Gordon was fascinated by how and when cells choose to divide. A process that is necessary for children to grow and for adults to repair wounds. But mistakes during this process can also lead to cancer. Gordon looked at the control mechanisms in place in our cells to stop them dividing and wanted to know why these controls are lost in cancer cells. His work led to the development of a group of drugs called CDK4 inhibitors, which are now used to treat cancer patients. These drugs work by regaining control of how and when cancer cells divide, blocking them from making any more divisions. In some patients, this can stop their tumour from growing.