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Real-time PCR quantification of c-erbB-2 gene is an alternative for FISH in the clinical management of breast carcinoma patients.

Evaluation of gene amplification and protein expression of the c-erbB-2/neu in breast carcinomas has been an important task in breast cancer management. Although immunohistochemistry is widely applied, fluorescence in situ hybridization (FISH) technology shows its advantage in discriminating tumors in an objective manner. More recently, development of LightCycler technology permits evaluation of gene amplification with a small volume of DNA run in a 20 microL glass capillary. In this study, a series of 87 breast carcinomas were chosen for evaluation of c-erbB-2/neu gene amplification detected by both LightCycler technology and FISH. Real-time polymerase chain reaction (PCR) was performed in LightCycler capillaries with 10 ng sample DNA. By using LightCycler Relative Quantification Software version 1 (LightCycler, Roche, Mannheim, Germany), the amount of c-erbB-2 DNA was calculated as a ratio of c-erbB-2/reference gene quantity in a sample, and then the ratio was divided by the ratio of c-erbB-2 gene/reference gene quantities of a calibrator DNA (a standard DNA provided in the kit), which was run with each sample reaction in parallel. Dual-color FISH was performed on sections of the formalin-fixed, paraffin-embedded tissue array samples using the DAKO HER2 FISH pharmDX kit (DAKO A/S, Glostrup, Danmark) according to the manufacturer's instructions. Furthermore, immunohistochemistry was performed in parallel, with both the NCL-CB11 and HercepTest antibodies. Both the FISH technology and the LightCycler-PCR identified a similar percentage of tumors with c-erbB-2 gene amplification in our present study, 16% (14/87) and 15% (13/87), respectively, whereas immunohistochemistry demonstrated 32% and 34% c-erbB-2 overexpression with the NCL-CB11 and HercepTest antibodies, respectively. In addition, FISH and PCR were highly correlated in detecting tumors mainly with 3+++ c-erbB-2 protein expression by immunohistochemistry, indicating that LightCycler real-time quantification of c-erbB-2 gene may be an alternative to FISH in breast cancer clinical application.

Biomarkers, Tumor↗

Simulation modeling of pooling for combinatorial protein engineering.

Pooling in directed-evolution experiments will greatly increase the throughput of screening systems, but important parameters such as the number of good mutants created and the activity level increase of the good mutants will depend highly on the protein being engineered. The authors developed and validated a Monte Carlo simulation model of pooling that allows the testing of various scenarios in silico before starting experimentation. Using a simplified test system of 2 enzymes, betagalactosidase (supermutant, or greatly improved enzyme) and beta-glucuronidase (dud, or enzyme with ancestral level of activity), the model accurately predicted the number of supermutants detected in experiments within a factor of 2. Additional simulations using more complex activity distributions show the versatility of the model. Pooling is most suited to cases such as the directed evolution of new function in a protein, where the background level of activity is minimized, making it easier to detect small increases in activity level. Pooling is most successful when a sensitive assay is employed. Using the model will increase the throughput of screening procedures for directed-evolution experiments and thus lead to speedier engineering of proteins.

Cells, Cultured↗

A cell-based ultra-high-throughput screening assay for identifying inhibitors of D-amino acid oxidase.

Enzymes are often considered less "druggable" targets than ligand-regulated proteins such as G-protein-coupled receptors, ion channels, or other hormone receptors. Reasons for this include cellular location (intracellular vs. cell surface), typically lower affinities for the binding of small molecules compared to ligand-specific receptors, and binding (catalytic) sites that are often charged or highly polar. A practical drawback to the discovery of compounds targeting enzymes is that screening of compound libraries is typically carried out in cell-free activity assays using purified protein in an inherently artificial environment. Cell-based assays, although often arduous to design for enzyme targets, are the preferred discovery tool for the screening of large compound libraries. The authors have recently described a novel cell-based approach to screening for inhibitors of a phosphatase enzyme and now report on the development and implementation of a homogeneous 3456-well plate assay for D-amino acid oxidase (DAO). Human DAO was stably expressed in Chinese hamster ovary (CHO) cells, and its activity was measured as the amount of hydrogen peroxide detected in the growth medium following feeding the cells with D-serine. In less than 12 weeks, the authors proved the concept in 96-and then 384-well formats, miniaturized the assay to the 3456-well (nanoplate) scale, and screened a library containing more than 1 million compounds. They have identified several cell-permeable inhibitors of DAO from this cell-based high-throughput screening, which provided the discovery program with a few novel and attractive lead structures.

