Starting a tumor off wrong

Aneuploidy is a hallmark of cancer, but the path from mutation to extra chromosomes is unclear. Now, Caldwell et al. help fill this gap, showing that a cancer-causing mutation promotes chromosome doubling by unfastening the mitotic spindle and hindering cell division.

The genome of a cancer cell is a mess, with breaks, rearrangements, and superfluous chromosomes. Many researchers speculate that the genomic instability that leads to aneuploidy and other chromosome chaos starts with tetraploidy, or a duplication of the genome. If so, cancer-spurring mutations should induce tetraploidy early in tumor development. One such mutation, Caldwell et al. suspected, occurs in the mitosis-controlling gene APC. The researchers previously found that APC mutations, which are prevalent in human colorectal tumors, lead to disrupted microtubules...