Tony Hunter made the seminal discovery, more than four decades ago, that the addition and subtraction of phosphate molecules to proteins on tyrosine, one of the 20 amino acids, allows cells to control when key proteins are on standby and when they are active. He went on to show that, in cancers, growth was switched to an always-on mode by the malfunctions of these phosphates. Since then, his lab has led the field in understanding how chemical additions to proteins control the cell cycle and growth. Hunter uses cutting-edge molecular, genetic and cell biology techniques to probe how these programs interact with each other, what effect they have on cells and how cancers disrupt them to encourage uninhibited growth.