Further characterization of storage-related alterations in immunoreactivity of archival tissue sections and its implications for collaborative multicenter immunohistochemical studies

Quality Assessment of Proteins and RNA Following Storage in Archival Formalin-Fixed Paraffin-Embedded Human Breast Cancer Tissue Microarray Sections

Although the immunogenicity of formalin-fixed paraffin-embedded tissue sections can decrease during storage and transport, the exact mechanism of antigenic loss and how to prevent it are not clear. Herein, we investigated changes in the expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2), E-cadherin, and Ki-67 in human breast tissue microarray (TMA) tissue sections stored for up to 3 months in dry and wet conditions. The positive rates of ER and PR expression were minimally changed after 3 months of storage, but the Allred scores of ER and PR stored in humid conditions decreased remarkably in comparison to fresh-cut tissue. The HER-2 antigenicity and RNA integrity of breast TMA sections stored in dry conditions diminished gradually with storage time, whereas the immunoreactivity and RNA quality of HER-2 in humid conditions decreased sharply as storage length increased. The area and intensity of E-cadherin staining in tissue sections stored in dry conditions did not change significantly and were minimally changed after 3 months, respectively. In contrast, the area and intensity of E-cadherin staining in tissue sections stored in humid conditions decreased significantly as storage length increased. Finally, the Ki-67 labeling index of tissue sections stored for 3 months in dry (9% decrease) and wet (31.9% decrease) conditions was decreased in comparison to fresh sections. In conclusion, these results indicate that water is a crucial factor for protein and RNA degradation in stored tissue sections, and detailed guidelines are required in the clinic.

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.

Podocalyxin inhibits human embryo implantation in vitro and luminal podocalyxin in putative receptive endometrium is associated with implantation failure in fertility treatment

OBJECTIVE

To study whether endometrial epithelial podocalyxin (PCX) inhibits implantation of human embryos in vitro and in patients undergoing in vitro fertilization (IVF).

DESIGN

We have recently identified PCX as a key negative regulator of endometrial epithelial receptivity. Podocalyxin is expressed in all epithelial cells in the nonreceptive endometrium, but is selectively downregulated in the luminal epithelium (LE) for receptivity. In the current study, we first investigated whether high levels of PCX in Ishikawa monolayer inhibit attachment and/or penetration of human blastocysts in in vitro models. We then examined PCX by immunohistochemistry in putative receptive endometrial tissues biopsied from 81 IVF patients who underwent frozen embryo transfer in the next natural cycle and retrospectively analyzed the association between PCX staining in LE and clinical pregnancy as a proxy of successful implantation.

SETTING

RMIT University, Australia; Vrije Universiteit Brussel, Belgium.

PATIENT(S)

In vitro fertilization patients undergoing frozen/thawed embryo transfer.

INTERVENTION(S)

N/A.

MAIN OUTCOME MEASURE(S)

Endometrial epithelial PCX inhibits implantation of human embryos in vitro and in IVF patients.

RESULT(S)

High levels of PCX in Ishikawa monolayer significantly inhibited blastocyst attachment and penetration. Among the 81 putative receptive tissues, 73% were negative, but 27% were heterogeneously positive for PCX in LE. The clinical pregnancy rate was 53% in those with a PCX-negative LE but only 18% in those with a PCX-positive LE. If LE was positive for PCX, the odds ratio of no clinical pregnancy was 4.95 (95% Confidence interval, 1.48-14.63).

CONCLUSION(S)

Podocalyxin inhibits embryo implantation. Assessment of PCX may aid the evaluation and optimization of endometrial receptivity in fertility treatment.

Factors affecting immunoreactivity in long-term storage of formalin-fixed paraffin-embedded tissue sections

Antigen decay in archival formalin-fixed paraffin-embedded (FFPE) tissue sections for immunohistochemistry is a well-known phenomenon which may have repercussions on translational and research studies and length of storage time appears fundamental. The aim of this study was to evaluate all possible factors which may lead to antigen decay on a prospective standardized collection of human tissues with a panel of 14 routinely used antibodies. Serial slide sections from FFPE control tissues were stored using different methods (routine storage at room temperature, Parafilm(®) protected, paraffin coated and cold stored at 4 °C) and for different time periods: 1, 6, 9, 12, 24 and 36 months. Immunohistochemistry was performed at each time cutoff simultaneously on stored sections and on freshly cut sections using a panel of 14 antibodies. Immunoreactivity was compared with immunoreactions performed at time zero. Reduction in immunostaining was observed for a subset of antibodies (CD3, CD 31, CD117, estrogen and progesterone receptors, Ki67, p53, TTF-1, vimentin) while for others (smooth muscle actin, keratins 7, 20, AE1/AE3, 34βE12), no antigen decay was observed. Loss of antigenicity was proportional to tissue section age and was dependent on mode of storage with cold storage slides being the least affected. All antigens with reductions in immunosignal were nuclear or membranous, and they all required heat pre-treatment for antigen retrieval. In contrast to results from other studies, when pre-analytical factors are strictly controlled and standardized, antigen decay seems to be restricted to nuclear or membrane antigens which require heat antigen retrieval.

