N. caninum infection in sheep that had an abortion and aborted fetuses compared to goats. Therefore, further studies using different diagnostic techniques to more accurately estimate the rate of infection in sheep and goats may help provide adequate control measures and strategies to reduce the rate of abortion in sheep and goats and reduce economic damage to the livestock industry. This study was registered at the International Prospective Register of Systematic Reviews (PROSPERO; code: CRD42020216694).

Immunohistochemical diagnosis of human infectious diseases: a review

BACKGROUND

Immunohistochemistry (IHC) using monoclonal and polyclonal antibodies is a useful diagnostic method for detecting pathogen antigens in fixed tissues, complementing the direct diagnosis of infectious diseases by PCR and culture on fresh tissues. It was first implemented in a seminal publication by Albert Coons in 1941.

MAIN BODY

Of 14,198 publications retrieved from the PubMed, Google, Google Scholar and Science Direct databases up to December 2021, 230 were selected for a review of IHC techniques, protocols and results. The methodological evolutions of IHC and its application to the diagnosis of infectious diseases, more specifically lice-borne diseases, sexually transmitted diseases and skin infections, were critically examined. A total of 59 different pathogens have been detected once in 22 different tissues and organs; and yet non-cultured, fastidious and intracellular pathogens accounted for the vast majority of pathogens detected by IHC. Auto-IHC, incorporating patient serum as the primary antibody, applied to diseased heart valves surgically collected from blood culture-negative endocarditis patients, detected unidentified Gram-positive cocci and microorganisms which were subsequently identified as Coxiella burnetii, Bartonella quintana, Bartonella henselae and Tropheryma whipplei. The application of IHC to ancient tissues dated between the ends of the Ptolemaic period to over 70 years ago, have also contributed to paleomicrobiology diagnoses.

CONCLUSION

IHC plays an important role in diagnostic of infectious diseases in tissue samples. Paleo-auto-IHC derived from auto-IHC, is under development for detecting non-identified pathogens from ancient specimens.

Semi-automated background removal limits data loss and normalizes imaging mass cytometry data

Imaging mass cytometry (IMC) allows the detection of multiple antigens (approximately 40 markers) combined with spatial information, making it a unique tool for the evaluation of complex biological systems. Due to its widespread availability and retained tissue morphology, formalin‐fixed, paraffin‐embedded (FFPE) tissues are often a material of choice for IMC studies. However, antibody performance and signal to noise ratios can differ considerably between FFPE tissues as a consequence of variations in tissue processing, including fixation. In contrast to batch effects caused by differences in the immunodetection procedure, variations in tissue processing are difficult to control. We investigated the effect of immunodetection‐related signal intensity fluctuations on IMC analysis and phenotype identification, in a cohort of 12 colorectal cancer tissues. Furthermore, we explored different normalization strategies and propose a workflow to normalize IMC data by semi‐automated background removal, using publicly available tools. This workflow can be directly applied to previously acquired datasets and considerably improves the quality of IMC data, thereby supporting the analysis and comparison of multiple samples.

PD-1 and PD-L1 Expression in Osteosarcoma: Which Specimen to Evaluate?

There is a growing interest in immunotherapy in childhood cancers. Osteosarcoma is a compelling potential target as there are few targeted options available for this aggressive cancer. We provide a description of the landscape of programmed cell death-1 (PD-1), programmed cell death-ligand 1 (PD-L1) and relevant immune markers in serial samples from 15 osteosarcoma patients. PD-1 and PD-L1 expression was present in biopsy samples (47% and 53%, respectively), absent in resections, and present in metastases (40% and 47%). Both decalcified and nondecalcified specimens demonstrated expression of PD-1 and PD-L1. The results suggest that biopsy or metastatic specimens maybe most valuable in assessing expression of PD-1 and PD-L1.

Comparative aspects of laboratory testing for the detection of Toxoplasma gondii and its differentiation from Neospora caninum as the etiologic agent of ovine abortion

Histologic examination of aborted material is an essential component in the diagnosis of ovine toxoplasmosis. However, the detection of Toxoplasma gondii in histologic sections, and its differentiation from the closely related protozoan Neospora caninum, is challenging. We developed a chromogenic in situ hybridization (ISH) assay for the identification of T. gondii in paraffin-embedded tissue samples. We examined retrospectively the archived placental tissue of 200 sheep abortion submissions for the presence of T. gondii by immunohistochemistry (IHC), ISH, and real-time PCR (rtPCR). All placental samples that tested positive for T. gondii by rtPCR (9 of 200) were also positive by IHC, with inconclusive IHC staining in an additional 7 rtPCR-negative cases. Further testing for N. caninum of all 200 placentas by rtPCR revealed 7 Neospora-positive cases. T. gondii ISH was positive in 4 of 9 IHC-positive samples and 1 of the 7 N. caninum rtPCR-positive samples. Real-time PCR was used as the reference standard for specificity and sensitivity calculations regarding placenta samples. Specificity of ISH and IHC was 99% and 96-100%, respectively. The sensitivity of ISH (44%) was quite low compared to IHC (100%). The exclusive use of ISH for the detection of T. gondii, and thus for the diagnosis of ovine toxoplasmosis, was not acceptable. However, combined with rtPCR, both ISH and IHC can be useful detection methods to improve histologic evaluation by visualizing the parasite within tissue sections.

