Heat pretreatment increases resolution in DNA flow cytometry of paraffin-embedded tumor tissue

Epigenomic analysis of formalin-fixed paraffin-embedded samples by CUT&Tag

For more than a century, formalin-fixed paraffin-embedded (FFPE) sample preparation has been the preferred method for long-term preservation of biological material. However, the use of FFPE samples for epigenomic studies has been difficult because of chromatin damage from long exposure to high concentrations of formaldehyde. Previously, we introduced Cleavage Under Targeted Accessible Chromatin (CUTAC), an antibody-targeted chromatin accessibility mapping protocol based on CUT&Tag. Here we show that simple modifications of our CUTAC protocol either in single tubes or directly on slides produce high-resolution maps of paused RNA Polymerase II at enhancers and promoters using FFPE samples. We find that transcriptional regulatory element differences produced by FFPE-CUTAC distinguish between mouse brain tumors and identify and map regulatory element markers with high confidence and precision, including microRNAs not detectable by RNA-seq. Our simple workflows make possible affordable epigenomic profiling of archived biological samples for biomarker identification, clinical applications and retrospective studies.

One-fits-all pretreatment protocol facilitating Fluorescence In Situ Hybridization on formalin-fixed paraffin-embedded, fresh frozen and cytological slides

Background

The Fluorescence In Situ Hybridization (FISH) technique is a very useful tool for diagnostic and prognostic purposes in molecular pathology. However, clinical testing on patient tissue is challenging due to variables of tissue processing that can influence the quality of the results. This emphasizes the necessity of a standardized FISH protocol with a high hybridization efficiency. We present a pretreatment protocol that is easy, reproducible, cost-effective, and facilitates FISH on all types of patient material simultaneously with good quality results.

During validation, FISH analysis was performed simultaneously on formalin-fixed paraffin-embedded, fresh frozen and cytological patient material in combination with commercial probes using our optimized one-fits-all pretreatment protocol. An optimally processed sample is characterized by strong specific signals, intact nuclear membranes, non-disturbing autofluorescence and a homogeneous DAPI staining.

Results

In our retrospective cohort of 3881 patient samples, overall 93% of the FISH samples displayed good quality results leading to a patient diagnosis. All FISH were assessed on quality aspects such as adequacy and consistency of signal strength (brightness), lack of background and / or cross-hybridization signals, and additionally the presence of appropriate control signals were evaluated to assure probe accuracy. In our analysis 38 different FISH probes from 3 commercial manufacturers were used (Cytocell, Vysis and ZytoLight). The majority of the patients in this cohort displayed good signal quality and barely non-specific background fluorescence on all tissue types independent of which commercial probe was used.

Conclusion

The optimized one-fits-all FISH method is robust, reliable and reproducible to deliver an accurate result for patient diagnostics in a lean workflow and cost-effective manner. This protocol can be used for widespread application in cancer and non-cancer diagnostics and research.

Cell sorting in cancer research--diminishing degree of cell heterogeneity

Increasing evidence of intratumor heterogeneity and its augmentation due to selective pressure of microenvironment and recent achievements in cancer therapeutics lead to the need to investigate and track the tumor subclonal structure. Cell sorting of heterogeneous subpopulations of tumor and tumor-associated cells has been a long established strategy in cancer research. Advancement in lasers, computer technology and optics has led to a new generation of flow cytometers and cell sorters capable of high-speed processing of single cell suspensions. Over the last several years cell sorting was used in combination with molecular biological methods, imaging and proteomics to characterize primary and metastatic cancer cell populations, minimal residual disease and single tumor cells. It was the principal method for identification and characterization of cancer stem cells. Analysis of single cancer cells may improve early detection of tumors, monitoring of circulating tumor cells, evaluation of intratumor heterogeneity and chemotherapeutic treatments. The aim of this review is to provide an overview of major cell sorting applications and approaches with new prospective developments such as microfluidics and microchip technologies.

Data-driven compensation for flow cytometry of solid tissues

Propidium Iodide is a fluorochrome that is used to measure the DNA content of individual cells, taken from solid tissues, with a flow cytometer. Compensation for spectral cross-over of this fluorochrome still leads to compensation results that are depending on operator experience. We present a data-driven compensation (DDC) algorithm that is designed to automatically compensate combined DNA phenotype flow cytometry acquisitions. The generated compensation values of the DDC algorithm are validated by comparison with manually determined compensation values. The results show that (1) compensation of two-color flow cytometry leads to comparable results using either manual compensation or the DDC method; (2) DDC can calculate sample-specific compensation trace lines; (3) the effects of two different approaches to calculate compensation values can be visualized within one sample. We conclude that the DDC algorithm contributes to the standardization of compensation for spectral cross-over in flow cytometry of solid tissues.

High-resolution multiparameter DNA flow cytometry for the detection and sorting of tumor and stromal subpopulations from paraffin-embedded tissues

This unit contains a detailed protocol for the simultaneous flow cytometric measurement of tumor cells, stromal cells, and DNA content of formalin-fixed, paraffin-embedded (FFPE) tissues. The vimentin-positive stromal cell fraction can be used as an internal reference for DNA content assessments. This allows clear detection of keratin-positive tumor cells with a DNA index lower than 1.0 and of keratin-positive tumor cells with a DNA close to 1.0 in overall DNA aneuploid samples, thus improved DNA ploidy assessment in FFPE carcinomas. Furthermore, the protocol is useful for studying molecular genetic alterations and intratumor heterogeneity in archival FFPE samples. Keratin-positive tumor cell fractions can be flow-sorted for further molecular genetic analysis, while DNA from the sorted vimentin-positive stromal cells can serve as a reference when normal tissue of the patient is not available.