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.

Immunohistochemical evaluation of the effects of paraffin section storage on biomarker stability

Environmental stresses can alter immunoreactivity of biomarkers in stored tissue sections. The effect of temperature and lighting on 49 cellular or microbial antigens was evaluated in 4 serial paraffin sections, cut 12 months, 10 months, 8 months, 5 months, 3 months, 1 month, 3 days, and 1 day before immunohistochemistry. Slides were stored at room temperature (RT) in the dark, at 4°C in the dark, at RT under fluorescent light, or at RT with windowpane exposure to sunlight. Immunohistochemistry was performed simultaneously in an automated immunostainer. Immunoreactivity was compared with that in the corresponding 1-day-old section and scored as 4 (<10% reduction), 3 (10%-25% reduction), 2 (26%-60% reduction), 1(>60% reduction), or 0 (no reactivity). Any loss of immunoreactivity was proportional to the tissue section age and was least in sections stored in the dark. Immunoreactivity was only completely lost in light-exposed sections and as early as 1 month for CD45. Other markers with complete loss of immunoreactivity were bovine viral diarrhea virus, CD18 (only with fluorescent light), CD31, CD68, canine parvovirus, chromogranins, and thyroid transcription factor-1. Markers with complete loss after light exposure also had reduced immunoreactivity when stored in the dark, as early as day 3. Eight markers (Bartonella spp, CD11d, high molecular weight cytokeratins, feline coronavirus, GATA-4, insulin, p63, progesterone receptor) had minimal decrease in immunoreactivity, regardless of treatment. In conclusion, light-induced antigen decay (tissue section aging) is antigen dependent and could explain unexpectedly weak or negative immunohistochemical reactions in stored paraffin sections.

CD31 angiogenesis and combined expression of HIF-1α and HIF-2α are prognostic in primary clear-cell renal cell carcinoma (CC-RCC), but HIFα transcriptional products are not: implications for antiangiogenic trials and HIFα biomarker studies in primary CC-RCC

Hypoxia-inducible factors, HIF-1α and HIF-2α, are expressed in the majority of clear-cell renal cell carcinoma (CC-RCC). In vitro, HIFα isoforms regulate a differential set of genes, and their effects in vivo within CC-RCC tumours may affect outcome. The role of angiogenesis and HIFα transcriptional products, including those involved in cell metabolism and morphological dedifferentiation have not been extensively investigated and might have relevance to the development of antiangiogenic or anti-HIFα trials in primary CC-RCC, either before or after radical nephrectomy. We analysed 168 consecutive clear-cell renal tumours from 1983 to 1999 within tissue microarrays and assessed expression of HIF-1α and HIF-2α together with the protein expression of seven of their target genes (BNIP3, CA9, Cyclin D1, GLUT-1, LDH5, Oct-4 and VEGF). The expression of these factors was compared with patient overall survival and CD31 angiogenesis. We found that HIFα antigenicity deteriorated with the age of the paraffin block (P < 0.0001) and in tumours from 1983 to 1992 was deemed not to be reliable. Similar findings were found in aged archival osteosarcoma samples. This might have important implications for retrospective biomarker studies that rely on archival tissue material. HIF-1α(HIGH)/HIF-2α(LOW) tumours had a worse overall survival compared with HIF-1α(LOW)/HIF-2α(LOW) tumours (P = 0.04). Surprisingly, on multivariate analysis, high levels of CD31(+) angiogenesis was shown to be an independent prognostic marker of increased overall survival (P = 0.003). We propose that better differentiation of vascular endothelium may be a reflection of a greater production of vessel stabilization factors versus pro-angiogenic factors, and therefore a less aggressive phenotype.

Effect of storage on p63 immunohistochemistry: a time-course study

One of the problems with immunohistochemistry is that storage of unstained slides can have a detectable negative effect on the intensity of staining for various antigens. This has not been well studied for the p63 antigen. A time-course study was performed to evaluate the effect of storage on the intensity of p63 immunohistochemical staining. Slides from various breast lesions/foci were stained with a p63 antibody on day 0 and after storage at room temperature for 2, 4, and 8 weeks. A p63 intensity score, ranging from 0 to 300, was calculated using the intensity (0, 1, 2, or 3+) and percentage of peripheral myoepithelial cell staining (0% to 100%). There was a progressive decline in the p63 intensity score with time with the differences between day 0 and 2 weeks and 2 and 4 weeks being statistically significant (P=0.037 and 0.001, respectively), whereas that between 4 and 8 weeks was not (P=0.075). These findings confirm a time-dependent decline in p63 immunostaining intensity evident as early as with 2 weeks of storage and still present after 8 weeks. This should be considered in the evaluation of p63 immunostains performed on stored unstained sections, both in diagnostic surgical pathology and in translational research studies.

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.