Animals↗

Overexpression of IGFBP5, but not IGFBP3, correlates with the histologic grade of human diffuse glioma: a tissue microarray and immunohistochemical study.

Insulin-like growth factor binding proteins (IGFBPs) comprise a family of proteins that bind and regulate the functions of IGFs. One of the IGFBPs, IGFBP2, has recently been shown to be overexpressed in glioblastoma. Overexpression of IGFBP2 contributes to the invasiveness of glioblastoma and correlates with histologic grade and survival in patients with diffuse gliomas, suggesting that IGFBP2 expression may contribute to the glioma formation and/or progression. The expression of other IGFBP family members in gliomas has, however, not been examined in detail. This study was designed to evaluate the expression of IGFBP3 and IGFBP5 in diffuse gliomas using immunohistochemistry applied to a tissue array constructed from 259 gliomas, including ten gliosarcomas. Expression of IGFBP5 correlated significantly with glioma histologic grade. 83% (58/70) of glioblastomas (WHO Grade IV) were positive for IGFBP5, which was significantly higher than WHO Grade III gliomas (41%, 41/101) or WHO Grade II gliomas (18%, 13/72) (p<0.001). In contrast, IGFBP3 was expressed in 17%, 23%, and 17% of WHO Grade IV, Grade III, and Grade II gliomas, respectively (p>0.05). There was no significant difference in IGFBP3 expression among different grades of glioma. Our study thus demonstrates that the expression of IGFBP5, but not IGFBP3, increases with glioma anaplastic progression. The strong correlation between overexpression of IGFBP5 and histologic grade suggests that, in addition to IGFBP2, IGFBP5 may also play a role in glioma progression.

Biomarkers, Tumor↗

The FU gene and its possible protein isoforms.

BACKGROUND: FU is the human homologue of the Drosophila gene fused whose product fused is a positive regulator of the transcription factor Cubitus interruptus (Ci). Thus, FU may act as a regulator of the human counterparts of Ci, the GLI transcription factors. Since Ci and GLI are targets of Hedgehog signaling in development and morphogenesis, it is expected that FU plays an important role in Sonic, Desert and/or Indian Hedgehog induced cellular signaling. RESULTS: The FU gene was identified on chromosome 2q35 at 217.56 Mb and its exon-intron organization determined. The human developmental disorder Syndactyly type 1 (SD1) maps to this region on chromosome 2 and the FU coding region was sequenced using genomic DNA from an affected individual in a linked family. While no FU mutations were found, three single nucleotide polymorphisms were identified. The expression pattern of FU was thoroughly investigated and all examined tissues express FU. It is also clear that different tissues express transcripts of different sizes and some tissues express more than one transcript. By means of nested PCR of specific regions in RT/PCR generated cDNA, it was possible to verify two alternative splicing events. This also suggests the existence of at least two additional protein isoforms besides the FU protein that has previously been described. This long FU and a much shorter isoform were compared for the ability to regulate GLI1 and GLI2. None of the FU isoforms showed any effects on GLI1 induced transcription but the long form can enhance GLI2 activity. Apparently FU did not have any effect on SUFU induced inhibition of GLI. CONCLUSIONS: The FU gene and its genomic structure was identified. FU is a candidate gene for SD1, but we have not identified a pathogenic mutation in the FU coding region in a family with SD1. The sequence information and expression analyses show that transcripts of different sizes are expressed and subjected to alternative splicing. Thus, mRNAs may contain different 5'UTRs and encode different protein isoforms. Furthermore, FU is able to enhance the activity of GLI2 but not of GLI1, implicating FU in some aspects of Hedgehog signaling.

Chromosome Mapping↗

The tissue microarray data exchange specification: a document type definition to validate and enhance XML data.