Differential expression of NKX 3.1 and HOXB 13 in bone metastases originating from prostatic carcinoma among the Egyptian males

BACKGROUND

The skeleton represents one of the most common sites to be affected by metastatic tumors. About 65 % of all bone metastases come from the breast cancer in females, and from the prostatic carcinoma in males. A probable diagnostic pitfall may be encountered during the process of decalcification of the bone metastases specimens. This study aimed to evaluate the diagnostic utility of NKX3.1 and HOXB13 and compare them with the traditionally used PSA for the detection of prostatic origin of bone metastases.

MATERIAL AND METHODS

We analyzed 41 tissue specimens of bone metastases originating from prostatic carcinoma. Immunohistochemical staining of NKX3.1, HOXB13 and PSA was done with evaluation of their differential expression.

RESULTS

NKX3.1, HOXB 13 and PSA were expressed in (41/41), (39/41) and (25/41) respectively of the analyzed cases. On comparing NKX3.1 and HOXB13 positive staining, there was a statistically significant difference (P = 0.000). In addition, the frequency of positive NKX3.1 expression in decalcified bone biopsies of metastatic prostatic adenocarcinoma is statistically higher than that of PSA immunostaining (P = 0.000). We found a statistically significant difference between HOXB13 and PSA positive immunostaining (P = 0.01).

CONCLUSION

This study demonstrates that NKX3.1 and HOXB13 are more sensitive markers than PSA for the detection of prostate carcinoma metastatic to the bone following the decalcification process. We recommend use of NKX3.1 and HOXB13, rather than PSA, in the diagnosis of bone metastases originating from prostate cancer.

Mapping and Identification of Native Proteins of Developing Teeth in Mouse Mandibles

Mass spectrometry imaging is a powerful tool of increasing utility due to its ability to spatially resolve molecular biomarkers directly from sectioned tissues. One hindrance to its universality is that no single protocol is sufficient for every tissue type, fixation, and pretreatment. Mineralized tissues are uniquely challenging as extensive decalcification protocols are necessary to achieve thin sections. In this study, we optimized a method to image tryptic peptides by matrix-assisted laser desorption ionization mass spectrometry of decalcified, formalin-fixed paraffin-embedded mouse hemimandibles. Using a combination of on-tissue MS/MS and hydrogel extraction LC-MS/MS, peptides from the enamel, dentin, periodontal ligament, alveolar bone, pulp, and other regions are identified and mapped. This breakthrough method provides a comprehensive approach to biomarker discovery in dental and craniofacial tissues which is highly relevant given that diseases originating from this region of the body are the most prevalent across all populations.

The Society for Immunotherapy of Cancer statement on best practices for multiplex immunohistochemistry (IHC) and immunofluorescence (IF) staining and validation

OBJECTIVES

The interaction between the immune system and tumor cells is an important feature for the prognosis and treatment of cancer. Multiplex immunohistochemistry (mIHC) and multiplex immunofluorescence (mIF) analyses are emerging technologies that can be used to help quantify immune cell subsets, their functional state, and their spatial arrangement within the tumor microenvironment.

METHODS

The Society for Immunotherapy of Cancer (SITC) convened a task force of pathologists and laboratory leaders from academic centers as well as experts from pharmaceutical and diagnostic companies to develop best practice guidelines for the optimization and validation of mIHC/mIF assays across platforms.

RESULTS

Representative outputs and the advantages and disadvantages of mIHC/mIF approaches, such as multiplexed chromogenic IHC, multiplexed immunohistochemical consecutive staining on single slide, mIF (including multispectral approaches), tissue-based mass spectrometry, and digital spatial profiling are discussed.

CONCLUSIONS

mIHC/mIF technologies are becoming standard tools for biomarker studies and are likely to enter routine clinical practice in the near future. Careful assay optimization and validation will help ensure outputs are robust and comparable across laboratories as well as potentially across mIHC/mIF platforms. Quantitative image analysis of mIHC/mIF output and data management considerations will be addressed in a complementary manuscript from this task force.

Elevated Microsatellite Alterations at Selected Tetranucleotides (EMAST) Is Not Attributed to MSH3 Loss in Stage I-III Colon cancer: An Automated, Digitalized Assessment by Immunohistochemistry of Whole Slides and Hot Spots

INTRODUCTION

EMAST is a poorly understood form of microsatellite instability (MSI) in colorectal cancer (CRC) for which loss of MSH3 has been proposed as the underlying mechanism, based on experimental studies. We aimed to evaluate whether MSH3 loss is associated with EMAST in CRC.

METHODS

A consecutive cohort of patients with stage I-III CRC. Digital image analysis using heatmap-derived hot spots investigated MSH3 expression by immunohistochemistry. Fragment analysis of multiplex PCR was used to assess MSI and EMAST, and results cross-examined with MSH3 protein expression.

RESULTS

Of 152 patients, EMAST was found in 50 (33%) and exclusively in the colon. Most EMAST-positive cancers had instability at all 5 markers, and EMAST overlapped with MSI-H in 42/50 cases (84%). The most frequently altered tetranucleotide markers were D8S321 (38.2% of tumors) and D20S82 (34.4%). Subjective evaluation of MSH3 expression by IHC in tumor found ≤10% negative tumor cells in all samples, most being ≤5% negative. Digital analysis improved the detection but showed a similar spread of MSH3 loss (range 0.1-15.7%, mean 2.2%). Hotspot MSH3 negativity ranged between 0.1 to 95.0%, (mean 8.6%) with significant correlation with the whole slide analysis (Spearman's rho=0.677 P<.001). Loss of MSH3 expression did not correlate with EMAST.

