Gene expression is one of the most strongly controlled processes in the body. This method needs to be firmly regulated to ensure that cells produce the accurate amount of proteins when they need them. Any disturbance to this regulation can lead to serious consequences, including cancer. Gene expression is regulated according to the needs of the cells. If the cell is exposed to an environment where particular gene products are needed, the expression of that gene product will be increased. Cells also produce specific gene products in response to external signals or cellular damage.