BACKGROUND: The Association for Pathology Informatics (API) Extensible Mark-up Language (XML) TMA Data Exchange Specification (TMA DES) proposed in April 2003 provides a community-based, open source tool for sharing tissue microarray (TMA) data in a common format. Each tissue core within an array has separate data including digital images; therefore an organized, common approach to produce, navigate and publish such data facilitates viewing, sharing and merging TMA data from different laboratories. The AIDS and Cancer Specimen Resource (ACSR) is a HIV/AIDS tissue bank consortium sponsored by the National Cancer Institute (NCI) Division of Cancer Treatment and Diagnosis (DCTD). The ACSR offers HIV-related malignancies and uninfected control tissues in microarrays (TMA) accompanied by de-identified clinical data to approved researchers. Exporting our TMA data into the proposed API specified format offers an opportunity to evaluate the API specification in an applied setting and to explore its usefulness. RESULTS: A document type definition (DTD) that governs the allowed common data elements (CDE) in TMA DES export XML files was written, tested and evolved and is in routine use by the ACSR. This DTD defines TMA DES CDEs which are implemented in an external file that can be supplemented by internal DTD extensions for locally defined TMA data elements (LDE). CONCLUSION: ACSR implementation of the TMA DES demonstrated the utility of the specification and allowed application of a DTD to validate the language of the API specified XML elements and to identify possible enhancements within our TMA data management application. Improvements to the specification have additionally been suggested by our experience in importing other institution's exported TMA data. Enhancements to TMA DES to remove ambiguous situations and clarify the data should be considered. Better specified identifiers and hierarchical relationships will make automatic use of the data possible. Our tool can be used to reorder data and add identifiers; upgrading data for changes in the specification can be automatically accomplished. Using a DTD (optionally reflecting our proposed enhancements) can provide stronger validation of exported TMA data.

AIDS-Related Complex↗

The tissue micro-array data exchange specification: a web based experience browsing imported data.

BACKGROUND: The AIDS and Cancer Specimen Resource (ACSR) is an HIV/AIDS tissue bank consortium sponsored by the National Cancer Institute (NCI) Division of Cancer Treatment and Diagnosis (DCTD). The ACSR offers to approved researchers HIV infected biologic samples and uninfected control tissues including tissue cores in micro-arrays (TMA) accompanied by de-identified clinical data. Researchers interested in the type and quality of TMA tissue cores and the associated clinical data need an efficient method for viewing available TMA materials. Because each of the tissue samples within a TMA has separate data including a core tissue digital image and clinical data, an organized, standard approach to producing, navigating and publishing such data is necessary. The Association for Pathology Informatics (API) extensible mark-up language (XML) TMA data exchange specification (TMA DES) proposed in April 2003 provides a common format for TMA data. Exporting TMA data into the proposed format offers an opportunity to implement the API TMA DES. Using our public BrowseTMA tool, we created a web site that organizes and cross references TMA lists, digital "virtual slide" images, TMA DES export data, linked legends and clinical details for researchers. Microsoft Excel and Microsoft Word are used to convert tabular clinical data and produce an XML file in the TMA DES format. The BrowseTMA tool contains Extensible Stylesheet Language Transformation (XSLT) scripts that convert XML data into Hyper-Text Mark-up Language (HTML) web pages with hyperlinks automatically added to allow rapid navigation. RESULTS: Block lists, virtual slide images, legends, clinical details and exports have been placed on the ACSR web site for 14 blocks with 1623 cores of 2.0, 1.0 and 0.6 mm sizes. Our virtual microscope can be used to view and annotate these TMA images. Researchers can readily navigate from TMA block lists to TMA legends and to clinical details for a selected tissue core. Exports for 11 blocks with 3812 cores from three other institutions were processed with the BrowseTMA tool. Fifty common data elements (CDE) from the TMA DES were used and 42 more created for site-specific data. Researchers can download TMA clinical data in the TMA DES format. CONCLUSION: Virtual TMAs with clinical data can be viewed on the Internet by interested researchers using the BrowseTMA tool. We have organized our approach to producing, sorting, navigating and publishing TMA information to facilitate such review. We have converted Excel TMA data into TMA DES XML, and imported it and TMA DES XML from another institution into BrowseTMA to produce web pages that allow us to browse through the merged data. We proposed enhancements to the TMA DES as a result of this experience. We implemented improvements to the API TMA DES as a result of using exported data from several institutions. A document type definition was written for the API TMA DES (that optionally includes proposed enhancements). Independent validators can be used to check exports against the DTD (with or without the proposed enhancements). Linking tissue core images to readily navigable clinical data greatly improves the value of the TMA.

AIDS-Related Complex↗

Overexpression of Eag1 potassium channels in clinical tumours.

