Malic Enzyme 1 Absence in Synovial Sarcoma Shifts Antioxidant System Dependence and Increases Sensitivity to Ferroptosis Induction with ACXT-3102.

PURPOSE: To investigate the metabolism of synovial sarcoma (SS) and elucidate the effect of malic enzyme 1 absence on SS redox homeostasis. EXPERIMENTAL DESIGN: ME1 expression was measured in SS clinical samples, SS cell lines, and tumors from an SS mouse model. The effect of ME1 absence on glucose metabolism was evaluated utilizing Seahorse assays, metabolomics, and C13 tracings. The impact of ME1 absence on SS redox homeostasis was evaluated by metabolomics, cell death assays with inhibitors of antioxidant systems, and measurements of intracellular reactive oxygen species (ROS). The susceptibility of ME1-null SS to ferroptosis induction was interrogated in vitro and in vivo. RESULTS: ME1 absence in SS was confirmed in clinical samples, SS cell lines, and an SS tumor model. Investigation of SS glucose metabolism revealed that ME1-null cells exhibit higher rates of glycolysis and higher flux of glucose into the pentose phosphate pathway (PPP), which is necessary to produce NADPH. Evaluation of cellular redox homeostasis demonstrated that ME1 absence shifts dependence from the glutathione system to the thioredoxin system. Concomitantly, ME1 absence drives the accumulation of ROS and labile iron. ROS and iron accumulation enhances the susceptibility of ME1-null cells to ferroptosis induction with inhibitors of xCT (erastin and ACXT-3102). In vivo xenograft models of ME1-null SS demonstrate significantly increased tumor response to ACXT-3102 compared with ME1-expressing controls. CONCLUSIONS: These findings demonstrate the translational potential of targeting redox homeostasis in ME1-null cancers and establish the preclinical rationale for a phase I trial of ACXT-3102 in SS patients. See related commentary by Subbiah and Gan, p. 3408.

Death by HDAC Inhibition in Synovial Sarcoma Cells.

Conventional cytotoxic therapies for synovial sarcoma provide limited benefit, and no drugs specifically targeting the causative SS18-SSX fusion oncoprotein are currently available. Histone deacetylase (HDAC) inhibition has been shown in previous studies to disrupt the synovial sarcoma oncoprotein complex, resulting in apoptosis. To understand the molecular effects of HDAC inhibition, RNA-seq transcriptome analysis was undertaken in six human synovial sarcoma cell lines. HDAC inhibition induced pathways of cell-cycle arrest, neuronal differentiation, and response to oxygen-containing species, effects also observed in other cancers treated with this class of drugs. More specific to synovial sarcoma, polycomb group targets were reactivated, including tumor suppressor CDKN2A, and proapoptotic transcriptional patterns were induced. Functional analyses revealed that ROS-mediated FOXO activation and proapoptotic factors BIK, BIM, and BMF were important to apoptosis induction following HDAC inhibition in synovial sarcoma. HDAC inhibitor pathway activation results in apoptosis and decreased tumor burden following a 7-day quisinostat treatment in the Ptenfl/fl;hSS2 mouse model of synovial sarcoma. This study provides mechanistic support for a particular susceptibility of synovial sarcoma to HDAC inhibition as a means of clinical treatment. Mol Cancer Ther; 16(12); 2656-67. ©2017 AACR.

HDAC and Proteasome Inhibitors Synergize to Activate Pro-Apoptotic Factors in Synovial Sarcoma.

