Generation of cell lines for drug discovery through random activation of gene expression: application to the human histamine H3 receptor.

Target-based high-throughput screening (HTS) plays an integral role in drug discovery. The implementation of HTS assays generally requires high expression levels of the target protein, and this is typically accomplished using recombinant cDNA methodologies. However, the isolated gene sequences to many drug targets have intellectual property claims that restrict the ability to implement drug discovery programs. The present study describes the pharmacological characterization of the human histamine H3 receptor that was expressed using random activation of gene expression (RAGE), a technology that over-expresses proteins by up-regulating endogenous genes rather than introducing cDNA expression vectors into the cell. Saturation binding analysis using [125I]iodoproxyfan and RAGE-H3 membranes revealed a single class of binding sites with a K(D) value of 0.77 nM and a B(max) equal to 756 fmol/mg of protein. Competition binding studies showed that the rank order of potency for H3 agonists was N(alpha)-methylhistamine approximately (R)-alpha- methylhistamine > histamine and that the rank order of potency for H3 antagonists was clobenpropit > iodophenpropit > thioperamide. The same rank order of potency for H3 agonists and antagonists was observed in the functional assays as in the binding assays. The Fluorometic Imaging Plate Reader assays in RAGE-H3 cells gave high Z' values for agonist and antagonist screening, respectively. These results reveal that the human H3 receptor expressed with the RAGE technology is pharmacologically comparable to that expressed through recombinant methods. Moreover, the level of expression of the H3 receptor in the RAGE-H3 cells is suitable for HTS and secondary assays.

Creation of genome-wide protein expression libraries using random activation of gene expression.

Here we report the use of random activation of gene expression (RAGE) to create genome-wide protein expression libraries. RAGE libraries containing only 5 x 10(6) individual clones were found to express every gene tested, including genes that are normally silent in the parent cell line. Furthermore, endogenous genes were activated at similar frequencies and expressed at similar levels within RAGE libraries created from multiple human cell lines, demonstrating that RAGE libraries are inherently normalized. Pools of RAGE clones were used to isolate 19,547 human gene clusters, approximately 53% of which were novel when tested against public databases of expressed sequence tag (EST) and complementary DNA (cDNA). Isolation of individual clones confirmed that the activated endogenous genes can be expressed at high levels to produce biologically active proteins. The properties of RAGE libraries and RAGE expression clones are well suited for a number of biotechnological applications including gene discovery, protein characterization, drug development, and protein manufacturing.

Fecal calprotectin levels predict colorectal inflammation among patients with chronic diarrhea referred for colonoscopy.

OBJECTIVE: Chronic diarrhea is a relatively common condition with multiple diverse etiologies. Stool testing may serve as a diagnostic aid to discriminate the presence or absence of organic pathology, such as colorectal inflammation. Calprotectin (a leukocyte-derived protein) and hemoglobin can be measured quantitatively from stool and represent candidate inflammation biomarkers. The aim of this study was to assess and compare the screening performance of fecal calprotectin and fecal hemoglobin among colonoscopy referral patients with chronic diarrhea of unknown origin or chronic colitis of unknown activity. METHODS: All subjects were identified prospectively and each submitted a single stool sample before purgation. Fecal calprotectin (PhiCal; Nycomed Pharma, Oslo, Norway) and fecal hemoglobin (HemoQuant; Mayo Medical Laboratories, Rochester, MN) assays were performed in separate laboratories by masked technicians. Colonoscopic and histological findings served as criterion standards for establishing the presence or absence of colorectal inflammation. RESULTS: Among 110 subjects who provided complete fecal assay data, 29 (26%) had and 81 (74%) did not have colorectal inflammation. Increased fecal calprotectin levels were significantly (p = 0.0001) associated with the presence of colorectal inflammation, whereas fecal hemoglobin levels were not (p = 0.61). Direct comparison of the fecal assays revealed that calprotectin was a more sensitive biomarker for colorectal inflammation at all specificity levels (p = 0.0001). CONCLUSIONS: In this study of colonoscopy referral patients, colorectal inflammation was reflected by fecal calprotectin but not by fecal hemoglobin levels. Assay of fecal calprotectin holds promise as a triage tool to identify inflammatory causes of chronic diarrhea.

Colorectal cancer screening by detection of altered human DNA in stool: feasibility of a multitarget assay panel.

