Gene expression profiling in cancer

Cancer is a disease characterized by uncontrolled cell growth and proliferation. For cancer to develop, genes regulating cell growth and differentiation must be altered; these mutations are then maintained through subsequent cell divisions and are thus present in all cancerous cells. Gene expression profiling is a technique used in molecular biology to query the expression of thousands of genes simultaneously. In the context of cancer, gene expression profiling has been used to more accurately classify tumors. The information derived from gene expression profiling often helps in predicting the patient’s clinical outcome.

Oncogenesis is the process by which normal cells acquire the properties of cancer cells leading to the formation of a cancer or tumor (see: tumorigenesis). It is characterized by a molecular reprogramming of a cell to undergo uninhibited cell division, allowing the formation of a malignant mass. The cells forming this mass undergo natural selection: as cells acquire mutations that enhance their survivability or reproductive capacity, they dominate the growing tumor as other cells are out-competed (see: somatic evolution in cancer). Because of these selective properties, the majority of cells within a tumor will share a common profile of gene expression.

Gene expression profiling is a technique used in molecular biology to query the expression of thousands of genes simultaneously. While almost all cells in an organism contain the entire genome of the organism, only a small subset of those genes is expressed as messenger RNA (mRNA) at any given time, and their relative expression can be evaluated. Techniques include DNA microarray technology or sequenced-based techniques such as serial analysis of gene expression (SAGE).

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