Reliability of immunohistochemical demonstration of oestrogen receptors in routine practice: interlaboratory variance in the sensitivity of detection and evaluation of scoring systems

AIMS

To investigate interlaboratory variance in the immunohistochemical (IHC) detection of oestrogen receptors so as to determine the rate of false negatives, which could adversely influence the decision to give adjuvant tamoxifen treatment.

METHODS

To ensure that similar results are obtained by different institutions, 200 laboratories from 26 countries have joined the UK national external quality assessment scheme for immunocytochemistry (NEQAS-ICC). Histological sections from breast cancers having low, medium, and high levels of oestrogen receptor expression were sent to each of the laboratories for immunohistochemical staining. The results obtained were evaluated for the sensitivity of detection, first by estimating threshold values of 1% and 10% of stained tumour cells, and second by the Quick score method, by a panel of four assessors judging individual sections independently on a single blind basis. The results were also evaluated using participants' own threshold values.

RESULTS

Over 80% of laboratories were able to demonstrate oestrogen receptor positivity on the medium and high expressing tumours, but only 37% of laboratories scored adequately on the low expressing tumour. Approximately one third of laboratories failed to register any positive staining in this tumour, while one third showed only minimal positivity.

CONCLUSIONS

There is considerable interlaboratory variability, especially in relation to the detection of breast cancers with low oestrogen receptor positivity, with a false negative rate of between 30% and 60%. This variability appears to be caused by minor differences in methodology that may be rectified by fine adjustment of overall technique.

High metallothionein expression is associated with features predictive of aggressive behaviour in endometrial carcinoma

AIMS

Metallothioneins (MTs) are a group of ubiquitous low molecular weight proteins with a high affinity for heavy metal ions. The aim of the present study was to investigate MT expression in a series of endometrial carcinomas. We wished to determine whether MT expression in endometrial carcinoma was related to established prognostic factors such as tumour grade, stage and histological type. We also wanted to establish if high MT expression in curettings of endometrial carcinoma was predictive of high expression in the subsequent hysterectomy specimen.

METHODS AND RESULTS

Sixty-three cases of endometrial carcinoma were included in the study. These comprised 57 endometrioid adenocarcinomas (15 grade 1, 25 grade 2, 17 grade 3), three papillary serous adenocarcinomas, two mucinous adenocarcinomas and one clear cell adenocarcinoma. Forty-five tumours were stage I, 10 were stage II and eight were stage III. In 28 cases, diagnostic endometrial curettings, performed prior to hysterectomy, were available for study. Immunohistochemical staining was performed using the anti-MT monoclonal antibody E9. The intensity and distribution of MT staining were assessed using a semiquantitative method. This resulted in an intensity distribution (ID) score out of a maximum of 300. The mean ID score of grade 1 and 2 endometrioid adenocarcinomas was 67 and 63, respectively, while for grade 3 tumours the mean ID score was 114. This was statistically significant (P = 0.05). The three papillary serous adenocarcinomas had high ID scores with a mean of 208. The mean ID score of stage I tumours was 69. This was lower than those of stage II and III tumours which had mean ID scores of 116 and 128, respectively. However, these differences were not statistically significant (P = 0.288). A significant correlation was observed between MT ID scores in endometrial curettings and in the subsequent hysterectomy (P = 0.013).

CONCLUSIONS

MT isoforms can be demonstrated in most endometrial adenocarcinomas. High MT ID scores are associated with high grade and high stage endometrial adenocarcinomas and with the aggressive papillary serous adenocarcinoma. Whether this is of value as an independent prognostic factor has yet to be established.

Immunocytochemical detection of metallothionein (MT1 and MT2) in copper-enhanced sheep brains

The role of metallothionein (MT) in the brain in heavy metal detoxification is relatively unexplored. Brain copper (Cu) elevation although unusual in chronic Cu poisoning in sheep, has been shown to occur after treatment with the chelating agent ammonium tetrathiomolybdate (TTM). The aim of this study was to investigate the expression of MT in TTM Cu-enhanced sheep brains, with immunohistochemical techniques. Brains from TTM-treated, Cu-poisoned sheep were examined for MT immunolabelling with a mouse monoclonal antibody (E9) for MT1 and MT2, and compared with brains from untreated sheep. Brain samples were analysed separately for Cu and zinc (Zn) by atomic absorption spectrophotometry. Markedly increased MT immunoreactivity was found in astrocytes of the cerebellum, thalamus/hypothalamus, cerebrum and medulla oblongata of the high-Cu brains, corresponding to the regional Cu elevations. MT immunolabelling was also found in the pia mater, choroid plexus and ependymal cells. Neurons were rarely labelled. MT induction within astrocytes and at the blood-brain barrier suggests that these are sites of stabilization and possibly transport for Cu and supports the hypothesis that the astrocyte compartment modulates metal homeostasis, conferring protection on vulnerable neurons and effecting damage limitation.