BACKGROUND & AIMS: Assay of altered DNA exfoliated into stool represents an intriguing approach to screen for colorectal neoplasia, but multiple markers must be targeted because of genetic heterogeneity. We explored the feasibility of a stool assay panel of selected DNA alterations in discriminating subjects with colorectal neoplasia from those without. METHODS: Freezer-archived stools were analyzed in blinded fashion from 22 patients with colorectal cancer, 11 with adenomas > or =1 cm, and 28 with endoscopically normal colons. After isolation of human DNA from stool by sequence-specific hybrid capture, assay targets included point mutations at any of 15 sites on K-ras, p53, and APC genes; Bat-26, a microsatellite instability marker; and highly amplifiable DNA. RESULTS: Analyzable human DNA was recovered from all stools. Sensitivity was 91% (95% confidence interval, 71%-99%) for cancer and 82% (48%-98%) for adenomas > or =1 cm with a specificity of 93% (76%-99%). Excluding K-ras from the panel, sensitivities for cancer were unchanged but decreased slightly for adenomas to 73% (39%-94%), while specificity increased to 100% (88%-100%). CONCLUSIONS: Assay of altered DNA holds promise as a stool screening approach for colorectal neoplasia. Larger clinical investigations are indicated.

Immunodiscrimination of colorectal neoplasia using MUC1 antibodies: discrepant findings in tissue versus stool.

Colorectal tumor-associated antigens are attractive targets for novel stool-screening assays. MUC1, a glycoprotein antigen, is aberrantly expressed in transformed colorectal mucosa and represents a candidate fecal biomarker. In this study, tissue staining and stool testing were performed to further clarify the discriminant potential of MUC1 in markedly different biologic media. One anti-MUC1 monoclonal antibody (MA5) was used for immunohistochemistry and two commercially available MUC1 assay kits (ELSA-CA 15-3 and Truquant BR) were used for stool detection. On tissue staining, MUC1 expression was strong in 40/40 (100%) adenocarcinomas, moderate in 42/55 (76%) adenomas, faint in 8/28 (29%) juxtatumoral mucosa specimens, and absent in 15/15 (0%) nonadjacent mucosa specimens. Conversely MUC1 levels in stool testing did not differ between colorectal cancer cases (N = 14) and controls (N = 14). Based on these results, MUC1 appears to be a functional tumor biomarker in colorectal tissue but not in stool. Bacterial metabolism within stool may unmask the core antigen of MUC1 and account for this discordance in immunoreactivity.

Morphometric analysis of the "mucocellular layer" overlying colorectal cancer and normal mucosa: relevance to exfoliation and stool screening.

Characterization of shed cell elements entrapped within the colorectal surface mucus would be valuable to the study of exfoliation and candidate stool screening markers. Yet, surprisingly little is known about the cellular composition of this "mucocellular layer" (MCL). Our aim was to describe and compare the histomorphometry of the MCL that overlies colorectal cancer (CRC) and normal mucosa. From tissue archives, 20 resected CRC specimens yielding perpendicular cuts of both tumor surface and adjacent normal mucosa were consecutively selected. MCL thickness and cell number were determined in triplicate using an ocular micrometer. Cellular elements within the MCL were characterized on paraffin sections by immunohistochemistry. Mean cell density was much greater in the MCL over CRC (2,639 +/- 2,178 per mm2) than over normal mucosa (184 +/- 395 per mm2), p < .001. Robust-appearing colonocytes and inflammatory cells predominated in the hypercellular MCL of CRC; the former retained expression of tumor-associated antigens. In contrast, the sparsely scattered cells within the normal MCL were typically apoptotic and of indeterminate lineage. Based on direct observations from this first descriptive study of the colorectal MCL, luminal shedding appears to be much greater from CRC than from normal mucosa.

Mycobacterium tuberculosis lipid antigens: use of multi-antigen based enzyme immunoassay for free and complex dissociated antibodies.

OBJECTIVE: To test the sensitivity and specificity of four lipid antigens of Mycobacterium tuberculosis: BDA-TDA, DAT, SL-I, and PIMs, adsorbed in the same microplate well, to detect reactive IgG by enzyme-immunoassay (EIA) from plain serum (MA-EIA) and dissociated immune complexes (ICMA-EIA). DESIGN: IgG antibodies against four antigens, placed in the same microplate well, were evaluated in serum from 155 tuberculous (TB) cases non-infected with the human immunodeficiency virus (HIV): 78 patients with positive bacilloscopy and culture, 33 patients with positive culture and 44 patients diagnosed by clinical and radiological criteria; and from 211 HIV negative control subjects: 32 patients with other pulmonary diseases, 100 healthy people and 79 close contacts. RESULTS: MA-EIA had an overall sensitivity and specificity of 61% (94/155) and 95% (200/211), respectively. We further examined whether the dissociation of immune complexes increases the number of positive reactions in those initially found to be seronegative (SN). The subset of 112 (76 controls and 36 TB) MA-EIA SN samples tested using ICMA-EIA yielded an overall sensitivity and specificity of 83% and 100%. The ICMA-EIA results improved the overall sensitivity from 61 to 80% without changing specificity. CONCLUSION: These preliminary results suggest that MA-EIA followed by ICMA-EIA, for SN samples, might serve as a fast, cheap, and easy method for the diagnosis of TB in less than 48 hours.