Conventional cytotoxic therapies for synovial sarcoma provide limited benefit, and no drugs specifically targeting its driving SS18-SSX fusion oncoprotein are currently available. Patients remain at high risk for early and late metastasis. A high-throughput drug screen consisting of over 900 tool compounds and epigenetic modifiers, representing over 100 drug classes, was undertaken in a panel of synovial sarcoma cell lines to uncover novel sensitizing agents and targetable pathways. Top scoring drug categories were found to be HDAC inhibitors and proteasomal targeting agents. We find that the HDAC inhibitor quisinostat disrupts the SS18-SSX driving protein complex, thereby reestablishing expression of EGR1 and CDKN2A tumor suppressors. In combination with proteasome inhibition, HDAC inhibitors synergize to decrease cell viability and elicit apoptosis. Quisinostat inhibits aggresome formation in response to proteasome inhibition, and combination treatment leads to elevated endoplasmic reticulum stress, activation of pro-apoptotic effector proteins BIM and BIK, phosphorylation of BCL-2, increased levels of reactive oxygen species, and suppression of tumor growth in a murine model of synovial sarcoma. This study identifies and provides mechanistic support for a particular susceptibility of synovial sarcoma to the combination of quisinostat and proteasome inhibition.

New Strategies in Sarcoma: Linking Genomic and Immunotherapy Approaches to Molecular Subtype.

There are more than 100 sarcoma subtypes, each uncommon and diagnostically challenging. Conventional chemotherapy has little benefit for most soft-tissue sarcomas; new treatment strategies are needed. Multiple recent genomic studies have provided detailed insights into sarcoma biology, including more accurate classification by molecular subtype, identification of recurrent mutations in oncogenic pathways, and evidence of epigenetic dysregulation. Advances in immunotherapy (adoptive immune cell transfer, tumor vaccine strategies, and immune checkpoint inhibition) have also provided a better understanding of how immuno-oncology might best be applied to sarcoma treatment, including connections to oncogenic pathways that may support combination strategies with conventional and targeted therapies. In this article, we review the latest sarcoma genomic studies and immuno-oncology developments and discuss how the findings suggest potential strategies to improve diagnosis and treatment across multiple sarcoma subtypes.

Synovial sarcoma: recent discoveries as a roadmap to new avenues for therapy.

UNLABELLED: Oncogenesis in synovial sarcoma is driven by the chromosomal translocation t(X,18; p11,q11), which generates an in-frame fusion of the SWI/SNF subunit SS18 to the C-terminal repression domains of SSX1 or SSX2. Proteomic studies have identified an integral role of SS18-SSX in the SWI/SNF complex, and provide new evidence for mistargeting of polycomb repression in synovial sarcoma. Two recent in vivo studies are highlighted, providing additional support for the importance of WNT signaling in synovial sarcoma: One used a conditional mouse model in which knockout of ß-catenin prevents tumor formation, and the other used a small-molecule inhibitor of ß-catenin in xenograft models. SIGNIFICANCE: Synovial sarcoma appears to arise from still poorly characterized immature mesenchymal progenitor cells through the action of its primary oncogenic driver, the SS18-SSX fusion gene, which encodes a multifaceted disruptor of epigenetic control. The effects of SS18-SSX on polycomb-mediated gene repression and SWI/SNF chromatin remodeling have recently come into focus and may offer new insights into the basic function of these processes. A central role for deregulation of WNT-ß-catenin signaling in synovial sarcoma has also been strengthened by recent in vivo studies. These new insights into the the biology of synovial sarcoma are guiding novel preclinical and clinical studies in this aggressive cancer.

Deconstruction of the SS18-SSX fusion oncoprotein complex: insights into disease etiology and therapeutics.

Synovial sarcoma is a translocation-associated sarcoma where the underlying chromosomal event generates SS18-SSX fusion transcripts. In vitro and in vivo studies have shown that the SS18-SSX fusion oncoprotein is both necessary and sufficient to support tumorigenesis; however, its mechanism of action remains poorly defined. We have purified a core SS18-SSX complex and discovered that SS18-SSX serves as a bridge between activating transcription factor 2 (ATF2) and transducin-like enhancer of split 1 (TLE1), resulting in repression of ATF2 target genes. Disruption of these components by siRNA knockdown or treatment with HDAC inhibitors rescues target gene expression, leading to growth suppression and apoptosis. Together, these studies define a fundamental role for aberrant ATF2 transcriptional dysregulation in the etiology of synovial sarcoma.