Fluorescent in situ hybridization heating pretreatment: the key is temperature control

Fluorescent in situ hybridization (FISH) is a very useful tool for diagnostic and prognostic purposes in pathology. However, many laboratories still experience troubles when applying FISH to paraffin material. To overcome these difficulties, different pretreatments which include enzymatic digestion have been described. Usually, previous to digestion, a heating step is performed. The aim of this study was to compare the efficiency of the heating step with different buffers and different heating methods. We conclude that the main factor in the heating pretreatment is the temperature control, irrespective of the buffer used. Best results are obtained with any buffer by heating the slides to 99°C for 15 min followed by 10 min at room temperature.

High-resolution multiparameter DNA flow cytometry for the detection and sorting of tumor and stromal subpopulations from paraffin-embedded tissues

This unit contains a detailed protocol for the simultaneous flow cytometric measurement of tumor cells, stromal cells, and DNA content of formalin-fixed, paraffin-embedded (FFPE) tissues. The vimentin-positive stromal cell fraction can be used as an internal reference for DNA content assessments. This allows clear detection of keratin-positive tumor cells with a DNA index lower than 1.0 and of keratin-positive tumor cells with a DNA close to 1.0 in overall DNA aneuploid samples, thus improved DNA ploidy assessment in FFPE carcinomas. Furthermore, the protocol is useful for studying molecular genetic alterations and intratumor heterogeneity in archival FFPE samples. Keratin-positive tumor cell fractions can be flow-sorted for further molecular genetic analysis, while DNA from the sorted vimentin-positive stromal cells can serve as a reference when normal tissue of the patient is not available.

An efficient protocol for genomic DNA extraction from formalin-fixed paraffin-embedded tissues

Formalin-fixed paraffin-embedded tissues (FFPET) represent the largest source of archival biological material available for genomic studies. In this work we present an advanced protocol for extraction of high quality DNA from FFPET that can be applied in several molecular studies. Although cat mammary tumours (CMT) are the third most frequent tumour in cats the recovery of significant number of samples for molecular studies are in some way restricted to FFPET samples. We were able to obtain high quality DNA from FFPET of thirty six CMT that were subjected to pre-fixation and fixation processes routinely used in the veterinary hospitals. The quality of DNA obtained was tested by PCR amplification using six sets of primers that amplify single-copy fragments. The DNA fragments obtained were further sequenced. This protocol was able to provide FFPET gDNA that can be amplified and sequenced for larger fragments up to 1182bp.

Fluorescent stains for quantification of DNA by confocal laser scanning microscopy in 3-D

Confocal microscopy requires the use of fluorophores to visualize structures of interest within a specimen. To perform reliable measurements of the intensity of fluorescence, the stain should be specific, penetrate well into tissue sections, and bind stoichiometrically. Furthermore, emission must be linear with respect to DNA content and brightness, and fluorescence should be stable. Confocal microscopy is used to determine DNA ploidy and to analyze texture of nuclei, which is accomplished in three dimensions, because nuclei can be measured within the original tissue context. For this purpose the sample must be stained with a DNA binding fluorophore with the properties described above. Stains with different properties have been developed for different applications. We review here the advantages and disadvantages of these different stains for analyzing DNA ploidy and nuclear texture using three-dimensional microscopy. We conclude that SYBR green I and TO-PRO-3 are the most suitable stains for this purpose at present.

Heat-induced antigen retrieval: mechanisms and application to histochemistry

Since the introduction of the fluorescence-labeled antibody method by Coons et al. [Immunological properties of antibody containing a fluorescent group. Proc Soc Exp Biol Med 47, 200-2002], many immunohistochemical methods have been refined to obtain high sensitivity with low background staining at both light and electron microscopic levels. Heat-induced antigen retrieval (HIAR) reported by Shi et al. in the early 1990s has greatly contributed to immunohistochemical analysis for formalin-fixed and paraffin-embedded (FFPE) materials, particularly in the field of pathology. Although antigen retrieval techniques including enzyme digestion, treatment with protein denaturants and heating have been considered tricky and mysterious techniques, the mechanisms of HIAR have been rapidly elucidated. Heating cleaves crosslinks (methylene bridges) and add methylol groups in formaldehyde-fixed proteins and nucleic acids and extends polypeptides to unmask epitopes hidden in the inner portion of antigens or covered by adjacent macromolecules. In buffers having an appropriate pH and ion concentration, epitopes are exposed without entangling the extended polypeptides during cooling process, since polypeptides may strike a balance between hydrophobic attraction force and electrostatic repulsion force. Recent studies have demonstrated that HIAR is applicable for immunohistochemistry with various kinds of specimens, i.e., FFPE materials, frozen sections, plastic-embedded specimens, and physically fixed tissues at both the light- and electron-microscopic levels, and have suggested that the mechanism of HIAR is common to aldehyde-fixed and aldehyde-unfixed materials. Furthermore, heating has been shown to be effective for flow cytometry, nucleic acid histochemistry (fluorescein in situ hybridization (FISH), in situ hybridization (ISH), and terminal deoxynucleotidyl transferase-mediated nick labeling (TUNEL)), and extraction and analysis of macromolecules in both FFPE archive materials and specimens processed by other procedures. In this article, we review mechanism of HIAR and application of heating in both immunohistochemistry and other histochemical reactions.

