Biomedical subjects

Wendy Wang

Publications and source records attributed to Wendy Wang.

9 recordsLinked to original sources

PubMed2006

Real-time telomerase assay of less-invasively collected esophageal cell samples.

Genomic and proteomic efforts have discovered a complex list of biomarkers that identify human disease, stratify risk of disease within populations, and monitor drug or therapy responses for treatment. Attention is needed to characterize these biomarkers and to develop high-throughput technologies to evaluate their accuracy and precision. Telomerase activity is correlated with tumor progression, indicating cells that express telomerase possess aggressive clinical behavior and that telomerase activity could be a clinically important cancer biomarker. Traditionally, the detection of cancer has involved invasive procedures to procure samples. There is a need for less invasive approaches suitable for population- and clinic-based assays for cancer early detection. Esophageal balloon cytology (EBC) is a low-invasive screening technique, which samples superficial epithelial cells from the esophagus. Since telomerase activity is absent in superficial cells of normal esophageal squamous epithelium but is often present in superficial cells from dysplastic lesions and ESCCs, measuring telomerase activity in EBC samples may be a good way to screen for these lesions. The development of rapid real-time telomerase activity assays raises the possibility of extending such screening to high-risk populations. In this study, we evaluate the feasibility of using rapid Real-Time Telomerase Repeat Amplification Protocol (RTTRAP) for the analysis of NIST telomerase candidate reference material and esophageal clinical samples. The telomerase activity of eight EBC samples was also measured by capillary electrophoresis of RTTRAP products, RApidTRAP, and hTERT mRNA RT-PCR assays. These findings demonstrate the feasibility of using the RTTRAP assay in EBC samples and suggest that individuals from high-risk populations can be screened for telomerase activity.

Biomarkers, Tumor↗

PubMed2005

Preparation and characterization of candidate reference materials for telomerase assays.

BACKGROUND: Telomerase has been measured in body fluids of cancer patients, and clinical tests for telomerase may have utility as noninvasive, cost-effective methods for the early detection of cancer. However, telomerase activity measured by common methods such as the telomerase repeat amplification protocol (TRAP) and telomerase reverse transcriptase catalytic subunit (hTERT) mRNA by reverse transcription-PCR (RT-PCR) varies among laboratories. METHODS: We prepared a CHAPS buffer lysate from cultured A549 cells and stored it at -80 degrees C. Telomerase activity was measured by TRAP/PCR and real-time TRAP/PCR in conjunction with RT-PCR measurements of hTERT mRNA. Activity measured with use of the robot-assisted TRAP (RApidTRAP) multicapillary electrophoresis system was compared with single-capillary and slab-gel measurements in the range 10 to 10 000 cell equivalents. RESULTS: Preparations made after flash freezing and sonication of cells were approximately 3-fold more active. Although the slab-gel and capillary instruments detected telomerase activity, the multicapillary instrument was better suited for high-throughput studies. Measurements of telomerase by TRAP/real-time PCR and hTERT mRNA/RT-PCR yielded reproducible titrations in the range 10 to 10 000 cell equivalents (CVs, 1%-8% and 1%-3%, respectively). CONCLUSIONS: We have prepared and characterized a candidate reference material that appears to be suitable for use in a wide range of assays of telomerase activity and expression.

Biomarkers, Tumor↗

PubMed2005

Mitochondrial DNA as a cancer biomarker.

As part of a national effort to identify biomarkers for the early detection of cancer, we developed a rapid and high-throughput sequencing protocol for the detection of sequence variants in mitochondrial DNA. Here, we describe the development and implementation of this protocol for clinical samples. Heteroplasmic and homoplasmic sequence variants occur in the mitochondrial genome in patient tumors. We identified these changes by sequencing mitochondrial DNA obtained from tumors and blood from the same individual. We confirmed previously identified primary lung tumor changes and extended these findings in a small patient cohort. Eight sequence variants were identified in stage I to stage IV tumor samples. Two of the sequence variants identified (22%) were found in the D-loop region, which accounts for 6.8% of the mitochondrial genome. The other sequence variants were distributed throughout the coding region. In the forensic community, the sequence variations used for identification are localized to the D-loop region because this region appears to have a higher rate of mutation. However, in lung tumors the majority of sequence variation occurred in the coding region. Hence, incomplete mitochondrial genome sequencing, designed to scan discrete portions of the genome, misses potentially important sequence variants associated with cancer or other diseases.