Validation of immature adipogenic status and identification of prognostic biomarkers in myxoid liposarcoma using tissue microarrays.

Myxoid liposarcoma displays variably aggressive behavior and responds poorly to available systemic therapies. Expression profiling followed by tissue microarray validation linked to patient outcome is a powerful approach for validating biological mechanisms and identifying prognostic biomarkers. We applied these techniques to independent series of primary myxoid liposarcomas in an effort to assess markers of adipose differentiation in myxoid liposarcoma and to identify prognostic markers that can be efficiently assessed by immunohistochemistry. Candidate genes were selected based on analysis of expression profiles from 9 primary myxoid/round liposarcomas and 45 other soft tissue tumors, and by reference to publicly available data sets. Protein products were validated on an adipose neoplasm tissue microarray, including 32 myxoid liposarcomas linked to patient outcome. Results were scored visually and correlated with clinical outcome by Kaplan-Meier and Cox regression analyses. In the study, by examining expression patterns of several lipogenic regulatory gene products, an immature adipogenic status was verified in myxoid liposarcomas. We also found that expression levels of the ret proto-oncogene, insulin-like growth factor 1 receptor, and insulin-like growth factor 2 correlate with poor metastasis-free survival, supporting a role for ERK/MAPK and PI3K/AKT pathways in clinically aggressive myxoid liposarcomas.

Synergism of heat shock protein 90 and histone deacetylase inhibitors in synovial sarcoma.

Current systemic therapies have little curative benefit for synovial sarcoma. Histone deacetylase (HDAC) inhibitors and the heat shock protein 90 (Hsp90) inhibitor 17-AAG have recently been shown to inhibit synovial sarcoma in preclinical models. We tested combinations of 17-AAG with the HDAC inhibitor MS-275 for synergism by proliferation and apoptosis assays. The combination was found to be synergistic at multiple time points in two synovial sarcoma cell lines. Previous studies have shown that HDAC inhibitors not only induce cell death but also activate the survival pathway NF-kappaB, potentially limiting therapeutic benefit. As 17-AAG inhibits activators of NF-kappaB, we tested if 17-AAG synergizes with MS-275 through abrogating NF-kappaB activation. In our assays, adding 17-AAG blocks NF-kappaB activation by MS-275 and siRNA directed against histone deacetylase 3 (HDAC3) recapitulates the effects of MS-275. Additionally, we find that the NF-kappaB inhibitor BAY 11-7085 synergizes with MS-275. We conclude that agents inhibiting NF-kappaB synergize with HDAC inhibitors against synovial sarcoma.

Histone deacetylase inhibitors reverse SS18-SSX-mediated polycomb silencing of the tumor suppressor early growth response 1 in synovial sarcoma.

Synovial sarcoma is a soft tissue malignancy characterized by the fusion of SS18 to either SSX1, SSX2, or SSX4 genes. SS18 and SSX are transcriptional cofactors involved in activation and repression of gene transcription, respectively. SS18 interacts with SWI/SNF, whereas SSX associates with the polycomb chromatin remodeling complex. Thus, fusion of these two proteins brings together two opposing effects on gene expression and chromatin structure. Recent studies have shown that a significant number of genes are down-regulated by the SS18-SSX fusion protein and that the clinically applicable histone deacetylase (HDAC) inhibitor romidepsin inhibits synovial sarcoma growth. Therefore, we set out to identify direct targets of SS18-SSX among genes down-regulated in synovial sarcoma and investigated if romidepsin can specifically counteract SS18-SSX-mediated transcriptional dysregulation. Here, we report that the tumor suppressor early growth response 1 (EGR1) is repressed by the SS18-SSX protein through a direct association with the EGR1 promoter. This SS18-SSX binding correlates with trimethylation of Lys(27) of histone H3 (H3K27-M3) and recruitment of polycomb group proteins to this promoter. In addition, we found that romidepsin treatment reverts these modifications and reactivates EGR1 expression in synovial sarcoma cell models. Our data implicate polycomb-mediated epigenetic gene repression as a mechanism of oncogenesis in synovial sarcoma. Furthermore, our work highlights a possible mechanism behind the efficacy of a clinically applicable HDAC inhibitor in synovial sarcoma treatment.

