It may be small and inconspicuous, but the structure called the centrosome plays a big role in the cell. One key duty: helping to organize the mitotic spindle—the collection of protein filaments that pull the duplicated chromosomes apart during cell division, thereby ensuring that the two daughter cells each get a complete set. Without the centrosome, normal division of human cells could not occur. But accumulating evidence hints that this structure has a dark side as well. When the centrosome malfunctions, cancer may result.

Researchers have known for decades that cancer cells are rife with chromosomal abnormalities. Some cells lack one or more chromosomes, for example, while having extra copies of others.“Virtually every cancer cell has an abnormal chromosome complement, whereas virtually every normal cell has the [normal] diploid number,” says cancer researcher Bert Vogelstein of Johns Hopkins University School of Medicine. The conventional wisdom has been that this aneuploidy, as it's called, is a late event in cancer development—the result of all the other disruptions in cancer cells. But now,“more and more it's coming out that [aneuploidy] is an early change and may be driving malignancy,” says Vogelstein, whose own work has been pointing in that direction.