Detection of tumor cells in body cavity fluids by flow cytometric and immunocytochemical analysis

Measurement of electronic volume versus DNA content of nuclei can be used to discriminate between normal and malignant cells. Epithelial membrane antigen immunocytochemistry (EMA-ICC), a helpful ancillary test in body cavity fluids, is not universally accurate for detecting malignancy in effusions. The current study was undertaken to determine if multiparametric flow cytometry (based on simultaneous analysis of light scatter, nuclear volume, DNA, and nuclear protein content) in combination with (EMA-ICC) could be used for the detection of malignant cells in peritoneal and pleural fluids. We studied 130 body cavity fluids (68 peritoneal and 62 pleural fluids) by conventional cytology and multiparametric laser flow cytometry. EMA-ICC was performed using EMA antibodies and L-SAB detection system (DakoCytomation, Carpinteria, CA). EMA-ICC had significantly higher sensitivity than conventional cytology (79% versus 59%, P = 0.016) and ploidy (79% versus 38%, P = 0.001). Cytology had significantly higher specificity than ploidy (97% versus 82%, P = 0.012). The differences in specificity between EMA-ICC and ploidy (87% versus 82%, P= 0.607) or EMA-ICC and cytology (87% versus 97%, P = 0.109) were not statistically significant. However, assuming serial testing, sensitivity increased significantly for the combinations of cytology and EMA-ICC (79.4%, P = 0.016) and cytology and ploidy (73.5%, P = 0.004) as compared to cytology alone (58.8%). Also, the combination of cytology and ploidy had a higher sensitivity than ploidy alone (73% versus 38%, P < 0.0001). However, the sensitivity associated with the three tests used in serial (85.3%) was not significantly different from the sensitivities corresponding to the combination of cytology and EMA-ICC (79%) or cytology and ploidy (73%). Multiparametric flow cytometry utilizing high resolution DNA, nuclear volume, protein measurement, and ICC, in combination with cytomorphology, may be a valuable tool for rapid identification of malignant cells in body cavity fluids.

CXCL12 Limits Inflammation by Localizing Mononuclear Infiltrates to the Perivascular Space during Experimental Autoimmune Encephalomyelitis

The inflammatory response in the CNS begins with the movement of leukocytes across the blood-brain barrier in a multistep process that requires cells to pass through a perivascular space before entering the parenchyma. The molecular mechanisms that orchestrate this movement are not known. The chemokine CXCL12 is highly expressed throughout the CNS by microendothelial cells under normal conditions, suggesting it might play a role maintaining the blood-brain barrier. We tested this hypothesis in the setting of experimental autoimmune encephalomyelitis (EAE) by using AMD3100, a specific antagonist of the CXCL12 receptor CXCR4. We demonstrate that the loss of CXCR4 activation enhances the migration of infiltrating leukocytes into the CNS parenchyma. CXCL12 is expressed at the basolateral surface of CNS endothelial cells in normal spinal cord and at the onset of EAE. This polarity is lost in vessels associated with an extensive parenchymal invasion of mononuclear cells during the peak of disease. Inhibition of CXCR4 activation during the induction of EAE leads to loss of the typical intense perivascular cuffs, which are replaced with widespread white matter infiltration of mononuclear cells, worsening the clinical severity of the disease and increasing inflammation. Taken together, these data suggest a novel anti-inflammatory role for CXCL12 during EAE in that it functions to localize CXCR4-expressing mononuclear cells to the perivascular space, thereby limiting the parenchymal infiltration of autoreactive effector cells.

The absence of CCL2 expression in cervical carcinoma is associated with increased survival and loss of heterozygosity at 17q11.2

To determine whether CCL2 mRNA expression is beneficial or detrimental for cervical cancer patients, the association between the expression of this molecule by cervical tumour cells, the number of tumour-associated macrophages, and clinicopathological parameters such as recurrence, relapse-free survival, and overall patient survival was investigated. In cervical cancer samples from 93 untreated cervical cancer patients, the CCL2 mRNA expression level was quantified using RNA in situ hybridization and verified using real-time quantitative RT-PCR. The number of tumour-associated macrophages was determined using immunohistochemistry. Furthermore, the study investigated whether lack of CCL2 expression was due to genetic alterations near the 17q11.2 (CCL2 genomic) region. CCL2 mRNA expression by cervical tumour cells was associated with the number of tumour-associated macrophages (p < 0.001). Lack of CCL2 mRNA expression (15 samples; 16%) was associated with increased cumulative relapse-free survival (log rank test, p = 0.030), increased cumulative overall survival (log rank test, p = 0.024), less post-operative surgery, reduced local and distant recurrence, reduced vascular invasion, and smaller tumour size (<40 mm). The absence of CCL2 mRNA expression corresponded with loss of heterozygosity (LOH) at 17q11.2 in five of six samples. The increased cumulative relapse-free survival and cumulative overall survival of cervical cancer patients lacking tumour cell-associated CCL2 mRNA suggest that the tumour-associated macrophages support tumour progression, presumably by promoting angiogenesis and production of growth factors.

Neuronal CXCL10 directs CD8+ T-cell recruitment and control of West Nile virus encephalitis

The activation and entry of antigen-specific CD8(+) T cells into the central nervous system is an essential step towards clearance of West Nile virus (WNV) from infected neurons. The molecular signals responsible for the directed migration of virus-specific T cells and their cellular sources are presently unknown. Here we demonstrate that in response to WNV infection, neurons secrete the chemokine CXCL10, which recruits effector T cells via the chemokine receptor CXCR3. Neutralization or a genetic deficiency of CXCL10 leads to a decrease in CXCR3(+) CD8(+) T-cell trafficking, an increase in viral burden in the brain, and enhanced morbidity and mortality. These data support a new paradigm in chemokine neurobiology, as neurons are not generally considered to generate antiviral immune responses, and CXCL10 may represent a novel neuroprotective agent in response to WNV infection in the central nervous system.