CONCLUSIONS

In a well-defined cohort of patients with CRC, loss of MSH3 was not associated with EMAST. Further investigation into the mechanisms leading to EMAST in CRC is needed.

Utility of FOS as diagnostic marker for osteoid osteoma and osteoblastoma

Osteoid osteoma and osteoblastoma are bone-forming tumors shown to harbor FOS (87%) and FOSB (3%) rearrangements. The aim was to evaluate the immunohistochemical expression of FOS and FOSB in these tumors in comparison to other bone tumors, to evaluate the influence of decalcification, and to correlate immunohistochemical findings with the underlying genetic alteration using fluorescence in situ hybridization (FISH). Immunohistochemistry using whole sections was performed on osteoid osteoma (n=23), osteoblastoma (n=22), osteoblastoma-like osteosarcoma (n=3), reactive (n=3), and proliferative (n=11) bone lesions. Immunoreactivity in giant cell tumor of bone (n=74), aneurysmal bone cyst (n=6), chondromyxoid fibroma (n=20), osteosarcoma (n=85), chondroblastoma (n=17), and clear cell chondrosarcoma (n=20) was assessed using tissue micro arrays. Strong nuclear expression of FOS in > 50% of the tumor cells was observed in all osteoid osteomas (22/22), in 57% of osteoblastomas (12/21) and in 3/197 control cases. FOS immunoreactivity disappeared after > 3 days decalcification. FOS rearrangements were present in 94% of osteoid osteomas and osteoblastomas, with a concordance of 86% between FISH and immunohistochemistry. Two osteoblastomas (5%) were positive for FOSB, as opposed to 8/177 control cases. Additional FISH revealed no FOSB rearrangements in these cases. To conclude, in short decalcified biopsies, FOS immunohistochemistry can be used to diagnose osteoid osteoma and osteoblastoma, as overexpression is seen in the majority, being rare in their mimics. FOS immunohistochemistry should not be used after long decalcification. Moreover, low level of focal expression found in other lesions and tissues might cause diagnostic problems, in which case FISH could be employed.

Impact of Specimen Characteristics on PD-L1 Testing in Non-Small Cell Lung Cancer: Validation of the IASLC PD-L1 Testing Recommendations

INTRODUCTION

Molecules targeting programmed cell death 1 or its ligand programmed death ligand 1 (PD-L1) revolutionized the treatment of patients with NSCLC. The only approved biomarker for predicting treatment response is the PD-L1 tumor proportion score (TPS) determined by immunohistochemistry. According to International Association for the Study of Lung Cancer recommendations, specimens that include fewer than 100 tumor cells or are older than 3 years should not be used for PD-L1 testing and the reliability of cell blocks has yet to be validated.

METHODS

This retrospective study included 1249 consecutive patients with NSCLC who were tested for PD-L1 (using the clone 22C3) between September 2016 and April 2017. The associations between the presence of suboptimal characteristics (specimens with <100 tumor cells, specimens older than 3 years, or cell blocks) and PD-L1 TPS were examined by using a multinomial logistic regression.

RESULTS

Specimens from 35.5% of the patients had at least one suboptimal characteristic. For patients with a PD-L1 TPS of higher than 50%, there was a significantly higher probability that they had a specimen with more than 100 tumor cells (OR = 1.97, p = 0.008) and a more recent block (within 30 days versus after >3 years) (OR = 2.46, p = 0.023). There was no statistical difference in PD-L1 TPS between cell blocks and tissue specimens (biopsy OR = 0.99 [p = 0.996] and surgery OR = 0.73 [p = 0.302]).

CONCLUSIONS

Our results suggest that specimens containing fewer than 100 tumor cells or older than 3 years may lead to an underestimation of PD-L1 status. Our findings also provide support for the use of cell blocks for PD-L1 testing, although further research is needed.

Receptor Conversion in Distant Breast Cancer Metastases: A Systematic Review and Meta-analysis

Background

In metastatic breast cancer, hormone and/or human epidermal growth factor receptor 2 (HER2)-targeted therapy decision-making is still largely based on tissue characteristics of the primary tumor. However, a change of estrogen receptor alpha (ERα), progesterone receptor (PR), and HER2 status in distant metastases has frequently been reported. The actual incidence of this phenomenon has been debated.

Methods

We performed a meta-analysis including 39 studies assessing receptor conversion from primary breast tumors to paired distant breast cancer metastases. We noted the direction of change (positive to negative or vice versa) and performed subgroup analyses for different thresholds for positivity, the type of test used to assess HER2 receptor status, and metastasis location-specific differences (two-sided tests).

Results

Overall, the incidence of receptor conversion varied largely between studies. For ERα, PR, and HER2, we found that random effects pooled positive to negative conversion percentages of 22.5% (95% confidence interval [CI] = 16.4% to 30.0%), 49.4% (95% CI = 40.5% to 58.2%), and 21.3% (95% CI = 14.3% to 30.5%), respectively. Negative to positive conversion percentages were 21.5% (95% CI = 18.1% to 25.5%), 15.9% (95% CI = 11.3% to 22.0%), and 9.5% (95% CI = 7.4% to 12.1%). Furthermore, ERα discordance was statistically significantly higher in the central nervous system and bone compared with liver metastases (20.8%, 95% CI = 15.0% to 28.0%, and 29.3%, 95% CI = 13.0% to 53.5%, vs 14.3%, 95% CI = 11.3% to 18.1, P = .008 and P < .001, respectively), and PR discordance was higher in bone (42.7%, 95% CI = 35.1% to 50.6%, P < .001) and liver metastases (47.0%, 95% CI = 41.0% to 53.0%, P < .001) compared with central nervous system metastases (23.3%, 95% CI = 16.0% to 32.6%).

