Contact inhibition

In cell biology, contact inhibition is the avoidance behavior exhibited by fibroblast-like cells when in contact with one another. In most cases, when two cells contact each other, they attempt to alter their locomotion in a different direction to avoid future collision. When collision is unavoidable, a different phenomenon occurs whereby growth of the cells of the culture itself eventually stops.

Mechanism

Contact inhibition is a regulatory mechanism that functions to keep cells growing into a layer one cell thick (a monolayer). If a cell has plenty of available substrate space, it replicates rapidly and moves freely. This process continues until the cells occupy the entire substratum. At this point, normal cells will stop replicating.

Role in cancer

Cancerous cells typically lose this property and thus grow in an uncontrolled manner even when in contact with neighbouring cells. They aren't motivated to change direction upon contact, so they pile up and grow over each other. Cells of naked mole rats, a species in which cancer has never been observed, show hypersensitivity to contact inhibition.

Cell motility

In most cases, when two cells collide they attempt to move in a different direction to avoid future collisions. As replication increases the amount of cells, the number of directions those cells can move without touching another is decreased. As the two cells come into contact, their locomotive process is paralyzed. Cells will also attempt to move away from another cell because they stick better to the area around them, a structure called the substratum, than on other cells. When the two cells colliding are different types of cells, one or both may respond to the collision.

Some immortalised cell lines, despite being able to proliferate indefinitely, still experience contact inhibition, though generally to a lesser extent than normal cell lines.