Abstract
Chromosomal instability is the hallmark of many cancers. In his Perspective, Pellman discusses new findings revealing that APC, a protein known to be mutated in colon cancer, is crucial for the attachment of chromosomes to the microtubules of the mitotic spindle. He explains how aberrant forms of APC could lead to missegregation of chromosomes during cell division, in turn leading to chromosomal instability.