Can excess chromosomes drive tumor growth?

Some cancers are addicted to having extra chromosomes, a study in mice suggests. Cells usually have only two copies of each chromosome, one inherited from mom and one from dad, but about 90 percent of cancer cells have extra chromosomes, a condition called aneuploidy.

Certain types of cancer cells often carry a third copy of a particular chromosome or part of a chromosome, for example, more than half of colorectal tumors have an excess chromosome 13 and more than 40% have an extra chromosome 7 or the long arm of chromosome 8. Storing spare copies of chromosomes has been associated with poorer patient outcomes compared with patients whose cancers have the usual two copies.

It turns out that those extra doses of genetic material are necessary for cancer cells to keep growing—in other words, cancerous tumors are addicted to extra chromosomes. The idea of ​​addicted cancer cells isn’t entirely new—scientists have known for decades that cancer cells can become addicted to altered versions of certain genes, meaning those genes are necessary for the cells’ continued cancerous growth.

The idea that cancer cells can be addicted to genes forms the basis of many targeted cancer therapies, which interfere with the action of genes that drive cancer. Chromosomes, however, contain thousands of genes, so determining which of those genes or combination of genes is the source of addiction is much more complicated.

But finding out which genes make cancer cells addicted is necessary if researchers are ever going to develop treatments to nullify the effect of the extra chromosomes.

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