This page has information about cancer cells and how they are different from normal body cells. You can read about
Normal body cells have a number of important features. They can
- Reproduce themselves only when and where they are needed
- Stick together in the right place in the body
- Self destruct if they are damaged or too old
- Become specialised (mature)
Cancer cells are different to normal cells in various ways.
Unlike normal cells, cancer cells don't stop growing and dividing when there are enough of them. So the cells keep doubling, forming a lump (tumour) that grows in size.
Eventually a tumour forms that is made up of billions of copies of the original cancerous cell.
Cancers of blood cells (leukaemias) don't form tumours but they make many abnormal blood cells build up in the blood.
Cells send chemical signals to each other all the time. Normal cells obey signals that tell them when they have reached their limit and will cause damage if they grow any further. But something in cancer cells overrides the normal signalling system.
The video shows how cancer cells send messages that trigger other cells to grow and divide.
View a transcript of the video about when cells cause cancer by giving the wrong messages.
Cancer cells can lose the molecules on their surface that keep normal cells in the right place. So they can become detached from their neighbours.
This helps to explain how cancer cells can spread to other parts of the body.
You can read about how cancer can spread.
Unlike healthy cells, cancer cells don't carry on maturing or become specialised once they have been made. Cells usually mature so that they are able to carry out their function in the body. The process of maturing is called differentiation. In a cancer, the cells often reproduce very quickly and don't have a chance to mature.
Because the cells are not mature, they are not able to work properly. And because they are dividing more quickly than usual, there's a higher chance that they will pick up more mistakes in their genes. This can make them become even more immature, so that they divide and grow even more quickly and haphazardly.
Normal cells can repair themselves if their genes become damaged. This is known as DNA repair. If the damage is too bad, they will self destruct. This is called apoptosis.
In cancer cells, the molecules that decide whether a cell should repair itself are faulty. For example, a protein called p53 normally checks to see if the genes can be repaired or if the cell should die. But many cancers have a faulty version of p53, so they don't repair themselves properly.
If cells don't repair damage to their genes properly, this leads to more problems. New gene faults, or mutations, can make the cancer cells grow faster, spread to other parts of the body, or become resistant to treatment.
Cancer cells can override the signals that tell them to self destruct. So they don't undergo apoptosis when they should. Scientists call this making themselves immortal.
Under a microscope cancer cells may look very different from normal cells. The cells are often very different sizes and some may be larger than normal while others are smaller. Cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.