Conclusions

Receptor conversion for ERα, PR, and HER2 occurs frequently in the course of disease progression in breast cancer. Large prospective studies assessing the impact of receptor conversion on treatment efficacy and survival are needed. Meanwhile, reassessing receptor status in metastases is strongly encouraged.

PIK3CA mutations early persistence in cell-free tumor DNA as a negative prognostic factor in metastatic breast cancer patients treated with hormonal therapy

PURPOSE

The identification of biomarkers of hormonal therapy (HT) failure would allow tailored monitoring in metastatic breast cancer (mBC) patients. PIK3CA gene mutation is one of the most frequent events in mBC and is associated with HT resistance. We evaluated the early prognostic value of cell-free DNA (cfDNA) PIK3CA detection in first-line HT-treated mBC patients.

METHODS

Between June 2012 and January 2014, 39 patients were prospectively included in a dedicated clinical trial (NCT01612871). Blood sampling was performed before (M0) and 4 weeks (M1), 3 months (M3) and 6 months (M6) after HT initiation, and at tumor progression. Patients were followed until progression or until the end of the study (2 years). Mutation detection was performed using droplet-based digital PCR (ddPCR). Progression-free survival (PFS) was used as primary endpoint.

RESULTS

Median age at inclusion was 63 years (range 40-86). Most patients (34/39) received an aromatase inhibitor and presented a non-measurable disease (71.8%). PIK3CA mutations were reported in 10 (27.8%) and 5 (14.3%) cases at M0 and M1, respectively. The persistence of a detectable circulating mutation at M1 was highly correlated with a worse progression-free survival (PFS), rate at 1 year: 40% versus 76.7%; p = 0.0053).

CONCLUSIONS

Four-week persistence of cfDNA PIK3CA mutation appears highly correlated with PFS.

TRIAL REGISTRATION

NCT01612871, registered on June 6th, 2012; https://clinicaltrials.gov/ct2/show/NCT01612871 .

Upregulation of Scavenger Receptor B1 Is Required for Steroidogenic and Nonsteroidogenic Cholesterol Metabolism in Prostate Cancer

Aberrant cholesterol metabolism is increasingly appreciated to be essential for prostate cancer initiation and progression. Transcript expression of the high-density lipoprotein-cholesterol receptor scavenger receptor B1 (SR-B1) is elevated in primary prostate cancer. Hypothesizing that SR-B1 expression may help facilitate malignant transformation, we document increased SR-B1 protein and transcript expression in prostate cancer relative to normal prostate epithelium that persists in lethal castration-resistant prostate cancer (CRPC) metastasis. As intratumoral steroid synthesis from the precursor cholesterol can drive androgen receptor (AR) pathway activity in CRPC, we screened androgenic benign and cancer cell lines for sensitivity to SR-B1 antagonism. Benign cells were insensitive to SR-B1 antagonism, and cancer line sensitivity inversely correlated with expression levels of full-length and splice variant AR. In androgen-responsive CRPC cell model C4-2, SR-B1 antagonism suppressed cholesterol uptake, de novo steroidogenesis, and AR activity. SR-B1 antagonism also suppressed growth and viability and induced endoplasmic reticulum stress and autophagy. The inability of exogenous steroids to reverse these effects indicates that AR pathway activation is insufficient to overcome cytotoxic stress caused by a decrease in the availability of cholesterol. Furthermore, SR-B1 antagonism decreased cholesterol uptake, growth, and viability of the AR-null CRPC cell model PC-3, and the small-molecule SR-B1 antagonist block lipid transport-1 decreased xenograft growth rate despite poor pharmacologic properties. Overall, our findings show that SR-B1 is upregulated in primary and castration-resistant disease and is essential for cholesterol uptake needed to drive both steroidogenic and nonsteroidogenic biogenic pathways, thus implicating SR-B1 as a novel and potentially actionable target in CRPC. SIGNIFICANCE: These findings highlight SR-B1 as a potential target in primary and castration-resistant prostate cancer that is essential for cholesterol uptake needed to drive steroidogenic and nonsteroidogenic biogenic pathways.

Nonspecific Binding in Immunoassays for Autoantibodies

Immunoassays are invaluable for detection and quantification of numerous analytes, including autoantibodies. However, human sera often yield high nonspecific binding in such assays, and this may result in false positive or sometimes false negative results. The causes of nonspecific binding are numerous and it correlates with inflammatory parameters. Since the results of autoantibody testing are used for diagnosis and treatment of autoimmune diseases, it is mandatory to be aware of all possible causes of nonspecific binding for each individual assay and to correct for it whenever possible. General guidelines for this are described in this chapter.