Determination of threshold values for determining the size of the fraction of steroid hormone receptor-positive tumor cells in paraffin-embedded breast carcinomas

BACKGROUND

For 4 years we used a multiparameter DNA flow cytometric (MP-FCM) technique to assess steroid hormone receptor expression in the diagnostic workup of routinely processed formalin-fixed, paraffin-embedded breast carcinomas as an alternative to immunohistochemistry (IHC) for the quantification of hormone receptor-positive cells. In all cases a positive fraction of hormone receptor-expressing epithelial cells was detected. This observation raised the question of what the cutoff value might be to distinguish receptor-negative from receptor-positive tumors.

METHODS

In our search for a possible threshold value of positivity for estrogen receptor (ER) and progesterone receptor (PR) in MP-FCM, we developed four steps. First, we compared IHC results in our own laboratory with the results obtained by MP-FCM on a small series of breast tumors (n = 42). Second, after collecting our first 843 tumors, we made a comparison with the literature of the distribution of receptor positivity according to age classes. Third, using the most likely threshold that resulted from this comparison, we compared a subset of 340 node-negative tumors for their combined ER/PR profiles with the data from a similar group of node-negative tumor cases from the National Cancer Institute's Surveillance, Epidemiology and End-Result (SEER) study. Fourth, with the results of these comparisons, we prospectively collected IHC data and MP-FCM results of the same tumor samples for a period of 1 year. In this way, we collected data for an additional 180 tumors.

RESULTS

The first step in this process resulted in an previous publication where 20% of steroid hormone receptor-positive cells seemed to be an acceptable cutoff point for positivity. However, the second step provided the best correlation at approximately 35% of ER reactive cells in the cytokeratin-positive cell population. With this cutoff, the distribution of combined ER/PR profiles in our patient population of node-negative breast cancers also showed a distribution similar to the data from the SEER study. The fourth step, using the 35% threshold value, resulted in a good correlation (r = 0.85, P < 0.0001) for ER and PR between IHC and MP-FCM in the 180 tumors investigated.

CONCLUSION

By comparing in-house data with those from large external data collections in the literature, a threshold percentage can be defined that distinguishes steroid hormone receptor-negative from hormone receptor-positive tumors. As a result, information about DNA content and cell cycle distribution can be obtained. This observational study provides additional support to our opinion that MP-FCM is an alternative for IHC determination of ER and PR positivity. It is more objective and quantification can be done more appropriately. The additional value of this approach is that we generate continuous variables of ER/PR content instead of categorical classes, which can be used at different threshold levels for evaluation of clinical relevance.

Standardised fluorescence in situ hybridisation in cytological and histological specimens

Fluorescence in situ hybridisation (FISH) has gained major impact in the detection of chromosomal aberrations. The application of FISH, however, is hampered due to complicated protocols. We therefore designed a FISH protocol that allows the fast and reliable application on cytological and histological specimens. Cytological and histological specimens of bone marrow, lymph nodes, liver and breast were analysed with 14 sets of centromere or locus-specific probes. A pretreatment of enzymatic digestion and microwave heating with the same incubation times for all specimens and probes used was performed. Hybridisation efficiency was proved by calculating the thresholds for monosomy, trisomy and translocations. Values in cytological specimens reached 9.0, 3.9 and 4.6%, respectively. In histological sections, values of 6.4% were seen for aneusomy and 3.1% for translocations. However, values for monosomy reached 20.5% in bone marrow and 61.8% in liver tissues due to cutting artifacts. In bone marrow with acute myeloid leukaemias, lymph nodes with follicular and mantle cell lymphomas, breast carcinomas and liver cell carcinomas, FISH confirmed aberrations already found using conventional cytogenetics. The protocol shown here is easy to perform and can be used with cytological and histological specimens. Moreover, with "hands on" time of less than 2 h, FISH can also be used for daily routine purposes.

High-resolution multi-parameter DNA flow cytometry enables detection of tumour and stromal cell subpopulations in paraffin-embedded tissues

The accuracy of DNA ploidy measurements of paraffin-embedded tissues is limited by the lack of resolution and the inability to identify the DNA diploid population unequivocally in bimodal DNA histograms. A multi-parameter DNA flow cytometric method has been developed that enables the simultaneous detection of neoplastic and stromal cells in samples from dewaxed 50 microm sections or 2 mm diameter punches of archival tissue blocks. The method combines heat pretreatment in sodium citrate buffer and subsequent enzymatic dissociation with a collagenase/dispase mixture. Cells were simultaneously stained for keratin (FITC), vimentin (R-PE), and DNA (PI) before flow cytometric analysis. The method was applied to 12 paraffin-embedded cervical carcinomas and four colorectal carcinomas. In all cervical cancers, distinct keratin-positive and vimentin-positive cell populations were observed. While the exclusive vimentin-positive cell fractions always yielded unimodal DNA content distributions, bimodal distributions were observed for the keratin-positive cell fractions in nine cervical carcinomas, whereas one cervical carcinoma showed three distinct G0G1 populations. Coefficients of variation of the G0G1 peaks ranged from 1.70% to 4.79%. Average background, aggregate, and debris values were 14.7% (vimentin-positive fraction) and 33.8% (keratin-positive fraction). Flow sorting confirmed that the exclusively vimentin-positive cell fractions represent different normal stromal and infiltrate cells that can serve as an internal ploidy reference enabling discrimination between DNA hypo-diploid and DNA hyper-diploid tumour cell subpopulations. The neoplastic origin of the keratin-vimentin co-expressing cells from two cervical carcinomas was confirmed by genotyping of flow-sorted samples revealing loss of heterozygosity (LOH) of 6p. This improved method obviates the need for fresh/frozen tumour tissue for high-resolution DNA ploidy measurements and enables the isolation of highly purified tumour subpopulations for subsequent genotyping.