Formation of de novo centromeres and construction of first-generation human artificial microchromosomes.

We have combined long synthetic arrays of alpha satellite DNA with telomeric DNA and genomic DNA to generate artificial chromosomes in human HT1080 cells. The resulting linear microchromosomes contain exogenous alpha satellite DNA, are mitotically and cytogenetically stable in the absence of selection for up to six months in culture, bind centromere proteins specific for active centromeres, and are estimated to be 6-10 megabases in size, approximately one-fifth to one-tenth the size of endogenous human chromosomes. We conclude that this strategy results in the formation of de novo centromere activity and that the microchromosomes so generated contain all of the sequence elements required for stable mitotic chromosome segregation and maintenance. This first-generation system for the construction of human artificial chromosomes should be suitable for dissecting the sequence requirements of human centromeres, as well as developing constructs useful for therapeutic applications.

DNA structural elements required for FEN-1 binding.

In eukaryotic cells, a 5'-flap DNA endonuclease and a double-stranded DNA 5'-exonuclease activity reside within a 42-kDa enzyme called FEN-1 (flap endonuclease-1 and 5(five)'-exonuclease). This endo/exonuclease has been shown to be highly homologous to human XP-G, Saccharomyces cerevisiae RAD2, and S. cerevisiae YKL510. Like FEN-1, these related structure-specific nucleases recognize and cleave a branched DNA structure called a DNA flap and its derivative, called a pseudo Y-structure. To dissect the important structural components of the DNA flap structure, we have developed a mobility shift assay. We find that the Fadj strand (located adjacent to the displaced flap strand) is necessary for efficient binding and cleavage of flap structures by FEN-1. When this strand is absent or when it is present, but recessed from the elbow of the flap strand, binding efficiency drops. Further investigation of the role of the Fadj strand using double flap structures reveals that the Fadj strand is necessary to provide a double-stranded template upon which FEN-1 can bind near the elbow of the flap strand. These results provide a basis for understanding how this structure-specific nuclease recognizes a variety of DNA substrates.

Sequence of human FEN-1, a structure-specific endonuclease, and chromosomal localization of the gene (FEN1) in mouse and human.

We recently purified and cloned the gene for a DNA structure-specific endonuclease, FEN-1, from murine cells. The murine protein recognizes 5' DNA flap structures that have been proposed in DNA replication, repair, and recombination. Here, we report the sequence of the human FEN1 gene. The translated sequence is identical to peptide sequence obtained from maturation factor-1, which is 1 of the 10 essential proteins for cell-free DNA replication. The human protein has the same structure-specific DNA endonuclease activity as the murine protein. Two human chromosomal hybridization signals, 11q12 and 1p22.2, were observed by FISH analysis using human genomic clones homologous to the mouse Fen-1 gene. The localization on human 11q12 was confirmed using radiation-reduced hybrids. The mouse Fen-1 gene is assigned to chromosome 19 based on somatic cell hybrids. The significance of these FEN1 gene localizations in human and mouse is discussed.

Functional domains within FEN-1 and RAD2 define a family of structure-specific endonucleases: implications for nucleotide excision repair.

Structure-specific nucleases catalyze critical reactions in DNA replication, recombination, and repair. Recently, a structure-specific endonuclease, FEN-1, has been purified and shown to cleave DNA flap structures. Here, we describe the cloning of the murine FEN-1 gene. The nucleotide sequence of FEN-1 is highly homologous to the Saccharomyces cerevisiae genes YKL510 and RAD2. We show that YKL510 and a truncated RAD2 protein are also structure-specific endonucleases. The substrate specificity of the truncated RAD2 protein implicates branched DNA structures as important intermediates in nucleotide excision repair. The polarity of these branched DNA structures allows us to predict the placement of DNA scissions by RAD2 and RAD1/RAD10 in this reaction.

The characterization of a mammalian DNA structure-specific endonuclease.

