Showing papers by "Michael D. Radmacher published in 2002"

A paradigm for class prediction using gene expression profiles.

Abstract: We propose a general framework for prediction of predefined tumor classes using gene expression profiles from microarray experiments The framework consists of 1) evaluating the appropriateness of class prediction for the given data set, 2) selecting the prediction method, 3) performing cross-validated class prediction, and 4) assessing the significance of prediction results by permutation testing We describe an application of the prediction paradigm to gene expression profiles from human breast cancers, with specimens classified as positive or negative for BRCA1 mutations and also for BRCA2 mutations In both cases, the accuracy of class prediction was statistically significant when compared to the accuracy of prediction expected by chance The framework proposed here for the application of class prediction is designed to reduce the occurrence of spurious findings, a legitimate concern for high-dimensional microarray data The prediction paradigm will serve as a good framework for comparing different pr

Methods for assessing reproducibility of clustering patterns observed in analyses of microarray data

Abstract: Motivation: Recent technological advances such as cDNA microarray technology have made it possible to simultaneously interrogate thousands of genes in a biological specimen. A cDNA microarray experiment produces a gene expression ‘profile’. Often interest lies in discovering novel subgroupings, or ‘clusters’, of specimens based on their profiles, for example identification of new tumor taxonomies. Cluster analysis techniques such as hierarchical clustering and self-organizing maps have frequently been used for investigating structure in microarray data. However, clustering algorithms always detect clusters, even on random data, and it is easy to misinterpret the results without some objective measure of the reproducibility of the clusters. Results: We present statistical methods for testing for overall clustering of gene expression profiles, and we define easily interpretable measures of cluster-specific reproducibility that facilitate understanding of the clustering structure. We apply these methods to elucidate structure in cDNA microarray gene expression profiles obtained on melanoma tumors and on prostate specimens. Availability: Software to implement these methods is contained in BRB ArrayTools microarray analysis package available from http://linus.nci.nih.gov./BRB-ArrayTools.html.

Design of studies using DNA microarrays.

Abstract: DNA microarrays are assays that simultaneously provide information about expression levels of thousands of genes and are consequently finding wide use in biomedical research In order to control the many sources of variation and the many opportunities for misanalysis, DNA microarray studies require careful planning Different studies have different objectives, and important aspects of design and analysis strategy differ for different types of studies We review several types of objectives of studies using DNA microarrays and address issues such as selection of samples, levels of replication needed, allocation of samples to dyes and arrays, sample size considerations, and analysis strategies