Tissue Morphology and Antigenicity in Mouse and Rat Tibia: Comparing 12 Different Decalcification Conditions

Conventional bone decalcification is a time-consuming process and is therefore unsuitable for clinical applications and time-limited research projects. Consequently, we compared the effect of four different decalcification solutions applied at three different temperatures, and assessed the rate of decalcification and the implications on tissue morphology and antigenicity of mouse and rat tibiae. Bones were decalcified with 10% ethylenediaminetetraacetic acid (EDTA), 10% formic acid, 5% hydrochloric acid, and 5% nitric acid at 4C, 25C, and 37C. Decalcification in both species was fastest in nitric acid at 37C and slowest in EDTA at 4C. Histological and immunohistochemical staining confirmed that the conventional protocols of EDTA at 4C and 25C remain the best option regarding the quality of tissue preservation. Whereas formic acid at 4C is a good alternative saving about 90% of the decalcification time, hydrochloric and nitric acids should be avoided particularly in case of rat tibia. By contrast, due to their smaller size, mouse tibiae had shorter decalcification times and tolerated higher temperatures and exposure to acids much better. In conclusion, this study demonstrated that depending on the specific research question and sample size, alternative decalcification methods could be used to decrease the time of decalcification while maintaining histological accuracy.

Peripheral and central autonomic nervous system: does the sympathetic or parasympathetic nervous system bear the brunt of the pathology during the course of sporadic PD?

It is a well-established fact that the sympathetic, parasympathetic and enteric nervous systems are affected at early stages in Parkinson's disease (PD). However, it is not yet clarified whether the earliest pathological events preferentially occur in any of these three divisions of the autonomic nervous system (ANS). Significant involvement of the peripheral autonomic nervous system of the heart and gastrointestinal tract has been documented in PD. Accumulating evidence suggests that the PD pathology spreads centripetally from the peripheral to central nervous system through autonomic nerve fibers, implicating the ANS as a major culprit in PD pathogenesis and a potential target for therapy. This study begins with a brief overview of the structures of the central and peripheral autonomic nervous system and then outlines the major clinicopathological manifestations of cardiovascular and gastrointestinal disturbances in PD.

A New Paradigm for Tissue Diagnostics: Tools and Techniques to Standardize Tissue Collection, Transport, and Fixation

Purpose of Review

Studying and developing preanalytical tools and technologies for the purpose of obtaining high-quality samples for histological assays is a growing field. Currently, there does not exist a standard practice for collecting, fixing, and monitoring these precious samples. There has been some advancement in standardizing collection for the highest profile tumor types, such as breast, where HER2 testing drives therapeutic decisions. This review examines the area of tissue collection, transport, and monitoring of formalin diffusion and details a prototype system that could be used to help standardize tissue collection efforts.

Recent Findings

We have surveyed recent primary literature sources and conducted several site visits to understand the most error-prone processes in histology laboratories. This effort identified errors that resulted from sample collection techniques and subsequent transport delays from the operating room (OR) to the histology laboratories. We have therefore devised a prototype sample collection and transport concept. The system consists of a custom data logger and cold transport box and takes advantage of a novel cold + warm (named 2 + 2) fixation method.

Summary

This review highlights the beneficial aspects of standardizing tissue collection, fixation, and monitoring. In addition, a prototype system is introduced that could help standardize these processes and is compatible with use directly in the OR and from remote sites.

Chemical Tools for Studying Lipid-Binding Class A G Protein-Coupled Receptors

Cannabinoid, free fatty acid, lysophosphatidic acid, sphingosine 1-phosphate, prostanoid, leukotriene, bile acid, and platelet-activating factor receptor families are class A G protein-coupled receptors with endogenous lipid ligands. Pharmacological tools are crucial for studying these receptors and addressing the many unanswered questions surrounding expression of these receptors in normal and diseased tissues. An inherent challenge for developing tools for these lipid receptors is balancing the often lipophilic requirements of the receptor-binding pharmacophore with favorable physicochemical properties to optimize highly specific binding. In this study, we review the radioligands, fluorescent ligands, covalent ligands, and antibodies that have been used to study these lipid-binding receptors. For each tool type, the characteristics and design rationale along with in vitro and in vivo applications are detailed.

Comparison of Different Decalcification Methods Using Rat Mandibles as a Model

Selection of decalcification agents is an essential consideration when processing mineralized tissues because the integrity and immunohistochemical characteristics of the tissues may be affected. Here, we report results obtained from the decalcification of rat mandibles using 10% ethylenediaminetetraacetic acid (EDTA) at room temperature (RT), 10% EDTA at 37C, 5% nitric acid, and 10% formic acid at RT. Decalcification endpoints were determined by microcomputed tomography. Morphological preservation and antigenicity were evaluated by hematoxylin and eosin staining and immunohistochemistry. Decalcification of the anterior and posterior portions of the mandible took 220 and 191 hr in 10% EDTA RT, 102 and 73 hr in 10% EDTA 37C, 13.5 and 4.3 hr in 5% nitric acid, and 140 and 36 hr in 10% formic acid, respectively. Decalcification in 10% EDTA at 37C was accelerated, but 10% EDTA at RT provided optimal results for immunohistochemistry and cellular and structural details. Decalcification using 5% nitric acid was accomplished in the shortest time and exhibited good cellular and architectural morphology, whereas 10% formic acid was suboptimal with respect to tissue and cellular morphology. Despite being the slowest method, EDTA at RT is still the recommended method for decalcifying mineralized tissues; however, if rapid decalcification is needed, 5% nitric acid is the best option, yielding acceptable tissue integrity and speed.

Optimized Protocol of Methanol Treatment for Immunofluorescent Staining in Fixed Brain Slices

We optimized methanol treatment in paraformaldehyde-fixed slices for immunofluorescent staining of ependymal basal bodies in brain ventricles. As 100% methanol induced severe deformations to the slices (including rolling and folding over), we tried to decrease methanol concentration. We found that 33.3% to 75% methanol could result in ideal immunostaining of basal bodies without inducing obvious deformations. Instead of treating slices at -20°C (without proper cryoprotection measurements) as suggested in previous studies, we carried out methanol treatment at room temperature. Our modified protocol can not only raise immunostaining efficiency in tissue slices, it may also prevent potential freezing damages to the samples.