Caveolin and its cellular and subcellular immunolocalisation in lung alveolar epithelium: implications for alveolar epithelial type I cell function

Caveolae are flask-shaped invaginations of the plasmalemma which pinch off to form discrete vesicles within the cell cytoplasm. Biochemically, caveolae may be distinguished by the presence of a protein, caveolin, that is the principal component of filaments constituting their striated cytoplasmic coat. Squamous alveolar epithelial type I (ATI) cells, comprising approximately 95% of the surface area of lung alveolar epithelium, possess numerous plasmalemmal invaginations and cytoplasmic vesicles ultrastructurally indicative of caveolae. However, an ultrastructural appearance does not universally imply the biochemical presence of caveolin. This immunocytochemical study has utilised a novel application of confocal laser scanning and electron microscopy unequivocally to localise caveolin-1 to ATI cells. Further, cytoplasmic vesicles and flask-shaped membrane invaginations in the ATI cell were morphologically identified whose membranes were decorated with anti-caveolin-1 immunogold label. Coexistent with this, however, in both ATI and capillary endothelial cells could be seen membrane invaginations morphologically characteristic of caveolae, but which lacked associated caveolin immunogold label. This could reflect a true biochemical heterogeneity in populations of morphologically similar plasmalemmal invaginations or an antigen threshold requirement for labelling. The cuboidal alveolar epithelial type II cell (ATII) also displayed specific label for caveolin-1 but with no ultrastructural evidence for the formation of caveolae. The biochemical association of caveolin with ATI cell vesicles has broad implications for the assignment and further study of ATI cell function.

SV40 DNA sequences in mesotheliomas

To investigate the presence of SV40 DNA sequences in human British mesotheliomas, PCR analysis using PYV and SV primers which amplify a 172 bp fragment of SV40LTAg and a 105 bp fragment unique to the SV40LTAg respectively was performed on archival and frozen tissues. Nine pleural mesotheliomas, nine adenocarcinomas metastatic to the pleura and three inflammatory disorders of the pleura were studied. PCR positivity with the SV primer set was restricted to four of the nine cases of mesothelioma with concordance between paraffin embedded and frozen tissues. Positivity with the PYV primer set was observed in six mesotheliomas, two adenocarcinomas and one of the reactive pleurae. This study indicates that SV40 DNA sequences are present in a substantial proportion of British mesotheliomas.

Silver development in microscopy and bioanalysis: past and present

With the experience accumulated from more than a century of silver applications in biology and medicine, physical development has become a powerful bioanalytical tool for marker amplification in blotting procedures, in situ hybridization, immunocytochemistry, histochemistry, and cytochemistry. Early, empirical techniques of silver impregnation followed by development in a reducing solution (chemical developer), or a solution which contained both silver reducers and silver salts (physical developer) were often capricious and suffered from unwanted silver precipitation caused by light and self-nucleation. To accommodate the modern demand for accurate physical development, various strategies have been devised to counter these problems. One approach has been to introduce organic colloids into the developer to keep the silver ions and reducer molecules apart, whilst excluding light by using a dark-room or by covering the solution. Albumen, gelatin, and complex polysaccharides have all been tested, but gum arabic is preferred. In addition, further control can be achieved by slowing down the rate of development with low pH and by changing from silver nitrate to silver lactate, which dissociates more slowly. Effective colloid protection in a physical developer is also provided by the inclusion of tungsten salts which can delay light-catalysed silver reduction and keep the developer clear for many minutes. The same result has been achieved by complexing the silver salt in the physical developer with very large organic molecules, restricting ionization. 'Light insensitive' commercial designer products have resulted. Probably no single formulation can satisfy all conditions of use, but with increased understanding of the mechanisms of physical developers a more flexible, user-friendly approach is anticipated.