Prognostic significance of macrophage infiltration in leiomyosarcomas.

PURPOSE: Macrophages are migratory cells that are frequently recruited to the site of tumors. Their presence is associated with poor clinical outcome in a variety of epithelial malignancies. The aim of this study is to examine the prognostic significance of tumor-associated macrophages in sarcomas. EXPERIMENTAL DESIGN: Global gene expression profiling data of a series of soft tissue tumors were analyzed for macrophage-associated gene expression. Immunohistochemistry on tissue microarrays containing leiomyosarcoma cases with known clinical outcome was used to verify the presence of macrophages and to examine the relationship between tumor-associated macrophages and clinical outcome. RESULTS: Gene expression profiling revealed high-level expression of several macrophage-associated genes such as CD163 and CD68 in a subset of leiomyosarcomas, indicating the presence of variable numbers of tumor-infiltrating macrophages. This was confirmed by CD68 and CD163 immunostaining of a tissue microarray containing 149 primary leiomyosarcomas. Kaplan-Meier survival analysis showed that high density of tumor-infiltrating macrophages as identified by CD163 or CD68 staining is associated with a significantly worse disease-specific survival in nongynecologic leiomyosarcomas, whereas leiomyosarcomas arising from the gynecologic tract showed no significant association between macrophage infiltration and survival. The presence of tumor necrosis did not correlate significantly with outcome. CONCLUSIONS: An increased density of CD163- or CD68-positive tumor-infiltrating macrophages is associated with poor outcome in nongynecologic leiomyosarcomas. This may help the clinical management of patients with leiomyosarcomas.

Discrimination between benign and malignant prostate tissue using chromatin texture analysis in 3-D by confocal laser scanning microscopy.

BACKGROUND: Analysis of chromatin texture may improve both the diagnosis and the assessment of the prognosis of prostate cancer. Confocal laser scanning microscopy (CLSM) allows performing measurements in nuclei reconstructed in 3-D. The aim of this study was to evaluate the clinical usefulness of 3-D texture analysis of prostate tissue. METHODS: Image stacks of eight prostate cancer sections were obtained by CLSM of both benign and malignant areas. Texture feature values were computed for individual nuclei. The discriminative power of the texture features was established by receiver operating characteristic (ROC) analysis and linear discriminant analysis (LDA). RESULTS: Texture features were identified that could discriminate between benign and malignant nuclei. LDA correctly classified 89% of the nuclei of the pooled set of benign and malignant nuclei. CONCLUSIONS: 3-D nuclear texture features allow discrimination of most benign and malignant prostate nuclei. We estimate that the classification rates can be increased by improving the image quality.

Development of 3D chromatin texture analysis using confocal laser scanning microscopy.

INTRODUCTION: Analysis of nuclear texture features as a measure of nuclear chromatin changes has been proven to be useful when measured on thin (5-6 microm) tissue sections using conventional 2D bright field microscopy. The drawback of this approach is that most nuclei are not intact because of those thin sections. Confocal laser scanning microscopy (CLSM) allows measurements of texture in 3D reconstructed nuclei. The aim of this study was to develop 3D texture features that quantitatively describe changes in chromatin architecture associated with malignancy using CLSM images. METHODS: Thirty-five features thoughtfully chosen from 4 categories of 3D texture features (discrete texture features, Markovian features, fractal features, grey value distribution features) were selected and tested for invariance properties (rotation and scaling) using artificial images with a known grey value distribution. The discriminative power of the 3D texture features was tested on artificially constructed benign and malignant 3D nuclei with increasing nucleolar size and advancing chromatin margination towards the periphery of the nucleus. As a clinical proof of principle, the discriminative power of the texture features was assessed on 10 benign and 10 malignant human prostate nuclei, evaluating also whether there was more texture information in 3D whole nuclei compared to a single 2D plane from the middle of the nucleus. RESULTS: All texture features showed the expected invariance properties. Almost all features were sensitive to variations in the nucleolar size and to the degree of margination of chromatin. Fourteen texture features from different categories had high discriminative power for separating the benign and malignant nuclei. The discrete texture features performed less than expected. There was more information on nuclear texture in 3D than in 2D. CONCLUSION: A set of 35 3D nuclear texture features was used successfully to assess nuclear chromatin patterns in 3D images obtained by confocal laser scanning microscopy, and as a proof of principle we showed that these features may be clinically useful for analysis of prostate neoplasia.