BACKGROUND: Certain types of potassium channels (known as Eag1, KCNH1, Kv10.1) are associated with the production of tumours in patients and in animals. We have now studied the expression pattern of the Eag1 channel in a large range of normal and tumour tissues from different collections utilising molecular biological and immunohistochemical techniques. RESULTS: The use of reverse transcription real-time PCR and specifically generated monoclonal anti-Eag1 antibodies showed that expression of the channel is normally limited to specific areas of the brain and to restricted cell populations throughout the body. Tumour samples, however, showed a significant overexpression of the channel with high frequency (up to 80% depending on the tissue source) regardless of the detection method (staining with either one of the antibodies, or detection of Eag1 RNA). CONCLUSION: Inhibition of Eag1 expression in tumour cell lines reduced cell proliferation. Eag1 may therefore represent a promising target for the tailored treatment of human tumours. Furthermore, as normal cells expressing Eag1 are either protected by the blood-brain barrier or represent the terminal stage of normal differentiation, Eag1 based therapies could produce only minor side effects.

Animals↗

Perlecan, a candidate gene for the CAPB locus, regulates prostate cancer cell growth via the Sonic Hedgehog pathway.

BACKGROUND: Genetic studies associated the CAPB locus with familial risk of brain and prostate cancers. We have identified HSPG2 (Perlecan) as a candidate gene for CAPB. Previously we have linked Perlecan to Hedgehog signaling in Drosophila. More recently, we have demonstrated the importance of Hedgehog signaling in humans for advanced prostate cancer. RESULTS: Here we demonstrate Perlecan expression in prostate cancer, and its function in prostate cancer cell growth through interaction and modulation of Sonic Hedgehog (SHH) signaling. Perlecan expression in prostate cancer tissues correlates with a high Gleason score and rapid cell proliferation. Perlecan is highly expressed in prostate cancer cell lines, including androgen insensitive cell lines and cell lines selected for metastatic properties. Inhibition of Perlecan expression in these cell lines decreases cell growth. Simultaneous blockade of Perlecan expression and androgen signaling in the androgen-sensitive cell line LNCaP was additive, indicating the independence of these two pathways. Perlecan expression correlates with SHH in tumor tissue microarrays and increased tumor cell proliferation based on Ki-67 immunohistochemistry. Inhibition of Perlecan expression by siRNA in prostate cancer cell lines decreases SHH signaling while expression of the downstream SHH effector GLI1 rescues the proliferation defect. Perlecan forms complexes with increasing amounts of SHH that correlate with increasing metastatic potential of the prostate cancer cell line. SHH signaling also increases in the more metastatic cell lines. Metastatic prostate cancer cell lines grown under serum-starved conditions (low androgen and growth factors) resulted in maintenance of Perlecan expression. Under low androgen, low growth factor conditions, Perlecan expression level correlates with the ability of the cells to maintain SHH signaling. CONCLUSION: We have demonstrated that Perlecan, a candidate gene for the CAPB locus, is a new component of the SHH pathway in prostate tumors and works independently of androgen signaling. In metastatic tumor cells increased SHH signaling correlates with the maintenance of Perlecan expression and more Perlecan-SHH complexes. Perlecan is a proteoglycan that regulates extracellular and stromal accessibility to growth factors such as SHH, thus allowing for the maintenance of SHH signaling under growth factor limiting conditions. This proteoglycan represents an important central regulator of SHH activity and presents an ideal drug target for blocking SHH effects.

Cell Line, Tumor↗

Measuring proliferation in breast cancer: practicalities and applications.

Various methods are available for the measurement of proliferation rates in tumours, including mitotic counts, estimation of the fraction of cells in S-phase of the cell cycle and immunohistochemistry of proliferation-associated antigens. The evidence, advantages and disadvantages for each of these methods along with other novel approaches is reviewed in relation to breast cancer. The potential clinical applications of proliferative indices are discussed, including their use as prognostic indicators and predictors of response to systemic therapy.

Antigens, Nuclear↗

Immunohistochemical expression of DNA repair proteins in familial breast cancer differentiate BRCA2-associated tumors.