BMTP-11 is active in preclinical models of human osteosarcoma and a candidate targeted drug for clinical translation

Osteosarcoma occurs predominantly in children and young adults. High-grade tumors require multidisciplinary treatment consisting of chemotherapy in the neoadjuvant and adjuvant settings, along with surgical intervention. Despite this approach, death from respiratory failure secondary to the development and progression of pulmonary metastases remains a significant problem. Here, we identify the IL-11 receptor α subunit (IL-11Rα) as a cell surface marker of tumor progression that correlates with poor prognosis in patients with osteosarcoma. We also show that both IL-11Rα and its ligand, IL-11, are specifically up-regulated in human metastatic osteosarcoma cell lines; engagement of this autocrine loop leads to tumor cell proliferation, invasion, and anchorage-independent growth in vitro. Consistently, IL-11Rα promotes lung colonization by human metastatic osteosarcoma cells in vivo in an orthotopic mouse model. Finally, we evaluate the IL-11Rα-targeted proapoptotic agent bone metastasis-targeting peptidomimetic (BMTP-11) in preclinical models of primary intratibial osteosarcomas, observing marked inhibition of both tumor growth and lung metastases. This effect was enhanced when BMTP-11 was combined with the chemotherapeutic drug gemcitabine. Our combined data support the development of approaches targeting IL-11Rα, and establish BMTP-11 as a leading drug candidate for clinical translation in patients with high-risk osteosarcoma.

Simultaneous Detection of EGFR and VEGF in Colorectal Cancer using Fluorescence-Raman Endoscopy

Fluorescence endomicroscopy provides quick access to molecular targets, while Raman spectroscopy allows the detection of multiple molecular targets. Using a simultaneous fluorescence-Raman endoscopic system (FRES), we herein demonstrate its potential in cancer diagnosis in an orthotopically induced colorectal cancer (CRC) xenograft model. In the model, epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) were targeted with antibody-conjugated fluorescence and surface-enhanced Raman scattering (F-SERS) dots. FRES demonstrated fast signal detection and multiplex targeting ability using fluorescence and Raman signals to detect the F-SERS dots. In addition, FRES showed a multiplex targeting ability even on a subcentimeter-sized CRC after spraying with a dose of 50 µg F-SERS dots. In conclusion, molecular characteristics of tumor cells (EGFR in cancer cell membranes) and tumor microenvironments (VEGF in the extracellular matrix) could be simultaneously investigated when performing a colonoscopy.

Influence of decalcification procedures on immunohistochemistry and molecular pathology in breast cancer

Distant breast cancer metastases are nowadays routinely biopsied to reassess receptor status and to isolate DNA for sequencing of druggable targets. Bone metastases are the most frequent subgroup. Decalcification procedures may negatively affect antigenicity and DNA quality. We therefore evaluated the effect of several decalcification procedures on receptor status and DNA/RNA quality. In 23 prospectively collected breast tumors, we compared ERα, PR and HER2 status by immunohistochemistry in (non-decalcified) tissue routinely processed for diagnostic purposes and in parallel tissue decalcified in Christensen's buffer with and without microwave, EDTA and Formical-4. Furthermore, HER2 fluorescence in situ hybridization and DNA/RNA quantity and quality were assessed. We found that the percentage of ERα-positive cells were on average lower in EDTA (P=0.049) and Formical-4 (P=0.047) treated cases, compared with controls, and PR expression showed decreased antigenicity after Christensen's buffer treatment (P=0.041). Overall, a good concordance (weighted kappa) was seen for ERα, PR and HER2 immunohistochemistry when comparing the non-decalcified control tissues with the decalcified tissues. For two patients (9%), there was a potential influence on therapeutic decision making with regard to hormonal therapy or HER2-targeted therapy. HER2 fluorescence in situ hybridization interpretation was seriously hampered by Christensen's buffer and Formical-4, and DNA/RNA quantity and quality were decreased after all four decalcification procedures. Validation on paired primary breast tumor specimens and EDTA-treated bone metastases showed that immunohistochemistry and fluorescence in situ hybridization were well assessable and DNA and RNA yield and quality were sufficient. With this, we conclude that common decalcification procedures have only a modest negative influence on hormone and HER2 receptor immunohistochemistry in breast cancer. However, they may seriously affect DNA/RNA-based diagnostic procedures. Overall, EDTA-based decalcification is therefore to be preferred as it best allows fluorescence in situ hybridization and DNA/RNA isolation.