A simple and reliable pretreatment protocol facilitates fluorescent in situ hybridisation on tissue microarrays of paraffin wax embedded tumour samples

AIMS

To describe a robust pretreatment protocol for preparing paraffin wax embedded tissues on tissue microarrays for fluorescence in situ hybridisation (FISH). The newly developed pretreatment protocol described here was compared with the commonly used sodium thiocyanate based protocol and two different heating methods used in standard antigen unmasking protocols for immunohistochemistry (pressure cooking and microwaving in citrate acid buffer).

METHODS

Dewaxed tissue sections were incubated in 10mM citric acid buffer at 80 degrees C for 30 minutes to two hours, followed by a short pepsin digestion (1-5 mg/ml). Pretreated tissues were co-denatured with DNA probes at 80 degrees C for 10 minutes, followed by hybridisation at 37 degrees C for 48-72 hours.

RESULTS

The three protocols using citrate acid buffer produced FISH signals with superior signal to noise ratios compared with sodium thiocyanate pretreatment. Most importantly, the best tissue attachment was achieved using the newly developed pretreatment protocol: on tissue microarrays less than 1% of cores were lost. To date, a total of 30 probes have been successfully hybridised on to breast tissue and multi-tissue microarrays.

CONCLUSION

This pretreatment protocol is easy, reproducible, and facilitates FISH on tissue microarrays, with potential for widespread application in cancer research.

Bone marrow precursor of extranodal T-cell lymphoma

The development of extranodal lymphomas is thought to be initiated by the transformation event in peripheral organs. Lymphomatoid papulosis (LyP) is a low-grade cutaneous lymphoma and may progress into the cutaneous anaplastic lymphoma. We identified 2 patients who 3 and 4 years before the development of LyP were treated for an unrelated malignancy (Burkitt lymphoma and small-cell B-cell lymphoma). We analyzed the T-cell receptor (TCR) gene rearrangement pattern in their skin, blood, and bone marrow, including the archival bone marrow sampled years before the development of clinically evident LyP. In all samples we detected the unique monoclonal TCR rearrangements. This observation suggests that the initial malignant transformation in LyP occurred in bone marrow and not, as could be supposed, in the skin.

Refining the diagnosis of hydatidiform mole: image ploidy analysis and p57KIP2 immunohistochemistry

AIM

To determine whether image analysis of ploidy status and immunohistochemical analysis of p57KIP2 (a paternally imprinted, maternally expressed gene) can be used to refine the diagnosis of molar pregnancy.

METHODS AND RESULTS

The original histological diagnosis in 40 randomly selected cases of hydatidiform mole was reviewed and confirmed in 38 cases (22 complete moles, 16 partial moles). These cases were anonymized and submitted for further analysis. Tissue from each case was submitted for flow cytometric assessment of DNA ploidy using a FACSort flow cytometer and for automated image cytometric assessment using a novel digital imaging system. Tissue sections from each case were immunostained with a monoclonal mouse antibody to p57KIP2. Correlations between the histopathological diagnosis, image cytometry, flow cytometry and p57KIP2 immunohistochemistry were determined using kappa statistics. The concordance between histological diagnosis and p57KIP2 was very good (kappa = 0.89). Twenty of the 22 (90.9%) complete moles showed no immunoreactivity for p57KIP2. The remaining two cases showed nuclear immunoreactivity in villous cytotrophoblast. In one of these, the pattern of staining resembled that of a partial mole. In the other, the staining pattern supported the diagnosis of a twin molar/non-molar pregnancy. All 16 partial moles were p57KIP2 immunoreactive. On flow cytometry, all 22 complete moles were diploid and 12/16 partial moles were triploid (the remaining four cases originally diagnosed as partial moles were found to be diploid). On image cytometry, one case originally diagnosed as complete mole was found to contain a triploid population. Thus, by using a combination of image cytometry and p57KIP2 status we were able to refine the diagnosis of molar pregnancy in five (13%) of the cases studied.

CONCLUSIONS

Automated image cytometry is a readily performed investigation which is comparable to, but more sensitive than, flow cytometry. Complementary use of ploidy analysis and p57KIP2 status can now help to distinguish a diploid hydropic miscarriage (p57KIP2-positive), diploid complete mole (p57KIP2-negative) and triploid partial mole (p57KIP2-positive).

Simultaneous detection of apoptosis and proliferation in colorectal carcinoma by multiparameter flow cytometry allows separation of high and low-turnover tumors with distinct clinical outcome

BACKGROUND

Dukes C colorectal carcinoma is treated with adjuvant chemotherapy. Adjuvant treatment is not standard for patients with Dukes B tumors, even though about 20% of patients within this tumor stage die of recurrent disease. The authors investigated whether a novel method of simultaneous detection of apoptosis and proliferation would improve the assessment of prognosis in colorectal carcinoma patients, with the ultimate goal of accurately identifying patients eligible for adjuvant therapy.

METHODS

A multiparameter flow cytometric assay with heat pretreatment was performed on 278 paraffin-embedded colorectal adenocarcinomas. After immunochemical isolation of tumor cells, apoptosis and proliferation were assessed simultaneously by immunostaining for the M30 antibody and by quantitative DNA analysis, respectively. Patients were followed for more than 10 years.