Implementation of accurate and fast DNA cytometry by confocal microscopy in 3D.

BACKGROUND: DNA cytometry is a powerful method for measuring genomic instability. Standard approaches that measure DNA content of isolated cells may induce selection bias and do not allow interpretation of genomic instability in the context of the tissue. Confocal Laser Scanning Microscopy (CLSM) provides the opportunity to perform 3D DNA content measurements on intact cells in thick histological sections. Because the technique is technically challenging and time consuming, only a small number of usually manually selected nuclei were analyzed in different studies, not allowing wide clinical evaluation. The aim of this study was to describe the conditions for accurate and fast 3D CLSM cytometry with a minimum of user interaction to arrive at sufficient throughput for pilot clinical applications. METHODS: Nuclear DNA was stained in 14 microm thick tissue sections of normal liver and adrenal stained with either YOYO-1 iodide or TO-PRO-3 iodide. Different pre-treatment strategies were evaluated: boiling in citrate buffer (pH 6.0) followed by RNase application for 1 or 18 hours, or hydrolysis. The image stacks obtained with CLSM at microscope magnifications of x40 or x100 were analyzed off-line using in-house developed software for semi-automated 3D fluorescence quantitation. To avoid sectioned nuclei, the top and bottom of the stacks were identified from ZX and YZ projections. As a measure of histogram quality, the coefficient of variation (CV) of the diploid peak was assessed. RESULTS: The lowest CV (10.3%) was achieved with a protocol without boiling, with 1 hour RNase treatment and TO-PRO-3 iodide staining, and a final image recording at x60 or x100 magnifications. A sample size of 300 nuclei was generally achievable. By filtering the set of automatically segmented nuclei based on volume, size and shape, followed by interactive removal of the few remaining faulty objects, a single measurement was completely analyzed in approximately 3 hours. CONCLUSIONS: The described methodology allows to obtain a largely unbiased sample of nuclei in thick tissue sections using 3D DNA cytometry by confocal laser scanning microscopy within an acceptable time frame for pilot clinical applications, and with a CV small enough to resolve smaller near diploid stemlines. This provides a suitable method for 3D DNA ploidy assessment of selected rare cells based on morphologic characteristics and of clinical samples that are too small to prepare adequate cell suspensions.

Subvisual chromatin changes in cervical epithelium measured by texture image analysis and correlated with HPV.