PURPOSE: Morphologic and immunohistochemical studies of familial breast cancers have identified specific characteristics associated with BRCA1 mutation-associated tumors when compared with BRCA2 and non-BRCA1/2 tumors, but have not identified differences between BRCA2 and non-BRCA1/2 tumors. Because BRCA1 and BRCA2 genes participate in the DNA repair pathway, we have performed an immunohistochemical study with markers related to this pathway to establish the profile of the three groups. MATERIALS AND METHODS: We have studied two tissue microarrays that include 103 familial and 104 sporadic breast tumors, with a panel of DNA repair markers including ATM, CHEK2, RAD51, RAD50, XRCC3, and proliferating cell nuclear antigen. RESULTS: We found more frequent expression of CHEK2 in BRCA1 and BRCA2 tumors than in non-BRCA1/2 and sporadic tumors. We found absence of nuclear expression and presence of cytoplasmic expression of RAD51 in BRCA2 tumors that differentiate them from other familial tumors. We validated these results with a new series of patient cases. The final study with 253 familial patient cases (74 BRCA1, 71 BRCA2, 108 non-BRCA1/2), and 288 sporadic patient cases, has allowed us to confirm our preliminary results. Because BRCA2 tumors present a specific immunohistochemical profile for RAD51 and CHEK2 markers that is different from non-BRCA1/2 tumors, we have built a multivariate model with these markers that distinguish both tumors with an estimated probability of at least 76%. CONCLUSION: Our results suggest that BRCA2 tumors demonstrate more cytoplasmic and less nuclear RAD51 staining, and increased CHEK2 staining. This pattern may distinguish BRCA2 from familial non-BRCA1/2 tumors.

Acid Anhydride Hydrolases↗

Estrogen-receptor-alpha exchange and chromatin dynamics are ligand- and domain-dependent.

We report a mammalian-based promoter chromosomal array system developed for single-cell studies of transcription-factor function. Designed after the prolactin promoter-enhancer, it allows for the direct visualization of estrogen receptor alpha (ERalpha) and/or Pit-1 interactions at a physiologically regulated transcription locus. ERalpha- and ligand-dependent cofactor recruitment, large-scale chromatin modifications and transcriptional activity identified a distinct fingerprint of responses for each condition. Ligand-dependent transcription (more than threefold activation compared with vehicle, or complete repression by mRNA fluorescent in situ hybridization) at the array correlated with its state of condensation, which was assayed using a novel high throughput microscopy approach. In support of the nuclear receptor hit-and-run model, photobleaching studies provided direct evidence of very transient ER-array interactions, and revealed ligand-dependent changes in k(off). ERalpha-truncation mutants indicated that helix-12 and interactions with co-regulators influenced both large-scale chromatin modeling and photobleaching recovery times. These data also showed that the ERalpha DNA-binding domain was insufficient for array targeting. Collectively, quantitative observations from this physiologically relevant biosensor suggest stochastic-based dynamics influence gene regulation at the promoter level.

Active Transport, Cell Nucleus↗

Immunohistochemical expression of p16INK4A, Ki-67, and Mcm2 proteins in gastrointestinal stromal tumors: prognostic implications and correlations with risk stratification of NIH consensus criteria.

BACKGROUND: Inactivation of p16(INK4A) promotes G1/S progression of cell cycle. Minichromosome maintenance protein-2 (Mcm2), a novel cell proliferation marker, is known to better correlate with clinical outcomes than Ki-67 in many carcinomas. Since gastrointestinal stromal tumors (GISTs) sometimes remains challenging in prognostication, we analyzed the utility of these three markers in GISTs. METHODS: Immunohistochemistry was performed in tissue microarrays of 277 primary GISTs and correlated with NIH consensus criteria and clinical outcomes. RESULTS: The increment of NIH risk levels significantly correlated with increasing labeling indices (LI) of both Ki-67 (P <.001) and Mcm2 (P <.001) and loss of p16(INK4A) expression (P <.035). However, the latter aberration did occur in 23% of very low/low-risk GISTs. The relationship between Mcm2 and Ki-67 LIs could be modeled as linear (P <.001, r = 0.697), while Mcm2 LI was considerably higher (P <.001) with a stepwise escalation related to risk levels. Ki-67 LI >5% (P <.0001) and Mcm2 LI >10% (P <.0001) were strongly predictive of inferior disease-specific survival (DSS), while aberrant loss of p16(INK4A) only reached a trend (P = .0954). In multivariate analyses, independent adverse factors of DSS were high-risk category (RR = 16.93, P <.0001), metastatic disease (RR = 4.12, P = .0015), Ki-67 LI >5% (RR = 3.55, P = .001), and presence of epithelioid histology (RR = 2.17, P = .0308). CONCLUSIONS: Prognostic efficacy of NIH consensus criteria is substantiated. P16(INK4A) deregulation can occur early in GIST tumorigenesis and marginally correlates with patient survival. Despite Ki-67 LI being an independent prognosticator, simultaneous detection of Mcm2 is recommended as a prognostic adjunct of GISTs, given its better sensitivity and stepwise escalation with increasing risk levels.