RESULTS

The mean values of apoptosis (apoptotic fraction [AF], i.e., the percentage of M30-positive cells) and proliferation (S-phase fraction [SPF]) were 11.1% and 13.1%, respectively. The AF and SPF values were correlated positively (P = 0.01) and both increased with advancing tumor stage (P = 0.02). Combining AF and SPF, patients with tumors with a high turnover (i.e., both AF and SPF values were greater than the mean) had an overall survival rate of 13%, whereas patients with low-turnover tumors (i.e., both AF and SPF values were less than the mean) had an overall survival rate of 89% (P < 0.001 by log rank test). Moreover, within Dukes B and C stages, patients with high-turnover tumors had a poorer survival than patients with low-turnover tumors (P < 0.001 for both stages).

CONCLUSIONS

The simultaneous detection of apoptosis and proliferation in archival material allows separation of high and low-turnover colorectal adenocarcinomas and improves the assessment of prognosis. This technique could be used to stratify patients for adjuvant chemotherapy.

Expression of T-cell activation marker CD134 (OX40) in lymphomatoid papulosis

BACKGROUND

CD134/OX40 and CD30 are transmembrane proteins from the tumour necrosis factor receptor (TNFR) family present selectively on activated T cells. TNFR-related proteins are crucially involved in the regulation of proliferation and survival of normal and malignant lymphohaematopoietic cells. CD30 has been used for the immunophenotyping and subclassification of cutaneous lymphomas; virtually nothing is known, however, about the expression pattern of CD134 in lymphoid skin malignancies.

OBJECTIVES

To determine CD134 expression in cutaneous lymphoma and benign inflammatory disorders.

METHODS

Biopsy material was obtained from patients with lymphomatoid papulosis (LyP, n = 42), mycosis fungoides (n = 21), Jessner's infiltrates (n = 10) and non-specific dermatitis (n = 14). The expression of CD134 and CD30 was scored after immunohistochemical staining with appropriate monoclonal antibodies. The proportion of G2 + S phase cells was determined by laser scanning cytometry from nuclei obtained from paraffin-embedded biopsies.

RESULTS

Few, single and scattered CD134+ cells (< 10%) were observed in the benign inflammatory infiltrations and in mycosis fungoides. A subset of 16 patients with LyP presented with clusters of CD30+ CD134+ cells. There was no correlation between the magnitude of CD134 expression and the histological type or the proportion of G2 + S cells in LyP. CD134 immunoreactivity was lower than expected in patients with LyP and another lymphoid malignancy (P < 0.001, Fisher's exact test).

CONCLUSIONS

CD134 is strongly expressed in a proportion (38%) of patients with LyP, but not in mycosis fungoides or benign lymphocytic infiltrations. Loss of CD134 expression in LyP may be a marker of an increased risk of second lymphoid malignancy.

Multiparameter flow cytometry as a tool for the detection of micrometastatic tumour cells in the sentinel lymph node procedure of patients with breast cancer

AIM

To investigate whether multiparameter flow cytometry (MP-FCM) can be used for the detection of micrometastasis in sentinel lymph nodes (SLNs) in breast cancer.

METHODS

Formalin fixed, paraffin wax embedded sentinel lymph nodes (n = 238) from 98 patients were analysed. For each lymph node, sections for haematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) for cytokeratin (MNF116) were cut at three levels with a distance of 500 microm. The intervening material was used for MP-FCM. Cells were immunostained with MNF116, followed by an incubation with fluorescein isothiocyanate (FITC) labelled goat antimouse immunoglobulin. DNA was stained using propidium iodide. From each lymph node 100,000 cells were analysed on the flow cytometer.

RESULTS

Thirty eight of the 98 patients with breast carcinoma showed evidence of metastatic disease in the SLN by one ore more of the three methods. In 37 of 38 cases where metastatic cells were seen in the routine H&E and/or IHC, more than 1% cytokeratin positive cells were detected by MP-FCM. In 24 patients, metastatic foci were more than 2 mm (macrometastasis) and in 14 these foci were smaller than 2 mm (micrometastasis). In three of these 14 cases, MP-FCM revealed positive SLNs, although this was not seen at first glance in the H&E or IHC sections. After revision of the slides, one of these three remained negative. However, MP-FCM analysis of the cytokeratin positive cells showed an aneuploid DNA peak, which was almost identical to that of the primary breast tumour. Duplicate measurements, done in 41 cases, showed a 99% reproducibility. In five of 14 patients with micrometastasis, one or two metastatic foci were found in the non-SLN. However, in 15 of 24 macrometastases multiple non-SLNs were found to have metastatic tumour. All micrometastases except for the remaining negative one mentioned above showed only diploid tumour cells, despite the fact that their primary tumours contained both diploid and aneuploid tumour cells. In primary tumours with more than 60% aneuploid cells, predominantly aneuploid macrometastasis were found, whereas diploid primary tumours only showed diploid micrometastases or macrometastases in their SLN. Aneuploid SLN macrometastases were associated with non-SLN metastases in five of seven patients, whereas diploid cases showed additional non-SLN metastases in only seven of 16 patients.

CONCLUSION

In all cases, MP-FCM was sufficient to detect micrometastatic tumour cells in a large volume of lymph node tissue from SLNs. In some cases it was superior to H&E and IHC staining. Approximately 30% of SLN micrometastases are accompanied by additional non-SLN metastases. The size of the aneuploid fraction (> 60%) in the primary tumour may influence the risk of having both SLN and non-SLN metastases.