OBJECTIVES: In this study, we are testing the hypothesis that human papillomavirus (HPV) positivity is correlated with chromatin texture in the cell. Interim analyses are important since this study involves 2000 patients and generates 6000 biopsy specimens that will be subjected to quantitative histopathological analysis and correlated to HPV positivity as measured by the Hybrid Capture II test (Digene; Gaithersberg, MD) and both HPV-DNA and mRNA by the polymerase chain reaction (PCR). The studies of optical technologies, from which we derive this sample, use the colposcopically directed and histopathologically classified cervical biopsy as the gold standard. In this report, we describe the results of an interim analysis of quantitative histopathology and chromatin texture as correlates of HPV infection using the cyto-savant system in cytologically and histopathologically negative specimens. METHODS: A group of 1544 patients entered the optical technology trials, generating 3275 biopsies and 1544 Papanicolaou readings. Two hundred forty-eight patients were cytologically and histopathologically negative. Study pathologists reviewed histologic samples 3 times in a blinded fashion. Non-overlapping, quantitatively stained nuclei were selected from the samples by the pathologists. HPV testing was done using the PCR method and the Hybrid Capture II test. Statistical analysis involved the creation of a classification matrix using a linear discriminant analysis. The matrix was trained on HPV-positive cells by PCR. The analysis included the random creation of both a training set and a validation set that were classified based on the discrimination score obtained by correlating nuclear texture with HPV positivity. RESULTS: The sensitivity of the classification was 52-54% and the specificity was 77-78%. Overall, a 68% predicted accuracy was achieved for both the training set and the test set. The agreement of a test and training set shows that the sets created randomly are indeed similar, and that the discrimination score worked equally well in both sets of cells. Once a cell-by-cell algorithm for HPV positivity was derived, HPV positivity was recalculated on the basis of cell-by-cell texture features. HPV positivity was then recalculated on both a per-biopsy basis and a per-patient basis. For HPV 16 and 18, the positivity rate was 70% on a per-biopsy basis and 73% on a per-patient basis. CONCLUSIONS: Although these results are preliminary, they suggest that texture features reflecting chromatin condensation may correlate with HPV positivity. The current sample is histologic, the analysis suggests that in a cytologic sample, HPV positivity could be detected or confirmed by texture features computed as part of an HPV-associated score. Additional biologic markers could be used as needed. While this study was performed on histologic samples, a study of cytologic samples would be more useful. Future studies will examine chromatin texture compared to HPV integration and mRNA HPV expression.

Kappa statistics to measure interrater and intrarater agreement for 1790 cervical biopsy specimens among twelve pathologists: qualitative histopathologic analysis and methodologic issues.

BACKGROUND: As part of a program project to evaluate emerging optical technologies for cervical neoplasia, we performed fluorescence and reflectance spectroscopic examinations of patients with abnormal Papanicolaou smears. Biopsy specimens were taken from each area and measured optically, and study pathologists performed qualitative histopathologic readings. Several methodologic issues arose in this analysis: (1) the interpathologist and intrapathologist agreement between institutions for the 1790 biopsy specimens; (2) the interinstitutional agreement among the two institutions conducting the trials on 117 randomly chosen biopsy specimens; (3) the interinstitutional agreement among the two institutions and a third expert gynecologic pathologist to ensure the expert readings were comparable to those outside both institutions on 117 randomly chosen biopsy specimens; and (4) an additional three reviews of the 106 difficult biopsy specimens by all three institutions. METHODS: All 1790 specimens from 850 patients were reviewed three times at each institution in blinded fashion; those for which the first and second reviews were identical were not reviewed a third time. A randomly selected sample of 117 specimens was randomly ordered and read by study pathologists at The University of Texas M. D. Anderson Cancer Center, British Columbia Cancer Agency (BCCA), and Brigham and Women's Hospital (BWH). The 106 difficult cases were treated in the same manner as the randomized and random-ordered cases. Generalized, unweighted, and weighted kappas and their 95% confidence intervals were used to assess agreement. Binary comparisons were used to compare diagnostic categories. FINDINGS: The kappas for the three readings of the overall data set using eight-category World Health Organization (WHO) criteria were as follows: 0.66 for the generalized, 0.72 for weighted, and ranged from 0.59 to 0.94 unweighted binary categories; those read using four-category Bethesda criteria: 0.70 for generalized, 0.69 for weighted, and 0.56-0.94 for unweighted binary categories. For the pool versus the study pathologist readings, the eight-category kappa was 0.51 for generalized, 0.72 for weighted, and 0.56-0.82 for unweighted binary categories; for those read using Bethesda criteria: 0.70 for generalized, 0.70 for weighted, and 0.59-0.82 for the unweighted binary categories. The interpathologist and intrapathologist readings were fair by Landis standards at the low end of the diagnostic scale (atypia, human papillomavirus, and CIN1) and substantial to almost perfect at the high end (CIN2, CIN3, and CIS). The randomly selected and randomly ordered sample of 117 specimens read with the WHO system yielded a generalized kappa of 0.45; among the three institutions (M. D. Anderson Cancer Center vs. BCCA, M. D. Anderson vs. BWH, and BCCA vs. BWH), the unweighted kappas were 0.46, 0.41, and 0.49 and the weighted were 0.65, 0.66, and 0.68, respectively; for the Bethesda, a generalized kappa of 0.65, unweighted kappas of 0.66, 0.65, and 0.47, and weighted of 0.74, 0.72, and 0.74. The difficult specimens read with the WHO system yielded a generalized kappa of 0.23; among the three institutions the unweighted kappas were 0.20, 0.30, and 0.37, and the weighted were 0.17, 0.34, and 0.31; for the Bethesda, a generalized kappa of 0.25; among the three institutions, the unweighted kappas were 0.21, 0.32, and 0.37, and the weighted were: 0.07, 0.21, and 0.37, respectively. INTERPRETATION: Kappas in this expert group of pathologists were in the moderate, substantial, and almost perfect ranges for the overall and randomized samples. The randomized sample was representative of the larger sample. The kappa of the specimens for which disagreements arose was, predictably, in the slight range. Our findings will aid both the correlations with optical measurements using fluorescence and reflectance spectroscopy and the quantitative histopathologic analysis of these study specimens.