Adult↗

p16INK4A (CDKN2A) gene deletion is a frequent genetic event in synovial sarcomas.

We assessed the frequency of genomic deletion of p16INK4A (CDKN2A) in synovial sarcomas (SSs) and its possible association with immunoexpression of p16 and cyclin D1 and the Ki-67 proliferation index using dual-color fluorescence in situ hybridization (FISH) on tissue microarray sections of 41 histologically and molecularly confirmed SSs. A heterozygous p16INK4A gene deletion was identified in 28 (74%) of 38 cases, with 25 (89%) of them showing abnormal p16 protein expression (20 negative and 5 heterogeneous). Of 25 cases, 19 (76%) exhibiting increased cyclin D1expression also demonstrated heterozygous p16INK4A deletion. No significant association was observed between p16INK4A deletion and Ki-67 proliferation index, tumor grade, or histologic subtype. Our results demonstrate that p16INK4A (CDKN2A) gene deletion is a frequent genetic event in SS.

Biomarkers, Tumor↗

Simple, inexpensive, and precise paraffin tissue microarrays constructed with a conventional microcompound table and a drill grinder.

In 1998, paraffin tissue microarrays (PTMAs) as paraffin blocks containing up to 1,000 cylindrical paraffin tissue core biopsy specimens (PTCBs) for high-throughput molecular profiling of tumor specimens were introduced. PTCBs can be constructed using a manual tissue puncher/arrayer (Beecher Instruments, Sun Prairie, WI; cost, at least $7,000). Furthermore, custom-built PTMAs such as the MaxArray are created by companies such as Zymed Laboratories (South San Francisco, CA; PTMA with 96 holes, about $900). In our search for a less expensive alternative, we constructed PTMAs with up to 558 PTCBs by using a drill grinder, a drill stand, and a microcompound table (Proxxon, Niersdorf, Germany; cost, <$300).

Humans↗

Expression of the B cell-associated transcription factors PAX5, OCT-2, and BOB.1 in acute myeloid leukemia: associations with B-cell antigen expression and myelomonocytic maturation.

The aberrant expression of the B-cell transcription factor PAX5 has been described in a subset of acute myeloid leukemia (AML) with t(8;21)(q22;q22) in association with B-cell antigen expression. However, the expression of other B cell-associated transcription factors, particularly OCT-2 and its B cell-specific coactivator BOB.1, has not been described in AML. In this study, expression of PAX5, OCT-2 and BOB.1 was evaluated by immunohistochemical staining of bone marrow samples from 83 cases of AML. The expression patterns were correlated with t(8;21)(q22;q22), B cell-associated antigen expression, and AML subtype. We confirmed the expression of PAX5 in AML with t(8;21)(q22;q22), but also demonstrated its expression in cases that express B-cell antigens but lack this translocation. Although OCT-2 and BOB.1 were not associated with PAX5 expression, we report expression of OCT-2 in AML with myelomonocytic/monocytic maturation and BOB.1 in normal hematopoietic elements.

Acute Disease↗

Reproducibility of MDM2 and CDK4 staining in soft tissue tumors.

MDM2 and CDK4 immunostaining can be useful adjuncts in diagnosing liposarcoma among soft tissue neoplasms. We examined the reproducibility of MDM2 and CDK4 staining between 2 laboratories and between tissue microarrays and whole tissue sections. Sixty-two soft tissue tumors were immunostained at the Bergonié Institute, Bordeaux, France, and the Curie Institute, Paris, France. We also examined 203 soft tissue neoplasms on standard tissue sections and tissue microarrays. There was high concordance of results obtained from the 2 laboratories (with 2 different pathologists) for MDM2 (kappa, 0.93) and CDK4 (kappa, 0.8) staining. There also was excellent concordance between results on tissue microarray and on whole tissue sections for MDM2 (kappa, 0.80) and CDK4 (kappa, 0.93). Immunostaining for MDM2 and CDK4 is a reproducible technique that may be exported to different laboratories for routine use. Tissue microarray is indicated for studying large series.

Biomarkers, Tumor↗