Steroid receptor heterogeneity in relation to DNA index in breast cancer: a multiparameter flow cytometric approach on paraffin-embedded tumor samples

Steroid hormone (estrogen and progesterone) receptor (ER and PR) status at the time of breast carcinoma surgery is used as a marker for hormone dependency to guide adjuvant therapy. In a significant number of cases a discrepancy exists between the detected number of hormone receptors and the response to hormonal therapy. One of the explanations for this could be intratumoral heterogeneity. Our objective was to investigate the heterogeneity of steroid hormone receptor expression in breast cancer by using multiparameter flow cytometry (MP-FCM) on routinely processed formalin-fixed, paraffin-embedded tumors. A series of 232 routinely processed breast carcinomas were analyzed using a recently developed technique for the isolation of single cells from paraffin-embedded material. After dewaxing and rehydrating, 50-microm thick sections were heated for 2 hours at 80 degrees C in a citrate solution. Single-cell suspensions were prepared by a short pepsin digestion. The obtained single-cell suspensions were immunostained simultaneously for cytokeratin and ER or PR. Finally, DNA was stained using propidium iodide, after which the samples were analyzed on a flow cytometer. The fractions of ER- and PR-positive cells were determined in the total, as well as the G0 /G1 fraction of the diploid, and in case of nondiploid tumors, also in the G0 /G1 fraction of the aneuploid cell population. Of 232 cases, 88 (38%) were diploid, 38 (16%) were tetraploid, and 106 (46%) were aneuploid. In the diploid tumors the mean fraction of ER- and PR-positive cells was 81% and 76%, respectively. The ER- and PR-positive fractions in the total cytokeratin-positive fraction decreased significantly in the tetraploid (56% and 55%, respectively) and aneuploid tumors (both 47%, p < 0.0001). When analyzing the ER- and PR-positive fractions separately in the diploid and aneuploid cell populations of the nondiploid tumors, it became apparent that the ER and PR status in the diploid fraction of the tumor was significantly higher than in the aneuploid fraction (p < 0.0001). For the tetraploid tumors the mean ER- and PR-positive fractions were 79% and 76%, respectively, in the diploid fraction, and this decreased to 45% in the aneuploid cell subpopulation. In the aneuploid tumors this decrease was even more drastic: in the diploid cell population the ER- and PR-positive fractions were 66% and 62%, while this was 38% and 39% in the aneuploid population. These findings illustrate clearly the existence of a heterogeneous distribution of ER/PR expression in breast cancer, related to the loss of a diploid DNA index. Because of its objective quantification of subfractions within the same tumor, MP-FCM can be regarded as a superior method compared to more conventional techniques such as immunohistochemistry and biochemistry.

Over-diagnosis of hydatidiform mole in early tubal ectopic pregnancy

AIMS

Tubal ectopic hydatidiform moles are rare lesions, and only 40 cases have been reported in the world literature. We investigated the apparently high incidence of tubal ectopic hydatidiform moles in women referred for treatment to a Supraregional Trophoblastic Tumour Screening and Treatment Centre between 1986 and 1996.

METHODS AND RESULTS

Of 4261 women referred during the study period, 25 (0.6%) had a suspected tubal ectopic hydatidiform mole and paraffin-embedded tissue was available in 20 (80%) of these. Each case was reviewed by two pathologists and DNA flow cytometric analysis was undertaken when the histological diagnosis was initially deemed equivocal or suggestive of hydatidiform mole. On review, 17 cases (85%) showed no evidence of hydatidiform mole (circumferential trophoblastic proliferation, hydrops, scalloped villi, and stromal karyorrhexis). Of these, 11 cases (65%) showed features of early placentation and six (35%) showed hydropic abortion. DNA flow cytometry was performed in 14 (82%) of these cases and revealed a diploid population in each case. Three cases of molar pregnancy (15%) were identified. Each of these cases had the histological features of an early complete hydatidiform mole. Sufficient tissue was available for DNA flow cytometric analysis in two of these cases and confirmed the presence of diploidy in each.

CONCLUSION

Our results show that tubal ectopic hydatidiform mole is a rare entity and demonstrate that it is over-diagnosed. Polar trophoblastic proliferation and hydropic villi are features of early placentation and of hydropic abortion. Sheets of extravillous trophoblast may be particularly prominent in tubal ectopic gestation. In the absence of circumferential trophoblastic proliferation combined with hydropic change a diagnosis of gestational trophoblastic disease should be avoided.

A novel flow cytometric steroid hormone receptor assay for paraffin-embedded breast carcinomas: an objective quantification of the steroid hormone receptors and direct correlation to ploidy status and proliferative capacity in a single-tube assay

