How cancer starts: how a normal cell turns into cancer
Oncogenes and tumour suppressor genes: the accelerator and the brake of a cell
Every cancer starts with genes that were working for you all along. Some tell a cell to copy, others tell it to stop. What happens when one of them gets a single wrong letter?
-
1
How does a cell obey the message "copy now"? Some of its genes make the parts that carry the message inside the cell. Together they work like the accelerator pedal of a car: the message presses it, and the cell copies.
-
2
When the message stops, the pedal comes back up, and the copying stops too.
-
3
Other genes work like brakes. They stop the cell from copying, for example while it repairs damaged DNA. A normal cell needs both pedals working.
-
4
A mutation can jam an accelerator gene so it stays pressed. Then the cell copies even when no message comes. A jammed accelerator gene is called an oncogene.
-
5
A mutation can also break a brake gene. Then nothing stops the cell when it should stop. Brake genes are called tumour suppressor genes, because when they work, they hold tumours back.
-
6
In 1976, Michael Bishop and Harold Varmus studied a virus that gives cancer to chickens. Its cancer gene was not the virus's own. It was a normal chicken gene that the virus had picked up. They won the Nobel Prize for it in 1989.
-
7
So most cancer genes are not invaders. They are our own accelerators and brakes, broken by a mutation.
-
8
In Rono's pigment cell, fifty years ago, the mutation landed in an accelerator gene called BRAF. The pedal jammed, and the cell copied with no message, again and again.
-
9
That sounds like cancer. Yet Rono's cells did not grow into a tumour. They made a small mole, and then they stopped.
-
Quick check
Blocking the message.
Show the answer
No. A jammed accelerator stays pressed with no message at all, so blocking the message does not stop that cell.
-
Go further
More about accelerator and brake genes.