Increasing expression of hypoxia-inducible proteins in the Barrett's metaplasia-dysplasia-adenocarcinoma sequence

Hypoxia-associated markers are involved in the progression of several malignancies, but are relatively unstudied in Barrett's carcinogenesis. Our aim was to assess the immunohistochemical expression of hypoxia-inducible factor (HIF)-1α, HIF-2α, erythropoietin (Epo), Epo receptor (Epo-R), Glut-1 and vascular endothelial growth factor (VEGF) along with Ki67/MIB-1 in the Barrett's metaplasia–dysplasia–adenocarcinoma sequence. Endoscopic biopsies of normal squamous epithelium (NSE) (n=20), columnar-lined oesophagus (CLO) (n=15), CLO with intestinal metaplasia (n=20), dysplasia (n=17) and Barrett's type adenocarcinoma (n=20) were obtained. Immunohistochemistry was performed on the paraffin-embedded tissue. A score was calculated for each marker (range 0−300) by multiplying intensity (none 0, weak 1, moderate 2, strong 3) by percentage of expression (range 0–100). Significant increases in the expression of HIF-2α (P=0.014), VEGF (P<0.0001), Epo-R (P<0.0001) and Ki67 (P<0.0001) were found as tissue progressed from NSE to adenocarcinoma. HIF-2α was expressed late in the sequence and was only seen in dysplasia and adenocarcinoma. High HIF-2α expression was seen in 12 out of 20 Barrett's type adenocarcinoma. The late expression of HIF-2α in the Barrett's carcinogenesis sequence and its high expression in adenocarcinoma suggest that it is worth further investigation as a marker of disease progression and therapeutic target.

Hypoxia-inducible factor-1alpha expression in the gastric carcinogenesis sequence and its prognostic role in gastric and gastro-oesophageal adenocarcinomas

Hypoxia-inducible factor-1 (HIF-1)α expression was studied in the gastric carcinogenesis sequence and as a prognostic factor in surgically resected gastric and gastro-oesophageal junction tumours. Protein expression was examined using immunohistochemistry on formalin-fixed biopsies of normal mucosa (n=20), Helicobacter pylori associated gastritis (n=24), intestinal metaplasia (n=24), dysplasia (n=12) and intestinal (n=19) and diffuse (n=21) adenocarcinoma. The relationship between HIF-1α expression and prognosis was assessed in resection specimens from 177 patients with gastric and gastro-oesophageal junction adenocarcinoma. Hypoxia-inducible factor-1α expression was not observed in normal gastric mucosa but increased in density (P<0.01) and intensity (P<0.01) with progression from H. pylori-associated gastritis, intestinal metaplasia, dysplasia to adenocarcinoma. The pattern of staining in the resection specimens was focally positive in 49 (28%) and at the invasive tumour edge in 41 (23%). Invasive edge expression was associated with lymph node metastases (P=0.034), advanced TNM stage (P=0.001) and was an adverse prognostic factor for cancer-specific survival (P=0.019). In univariate analysis and in comparison with tumours not expressing HIF-1α, invasive edge staining was associated with a hazard ratio of 1.6 (95% CI 1.0−2.5) and focally positive staining a hazard ratio of 0.7 (95% CI 0.5−1.2). Hypoxia-inducible factor-1α lost prognostic significance in multivariate analysis. The results suggest HIF-1α is involved in gastric carcinogenesis and disease progression, but is only a weak prognostic factor for survival.

Hypoxia-inducible factor 1alpha expression as an intrinsic marker of hypoxia: correlation with tumor oxygen, pimonidazole measurements, and outcome in locally advanced carcinoma of the cervix

PURPOSE

Hypoxia-inducible factor (HIF)-1alpha expression was studied retrospectively in locally advanced carcinoma of the cervix in relation to other methods for measuring/assessing tumor hypoxia and outcome after radiotherapy.

EXPERIMENTAL DESIGN

HIF-1alpha expression was examined in formalin-fixed tumor biopsies using a semiquantitative scoring system and correlated with measurements of hypoxia obtained using oxygen electrodes, pimonidazole staining, and carbonic anhydrase 9.

RESULTS

High HIF-1alpha expression showed a weak correlation with low pO2 (r = -0.26; P = 0.030; n = 72). Weak significant correlations were found between HIF-1alpha and pimonidazole staining (r = 0.34; P = 0.040; n = 36) and carbonic anhydrase IX (r = 0.27; P = 0.001; n = 160). There was no relationship with surviving fraction at 2 Gy. The relationship between HIF-1alpha expression and radiotherapy outcome was examined in 99 patients. HIF-1alpha expression did not correlate with disease stage, grade, tumor size, and patient age. HIF-1alpha alone was not a significant prognostic factor for disease-free survival, metastasis-free survival, or local recurrence-free survival. High HIF-1alpha expression tended to be associated with poor outcome in small tumors but good outcome in large tumors, with statistically significant interactions between HIF-1alpha and tumor size for survival (P = 0.046) and local control (P = 0.009).

CONCLUSIONS

In this study, HIF-1alpha had no prognostic significance in locally advanced carcinoma of the cervix. The possible switch in large tumors for an association between high HIF-1alpha expression and good outcome might relate to tumor size-related changes in the balance of genes up-regulated by HIF-1alpha. Whereas angiogenesis-promoting genes might be preferentially up-regulated in small tumors, proapoptotic genes might be induced in large tumors. This hypothesis needs testing in future work.