Improved decision making for prioritizing tumor targeting antibodies in human xenografts: Utility of fluorescence imaging to verify tumor target expression, antibody binding and optimization of dosage and application schedule

Preclinical efficacy studies of antibodies targeting a tumor-associated antigen are only justified when the expression of the relevant antigen has been demonstrated. Conventionally, antigen expression level is examined by immunohistochemistry of formalin-fixed paraffin-embedded tumor tissue section. This method represents the diagnostic "gold standard" for tumor target evaluation, but is affected by a number of factors, such as epitope masking and insufficient antigen retrieval. As a consequence, variances and discrepancies in histological staining results can occur, which may influence decision-making and therapeutic outcome. To overcome these problems, we have used different fluorescence-labeled therapeutic antibodies targeting human epidermal growth factor receptor (HER) family members and insulin-like growth factor-1 receptor (IGF1R) in combination with fluorescence imaging modalities to determine tumor antigen expression, drug-target interaction, and biodistribution and tumor saturation kinetics in non-small cell lung cancer xenografts. For this, whole-body fluorescence intensities of labeled antibodies, applied as a single compound or antibody mixture, were measured in Calu-1 and Calu-3 tumor-bearing mice, then ex vivo multispectral tumor tissue analysis at microscopic resolution was performed. With the aid of this simple and fast imaging method, we were able to analyze the tumor cell receptor status of HER1-3 and IGF1R, monitor the antibody-target interaction and evaluate the receptor binding sites of anti-HER2-targeting antibodies. Based on this, the most suitable tumor model, best therapeutic antibody, and optimal treatment dosage and application schedule was selected. Predictions drawn from obtained imaging data were in excellent concordance with outcome of conducted preclinical efficacy studies. Our results clearly demonstrate the great potential of combined in vivo and ex vivo fluorescence imaging for the preclinical development and characterization of monoclonal antibodies.

Verification of the Cross Immunoreactivity of A60, a Mouse Monoclonal Antibody against Neuronal Nuclear Protein

A60, the mouse monoclonal antibody against the neuronal nuclear protein (NeuN), is the most widely used neuronal marker in neuroscience research and neuropathological assays. Previous studies identified fragments of A60-immunoprecipitated protein as Synapsin I (Syn I), suggesting the antibody will demonstrate cross immunoreactivity. However, the likelihood of cross reactivity has never been verified by immunohistochemical techniques. Using our established tissue processing and immunofluorescent staining protocols, we found that A60 consistently labeled mossy fiber terminals in hippocampal area CA3. These A60-positive mossy fiber terminals could also be labeled by Syn I antibody. After treating brain slices with saponin in order to better preserve various membrane and/or vesicular proteins for immunostaining, we observed that A60 could also label additional synapses in various brain areas. Therefore, we used A60 together with a rabbit monoclonal NeuN antibody to confirm the existence of this cross reactivity. We showed that the putative band positive for A60 and Syn I could not be detected by the rabbit anti-NeuN in Western blotting. As efficient as Millipore A60 to recognize neuronal nuclei, the rabbit NeuN antibody demonstrated no labeling of synaptic structures in immunofluorescent staining. The present study successfully verified the cross reactivity present in immunohistochemistry, cautioning that A60 may not be the ideal biomarker to verify neuronal identity due to its cross immunoreactivity. In contrast, the rabbit monoclonal NeuN antibody used in this study may be a better candidate to substitute for A60.

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.

Non–Small Cell Lung Cancer, PD-L1, and the Pathologist

Context

Although most primary cancers of the lung carry a heavy mutational load and will potentially present many “nonself” antigens to the immune system, there are a wide range of possible mechanisms for tumors to avoid so-called immune surveillance. One such mechanism is the adoption of immune checkpoints to inhibit the host immune response. Immune checkpoint inhibitors show great promise in the treatment of advanced non–small cell lung cancer.

Objective

—To discuss the possibility of biomarker selection of patients for these therapies. This is becoming a much debated issue, and the immunohistochemical detection of Programmed Death Ligand 1 (PD-L1), the ligand for the inhibitory Programmed Death receptor 1 (PD-1) checkpoint, is one possible biomarker. Data so far available show some conflicting results, but PD-L1 immunohistochemistry looks likely to be introduced into clinical use for selecting patients for treatment with anti–PD-1 or anti–PD-L1 therapies. Given that there are 4 such drugs rapidly approaching regulatory approval, each with its own independent PD-L1 immunohistochemistry biomarker test, both oncologists and pathologists face some significant challenges.

Data Sources

Peer-reviewed literature and meeting proceedings, especially during the last 12 months, were used.

Conclusions

—The biology of PD-1/PD-L1 is complex, the clinical data for these drugs show considerable variation, the selection performance of the PD-L1 biomarker test is not perfect, and the existence of 4 drug/test combinations adds significantly to the problems faced. This article addresses some of the background to this therapeutic problem and discusses some of the issues ahead.

A method for histopathological study of the multifocal nature of spinal cord lesions in murine experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a well-established mouse model for multiple sclerosis and is characterized by infiltration of mononuclear cells and demyelination within the central nervous system along with the clinical symptoms of paralysis. EAE is a multifocal and random disease, which sometimes makes histopathologic analysis of lesions difficult as it may not be possible to predict where lesions will occur, especially when evaluating cross sections of spinal cord. Consequently, lesions may be easily missed due to limited sampling in traditional approaches. To evaluate the entire length of the spinal cord while maintaining anatomic integrity, we have developed a method to section the cord within the decalcified spinal column, which allows for the study of the multifocal nature of this disease and also minimizes handling artifact. HE and Luxol fast blue staining of these spinal cord sections revealed a paucity of lesions in some areas, while others showed marked inflammation and demyelination. The percentage of spinal cord affected by EAE was evaluated at four separate areas of longitudinally sectioned cord and it varied greatly within each animal. Immunohistochemical staining of in situ spinal cords which had undergone decalcification was successful for key immuno-markers used in EAE research including CD3 for T cells, B220 for B cells and F4/80 for murine macrophages. This method will allow investigators to look at the entire spinal cord on a single slide and evaluate the spinal cord with and without classic EAE lesions.