Adult↗

PubMed2005

Biomarkers in molecular medicine: cancer detection and diagnosis.

In spite of advances in diagnostics and therapeutics, cancer remains the second leading cause of death in the U.S. Successful cancer treatment depends not only on better therapies but also on improved methods to assess an individual's risk of developing cancer and to detect cancers at early stages when they can be more effectively treated. Current cancer diagnostic imaging methods are labor-intensive and expensive, especially for screening large asymptomatic populations. Effective screening strategies depend on methods that are noninvasive and detect cancers in their early stages of development. There is increasing interest and enthusiasm in molecular markers as tools for cancer detection and prognosis. It is hoped that newly discovered cancer biomarkers and advances in high-throughput technologies would revolutionize cancer therapies by improving cancer risk assessment, early detection, diagnosis, prognosis, and monitoring therapeutic response. These biomarkers will be used either as stand-alone tests or to complement existing imaging methods.

Biomarkers, Tumor↗

PubMed2004

Inter-rater agreement on chromosome 5 breakage in FISH-based mutagen sensitivity assays (MSAs).

In chromosome breakage assays, validated, universal criteria for selection of cells and classification of chromosome aberrations may enhance their utility for cancer susceptibility screening. To standardize a fluorescence in situ hybridization (FISH) modification of the mutagen sensitivity assay (MSA), scoring criteria were evaluated by web-based validation. Two hundred digital FISH images were assigned random identification numbers. With this set of images, criteria for inclusion of cells and measurement of the frequency of abnormal cells were evaluated by eight observers, all of whom had five or more years of experience. Observers included doctoral and MS/BS level cytogeneticists, and were drawn from a randomized pool of 54 volunteers. Questions addressed were: (1) how uniformly were criteria applied to analysis of a standard digital FISH image set and (2) did concordance vary with educational level? These data suggest inter-rater agreement within a factor of 2 for average breakage frequency, but revealed greater variability in cell selection. These results aid in estimating the components of assay variance due to definitions, technical parameters and biological variables.

Chromosome Aberrations↗

PubMed2004

Analytical validation of telomerase activity for cancer early detection: TRAP/PCR-CE and hTERT mRNA quantification assay for high-throughput screening of tumor cells.

Activation of telomerase plays a critical role in unlimited proliferation and immortalization of cells. Telomerase activity has been shown to correlate with tumor progression, indicating that tumors expressing this enzyme possess aggressive clinical behavior and that telomerase activity may be a useful biomarker for early detection of cancer. However, measurements of telomerase activity by current methods such as telomeric repeat amplification protocol (TRAP)/polymerase chain reaction (PCR) or antibody-based radioimmunoassay (RIA) are low-throughput and not robust enough to easily accommodate the required statistical analysis to determine whether telomerase activity is a practical biomarker. As part of the National Cancer Institute Early Detection Research Network of analytical validation, we have developed a robot assisted TRAP assay (RApidTRAP) of telomerase, a potential biomarker for cancer early detection. Measurements of human telomerase reverse transcriptase catalytic subunit (hTERT) mRNA were performed in concert with measurement of telomerase activity. For this purpose we determined hTERT mRNA concentration and telomerase activity in human normal (RPE-28) and cancer (A549) cell lines as well as in human serum (SRM 1951A). Telomerase activity measurements were made using the TRAP/PCR capillary electrophoresis (CE) method on (50 to 1000) cells/reaction isolated from cell extracts. Measurement of hTERT mRNA was made using specific primers and probes on a LightCycler in the range of (10 to 7000) cells/reaction. Comparison of high-throughput telomerase activity measurements using the robot and those performed manually were consistent in sensitivity and reproducibility. Using this combination of telomerase activity and hTERT mRNA measurements, the automated system improved efficiency over traditional TRAP/PCR methods.

