A gene signature or gene expression signature is a single or combined group of genes in a cell with a uniquely characteristic pattern of gene expression[1] that occurs as a result of an altered or unaltered biological process or pathogenic medical condition.[2] This is not to be confused with the concept of gene expression profiling. Activating pathways in a regular physiological process or a physiological response to a stimulus results in a cascade of signal transduction and interactions that elicit altered levels of gene expression, which is classified as the gene signature of that physiological process or response.[3] The clinical applications of gene signatures breakdown into prognostic, diagnostic[4][5] and predictive signatures. The phenotypes that may theoretically be defined by a gene expression signature range from those that predict the survival or prognosis of an individual with a disease, those that are used to differentiate between different subtypes of a disease, to those that predict activation of a particular pathway. Ideally, gene signatures can be used to select a group of patients[6] for whom a particular treatment will be effective.[7][8]
^Chibon F (May 2013). "Cancer gene expression signatures - the rise and fall?". European Journal of Cancer. 49 (8): 2000–9. doi:10.1016/j.ejca.2013.02.021. PMID23498875.