Semiquantitative estimation of steroid hormone receptors by immunohistochemistry applied to paraffin sections is common practice in surgical pathology. Flow cytometric (FCM) analysis of estrogen receptor (ER) and progesterone receptor (PR) levels provides a faster and more objective quantitative assay. However, a major problem in such FCM analyses of solid tumor samples is the admixture of tumor cells with normal epithelial, stromal, and inflammatory cells. The aim of the underlying study was to investigate the applicability of a recently developed multiparameter flow cytometric methodology for the accurate estimation of the fraction of steroid hormone receptor-positive tumor cells and to explore whether this multiparameter approach allows the detection of specific, clinically relevant subsets of tumors, based on a combination of ploidy level, steroid hormone receptor status, and cell cycle characteristics. For this purpose, samples of 42 breast cancer patients, from which routine immunohistochemistry for ER and PR also was available, were analyzed. From each case, a cell suspension was prepared from the paraffin block by applying a heating and short pepsin digestion step to 50-microm-thick sections. These cell suspensions were double-immunostained for cytokeratin to identify the epithelial cells, and ER or PR, whereas DNA was quantitatively stained with propidium iodide using an optimized protocol. In the entire group of breast tumors, the percentages of ER- and PR-positive cells were registered in the epithelial subfraction, in combination with DNA ploidy and S phase fraction (SPF). A significant correlation was found between the fraction of hormone receptor-positive cells as found by the immunohistochemical and FCM procedures. For ER, a correlation coefficient of r = .87 was found, and for PR r = .62, both P < .0001. It became clear that all the diploid breast tumors had more than 30% tumor cells positive for ER with a SPF lower than 10%, whereas aneuploid tumors contained on average a smaller percentage of steroid hormone receptor-positive cells, and simultaneously an SPF greater than 10%. Our results show that this multiparameter FCM analysis allows an objective and reproducible quantification of the fraction of steroid hormone receptor-positive cells in the relevant epithelial cell compartment in relation to DNA ploidy status and proliferative capacity in a single-tube assay.

Apoptosis, bcl-2 expression, and proliferation in benign and malignant endometrial epithelium: An approach using multiparameter flow cytometry

OBJECTIVE

Disturbances in the regulation of cell proliferation and differentiation play an important role in the formation of neoplastic lesions. Consequently, abnormalities in apoptosis regulation may contribute to this process. Expression of a neoepitope on cytokeratin 18, unmasked by an early caspase cleavage event and recognized by the novel monoclonal antibody M30, is an indicator of early epithelial cell apoptosis. The purpose of this study was to evaluate the quantitative relation among apoptosis (M30), cell persistence (bcl-2), and proliferation (S-phase fraction; SPF) in malignant and benign endometrium.

METHODS

Using multiparameter DNA flow cytometry on 54 formalin-fixed paraffin-embedded samples from benign (proliferative, secretory, inactive, and hyperplastic endometrium) and malignant (grades 1-3 endometrial adenocarcinoma) endometrial tissue, bcl-2 expression and M30 reactivity were assessed together with the SPF in the cytokeratin-positive epithelial cells.

RESULTS

Benign cyclic endometrium showed a relatively high bcl-2 expression and low M30 reactivity in the proliferative phase whereas in the secretory phase this relation was inverse. In endometrial hyperplasia the expression of bcl-2 was increased compared to that in secretory and postmenopausal endometrium, but still below the level of proliferative samples. The expression of M30 also increased compared to normal proliferative endometrium but did not reach the level of endometrium in the secretory phase of the menstrual cycle. In cancer the expression of bcl-2 decreased with the progression of differentiation grade. For M30 expression this relation was inverse. Overall there was a significant increase of M30 reactivity in cancerous compared to hyperplasia and normal cyclic endometrium.

CONCLUSION

Transition of endometrial epithelium from hyperplasia to cancer seems to involve both increased apoptosis and decreased bcl-2 expression. Flow cytometric evaluation of M30 and bcl-2 expression levels, with the SPF, in currettage specimens from postmenopausal patients complaining of bleeding provides a quantitative assessment of endometrial apoptosis, anti-apoptosis, and proliferation. Further studies are needed to determine the relationship among these three processes as indicators of the biological behavior of gynecological tumors.

Clonality assessment of lymphoproliferative disorders by multiparameter flow cytometry of paraffin-embedded tissue: an additional diagnostic tool in surgical pathology

A major drawback of immunohistochemical detection of monoclonality in B-cell lymphoproliferative disorders is the lack of contrast between surface-immunoglobulin staining and extracellular immunoglobulin staining. To bypass this drawback, immunophenotyping of single-cell suspensions by flow cytometry is commonly used. Although the expression of immunoglobulin light chain subtype can be quantified rapidly and reliably, the technique is hampered by the requirement of fresh unfixed material. We applied a recently developed technique for the isolation of single cells from formalin-fixed, paraffin-embedded material to measure clonality in B-cell lymphoproliferative disorders (lymphoid tissue (n = 10) and non-Hodgkin's B-cell lymphoma (n = 10). Immunocytochemistry indicated that common cell surface markers as well as the immunoglobulin light chains could be detected in the cell suspensions derived from archival material. In addition, the technique also allowed combined high-resolution DNA flow cytometric analysis. To investigate the effect of formalin fixation on cross-linking of extracellular immunoglobulins to lymphocytes, a double-immunostaining experiment for both light chain immunoglobulins (kappa and lambda) was performed. This experiment showed that this cross-linking was minimal (less than 2%). All cases of reactive lymphoid hyperplasia were DNA diploid and showed a polyclonal expression of immunoglobulin light chains. In contrast, in 9 of 10 non-Hodgkin's B-cell lymphomas, monoclonality was established on the basis of light chain expression, whereas only 6 of 9 cases were conclusive by immunohistochemistry. Four of the 9 cases were DNA aneuploid. One case did not show light chain expression at all by both techniques. However, this case could be classified as malignant by flow cytometric analysis because of the DNA-aneuploid nature of the B-cell subpopulation. The average S-phase fraction (SPF) of the B cells in the reactive lymphoid tissues was 3.5%. The mean SPF values for B cells in DNA-diploid cases of lymphomas was 3.0%, whereas the mean SPF of B cells in DNA-aneuploid cases was 6.1%. The presented technique is superior to immunohistochemistry for the detection of monoclonality in B-cell lymphoproliferative disorders and therefore provides a powerful tool to support the diagnosis of malignant lymphoma in routinely processed archival samples of lymphoid tissues.