Biomarkers↗

PubMed2004

A middle school immunization law rapidly and substantially increases immunization coverage among adolescents.

OBJECTIVES: This study assessed the effectiveness of a middle school vaccination requirement for raising second-dose measles, mumps, and rubella vaccine and hepatitis B vaccine coverage among adolescents. METHODS: Random-digit-dialed telephone surveys were conducted before (1998) and after (1999) the implementation of a vaccination requirement for entry into the seventh grade in San Diego, Calif. RESULTS: Vaccination coverage was higher among children subject to the vaccination requirement (seventh-grade students; 60%) than among fifth- and sixth-grade students 1 year before the requirement (13%, P <.001), and 8th- through 12th-grade students not subject to the requirement (27%, P <.0001). CONCLUSIONS: Middle school-entry vaccination requirements can rapidly and substantially raise vaccination coverage among students subject to the law.

Adolescent↗

PubMed2003

High-throughput analysis of telomerase by capillary electrophoresis.

The enzyme telomerase is expressed in (85-90)% of all human cancers, but not in normal, non-stem cell somatic tissues. Clinical assays for telomerase in easily obtained body fluids would have great utility as noninvasive, cost-effective methods for the early detection of cancer. The most commonly used method for the detection and quantification of telomerase enzyme activity is the polymerase chain reaction (PCR)-based assay known as the telomerase repeat amplification protocol or TRAP assay. Most of the TRAP assay systems use a slab-gel based electrophoresis system to size and quantify the PCR-amplified extension products. We are developing high-throughput capillary electrophoresis (CE) methods for the analysis of TRAP/PCR products. The TRAP assay was conducted on lysates of the human lung cancer cell line A-549 in reactions containing 5-100 cells. TRAP/PCR products were generated using a fluorescent 4,7,2'4'5'7',-hexachloro-6-carboxyfluorescein(HEX)-labeled TS primer and analyzed on the Applied Biosystems Model 310 CE system using POP4 polymer. After analysis with GeneScan and Genotyper software, the total peak areas of the TRAP ladder extension products were computed using Microsoft Excel. Results were compared with unlabeled TRAP/PCR products analyzed on the Bio-Rad BioFocus 3000 CE system using 6% high molecular weight polyvinylpyrrolidone (HMW PVP) polymer and SYBR Green I dye. Both CE systems were able to resolve the TRAP ladder products with high reproducibility and sensitivity (5-15 cells). With the appropriate robotic sample handling system, these CE methods would enable performing the telomerase TRAP assay with increased sensitivity, reproducibility and automation over slab-gel methods.

Base Sequence↗

PubMed2003

Early detection and risk assessment: proceedings and recommendations from the Workshop on Epigenetics in Cancer Prevention.

Recent advances in molecular biology that have provided a greater understanding of multistage carcinogenesis include the use of biomarkers of early detection and risk assessment. Prominent among such biomarkers are epigenetic changes. The field of epigenetics has seen a recent surge of interest among cancer researchers since alterations in DNA methylation have emerged as one of the most consistent molecular alterations in multiple neoplasms. Chromatin condensation, histone deacetylation, and promoter methylation are major steps in the epigenetic regulation of gene expression. Epigenetic changes may occur due to environmental factors, aging, and genomic imprinting. An important distinction between genetic and epigenetic alterations in cancer prevention is that the latter might be more easily reversed using therapeutic interventions. In the workshop the following areas of research were recognized for emphasis in future work: (1) basic epigenetic mechanisms in cancer need further investigation; (2) technology development in the area of epigenetics, such as high-throughput quantitative assays and increased sensitivity/specificity, is essential for the early detection and risk assessment of cancer; (3) the clinical application of epigenetic changes to cancer prevention and risk assessment needs further investigation. Further research will lead to the identification of new targets for cancer prevention.

Aging↗