The repair of some types of DNA double-strand breaks is thought to proceed through DNA flap structure intermediates. A DNA flap is a bifurcated structure composed of double-stranded DNA and a displaced single-strand. To identify DNA flap cleaving activities in mammalian nuclear extracts, we created an assay utilizing a synthetic DNA flap substrate. This assay has allowed the first purification of a mammalian DNA structure-specific nuclease. The enzyme described here, flap endonuclease-1 (FEN-1), cleaves DNA flap strands that terminate with a 5' single-stranded end. As expected for an enzyme which functions in double-strand break repair flap resolution, FEN-1 cleavage is flap strand-specific and independent of flap strand length. Furthermore, efficient flap cleavage requires the presence of the entire flap structure. Substrates missing one strand are not cleaved by FEN-1. Other branch structures, including Holliday junctions, are also not cleaved by FEN-1. In addition to endonuclease activity, FEN-1 has a 5'-3' exonuclease activity which is specific for double-stranded DNA. The endo- and exonuclease activities of FEN-1 are discussed in the context of DNA replication, recombination and repair.

IEEE (Institute of Electrical and Electronic Engineers) P1157 Medical Data Interchange (MEDIX): application of open systems to health care communications.

IT offers the potential for controlling the rising costs of health care while continuing to improve the quality of health care delivery. Health care communications standards are a necessary condition to accelerating the diffusion of IT in health care. The IEEE P1157 standards, which are international in scope, are being developed by a process of open participation under the auspices of the IEEE EMBS to meet strict conformance to the ISO/OSI standards. The IEEE P1157 standards are being coordinated with related health care information systems and will make an important contribution in this area. The initial focus of the IEEE P1157 committee will provide a needed subset of the eventual standard in 1991. The long-term focus on the patient record will provide the groundwork for extension of the effort to cover communications in all of health care. Development of these standards is based upon voluntary effort. All health care professionals with an interest in this area are urged to participate actively in the process.

Chemically sensitized erythrocytes for hemagglutination reactions.

The use of chemically modified indicator erythrocytes for hemagglutination reactions can result in increased sensitivity. Treatment of erythrocytes with polyvinylpyrrolidone (PVP) or dextran T40 (10% weight/volume) induces changes in the cell surface in the form of extensions and blebbing, thereby increasing the surface area. These sensitized cells can be used in forensic science when detection or quantitation of erythrocyte surface reacting antibodies is important. The effect of altering membrane lipid fluidity on erythrocyte surface antigens has also been investigated. Treatment of cells with a reagent that increases the membrane ratio of cholesterol to phospholipid results in enhanced hemagglutination capacity despite the lack of extensive spiculation.

Detection of hemagglutinins in dried saliva stains and their potential use in blood typing.

Since 1928, hemagglutinins have been known to exist in saliva; however, they have not been utilized as evidence in criminal investigations because in the past, techniques for measuring them have not been sufficiently sensitive. In this paper we describe improved techniques for detecting salivary hemagglutinins and report initial results obtained with these methods. The stability of salivary hemagglutinins at several different temperatures was examined in liquid samples and in dried stains on filter paper, cigarette butts, and envelope flaps. Our observations indicate that salivary hemagglutinins may be sufficiently stable, over periods of one to several days at ambient room temperatures, to be of value to forensic science investigators. The results of the hemagglutinin assay are not affected by the age or sex of the sample donor. Because salivary hemagglutinins can be used to determine ABO blood type, analyses of this kind can serve as an important confirmatory test which the forensic serologist can use in conjunction with salivary agglutinogen determinations.

Detection and use of salivary hemagglutinins for forensic blood grouping.

A sensitive method for the detection of anti-A and anti-B hemagglutinins in fresh saliva has been developed. The method utilizes a bromelin treated erythrocyte suspension as indicator cells and includes a simple procedure to concentrate these hemagglutinins. Antiserum directed against immunoglobulin A enhances the hemagglutination assay. We find that these salivary hemagglutinins are present in over 90% of the population and that their titer remains stable over a period of two months. These hemagglutinins can be used to blood type the donor of a saliva sample and can be used in a confirmatory test that complements the commonly used absorption-inhibition test which is used to detect salivary blood group agglutinogens. In preliminary studies we have determined that hemagglutinins can be successfully isolated and analyzed from dried saliva stains.

Pseudoaneurysm of the left ventricle: an unusual echocardiographic presentation. Review of the literature.

Echocardiography showed a large anterior chamber communicating with the left ventricle cavity through the interventricular septum in a patient with a previous left ventricular aneurysmectomy. At postmortem examination this chamber proved to be an 11-cm diameter pseudoaneurysm that opened into the left ventricle through a 3-cm orifice. A review of the literature showed 67 cases of histologically proven left ventricular pseudoaneurysm, most of which occurred after myocardial infarction and cardiac surgery. Twenty-six of 32 left ventricular pseudoaneurysms were successfully operated upon. Among 35 patients with pseudoaneurysms not operated upon, rupture was a cause of death in 11.