Biomedical subjects

L A Charette

Publications and source records attributed to L A Charette.

4 recordsLinked to original sources

PubMed2001

Amplification of tissue by construction of tissue microarrays.

Tissue microarrays are a method of relocating tissue from conventional histologic paraffin blocks in a manner that tissue from multiple patients or blocks can be seen on the same slide. This is done by using a needle to biopsy a standard histologic section and placing the core into an array on a recipient paraffin block. This technique allows maximization of tissue resources by analysis of small core biopsies of blocks, rather than complete sections. Using this technology, a carefully planned array can be constructed using cases from pathology tissue block archives, and a 20-year survival analysis can be done on a cohort of 600 or more patients using only a few microliters of antibody in a single experiment. Furthermore, this cohort can be analyzed thousands of times with different reagents as a result of judicious sectioning of the array block. This review describes this process and discusses the issues of representative sampling in heterogeneous lesions, the issue of antigen preservation, and some technical strategies and methods of array construction. In summary, this technique can provide a highly efficient, high-throughput mechanism for evaluation of protein expression in large cohorts. It has the potential for allowing validation of new genes at a speed comparable to the rapid rate of gene discovery afforded by DNA microarrays.

Histological Techniques↗

PubMed2001

Tissue microarray analysis of beta-catenin in colorectal cancer shows nuclear phospho-beta-catenin is associated with a better prognosis.

PURPOSE: Beta-catenin is involved in homotypic cell-cell adhesion and the wnt signaling pathway. Deregulation of beta-catenin levels, caused in part by mutations of the adenomatous polyposis coli gene, is thought to play a role in the development of colorectal and other cancers. To further elucidate their roles, the expression pattern of beta-catenin and phosphospecific beta-catenin was correlated with clinical outcome in a series of patients with colorectal cancer. EXPERIMENTAL DESIGN: Immunohistochemical analysis of a tissue microarray with 650 colorectal cancer specimens was performed to study the expression and subcellular localization of beta-catenin and phosphospecific beta-catenin. These results were correlated with other clinicopathological factors and with overall survival. RESULTS: The majority of cancers retained some degree of beta-catenin membranous staining, whereas cytoplasmic or nuclear expression was seen in 42.5% and 20.4% of specimens, respectively. Phospho-beta-catenin showed nuclear staining in 9.5% of specimens, and there was no apparent membranous or cytoplasmic staining. There was no significant association between beta-catenin or phospho-beta-catenin and grade or stage. However, there was a positive correlation between beta-catenin and phospho-beta-catenin (P = 0.039), with phospho-beta-catenin representing a subset of nuclear beta-catenin. Patients with nuclear expression of beta-catenin did not have an altered survival compared with those that did not (P = 0.5611). Nuclear expression of phospho-beta-catenin, however, was associated with an improved survival (P = 0.0006). In multivariate analysis, only stage and phospho-beta-catenin were independently predictive of overall survival (P < 0.001 and P = 0.0034, respectively). CONCLUSIONS: These findings support a role for beta-catenin overexpression in colorectal tumorigenesis and provide initial evidence that phospho-beta-catenin may be a marker for improved overall survival independent of stage and grade.

Animals↗

PubMed2000

Validation of tissue microarray technology in breast carcinoma.

The recent development of tissue microarray technology has potentiated large-scale retrospective cohort studies using archival formalin-fixed, paraffin-embedded tissues. A major obstacle to broad acceptance of microarrays is that they reduce the amount of tissue analyzed from a whole tissue section to a disk, 0.6 mm in diameter, that may not be representative of the protein expression patterns of the entire tumor. In this study, we examine the number to disks required to adequately represent the expression of three common antigens in invasive breast carcinoma--estrogen receptor, progesterone receptor, and the Her2/neu oncogene--in 38 cases of invasive breast carcinoma. We compared the staining of 2 to 10 microarray disks and the whole tissue sections from which they were derived and determined that analysis of two disks is comparable to analysis of a whole tissue section in more than 95% of cases. To evaluate the potential for using archival tissue in such arrays, we created a breast cancer microarray of 8 to 11 cases from each decade beginning in 1932 to the present day and evaluated the antigenicity of these markers and others. This array demonstrates that many proteins retain their antigenicity for more than 60 years, thus validating their study on archival tissues. We conclude that the tissue microarray technique, with 2-fold redundancy, is a valuable and accurate method for analysis of protein expression in large archival cohorts.

Biomarkers, Tumor↗

PubMedDate not supplied

Tissue microarray: a new technology for amplification of tissue resources.

Tissue microarrays are a method of harvesting small disks of tissue from a range of standard histologic sections and placing them in an array on a recipient paraffin block such that hundreds of cases can be analyzed simultaneously. This technique allows maximization of tissue resources by analysis of small-core biop sies of blocks, rather than complete sections. Using this technology, a carefully planned array can be constructed with cases from pathology tissue block archives, such that a 20-year survival analysis can be performed on a cohort of 600 or more patients by use of only a few microliters of antibody in a single experiment. The reflex criticism of this technique is that the tissue analyzed is not representative, especially in antigens with heterogeneous staining patterns. This review addresses this issue, as well as the issue of antigen preservation or durability, which validates construction of arrays from archives. Strategies and methods of construction and analysis of the arrays are discussed, as well as some other unusual array applications. This technique can provide a highly efficient, high-throughput mechanism for evaluation of protein expression in large cohorts. It has the potential to allow validation of new genes at a speed comparable to the rapid rate of gene discovery afforded by DNA microarrays.

Antigens↗