Confocal 3D DNA cytometry: assessment of required coefficient of variation by computer simulation.

BACKGROUND: Confocal Laser Scanning Microscopy (CLSM) provides the opportunity to perform 3D DNA content measurements on intact cells in thick histological sections. So far, sample size has been limited by the time consuming nature of the technology. Since the power of DNA histograms to resolve different stemlines depends on both the sample size and the coefficient of variation (CV) of histogram peaks, interpretation of 3D CLSM DNA histograms might be hampered by both a small sample size and a large CV. The aim of this study was to analyze the required CV for 3D CLSM DNA histograms given a realistic sample size. METHODS: By computer simulation, virtual histograms were composed for sample sizes of 20000, 10000, 5000, 1000, and 273 cells and CVs of 30, 25, 20, 15, 10 and 5%. By visual inspection, the histogram quality with respect to resolution of G0/1 and G2/M peaks of a diploid stemline was assessed. RESULTS: As expected, the interpretability of DNA histograms deteriorated with decreasing sample sizes and higher CVs. For CVs of 15% and lower, a clearly bimodal peak pattern with well distinguishable G0/1 and G2/M peaks were still seen at a sample size of 273 cells, which is our current average sample size with 3D CLSM DNA cytometry. CONCLUSIONS: For unambiguous interpretation of DNA histograms obtained using 3D CLSM, a CV of at most 15% is tolerable at currently achievable sample sizes. To resolve smaller near diploid stemlines, a CV of 10% or better should be aimed at. With currently available 3D imaging technology, this CV is achievable.

Quantitative histopathological analysis of cervical intra-epithelial neoplasia sections: methodological issues.

OBJECTIVES: As part a Program Project to evaluate emerging optical technologies for cervical neoplasia, our group is performing quantitative histopathological analysis of biopsies from 1,800 patients. Several methodological issues have arisen with respect to this analysis: (1) Finding the most efficient way to compensate for staining intensity variation with out losing diagnostic information; (2) Assessing the inter- and intra-observer variability of the semi-interactive data collection; and (3) the use of non-overlapping cells from the intermediate layer only. METHODS: Non-overlapping quantitatively stained nuclei were selected from 280 samples with histopathological characteristics of normal (199), koilocytosis (37), CIN 1 (18), CIN 2 (10) and CIN 3 (16). Linear discriminant analysis was used to assess the diagnostic information in three different feature sets to evaluate and compare staining intensity normalization methods. Selected feature values and summary scores were used to evaluate intra- and inter-observer variability. RESULTS: The features normalized by the internal subset of the imaged cells had the same discriminatory power as those normalized by the control cells and by both normalization methods seem to have additional discriminatory power over the set of features which do not require normalization. The use of the internal subset decreased the image acquisition time by approximately 50% at each center, respectively. The intra- and inter-observer variability was of a similar size. Good performance was obtained by measuring the intermediate layer only. CONCLUSION: The use of intensity normalization from a subset of the imaged non-overlapping intermediate layer cells works as well as or better than any of the other methods tested and provides a significant timesaving. Our intra- and inter-observer variability do not seem to affect the diagnostic power of the data. Although this must be tested in a larger data set, the use of intermediate layer cells only may be acceptable when using quantitative histopathology.