Predictive factors of activity of anti-programmed death-1/programmed death ligand-1 drugs: immunohistochemistry analysis

Anti-programmed death-1 (anti-PD1)/programmed death ligand-1 (PD-L1) therapeutic antibodies targeting regulatory pathways in T cells have recently shown to promising clinical effectiveness in several solid tumors by enhancing antitumor immune response. Immune checkpoint therapy has propelled therapeutic efforts opening a new field in cancer treatment. However, durable clinical response has been educed only in a fraction of patients, underlining the need to predictively select those patients most likely to respond, e.g., by detecting predictive biomarkers. Immunohistochemistry (IHC) detection of PD-L1 in tumor cells has been used in various trials of anti-PD-1/PD-L1 agents to try to select those patients most likely to respond. However, since there are different techniques and scoring systems, results have not been conclusive. Thus efforts are needed to develop standardized IHC assays as well as to explore additional biomarkers to evaluate and predict immune responses elicited by anti-PD-1/PD-L1 therapies.

Development and Characterization of Monoclonal Antibodies Specific for Mouse and Human Fcγ Receptors

FcγRs are key regulators of the immune response, capable of binding to the Fc portion of IgG Abs and manipulating the behavior of numerous cell types. Through a variety of receptors, isoforms, and cellular expression patterns, they are able to fine-tune and direct appropriate responses. Furthermore, they are key determinants of mAb immunotherapy, with mAb isotype and FcγR interaction governing therapeutic efficacy. Critical to understanding the biology of this complex family of receptors are reagents that are robust and highly specific for each receptor. In this study, we describe the development and characterization of mAb panels specific for both mouse and human FcγR for use in flow cytometry, immunofluorescence, and immunocytochemistry. We highlight key differences in expression between the two species and also patterns of expression that will likely impact on immunotherapeutic efficacy and translation of therapeutic agents from mouse to clinic.

Disaccharides Protect Antigens from Drying-Induced Damage in Routinely Processed Tissue Sections

Drying of the tissue section, partial or total, during immunostaining negatively affects both the staining of tissue antigens and the ability to remove previously deposited antibody layers, particularly during sequential rounds of de-staining and re-staining for multiple antigens. The cause is a progressive loss of the protein-associated water up to the removal of the non-freezable water, a step which abolishes the immunoavailability of the epitope. In order to describe and prevent these adverse effects, we tested, among other substances, sugars, which are known to protect unicellular organisms from freezing and dehydration, and stabilize drugs and reagents in solid state form in medical devices. Disaccharides (lactose, sucrose) prevented the air drying-induced antigen masking and protected tissue-bound antigens and antibodies from air drying-induced damage. Complete removal of the bound antibody layers by chemical stripping was permitted if lactose was present during air drying. Lactose, sucrose and other disaccharides prevent air drying artifacts, allow homogeneous, consistent staining and the reuse of formalin-fixed, paraffin-embedded tissue sections for repeated immunostaining rounds by guaranteeing constant staining quality in suboptimal hydration conditions.

Biomarkers of Tumour Radiosensitivity and Predicting Benefit from Radiotherapy

Radiotherapy is an essential component of treatment for more than half of newly diagnosed cancer patients. The response to radiotherapy varies widely between individuals and although advances in technology have allowed the adaptation of radiotherapy fields to tumour anatomy, it is still not possible to tailor radiotherapy based on tumour biology. A biomarker of intrinsic radiosensitivity would be extremely valuable for individual dosing, aiding decision making between radical treatment options and avoiding toxicity of neoadjuvant or adjuvant radiotherapy in those unlikely to benefit. This systematic review summarises the current evidence for biomarkers under investigation as predictors of radiotherapy benefit. Only 10 biomarkers were identified as having been evaluated for their radiotherapy-specific predictive value in over 100 patients in a clinical setting, highlighting that despite a rich literature there were few high-quality studies for inclusion. The most extensively studied radiotherapy predictive biomarkers were the radiosensitivity index and MRE11; however, neither has been evaluated in a randomised controlled trial. Although these biomarkers show promise, there is not enough evidence to justify their use in routine practice. Further validation is needed before biomarkers can fulfil their potential and predict treatment outcomes for large numbers of patients.

Alpha-synuclein immunoreactivity patterns in the enteric nervous system

We aimed to compare immunoreactivity patterns of four different anti-α-syn antibodies in surgical specimens of the gastrointestinal tract of Parkinson disease and control cases. Surgical specimens from stomach, small and large bowel of 6 PD cases and 12 controls were studied. Primary antibodies: anti-α-syn clone KM51, anti-phosphorylated α-syn Ser129, anti-α-syn clone 15G7 and anti-nitrated α-syn505. We found different immunoreactivity patterns: (a) coarse, Lewy-body-like aggregates labelled by the 4 antibodies and detected in 4/6 PD cases and in 1/12 controls; (b) distinct punctate cytoplasmic staining of ganglion cells labelled by anti-phosphorylated-α-syn and detected in 3/6 PD cases and 3/12 controls; (c) fine diffuse, synaptic-type staining of neural structures labelled by anti-α-syn-15G7 and anti-nitrated-α-syn505 and detected in all subjects. We conclude that different specific and non-specific immunoreactivity patterns are detected in surgical specimens of gastrointestinal tract when using different anti-α-syn antibodies, as they recognize different epitopes and states of alpha-synuclein protein. Coarse aggregates in neural structures seem to be the most promising marker for the diagnosis of Lewy-body parkinsonism when evaluating abnormal α-syn in the gastrointestinal tract.