Genome-Wide Profiling: Gene Expression Profiles
Researchers use gene expression profiling to study the activity of genes in a patient's tumor sample and in surrounding tissue. This approach measures levels of messenger RNA (mRNA), which is a good indicator of the proteins about to be made by the cell.
An individual's messenger RNA is processed and labeled and then applied to a specially designed chip, often referred to as a microarray, which includes complementary sequences for hundreds of thousands of genes. A chip reader measures levels of the expressed genes in the sample.
Other techniques used to assess gene activity monitor levels of genome-wide DNA methylation, which can silence gene activities, or levels of proteins already made in the cell, or the chemical properties of some proteins (e.g., phosphorylation status).