Cancer cells use loopy genes for speedy growth

When c-Myc goes wrong, cells grow too fast and we may get tumours. New research shows that c-Myc makes loops in growth genes. These loops change cell structures so cells can grow faster.

Scientist Rachel B___ and her colleagues at the Karolinska Institute in Sweden have found a new kind of loops in important genes. This could explain how some cancer cells can grow faster than normal.

Rachel's team are studying c-Myc, a master regulator of cell growth which often gets out of control and causes cancer. In the US, for example, one death out of every seven is due to a problem with c-Myc. Understanding how c-Myc works is an important step towards developing new, better cancer drugs.

Protein factories

c-Myc is important because it tells cells when it's time to build more protein-making machinery. Just as a company that wants to increase its productivity needs to build new factories, growing cells need to build protein "factories". These factories contain hundreds of copies of a few simple genes, which are the plans for the protein making machinery. c-Myc directs resources to the factories until they consume up to half the cell's budget.

immunofluorescence labelled cells showing nucleoli

The protein factories of an active cell are big enough to see with a microscope. When pathologists look at samples from patients, one thing they look for is changes in the appearance of these spots. Cancerous samples often have enlarged spots or more of them than usual, but we don't know precisely why.

Loops

Rachel's colleagues were surprised to see c-Myc attached to the beginning and the end of the genes in the protein factories. Normally, regulators are only found at the start of genes, explains one of the scientists, because that's where the switches are that control gene expression.

They realized that c-Myc makes the genes bend round in a complete circle, so that the end is next to the beginning. This means that when the cell machinery moves along the gene making components, it can continue round the loop to the beginning and make a second component straight away. So more components are produced faster and the cell can grow rapidly.

These loops are repeated over the hundreds of copies of identical genes. This creates new structures in the cell that are big enough to see with a microscope. That's why we see changes in the protein factory spots when we look at cancer cells.

Improved cancer drugs

Scientists are working on drugs that block c-Myc so that cancer cells can't grow. If a company director started ordering the building of new factories when none were needed, the company would eventually go bankrupt. So c-Myc, the rogue director, has to be stopped before that can happen. If scientists can understand exactly how c-Myc works, it can be eliminated without harming healthy cells in the rest of the body.


© RGB Nov 2008