Silver development in microscopy and bioanalysis: a new versatile formulation for modern needs

Potentially, silver development could unify most modern demands for clean, accurately localized marker amplification in microscopy and bioanalysis. However, the existing technology leaves room for improvement in developer design. A new formulation has been devised which, by using principles of silver chelation, avoids problems of self-nucleation and catalysis by light. It is made, just before use, by mixing together equal amounts of stock solutions containing high molarity, Tris-buffered silver nitrate and alcoholic, buffered pyrogallol. The two stocks are easily prepared and have very long shelf-lives. The developer is light insensitive for up to an hour at room temperature, so that development can proceed under ambient light conditions and at the neutral pH most suited to biological systems. The powerful reducer in the suggested formulation should allow the detection of low concentrations of marker signal in a wide range of applications.

Immunohistochemical retrieval of the principal HIV antigens p24, gp41, and gp120 in formalin fixed tissue: an investigation using HIV infected lymphoblasts and postmortem brain tissue from AIDS cases

This paper describes the use of an autoclaving procedure followed by immunocytochemistry to enhance the detection of the human immunodeficiency virus (HIV) antigens p24, gp41, and gp120. This procedure greatly improved the detection rate of the p24 and gp41 HIV surface antigens in formalin fixed, paraffin wax embedded, HIV positive central nervous system (CNS) tissue while restricting staining to areas of the CNS showing evidence of neuropathology. However, the technique did not improve retrieval of the gp120 antigen in either HIV positive, formalin fixed CNS tissue or HIV infected T lymphoblasts. The inclusion of the high temperature autoclave step was validated using both HIV infected lymphoblasts and pre-adsorption of the specific antibodies with the appropriate recombinant HIV proteins. Using the methodology described here, formalin fixed CNS tissue from potential or known HIV positive cases can be processed reliably and safely. To ensure the reliability of this technique, it is recommended that an assessment of both the p24 and gp41 antigens is undertaken.

Human wound contraction: collagen organization, fibroblasts, and myofibroblasts

The closure of ungrafted sacrococcygeal pilonidal sinus excisional wounds was studied in 15 patients. Wound punch biopsies were taken on a regular basis, and histologic sections were made. To document changes, computer-assisted morphometric image analysis was employed. Initial average wound depth was 37.8 +/- 4.6 mm, and complete closure (0 wound depth) was reached by 68 days. Wound contraction contributed 88 percent to wound closure, whereas the deposition of scar only contributed 12 percent. Maximum cells density within granulation tissue was reached by day 18. Myofibroblasts, identified by alpha-smooth muscle actin immunostaining, first appeared on day 11. Unlike those observed in laboratory animals, myofibroblasts were a minor cell population of granulation tissue, never exceeding 10 percent of the cells. The pattern of collagen fiber organization was documented by polarized light microscopy of Sirius red-stained sections. Early granulation tissue collagen fibers demonstrated a fine greenish birefringence, whereas more mature granulation tissue collagen fibers were thicker, displaying orange-yellowish birefringence. Myofibroblasts were associated exclusively with thicker collagen fibers, whereas fibroblasts were associated with both fine and thick collagen fibers. It is proposed that human wound contraction involves a volume change whereby normal dermal and adipose tissues are pulled into the defect by forces generated within fibroblasts.

Immortalized human pituitary cells express glycoprotein alpha-subunit and thyrotropin beta (TSH beta)

A major problem in the study of human pituitary cells is their lack of proliferative capacity in vitro. To address this issue, we have infected normal human, postmortem pituitary cells in monolayer culture with a temperature-sensitive (tsA58) mutant of SV40 large T antigen. Several epithelial-like colonies were isolated; and one, designated CHP2, has been studied in detail to identify its functional characteristics. CHP2 cells have undergone more than 150 culture passages and retain an epithelial morphology. They exhibit tight temperature-dependent growth, in the presence and absence of serum, with cell division at 33 C and growth inhibition at 39 C. CHP2 cells, at both temperatures, showed diffuse immunostaining for human alpha-subunit and focal staining for TSH beta. Gene expression was confirmed by RT-PCR and sequencing. TRH and GnRH receptors were not detectable, and their absence was confirmed by their lack of effects on intracellular calcium and inositol phospholipids. Cytogenetic analysis showed that the cells had a modal peak in the diploid range and a smaller peak in the tetraploid range. There was also a consistent loss of chromosome 22 and a normal chromosome 2 homologue, the latter being replaced by one of two chromosome 2 markers, M2A or M2B. In conclusion, we have immortalized human pituitary cells using SV40 tsT, from which we have cloned a cell line expressing alpha-subunit and TSH beta.

