Spindle Assembly Checkpoint
The spindle assembly checkpoint (SAC) controls the progression through mitosis, ensuring that anaphase does not occur until all chromosomes are properly attached to microtubules originating from two spindle poles.
In 1902, Theodor Boveri proposed that cancers could derive from “a certain abnormal chromosome constitution that in some circumstances can be generated by multipolar mitoses.” Since little was known about the cell cycle and the spindle assembly checkpoint (SAC) had not been discovered, he did not know he was implying that cancer cells have a weakened SAC. While studying the effects of radiation on mitosis in 1970, Zirkle was one of the first to notice that even a small aberration in the alignment of chromosomes at the metaphase plate induced a delay in anaphase. With the discovery of microtubule agents including paclitaxel(1967) and nocodazole (1976), researchers were equipped with the tools needed to induce this delay and...