Exploratory analysis of quantitative histopathology of cervical intraepithelial neoplasia: objectivity, reproducibility, malignancy-associated changes, and human papillomavirus.

BACKGROUND: As part of a project to evaluate emerging optical technologies for cervical neoplasia, our group is performing quantitative histopathological analyses of biopsy specimens from 1,190 patients. Objectives in the interim analysis are (a) quantitatively assessing progression of the neoplastic process of cervical intraepithelial neoplasia (CIN)/squamous intraepithelial lesions (SIL), (b) detecting malignancy-associated changes (MACs), and (c) phenotypically measuring human papillomavirus (HPV) detected by DNA testing. METHODS: The diagnostic region of interest (ROI) from immediately adjacent sections were imaged, and the basal lamina and surface of the superficial layer were delimited. Nonoverlapping quantitatively stained nuclei were selected from 1,190 samples with histopathological characteristics of normal (929), koilocytosis (130), CIN 1 (40), CIN 2 (23), and CIN 3/carcinoma in situ (CIS) (68). A fully automatic procedure located and recorded the center of every nucleus in the region of interest (ROI). We used linear discriminant analysis to assess the changes between normal and CIN 3/CIS. RESULTS: Scores computed from the cell-by cell features and the clinical grade of CIN/SIL were highly correlated, as were those of the architectural features and the clinical grade of CIN/SIL. We found even higher correlations between a combination of cell-by-cell and architectural scores, and clinical grade. Using these scores, we found MACs in the normal biopsy specimens from patients with high-grade CIN/SIL. Furthermore, the same scores correlated with the molecular detection of HPV. CONCLUSIONS: Quantitative histopathology can be used in large clinical trials as an objective and reproducible measure of CIN/SIL. Detectable phenotypic changes correlate well with CIN/SIL neoplastic progression. It can also be used to infer the presence of CIN/SIL (MACs) and molecular changes associated with increased risk of cancer development (high-risk HPV).

Confocal DNA cytometry: a contour-based segmentation algorithm for automated three-dimensional image segmentation.

BACKGROUND: Confocal laser scanning microscopy (CLSM) presents the opportunity to perform three-dimensional (3D) DNA content measurements on intact cells in thick histological sections. So far, these measurements have been performed manually, which is quite time-consuming. METHODS: In this study, an intuitive contour-based segmentation algorithm for automatic 3D CLSM image cytometry of nuclei in thick histological sections is presented. To evaluate the segmentation algorithm, we measured the DNA content and volume of human liver and breast cancer nuclei in 3D CLSM images. RESULTS: A high percentage of nuclei could be segmented fully automatically (e.g., human liver, 92%). Comparison with (time-consuming) interactive measurements on the same CLSM images showed that the results were well correlated (liver, r = 1.00; breast, r = 0.92). CONCLUSIONS: Automatic 3D CLSM image cytometry enables measurement of volume and DNA content of large numbers of nuclei in thick histological sections within an acceptable time. This makes large-scale studies feasible, whereby the advantages of CLSM can be exploited fully. The intuitive modular segmentation algorithm presented in this study detects and separates overlapping objects, also in two-dimensional (2D) space. Therefore, this algorithm may also be suitable for other applications.