termsTerm
Gene expression
aka expression, expressed, expresses, expression level, expression levels, highly expressed, low expression, high expression
How much a gene is switched on, and therefore how much of its protein a cell makes. Cancer cells often express the wrong genes at the wrong levels.
Expression is controlled by switches in the DNA, by chemical marks on the DNA and its packaging (epigenetics), and by signals from outside the cell. Saying a tumour 'expresses HER2' or 'is PD-L1 positive' means the protein is present at a detectable level, usually measured by immunohistochemistry or RNA sequencing. Expression matters for treatment because antibody drugs and ADCs need enough target protein on the cell surface to bind, and because expression signatures (Oncotype DX, PAM50) predict how a tumour will behave.
Category
Biology basics