Microarrays and molecular markers for tumor classification

Abstract

Human cancers have traditionally been classified according to their tissue of origin, histological characteristics and, to some extent, molecular markers. Clinical studies have associated different tumor classes with differences in prognosis and in response to therapy. Measurement of the expression of thousands of genes in hundreds of cancer specimens has begun to reveal novel molecularly defined subclasses of tumor; some of these classes appear to predict clinical behavior, while others may define tumor types that are ripe for directed development of therapeutics. Unfortunately, at present, differences between studies of similar tumor types can be as striking as their similarities.

Figure 1

Gene-expression patterns of 85 different breast cancer specimens for the 456-gene 'intrinsic gene list' identified by Sorlie et al. [17], depicted as a pseudo-color hierarchical cluster-diagram. Highlighted areas depict sets of genes whose expression has been inferred to distinguish classes of breast cancer as determined by cluster analysis. The luminal class and erbb2 class are candidates for treatment with tamoxifen and herceptin, respectively. Other identified classes may be useful for the identification of novel markers of prognosis and for the identification of targets for rational drug design. Figure adapted from [17].