Clonal overexpression of metallothionein is induced by somatic mutation in morphologically normal colonic mucosa

Metallothionein (MT) overexpression occurs frequently in human tumours but the underlying mechanism is unknown. Morphologically normal-appearing mucosa from human colorectal carcinoma resection specimens and of the colons of ageing laboratory mice contains scattered single crypts whose cells show uniformly increased MT immunostaining, suggesting that MT overexpression arises directly from random crypt stem cell somatic mutation, followed by colonization of the clonal unit by the mutated progeny. This hypothesis has now been tested by quantifying the frequency of immunocytochemically detectable monocryptal colorectal MT overexpression, 5 and 30 days after injection of 8-week-old mice with a single dose of the mutagen dimethylhydrazine (DMH, 30 mg/kg subcutaneous). Otherwise normal-appearing MT-positive crypts were recorded as either wholly or partially involved by the overexpressing phenotype. Five days after DMH injection, the median frequency of partially involved MT-positive crypts was 11.7 x 10(-4), declining significantly to 1.8 x 10(-4) at 30 days (Mann-Whitney U, P < 0.01). In contrast, the median frequency of wholly involved crypts was 0.2 x 10(-4) at 5 days, increasing significantly (P < 0.005) to 12.9 x 10(-4) at 30 days. The frequency of MT-positive crypts and the time course of evolution of partially involved to wholly involved forms were similar to those described for mutation-induced crypt-restricted loss of glucose-6-phosphate dehydrogenase activity in mice treated with an identical DMH regimen. The findings indicate that cellular MT overexpression can occur as a direct consequence of somatic mutation, either cis-activating mutation(s) of the MT gene itself, or trans-activating mutation(s) of other genes involved in controlling MT expression. This is likely to be an important mechanism underlying MT overexpression in neoplasia. Such mutation-induced aberrant MT expression may be involved in the acquisition of selective cellular growth of survival advantage during tumour progression.

Metallothionein overexpression in human brain tumours

Metallothioneins (MTs) are metal binding proteins overexpressed in various human neoplasms which are associated with resistance to cytotoxic drugs. A series of 156 archival human brain tumours were investigated immunohistochemically for expression of MTs; these included 10 low-grade gliomas, 44 high-grade gliomas, 98 meningeal tumours (19 classical, 30 atypical, 38 anaplastic meningiomas, and 11 haemangiopericytomas or papillary meningiomas), and 4 other tumours. Low-grade gliomas showed heterogeneous MT expression; 32 high-grade gliomas (72.7%) showed MT expression of more than 25% of tumour cells without statistically significant differences between first operations and recurrent tumours. In 2 glioblastomas, the presence of MT was confirmed by Western blotting. The extent of MT immunoexpression showed a statistically significant inverse relationship to the degree of p53 immunoreactivity. In meningiomas, a tendency to a higher percentage of MT-expressing cells was observed from classical over atypical to anaplastic meningiomas, but these differences were not statistically significant. In conclusion, MT expression is present in a significant portion of, especially malignant, brain tumours and might be involved in their poor response to antineoplastic drugs.

Role of calcium chelation in high-temperature antigen retrieval at different pH values

Recent work by Shi et al. on the mechanism of high-temperature antigen retrieval has claimed that the antigen retrieval process is pH-dependent, with different antigens benefitting at high or low pH values of antigen retrieval solutions. It has previously been claimed that chelation of Ca2+ at high temperature is an essential feature of the antigen retrieval process. In order to resolve this apparent dichotomy, the relative antigen retrieval effects were analysed using the buffers employed by Shi et al. in both a facilitating and an inhibitory mode. The results show that calcium-related effects are optimal at high pH values and do not operate at very low pH. The relative antigen retrieval effectiveness of hydrochloric acid and its metal halide solutions were also investigated in relation to pH. The results of these experiments showed that whilst HCl alone produced antigen retrieval (AR), it also produced severe tissue damage, which was reduced by the inclusion of inorganic salts. These results suggest that antigen retrieval at low pH may be achieved through the dissociation of Ca2+ complexes by high concentrations of H+ ions and/or the breaking up of cross-links from formalin fixation. Results are also presented to show that chaotropic denaturants such as urea and guanidine hydrochloride also function principally through calcium chelation, whilst detergents have no role to play in high-temperature retrieval.

Apoptosis in autoimmune and non-autoimmune thyroid disease

The elimination of autoreactive T cells in the thymus involves the process of programmed cell death. Animal model studies, using the lpr and gld strains of mice, have identified FAS receptor (FAS) and FAS ligand (FAS-L) as important components of this mechanism. Whether FAS and FAS-L are also implicated in the autoimmune destruction of a target organ, such as the thyroid, remain hypothetical. An accompanying paper in this issue has addressed the question by FACS and immunocytochemical analysis of FAS expression and apoptosis in thyrocytes grown in culture and in intact thyroid tissues obtained from Hashimoto's thyroiditis, multinodular goitre and Graves' disease. The overall results suggest that the degree of FAS expression on target cells may determine their sensitivity to T-cell mediated cytotoxicity in the absence of perforin or granzyme directed apoptosis mechanisms.

Immunoreactive p53 and metallothionein expression in duct carcinoma in situ of the breast. No correlation

Immunocytochemically detectable MT and p53 have been found more commonly in comedo DCIS of the breast with high-grade cytology. The aim of this study is to confirm these findings and to investigate the relationship between MT and p53 in a single large series of cases of DCIS of the breast. To this end, 127 cases of DCIS were classified histologically according to architecture, cytonuclear differentiation (grade), presence and extent of intraduct necrosis, and using the Van Nuys system. Sections were immunostained for p53 and MT (E9) using established techniques, and the extent and intensity of staining were assessed semi-quantitively. The results confirmed that there was generally more MT and p53 positivity in poorly differentiated (grade 3) DCIS with extensive necrosis and that MT expression was greater in grade 2 lesions than p53 expression. However, overall there was no statistically significant correlation between p53 and MT staining. The results indicate that MT and p53 overexpression may arise from independent mechanisms in early breast neoplasia.

Loss of E-cadherin expression associated with lymph node metastases in small breast carcinomas

The National Breast Screening Programme affords the opportunity to study breast carcinomas at an early stage in their development. E-cadherin is a calcium-dependent, intercellular adhesion molecule whose loss of expression may facilitate the processes of invasion and metastasis of some human tumours. From a group of screen-detected ductal carcinomas less than or equal to 10 mm in diameter, 16 with lymph node metastasis were identified and matched for grade, size and patient age with node negative tumours. The level of expression of E-cadherin (detected by immunocytochemistry) was compared in the matched pairs using a simple semi-quantitative intensity distribution scoring system. The results showed a significant (P = 0.05 Wilcoxon paired rank test) reduction of E-cadherin expression in tumours with lymph node metastases compared to those without. In the context of the small size of these tumours it is proposed that these results support the hypothesis that reduction in E-cadherin expression is an early event in the development of metastases.

Immunocytochemical identification of metallothionein-positive cells in rheumatoid synovium and analysis of their cell lineage

Metallothionein is a ubiquitous low molecular weight metalloprotein with powerful protective properties against oxygen radical-mediated cytotoxicity associated with inflammatory processes. In rheumatoid arthritis, the inflammatory damage to the synovium appears to be mediated by free radicals released by the high concentration of neutrophils found in the synovial fluid of the inflamed joint. Synovial tissue obtained during routine surgery on rheumatoid and non-rheumatoid joints was subjected to an indirect immunoperoxidase protocol for the immunolocalization of metallothionein using mouse monoclonal anti-metallothionein antibody E9, reactive against the two major isoforms of mammalian metallothionein. A layer of large dendritic-like cells situated subsynovially in the rheumatoid synovium stained very positively for the metalloprotein, both cytoplasmically and in their nuclei. These cells were not found in non-rheumatoid osteoarthritic or in undamaged synovial tissue associated with traumatic joint injury. An attempt was made to investigate their lineage using a series of antibody markers against epithelial cells, endothelial cells, smooth muscle, mesothelial cells, fibroblasts, neutrophils, dermal dendrocytes, macrophages, low and high molecular weight cytokeratin as well as a cell proliferation marker. From our results, it is suggested that these metallothionein-positive cells are probably myofibroblasts similar to the highly motile cells present in granulation tissue. They may originate from perivascular areas of synovium and their movement into the inflamed synovium may reflect the cytoprotective role of metallothionein acting as a free radical scavenger against oxidative damage.